- Joined
- Sep 15, 2012
- Messages
- 112
Rohan said:
It doesnt sound like you have a lot of first hand experience rebuilding Norton bottom ends. at least from what you just posted. In my experience, most British twins will benefit from a dynamic balance, I say that because I dont make it mandatory for a Triumph crank, but after my experiences with Norton twins, and the experience of some local experts who have machined and balanced hundreds over several decades, I wont consider rebuilding any Norton twin without a mandatory dynamic balance. Kenny got to the point he was rejecting large amounts of parts that were unsuitable for even sending to the machine shop for refurbishing. Dan Hall, who did over 5 decades of machine work on British Iron here locally grumbled greatly about the difficulty of Balancing Norton twins, and their used to be a lot of shops here in the area who built Nortons.
Rocking couple is usually pretty bad on Norton twins and difficult to address, true the flywheel is centrally located, but unlike Triumphs and BSA its not a full width flywheel, thus its hard to work out weight imbalances, while often times you can grind away on a outboard cheek, or drill to remove mass, there is only so much metal to work with. In about half the Norton twins Ive done we had to add mallory metal in other areas just to get them into spec. In a few cases the cranks were so out of whack I rejected them and started over with another crank. Over the years i worked with 3 dynamic balancing guys. My current guy for the last 15 years Does Airplane propeelors, and Industrial equipment mostly, motorcycles are just a side line but he enjoys it when the Bike cranks come in. When Dan hall did them for me he complained about the Norton cranks because what normally is an hour job can stretch into 2 days, Bearing services just stopped accepting Norton twins, it wasnt cost effective to do them, It was suggested we find another vendor, After Dan Hall died R.I.P the guy who took over 3 years ago sold off the machinery and wont accept any British Bike cranks period. I used to average 15 to 20 engine rebuilds a year for British twins. How many have you done? Im not asking how many cranks you personally turned or balanced, but engines built? Ill admit I personally havent turned any cranks personally for the last 20 years But I did do about 14 of them one year in a machine shop for airplanes, mostly lycoming, some continentals, but always under close supervision of the lead, Aircraft cransk start at $5,000 dollars and go up from there. Crank grinding is an art form, so I wouldnt expect the average person to have any experience, but it IS relevant here how much you really know before you claim some elses points arent valid.
Are you certified in any areas? SAE? NDT? A&P?
By the way, CNC is usually associated with Billet or forgings, I suppose there might be applications where a casting such as a Norton crank might be put ina CNC mill or Lathe. Id be interested if you have any experience in mastercam or programing.
