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I am in the process of gathering material to build a 4 stroke vertical shaft engine chainsaw mill and really need help on how to attach the chain sprocket to the engine shaft.I had thought to just turn a taper the same as on the sprocket and bolt or weld it to the engine shaft.Any ideas with pictures if possible would help.Thanks
Welding to the crankshaft is not a good idea. A turned adapter should work if you have access to a metal lathe. Is your engine shaft tapered also?
You may want to look at rigging up a jackshaft to speed up the sprocket and chain speed. A chainsaw mill would run between 8-10,000 rpm in the cut and most 4 cycle engines are maxed out at 3600 to 3900 rpm in stock configurations. I would think that you would want to up the speed by 2:1 to get close to the same chain speed. I would think that your rate of speed would be pretty slow. Now maybe your sprocket is much larger in diameter and the bar is set up to match but if you are trying to use stock chainsaw bars and sprockets I think a speed up would help.
You could outfit one end of the jackshaft to be the same as the end of a large chain saw crank ie 090/088/395/3120. You could then mount a clutch system for the saw you duplicated and have access to the rim system for sprockets and spare parts would be readily available. If you want to use larger pitch chain ie 3/4", you can use harvester sprockets that come keyed. But, that would mean a wider kerf.
If you just want to make and adapter get a clutch for a larger chainsaw and weld an undersized hub to the backside of the clutch drum. Then chuck it in the lathe on the splines and bore the hub to size. This should align the bores concentric to the splines for the rim sprocket.
Don
take a look at this site http://www.danzcoinc.com/html/chain_saw_sprockets.html I have been considering the same thing and found the hydraulic motor quite interesting.