The Craftmans Shop > Model Engineering

Side Valve i.c. engine from Bar stock

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tom osselton:
I hear you! I bought my house in 82 so my butt is staying where it is  I've acumulated too much stuff mind you the basement shop is nice the double car garage is full!   :doh:

Brian Rupnow:
This type of crankshaft, where only one half bears the load from the connecting rod, and the other half simply follows the arc of the first half to drive the ignition points is something entirely new to me. I think that as suggested, the entire crankshaft will be press fit together with no pins or welds. I have found by experimentation that a .002" interference gives a really hard press fit, as hard a fit as I am capable of achieving with my equipment. The only "slip fit" will be where the con rod journal enters the web of the "follower half" of the crankshaft. The con rod journal itself will be hardened to 50-55 Rockwell c so the con rod needle bearings running directly on it will not chew up the surface. In order to get the holes in exactly the same locations in both crankshaft webs, I plan on mig welding the two bars from which the webs will be cut together, then drilling and reaming the holes with undersize reamers while they are clamped to the milling machine table with toe clamps (with a 1/2" piece of sacrificial aluminum between them and the mill table) to ensure that the axis of the holes are 100% square to the face of the bars. I don't trust my vice for this rather critical operation. I will have the thinner of the two bars, which forms the web of the follower crankshaft on top of the stack, so that I can run the undersize rod journal reamer thru both bars, then without changing my set-up run the clearance reamer thru the topmost bar only.--(Picture to follow). I think that in order to ensure that the pushed in shaft sets square to the plates, I will push the shafts thru the flatbar about 1/2", then trim the excess shaft sticking out the far side with my lathe.

Brian Rupnow:
I seem to get more reactions to my posts when I post the actual in progress drawings of the pieces I am making even though these drawings may change somewhat as the pieces are actually made. For that reason I am going to post the drawings marked as "preliminary" purely for interest sake for the remainder of this project. I do not recommend that anyone save these drawings, but instead wait until the end of the project when I will post a download link to all of the corrected drawings.--I will begin by posting drawings of the parts which have already been made.-Brian

Brian Rupnow:
The gears---

Brian Rupnow:
Here you can see my crankshaft web layout on one of the cold rolled steel bars. (There is one extra arc on there that shouldn't be---I had the compass set wrong) I won't be machining from that layout. It is only a visual reference. I will use the edge finder and the dials on the mill table to locate and drill/ream all the holes. You can also see a short bit of mig weld holding the two bars together. There is another weld the same size on the far side. I will drill both bars at the same time, then separate them and trim them, then press them onto their respective shafts and finish the o.d. in the lathe. It will be an interrupted cut, but i don't see any good way to avoid that.

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