V11 Bevelbox jollies!

[pete roper]

OK, so I've got my first V11 bevelbox in. The owner bought it in because he was concerned with play in the pinion. This is something I've noted before on some V11's and I just wanted to pick the more experienced folks brains.

 

Drained the oil out and then grab the pinion. When you move it latterally there is a good 15-20 thou, (Nearly 1/2 a mm) of sideways play in the bearings. There is also a smaller amount of fore and aft end float.

 

I couldn't believe this is right. I would of thought that that much latteral play would upset the point of contact so severely that it would destroy the bevels quick-smart?

 

Not having, and not being able to get from the importer, the required castellated spanner for the pinion retaining nut I decided that the safest bet would be to pull off the crownwheel cover, a dead simple job on the new boxes as you can get a pair of screwdrivers under the plate and gently pry it off, much easier than the earlier boxes with their recessed plate! Hooray! Guzzi get something right for a change!!!! The box flange is also now sealed with an O-ring! No more poxy paper gaskets!!!! .

 

Once the flange was off and the crownwheel and box, with pinion still installed, were given a good tub in the parts washer I was able to examine the gears and, surprise,surprise, they were perfect. I was expecting at least evidence of poor mating or damage to the case hardening but they are both, crownwheel and pinion, in superb condition.

 

OK, so the new boxes use a very different system to the old ones. The nose of the pinion is supported in a bearing, this appears to be a needle roller. The splined end is supported in a *special* bearing that I believe is a combined tapered roller and ball race item, presumably the ball race to take lateral and rotational loads, the tapered oller to take the thrust imparted by the helical gears trying to throw themselves apart. There is no means of pre-loading this bearing so one would imagine that the internal tollerances in it would have to be super-critical to avoid the balls being over-taxed with side thrust.

 

What I'd like to know is a.) Is this amount of latteral play normal? b.) Is the theory that the end thrust on the pinion will ensure that the tapered roller will seat and this is what will maintain alignment of the crownwheel and pinion under load? c.) Is this, to me dangerously large amount of latteral play and end float simply a result of the components being cold? Is the play taken up by expansion as the box moves towards standard operating temperatures?

 

Obviously everything is working OK because there is no discernable damage to the gears and the bearings all feel fine with no notchiness or roughness but it all seems seriously shonky to me. I'm NOT and engineer, I'm a mechanic. There may be perfectly good engineering reasons for using this system but I have to admit it all looks a bit cock-arsed to me and I'm *really* not happy about the latteral play in the pinion.

 

Thanks.

 

Pete