Lower bevel gear spindle shimming - Darmah

Post your general FAQs, comments & questions regarding all Ducati engine & transmission restoration here. [Specific engine FAQs should go in the 'BevelHeaven Garage' section.]
Post Reply
andybaggies
Cucciolo - the Lil Pup
Posts: 4
Joined: Thu Nov 01, 2018 11:52 am

Lower bevel gear spindle shimming - Darmah

Post by andybaggies » Mon Nov 05, 2018 3:49 am

Can someone confirm exactly where shims are required on the lower bevel gear spindles ? e.g.

i) between the bearing mounting plate & the’front’ of the pinion/bevel gear cluster.
ii) between the pinion and bevel gears themselves (???).
iii) between the ‘back’ of the pinion/bevel gear cluster and the raised ‘lip’ on the spindle.
iv) between the ‘back’ of the spindle and the bush in the casing.

The reason I ask is because during strip down I noticed one of these spindles can be moved in and out by ~1mm or so. The ‘float’ is between the back casing and the pinion/bevel gear cluster and this is with timing marks aligned and the bearing mounting plate still bolted up n.b. the only shims fitted are in in position i).

So is this ‘float’ acceptable or does it need to be taken up?

And a follow on question, if I may, does the pinion/bevel gear cluster spin on it’s spindle or do they move as one (hence the outrigged bearing)?

Andy B

wdietz186
888
Posts: 672
Joined: Sun Sep 10, 2006 4:40 pm

Re: Lower bevel gear spindle shimming - Darmah

Post by wdietz186 » Tue Nov 06, 2018 10:43 am

The shims on the bevel support plate are generally between the the gear and the support plate. Could be shim[s] between the gear and the spindle would be needed to keep the gear from too deep engagement with the upper bevel gear. Has the support plate been off before to your knowledge? It's very easy to lose shims when the plate is removed. The spindle should be free to spin if needed but 1mm of play seems too much. I would shim between the gear and spindle to take up the play. It probably isn't too critical as when the gear is driven it will load the gear outwards toward the support plate. A shim between the spindle and the case bush might work but it could tear up the bushing as the spindle turn.

andybaggies
Cucciolo - the Lil Pup
Posts: 4
Joined: Thu Nov 01, 2018 11:52 am

Re: Lower bevel gear spindle shimming - Darmah

Post by andybaggies » Tue Nov 06, 2018 12:19 pm

Could be shim[s] between the gear and the spindle would be needed to keep the gear from too deep engagement with the upper bevel gear.
Yes, that's what I was thinking.
Has the support plate been off before to your knowledge?
Not since a rebuild by a noted Ducati workshop - which of course then made me think the float is probably ok. :?
The spindle should be free to spin if needed but 1mm of play seems too much.
Yeah, it does doesn't it? & that's what started getting me worried.
It probably isn't too critical as when the gear is driven it will load the gear outwards toward the support plate. A shim between the spindle and the case bush might work but it could tear up the bushing as the spindle turn
Again that's exactly what I had been thinking.

I'm going to strip it down and see how the other spindle has been shimmed... and then dither some more on what to do :)

The only reference I have found only adds to my confusion where Ian Fallon does mention "After the side bushes are fitted the two pins with thrust washers are installed. The straight cut gears and outer thrust washers follow. The timing marks should line up with the central gear." Thrust washers ? hmmm shims perhaps ?

So many thanks for the feedback, much appreciated.

Andy B

User avatar
Craig in France
Cagiva Elefant
Posts: 820
Joined: Tue Mar 23, 2004 3:58 pm
Location: Montpellier, France

Re: Lower bevel gear spindle shimming - Darmah

Post by Craig in France » Wed Nov 07, 2018 3:05 am

andybaggies wrote:
Tue Nov 06, 2018 12:19 pm
The only reference I have found only adds to my confusion where Ian Fallon does mention "After the side bushes are fitted the two pins with thrust washers are installed. The straight cut gears and outer thrust washers follow. The timing marks should line up with the central gear." Thrust washers ? hmmm shims perhaps ?
Hi Andy

I think this comes from an instruction in the 860 Workshop manual where it is written:

"Attenzione!
Prima di effettuare il montagio occorre ricordarsi di mettere sotto i perni le relative rondelle di rasamento"


Which translates to:
"Attention!
Before installing the shafts, remember to fit the associated shims* under the shafts.

* 'Shims' or 'thrust washers'? Same difference. You choose ... :)

The Dramah manual has similar:
"Montare i due alberini porta ingranaggi nelle loro sedo facendo bene attenzione ad inserire sotto di essi le relative rondelle di rasamento"
.

The only problem is that I can find no reference to these "Rondelle di rasamento" in the parts books for either engine. The only shims I can see are for shimming the bevel gears (which is the most important anyways). See below:

Image

But that said, I find it strange that the shafts should have any end play ...

Dunno whether this helps :?

Craig

ducadini
750 Sport [BEVEL]
Posts: 220
Joined: Sat Jul 31, 2004 8:54 am
Location: Antwerpen

Re: Lower bevel gear spindle shimming - Darmah

Post by ducadini » Wed Nov 07, 2018 7:27 am

Due to the helicoidal teeth, the connecting gears are pushed outward (and upward), hence only shims #24 on the outside.
Since the gear to the crank is a straight-toothed (?) one, there is no need for additional shimming.
Don't want to make the shimming harder than it already is :shock: :shock:

ciao
ducadini

anyone at Novegro this weekend ?
Nego i ricordi peggiori
Richiamo i migliori pensieri

andybaggies
Cucciolo - the Lil Pup
Posts: 4
Joined: Thu Nov 01, 2018 11:52 am

Re: Lower bevel gear spindle shimming - Darmah

Post by andybaggies » Fri Nov 09, 2018 11:39 am

Dunno whether this helps :?
Nope! just adds to the confusion :) But seriously that’s half the problem as none of these instructions or diagrams give exact details and are open to too much interpretation... And from my Darmah workshop manual there’s yet another “Fit the two timing gear shafts taking care to place the shims in the same positions in which they were before engine strip down. Fit the two timing gears on the shafts, taking care to align the reference marks. Fit the shims on the shafts.”

This is similar to Craig's quote from the 860 manual and does, to me at least, imply there are shims at the casing bush side i.e. under the shafts. I’ve also seen a video on youtube that confirms the same. But best of luck trying to find the part number or reference to it on any of the Ducati spares sites. And I note the spindle at the casing side is a smaller diameter from the end that holds the gear cluster.

But then Ducadini wades in :(~ and confirms the thought that the bevels press outwards and further shimming isn’t required. Which also confirms the manner it was rebuilt. And the one that I'm favouring.

So what to do? Oh lord I dunno :? and I think I’ll stop dithering for the moment & finish the top end & barrel strip whilst all the information is soaking in and hope a decision pops out from the ether. :idea:

Or perhaps I’m just getting bevel OCD and making a mountain out of a molehill....

Thanks for the all the replies & info though guys. Much appreciated.

Andy B

Post Reply

Return to “Engine & Transmission Shop”