- Tue Jul 10, 2012 2:50 pm
#14604
Hi Jonny. Velocette chose taper bearing as they were impressed by the low wear rate they seemed to achieve and they stood up to the side thrust created by the helical cam gears.. Initially SKF advised them to use self aligning taper bearings but due to assembly problems tried to use ordinary taper bearings. Unfortunately as the crankcases heated up the expansion created slop in the bearings with too much end float so Velocette opted to preload the bearings at cold temperature so when at running temperature the end float was just right as the crankcases expanded and relaxed the tightness. Taper bearings were never designed to run with this amount of pre load but this is only maintained for a fairly short time. Even expert engine builders find setting the preload difficult and with too much, there are many cases where the bearing has been pushed through the crankcase wall. Some engines have been modified to use “top-hat†inserts to spread the side thrust on the bearing housings. Quite a few owners now use high quality conventional roller bearings rather than taper bearings in the Venom motor!...So it would not seem a good idea or have any advantage to fit taper bearings in a Bullet motor. The Bullet engine does have the advantage and strength of a roller bearing on the timing side…many British singles only have a bronze bush. You need to keep the 6305 ball bearing on the outer drive to give the crankshaft some positive alignment for end float but you might be able to get a “maximum capacity†type bearing for this position which is a bearing fitted with an extra two or three balls to increase it’s load capabilities. Whether self aligning roller bearings that have barrel shaped rollers (Called Superblend in Norton parlance) that can now be bought would be an improvement I don’t know but they are usually very expensive. You will have to do some searching or phoning the bearing stockists to find out
