Author Topic: Elmer Engine Number 14 - Wobble Plate  (Read 31993 times)

Offline propforward

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Re: Elmer Engine Number 14 - Wobble Plate
« Reply #15 on: January 27, 2013, 12:59:29 AM »
Thanks all. All comments, suggestions, hints and tips greatly appreciated.

I spent a little more time on this today, and I shall now show you my triumphs, and point out the screw up. Although I yet hope to recover from the screw up. You'll see what I mean.

So, I started the day off by doing a last little bit of finishing to the cylinder - nothing to much to note there. It simply needed facing to length at each end, and then a chamfer on the ID of the bore at one end, for extra clearance for the con rod.

With that done, I decided to make the piston. Starting with more brass.



I measured the ID of the cylinder bore, and then ever so gradually snuck up on it on the OD of the piston, test fitting the cylinder over it as I went.

Here you can see my sneaking.  ;D



Once the OD was achieved, I needed to make two counterbores, one 1/4" diameter, and another 5/16, to allow for clearance for the con rod. I drilled out most of the material, but finished both counterbores with end mills.



That worked out quite well.

With that done, I added the two oil grooves. I just used a threading bit to make the light cuts.



After parting off, I turned the piston around and cleaned up the end.





I am very happy with how it fits in the bore of the cylinder. It slides very nicely.

Stuart

Forging ahead regardless.

Offline propforward

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Re: Elmer Engine Number 14 - Wobble Plate
« Reply #16 on: January 27, 2013, 01:13:11 AM »
Now, I was going to work on the cylinder head today, but in the end decided to have a go at the con rod.

I started by cutting a piece of 1/4" dia brass rod about 3" long, and put a center drill to it at one end. Then I mounted it in the 3 jaw, and supported the other end with a dead center.



I put a smidge of high temperature grease used for disc brakes on the dead center. Not sure it was necessary, but figured it couldn't hurt either.

Now, I started with a light clean up skim over the whole length to clean up and get the OD concentric, and then focussed on the small diameter.



Gradually taking cuts to get close to the desired diameter, and then taking several very light finish cuts to smooth it out.



After that, I machined the little end down to the right diameter (little end is at the tailstock end)



And now is when I screwed up. I very carefully turned down the diameter past the little end to separate the piece of unwanted support material from the con rod.



It went fine - but the screw up is - I have no way to hold the part to mill the flats and drill the hole through the little end! Gah!  :rant:

I think I can recover from this with this technique - what you can see here is a simple two piece clamp that I made, which allowed me to hold the con rod and clean up the little end.



It does work:



I think I will be able to use such a technique to support the part for adding flats and pivot holes. What I should have done was leave the excess material each end - milled the flats and drilled the holes, and then parted / turned off the excess. You live and learn, but like I say, I think I can recover.

The parts cache as it stands:



Tomorrow - well tomorrow is bloody marys and brunch with my friends, so there won't be any machining tomorrow, but the next session will likely involve the cylinder head I think. I'm going to put off finishing the con rod a bit so that I can mull over the flats and holes and give them my best shot when I'm ready.

 :embarassed:

 :ROFL:
« Last Edit: January 27, 2013, 02:18:54 AM by propforward »
Stuart

Forging ahead regardless.

Offline mklotz

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Re: Elmer Engine Number 14 - Wobble Plate
« Reply #17 on: January 27, 2013, 05:14:38 PM »
A couple of suggestions...

Putting the oil grooves in a piston can raise tiny, almost invisible burrs that increase the effective diameter ever so slightly.  I take the piston down to ten or fifteen thousandths oversize, make the grooves, and then finish cut to size.  Any burrs formed are removed by the final cut.

Making the connecting rod in one piece might be good as an exercise but whenever I encounter such a piece I try to dissect it into separate components and make a fabrication.  That's what I did on my version of this engine.

As you learned, make the flats first.  Drill the hole(s) before disturbing the setup so the holes are perpendicular to the flats.  Then do the turnings.

Have you given any thought to how you are going to fixture the swash plate to solder it to the sleeve to which it attaches?  That gave me the most trouble when I made the engine.
Regards, Marv
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Offline propforward

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Re: Elmer Engine Number 14 - Wobble Plate
« Reply #18 on: January 27, 2013, 09:18:24 PM »
A couple of suggestions...

Putting the oil grooves in a piston can raise tiny, almost invisible burrs that increase the effective diameter ever so slightly.  I take the piston down to ten or fifteen thousandths oversize, make the grooves, and then finish cut to size.  Any burrs formed are removed by the final cut.

Sure enough, when I went to test fit the piston after completion, it no longer fit in the cylinder because of those burrs. Not a big problem to remove, but I should have done it in the order you mentioned here. Now I know for next time, anyway.

Quote
Making the connecting rod in one piece might be good as an exercise but whenever I encounter such a piece I try to dissect it into separate components and make a fabrication.  That's what I did on my version of this engine.

As you learned, make the flats first.  Drill the hole(s) before disturbing the setup so the holes are perpendicular to the flats.  Then do the turnings.

I definitely need to start thinking through the sequence of events more carefully. When I made the flywheel on the last engine, I actually listed out the machining sequence on the white board. I may try that again on more complex components in the future, in writing it down it helps highlight when things may not be sequenced best. However - today I have thought of a scheme that will allow me to mill the flats and drill the holes, and save the part. I will try it tomorrow I hope. However, in future the sequence will be different.

EDIT: This is one reason why this hobby is so much fun. It exercises the brain - it's not just about turning metal.

Quote
Have you given any thought to how you are going to fixture the swash plate to solder it to the sleeve to which it attaches?  That gave me the most trouble when I made the engine.

I have given it some thought, although I wouldnt say I have arrived at a final decision. basically it involves a spacer under one side of the disc, and a weight on top of the hub to hold it down. But I don't want the weight to be a heatsink and make the soldering difficult. So, still working through that idea.

EDIT: What might work, is if I use a clamp - think of a longish arm to apply some pressure to the top (one end) of the hub. Then a spacer under the "high" end of the plate should hold it in the right position - I was careful in turning the hub down so that when the disc is wedged at a tight angle, it is in the right position. I have a few odds and ends of ceramic about, which could go on top of the hub so that whatever arm I use to apply pressure doesn't act as a heat sink. In my minds eye, this arrangement is perfect and flawless, so naturally that makes me suspicious of it. ;)
« Last Edit: January 27, 2013, 09:51:14 PM by propforward »
Stuart

Forging ahead regardless.

Offline mklotz

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Re: Elmer Engine Number 14 - Wobble Plate
« Reply #19 on: January 27, 2013, 10:57:52 PM »
Toldya!   :mischief:  About the burrs I mean.

Yes, machining is far more a mental discipline than it is a physical skill.  It's one of the few hobbies where an advanced case of OCD is a real aid to performance.  You'll learn a great deal about how your mind works (or not) from this hobby.

Think everything about the part through first.  Material selection, single piece or fabrication, how to hold, how to install, etcan. - it's all important, especially so if you're designing on the fly like so many of us do when making jigs, fixtures, tools, and accessories.

You'll soon learn to do this in your mind while performing routine daily chores.  (My favorite is showering but doing dishes or scraping paint works well too.)  Novices should probably start by doing it on paper so they can appreciate in retrospect just how much there is to think about.  For complex jobs everyone, novice or accomplished, should use paper.

I didn't silver solder the swash plate on my engine.  It will never get hot enough, even running on steam, to melt the silver-bearing conventional solder I used.  The engine has seen many running hours and it shows no weakening.

I made a little aluminum (won't stick to solder) jig to hold the plate and the piece to which it attaches.  A small setscrew provided the necessary tilt.  Then I tilted the jig so the swash plate was horizontal (to minimize solder runoff), applied flux and some flux-coated paillons of solder to the joint and blazed away with the torch.
Regards, Marv
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Offline propforward

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Re: Elmer Engine Number 14 - Wobble Plate
« Reply #20 on: January 27, 2013, 11:44:41 PM »
Of course had you told me about the burrs before I made the part instead of afterwards.........;)

No matter Though - not a difficult problem to rectify, but it is more satisfying to get the job done and not have to rectify things. This engine though is proceding with less rectification than the first one, so I take some satisfaction from that.

For the wobble plate assembly I was just going to use tin/lead solder. I think it will do the job well enough. On a job like this I usually wind a piece of solder around the joint before heating, coated with flux, and then heat the joint indirectly with a torch. ie heat top and bottom of collar, and the disc, moving between each until the solder flows, and then that is it. Usually works a treat - it sounds a lot like the method you outlined. I find it best to set the job up entirely this way, rather than heat and try and poke a stick of solder at it, for example, which usually ends up with knocking the parts over and solder running everywhere. I'll take pictures when I do it of course, and we'll see how it all works out.
Stuart

Forging ahead regardless.

Offline zeeprogrammer

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Re: Elmer Engine Number 14 - Wobble Plate
« Reply #21 on: January 28, 2013, 12:20:35 AM »
 :Lol: This thread brings back many memories when I was starting out a few years ago.

You're absolutely right about this hobby exercising the brain. Problem solving. That's a big part of the joy.
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Offline mklotz

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Re: Elmer Engine Number 14 - Wobble Plate
« Reply #22 on: January 28, 2013, 12:32:24 AM »
... and pain.
Regards, Marv
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Offline propforward

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Elmer Engine Number 14 - Wobble Plate
« Reply #23 on: January 28, 2013, 12:36:10 AM »
Yes. Pain. Well - emotional pain anyway. ;D

We try and keep body and soul together of course!
Stuart

Forging ahead regardless.

Offline propforward

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Re: Elmer Engine Number 14 - Wobble Plate
« Reply #24 on: February 02, 2013, 01:59:56 PM »
OK - so I thought I would share my attempts at saving the con rod. It sort of worked out. Sort of. I am undecided as to whether to make the whole thing again or not. As you will see, it certainly needs some clean up, which is no big deal I guess.

What is clear from all this is that I could really use either a mill, or I need to add a vertical slide to the lathe somehow. Short term that may be what I do.

Anyway, here is what I did.

I started by mounting the con rod in the toolpost, in a V cut tool holder, using the split collar I made. I used the other tool holder position to hold a piece of aluminum bar to support the big end of the con rod, and then milled the first flat.





Then I applied some blue to that face, and marked the position of the crank pin hole.



I then drilled that hole.

Then, I rotated the con rod, and used the drill hole to align the rod to the axis of the lathe, to prepare it for milling the second side.



After milling:



Then I flipped the part around to work on the little end.

Again, I used the drilled hole in the big end to get the orientation of the part.





Once the first flat was milled on the little end, I again used the big end hole as a locator, and then used the cross slide to index across the appropriate distance for the hole in the little end, center drilled it, and then through drilled it. Again, I rotated the part around and milled the second side.

It worked out, more or less.



As you can see, the finish is awful, so I will have to clean up with emery and so on, but I will accept that for now. In future I will machine such parts in a more appropriate sequence.

Getting this done was tricky, without a nice fine adjustment to the vertical position, but sometimes you have to make do with what you have - and this did at least get the holes drilled accurately in terms of their spacing relative to each other.

Next up, Cylinder head, which requires the 4 jaw. I made a simple center test indicator bar to help align it.



It's a solid rod - no spring as yet, I will make a nicer one in due course.

I also made progress with the CNC router, and have managed to create programs for it and drive it, so sometime this week I hope to try cutting the side plates for the engine. I still have a few things to work out on that.
Stuart

Forging ahead regardless.

Offline b.lindsey

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Re: Elmer Engine Number 14 - Wobble Plate
« Reply #25 on: February 02, 2013, 02:11:29 PM »
That looks good Prop, given the way you had to go about it. A little clean-up on the flat faces with some  fine emery paper an dyou should be good to go. Keep after it.

Bill

Offline propforward

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Re: Elmer Engine Number 14 - Wobble Plate
« Reply #26 on: February 02, 2013, 02:38:05 PM »
Thanks Bill.

Of course, the little CNC router might be a good tool for this as well, but it has a really limited tool set. If I can spot hole positions though, that might help. Don't know - I'll look into it.
Stuart

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Offline zeeprogrammer

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Re: Elmer Engine Number 14 - Wobble Plate
« Reply #27 on: February 02, 2013, 03:01:16 PM »
Nice save Prop.
Did I hear a 'whew!'?
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Offline propforward

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Re: Elmer Engine Number 14 - Wobble Plate
« Reply #28 on: February 02, 2013, 03:08:45 PM »
Nice save Prop.
Did I hear a 'whew!'?

You did - and a few other interesting expressions too.  :naughty:
Stuart

Forging ahead regardless.

Offline arnoldb

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Re: Elmer Engine Number 14 - Wobble Plate
« Reply #29 on: February 02, 2013, 03:52:51 PM »
Good going Prop  :ThumbsUp:

Ahh... Files and emery - they get to be one's best friends  ;)

Kind regards, Arnold
Building an engine takes Patience, Planning, Preparation and Machining.
Procrastination is nearly the same, but it precludes machining.
Thus, an engine will only be built once the procrastination stops and the machining begins!

 

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