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| Joe in Oz:
I strongly agree with Manxmodder: taper rollers are wrong for this application. Best would be barrel rollers on the drive side (or both), deep groove on the non-drive side.... Taper roller bearings need to be preloaded to meet their design parameters - and you can't do that with a crankshaft since you introduce bending forces on the crankpin if you did. Cheers and enthusiastically anticipating the build log! Joe |
| John Stevenson:
Sorry but I disagree about the taper rollers. In theory what you say *may* be correct but Velocette's used taper rollers all thru the production life of their later series of machines with no problems. You assembled the engine cold with an 8 thou gap between the crankcases so that was the preload |
| billmac:
Just to add to what John has said about Velocette bottom ends. The design resulted in a rather narrow bottom end which raises its stiffness significantly. This is a big advantage in a high performance single (or even more so a V twin) , because it reduces the deflection in the mainshafts and crankpin and tends to produce a smoother running engine. In the case of the Velocette it also allowed the unusual arrangement of the clutch and final drive sprocket, which are quite different to any other similar machine. I seem to recall that Joe Craig of Norton fame believed that the Velocette bottom end was a better design than his Manx Nortons, although he didn't have the same high opinion of the rest of the engine. I can't find a quote for that so maybe my memory is faulty, but in any case I think the OPs design is interesting and if the crankcase is made strong enough will result in a great engine. |
| vtsteam:
Already a great read! Learning a lot. |
| OKTomT:
Thanks for all the input. I do appreciate you taking the time to post your opinion. Frank the flywheels are 1018 and the pins 1045 ground and polished. this will work for me but I am sure there is a better material. Getting the crankshaft to run true is quite a challenge for me. I would like to know how you would contain the rod pin and how you would machine the fit in the flywheels. The main pins are tapered at 3* and run true with the fly wheels but rod pin is off by .030 tir. I bored and cut the taper for the main pins in the lathe then put the flywheels in the mill and bored the rod pin fit. One of them was bored for a press fit and the other was left under size and put back in the lathe and the taper cut. I think there must be a better way. On the last engine I put a 3 jaw self centering chuck in my 4 jaw chuck and set it off center to bore and taper the rod pin holes but the finish was bad due to the slow speed I had to use. Thanks Tom |
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