Making a Cushier Cush Drive

[docc]

Mine has three discs: the outer stainless steel looking retaining ring, the inner forged steel drive with the splines on one side and vanes on the other, and an intermediate fiber disc(not shown in any of Greg's photos) which looks to be made of a fiber friction material like a clutch disc or brake pad. With it all caked up it looks like part of the black metal drive hub, but it peels off and cleans up.

 

EDIT: The Workshop Manual, Section F page 10, refers to the retaining plate as the "washer", the intermediate fiber plate as the "gasket" and the inner plate as "plate with gearing."

 

It looks like a pretty abrasive gasket judging by the wear indication on the inner plate. If, indeed its only purpose is sealing there would be nothing wrong with a coat of really slippery moly as long as it doesn't sling out on the wheel too much.

 

[Guest ratchethack]

Oh - THAT disk. I'd remembered it wrong, sorry. I was thinking it covered the whole plate.

 

I think of that as more of a "ring" - I believe this serves (again) to keep out debris. It "floats" between the stanless retaining ring and the back-and-forth movement of the forged steel drive plate. The ring doesn't carry any load in the sense that a clutch friction disk would carry load. Looks kinda funny, though, as I recall. Some sort of fiber material.

 

Looks like you've got a "surgically clean" operation there, Docc!

[docc]

You don't work on your Sport on a Persian rug? Gotta get on board there, buddy.

 

There is a significant wear ridge from the fiber disc into the forged drive hub. As long as it's there just as a seal and isn't supposed to be a friction damper I think I'll try to slick it up a bit more with a coat of moly along with the grease. The disc is self lubricating as the grease slings off the drive splines.

[Guest ratchethack]

Yep. I remember the term "gasket" from my manual. The wear ridge and marks are from dust and grit that get betweeen the gasket ring and the "washer" and the "plate with gearing"... It's an indicator that your cush drive is doin' its job. Don't ya love those Italian-English translations in the manual? Keeps you guessin' most of the time. . .

 

Again -- I'd be careful about being too generous with grease on the "gasket" -- moly or no, it WILL end up on your wheel (and tire).

[dlaing]

No one mentioned the friction disc between the vane plate and the retaining ring.

Very interesting

This is getting more and more intriguing.

It makes sense that there should be some sort of damping to keep the cush from bouncing back and forth beyond the free play.

Any force necessary to overcome the friction ain't gonna damage dah splines, but the friction may make drive lash more noticeable, and lubing a friction disk might make for less jolting drive lash, although possibly bouncier.

To find out, I suppose you could temporarily reassemble without pucks to see if it provides friction damping. Or is the 'plate with gear' held up against the "gasket" by the pucks?

I believe for it to function as a friction disk it cannot be clamped under the full force of the button screws, nor completely free moving. It would ideally have to be under some sort of fixed spring force, but there are no springs unless the washer or the pucks create the spring force.

Since so many people have been lubing these for over 40 years, it is hard to believe it is a friction ring.

[pete roper]

Oh good grief! How many? Eleven! Eleven bloody pages!!!! Sodomise a thousand guinea-pigs! Is there no end to it?????

 

Pete

[g.forrest]

well i'll be pucked pete!

[belfastguzzi]

Is there no end to it?????

 

Pete

No not yet.

 

Nobody has really mentioned the radiused edges on these rubber wedges. Can Guzzi have got this dimension right? I doubt it! There must be room for improvement. Why are they rounded off in such a fashion anyway? It can't be for stylistic appearance as the things can't be seen in normal useage. Can somebody please explain?

 

Working on the basis that Guzzi can't have got this right, I first considered cutting a hard chine, but now I'm more inclined to go for some sort of serrated, waveform along the edge of the wedge. That ought to aid cushy pliability no end. Of course it's not all about hard science and what would work best from a technical point of view – these are Italian bikes – so it's worth putting in a bit more effort with the scalpel and fine sandpaper. Go for something like a clinker-built effect or even cedar shingles. Extra cush AND beauty. A SOLUTION, as I think you'll agree.

 

See Docc's basic rounded edge wedges, as they come from the factory (though Docc seems to have polished his).

[dlaing]

Guzzi sure messed up by not giving us color choices.

Black may be fine for the Scuristas, but Swedish Gummy Fish Red would surely be more popular. (Sorry, your monitor may need calibration for color to appear correct)

 

Oh good grief! How many? Eleven! Eleven bloody pages!!!! Sodomise a thousand guinea-pigs! Is there no end to it?????

 

Pete

No pucking the pigglies permitted, puh-lease!

[Skeeve]

Oh good grief! How many? Eleven! Eleven bloody pages!!!! Sodomise a thousand guinea-pigs! Is there no end to it?????

 

Wrap'em in duct tape first, Petey![1]

 

Hopefully, this post will push it over to 12 pages. Just eyeballing it, but it looks about like it should...

 

Ride on! [a cushier cush drive]

 

 

 

 

[1] 'Cause that way they don't explode when you're sodding'em. Last longer that way, y'know?

 

 

 

That last reply didn't quite do it!

 

Do we have 12?

 

 

ObCushDrive content: How about a hydraulic baggie that smooshes the fluid one way or the other under thru a calibrated hole? Maybe w/ a "spike load" relief valve in the mix?

 

Nuts!

 

This dang BBS software keeps appending my posts to the last one, so I can't push it over the top to 12 pages!

 

Someone, give me a hand here! We can't disappoint Pete!

[docc]

If I hadn't been saddled with a wheel bearing change I may have poked my cushies while they were out. I'd still like a more 'elegant' solution, if even cleaner holes maybe spaced with a template to be all uniform. Sure it's a bit anal, but at least I'm not into gerbils with or without duct tape.

 

I did clean it all up nicely, apply silicone grease to the cushies, BelRay waterproof to all the metal parts and bearings, copper anti-seize to the bolts and put it all back together with a new Pirelli Strada.

 

Me bitty wombatty bwain even thought of Pete and his fuzzy buddies while setting my uncalibrated torque wrench to 120NM to set the axle nut torque from the wrong side.

 

A BMW buddy was explaining how they crack the gearbox from the motor and slide it back about every 20,000 miles to put a bit of grease on the input splines where the clutch disc slides; says it smooths the clutch operation and saves the splines. These are surely the same splines Greg referenced as being vulnerable to the engine braking. I've yet to check the Guzzi manual to see if lube is recommended there upon reassembly. It was in the Haynes manual for the R80/100

[Guest ratchethack]

If I hadn't been saddled with a wheel bearing change I may have poked my cushies while they were out. I'd still like a more 'elegant' solution, . . .

I'm finding myself rapidly becoming as barking mad gobsmacked as Pete. . .

 

Hmmmm.

 

Wot could be a more 'elegant' solution than one that has all 5 of the following characteristics:

 

1. Well proven long term

 

2. Unanimously endorsed by the Pro's

 

3. 100% Effective

 

4. Costs nothing

 

5. Takes relatively little time and effort

 

-- Um, something such as Greg suggested in post #1, f'er example?!

 

Now maybe if someone offered something that was:

 

1. Completely speculative, without precedent, and entirely experimental

 

2. Not recommended by any of the Pro's

 

3. Unknown effectiveness

 

4. Unknown expense

 

5. Unknown investment of time and effort -- could take from months to years

 

-- Does THAT sound 'elegant' in comparison??

[dlaing]

Didn't someone once write something like that about multivalved engines and other innovations?

[Guest ratchethack]

Didn't someone once write something like that about multivalved engines and other innovations?

Um, I seriously doubt it, but then isn't this very Forum an example of the limitless possibilities of wot people write??

 

Just because a concept is an innovation to YOU , Dave, doesn't mean it's new . . .

 

Multivalve engines are at least 100 years old now. . .

 

Innovations such as desmodromic valve actuation were used by (among others previously) Mercedes in F1 racing (as I recall?) in the '20's. . .

[dlaing]

Dave, doesn't mean it's new . . .

Right you are, here are some BST CF wheels with urethane bushings:

Innovation often involves taking an idea that others huff at and making it sucessful.

Greg Field is good at that. I am surprised he is not on board with urethane