Author Topic: A Cracker locomotive  (Read 61293 times)

Offline DaveH

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Re: A Cracker locomotive
« Reply #50 on: August 21, 2011, 03:53:23 PM »
Arnold,

I missed you, thought you had left us :(

Nice to see you're back :D

Well it does look nice, what is it for. :scratch:

 :beer:
DaveH
(Ex Leicester, Thurmaston, Ashby De La Zouch.)

Offline Stilldrillin

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Re: A Cracker locomotive
« Reply #51 on: August 22, 2011, 03:46:47 AM »

And no progress to report on the cracker; I finally got some shop time today and squandered it on this lot  :doh: :
 :beer:, Arnold

Well squandered Arnold!  :clap:  :thumbup:

But..... Worrisit?  :scratch:

David D
David.

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

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

Offline sbwhart

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Re: A Cracker locomotive
« Reply #52 on: August 22, 2011, 04:39:25 AM »
Arnold,

I missed you, thought you had left us :(

Nice to see you're back :D

Well it does look nice, what is it for. :scratch:

 :beer:
DaveH

Same her

What is it for  :scratch: :scratch: :scratch: :scratch:

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

Location:- Crewe Cheshire

Offline arnoldb

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Re: A Cracker locomotive
« Reply #53 on: August 22, 2011, 03:14:39 PM »
 :beer: Cheers Gents

Dave, I'm like weed (no, NOT the Dutch/Hippie type! - the unwanted stuff you get in the garden :lol:) - You'll have one hell of a time trying to get rid of me as  :nrocks: :D :D :D
 :doh: Been working like a dog at my office job for the last 3 weeks; sometimes up to 16 hours a day, so shop was a tad out - nothing like a tired mind in the shop to sacrifice body parts to the machines...

 :lol: :lol: As to the mystery pieces, it's an "Executive Toy" for my decidedly non-executive office desk  :lol: :lol: - it's a finger engine in progress with a clutch system to allow it to free wheel.  Just working from odds 'n ends I have lying around, and already the clutch mechanism needs to be redone as it's not as reliable as I'd like it.  Not really up to my personal standard of appearance, but it's for some quick gratification, so I'll call it a bit "rustic" and carry on.  Friday's a public holiday here in Namibia and I bluntly told my bosses I'm taking my long weekend, so I'll try and finish it on Friday, and use the rest of the weekend on the Cracker again.

 :beer:, Arnold

Offline arnoldb

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Re: A Cracker locomotive
« Reply #54 on: August 28, 2011, 02:33:47 PM »
Well, squandered more time on the finger engine, and it resulted in this:





On to the Cracker then  :D - not much but some done...

Used a bit of bronze to start the smokebox "door" from:

A bit of a waste of this bronze, but it's easier to find locally than brass is - and approximately the same price!

Turned it down for a light push fit in the boiler smokebox, and hollowed it out quite a bit.  Then flipped it and started turning the outside detail for the smokebox.  First just some free-hand turning, juggling the apron and cross slide; my ball turner can't get that close to the chuck:


Followed by a file (VERY carefully, as those chuck jaws were close!) and some emery:


Then a hole in the centre - tapped M4 to fit a handle; I must still decide whether I want a lever or a wheel style.  Also milled out clearance for the chimney on the back side:


It looks OK on the boiler  :D :


And that's it for now.  I'll see if I can get small bits done during the week; next weekend I have to work at the office  :doh:

 :beer:, Arnold

(Edited for some gross spelling mistakes!)
« Last Edit: August 28, 2011, 04:09:16 PM by arnoldb »

Offline ozzie46

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Re: A Cracker locomotive
« Reply #55 on: August 28, 2011, 03:00:40 PM »



  Arnold, that's a cracking looking little cracker there. :D :D :D :D

Very nice

 Ron

Offline saw

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Re: A Cracker locomotive
« Reply #56 on: August 28, 2011, 05:03:23 PM »
Good work  :thumbup:
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Offline DaveH

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Re: A Cracker locomotive
« Reply #57 on: September 01, 2011, 02:59:31 PM »
Arnold,

Quite a little violent finger engine, like the 'free wheel'. :thumbup: :thumbup: :thumbup:

Cracker is coming along very good, the dome looks good. :thumbup: :clap:
 :beer:

DaveH

 
(Ex Leicester, Thurmaston, Ashby De La Zouch.)

Offline arnoldb

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Re: A Cracker locomotive
« Reply #58 on: September 03, 2011, 02:37:44 PM »
Ron, Benni, Dave - thanks Gents  :beer:

 :D Sometimes a work week that's gone badly makes for a great weekend...  I had some crises thrown at me during the week at the office, with a result that I could not get around to do the prep that was needed for this weekend's work, so I got shop time  :ddb:

First order of the day was to start on the safety valve.  I turned a bit of 8mm hex brass down to 6mm and threaded it M6x0.5 to fit the treads in the boiler bushes.  I still have not been able to find a decent M6x0.5 die nut, so I just used the "thread cleaning" nut I have supported by one of my tailstock die holders to thread the workpiece:


Parted off to a suitable length, I chucked it up in reverse, and started drilling...  First 2mm right through, then 5.5mm to a suitable depth for threading M6x0.5 - which was duly threaded.  Then I used a 5mm end mill to flatten out the bottom of the hole:


A bit more drilling, this time 3mm diameter and about 3mm below the bottom of the flat section.  This is a lot of faffing around - I'm out of 3mm stainless steel balls to use in the valve, so now it's on to a pop-style with O-ring.  That'll teach me to run out of balls  :lol:  The (nearly) finished safety valve body on the boiler, with the 5mm flat barely visible around the 3mm centre hole:


Next the adjusting nut; a bit of brass round turned down to 6mm, and a 1mm hole poked through the centre:


Then threaded M6x0.5 on the outside and parted part-way, and off to the rotary table on the mill to add some 1.5mm slots around the outside; these will allow steam past the adjusting nut:


After some more lathe work to turn the valve itself I had all the bits together for the safety valve; the O ring from a kit, the "brass" pin (actually coated soft steel) from a packet of Cheap 'n Cheerful Chinese design-your-own jewellery stuff, and the spring from a cheap disposable lighter:

A stainless or bronze spring would be better, but I couldn't find any; older style tire valves had some nice springs, but the new ones are not suitable...  Fortunately, if the spring corrodes from steam vapour, it will reduce the safety valve's operating pressure.

Then I soldered the pin to the valve and assembled the lot after trimming a section of spring off.  A quick check with the compressor showed that the valve works nicely, which I hadn't expected on my first try with this type of valve; it was easy to adjust to open at 35 psi and repeatedly re-sealed properly without leaking.  Assembled it looks like this; it still needs final setting while on steam, but the adjustment range is good so I added a little loop to the top of the valve spindle to make it easier to test manually that it's not sticking:


The hex valve body was definitely not pleasing on the eye, so I made up a quick mandrel and turned down the body a bit:


On to a bit of planning...  It was high time I sorted out what I wanted to do about the smokestack and cab.  This engine will be used quite often to "play" with and show off, and while it is roughly based on a real model, it's more of a fun toy than a model, and it should look the part.  I scrounged around a bit and found the extra pipe reducer I bought "in case" when I built the burner for the Little Blazer; it looks quite pleasing as a smoke stack...  Some recycled ciggy packs to mock up a cab - I'm not quite happy with that yet, but to get a rough idea.  I'll only finish the design of the cab once I finished the rest and have the loco running, as I don't want the gas tank and regulator difficult to get to; this engine must be easy to run:


At least, having decided on the smokestack, I set up the boring head in the mill and faced off the end of the copper fitting to conform to the boiler outside diameter - clamped down using a tightish-fitting bit of bar in the bore to prevent the milling vice from flattening it:


While I had the boring head set up and to the correct dimension, I messed around with some hardwood - that will become the boiler mountings:


Utter laziness - milling down wood on the mill  :doh: :lol: :lol: :lol: :


How about a reprieve then? - I used my mitre saw to saw off the needed bits:


Ended up with these - there's a bit of wood that splintered out on the one, and I hadn't noticed until too late :doh: :


With the stack soldered on (I used electronics solder for that), things are starting to look up:


Time to start messing (albeit very carefully and safely!) with the gas supply system...  I haven't been able to find jets as specified locally, and the only gas filler valves I can find comes from these cheap pencil torches:

If only the body where the filler screws into were brass! - Alas, it is aluminium and useless.  The filler uses a thread for which I don't have taps - measured across the thread it's 5.4mm.  The pitch appears to be 0.5mm which is fine.  This leads me to believe this is M5.5x0.5 ??? - so I'll have to make a tap.  I'll play around with the torch first; maybe it's jet will work as well, which will save me the bother of having to make my own or wait for months for delivery from overseas.

 :beer:, Arnold

Offline saw

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Re: A Cracker locomotive
« Reply #59 on: September 03, 2011, 07:20:20 PM »
Nice I just love this project  :drool:
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Offline sbwhart

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Re: A Cracker locomotive
« Reply #60 on: September 04, 2011, 01:53:17 AM »
Looking real well Arnold

You've given me some inspiration to get to work on my loco, I've stripped it down and bin correcting some of the faults that I know its got.

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

Location:- Crewe Cheshire

Offline DaveH

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Re: A Cracker locomotive
« Reply #61 on: September 04, 2011, 03:43:19 PM »
Arnold,

Great stuff, looking really good, coming along nicely. :clap: :clap: :clap:

Nicely photographed and posted again. :thumbup:

 :beer:
DaveH
(Ex Leicester, Thurmaston, Ashby De La Zouch.)

Offline arnoldb

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Re: A Cracker locomotive
« Reply #62 on: September 05, 2011, 01:30:53 PM »
Benni, Stew & Dave - Thanks Gents  :beer:

Stew, I'd love to see you continuing with your loco  :thumbup:

Sunday I spent fixing things around the house, but this weekend we changed to Summer time, and that always leave me feeling like spending time in the shop after work, so this afternoon I did some testing with the pencil torch and bits 'n bobs, not expecting much success.

This is the jet end of the pencil torch, with the burner removed:

It looks like there's a tiny bit of aluminium foil stuck in there with the jet hole punched in it.  The end fits nicely in a bit of 8mm copper pipe though.

I cut a bit of 8mm copper pipe, made an aluminium ring for it to fit in the boiler flue, and crimped the end shut with the vise.  Then I used a junior hacksaw to saw some grooves in it, and drilled a 2mm air hole right through both sides of the pipe at a point just deep enough to allow the jet end of the torch to be pressed in.  I also used a bit of the same copper tube I made the boiler flue from  and cut that to the same length as the flue.  Having read up on other people's attempts at making these poker burners, I fully expected to have to spend a lot of time getting it going, so instead of starting outside of the "flue", I decided to start right from the beginning with the burner in the flue (or simulated flue in this case).  These are the bits I started off with; very crude, but I didn't expect too much for a start:


And all assembled:


then I clamped the "flue" in the vice and started trying to light up...  The first couple of attempts resulted in some big whooshes out the end of the flue, so I decided the gas/air mix was a bit rich, and I started drilling out the air holes in front of the jet - 0.5mm each time.  When the holes were 3mm, the flame flashed back into the tube and started burning at the burner inside the tube.  I even had a bit of control over it by regulating the torch, though the flames were a bit "off-colour".  So I drilled it out to 3.5mm, and ended up with this with the torch set to a very low setting:

A nice bright blue flame with barely a hiss of gas, that I could regulate nicely with the torch valve to full-open and a blue flame licking out of the end of the flue tube - indicating a nice gas/air mixture; I wasn't about to poke my camera in front of that though!

In fact, I'm pleasantly surprised at how well it works and how quickly I got a satisfactory result - so I guess I'll have to go and grab a handful of these torches for their jets and filler valves while the getting's good...
It remains to be seen how it will operate in the boiler with the smokebox and smokestack though; I might have to open the air hole a bit more - or make a ring (like on gas lanterns) to restrict the airflow slightly to adjust the mixture.

 :beer:, Arnold

Offline DaveH

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Re: A Cracker locomotive
« Reply #63 on: September 06, 2011, 01:26:50 PM »
Arnold,
You really do come up with some ingenious  ideas, I would have never thought of using a pencil torch. :scratch:

Everything is coming together nicely. :D

Nicely posted Arnold - a real pleasure looking and reading your posts. :D
 :beer:
DaveH
(Ex Leicester, Thurmaston, Ashby De La Zouch.)

Offline arnoldb

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Re: A Cracker locomotive
« Reply #64 on: September 10, 2011, 05:09:12 PM »
 :beer: - Thanks Dave.  That pencil torch was driving me up the wall anyway, so it's good to find a better use for it.

Some days are just a pleasure in the shop; today was one of those golden days, with everything just going right  :ddb:

First thing up was the tap needed for threading for the filler valve...  I could have single-point turned the thread, but a tap would be convenient, as I have two other boilers that I want to build gas tanks for, and some future projects will also require it.  From other posts and documentation, I know the "standard" Ronson style filler valve uses an M4.5x0.5 thread, but the one in the donor pencil torches is definitely M5.5x0.5.  No matter; I don't have a tap for either anyway.

I chucked up a bit of 6mm oil hardening silver steel, and turned it down to 5.5mm for a length, added a run-out groove with the parting tool, a step on the front that's exactly 5mm diameter, and a gentle taper just by eye using the topslide.  The tap will be used on through-holes, so there's no need to make it in the shape of a plug tap:


Then I set about carefully honing my "small" 60 degree threading toolbit to a really nice sharp tip on an oilstone - using a "fishtail" gauge to make sure I didn't go out of kilter on the angle.  A 0.5mm pitch is a relatively fine thread; the total infeed needed is only 0.25mm / just under 10 thou, and the tool must be really sharp to cut accurately:


I used a rod chucked in the tailstock to set the tool squarely, once again using the fishtail to check:


Then I spent a good half an hour setting up the ML7's change wheels for 0.5mm pitch, and thoroughly cleaned each and every gear tooth and the lathe's leadscrew with a toothbrush before giving it all an even coat of oil.  Fine threads don't like gunk in the drivetrain.  My lathe does not have zero-able dials on it; so I found the total depth of thread reference reading by feeding in till the tool _just_ touched the 5mm section.  I wound the cross slide out and dialled in an ~2 thou cut for the first pass:


Three more passes at 2 thou infeed each followed - with a good amount of cutting fluid applied for each pass.  This sounds like very little, but with the extremely sharp tip needed on the tool, anything more might easily chip off the tip.  On a coarser thread this would not matter much, but on a fine thread, that would mean re-doing everything; it's difficult to pick up a thread properly if one have to re-grind the cutting tool, and all dial readings go out as well.  Fine successive cuts also helps to make a really smooth thread in my limited experience, and that's exactly what I want from a tap. My original depth reading was between 45 and 46 thou on the handwheel - and as close as I could judge it at about 45.75 thou - but that already left a scratch, so for the last two passes I went to 45.5 thou; one to cut and one to finish.  This is what the result looked like:


It's always nice to have a reference to check with; in this case the body of the donor pencil torch, and it screwed on smoothly right away - but more importantly with no free play in the thread at all - just what I wanted:


 :lol: Can anybody tell I love doing single point threading on the lathe ?  :lol: - I'll stop boring you now and get on with things.

I used this setup to mill the tap flutes - it's nice to have a dividing head that can plonk into the mill vise in just seconds:


A bad photo follows; focus was on the chuck and not on the face of the workpiece  :doh: - I milled in the flutes - with the milling cutter cutting about 0.1 mm below the centre line.  This provides some relief on the tap's flutes for cutting, and also allows a bit of sharpening after it's been hardened:


After milling out the flutes, I coated the workpiece liberally in some semi-dried-out dishwashing liquid, and shoved it on a dirty and well-used bit of firebrick that I don't care much about:

The soap makes it easier to get a bit of shine back on the workpiece after hardening it - and more importantly, it provides a bit of protection to the delicate threads by forming a kind of coating when heating things up.

I took that lot, a bucket of used motor oil I have hanging around, a pair of pliers, a fire extinguisher, a leather welding glove and a small blowtorch outside to the driveway leading to my shop.  There I set up things so that I would be up-wind of any fumes, with the fire extinguisher behind me - ready to grab on-the-run.
Why all this boo-hah ? - well, I can't get my hands on water hardening silver steel (drill rod) - so I have to use oil hardening.  I do have some air hardening silver steel, but that always warps, so is pretty much useless for a job like this.  Hardening the workpiece means heating it till it's bright red, and then dunking it in the oil to cool rapidly.  That produces a good bit of potentially highly flammable/explosive smoke - so safety is paramount.  It's not nice getting burnt; I know very well from some non-shop but first-hand (well, both of them in fact  ::) ) experience.
No photos of the process; that's a distraction that I'm not comfortable with, and besides, things get a bit hectic; there's simply no time to take a piccie :).  It goes like this (I'm right-handed):
* Welding glove on right hand, and make sure there are no open or smouldering flames about; not even a pipe/cigarette; this is a no-smoking zone...
* Start torch and with left hand blow flame length-wise across workpiece, moving torch around to get as even heating as possible.  Uneven heating will cause warping.
* With pliers in gloved right hand, rotate workpiece around a bit while heating.
* Next lot must be done very quickly...
* Once workpiece is bright red hot, turn off torch - make sure it's turned off, pick up workpiece with pliers, take a deep breath and hold, then dunk workpiece vertically into the oil at arm's length (with gloved hand).  Once it's submerged, swirl it around a bit.  There will be a lot of smoke coming off for a couple of seconds. When the smoke stops, keep the workpiece swirling under the oil for another 20 second or so - it is still very hot when the smoke stops. Oh, and it's safe to start breathing when you're sure you're not going to breathe in any of the oil fumes.  If anything lights up and start burning, drop everything, make a dash away, grab the fire extinguisher "en passant" (that's why it must be behind you when you start), then at a safe distance turn back and decide what needs to be done. 
* Wipe excess oil of workpiece, and use a file you're not particularly fond of and try to file a bit off the workpiece in a place where it does not matter; I tested with the edge of a half-round file in the thread run-out section of the tap.  If the file just skids over without actually filing out a bit, you've got success.  If it files a bit out, you get to re-do the whole process and you have to be a bit quicker and/or heat the workpiece a bit more than on the first try.  The file skidding off (and actually getting blunted in the process) is an indication that the workpiece hardened correctly.

 ::) If you have access to water hardening silver steel/drill rod - you can fairly safely skip a lot of the previous write-up; just heat it bright red, vertically dunk in water (careful: the steam coming off can scald you) and swirl.  A fire extinguisher behind you is still a good idea though; one never knows  :thumbup:

Now came the hard bit; tempering the tap.  As-hardened previously, it is like glass; it will easily shatter or break if dropped or bent.  The tempering process adds a bit of toughness back to it, at the sacrifice of some of it's hardness.  Tempering means bringing it back up to a certain temperature and quenching again - there's a lot of references available that mentions different temperatures and their associated colours.  There's fancy ways with precision equipment to do all of this, but I don't have any of those, so I went by the book according to older engineering books.  I don't foresee this tap getting used in anything but brass, or maybe bronze, so it does not need to be all that tough - in other words, just lightly tempered.  If its hard, it'll stay sharper for longer.  So I used a bit of Scotch-Brite to shine up as much of the tap tip and shank as I could do easily (this is where that soap I put on earlier really helps).  Then, by just heating the shank with a small flame (NOT on the tapping teeth itself) I could let the heat run through for what I think is the so-called "light straw" colour.  I still used too big a flame, so the heat transferred a bit rapidly, and I was in a near panic to quench it again - this time in water; it does not seem to make too much of a difference if the tempering is done in water compared to oil, as long as the heat is stopped.  In this photo you can see where I stopped it; the tip of the tap and the teeth are yellowish compared to the paper in the background.  The rest is dark blue to black - meaning tough but not hard.  You can click on the photo for a larger image:


I used a diamond needle file to clean up the flute's cutting faces, and ended up with this:

Not pretty, but hopefully effective.

I had to try the tap out, so I turned up a brass bush to silver solder in the gas tank - drilled through at 5mm (tapping size), and 6.5mm to a depth of 2mm to mimic the original pocket on the donor torch.  Then I tried the tap; just chucked up in the tailstock chuck:

 :ddb: :ddb: It works a treat; it actually tapped easier than my shop bought M6x0.5mm taps; no squeaks from the brass, and barely any effort needed to turn the collet chuck - I'm right chuffed with the result  :D :D

And the proof of the pudding; the filler valve screws into the bush easily and accurately:


I ended up making a couple of more bits, and ended with this lot for today:


It will go together like so:


The copper fitting is an ACR grade pipe coupler; rated at a much higher pressure than the original plans call for.  I'll have to do a bit more single-point turning to make an adapter to match up with my pressure gauge to pressure-test the gas tank once soldered up.  I need to make the regulator first as well,as it's body must be silver soldered to the tank as well.

 :beer:, Arnold

Offline sbwhart

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Re: A Cracker locomotive
« Reply #65 on: September 11, 2011, 02:31:10 AM »
Looking good Arnold that tap looks very well done.

 :clap: :clap: :clap: :clap: :clap:

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

Location:- Crewe Cheshire

Offline Stilldrillin

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Re: A Cracker locomotive
« Reply #66 on: September 11, 2011, 04:12:51 AM »
...... "I'm right chuffed with the result" ........  :D :D

So yer should be! What a good day's work. With a satisfying, accurate outcome.   :)

Well done Arnold! I'm really enjoying this gently developing saga......  :clap:  :clap:  :thumbup:

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

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

Offline modeldozer

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Re: A Cracker locomotive
« Reply #67 on: September 11, 2011, 05:58:30 AM »
Thanks for a very thourough expination on treadcutting and making a tap, it is filed for future refferance.   :bow: :bow: :bow:

 :beer:

Abraham


Offline ozzie46

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Re: A Cracker locomotive
« Reply #68 on: September 11, 2011, 08:45:55 AM »


   Well done Arnold. Very nice write up also.
  It seems I learn some thing new each time I check in.  :D :D

 Ron

Offline arnoldb

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Re: A Cracker locomotive
« Reply #69 on: September 11, 2011, 12:36:50 PM »
 :beer: Many thanks Gents.

Today was a bit quiet in the shop... Not much to show as the bit I did was pretty straight forward lathe work.

I started off on the gas regulator body; it needed a couple of different holes drilled into it, with the very last one a very deep 1mm hole - here I have only about 4mm of the drill bit clamped up in the tailstock drill chuck, and the chuck was run in till the jaws very nearly touched the workpiece:


Then I started on the regulator needle; it's supposed to be made from 3mm rod, but I only had some 4mm stainless kicking around, so I turned it down in stages moving the work further out of the chuck between each stage. First the needle tip, then moved out and turned down and threaded M3:

After this photo, there were two more stages of turning down to 3mm to get the correct length.

Then I made the pack nut, and called it a day for today; just 2 hours in the shop, but I had some other things to do.  The finished lot:


 :beer:, Arnold

Offline lazylathe

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Re: A Cracker locomotive
« Reply #70 on: September 11, 2011, 01:30:11 PM »
Very cool work as usual Arnold!!!

Will be following this build to the end!
Is the stoep track ready yet??

Andrew

Offline DaveH

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Re: A Cracker locomotive
« Reply #71 on: September 11, 2011, 02:54:12 PM »
Arnold,

Well you certainly took off this weekend, started with that nicely made tap, finished with an equally nice gas regulator. :thumbup: :clap:

A real pleasure as always Arnold thanks :clap: :clap: :clap:
 :beer:
DaveH




(Ex Leicester, Thurmaston, Ashby De La Zouch.)

Rob.Wilson

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Re: A Cracker locomotive
« Reply #72 on: September 11, 2011, 06:09:32 PM »
Nice going Arnold  :bow: :bow: :bow: :bow: :bow:

Looks like you had a cracking couple of shifts in the shop  :dremel:  ,,,,,,,,,,,,, must be the warmer weather  :lol: :lol: :lol:



Rob

Offline arnoldb

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Re: A Cracker locomotive
« Reply #73 on: September 17, 2011, 01:21:08 PM »
Thanks Andrew  :beer: - the Stoep Track is laid and ready to use; just needs some final fixings and a bit of scenery...  I left the track laying loose through the winter to see what happened at the rail joiners; I expected that the big temperature differences we get here (from 0C in the night to as high as 25C that same day) might wreak havoc with the track shrinking and expanding, and it did.  So there's no way I can actually fix the track down; it'll have to stay loose to allow for the temperature expansions, so I'll most likely just dump some fine gravel down over it as ballast to limit movement while running trains.

 :beer: Thanks Dave.  Like I said, one of those golden shop sessions  :ddb:

Rob, cheers mate  :beer::lol: - We're back to high 20s and low 30s, so I've started to thaw a bit  :lol: - Definitely nicer in the shop now  :thumbup:

Today's little bit...

The gas tank body had to have a hole drilled through for the regulator body - so I clamped it up in the mill using the end caps to prevent the copper tube from collapsing, and a nice thick bit of cardboard to soak up the tiny differences in size between the caps and the pipe.  Then I just plunged an 8mm end mill trough; no need to struggle with drill bits wandering all over the show:


On to a bit of silver soldering...  I fluxed the bits where needed while assembling, and used a fire brick to hold things down.  I set the job slightly over the edge of the bottom fire brick on purpose - using the broken indent on the brick to good effect.  A small ring of silver solder was used around the filler bush right in the bottom; for the rest I decided to stick-feed the solder rather than use rings, as it would have been a complex job trying to make up rings for that lot:

I left the overhang at the bottom to use the fact that silver solder follows the flame's heat; as there was only a partial ring of solder around the bush, it would melt and follow the flame, thus coating and filling the entire joint.  For the cap itself, and the regulator body, I used the flame around the outside and fed the silver solder in on the inside - also using the flame to draw solder into the joints.  Around the regulator body, the solder flowed out nicely to the outside, as the brass bits sticking out into the flame got really nice and hot.

As I was in a bit of a hurry, I gave the workpiece just a very quick pickle, and used a scouring pad to clean up a ring on the inside where the bottom end cap needed to get soldered in.  For the bottom cap, I used a ring of solder - bent so that it was a spring fit in the body, and that the cap would push it into the body when assembling:

Then I fluxed up the ring of solder, and around the outside of the end cap, assembled, turned upside down from the photo, and soldered the lot together.  This was a bit more difficult; I couldn't see what the solder was doing and when it melted, so I had to keep a careful eye out for when the solder flowed trough to the outside - and then had to use the flame to make it follow around the joint.

Gas tank all assembled after more pickle and a bit of rubbing with Scotch-brite:


It's not pressure tested yet...  I had to dig and scratch to find the recommended pressure to test it to; eventually I had a look at the different LP gas cylinders I have around, and nearly all of them was tested to 3000kpa (around 435psi).   :palm: The highest-reading pressure gauge I have is only 1000kpa - so I'll have to invest in another pressure gauge; can only get that on Monday.  Oh well, there's still many bits left to make, and then there's the little matter of a breath-powered Elmer's #46 Coomber Rotary that I have to make before middle October...

 :beer:, Arnold

Offline arnoldb

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Re: A Cracker locomotive
« Reply #74 on: September 18, 2011, 12:37:05 PM »
Some more little bits out of the way...  When an engine nears the running stage there's always a lot of tiny time-consuming bits to make  :lol:

First up was the smokebox door handle.  I went for a round one - just shaped a bit of brass by eye and threaded it to fit the threads I made in the smokebox door:


Then milled some 2mm cut-outs in it on the RT on the mill:

These were followed with a 2mm drill trough each cut-out.

Then I parted it off on the lathe; half-way down first, then used a small file to round the corners, then finished the parting.  As I needed to work on the parted face a bit, I located one of those short bits of off-cut that never seems to be useful as it's too short to really use...:


I chucked the off-cut in the lathe and drilled and tapped it to match the handle-in-making:


Just screwed the handle into it for further work:


Then I hollowed out the front a bit with drills and used a riffler file to try and get a curve in there; not too successful, and not quite what I had in mind, but it'll do for now:


Next up, a bit of 4.7mm thick brass flat marked out and drilled 1.6mm through the width, two 1.6mm holes furthest away through the flat side, and a 2mm and 2.5mm hole respectively nearer in view through the flat side:

All the 1.6mm holes will be tapped 2mm.

A couple of cuts with a 0.5mm slitting saw:


And some tapping, 2mm clearance drill through one side of the top of each bit, and a bit of filing later, I had the bodies of the regulator handles:


Both needed, well, "handles" - so I fashioned some up in the lathe; just by eye; removing most of the material with the toolbits and using a small file to finish off the contours:

To the left, you can see that I used the file to nearly part off the handle; after this photo I just snapped it off by hand and filed the pointy left-over end down.

Then I had a look-see how things fit together so far:

 :bang: The "Cab" is extremely busy, and everything is in something else's way...  I Guess that's what happens when you don't follow plans strictly  :lol:

I mulled things over a bit...  I want both the steam and gas regulator controls easily accessible, and it must be easy to get to the gas filler valve for a refill; this loco will be run often, so ease-of-use and ease-of maintenance gets priority over aesthetics.  I worked out that if I extended the steam regulator handle to the back of the engine, and turned the gas tank 90 degrees from the previous photo so that its regulator handle is at the side of the loco, all controls including the gas filler would be easy to reach, and the pipe work would be minimalist, making things easy to take apart for maintenance.

Extending the steam regulator left me two choices; I could make a complete new needle valve with a longer shaft, or make an extension piece.  I'm lazy, so I opted for the extension piece  :lol:
The easiest and cleanest-looking way to fit it to the existing is by using a steel pin through both; that can then be removed easily if needed, so I turned up the extension from some brass rod, stuck the valve in the end I drilled to fit it, and cross-drilled the lot for a 1mm pin:


A final check, and things look OK - the piping should be fairly easy to do now - both for gas and steam:


 :beer:, Arnold