Author Topic: Another Comber / Coomber build  (Read 21011 times)

Offline arnoldb

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Another Comber / Coomber build
« on: October 23, 2011, 06:56:08 PM »
I mentioned in another build thread that I'll be starting another "Elmer" build.  Besides all the Elmer engines that I still want to build, two needs immediate attention.

The Kimble engine has been nagging at me for a long time; it WANTS to be built, and I will build that one soon, but once again it's on the back-burner...

Last year at some point, I was in three minds about which engine to build next for my own collection, and after I showed my sister the pictures, she chose the Elmer #46, which I then built.  When I asked her what she wanted for her birthday a couple of months ago, she said I owed her a #46  :lol:.  Mine is a good runner, and I can just give her this engine, but it does not quite run on breath power, so I thought it better to make her a new one, that will easily run on breath power and with a bit of added personalization.  I hope this new build will do the job  :)

So the rules are "simple" - build a personalized, breath powered, Coomber   :D - I think I'm a sucker for punishment   :whip:  :lol:

On to the nitty gritty then...

I'll be building mostly to Elmer's plans except for:
a) Increased cylinder bore size. An increased piston diameter will reduce the pressure needed to power through a stroke.  Increasing the bore diameter means increasing the cylinder block dimensions; that means recalculating the bearing block spacings.  I'll do that as I go.
b) A flywheel that is fairly light, yet with good rim mass.  Light to keep bearing friction down, and outside rim mass will help it keep up rotational momentum.
c) Minimise friction...  My existing Comber has quite a bit of friction in the bearings, and some "slapping" on the cam ring.  For this build, I'll add a cast-iron insert on the main/port bearing; the brass running in CI compared to brass in aluminium should be an improvement.  For the "slapping", well, I'll just to add a bit more clearance to the forks, make the rollers smoother, and make the cam dead-on smooth.  I could add a roller bearing on the non-port bearing block, but maybe a CI insert will do that job as well.
d) Metric - all bits are converted to metric; I don't mind working in inches and fractions and thous, but pretty much everything I have access to is in metric, so I machine in metric.

I started off the cylinder block with a bit of 25 x 25 x 40mm brass stock flycut down to get it square:

That's the beginnings of the cylinder block.

A bit of marking out - to find the center on both of the long-end faces: with two reference sides marked


In the 4-jaw chuck on the lathe - finding center with a dead center... I REALLY need to make a proper pump center   :doh:


That was then center drilled, reversed in the chuck, and the other end's center found the same way, and drilled 7mm to fit a bit of 7mm round brass I have in stock:


That 7mm brass bar was a fairly tight fit, but as I wanted to silver solder it in there, it needed a bit of clearance for the solder to wick in, so I filed the end of the bar down a bit in the lathe to make it about 0.1mm under-sized, and then knurled the end:


The knurling raises the effective thickness of the brass bar, making it need a good whack to go into the hole in the cylinder block, retaining it fairly straight and square in the hole.  It also leaves grooves for the solder to flow (wick) into the joint.  I coated the hole inside  the cylinder and the knurled bit with silver solder flux paste before whacking together and added a ring of silver solder and additional flux.  A bit of "colouring in" with a graphite pencil around that lot followed; the penciled area will prevent flux and silver solder sticking:


Then I showed that lot my Sievert torch - LOTS of heat concentrated on the bottom of the cylinder block to make it glow dull red, took a bit longer than I'm used to; about 50 seconds for the flux to flow (it goes from looking like bubbly sherbet, to white crystals, then like burnt and black caramel, then suddenly like water all over the place) and 10 more for the silver solder to wick in properly, but it came together:

Heat at the bottom of the cylinder, as that draws (wicks) the solder INTO the joint; if you just heat the outside and top, the solder will melt, but not penetrate into the joint.

After a pickle in citric acid for the part while I had a bite to eat (~ 30 minutes) I chucked up the 7mm end in the collet chuck on the lathe, and with the tailstock support in the previously-drilled center, I turned down the end to 12mm with a 14mm shoulder:


Flipped in the chuck, and clamping down on the 12mm bit, I VERY carefully turned down the 7mm round bit to 6mm.  It has a fair bit of overhang, so a sharp HSS toolbit is the order of the day:


Then I set up that lot in the mill, using a dial test indicator (DTI) to check for squareness.  Obviously, the mill needs to be in near-perfect tram for this and the following machining steps:


Then I drilled and bored out the cylinder with a couple of successive drill sizes -3mm, 7mm, 13mm and then the boring head to take it up to 16mm.  A blurry action photo; as the boring head was running nicely balanced, this shot is at about 800 RPM, and very fuzzy as I was paying more attention to the feed than the camera   ::):


I checked for the final 16mm bore size with a telescoping gauge:

Well, not entirely true...   :med: - the sizes measured are all OK, but I know that that digi caliper of mine is inclined to measure 0.05mm under size... - so that hole is actually 15.95mm   :smart:

I ended up with this lot for today's work:


If you click on the last photo and have look down the left side of the non-perfect bore, you'll see the slight oval where the shaft joined the body; at least the silver solder job went exactly as planned  :)

I wanted to be a bit further along today, but a neighbour  popped in with a a gift and his young 'uns in tow.  The gift is a very drinkable bottle of Scotch in return for fixing his wife's treadmill last weekend, and the young 'uns wanted to see some of my engines running.  It's just as much fun as machining - if not more so - showing off my simple engines to a four and six year old...  They seem to like the Elbow engine , the Comber, and of course the half-finished Cracker...  pft pft pft  ;D

Kind regards, Arnold

Offline sbwhart

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Re: Another Comber / Coomber build
« Reply #1 on: October 24, 2011, 01:38:23 AM »
Great start Arnold well shown,  :thumbup: I'll be quetly following this one.

Stew
A little bit of clearance never got in the road
 :wave:

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Offline saw

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Re: Another Comber / Coomber build
« Reply #2 on: October 24, 2011, 04:29:09 AM »
This project seems to be intressting, good start by the way  :clap: :clap:
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Offline arnoldb

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Re: Another Comber / Coomber build
« Reply #3 on: October 25, 2011, 02:29:07 PM »
Stew, Benni, thanks gents  :beer:

Had an hour and a half in the shop after work today  :)

Layed out for the ports on the cylinder block:


As I made the cylinder dimensions bigger than on the plan, I left enough meat to drill the passages square rather than at the angles as on the original plans. I also increased the passage bore to 2mm from the original 1.6mm.  Drilling the first passage:


Flipped the block and drilled the second passage, then milled out clearance 2mm deep into the cylinder bore:


While I had the milling cutter set up, I milled the port slots on the main axle as well:


The connection ports followed; I used a "wiggle wire" to feel for break-through into the steam passage:


Cleaned things up a bit and stopped for today.  Time really flies when one is having fun! :


Regards, Arnold

Offline saw

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Re: Another Comber / Coomber build
« Reply #4 on: October 25, 2011, 02:46:52 PM »
Arnold, I have been looking and looking, smoking, drinking coffie, looking, smoking again, but I cant understand how this engine is going to work. Am I stupid or..  :doh:
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Offline arnoldb

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Re: Another Comber / Coomber build
« Reply #5 on: October 25, 2011, 03:24:47 PM »
Hi Benni

At first it does not make sense; don't worry  :thumbup:.  If you have a look here it might become more obvious.
The animation does not show how the porting to the cylinder works though.  In the last photo of my cylinder block, the two holes at the end of the axle must still be blocked off. This is a cross-section of what the cylinder & steam passages looks like:


The slots that are milled in the port faces connect up to holes in the main bearing as the engine is turning - providing the steam / air path.  This is what the main bearing looks like to allow for steam and exhaust connection:


Hope this helps  :D

 :beer:, Arnold

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Re: Another Comber / Coomber build
« Reply #6 on: October 25, 2011, 03:45:54 PM »
Off to your usual great start Arnold!  :clap: :clap:

I hadn't the faintest idea, just what a Coomber engine was/ is.......  :scratch:

Google Images came up trumps!  :thumbup:

Good luck! Watching quietly.  :wave:

David D
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Still drilling holes... Sometimes, in the right place!

Still modifying bits of metal... Occasionally, making an improvement!

Offline saw

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Re: Another Comber / Coomber build
« Reply #7 on: October 25, 2011, 03:52:36 PM »
Thanks Arnold but I am not shure.  :doh:
I am awere that there is a lot off diffrent steam engine, but I don't think that I ever have seen this kind of engine before.
If I understand, well not right now, I will go back to my own engine for some adjustment, and thinking of you're engine, then maybe there will go up a candle  :smart:
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Offline arnoldb

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Re: Another Comber / Coomber build
« Reply #8 on: October 29, 2011, 02:29:26 PM »
Cheers David  :beer:

Benni, don't worry  :thumbup: ; this type of engine is a bit less known, as I think it is inefficient and as a result was unsuccessful in industry.  I like these weird engine designs, that's why I build them...  The next engine I have in line to build is the "Kimble" engine, and I'm busy putting my own set of plans together for another weird engine that I have not seen any models or pictures of real ones of...  If you have any specific questions on what you don't understand on this engine, or any detail you want more pictures of, please ask  :thumbup: - I'm happy to try and help.

Today's bit; I wanted to have more done by now, but time has a way of running out...

I started on the cylinder heads; some 25mm square Aluminium bar clocked up relatively on center in the 4-jaw chuck:

Remember, when centering up square stock, make sure you have enough travel on the dial indicator to clear the edges, and manually push in the tumbler when rotating the stock  :med:

Faced off - I like it when I get a near-mirror finish like this:


Then some more taken off to leave a 0.5mm thick step.

The step is a nice push fit in the cylinder bore to keep the head concentric, and one needs a nice sharp point on the toolbit to prevent rounding in the corner, otherwise the head will not sit flat against the cylinder face.

The workpiece was then center drilled with a 1mm center drill, and drilled about 8mm deep with a sharp 2mm drill that I know does not drill over size.  This hole should actually have been reamed to about 2.02mm, but I don't have a 2mm reamer, so I'll lap the hole out later.  I just made a point of retracting the drill bit slowly from the hole; a sharp drill can leave a fairly good finish in the hole if this is done.

Then I used the parting tool (after a quick hone on it) to remove a fair bit of material on the other side:

Just a couple of straight-in parting cuts to the same depth; have I mentioned how much fun parting plunge cuts can be through the square section?  ::)

The other cylinder head followed, using the same method.  The one on the left shows the face that points into the cylinder, and the gory one on the right what it looked like after the parting off on the other side.  Not quite as bad as it looks; it's got some cutting oil stains on it as well:


To clean up the messy face, I just chucked up a bit of 2mm rod in the collet chuck, leaving a short length protruding to engage the holes in the cylinder heads, and took a bit of carton and stuck it over that:


Then I used the revolving center in the tailstock to tightly press the cylinder head to the front of the chuck, and with light cuts turned the face and boss to final sizes:


To clean up the face of the boss was another matter; one cannot get close enough without damaging the center; something I REALLY do not want to do.  So I moved away the tailstock, and with a narrow strip of emery pressed against the face with the forefinger of my right hand, I started the lathe; the pressure keeps the cylinder head engaged against the collet chuck, and because the contact area against the paper is larger than that of the emery on the face, there's sufficient drive to finish it.  NOT the best way to do things; it would be better to stick the cylinder head to a mandrel (with superglue or double sided tape) or clock it up in the 4-jaw against a backstop to finish machining.

A piece of 2mm rod passes easily yet closely through both holes with very little binding.  A Little lapping will sort the binding out in just minutes:


Next I set up to drill for the cylinder mounting screws.  I marked one side of the cylinder out just for visual reference, then found the left back edge of the cylinder block, dialled in the location of the first hole, and set the X and Y dials to 0.  A quick check locating the other hole locations on the handwheels turned out well:


Then I clamped one cylinder head to the block and drilled the four 1.6mm holes needed to tap for M2.

I really need to invest in some spotting drills... I'm still using a center drill to spot the holes before drilling.
Flipped the block, and did the same on the other side using the other cylinder head clamped down.

On to tapping the holes in the block.  For tapping M2, I use the cruddy-looking tapping handle and tapping guide shown:

I'm a big old wimp - When I get around to tapping holes in a cylinder block, I religiously follow through the holes with each tap in the set; cleaning the tap after each hole.  It may take much longer, but after having put a lot of time, material and effort into the cylinder block, the last thing I want is to have it ruined by breaking a tap in it!

One thing I have found to be really convenient is to use a countersink to lightly countersink around each hole before tapping.  I just do it by twirling the countersink between fingers until there's a spot just slightly larger in diameter than the thread size:

This serves multiple purposes.  On a cylinder face, it prevents tapping from raising a burr above the level of the face, keeping it nice and flat.  It also seems to help to make the tap start easier into the hole.  And last, the tangent surface of the countersink reflects some light when looking through the hole of the tapping guide, making it easier to locate over the hole.

For this engine, I'm going to use 2mm countersink screws to retain the cylinder heads.  I just clamped each cylinder head in a loose vise, and on the drill press drilled the holes out to 2mm clearance and then countersunk them, using the drill press depth stop to limit depth:


I also milled each cylinder head down to final size on the square ends, and ended up with this:


Next I need to start laying out the base.  As I'd increased the cylinder dimensions, the bearing posts need to be relocated from the original plans.  To get a feel of what things would look like, I compared the cylinder block to my existing Coomber's:


I think it will look OK - just a bit chunky maybe, because it's fatter.  But I didn't expect one thing...   :bang: :bang:  The new cylinder was meant to be the same length as the original with the same stroke...  It's about 3mm longer! - had a look at the plans, and the fuzzy dimension on the printout says it all...  The cylinder block was supposed to be 13/16" long, but on the printout it looks like 15/16" and that's what I made it, so it's 1/8" too long...  That means I'll have to increase the size of the cam - the original is already very close in clearance and there's no way I can keep to the original cam size now.  Seeing as I have 1/8" more stroke available, I might as well adjust the cam for that as well.
I guess my sister's going to get a bigger engine than I thought  :lol:

Regards, Arnold

Offline saw

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Re: Another Comber / Coomber build
« Reply #9 on: October 29, 2011, 06:17:20 PM »
You are working nicley, like a painter  :bow: :bow:
« Last Edit: October 30, 2011, 04:01:42 AM by saw »
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Offline madjackghengis

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Re: Another Comber / Coomber build
« Reply #10 on: October 29, 2011, 07:40:49 PM »
I've got to say, that's the first time I ever saw an engine of that sort.  That should make a very interesting engine when you've got it running.  I'm really looking forward to seeing it running. :jaw:  Cheers, mad jack

Offline arnoldb

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Re: Another Comber / Coomber build
« Reply #11 on: October 30, 2011, 01:39:57 PM »
Thank you Benni  :beer:

 :beer: Thanks Jack - they are interesting.  My first one runs nicely - video - ; I hope this one will go on breath power.

This morning I re-calculated the dimensions for the cam ring to use the new piston stroke, and added a bit of extra clearance to the connecting rod length in the process.  The original dimensions would not have enough clearance on the center height of the bearings, so I had to compensate for that as well...  So, one wrong-size cylinder and the original changes to the base are still needed as expected, but the bearing columns had to get the once-over as well.  This lot took a surprising amount of time to re-design so that things would (hopefully!) work out.

A fairly quick C-o-C later to put all the new dimensions on one bit of paper:

 :lol: It's not pretty, but it makes sense to me...

A rummage around, and some bandsawing, and I had bits of stock to start with:


After some work on the mill with the fly-cutter and end mills, I had those to size and ready for lay-out.  The bearing blocks were super glued together early on to allow me to machine them as a pair to maintain a semblance of accuracy:


I nearly stopped for the day at that point, but decided to drill and bore the bearing blocks to 16mm to accept bushes:


Then I did stop for the day:


Not a lot of progress, but things might pick up in the evenings  :)

:beer: , Arnold

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Re: Another Comber / Coomber build
« Reply #12 on: October 30, 2011, 05:55:41 PM »
I see your making great progress Arnold  :clap: :clap: :clap: :clap:

Lookin good  :dremel:


Rob  :D

Offline millwright

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Re: Another Comber / Coomber build
« Reply #13 on: October 30, 2011, 06:24:52 PM »
Had to read up on it and check the drawings, a complete new one on me. Loking forward to seeing it run, wont have too long to wait i suspect. nice clear pics as well Arnold.  :clap:
John

Offline doubleboost

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Re: Another Comber / Coomber build
« Reply #14 on: October 30, 2011, 06:30:23 PM »
Some really nice work going on hear  :thumbup: :thumbup: :thumbup:
John

Offline madjackghengis

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Re: Another Comber / Coomber build
« Reply #15 on: October 31, 2011, 12:28:01 PM »
Well Arnold, it looks like you're making some pretty good progress there.  Thanks for the video of your running engine, it's much better than the other video showing the basic mechanics of it.  Thanks for the connections to Elmer's engines as well, I expect to find some interesting projects for the future from among them.  I like the fact you are using plans, but not tied to them, and willing to modify and adapt, it makes each engine unique unto its self that way as I see it.  This engine is kind of like a wobbler that the cylinder travels in a complete circle to complete its porting of steam and it makes for a very interesting looking engine when running.  Very nicely done she should be a real beauty when she's running. :jaw: :beer:  Cheers, mad jack

Offline arnoldb

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Re: Another Comber / Coomber build
« Reply #16 on: November 01, 2011, 02:53:56 PM »
Rob, both Johns and Jack - Thanks Gents  :beer:

Jack, Elmer's engines are well suited for beginners, but I know of quite a couple of experienced machinists who get just as much fun from building them.  About half of the engines I've built so far are Elmers; on most of them I worked to the plans, but now that I've started to grasp how things go together on paper and what to look out for when making my own changes, I'm getting bolder about doing that.  The basic Elmer engines are very simple in appearance and does lean themselves to a bit of change and "customisation".

Stole two hours in the shop after work today   :dremel:

I used an old "incorrectly made" needle valve stem to find the location for the first mounting hole to drill in the columns and zeroed the X and Y dials on it:


Then I started drilling the holes, just by feeding in the coordinates on the mill.  The third hole was a bit of a disaster; the 1mm center drill I was using to spot the hole location before drilling snapped it's tip in the hole:


I used the sharp side edge of a pair of needle-nosed pliers to grab on to it and gently tried to reverse it out of the hole.  A bit more snapped off, and after poking around in the hole with a sharp scriber I could feel there was a bit left.  Out of sheer desperation, I plunged the snapped center drill in rapidly, hoping that it would deflect and then pick up and extract the bit of HSS trapped in the hole together with the swarf:


 :ddb: It worked; after that plunge, scratching around in the hole with the scriber I couldn't feel any hard bits in there, so I drilled the hole to size without any further fiasco, and the last hole went well as well:


Tapping the holes went well; in the background you can see the bottle with the purple-coloured methylated spirits I use for tapping aluminium:


I wasn't in the mood to set up the rotary table to round over the tops of the bearing columns, so I used a 16mm drill bit's shank to support the columns and started milling away facets - a quick job, but just make sure there's no swarf trapped below the drill bit (or supporting rod):


This is what the columns looked like fresh off the mill; the glue holding them together came loose in the process, but fortunately they need not be held together any more at this point:


Getting rid of the facets is easy - a couple of light strokes (literally about 10) with a sharp file around the outside, and you can see the difference:


A quick rub over emery, and that's where I stopped for the day; there's still some tool marks left, but I'll remove those later, as I need to do a bit more work on the one column and also press in the bearings once made:


 :beer:, Arnold

Offline saw

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Re: Another Comber / Coomber build
« Reply #17 on: November 01, 2011, 03:35:40 PM »
Arnold, you are stiil going strong, nice progress  :clap: :clap:
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Offline Stilldrillin

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Re: Another Comber / Coomber build
« Reply #18 on: November 01, 2011, 04:51:26 PM »
Well saved, and nice end result Arnold!  :clap: :clap:

After just such a snapping, last year. I stopped using centre drills.

I always use a 3mm spotting drill, in the lathe and mill.......  :thumbup:   

Not one hiccup since!   :D       

 http://www.ebay.co.uk/itm/3MM-NC-SPOTTING-DRILL-90-DEGREE-COBALT-SPOT-DRILL-NEW-/140596402738?pt=UK_Home_Garden_PowerTools_SM&hash=item20bc32da32

David D
David.

Still drilling holes... Sometimes, in the right place!

Still modifying bits of metal... Occasionally, making an improvement!

Offline Henning

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Re: Another Comber / Coomber build
« Reply #19 on: November 01, 2011, 04:59:50 PM »
Great work!

Nice touch on using the drill bit as an axis to mill the facets to get the rounding. I have saved that in the murky depths of my twisted mind until i get a mill.
Henning

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Offline saw

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Re: Another Comber / Coomber build
« Reply #20 on: November 01, 2011, 05:11:41 PM »
 :offtopic:  I have to ask:
Quote
I always use a 3mm spotting drill, in the lathe and mill
I have never heard of it, but I have some big problem using centerdrill on my mill.  :Doh:
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Offline sbwhart

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Re: Another Comber / Coomber build
« Reply #21 on: November 01, 2011, 05:20:54 PM »
Great work Arnold photos at talk through are first class

 :clap: :clap: :clap: :clap: :clap:

Stew
A little bit of clearance never got in the road
 :wave:

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Offline Stilldrillin

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Re: Another Comber / Coomber build
« Reply #22 on: November 01, 2011, 06:51:46 PM »
:offtopic:  I have to ask:
Quote
I always use a 3mm spotting drill, in the lathe and mill
I have never heard of it, but I have some big problem using centerdrill on my mill.  :Doh:

Benni.
Centre drills are for making tapered holes, to locate on to a lathe centre.....

Spotting drills are for making a starting dimple for drilling, in CNC machining.
The dimple is often made wider than the drilled hole, to leave a chamfer around the finished hole.......

And, there is no tiny centre pip to break off.........   :bang: :bang:

David D
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Still drilling holes... Sometimes, in the right place!

Still modifying bits of metal... Occasionally, making an improvement!

Offline saw

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Re: Another Comber / Coomber build
« Reply #23 on: November 01, 2011, 06:58:01 PM »
Thanks Stilldrillin
(I always read out that as Stilldrinks  :lol: )
I cant figger out what spotting drills is, I have tryed Google translate but no  :doh:
I would like to find something that can help me centerdrill on the mill.  :scratch:
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Offline Stilldrillin

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Re: Another Comber / Coomber build
« Reply #24 on: November 01, 2011, 07:05:53 PM »
Benni.

Search Ebay, for spotting drill. Lots of them available........   :thumbup:


*Note.... NOT spotweld drill.*

David D
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Still drilling holes... Sometimes, in the right place!

Still modifying bits of metal... Occasionally, making an improvement!

Offline Bluechip

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Re: Another Comber / Coomber build
« Reply #25 on: November 01, 2011, 07:06:27 PM »
I have a few modest talents. Knowing what I'm doing isn't one of them.

Offline saw

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Re: Another Comber / Coomber build
« Reply #26 on: November 01, 2011, 08:02:01 PM »
Thanks Bluechip I think I understand now  :doh:
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Offline Bernd

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Re: Another Comber / Coomber build
« Reply #27 on: November 02, 2011, 09:15:45 AM »
I cant figger out what spotting drills is, I have tryed Google translate but no  :doh:
I would like to find something that can help me centerdrill on the mill.  :scratch:

SAW,

Here's what they look like. LINKY

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Offline saw

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Re: Another Comber / Coomber build
« Reply #28 on: November 02, 2011, 09:30:43 AM »
Thanks, I have order one so I will know what you are talking about  :)
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Offline arnoldb

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Re: Another Comber / Coomber build
« Reply #29 on: November 02, 2011, 12:42:40 PM »
Thanks Gents  :beer: - and also for helping Benni out with the spotting drill stuff  :thumbup:

 :lol: I think I jinxed myself earlier in the build by mentioning I need to get spotting drills  :lol:.  They're not available locally, so I have to order from overseas, and right now the N$ is worth nothing, so I'll hang on a bit...  The spotting drills are not cheap!

No shop for me tonight; have to attend to domestic matters  :Doh:

 :beer:, Arnold

Offline DaveH

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Re: Another Comber / Coomber build
« Reply #30 on: November 04, 2011, 01:31:16 PM »
Arnold,

You can get them here in SA :D
 :beer:
DaveH
(Ex Leicester, Thurmaston, Ashby De La Zouch.)

Offline arnoldb

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Re: Another Comber / Coomber build
« Reply #31 on: November 05, 2011, 05:08:04 PM »
Thanks Dave  :headbang: - Aye - Somta makes them, but I nearly had a heart attack when I priced one for delivery here...  I love their tools.  In fact I exclusively buy their drills as they are reasonably priced and very good quality.  But the spotting drills are off the charts, along with their milling cutters.  I'd love to buy them, but economies of scale just does not allow it  :doh:  Have you found any others ? - I'd be happy to try them  :D


This afternoon I had a good solid 4 1/2 hours of shop time   :D

Started off on the base, and poked in the mounting holes for the columns:


I needed to mill a 2mm wide slot 6mm deep - and re-cutting chips is a problem, so I used a bit of wire to pipe in air from the compressor:


That slot would need 10 passes at 0.6mm deep per pass, so I dragged a chair closer and got comfortable.  The first pass nearly done:


And a little while later, all done without any drama:


Then I flipped the base, and countersunk the column mounting holes, and also drilled two 3.3mm holes 10mm deep to tap M4 for the mounting the base to wood later:


A trip to the bandsaw, and I got rid of some excess from the base:


And milled the rest down to size:


I thought I was done, then remembered I still needed holes to mount the cam to - those followed in short order - 2.5mm to tap M3:


When it came to tapping the holes, a problem raised its head - my taps are too short:


That's not the first time I've had this kind of problem with my M3 taps... So I diverted a bit and made a quickie tapping handle for such cases:


It works a treat  ;D - I just have to shorten the grub screw a bit:


I was thinking of making cast-iron bushes to press into the columns - to give good bearing properties combined with the brass that the cylinder block and shafts are made of.  Unfortunately I could not find any in a suitable size, and while I do have some 25mm CI I could turn down, that seems a bit of a waste for such an expensive commodity...  My next best choice was phosphor bronze, which I have quite a bit of and can get at a reasonable price, but research indicates that brass and bronze are "similar" metals and not good for bearings...  Well, I could use steel then; it would be better...  And then my eye fell on the 1m length of 17mm round PTFE I bought more than a year ago at a whim (and very good price).

Well...  Why not?... I don't see plastics used a lot on model engines, but it's supposed to be as slippery as snot, so should make good bushes for this application.  This engine will never be run on steam, so the issues with heat and water porosity shouldn't be a problem...  There are two problems though; a) Would it be acceptable to use a synthetic material in a model like this ? and b) I've never tried to machine PTFE  - not to any sort of accuracy anyway.

As to a) - It "feels" wrong, but then again, I wonder what the Verburgs, Duclosses and Spareys would have done; Some of their build specifications seem to use cutting edge materials in terms of what was available when they built their models, so I'm not going to feel too bad to add a bit of new technology...

And as to b) - Well, there's always a first time  :)

Decision made, I started; I just used my regular HSS tools that I use on everything; I just made sure all the cutting edges were honed sharp.  Cuts easily, though I had some chatter as I didn't add tailstock support right from the start, but even parting off is a breeze  ;D - small diameter bush done:


Bigger diameter bush in-making:


Both bushes were turned on the OD to a press fit in the columns.  I'm surprised; it was easy to accurately turn the plastic and get fairly acceptable finishes; I expected to struggle a bit with that, but it turned out rather well.  Pressing the inserts into the columns made a fairly significant change on the ID's of their bores. 
So I decided to try out my hand reamers on them; the 6mm one for the small shaft went well, and easily cut the bush ID to size again without any complaints.

The 12mm reamer was another matter; it wanted to chatter - severely...  I was trying dry cuts, so I decided to try a little lubrication... But what  :scratch:.  I settled on a squirt of the synthetic oil/water mixture I use when parting off steel; it worked a treat and the reamer smoothed right out and cut nice even chips out of the hole   :ddb:

For today's work, I ended with this lot:


I'm surprised by how well the PTFE bushes work  :D:
http://youtu.be/D8wbTMHXql8

The bush on the thin axle looks like cr@p though, so I think I'll make an aluminium insert to press in with a smaller bush that will be hidden by the flywheel hub later on.  I can make the ali insert nearly invisible and things should look nicer.
 :beer:, Arnold

Offline arnoldb

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Re: Another Comber / Coomber build
« Reply #32 on: November 06, 2011, 02:53:41 PM »
Today's four hour stint was done on the cam ring; it's not finished, but at least some progress.

I printed out the list of machining diameters  (Many Thanks goes to Gail Graham for making up the spreadsheet I used), jotted down some notes of things to keep in mind on it, and sawed a bit of 2mm brass plate from some stock I have:


The plate was smeared with some permanent marker ink, and laid out for the most important bits:


On to setting up for machining, and oh dear; it's too big for my rotary table:


But it will fit on the lathe's face plate if I mount that to the RT  :D:


I found a bit of wood off-cut  from last year's kitchen renovations, and mounted the workpiece to it with some self-tapping screws through the center bit where the screws will be inside the cutting tool path.  After that, I drilled holes through the corners where excess will be, but spaced to match up the face plate's slots when the workpiece is centered:


Mounted the face plate on the RT, and centered the RT on the mill as well as zeroing the X and Y handwheels - making an additional note on the cutting chart as to which direction I was moving the table when zeroing the handwheels:


Then I mounted the workpiece on the face plate, lightly tapping it till I could get it as centered as possible.  The mill's X and Y wheels were left strictly alone on zero.  The idea is to center the workpiece to the center of the RT here:

I also tried to get the base reference as parallel to the X travel of the mill as possible by eye.

Once I was happy that the workpiece was centered, I cranked on X to check on the rotational orientation:

I'd eyeballed the rotation to less than half a degree, so I cranked the RT to bring the line on center and zeroed its dial.

One disadvantage of having screw-on chucks/faceplates is in a scenario like this.  In this case, the face plate screwed on with it's slots offset by about 30 degrees, so I couldn't use the RT's own degree scale:


Oh well, a permanent pen can make a new scale; I'm going to work without any cutting fluid, so the markings won't be washed off:


Next I bodged up a DRO - One day I'll get proper DRO's but for the most part I don't mind reading the handwheels:

 :lol: - I did say "bodged up"   :lol:

A final check of everything later, then a cup of coffee, pulled up a chair, and started...  I'd calculated the cutting path for a 12mm cutter, so I drilled a 10mm hole to start things at the first coordinate after locking both X and Y axes on the mill and the RT's table.  The hole is to give the cutter less material to cut away for a start - and prevent things moving:


Then I started with the 12mm cutter - same location and drill it out to size, mark the first coordinates on the sheet done.  Then the roundabout began... Unlock RT, feed 2 degrees, lock, unlock X, dial in the new coordinate, lock, drill new location, mark as done on the sheet.  Repeat.  About 60 degrees later:


I stopped for the day at 178 degrees:


It takes about 45 minutes to do 90 degrees and a LOT of concentration (maybe I'm just a slow worker  :lol:).  One mistake, and I'll get to start all over   :coffee:  And it is a bit of a mind-numbing process, so better to carry on when I'm fresh.  That's why I put a new battery in the caliper; so it can "remember" the last reading, and why I meticulously marked off each position as it was done and the state of the mill when I started; at least I can stop and pick up from there later.

 :beer:, Arnold

Offline arnoldb

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Re: Another Comber / Coomber build
« Reply #33 on: November 13, 2011, 11:16:11 AM »
After a hectic work week and most of my weekend spent on getting an additional data center going for my company I finally got some shop this afternoon.

Finished off the last 180 degrees of the cam:


Drilled the two 3mm mounting holes:


I nearly forgot to clamp down the outer bit to the wood block before removing the bolts holding everything to the face plate...  Fortunately I realised just in time and added a couple of screws through the mounting holes to keep it in place.  The whole lot needed to be moved on the face plate to the outer ring center to finish things off, and if it moved it would have lost its place on the center piece that has the center position marked! :


Of course, last weekend in a blinding flash of idiocy I didn't drill additional mounting holes offset with the required 8mm from the initial ones, so no mounting holes could align with the face plate slots once I moved the workpiece to the new center   :lol: - So I grew a forest of clamps to finish the rest of the machining operations:


That meant I had to stop during machining to move clamps around to get out of the way - here is one of the stoppages to move a clamp:


Finally - all machining done on the cam three hours into the shop session:

Not a miss-step or anything, and that's the hardest part of this build done   :ddb: - just some clean-up left to do.

A close-up of the cusps left by the machining process on the inside of the cam:


They look worse than they are; a little very light and careful filing with a 250mm fine half-round file brought the roughness down very quickly till all the cusps were barely visible and even in size right around the ring.  Then I wrapped some 320 emery around a bit of 50mm pipe, and in careful circular motions around the ring removed the last visible signs of the cusps.  All this was done very carefully; things needed to just be smoothed out; the shape mustn't change.

After a bit of file work around the outside of the ring to get rid of tool marks, and a rub over some emery and a quick rub with scotch-brite to give a brushed finish, the cam is done:


What do you know? - things fit together and is starting to look like an engine:


That's the engine half-way done then; so only 90% to go   :)

 :beer:, Arnold

Offline sbwhart

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Re: Another Comber / Coomber build
« Reply #34 on: November 13, 2011, 12:37:48 PM »
That cam ring realy look the buisness, cracking bit of machining Arnold.

 :clap: :clap: :clap: :clap: :clap: :clap:

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Offline saw

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Re: Another Comber / Coomber build
« Reply #35 on: November 13, 2011, 01:59:39 PM »
Fine as usual, but I have to ask  scotch-brite what is that? :doh:
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Offline Bluechip

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Re: Another Comber / Coomber build
« Reply #36 on: November 13, 2011, 02:13:08 PM »
Benni

Abrasive pad, similar to this ...


http://www.arceurotrade.co.uk/Catalogue/Abrasives/Hand-Pads

Cheaper than genuine Scotchbrite, but just as good for most things ,,

BC
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Offline Kjelle

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Re: Another Comber / Coomber build
« Reply #37 on: November 13, 2011, 02:28:23 PM »
Fine as usual, but I have to ask  scotch-brite what is that? :doh:

Hi Benni!

Dom där gröna disksvamparna, du vet...

Kjelle

Offline saw

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Re: Another Comber / Coomber build
« Reply #38 on: November 13, 2011, 03:03:43 PM »
Thanks everyone  :clap:
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Offline Brass_Machine

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Re: Another Comber / Coomber build
« Reply #39 on: November 13, 2011, 11:33:39 PM »
Another one that I missed.

Excellent work!

Eric
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Offline Stilldrillin

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Re: Another Comber / Coomber build
« Reply #40 on: November 14, 2011, 02:18:12 AM »
Fine work done well, Arnold!  :clap: :clap: :thumbup:

David D
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Offline Doc

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Re: Another Comber / Coomber build
« Reply #41 on: November 14, 2011, 10:46:00 AM »
Looking good Arnold. The cam ring looks nice I have to laugh at your comment 50% done only 90% to go.
 That's how I feel some time during a build.
Keep up the good work!
George

Offline arnoldb

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Re: Another Comber / Coomber build
« Reply #42 on: November 15, 2011, 12:51:00 PM »
Stew, Benni, BC, Kjelle, Eric, David & George - Thanks for checking in Gents   :beer:

Benni, like BC said - scouring pads  :thumbup:.  The ones I use are the green ones available in grocery shops for scrubbing post & pans in the kitchen.  I tried some other brands that's available on the shelves, but the genuine 3M Scotchbrite sold in the kitchen section works best for me; I use a lot of them; half in the shop and the rest for scrubbing pots that burned on while I'm posting  :D  :lol:

George, glad you had a laugh; the 50% done and 90% to go seems to be a sort of a fact while building engines.  For me, that's mostly because I tend to start with the easiest-to-make parts, which are normally the biggest.  The hardest part of any build is in the handful of small bits; they take more time and setup to make, and trying to get a good finish on those are the hardest.  All good fun though  :D

I stole an hour in the shop after work today; decided I'll fix up one of the eye-sores...

I removed the big ugly PTFE bushing from the "thin-shaft-side" bearing column, and turned up an aluminium filler piece and smaller PTFE bush, all for press fits:

The PTFE bush I did twice; on the first attempt I turned it's OD 0.02mm under the size needed, and that resulted in too light a fit...

The aluminium insert pressed into the big hole:


After a bit of filing and emery, the joint is nearly invisible:

You can click the photo above to see a bigger version; there it's more visible.

New bush pressed in - intentionally standing 0.5mm proud on either side of the bearing column:


That looks a lot better; in fact, once the flywheel is mounted, the plastic bush will be nearly hidden:


 :beer:, Arnold

Offline cfellows

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Re: Another Comber / Coomber build
« Reply #43 on: November 17, 2011, 10:50:14 AM »
Coming together very nicely, Arnold. 

Chuck

Offline saw

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Re: Another Comber / Coomber build
« Reply #44 on: November 17, 2011, 12:58:17 PM »
Nice build, when this engine is finish there is a small chance that I understand this engine  :lol:
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Re: Another Comber / Coomber build
« Reply #45 on: November 18, 2011, 04:12:43 PM »
Hi Arnold  :clap: :clap: :clap: :clap:


Well done mate ,,,,,,,cam ring came out great  :bow: :bow:

Rob  :D

Offline DaveH

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Re: Another Comber / Coomber build
« Reply #46 on: November 19, 2011, 01:58:38 PM »
Arnold,

Coming along great :thumbup: :clap:
 :beer:
DaveH
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Offline arnoldb

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Re: Another Comber / Coomber build
« Reply #47 on: November 19, 2011, 07:49:49 PM »
Chuck, Benni, Rob & Dave, thanks for checking in Gents  :beer:

Benni , it's starting to come together now  :thumbup: - Just ask if you want to have more detail; I'm happy to try and help  :D   :thumbup:


Today's bit; I had a good shop session, so lots of photos...

I started work on the piston.  Earlier in the build, I left the bore of the cylinder just a tad under the 16mm I wanted.  That was on purpose; I have some 16mm round brass bar to make the piston from, but it needs a bit of skimming, so will end up under 16mm.  I chucked the brass bar up in the collet chuck on the lathe, and faced it and then parted it down part-way on 5mm length:

Starting with a partial parting cut might seem silly, but there's a reason for it.  If you look closely at the above photo, you'll see the burrs raised on both sides of the parting cut.  If I left this for last, that would leave a ridge on the piston that I'd have to remove in some or other fashion - and there's no easy or accurate way.

A little later, and I'd used a small file to put chamfers on both sides of the piston, a free-hand oil groove with a triangular needle file, then turned it to final size and drilled it 2mm through the center:


After finishing the parting cut, I ended up with this:

The face shown is on the parted-off side; I still need to practice parting a lot more to get better finishes.  The pronounced countersink on the hole was added manually; on both sides of the piston; these are needed for later steps.

Next I started on the forks.  Drilled a 1.6mm hole through some 6mm thick square brass:


Then I mounted the slitting saw on the mill and used my height gauge to pick up the top of the block and set the slitting saw to height:


I just used my 0.5mm slitting saw to slit through for the fork bodies deep enough to later cut them off.  Then added my 1mm slitting saw to the arbour to start cutting the forks - using the height gauge again - this left a 1.5mm wide slot; which I just slit to depth on the line I'd marked:


I then moved the mill quill down by 1mm, and slit again - leaving a 2.5mm wide slot, and then moved down and repeated:

If you look carefully, you'll see there's two stilling saws ganged together; a 1mm and a 0.5mm one.  I really need to buy more slitting saws :big:

The block was then flipped in the vise and clamped down with a generous bit of cardboard to prevent things moving, and then the two forks slit off from the parent stock:


I then drilled the backs of the workpieces 1.6mm to tap M2 later:


After tapping and then some free-hand filing to round over the ends, the forks were done:


I needed some bolts to hold the cam to the base.  Any old 3mm screw would have done, but I rather made my own. Here's some 5mm hex brass turned down and threaded with the tailstock die holder:


After some more machining, I had these:


The cylinder block needed some holes plugged - just two bits of 2mm brazing rod plugged in with high-strength retaining compound:

Ugly, innit ?  ;D

Some more 2mm brazing rod followed to make the connecting rod; threaded both ends M2 to fit the forks and lock nuts.  The piston have to be soldered on in the middle:


I used some aluminium drinks-can plate to clamp down the connecting rod with the piston in place.  The plate keeps the piston on the correct height and prevents the vise from marring the connecting rod.  Any solder that leaks through won't stick to the aluminium plate either:


Some soft-solder flux was brushed on before assembly, then I soldered the lot together with some electronics solder. I just used a small plumber's blow-torch to heat things up.  It looks horrible here, but worked quite well:

Remember the chamfers I mentioned on the piston earlier on? - This is where they came into play; I made the hole in the piston a relatively tight fit to the connecting rod, but they had to be soldered together, and with the hole being tight the solder would not flow through.  The chamfers provide the necessary area for the solder to make a reasonable secure joint.

Next I cleaned up some 6mm silver steel rod and drilled it through and reamed to 4mm, and parted off two rings 2.4mm thick:


Some brass followed, a tad under 4mm OD for a smooth running fit in the silver steel above, and parted off at 2.5mm lengths:


Makes for some OK bearings:


A quick trial-fit in the cam, and I could see how much to adjust the forks in the connecting rod:


All assembled together:

Please excuse all the oily marks and so on; when I assemble something for the first time, I use a LOT of oil.  As can be seen from the photo, I''d also filed down and smoothed over the plugs on the air passages to blend in to the main shaft

There was a couple of tight spots on the cam with things all assembled; that was easily taken care of with some light filing and emery paper.
Things turned over fairly smoothly after that by hand, but wouldn't give me the easy flick with multiple rotations... and I was NOT happy; I'd built this engine so far to be EASY to run!
It was supposed to spin like a top...

At this point Thor threw a hammer at me noggin, and connected... HARD... ; Well, DUHHH - I've not yet drilled the main bearing column for an  air supply or exhaust...  - There is nowhere for the cylinder to suck or vent...  So obviously it would not run well  LOL - It needs a bit of breathing  LOL

Regards, Arnold
« Last Edit: November 20, 2011, 12:20:30 AM by arnoldb »

Offline Stilldrillin

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Re: Another Comber / Coomber build
« Reply #48 on: November 20, 2011, 02:32:22 AM »
Nicely done, and shown Arnold!  :clap: :clap:

Hope it's soon spinning free..... It's always a nice moment, when you hear an engine start breathing........ :thumbup:

David D
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Still modifying bits of metal... Occasionally, making an improvement!

Offline arnoldb

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Re: Another Comber / Coomber build
« Reply #49 on: November 20, 2011, 02:05:05 PM »
Thanks David  :D - I agree; that first time an engine starts is always the best :D

I didn't get a lot done today, but had quite a bit of fun   :ddb:

First I drilled the column for the port holes - just 2.5mm straight through the center through both sides.  One side will be tapped M3 for the airline connection, and I used a 6mm end mill to make a flat for the connector to screw up to:


Then I turned up the airline connector from some 6mm hex brass:


And then the real fun started; everything except the flywheel was there to give the engine a test run - so I tried it   :dremel::
<a href="http://www.youtube.com/watch?v=jHJ0YAyGoA4" target="_blank">http://www.youtube.com/watch?v=jHJ0YAyGoA4</a>

 :ddb: :ddb: :ddb: :ddb: - I didn't even know if it would run after all the changes I made.

I borrowed the flywheel off my grasshopper engine, and added that; after about 10 minutes of running, it could do slow too:
<a href="http://www.youtube.com/watch?v=gSra3sXZQoE" target="_blank">http://www.youtube.com/watch?v=gSra3sXZQoE</a>


It's not quite running on breath power; an almighty blow gets me a couple of turns, but I think I can get it running as I want with a slightly bigger diameter flywheel with most of the weight in the rim and some additional run-in time. 

So, it's flywheel, wooden base and final cleanup to go now...

 :beer:, Arnold

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Re: Another Comber / Coomber build
« Reply #50 on: November 20, 2011, 02:18:03 PM »
ITS A RUNNER[/glow]

Cracking job Arnold I just love to follow your threads.

 :thumbup: :thumbup: :thumbup:


 :clap: :clap: :clap: :clap:


 :nrocks: :nrocks: :nrocks:

Stew
A little bit of clearance never got in the road
 :wave:

Location:- Crewe Cheshire

Offline Stilldrillin

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Re: Another Comber / Coomber build
« Reply #51 on: November 20, 2011, 03:46:29 PM »
YEEeee.... HAAaaarrrrrrr!!!   :ddb: :ddb: :ddb:   :D :D

 :bow: :bow: VERY nicely done Arnold!

David D
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Still drilling holes... Sometimes, in the right place!

Still modifying bits of metal... Occasionally, making an improvement!

Offline AdeV

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Re: Another Comber / Coomber build
« Reply #52 on: November 20, 2011, 04:24:42 PM »
Fantastic build Arnold, that's a real beauty. And properly unusual too... Elmer must have been on something when he designed that one...

Can't wait to see it properly blinged up & running on lungs  :thumbup:
Cheers!
Ade.
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Offline grayone

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Re: Another Comber / Coomber build
« Reply #53 on: November 21, 2011, 02:32:03 AM »
Fantastic build Arnold, that's a real beauty. And properly unusual too... Elmer must have been on something when he designed that one...

Didn't these strange contraptions appear as a result of Stevenson's patent on his steam engine?

Anyway a real fun looking machine and some real smart machining to boot :headbang:
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Offline millwright

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Re: Another Comber / Coomber build
« Reply #54 on: November 21, 2011, 05:50:37 PM »
Lovely job Arnold enjoyed the build and good looking engine. Mmmm wonder whats next?
John

Offline saw

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Re: Another Comber / Coomber build
« Reply #55 on: November 22, 2011, 05:14:47 AM »
Just fantastic good work Arnold  :bow: :bow:
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Offline arnoldb

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Re: Another Comber / Coomber build
« Reply #56 on: November 22, 2011, 11:23:34 AM »
Many thanks Gents   :beer:

Still quite a bit left to do though  :D

Grayone, yes, many different engines appeared because of patents.  Many of the rotaries appeared because of patents on the original crank; can't recall if that was Stephenson or Watt that held that patent though.

John, like I said, there's still quite a bit left to do on this one.  After that, there is some tooling, and then another "weird" engine  :D - that is if I stick to my planning  :lol:

 :beer:, Arnold

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Re: Another Comber / Coomber build
« Reply #57 on: November 22, 2011, 11:33:08 AM »
 :bow: :bow: :bow: :bow: :bow: :bow: Nice one Arnold  :clap: :clap: :clap: :clap: :D

Rob  :)

Offline DaveH

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Re: Another Comber / Coomber build
« Reply #58 on: November 22, 2011, 12:27:05 PM »
Arnold,

Great stuff,   :thumbup: :clap: ........    "keep puffing"

Really looks good :bow: :bow: :bow:
 :beer:
DaveH
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Offline Brass_Machine

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Re: Another Comber / Coomber build
« Reply #59 on: November 22, 2011, 02:39:11 PM »
Woot! Very nice!!!
Science is fun.

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Offline spuddevans

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Re: Another Comber / Coomber build
« Reply #60 on: November 22, 2011, 02:46:02 PM »
Dunno how I missed this thread, but well done Arnold on another runner  :clap: :thumbup: :clap: :thumbup: :clap:

Nice and unusual engine.


Tim
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Offline arnoldb

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Re: Another Comber / Coomber build
« Reply #61 on: November 27, 2011, 11:07:51 AM »
Rob, Dave, Eric & Tim - thanks gents  :beer: - apologies for the belated thank-you!

I didn't post yesterday's work yesterday evening, as a social commitment ( :beer:) interfered  :D

Work started on the flywheel.

I got a phosphor bronze off-cut from one of my suppliers - not cheap, but it was the best I could do:


Started cleaning it up; this piece is just long enough to make two flywheels from.  I've machined quite a bit of PB so far - always without any problems, but this piece was giving me some grief; it had soft and hard spots in it and was a bear to turn:


Parting it off was no fun; my rear parting tool wouldn't touch it, even though I'd honed it up super sharp! So I tried my old jig-saw parting bit and that ran through it without any problems:


After some more turning, I had the flywheel rim:


Next I turned up the flywheel hub, and drilled six 2mm holes in it for spokes, and a 2.5mm hole between two spoke locations to tap M3 for a grub screw:

While I had the dividing head mounted on the mill, I also drilled the rim for the spokes.  The hard and soft spots made the drill wander quite a bit in each hole...

Spokes were cut from 2mm brazing rod, and one end of each cleaned up with a file:


The wandering of the drill in the rim made for a tight fit for the spokes through the rim; I had to resort to a small hammer to tap them in to just outside of the hub's radius.  Then I set the hub on a piece of 6mm rod in the tailstock to help with positioning:


I put a drop of retainer in each hole in the hub, and also on the bits of the spokes still sitting outside the hub.  Then I tapped each spoke in.  I then moved away the tailstock, and with the rod left in the hub, I clocked the hub as center as I could by lightly tapping the bits of spoke still sticking out of the rim.  Because the holes through the rim had wandered, axial run-out would have caused a very wobbly flywheel - so I checked further away as well, and used the rod to bend the spokes slightly to get the wobble out:


The flywheel was then set aside to let the retainer cure overnight.  The spokes need to be filed or turned down later:


On to some woodwork...
Earlier this year while visiting, my father brought me a circular saw and a mounting table that my grandfather had very generously donated to me:

I haven't used it yet as I steer away from woodwork in general, but now was the time to try it   :dremel:

The piece of teak I have for bases is quite difficult to cut with a jigsaw as I had done in the past - the circular saw did in seconds what used to take me many minutes to get done:


A final cleanup of the uncut edges of the block was done on the mill:


The piece of timber is very rough, and had spent quite a bit of time out-of-doors before I bought it, so all the faces are impregnated with dust and sand, so instead of breaking out the wood plane to plane down the flat faces, I used a very sharp HSS flycutter on the mill:

That left a really smooth finish  :D

Mounting holes for the engine base was drilled - part-way 8mm and then 4mm through - to match some M4 countersink screws I have:


I used a router bit to add a bit of detail - first on both cross-grain faces:

As can be seen in the photo above, the cross grain faces splintered out a bit, but the splintered bits are in areas that would be removed when routing along the grain - without additional splinters coming off.

After a final bit of work with sand paper, the base was looking OK:

I then lavishly applied furniture wax to it, and set it in the sun to have the wax draw into the wood a bit.

Work stopped there for yesterday - I'll carry on in another post for today's bit; have to finish uploading some things first  :)

 :beer:, Arnold

Offline arnoldb

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Re: Another Comber / Coomber build
« Reply #62 on: November 27, 2011, 01:12:44 PM »
On to today's bit...

The good news is the engine runs, but bad news is there's some of the last machining photos missing, as my camera's batteries gave out after the first photo and the spare set was flat as well  :doh:

To clean the bits of spoke sticking out of the flywheel, I trimmed them as close as I could with a side-cutter, and turned up a mandrel to mount the flywheel on.  I just filed a flat on it for the grub screw to locate on to hold the flywheel in position:


The batteries gave out and was put on charge, so some typing to explain what happened next:

I turned the outside of the flywheel down very carefully - till the spoke ends were off and I then gave it a very light finishing pass across the rim.  Even though I worked as carefully as I could, the interrupted cuts and finishing pass brought the rim into a wobble.  As I can't fiddle with it too much, I trued it up as well as I could, but it still runs slightly wobbly   :(; I should have silver soldered the spokes in instead of using the retainer.

The waxed wooden base was given a vigorous rubbing with a soft cloth, more wax applied and more buffing with the cloth.  I could have painted the base with clear varnish, but I just like the way waxed & polished wood looks, feels and smells - even if it needs a bit of wax every now and then.  My sis knows the drill with the floor & furniture wax   :coffee:

I disassembled the engine and gave everything a final clean-over.  All the finishes will be left as-is; the engine is fairly big (compared to my other builds) and I think polishing bits of it will be a bit too much on the eye.  Also, polished surfaces need attention over time to keep them shiny, and the engine is actually quite delicate - if the cam ring bends slightly or pressure is exerted on the connecting rod or forks, it can go from a good runner to a non-runner in no time.

After cleaning and final assembly (and charged batteries), the engine looks like this:






I tried a couple of different locations for taking the finished photos; the above ones were the best lot from the lot, but this one is OK as well:


After some oil on the cam; a bit too much  :coffee: - it still runs very well:
<a href="http://www.youtube.com/watch?v=rqDfsFwSgKI" target="_blank">http://www.youtube.com/watch?v=rqDfsFwSgKI</a>

One of the aims of this engine was to have it run on breath power.  It does, but still needs a bit more of running in.  Please excuse the ugly mug intruding in the scene   :lol::
<a href="http://www.youtube.com/watch?v=flnqLdfuTIY" target="_blank">http://www.youtube.com/watch?v=flnqLdfuTIY</a>

My sister will hopefully visit in the next couple of weeks, then I can present it to her   :ddb: :ddb: :nrocks:

Another fun build done... Time to clean the machines, make a bit of tooling, and then on to the next engine.

 :beer:, Arnold

Offline saw

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Re: Another Comber / Coomber build
« Reply #63 on: November 27, 2011, 01:18:40 PM »
Congrat a fine peace of art
 :bow: :bow: :bow: :bow: :bow: :bow: :bow: :bow: :bow: :bow: :bow: :bow: :bow: :bow: :bow: :bow: :bow: :bow: :bow: :bow: :bow: :bow: :bow: :bow: :bow: :bow:
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Offline Stilldrillin

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Re: Another Comber / Coomber build
« Reply #64 on: November 27, 2011, 03:55:27 PM »
Really top class build Arnold!  :clap: :clap:

Classy woodwork.  :thumbup:

I can't see any flywheel wobability!  :scratch:

Well done!  :D

David D
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Still drilling holes... Sometimes, in the right place!

Still modifying bits of metal... Occasionally, making an improvement!

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Re: Another Comber / Coomber build
« Reply #65 on: November 27, 2011, 04:25:36 PM »
 :bow: :bow: :bow: :bow: :bow:  great job Arnold ,,,,,,,,,,, well done mate  :clap: :clap: :clap: :clap:


Rob


PS ,,,,,,,,, probably would go faster if you cut out the tabs  :lol: :lol: :lol: :lol: :lol: :lol:

Offline millwright

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Re: Another Comber / Coomber build
« Reply #66 on: November 27, 2011, 05:17:31 PM »
Lovely job Arnold,
I know when You started it i had never heard of one, so have followed the thread right through. A nice bit of grain and a good finish on the brown stuff.
John.

Offline cfellows

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Re: Another Comber / Coomber build
« Reply #67 on: November 27, 2011, 11:23:53 PM »
Very Nice, Arnold!  I especially like the flywheel.  I'm kind of partial to skinny spokes.  Great runner!   :bow:

Chuck

Offline arnoldb

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Re: Another Comber / Coomber build
« Reply #68 on: November 28, 2011, 12:14:08 PM »
Thanks Benni  :D

Cheers David  :beer: - the wheel is a tiny bit wobbly and I'm darn critical of my own work  :lol:

Rob, thanks mate  :beer::lol: :lol: I do need to cut down on the tabs  :Doh:

Thanks John  :beer: - I like these "different" engines; the next one will be quite a bit of fun to build as well.  Have you heard of a Kimble engine ?

Chuck, thank you  :beer:.  I like the thin spokes as well; I was debating with myself whether to make them 2mm or 1/8" on this engine.  The thicker spokes are easier to make and less hassle with drilling the holes for them, but would have looked a bit out of place on this engine; I tried to copy the look of the connecting rod and cam ring through to the flywheel.

Some tooling work coming up tomorrow evening  :D

 :beer:, Arnold

Offline sbwhart

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Re: Another Comber / Coomber build
« Reply #69 on: November 28, 2011, 12:40:45 PM »
Cracking build Arnold:-   :clap: :clap: :clap: :clap: :clap: :clap: :clap:

That fly wheels looks particularly nice  :thumbup:

As for the breath power, you could use it as a smokers gauge, the more fags/day the fewer revs/ breath.

 :D :D :D :D :D

Stew
A little bit of clearance never got in the road
 :wave:

Location:- Crewe Cheshire

Offline DaveH

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Re: Another Comber / Coomber build
« Reply #70 on: November 28, 2011, 04:22:22 PM »
Well you have done it again Arnold  :clap: :thumbup:

That is a really great looking and running engine. :bow: :bow:

Nice to see you still have some puff in those lungs, hope it didn't make you dizzy and fall over like it does to me.  :lol: :lol: :lol:

Great post as well, nicely photographed and written. :clap: :clap: :clap:
 :beer:
DaveH
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Offline millwright

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Re: Another Comber / Coomber build
« Reply #71 on: November 29, 2011, 03:46:30 PM »
Hi Arnold
Ive downloaded a kimble engine plan from John Tom, looks interesting i think I've got it figured out, I'm sure it will all drop into place when you start your build. Not done very much myself since i joined this forum, I'm waiting to have both knee joints replaced the first was going to be this Thursday but its now been cancelled cause my blood pressure was high, so now i have to wait for the new medication to kick in. My lathe now cleaned oiled and covered for the winter, unless someone needs some small job doing. cant stand for long and it doesn't feel right turning from a stool.
John

Offline Kjelle

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Re: Another Comber / Coomber build
« Reply #72 on: November 30, 2011, 04:39:07 AM »
Hi Arnold!

You make stuff in a way I can only dream of! I havn't touched a lathe or mill for over 30 years, and long to make some chips after reading through this and other threads...
 :bow:

It doesn't make it any easier when you have a complete prototype workshop on your beat! I go in there and talk to the guys if they are working overtime, just to smell the cutting fluids, and look at the machines...
 :drool:
Kjelle (impressed beyond comprehension!)

PS; The workshop is Atlas Copco's, at their head office in Stockholm... DS

Offline arnoldb

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Re: Another Comber / Coomber build
« Reply #73 on: December 01, 2011, 05:03:55 AM »
Thanks Stew  :beer::lol: I like your idea of the smoker's gauge  :lol:

 :beer: Cheers Dave - it doesn't need to be blown hard enough to make me want to fall over  :lol:

Good luck with the knee ops John  :thumbup: - my lathe is mounted too high to sit down at, but I regularly grab a chair up to the mill to sit down for long jobs; this engine's cam ring was machined sitting down...  Saves a crick in the back.

Thanks Kjelle  :beer:.  Two years ago I also only dreamt of making things like this; it just takes a bit of work to start turning dreams into reality  :thumbup:.   :D Must be great getting into Atlas's workshops; they make great compressors  :thumbup:

 :beer:, Arnold