'75 900ss front axle/speedo drive weirdness

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in-two
Diana
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'75 900ss front axle/speedo drive weirdness

Post by in-two » Sun Jun 10, 2012 3:01 pm

I don't know if i'm having a senior moment, or just a Ducati moment, but help is needed! My ss is literally hours away from completion after two years of cleaning, scrubbing, painting etc. etc.,
Whilst test fitting the front wheel I couldn't immediately remember where the i/d 20, o/d 28 washer went, the one on the speedo drive side. After trying both options,(1) R/H forkleg/washer/speedo drive, and (2)fork leg/speedo drive/washer about ten times, I've come to the conclusion that neither works ... I'm not unfamiliar with mechanical devices, and have owned the bike for 35 years, so I've had to sit down, pour a beer, and consult my therapists, you guys. I'm fairly sure the correct setup is the first option, washer between fork leg and drive, but when the axle is tightened, the wheel rotates stiffly and the drive moves a bit axially on rotation. This is hardly surprising since the step in the axle bears on the washer which bears on the alloy drive casing pushing it against it's internal sleeve, preventing free rotation. The second set up works perfectly except the axle is then drawn 15mm (thickness of the drive) too far into the disc carriers, enough for the crossbar to touch the outside of the fork leg, obviously wrong. The drive is a Veglia 23/11, and, although I pulled it down a few years ago i'm fairly sure its the original part, and I don't have any others hanging about. I've checked for bent fork tubes/triple crowns and the disc carriers are sitting square in the wheels, bearings and distance tube are all good. I didn't completely strip the drive, just soaked it, blew it and filled it with transmission oil, straightened out the slightly battered drive tang thingy. To my eye the assembly lacks a thin internal sleeve to the speedo drive, length about 2mm longer than the thickness of the drive, I/D to fit snugly over the axle, O/D to fit inside the steel drive rotor which would be free to rotate whilst the alloy casing was held between the axle step and the sleeve. This would also make the washer unnecessary, but I'm fairly sure there was no such thing, or maybe it fell out unnoticed? I would really appreciate some guidance on this seemingly stupidly simple problem.
'75 900 SS
"don't get behind on your cheating, but don't get ahead either" Cook Nielson, California Hotrod

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BevHevSteve
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Re: '75 900ss front axle/speedo drive weirdness

Post by BevHevSteve » Sun Jun 10, 2012 4:19 pm

If your speedo drive slides over your axle with the same clearance as the axle slides through the fork leg the the speedo drive is not missing anything. There is supposed to be a washer between speedo drive and inside of fork leg. If it is even slightly cupped then replace it with one of our stainless washers so that everything falls back into alignment.
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Craig in France
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Re: '75 900ss front axle/speedo drive weirdness

Post by Craig in France » Mon Jun 11, 2012 1:19 am

in-two wrote: .. when the axle is tightened, the wheel rotates stiffly and the drive moves a bit axially on rotation. This is hardly surprising since the step in the axle bears on the washer which bears on the alloy drive casing pushing it against it's internal sleeve, preventing free rotation.
I think Steve has it. This is a not uncommon problem and, as he says, is caused by the washer getting dished. But unless you know, it's a real head-scratcher!

Don't muck around. Get a new stainless one and all should be resolved.

Good Luck!

Ciao

Craig

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Diana
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Re: '75 900ss front axle/speedo drive weirdness

Post by in-two » Mon Jun 11, 2012 5:23 am

Thanks for speedy replies, but here's the thing, the washer I have is the original but flattened carefully and dimensionally O.K., I/D 20.5, O/D 27.75, thickness 1.5 mm. I'd put in one of Steve's washers in a heartbeat, but I can't see how it would help.
The drive has an I/D of 25.07 on the steel rotor/sleeve and 22.60 on the alloy casting, so much bigger than the axle large diameter, 21.90. This means the axle can pass right through the casting and the axle step bears on the washer, which in turn just squashes the casting against the disc carrier bearing, which can't be right, surely.
I 'll try and post photos and/or a diagram but presently the 'upload attachment' feature just rewards me with a ping from the PC.... Murphy's law strikes again!
Thanks again for taking an interest.
'75 900 SS
"don't get behind on your cheating, but don't get ahead either" Cook Nielson, California Hotrod

in-two
Diana
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Re: '75 900ss front axle/speedo drive weirdness

Post by in-two » Mon Jun 11, 2012 1:58 pm

nearly done!448x336.jpg
hand smallest.jpg
speedo drive ID 448x336.jpg
Here's some pics at last, I keep wondering if I have somehow substituted another drive or a bit has fallen out, and my grey cells are too rotten to remember... Oh well!
'75 900 SS
"don't get behind on your cheating, but don't get ahead either" Cook Nielson, California Hotrod

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Re: '75 900ss front axle/speedo drive weirdness

Post by BevHevSteve » Mon Jun 11, 2012 4:01 pm

looks like you have lost the inner sleeve. start hunting. The speedo drive should slip over axle with a very small clearance, the ID should be 20.2mm

You are definitely missing a sleeve inside that speedo drive.
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Craig in France
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Re: '75 900ss front axle/speedo drive weirdness

Post by Craig in France » Mon Jun 11, 2012 11:31 pm

BevHevSteve wrote: You are definitely missing a sleeve inside that speedo drive.
HTH

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in-two
Diana
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Re: '75 900ss front axle/speedo drive weirdness

Post by in-two » Mon Jun 11, 2012 11:59 pm

Hallelujah!
I can't tell you how relieved I am to (a) not be drummed out of the Ducati mechanics hall of fame (b) shuffle off into permanent dementia (yet)! I was actually drawing a spacer for my local lathe jockey to produce when your posts popped up, and had just thought mmm, maybe a small step to poke through the casting of the drive is the way to go!
I can't imagine where the inner sleeve has got to, so could you post the dimensions ? No problem to work it out from scratch, but nice to know.
Today's job is assembling the rear hub & wheel, more spacer juggling, so this correspondence may not be over.
Huge thanks again for helping, I might even have the bike running this week, for the first time in about 20 years, assuming Uncle Joe Lucas and the Rita Gods are with me, a big assumption, I know.
All the best from sunny Poland.
'75 900 SS
"don't get behind on your cheating, but don't get ahead either" Cook Nielson, California Hotrod

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Steve Foster
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Re: '75 900ss front axle/speedo drive weirdness

Post by Steve Foster » Tue Jun 12, 2012 1:30 am

The drive is a Veglia 23/11, and, although I pulled it down a few years ago i'm fairly sure its the original part
My understanding is that the 23/11 drive is for a 19" front wheel such as those fitted to 750 GT and Sports. The 18" wheel of the SS uses a 20/10 drive I think.
Cheers
Steve
1974 Ducati 750 GT

in-two
Diana
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Re: '75 900ss front axle/speedo drive weirdness

Post by in-two » Tue Jun 12, 2012 3:33 am

Steve,
Yes, I have to say that seems right, 23/11 for 19" , which my bike definitely isn't, and somewhere in the distant recesses of my memory I think there may have been another veglia drive knocking about the garage, which could explain much. A forensic examination of the spares pile awaits!
Thanks for your help and interest.
'75 900 SS
"don't get behind on your cheating, but don't get ahead either" Cook Nielson, California Hotrod

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Craig in France
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Re: '75 900ss front axle/speedo drive weirdness

Post by Craig in France » Wed Jun 13, 2012 1:35 am

in-two wrote: ... so could you post the dimensions ?
One Hi-Quality technical drawing below ... :shock:

Image

Dims, just in case they're not clear:

Overall length: 14.5mm
Length of shoulder: 2mm
OD: 25mm
OD of shoulder: 23mm
ID: 20mm

Male and female edges lightly chamfered.

P.s I'd advise you to get yourself one of Steve's stainless washers anyways. They prevent the soft aluminium casing of the drive getting dished in. A small but worthwhile investment.

Ciao

Craig

in-two
Diana
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Re: '75 900ss front axle/speedo drive weirdness

Post by in-two » Wed Jun 13, 2012 2:19 am

Craig, everybody,
Huge thanks and fantastic news, I found the sleeve! It had obviously dropped out of the drive and was maliciously 'hiding in plain view' in my front wheel junk box... duh!
I now am wondering about the 23/11 issue but I don't really care, the speedo always bounced around like a break- dancer and I don't suppose 20 years in a box has improved it any. It will also give me a new conversation starter when illuminated by blue and red flashing lights..." well officer it was all due to the gear ratio of my speedo drive" etc. etc.
I will order a washer from Steve when I order a fork spring kit, just out of loyalty. My local precision engineers will knock out 50 for a litre of vodka, when they are not re-furbing MIG engines.
Thanks again and wish me luck on getting the thing running this week.

Cheers In- Two
'75 900 SS
"don't get behind on your cheating, but don't get ahead either" Cook Nielson, California Hotrod

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Steve Foster
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Re: '75 900ss front axle/speedo drive weirdness

Post by Steve Foster » Fri Jun 15, 2012 2:07 am

In-two,
Good luck on getting the thing running this week!

Just saw the following FYI.
http://www.ebay.com.au/itm/Ducati-Bevel ... 570wt_1270

And by the way, when you're having your discussion with the blue and red lights flashing in the background, don't mention that the 23/11 drive actually made your speedo read fast with your 18" wheel because then the other party to the discussion about the finer points of speedo gearing will realise that you must be really irresponsible (kind of opposite to claiming that your speedo was reading slow so you inadvertently exceeded the speed limit ....).

And I must say that your Vodka drinking MIG (I assume that you're referring to the Russian jet fighter) maintenance friends sound interesting ... now that would be an interesting forum if they had one. (But Lech, I don't think you should part out the MIG engine even though you would make many, many zloty. And by the way, what sort of oil do you use in it? Straight or multi-grade?)
Cheers
Steve
1974 Ducati 750 GT

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Craig in France
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Re: '75 900ss front axle/speedo drive weirdness

Post by Craig in France » Fri Jun 15, 2012 10:11 am

in-two wrote:It had obviously dropped out of the drive and was maliciously 'hiding in plain view' ...
Ha! As these things 'are wont to do' ... :-D
in-two wrote: ... and wish me luck on getting the thing running this week.
Ok, fair enuf ...

Good Luck!

^>^

Ciao

Craig

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Craig in France
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Re: '75 900ss front axle/speedo drive weirdness

Post by Craig in France » Fri Jun 15, 2012 10:14 am

Steve Foster wrote:And by the way, what sort of oil do you use in it? Straight or multi-grade?
%^)

You're a Bad Man, Steve ... :-D

Craig

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