Author Topic: Another Halo  (Read 54703 times)

Offline kvom

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Re: Another Halo
« Reply #50 on: October 09, 2009, 09:28:33 PM »
Made the cams:



I turned some brass rod down to .780" and drilled the center hole, then mounted it in the rotary table to mill the rest of the profile and drill the mounting holes.  Then it was back to the lathe to part off two "slices".  Finally I milled the cams to the desired thickness.

Here they are mounted on the driveshaft:



The dimensions given result in a very precise, tight fit.  To get the screws to line up with the taped holes in the shaft I needed to file the center hole slightly to give some wiggle room.  I also think a #43 drill for the mounting holes would be preferable to the #44.

One issue to resolve at assembly time is the angle the crank pin needs relative to the cam lobes.  The cam nearest the end drives the input valve, so I'm guessing that the valve should start to open somewhat just before TDC.  Comments?

Offline CrewCab

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Re: Another Halo
« Reply #51 on: October 10, 2009, 01:46:19 PM »
Excellent work Kirk  :beer:

The flywheel is looking good and nice use of the mill ............... plus Marv's input of course, well done sir  :headbang:

About the Cam's  :scratch: ................... yes. it looks like the inlet valve will begin to open a little over 11o before TDC, however I seem to be missing something in the drawings ............. is there a dimension short ............. how do you locate the intersection of the 20o angle with the .78" diameter, obviously once that is correctly machined the .68" diameter is straightforward to machine  .................. not a criticism by any means Kirk, perhaps just my ageing brain cell's refusing to co-operate .

Again ................. top class work mate  :bow:

CC

Offline kvom

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Re: Another Halo
« Reply #52 on: October 10, 2009, 02:26:39 PM »
The straight sides are .340 from the center, so I move the x-axis +/- .340 plus the radius of the cutter, rotate the table +/- 10 degrees, and cut straight with the y axis.  Then for the .340 radius portion, I set the x-axis to 0, rotab to 0 degrees, and touch the endmill side flutes to the work.  Then in theory I just need to move the y-axis in .050" and rotate the table.  In practice I cut in .045" first and measured the diameter before taking the final cut.

The crank pin can be installed at any angle to the cams.  TDC should occur then the pin is directly below the cylinder's axis, so my question is whether the valve should open before, at, or after TDC?

Offline CrewCab

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Re: Another Halo
« Reply #53 on: October 10, 2009, 02:42:36 PM »
The straight sides are .340 from the center, 

Got it .... (an Eureka moment for my grey matter)......  :med: ............... thanks Kirk, looking forward to the rest  :bow:

CC

bogstandard

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Re: Another Halo
« Reply #54 on: October 10, 2009, 04:48:25 PM »
If you go to here, how to cut the cams on the RT is explained step by step.

http://lineymachine.googlepages.com/halobuildinginformation


Bogs

Offline CrewCab

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Re: Another Halo
« Reply #55 on: October 10, 2009, 04:55:54 PM »
Thanks John, that table of diagrams is just spot on  :thumbup:

CC

Offline kvom

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Re: Another Halo
« Reply #56 on: October 13, 2009, 07:27:54 PM »
After a weekend spent mostly watching the Presidents Cup golf matches on TV and some assorted honey-dos, I spent the afternoon in the shop making a little progress.

The first order of business was to get the bearing retainer finished.  Since I now had a 3/8 under reamer, I mounted the piece in the lathe and reamed the center hole to .374.  Then I parted off the part and spend some time cleaning up the mounting holes; the tapping stand was useful for this.  Then there was the obligatory trial fit:



Looks as if I need a deeper countersink for the screws, and some filing to make the spokes a bit nicer.  I did a quick test of the bearing supplied by Liney, and it looks as if it will be a nice fit - not loose but not terribly tight either.

Not being overly ambitious, I decided to just make the rocker pins.  Although these are pretty darn simple, they were tedious to make with lots of ins and outs on the collet chuck.  First, hacksaw off 5 pieces of 1/8" brass rod a bit longer than the finish length; next face all 10 ends to get accurate length measurement.  Then face off to final length.  Now I needed to center drill each end, as I was not sure that I would get a straight hole drilling through from one end.  So I drilled halfway, then turned around and drilled through from the other side.  The final operation was threading each end, using the bushing I made to fit the tapping chuck.  So I probably spent two hours just to make these 5 small, simple parts.


Offline kvom

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Re: Another Halo
« Reply #57 on: October 16, 2009, 07:42:43 PM »
More shop time making little fiddly parts the past few days.

Since I obtained my O/U reamers, I reamed the cross hole of the rocker bracket and inserted the rocker pins.  Not a press fit, but I suppose brass rod isn't necessarily on size.



Next I started on the rocker arms.  I first took a 6x6" piece of 1/4" aluminum plate and cut off as slice  that I machined to 1" wide.  I then milled the profile of the arms.  The sides of the center section were milled with a 1/8" ballend endmill to obtain the rounded corner profile.  I then used a 1/4" endmill to slice off 10 pieces.  At the end of the cut the pieces would snap off leaving a large burr that would need to be milled off later.



The next machining steps required the use of soft jaws on my Kurt vise, as both the rockers and the connecting rods to follow are 1/8" thick.  After mounting the jaws, I milled off the existing slot with a 1/8" endmill to get a flat starting point.  Then I clamped a 6" rule between the jaws to allow clamping room later, located the center of the slot with the edge finder, and milled a 3/32" deep slot with a 1/8" endmill.



After positioning a vise stop and locating the x-axis with the edge finder, I was able to mill off the burr from each piece, and then drill the vertical hole that will accept the pushrod:



The same setup was used to spot drill, drill, and ream the cross hole for the rocker pin.



Finally, I cut four pieces of 1/8" square brass rod (using a wire cutter is quicker than hacksawing), and used the same vise slots to mill to length, drill the cross holes, and finally mill the slot in the end (1/16" endmill):



For those who haven't tried soft jaws and have a vise with removable hard jaws, I can recommend them for holding thin pieces where parallels are impractical.  Note that you can drill into the jaws through the pieces, which is not a good idea with hard jaws.

Offline NickG

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Re: Another Halo
« Reply #58 on: October 17, 2009, 04:47:06 AM »
Wow Kirk, you're marching on ahead with this one! Looking great  :bow:
Location: County Durham (North East England)

Offline kvom

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Re: Another Halo
« Reply #59 on: October 17, 2009, 08:21:12 AM »
One of these days I need to get my nerve up and cut the fins on the cylinders as per Bogs' recipe.   ::)

bogstandard

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Re: Another Halo
« Reply #60 on: October 17, 2009, 09:36:48 AM »
Why did you think I did those cylinders first?

Always do the difficult bits first. If you can get those finished, then it is all downhill for the rest of the build.

That is why so many builds end up under the bench. They do the easy bits first, then when they come to the hard, they have had enough and just give up on it.


Bogs


BTW, I hope you made a few spares.

Offline Darren

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Re: Another Halo
« Reply #61 on: October 17, 2009, 10:11:07 AM »
You are a bugger John ..... make him feel good eh ....  :med:
You will find it a distinct help… if you know and look as if you know what you are doing. (IRS training manual)

bogstandard

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Re: Another Halo
« Reply #62 on: October 17, 2009, 12:14:44 PM »
Darren,

I explained all about getting the hard bits out of the way on my Halo post. Also, I have yet to see on any of the Paddleducks engine builds, one with the steam control valve fitted and working. Maybe because that is one of the most difficult parts to make. It just so happens that it has to come at the end because other components are required to build it. So once it has had it's initial run on air, without the controller, they seem to be forgotten about.

If Kirk gets the message and has only made just enough cylinders, he will do a bit of practicing first on bits of bar. Then when confident about the result, go for it.
I started out with 23 I think, and lost two on the journey. That is an attrition rate of 10%, and I am experienced in making things like that. Kirk needs to get the practice in first, not only in cutting the grooves, but grinding up the tools to do the job.

Hence the warning.


John


Offline Darren

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Re: Another Halo
« Reply #63 on: October 17, 2009, 12:44:27 PM »
Tis OK John, I knew exactly where you were coming from ....  :thumbup:
You will find it a distinct help… if you know and look as if you know what you are doing. (IRS training manual)

Offline kvom

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Re: Another Halo
« Reply #64 on: October 17, 2009, 01:18:53 PM »
Quote
practicing first on bits of bar
 That is my plan, as it happens.  :headbang:  I didn't make a spare cylinder;  I decided that I would not gain any efficiency in making extras as it would take me as long to make a replacement as a spare.  Given John's procedure for truing the tool, there is really no reason that cutting the fins should be an issue.  (knocking on wood as I type this).

Once I get the master rod made (current work item, that for me in one of the harder pieces), I will need to suck up and finish the cylinders.  I don't want to make a piston for a cylinder that needs a do-over.

As for the paddleducks build, I ran out of solder and am waiting for my order to arrive to finish the valve.  For me, at least this far, the machining/fabricating work is more "fun" than the debugging.  However, I promised myself not to start another build after the halo before I get the paddleducks working with the valve and some bling done too.
« Last Edit: October 17, 2009, 01:22:32 PM by kvom »

bogstandard

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Re: Another Halo
« Reply #65 on: October 17, 2009, 05:54:29 PM »
Kirk,

I wasn't  :poke: you specifically, it was just a comment about what is happening with the Paddleducks engines.

It is my fault really, for doing a difficult piece at the very end. But that is the only way it could be done, to accurately make it physically fit the engine.

Bogs

Offline ozzie46

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Re: Another Halo
« Reply #66 on: October 17, 2009, 09:19:25 PM »
Darren,

 I have yet to see on any of the Paddleducks engine builds, one with the steam control valve fitted and working.
John



    Ok John,  here it is.




   I didn't find the control valve all that difficult to build.  :dremel: Just a little bit time consuming to get the spool to length , took me about half an hour.  Then again maybe I got lucky.   :D

  Sorry about the quality of the video. I'm still not to versed on them yet.

   Ron

bogstandard

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Re: Another Halo
« Reply #67 on: October 18, 2009, 01:49:38 AM »
Absolutely wonderful Ron, you have just made my day.

Many thanks for showing it to us.

Another first.


John

Offline kvom

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Re: Another Halo
« Reply #68 on: October 18, 2009, 01:06:54 PM »
Yesterday and today I worked on the most challenging part thus far, the master rod.  Because of the irregular shape I figured I needed a jig to hold it.  First I reduced a small piece of 1/4" brass to .375" wide by 1.25" long and drilled the holes needed for the wrist and crank pins.  After reaming the crank pin hole, I machined it to 1/16" thickness.

For the jig, I found a 3" diameter disc of aluminum about 3/4" thick.  I turned one side for a 1" diameter spigot that would mount on the rotab, and then turned the other side with a small .125" spigot that would be a tight fit for the crank pin hole.  Once mounted on the rotab and centered under the spindle, I set the rotab to 0 degrees and drilled a .063" hole .850" from the center.  I then could mount the workpiece on the center spigot and hold it laterally with a piece of 1/16" drill rod.  I then drilled the 4 holes to which the other connecting rods will be pinned:



Next using a 1/8" endmill I tried to carefully machine the profile using a combination of linear and rotary motions.  Unfortunately it seems I had a slight undercut on one side.



I trimmed the tail to length leaving a workable, although less than perfect, master rod.



Some lessons I learned.  I had intended to drill and tap a hole in the tail as a hold-down (for that reason it was left long).  When I first mounted it on the jig it was very solid, so I neglected that step.  On a do-over I would do so as the piece did have a tendancy to lift when milling the tail portion.  Rather than the spigot in the center of the jig, I would just drill a hole and insert some 1/8" drill rod. 

If, like John, I needed to make multiples, I would sandwich all of the pieces and drill/mill all at the same time.   I think using a larger endmill and calculating the toolpath for a single cut of the entire profile would be better than the incremental milling I used.  I'll be interested in seeing how John approaches this part.  I don't really see the need to shape the head as the plan shows unles I find some binding with the rod ends once assembled.

bogstandard

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Re: Another Halo
« Reply #69 on: October 18, 2009, 02:59:46 PM »
Kirk,

I will only be able to make two the same, all the rest will be different.


John

Offline kvom

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Re: Another Halo
« Reply #70 on: October 18, 2009, 05:54:41 PM »
Quote
I will only be able to make two the same, all the rest will be different.

That's true - different number of holes for the conn rods.

And since John goaded me into action:

Since my house was invaded this afternoon by 7-8 teenagers at the invitation of my daughters, I decided to hide out in the shop.  It was finally time to turn the fins in the cylinders, as they had been waiting since 9/28 to be finished up.  Bogstandard has a fine writeup on setting up the very thin parting tool (.025", no relief), and I followed it pretty much as written.  Since the tool needed a surface grinder to create, others attempting this build might choose to use a wider, commercial tool and cut fewer fins (or no fins at all).  I was able to chuck the parts in my Jacobs Rubberflex collet chuck, and the cuts were surprisingly easy. 

Like Bogs I had written down a list of X-Y coords for each cut, and it took only about an hour or so for all 5.  Having a DRO on the lathe makes this a much easier proposition.  Then I reversed them in the chuck to cut down the bottom spigot to length.  One thing I did differently was using a 1/16" parting tool to turn down the three bottom fins; this avoided the thin wires that would result from using the thinner tool.



My list of to-do parts is getting smaller.  I still need to drill the many, many holes in the heads and make the 5 pistons, and then I can think about some assembly, a base for mounting, and some sort of air manifold.

bogstandard

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Re: Another Halo
« Reply #71 on: October 18, 2009, 08:03:12 PM »
Nicely done Kirk.

DRO's and surface grinders do make life a lot easier when doing a job like this.

I do still have the extra tools I ground up for doing the finning job, so if anyone wants to build one of these engines, and doesn't think they could grind up a tool to do the job, I am sure that one could find it's way to you.


Bogs

Offline kvom

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Re: Another Halo
« Reply #72 on: October 18, 2009, 10:30:30 PM »
I could send mine to someone on this side too.

Offline kvom

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Re: Another Halo
« Reply #73 on: October 21, 2009, 11:45:17 AM »
I started drilling holes in the remade heads yesterday, and "sacrificed" the first one.  Once again the valve holes presented the problem.  The drawings specify the depth to cut, but show a flat bottom hole.  The first holes I drilled I used the points to set the depths, but doing this the valve ball sits too high for the plunger to contact.  So I reset both the initial hole and counter bore to not count the point.  The first hole then goes into the side mounting holes.  This is probably not an issue, but it's also possible I don't need that full .4" depth anyway.   A bigger problem was that the counterbore was probably a 1-2 thou. too deep and intersected the plunger hole; I think this would make the valve leak.  So I now believe the solution is to use an endmill in order to achieve a flat counterbore.  The plan specifies .200 counterbore.  A 3/16" endmill followed by a #8 reamer should work.

I'm out of town the rest of the week, so I'll try it next week.

Of course, all of this is of little interest unless you're planning to build this one too.   :coffee:

Offline kvom

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Re: Another Halo
« Reply #74 on: October 21, 2009, 10:08:31 PM »
I had a little more shop time before leaving for the long weekend, so I "caught up" on some tapping.  This model needs a lot of tapped holes.  Each of the 5 cylinders and their attached parts total 20 2-56 holes.   Without the tapping stand I made a short while ago this would have been mission impossible.