Making a Cushier Cush Drive

[luhbo]

.....

If you could make the entire drive train out of some soft polymer, yet retain dimensional stability, the driveline slack would remain the same as with steel and alloy. But it would feel rather cushy........

 

That's the basic misinterpretation: if it feels cushy, then it's elastic, things move relative to each other, you have more slack as Dave says.

 

Simply drilling these hard and cheap rubber blocks 'till they look as a swiss cheese is just bullshit, anything but brilliant

 

If some are afraid of closing the throttle because they think this will destroy their Guzzi, then a drilling machine won't help them.

 

Besides, taking an axe and having a good time behind the shop for some hours can also cure a lot. So why not...

[mike wilson]

That's the basic misinterpretation: if it feels cushy, then it's elastic, things move relative to each other, you have more slack as Dave says.

 

No you don't. You have exactly the same amount of slack and a different feel to the driveline once that is taken up.

 

Simply drilling these hard and cheap rubber blocks 'till they look as a swiss cheese is just bullshit, anything but brilliant

 

If some are afraid of closing the throttle because they think this will destroy their Guzzi, then a drilling machine won't help them.

 

 

Why? If you take a piece of steel, it will have a certain strength and flexibility. Drill it full of holes and the strength and flexibility will change. Same for a piece of wood. Same for a piece of rubber. Blocks of elastic material have been used for decades in vehicle drive trains. Changes in size, composition and form are standard ways to alter the characteristics of them. If you have a rational argument against this, rather than an emoticon, I would be interested to hear it.

[Guest ratchethack]

That's the basic misinterpretation: if it feels cushy, then it's elastic, things move relative to each other, you have more slack as Dave says.

Words carry meaning.

 

Best use them properly or basic misinterpretations run wild in the streets -- and some of 'em carry nasty consequences . . .

 

Let's get this straight. Somebody's just got to , f'er cryin' out loud. . .

 

Driveline slack is the amount of free movement of the driveline with NO LOAD on the driveline!!!

 

As soon as ANY LOAD is applied to the driveline, the slack is used up!!!

 

Regardless of how stiff a cush drive is -- from sponge cake soft to chrome moly steel hard -- as soon as a cush drive deforms from LOAD applied to it, it continues to take on LOAD from the engine relative to the load it transfers to acceleration of the Guzzi. It does this in both directions, under acceleration and deceleration.

 

AT NO POINT in the deformation of a cush drive from application of LOAD is there ANY point where there is NO LOAD on the driveline!!!

 

Therefore, ANY degree of flexibility of a cush drive DOES NOT and CANNOT contribute to driveline slack!!!

 

Driveline slack = NO LOAD*

 

Cush drive deformation = LOAD

 

That oughtta finally drive a stake through the heart o' this one. . .

 

But then again, perhaps not. . .

 

We do seem to have a number of those with a need to raise grief to meet quite high personal Grief Level Optimum settings. . .

 

*Those with interest in investing may find further info here : http://www.investopedia.com/terms/n/no-loadfund.asp

[Tom M]

[dlaing]

Words carry meaning.

 

Best use them properly or basic misinterpretations run wild in the streets -- and some of 'em carry nasty consequences . . .

 

Let's get this straight. Somebody's just got to , f'er cryin' out loud. . .

 

Driveline slack is the amount of free movement of the driveline with NO LOAD on the driveline!!!

 

As soon as ANY LOAD is applied to the driveline, the slack is used up!!!

 

Regardless of how stiff a cush drive is -- from sponge cake soft to chrome moly steel hard -- as soon as a cush drive deforms from LOAD applied to it, it continues to take on LOAD from the engine relative to the load it transfers to acceleration of the Guzzi. It does this in both directions, under acceleration and deceleration.

 

AT NO POINT in the deformation of a cush drive from application of LOAD is there ANY point where there is NO LOAD on the driveline!!!

 

Therefore, ANY degree of flexibility of a cush drive DOES NOT and CANNOT contribute to driveline slack!!!

 

Driveline slack = NO LOAD

 

Cush drive deformation = LOAD

 

That oughtta finally drive a stake through the heart o' this one. . .

 

But then again, perhaps not. . .

 

We do seem to have quite a number of those with a need to raise grief to meet quite high personal Grief Level Optimum settings. . .

 

I thought I was done, but when you write with such great clarity, it gives me hope that we can share understanding.

 

Driveline slack is NOT the amount of free movement of the driveline with NO LOAD on the driveline!!!

Driveline slack is the amount of free movement of the driveline going from maximum hard decceleration to maximum hard accelleration!!!

 

It is not true that,

"As soon as ANY LOAD is applied to the driveline, the slack is used up!!!"

As soon as MAXIMUM LOAD is applied to the driveline, the slack is used up!!!

 

Driveline slack = MAXIMUM LOAD ACCELERATING TO MAXIMUM LOAD DECCELERATING

 

Cush drive deformation is part of driveline slack and is proportional to ± LOAD

 

This thread started with the premise that decceleration does the damage.

Was acceleration not mentioned because it is essentially unavoidable, while using engine for braking is avoidable?

Or does engine braking do more damage and thus does it need more cush?

In re-designing the cush rubbers, one could add more dimensional cush in the direction of decceleration while giving up accelerative cush.

 

And for I think the fourth time, which spline is at risk?

I guess every gear, the clutch, the shaft, and the pinion are at risk.

I think Greg indicated the Scura clutch splines were at risk.

The one the wheel slides into would be my guess.

Everyone's opinion is welcome for these questions.

Just because I think that:

polyurethane is a better material,

too many drill holes is bad,

and adding holes increases slack,

does not mean I don't respect people who disagree who certainly know more about the cush and splines than I.

And, it does not mean I don't think staying with the original rubber,

drilling some holes, adding silicone grease, and incidentally increasing slack a little for the benefit of cush, is a good idea.

Thank you Greg for posting an excellent how to.

[luhbo]

No you don't. You have exactly the same amount of slack and a different feel to the driveline once that is taken up.

Why? If you take a piece of steel, it will have a certain strength and flexibility. Drill it full of holes and the strength and flexibility will change. Same for a piece of wood. Same for a piece of rubber. Blocks of elastic material have been used for decades in vehicle drive trains. Changes in size, composition and form are standard ways to alter the characteristics of them. If you have a rational argument against this, rather than an emoticon, I would be interested to hear it.

 

Mike, that's not so much a problem: take a piece of metal or rubber, clamp it on one side, stretch it with a certain, in this example preferable heavy load, measure the elongation under this load, and then drill a good hole through the probe. Depending of the load two things may happen: one is it will be stretched for some more millimeters, the other one is you will have two of them.

 

There is one other problem. Let's assume the hole was small enough so that you can repeat this stretching often enough, then you may notice that the piece of rubber gets warmer and warmer, hot maybe. Why that? It's just the work that you apply.

 

These rubber parts as they are delivered by Moto Guzzi work as designed. Drilling them is not a good idea. They are not designed to work as soft springs with relatively big elongations, it's just the wrong material and the wrong shape.

 

If you make the geometry too soft, not rigid enough, the geometry will disintegrate.

 

A hole here and one there may do no harm, at least it gives you the good feeling that you were kind to her, but these cheesy pix and the 50% reduction of cushions are something very worth a controvers discussion, to say the least.

 

You can probably see what I want to say with the above, hopefully also behind the one or other wrong word or grammatical construct.

 

Maybe that we have a member here with some engineering and anglo-american background and willing to jump in and give a better understandable explanation about the relation between load - elongation - shape - stress - inner damping - heat - proper material - failure.

 

It's no help if you put a Webster besides your ratchet.

 

Hubert

[dlaing]

If you have a rational argument against this, rather than an emoticon, I would be interested to hear it.

I guess you have not noticed how many emoticons Ratchet uses for his errha-rational arguments.

[dlaing]

Engine braking is notoriuously hard on all the splines of a Guzzi. In my day job selling Guzzi parts and my morning job fixing Guzzis, I see so many hammered splines that I normally recommend that Guzzi riders avoid engine braking altogether. This is especially true for all the early (and some late) Guzzis that lacked a cush drive in the rear wheel. Even on those with a cush drive, I recommend against engine braking unless you are sure the cush drive is actually functional. I've seen a ton of them that are so rusty that they do nothing at all to absorb shock.

Are these the splines that get hammered the hardest?

[belfastguzzi]

BTW, I can't see an emoticon for 'tongue in cheek' but I think BFG might have a use for one to avoid the usual Transatlantic confusion

Please, Jaap?? You gave the old codger icon on my last request. Perhaps you would be so good as to follow-up with GJ's hint?

[luhbo]

Another reason why this mod is not a real good idea: these "springs" are mounted without any preload. No sag discussion here, but without preload one side gets compressed while the other side floats around, totaly bored and unloaded. The moment the load changes its orientation it should definitely be possible to hear it "smack".

 

Merriam-Webster says: slack - not tight or taut . If that aint spot-on...

 

Hubert

[belfastguzzi]

BFG, I'm either slightly confused...

Excellent! I need a special 'point' for this achievement. Perhaps Nog would be so bad as to design one?

 

Ratchet, read MikeyMike's post for clarifiaction about which splines he was reffering to, then set to.

However I suggest that this mod be carried out on all interfacing metallic splines anywhere. I started the experiment on my driveshaft splines. Honest.

Knock 'em out – this mod is gonna be all the rage soon.

[Guest ratchethack]

Excellent! I need a special 'point' for this achievement. Perhaps Nog would be so bad as to design one?

 

Ratchet, read MikeyMike's post for clarifiaction, then set to.

Knock 'em out – this mod is gonna be all the rage soon.

BFG, it seems that a TFPIC (tongue firmly planted in cheek) emoticon may serve well to bridge that Great Transatlantic Cultural Divide. By all means, let's have one.

[Greg Field]

Are these the splines that get hammered the hardest?

 

 

Only in extreem circumstances. Bad wheel bearings or continual cycles of rusting and scraping off of rust are what most often takes out the wheel splines.

[belfastguzzi]

the

Great Transatlantic cultural divide?!

-- is that

I always assumed

humor was supposed to be well, er....funny??

it's supposed to be, um, er... spelled with a 'u' humour

[docc]

For all but the Scuras and others with the single-plate clutch, the major hammering takes place on the splines of the i.d. of the flywheel and the o.d. of the clutch hub.

 

 

Just for clarification, this is what I think Greg said about where he has found the wear. I can't visualize this interface as I've only had my clutch exposed once. I suspect this is an area that will tolerate zero lubrication.