The Craftmans Shop > Model Engineering

Side Valve i.c. engine from Bar stock

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Brian Rupnow:
I've heard it said that "Close only counts in horse-shoes and hand grenades." There is one other place that it counts, and that is clearance where the con rod exits a round hole in the bottom of the cylinder. I showed lots of clearance in my 3D cad model when I took a section view thru the center of the engine, but in the case of a rectangular cross section rod exiting thru a round hole in the bottom of the cylinder, it doesn't tell the whole story. If you look at the edge of the con rod, about at the center, you will see how much clearance I DIDN'T have. I thought I felt some resistance when I first rotated the assembled engine by hand, but it was stiff and I was able to get a full rotation after working the crankshaft back and forth a bit rotationaly.  I will file a radius on the corners of the con rod, and that will take care of things. There is no moral to this story, other than the fact that building one of these small engines always has a few surprises in the process. Laying in the picture with the con rod and piston is the newly machined and hardened wrist pin.

awemawson:
Bad luck. Presumably there will be witness marks on the rod where the interference is? Can you perhaps mount it in the 4 jaw and turn the corners off ?

Brian Rupnow:
  I will file a radius on the corners of the con rod, and that will take care of things.

Brian Rupnow:
I am down to the point in my parts making where all that is left is the carburetor, exhaust pipe, and the cooling fan system. I still have a lot of bronze laying around, so decided to make this part today, just because it's do different. Alas, it is not going to happen. Whatever it is about bronze, if the bandsaw blade has any wear on it at all, it simply won't cut bronze. A new blade, it cuts fine.  A slightly used blade, and it just isn't going to happen. The blade still cuts aluminum and steel with no problem but not the bronze. My metal supplier who has a big industrial size self feeding bandsaw and cuts the slices of the 5 or 6" diameter " bronze billet" I have says the same thing about his saw. I would switch to aluminum for the part, but I have to be able to silver solder the fan shroud to it.---Darn!!!

lordedmond:
Brian

You will have to do what I do keep a blade for bronze/brass when it wears then use it for steel same for milling cutters new ones for the two B,s the down to steel

Both things once they have cut steel are NBG for brass

Build is coming along just fine soon be time for some bangs


Stuart

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