Milling the main frame on the PMR #2A engine.

[Twmaster]

I'm still a wet-behind-the-ears metal man. I've had my mill for about 2 months now and am still learning how to do things.

I just received my PM Research model #2A engine. While looking at the main chassis casting and deciding what order to do things in I'm trying to determine which way I should start this as to not bollux it up from the git-go.

What I am thinking to do is jig it up on my mill table to make the back of the casting as close to level as possible. Then machine the three surfaces that need to be in plane with each other. I figure once I've done that I can mill the bottom of the mounting feet and top of the casting perpendicular to the planed surfaces as well as to the specified height. This all can be done without disturbing the setup on the table.

Is my thinking correct here or an I making this too hard or missing a step?

 

[zeeprogrammer]

I got the video that's available for the kit (at extra cost) but, for the life of me, I can't find it. If I remember it correctly, then you're basically right.

As you said, mount the mast horizontally and mill the 3 surfaces and the feet. This is what you need in order to stand it up and use a height gauge to scribe the crankshaft hole, pivot hole, and the four holes that intersect the inlet and exhaust holes.

I don't think it's necessary to mill the top yet. When you need to drill and tap the inlet and exhaust holes you can shave off the top then. total height is not critical.

Two of the tricky parts for me was 1) getting the part level sideways when scribing it and 2) mounting it at an angle on the mill for drilling and tapping the set screw hole. A combination level was handy for this.

This was my very first engine and machining attempt so I was learning everything as I went. As for the video...it was very helpful along with this forum. But the author either ran out of time or interest as it ended somewhat abruptly. Kind of went from slow and easy pace to suddenly being assembled.

Hm...I wonder if that video is still in the VCR?

 

[ChooChooMike]

I recommend watching the video Good instruction on how to work the frame casting and other parts of the engine. Also a good intro to using Sherline's mill/lathe.

As for the video...it was very helpful along with this forum. But the author either ran out of time or interest as it ended somewhat abruptly. Kind of went from slow and easy pace to suddenly being assembled.

Ya know, now that I think of it, I have to agree with that comment. It's been a couple of years since I watched the video, but do remember it starting out showing lots of details on machining the frame casting, and then kind of jumping ahead to boring the cylinder on the lathe and then to the finished engine. No details on the rest of connecting rod, crank, break-in. etc.

Mike

 

[Twmaster]

Thanks for the input folks. It's unlikely I will buy the video. I have other things my $25 would be well spent on. Like tools.... Need to buy a 5-40 tap/die.

Part of the allure of working with this gear is learning how by having to think about procedures. Learning by being shown how is also good but I've always been a bit hard headed....

 

[bearcar1]

That video is a horrible video in my opinion. It really does not walk the beginner through the steps in detail enough. It merely shows about a dozen times, the process for center drilling and then drilling the holes. (after the first time, BORING) As it has been stated, it goes along WAY too slowly in the beginning and the next thing you know, its built. Quite a bit more thought could have been done in how this video was put together. Now that I have that said, yes, TW, you are on the right track in machining the base casting.

BC1
Jim