Postby LaceyDucati » Sun Nov 12, 2023 6:39 pm
Hi Colin,
Are the bevels matched? Some Spanish bevels I've seen do have the ground marks and most other Spanish matched sets have numbers on them (same on each gear)
They could be worn from being set incorrectly, but it's not unusual to find an element of run out on gears (even on new unused gears). Basically some of the manufacture leaves a bit to be desired and I don't think I've ever had a set of bevels that don't vary in clearance throughout the rotations. If the gear head is not true to the bore then the contact patch will always have a tendency to move about... Of course any run out in the crank will also have an effect, however your crank was good.
All you can do is observe what is going on overall and go for the best compromise of contact. If they are unmatched then they may never sit together or work as a set. For any setting up I arrange the gears so they are oil free and can be spun freely. That is rockers out and bottom crank bevel removed for the top set and no top end, piston, alternator or primaries for the bottom set. Only like this can you feel what is going on. For clearance I spin through the rotation from dots lining up to dots lining up and find the tightest spot. This I do by turning the gears and "rattling" the pair in various small increments and when I've found that tight spot I mark it with a marker pen. I will then shim the clearance to this point so there is no perceptible clearance but at no point can anything be heard or felt, indicating a tight spot. Any other clearance around the travel I then live with. I will say at this point everything will need to be fully tightened, bevel nuts, flange and tunnel screws. Otherwise when you do the final tightening the clearance will alter. That will also include the bevel circlip being fully shimmed snugly and the head bolts fully torqued for the top set. When you are down to the final setting all these things will make a difference, mainly resulting in tight gears. Running tight gears will lead to wear.
In an ideal world the teeth should "cup" into each other centrally, but sometimes you just have to compromise. However if the gears are spun and they are unusually noisy or feel rough then most likely you will need to find some more gears. You can usually see where the gears have been running and that may help when using blue.....that's assuming they were acceptable/somewhere close to start with. Unfortunately setting bevels well can be a very long winded and frustrating game and even with experience it can take many hours.
Regarding grinding down early bevel gears for use in the later widecases, I do it in a cutter grinder, but you could use either a cylindrical grinder or a tool post grinder on a lathe as has been mentioned. It doesn't have to be that accurate but doing it by hand would be a risky game..... Anyone in the UK who wants a set ground down I can help with that. Although you do lose the close ground marks at the tooth edge, you can generally still use a ruler across them and see the match okay. Once all is good with an unmatched set then making you own "ground" marks is a good plan for the future....but then you will need to mask everything and then strip and wash everything before final assembly. I think you may be getting the idea of the value of a good set of matched gears!
Hope some of that helps
Regards Nigel
