Author Topic: PM Research Engine Number 1  (Read 30723 times)

Offline dwulfe

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Re: PM Research Engine Number 1
« Reply #270 on: May 31, 2021, 08:00:22 PM »
If the fastener is plain alloy steel you could "rust it away" with salt water and vinegar. Assuming it broke off in the rod.

Offline propforward

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Re: PM Research Engine Number 1
« Reply #271 on: May 31, 2021, 09:48:25 PM »
Thanks for the suggestion, but the fastener is not an issue.

Alas, the little end is distorted and beyond repair by silver soldering - Iím going to make a new connecting rod.
Stuart

Forging ahead regardless.

Offline propforward

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Re: PM Research Engine Number 1
« Reply #272 on: July 11, 2021, 09:34:43 PM »
Continuing the saga fiasco  :facepalm:  that is this engine, with it's many re made parts, I got some more time on it today. I was going to re make the connecting rod out of bar stock, and figured out an intricate sequence to machine it without marking out, using a rotary table to make various rounded features. I'm pretty sure that would have (or could have) worked, but on a whim I called PM Research and discovered the price of a new casting was six dollars. With brass bar being close to the value of gold, or so it seems, I bought the replacement part. I was pleased to discover that PM Research have been so busy they have had to add more staff just to deal with orders. The nice lady I spoke to was very new, and I was her first foray into supplying spare parts. In the background I heard one of the main people there assuring her that "lot's of people need to buy replacement part one offs". I suppose that reassured me a bit also.

Anyway, here is a sequence of pictures for the sake of it. Made much the same as the last one, although I hope to get the split line in the right place this time.

I have learned to spend a fair amount of time measuring castings and understanding the starting part, so as to think through where the stock is on the part, and understand whether the starting part is symmetrical, or how it relates to the finished part. After that I drew up a machining plan. So first step was getting the thickness of the bosses to size, which involved taking slightly more off one side over the other to try and keep the bolt bosses central.





I then set up a knee (angle plate - we call them knees at work, and I quite enjoy using that term) to hold the part for drilling and tapping the bolt bosses. I aligned it by touching off on the tops and sides of each bolt boss, and tweaking it until they were evened out.



I machined off some of the gate feature - but not all of it. This is a qualifying surface - i.e. one I can use to register in later operations, knowing it is perpendicular to the axis of the part. I also cleaned the tops of the bolt bosses.



Having done that, I established the center of the part by touching off on the sides in both X and Y directions. I spotted the qualified surface just in case that might be useful later on. Then drilled and tapped the bolt holes.



Then I set up an aluminum jig plate that I had used previously to hold the bed casting (sole plate?). I used this piece of aluminium because I had fly cut it previously on both sides, and I knew it was flat and parallel, and also preferred over drilling into the mill table. I suppose I could have used this in the first place and drilled the holes in the part in the same set up as milling the thicknesses. Oh well.





Here I am using the qualified surface to verify squareness to the X and Y axes.



I used a gauge pin to center the little end under the spindle - just done visually to get the zero point.



After that I lightly marked the center of the little and big ends, and performed a quick measurement of the big end to be sure I was central.



After drilling and reaming the two holes, I was pleased to find that a .250 gauge pin would slide in, but a .251 gauge pin would not.



Note: I checked the little end using the actual wrist pin as well, in case I needed to ream slightly over to fit that, but it fit perfectly. Also - the final hole size in the big end will be .375. I have a .25 hole in there right now to aid in set up for slitting the big end. After that is done, and the caps milled to size, then the end cap will be attached and the hole opened up to .375. I probably don't need the .25 hole in place, but I think it may help visually, plus I can touch off on a gauge pin inserted in it when setting up the slitting operation. This is the part I got wrong before (aside from breaking the thing being foolish later on). So - getting there. But that's all for today.

« Last Edit: July 12, 2021, 01:54:43 AM by propforward »
Stuart

Forging ahead regardless.

Offline RReid

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Re: PM Research Engine Number 1
« Reply #273 on: July 12, 2021, 12:32:20 AM »
Lookin' good, Stuart. Glad you're back on track! :ThumbsUp:
Regards,
Ron

Offline Kim

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Re: PM Research Engine Number 1
« Reply #274 on: July 12, 2021, 05:53:39 AM »
Nice work, Stuart!  It's great that you were able to get a replacement casting at such a reasonable price.  Not every place seems to do that!

Kim

Offline propforward

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Re: PM Research Engine Number 1
« Reply #275 on: July 12, 2021, 01:59:45 PM »
PMR are really decent on that. Their stuff is high quality overall too.
Stuart

Forging ahead regardless.

Offline gary.a.ayres

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Re: PM Research Engine Number 1
« Reply #276 on: July 14, 2021, 10:35:15 PM »
Congratulations on getting the connecting rod replaced and getting back on track again Stuart. And only $6 too!

 :ThumbsUp:

Offline propforward

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Re: PM Research Engine Number 1
« Reply #277 on: July 17, 2021, 11:34:58 PM »
Thanks guys for following along. I made some more progress today - and I'm happy to report it really is progress. Fair warning - far more pictures than necessary to describe a simple part, but I was enjoying myself.

Continuing with my step by step second go at the connecting rod, I got it set up on a 2-4-6 block held in the vise to get ready for slitting.

My reference surface was used to indicate the part and get it square for the cutting operation.



Side view shows a piece of the old broken connecting rod being used to pack the upper clamp to stop it twisting off the small clamping surface of the new connecting rod. The gauge pin was used to make sure the pilot hole was above the surface of the 2-4-6 block, in readiness for measurement later.



The gauge pin was also used to locate the slitting saw. I used a piece of paper to feel for a light drag between pin and saw to know I was very close to top of the hole. From that I could easily set the saw height to be right in the middle of the slot of stock material that needs to come out.



Part way through slitting. Remember that the hole is undersize significantly - it is only a reference at this point, which is why the slot looks way off. This is a 1/4" hole, and will be drilled and reamed 3/8" later. After slitting, the top of the connecting rod at the slit, once cleaned up, should pass right through the center of the hole. The slitting saw is 1/32" thick, and the total material to be removed is 1/8", which is why the slot appears above centerline in this picture.



Slit complete





Cleaning up. To understand end mill height, I used a feeler gauge between the end mill and a gauge pin in the partial hole to set the tool height (because it is too easy to chip a carbide tool setting it directly on the gauge pin).





Gauge pin in place just to show that the finished surface is right on the centerline of the hole.



Then added the oil hole while in this set up.



On to the end cap. Similar approach. The remaining amount of pilot hole is used to establish height. The reference surface I set up earlier on provides a very convenient locating surface to get the part square by sitting it on a parallel.



Again - setting tool height using a feeler gauge.



This is part way through cleaning up the mating surface. See how the hole just disappears on the final milling step - which is exactly correct. Means I nailed the height setting.



You can see only the chamfers remain - so I got this right on.



Now clamp it to the connecting rod:



Set it up to drill and tap the oil cup hole. Reference surface again comes in handy.



And again, getting set up for the final big end hole drill and ream op.



After locating the small end hole using a gauge pin and indicator, I lightly spot faced the big end to make sure that visually the spot face was centered.



After that I plunge milled out the half hole, and drilled and reamed the hole to 3/8". I guess I finally got bored of taking pictures because there aren't any more, until after test assembly of the connecting rod in the engine. I didn't take any pictures of slitting the little end either, which was a pretty straightforward job.





Happily, fits really well. The engine has the piston installed, and I can turn the engine over turning the crankshaft with my fingers, so this gives me hope - but at the same time it is not loose and sloppy.

So, finally getting the engine further along.

I enjoyed todays efforts. I take a lot of satisfaction in making parts by indicating features to locate them in space, as opposed to marking out. It's just an approach I like to take, I don't consider it superior to other methods or anything like that, it simply gives me satisfaction.

Anyway, it's time to get serious. I want the flywheel to be the last item made, so now it's time to make gaskets and oil cups, then it will be the flywheel, and then assembly and test.

But now it's Saturday night.

 :wine1:
Stuart

Forging ahead regardless.

Offline Dave Otto

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Re: PM Research Engine Number 1
« Reply #278 on: July 17, 2021, 11:43:46 PM »
Great progress Stuart!

Dave

Offline gary.a.ayres

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Re: PM Research Engine Number 1
« Reply #279 on: July 17, 2021, 11:45:58 PM »
Hey Stuart - nothing wrong with a bunch of pictures! The more the better as far as I'm concerned...

Nice work, resulting in some good progress!

And your Saturday night begins as mine draws to a close...

Enjoy!  :cheers:

gary

Offline propforward

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Re: PM Research Engine Number 1
« Reply #280 on: July 27, 2021, 10:28:24 PM »
I had some fun today making these fiddly little fellows - oil cups. I ground a 45 degree chamfer tool which made short work of these. Not much to them really, although drilling the little through hole takes some care. Otherwise pretty simple - but being so small I am rather pleased with the result.





The inside finish isn't the best - maybe the drill wasn't in the best shape.





Still not too shabby and they look the part well enough.



Not many parts left now. I need to form up the eccentric connecting rod, then it's time for the flywheel, then assembly and test.
Stuart

Forging ahead regardless.

Offline Kim

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Re: PM Research Engine Number 1
« Reply #281 on: July 27, 2021, 11:48:25 PM »
Those are some mighty cute little oilers, Stuart!  Very nice!

Kim

Offline RReid

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Re: PM Research Engine Number 1
« Reply #282 on: July 28, 2021, 12:33:38 AM »
Quote
The inside finish isn't the best - maybe the drill wasn't in the best shape.
The oil won't care. :cheers:
Regards,
Ron

Offline propforward

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Re: PM Research Engine Number 1
« Reply #283 on: July 28, 2021, 01:12:01 AM »
Thanks chaps. Slightly rough hole lower extremity aside, I was pleased that a) I didnít drill the cup ID too deep, b) I didnít break off the small drill, c) the small drill went out through the end of the 2-56 portion, not the side and d) I donít have to make any a second time. So overall - satisfying. Plus my home made cutting tool worked.
Stuart

Forging ahead regardless.

Offline Dave Otto

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Re: PM Research Engine Number 1
« Reply #284 on: July 28, 2021, 01:19:42 AM »
Nicely done!

Dave