AOG's version of the PM -3A engine

[AOG]

I've got that itch again so it's time to get started on another project. This will be my second engine from a casting kit so I wanted something that wouldn't be that hard. I decided on the PM Research 3A.



(Image from the PM models site)

Let's get started. First I leveled base casting in the vise using adjustable parallels. Then I milled the bottom flat.



With the bottom flat I flipped over the base casting and faced the mounting pads. Then I drilled the pads for 4-40 mounting hardware.



Next I squared up a piece of flat plate, transfer drilled and tapped the holes from the base. The casting shifted slightly so one of the holes is off. Three mounting screws is enough for what I need to do.



With the base casting mounted on the tooling plate I marked out the center height of the piston on the bearings and cross head. Then the part was placed in the vise to take advantage of its squareness and rigidity. Then I flattened the face where the cylinder will mate to the base casting.



Next I drilled and reamed the hole in the base that the piston rod passes through.



With the same setup I used the DRO to layout and drill the cylinder mounting holes. This particular operation almost got me. The three holes are no equidistant from each other. Two of the holes are only 90 degrees apart instead of 120 degrees apart. Thankfully I caught it before I drilled the holes.



Then I rotated the part and milled the lower cross head guide to dimension.



Next the part was rotated again and the rest of the cross head taken to dimension and the mounting holes drilled and tapped.



Following that the piece was rotated again and the holes for the crankshaft were drilled and reamed.



Then the tops of he bearing journals were spot faced, drilled and tapped for oil cups.



Here is the finished part with the oil cups installed.



Till next time

Tony





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[b.lindsey]

Very nice Tony, you have already got some of the hardest parts done!!  Looking forward to the next installment.

Bill

[Flyboy Jim]

Looks like a good start Tony.

I'm guessing the #3A means it's the aluminum version. That looks like the only kit they have that has an aluminum version besides the #2.

I wish there were others.

Jim

[Don1966]

Great start Tony and will be following you.....

Don

[Tennessee Whiskey]

I like the way you keep things rolling Tony  . I agree with Jim, after cleaning up behind C/I, ali would be nice.

Cletus

[AOG]

Time for round 2, making the cylinder. I started by facing one side flat.



That gave my a flat side to put against the chuck. Then I machined the other side. I left the part 10 thousands oversized to allow a facing cut with the boring bar to ensure  that the face is parallel to the bore. Then the hole was drilled out to accept my boring bar.



The cylinder was then bored to size and the facing cut made.



Then the bore was lapped with some timesaver.



The part was flipped and the cylinder taken to final length.



The cylinder was taken to the mill and boss for drilling the valve ports was flattened and leveled. This will be one of my reference faces.



Since I was setup for it I drilled the straight ports. Drilling them first means that I don't have to worry about breaking into the valve hole and leaving burrs.



The cylinder was rotated to put the boss against the fixed jaw. The center of the bore was located and set as the zero reference. Then the valve hole was drilled and reamed.



Next I counterbored the port face at the cylinder.



The last thing on that side was to drill and tap the mounting holes for the cover.



The part was then reversed and the port face was counterbored and the mounting holes drilled and tapped.



The next operation was the one that always make me nervous. I drilled the angled port between the face and the vertical ports. I was quite relieved when it went well.



The last operation was to spot face, drill and tap the intake port.



I'll end this with the current family shot (such as it is).



Till next time.

Tony


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[crueby]

Lot of work in that sequence, very nicely done!

[AOG]

I got some more shop time this week so here are the results. The next part made was the bottom cylinder cover. I used a bump center to center the part in the three jaw and cleaned up one face of the part.



Then I drilled and tapped the hole for the piston rod.



Then the part was flipped and put in a collet chuck. The outer edge was cleaned up and the center boss cut.



Then the collet was transferred to a collet block and the mounting holes were drilled.



Next up was the top cover

The three jaw was installed and the cover was bump centered to get it running true. Then the center boss was cut.



The part was flipped and installed in the collet chuck. The diameter was then taken to size.



Then over to the mill where the mounting holes were drilled.



With the covers done it was time to make the piston. The blank was turned to size and the ring grooves cut.



Then the center was drilled and counterbored.



The piston was parted off and the piston rod made by turning and threading both sides of the rod stock to the correct size.



Then I assembled everything for an alignment check.



That's it for now

Tony


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[b.lindsey]

You are making rapid progress Tony. The parts all look very nice so far. IN the last picture, what is that on the near side crankshaft bearing and down the side of the frame?

Bill

[AOG]

Bill, that's a piece of plastic that I was using to keep from dropping a screw into the cavity below the crosshead. It looks like I forgot remove it all the way before I took the picture. 

Tony

[b.lindsey]

I figured something like that. The engine is looking  great though.

Bill

[AOG]

Thanks Bill

Tony

[Flyboy Jim]

Looking good Tony.

Lots of similar parts to your and my PMR 2's.

Jim

[AOG]

I was thinking the same thing. Everything I learned doing the 2 has been directly applicable. The biggest changes are the base and piston valve. Drilling the valve ports is a very hairy operation.

Tony

[Don1966]

Making good time Tony and she's looking good.....

Don