The Craftmans Shop > Model Engineering

Side Valve i.c. engine from Bar stock

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Brian Rupnow:
Gentlemen--Thank you for your replies. I was looking at my engine collection this morning, and it seems that my Atkinson engine has .093 slots between the fins and the slots are 3/8" deep. I don't remember having any particular problems with that cylinder, and I machined it dry. I will machine this new cylinder dry and hope for the best. Philf--I did buy a .093" slitting saw, in case I ran into any problem with the cylinder machining, and because the part directly above the cylinder along with the cylinder head have a number of the same size slot, and they can not be turned. I couldn't imagine the time it would take to do these with a 3/32" endmill, so I have the slitting saw in reserve.---Brian

Brian Rupnow:
Made a mistake. Kissed a snake. How many cooling fins did I make??--Well okay, maybe you're not into skipping rhymes!!! However, if you are paying attention, you will see that I have one more cooling fin on there than the drawing calls for. To make it even worse, the top 3 cooling fins are skinny little devils, while the bottom 3 are full size. I have absolutely no excuse for it, other than encroaching old age and gross incompetence. By the time I noticed that the first cooling fin down from the top was too skinny, I had already advanced the tool .040" into the work, and there was no good way to hide it or cover it up. I'm still a bit baffled as to exactly what happened, but somewhere in there, the math let me down. At any rate, I have convinced myself that since this is a prototype, it really doesn't matter that much. The cylinder will still function just as well with one extra cooling fin. Everything seems to bolt together okay, although I did have to use a ball end hex wrench to tighten up the bolts holding the cylinder to the crankcase.---Probably would have had to do that even without the extra cooling fin. And for my next amazing stunt---I will be making the combustion chamber that mounts on top of the cylinder.---And, Oh yeah---I machined the cylinder dry, and there was absolutely no binding, galling, or "scare the crap out of me cut off tool breaking".

Brian Rupnow:
This is the part I will build next. I will probably mess with the cooling fin spacing a bit so it matches my miss-machined cylinder cooling fins.

tekfab:
Hi Brian, I'm too late getting here but if you have to do any similar fin cutting in cast iron we always used a compressed air jet to keep the cut clear and also cool the tool down always assuming you have access to a compressed air source.
Keep up the good work  !

Mike Young

Brian Rupnow:
Tekfab--Thanks for having a look and posting a comment. I do have compressed air in my shop, and as I said on one of the other forums I post on, it is a good solution but makes an awful mess of a small home shop. Another good solution is to rig a holder for the shop vac nozzle so it follows the cutting tool. Accomplishes the same thing but without the mess of cast iron dust blown all around the shop. Actually, I cut that cylinder dry with no compressed air or vacuum and didn't experience any problems.---Brian

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