Lower bevel gear spindle shimming - Darmah

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andybaggies
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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

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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.

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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

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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

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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

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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

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Re: Lower bevel gear spindle shimming - Darmah

Post by 81mhr900ss » Thu Nov 22, 2018 7:41 pm

andybaggies: have you checked this video yet:
https://www.youtube.com/watch?v=BlXSGH-KKGk&t=9s

It may help.

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Re: Lower bevel gear spindle shimming - Darmah

Post by andybaggies » Fri Nov 23, 2018 6:30 am

andybaggies: have you checked this video yet:
Yes I have, thanks.... multiple times :) This is the one I made reference to in my previous post and from 2:50 he mentions "shims on the inside that run against the bronze bush" and "shims on the outside". And it does make real sense, especially with the float I'm seeing, but can anyone find part numbers or reference to the inner shims in any diagrams?

The same guy has also made another great video on head shiming, https://www.youtube.com/watch?v=WqSQ53yWElU where he mentions the self aligning bearing needs shiming in it's bush holder (from 1:00) but again can I find any reference/part number to it anywhere?

I'm still siding with the well respected Ducati workshop who assembled the engine so what I find is what it gets.... Joking aside I think there may be some instances of the factory taking a belts & braces approach which later proved unfounded.

Thanks again,

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Re: Lower bevel gear spindle shimming - Darmah

Post by Craig in France » Sat Nov 24, 2018 9:49 am

Andy, the author of that video is Tim Keyes. Tim has been around a long time and is generally reckoned to know his stuff :) .

Maybe you could ask him? I haven't got an e-mail address for him. Maybe Steve has ....?

HTH

Craig

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Re: Lower bevel gear spindle shimming - Darmah

Post by 81mhr900ss » Sat Nov 24, 2018 9:18 pm

I just sent Tim a quick note to tell him that help is needed!

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Re: Lower bevel gear spindle shimming - Darmah

Post by 1funduc » Sun Nov 25, 2018 12:39 pm

Hello All,
Been awhile since I followed the forum. I have been asked my opinion on this shimming question. Before doing so I want to point out that these are my thoughts and nothing more. I make no claim on expertise. This is just the way I do it.

First off,
I have never found a Ducati manual that was worth a dog doodie. Even the factory manual leaves a lot to be desired. Acquire as many manuals as you can, read them all. You will find answers to different questions in one that may not be in another. These engines are puzzles and thats what makes them interesting. They were designed when labor was cheap and machine tools expensive, that is why they are full of shims.

One comment questioned the idea of running a shim against the case bushing.
Well, remember that the hardened steel shaft is already running in the bronze bush and without a shim would also run against the outer edge of the bush. A shim between the shaft and the bushing would not cause any more wear than would already occur. If anything a shim would act like a bearing and reduce friction between the shaft and the bush.

Comment made re shimming on only one end of the shaft.
All gears are designed to have precise engagement geometry between the teeth of the pair of gears. They cannot move either deeper into or away from each other. Any radial movement where the tooth engagement changes will quickly cause failure of the gearset. Straight cut spur gears CAN move axially to each other but note that their tooth engagement angle (geometry) does not change.

Comment on gear loading,
The idea that the bevel gears are loaded in only one direction is incorrect. With the enertia of the cam drive train, the gears will always be playing catchup to the crankshaft. The cam lobes also cause decceleration and acceleration as the rocker slides over it. The gear loading will be both positive and negative therefor is is imperative that the bevel gears be shimmed with as close to zero end play or backlash as possible.

Comment on shim location,
I place them between the gear spindle and the case bush and also between the gear spindle and the outrigger plate bearing. The gears (the bevel and the spur gear) should be quite snug together. If there is any play between them, replace them. Do not place shims between the spur and bevel gear.

I should add that the shim thickness available includes .05mm. I omitted that size in my video.
That's my $0.02 Thanks for listening.
Tim

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Re: Lower bevel gear spindle shimming - Darmah

Post by 1funduc » Sun Nov 25, 2018 12:44 pm

Dog Doodie.. Gotta love that auto correct. :tisk:

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Re: Lower bevel gear spindle shimming - Darmah

Post by andybaggies » Tue Nov 27, 2018 2:21 am

Tim,

Good grief! I wasn’t expecting such a speedy & thorough response. :o Top man.
I make no claim on expertise
You can 100% say the same for me but I do suspect your expertise is a lot better than mine… And I’m always appreciative of other, more experienced input to help improve my own knowledge.
I have never found a Ducati manual that was worth a dog doodie.
Ain’t that the case as this topic has quite plainly proved. And this is where my engineering knowledge falls short to be able to solve a particular puzzle hence the re-assurance of other’s thoughts.

So your subsequent comments on the various points have proved really valuable and have finally allowed me to come to a conclusion, hurrah! A conclusion I suspected all along was the correct way to go i.e. shim out the spindle float on the bush/casing side. Couple this with a sudden flash of inspiration that saw me realise the shims are the exact same as used for shimming the rocker pins :doh: , and I’m all good to go.

Can’t thank you enough & thanks to all on a great topic.

Cheers,

Andy B

p.s.
They were designed when labour was cheap and machine tools expensive, that is why they are full of shims
Such a great quote.

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Re: Lower bevel gear spindle shimming - Darmah

Post by 1funduc » Tue Nov 27, 2018 6:34 pm

Not too sure that the shims are the same I.D. on either end of the spindle. Off the top o my head, the inner ones are smaller. A good shim source is McMaster-Carr or perhaps any of the shops/suppliers that work on old Ducs.

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Re: Lower bevel gear spindle shimming - Darmah

Post by andybaggies » Wed Nov 28, 2018 12:46 am

I did check by removing the plate & one of the spindles and a spare rocker pin I had lying about was a perfect fit in the bush - 10.5 mm if I remember correctly.

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