Making a Cushier Cush Drive

[dlaing]

Bruce, IMHO you want to take material out in proportion to the thickness of the wedges. With smaller holes, as Greg has done, this is a simpler consideration. Larger holes require a bit of analysis, with more holes placed at the wider ends. Again, I don't think this is anything to get hyper-concerned about, but then, my arguments in this thread seem to've been "errha-rational".

EDIT, now that I think more rationally.....what I said below is not true. The wider end would need more holes to allow for more travel. But due to more force at the narrow end there should proportionally be more holes to width at the narrow end....which was what I was thinking originally, but neglected to add travel to the equation

The wider ends have more space for holes, but the narrow end needs more cush, so I would ensure that the narrow end has as many holes as the wide end.

Unlike Greg and Ratchet, I have no experience drilling holes in the rubber and opening up years later. I don't even know how firm the rubber is.

But rationally and apparently conservatively speaking I would aim for two rows of smaller evenly spaced holes, where no two holes are within there own diameter from one another.

Probably about two hole diameters from one another would be about right, and I would stay away from the perimeter of the wedge.

At the narrow end of the wedge, getting kind of close to the perimeter is necessary, but don't get to within a hole's diameter of the edge.

In this photoshoped image, the holes should have appeared a little larger at the wide end due to perspective, and a little smaller at the narrow end.

BAA, YMMV and this is completely hypothetical. Greg's or Ratchet's strategies may also be perfectly fine. I just think a more conservative approach would be wise, because I have seen too much rubber break down from ozone, over compression, and over flexing.

[guzzijack]

Unlike Greg and Ratchet, I have no experience drilling holes in the rubber and opening up years later. I don't even know how firm the rubber is.

 

One question. Have ever taken the cush drive apart and serviced it on your own bike?

 

Gj

[belfastguzzi]

One question. Have ever taken the cush drive apart and serviced it on your own bike?

 

Gj

SSSSSShhhhhhhhhhhh! You don't ask questions like that!

There are some people here who don't even have bikes....

[dlaing]

SSSSSShhhhhhhhhhhh! You don't ask questions like that!

There are some people here who don't even have bikes....

SSsssshhhh, you are on to my secret!

But if I did have a bike, the answer is no, I have not taken the cush drive apart. If I had, I might have a better clue about how close to the hardness of steel they are. FWIW I mentioned that I have not seen inside the cush drive a few posts ago.

Years ago, probably after reading Ratchet's first post about cush drives, I did make one attempt, but balked when it became clear that the button screws were in TIGHT. To me the benefit did not out weigh the PIA factor.

I did however have a V65 that has cush rubbers that are visible with every rear tire change.

Those rubbers were not rock hard, but I recall they got harder and beat up as the years progressed and at one point I replaced them.

Mike Wilson had better luck or took better care of them on his small block than I did on mine.

It may be possible I messed them up by not meshing the vanes with the rubbers properly, or maybe it was from drilling them as somebody had recommended? I really can't remember

[guzzijack]

EDIT, now that I think more rationally.....what I said below is not true. The wider end would need more holes to allow for more travel. But due to more force at the narrow end there should proportionally be more holes to width at the narrow end....which was what I was thinking originally, but neglected to add travel to the equation

 

But the puck is a 3 dimensional object and flexing forces are not limited to one direction. The narrower (apex) end of the triangle is actually the thicker/deeper part when viewed side (edge) on. Where is the rationale in limiting the imitation of a Toredo Navalis on speed to the one plane? Why not drill that thicker part of the puck from the side elevation to better distribute the flexing?

 

BTW: As you haven't actually serviced the cush drive and ensured that the drive plate is at least free to move on your bike, it is almost certain that you are running with a locked rear drive - given that Mandello is the centre of a grease free zone Bite the bullet and commit yourself to replacing the button head retaining screws, (if need be), and at least make sure the drive plate is free to move on its spigot. Your clutch, gearbox, UJ and drive shaft will thank you for it.

 

GJ

[chris a]

WOW !!!!! this one is a real monster thread...

Unless I missed it , no one has come up with a set of drilled pucks that have failed which implies that it is safe and the EASY way to go.I'm certain that if it wasn't then Pete , Greg and all the other old hands would not endorse it . Any pics of trashed ones out there to post ???

Pucks made of more compliant material would be great and if you go ahead then I'd be interested Dave.I drilled half a set and installed these years ago with no probs but a local ( French ) Guzzi pro tut tut'ed . I guess he just lives with drive train wear and they all seem to have a very conventional ( read stuck in the mud !!) approach down here.My "holy" pucks are staying in ....

[dlaing]

But the puck is a 3 dimensional object and flexing forces are not limited to one direction. The narrower (apex) end of the triangle is actually the thicker/deeper part when viewed side (edge) on. Where is the rationale in limiting the imitation of a Toredo Navalis on speed to the one plane? Why not drill that thicker part of the puck from the side elevation to better distribute the flexing?

 

BTW: As you haven't actually serviced the cush drive and ensured that the drive plate is at least free to move on your bike, it is almost certain that you are running with a locked rear drive - given that Mandello is the centre of a grease free zone Bite the bullet and commit yourself to replacing the button head retaining screws, (if need be), and at least make sure the drive plate is free to move on its spigot. Your clutch, gearbox, UJ and drive shaft will thank you for it.

 

GJ

Excellent points!

I need to buy new tools anyway.

[dlaing]

WOW !!!!! this one is a real monster thread...

Unless I missed it , no one has come up with a set of drilled pucks that have failed which implies that it is safe and the EASY way to go.I'm certain that if it wasn't then Pete , Greg and all the other old hands would not endorse it . Any pics of trashed ones out there to post ???

Pucks made of more compliant material would be great and if you go ahead then I'd be interested Dave.I drilled half a set and installed these years ago with no probs but a local ( French ) Guzzi pro tut tut'ed . I guess he just lives with drive train wear and they all seem to have a very conventional ( read stuck in the mud !!) approach down here.My "holy" pucks are staying in ....

You and the experts may well be right about the durability of the holy pucks.

Apparently I am the only one who ever replaced them and that was on a V65 not a V11, and the rubber was apparently much softer on the V65 as I recall it being about as soft as tire tread.

Few have taken a V11 over 40,000 miles and only Ratchet is close to that with drilled pucks. I am sure he will keep us informed of how well they are doing. It would be interesting to see his hole drilling strategy.

I might just drill a few small holes for the pucks that effect deceleration as nobody has indicated acceleration being a problem.

I also suspect fuel efficiency and power are lost to cush in the direction of acceleration. It sure would be nice to have the R&D to design the ultimate cush with maybe 10mm of rising rate dynamic cush under maximum gear dropping deceleration, and maybe 5mm of linear dynamic cush at maximum gear banging clutch popping acceleration. Springs, oil damping, etc. Maybe in the 2050 model year Norge????

[mike wilson]

I might just drill a few small holes for the pucks that effect deceleration as nobody has indicated acceleration being a problem.

I also suspect fuel efficiency and power are lost to cush in the direction of acceleration. It sure would be nice to have the R&D to design the ultimate cush with maybe 10mm of rising rate dynamic cush under maximum gear dropping deceleration, and maybe 5mm of linear dynamic cush at maximum gear banging clutch popping acceleration. Springs, oil damping, etc. Maybe in the 2050 model year Norge????

 

The cush drive is there to deal with the shock loadings associated with the transition between acceleration and deceleration in _both_ directions. There may be some loss of fuel efficiency and power but it is miniscule compared with, for instance, turning the drive through a right angle in the drive box. Otherwise, the hub would get hot enough to either melt the rubbers or need continual lubrication/cooling.

[pete roper]

Oh for f*cks sakes! 9 bloody pages? God give us strength!!!!

 

Pete

[mike wilson]

Education takes time if it's done properly. 8-)))

[g.forrest]

just a thought. but is there a conversion to chain drive for guzzi, perhaps this could cure all problems of drive lash. i'm open to hear others thoughts on this.

[Guest ratchethack]

just a thought. but is there a conversion to chain drive for guzzi, perhaps this could cure all problems of drive lash. i'm open to hear others thoughts on this.

Forrest, there was a Euro race team many years ago that I believe campaigned chain drive V-twin Guzzi conversions.

 

However, chain drive is no "cure all" for driveline lash. As Pete has explained so many times over the years, and as I mentioned in post #63 of this thread http://www.v11lemans.com/forums/index.php?...st&p=125764 there is for all practical purposes no driveline lash on the Guzzi between the transmission and rear wheel -- just as with chain drive setups. The "driveline lash", or "driveline slack" is in the transmission, and can be directly measured, as I have done and posted (see post at link).

 

The point at the link relative to your proposition of a "chain drive cure all" was:

 

The gap between shift dogs and sliding muffs can be directly and very easily measured. Since there are virtually no other sources of slack in the driveline of any measurable amount, this is the same as a measurement of the total driveline slack. With the bike in first gear, the dog-to-sliding muff gap in the first gearset amounts to 70 mm of fore-aft movement at the rear wheel. This is by no means excessive for any motorcycle with a constant-mesh transmission.

[Guest ratchethack]

Education takes time if it's done properly. 8-)))

And all too frequently, many times longer when done improperly. . .

 

But then, there have always been and will always be none so blind as those who will not see. . .

 

The cush drive is there to deal with the shock loadings associated with the transition between acceleration and deceleration in _both_ directions. There may be some loss of fuel efficiency and power but it is miniscule compared with, for instance, turning the drive through a right angle in the drive box. Otherwise, the hub would get hot enough to either melt the rubbers or need continual lubrication/cooling.

Good point, and well made, Mike.

[dlaing]

The cush drive is there to deal with the shock loadings associated with the transition between acceleration and deceleration in _both_ directions. There may be some loss of fuel efficiency and power but it is miniscule compared with, for instance, turning the drive through a right angle in the drive box. Otherwise, the hub would get hot enough to either melt the rubbers or need continual lubrication/cooling.

Thanks Mike!

I really appreciate your posts

Comprehensible and no hostile attitude.