Making a Cushier Cush Drive

[Guest drknow]

I'd also like to offer super-light-weight wheels hand tooled from Balsa-Wood. These would be incredibly light reducing unsprung mass significantly, especially if filled with helium! Sharpen up the steering too!

 

Pete

 

man, not to derail this thread, but...

 

I've seen balsa wood strips in ultra lightweight factory Aprilia GP bodywork. It's been used in racing for quite a while. Maybe you can fabricate a monocote assembly with balsawood pressed into a magnesium honeycomb and take us to the next level.

 

Oh, and in keeping with the thread, cush, slop, lash, flex, wiggle, durometer and drillbit.

 

dk

[emry]

I just had to chime in. First Drill the valve stems - many Hi-Po versions are already hollow and filled with sodium --- ooohhhhh.... salt..... Second "Lash" would be defined as clearence "open space" between two parts. What our cush drives allow is "deflection" or movement beyond initial contact. Normally deflection is used when a material will return to its orginal position when the force is removed - springs, bump stops, cush rubbers, etc.. If the material does not return that would be called --- bent or compressed. By drill or replacing with a lower durometer material you are allowing more deflection. This could allow more "slop" which is unwanted lash, drive a 100k Chevy 4x4 and go from reverse to drive, that nice clunk whould be slop. So what is the target resilience of the material, we have a durometer, (how much force it takes to defect our cush) how fast should our cush return to its orginal state. These are the questions that inquiring minds want to know.

 

Man... all these pages over some holes in a rubber.

 

Almost forget... Balsa wood rocks!!! Pete i'll take a set. Whittle 'em up. But seriously balsa wood is still a popular material in light aircraft. Heck even Lotus dashboards were made out of it until the 90's

[emry]

Now that I think about it back in the eighties when a customers "cush" rubbers were worn and they were to cheap to pay for new ones we would just fill the space with some silicone - yeah tub & tile. Pop the drive back in, let it dry for a day and send them on their way. Never had any complaints.

[dlaing]

Another incorrect, "loosey goosey" speculation, Dave. Pete covered this waaaaaaay back on post #94. There are no "cush" springs in the dual disk clutches that most of our V11 Guzzi's have in them -- including yours, mine and Docc's. The only springs in the dual disk clutch that exist act only to clamp the drive components (flywheel, intermediate plate, and pressure plate) together with the driven friction disks in the clutch pack. Single-disk clutches, including many I've replaced on cars, typically have "cush" springs arranged circumferentially (is that a word?) within the clutch hubs.

 

Thanks for the clarification.

Sorry, I totally missed that he was straightening me out in that post.

I was drawn into second and third paragraphs.

My V65 had a clutch with "anti-rattle springs" and it grenaded, luckily with only internal cosmetic case damage.

Certainly another excellent Pete Roper post worth repeating as it full of valuable info:

Single plate clutches tend to use anti-rattle springs, (this, oddly enough, is why Scuras, Rosso Mandellos etc with the single plate clutch rattle when the clutch is disengaged!) these are one of the components in the clutch plate. The twin plate clutch has no anti-rattle devices. The only springs in there are the actual clutch pressure springs which sit between the flywheel and the pressure plate, you couldn't replace them with rubber or anything else.

 

One place where spline wear does very often occur is withing the clutch/flywheel assembley. With a twin plate unit when you engage the clutch, (Pull in the lever.) it de-compresses the friction and intermediate plates. The friction plates are splined to the input hub of the gearbox, the intermediate plate is splined into the flywheel. As the flywheel accelerates and decellerates between power strokes the plates will thrash bavk and forth on their splines and this will eventually cause *stepping* and wear on the splines leading to poor engagement and disengagement of the clutch and in extreme cases 'Creep' when the clutch is engaged at a standstill.

 

This thrashing is only really a problem at low engine speeds and is due to the 270/430 degree firing order of the V twin motor. For this reason it is unwise to set your idle speed low, (Guzzi recommend 1200RPM for a reason.) and likewise it is not good for the clutch componentry to sit at idle with the clutch pulled in. Another completely unrelated reason to keep the idle speed up is of course that the lower the crank speed the lower the oil pump speed. Set the idle really low and you may, in extreme circumstances, not have an adequate oil supply at idle to prevent boundary lubrication.

 

pete

 

 

Now that I think about it back in the eighties when a customers "cush" rubbers were worn and they were to cheap to pay for new ones we would just fill the space with some silicone - yeah tub & tile. Pop the drive back in, let it dry for a day and send them on their way. Never had any complaints.

I nominate Emry for a bodge point!

[Guest ratchethack]

Now that I think about it back in the eighties when a customers "cush" rubbers were worn and they were to cheap to pay for new ones we would just fill the space with some silicone - yeah tub & tile. Pop the drive back in, let it dry for a day and send them on their way. Never had any complaints.

Errr, I don't know what shop this was, Emry, and I have no idea wot kind of a Customer Satisfaction reputation it had, nor do I have any idea wot their return clientele rate was like. (Casting no aspersions, I notice that the Monster Mega Dealers hearabouts -- of which there are many -- don't seem to care in the slightest if a Service customer EVER comes back. The constant stream of newbie idiots coming in the front door with more money than brains clearly obliterates any concern wotosever over Customer Sat...) But let me just add an observation in the context of all this "advanced" discussion and cush drive material analysis:

 

I reckon I've run cases of various silicone sealants and adhesives through several cartridge guns on varieties of projects too numerous to mention. I've also used GE Silicone II sealant (yeah, tub & tile) on engine rebuilds in literally dozens of engine applications for 40 years, and still do, including on the Guzzi, but I seem to use most of it on household projects in and around the back porch, roofs, etc. The stuff was at one time pretty much an industry standard, general purpose sealant that you found everywhere, and as far as I know it still is. The local hardware always has it in stock every time I run out. Judging by the number of near-empty cartridges I accumulate by the caseload and haul to the recycler (again last weekend), I seem to go through a surprising amount of many grades of sealants. I've got a pretty fair idea of the nature of the stuff, how it works, and it's long-term durability.

 

I've also got a pretty fair assessment of the durability of the stock Guzzi cush drive rubbers after 34K miles and 3 years of hands-on inspection after drilling and lubing them.

 

Lemme just say this. If your shop filled up garden-variety '80's cush drives with GE Silicone II (or anything like it) and didn't get the customer back with a complaint within a few thou miles, I offer two possible explanations:

 

1. It's Grandma's scooter. She only rides it to church on Sundays. She's been riding it in first gear ever since 1982 because she's afraid of riding it over 10 mph, and she's still riding the same way today.

 

2. The rider was SO HORRIFIED at the resulting mayhem of the bodgery (I reckon it ain't pretty), he was permanently motivated to take his business elsewhere -- including a clean-out of the cush drive and installation of a proper cush drive at a higher price at a shop that would refuse to commit such bodgery.

 

D'you reckon Greg or Pete would put tub & tile sealant in a customer's cush drive -- no matter how poor & bedraggled the customer?

 

No offense intended, Emry -- Just an observation and perhaps a thought-provoking question.

 

EDIT: Here's a related and perhaps also thought-provoking Q for Dave along the same lines:

 

Hey Dave - D'you reckon either Greg or Pete would mix up 2-part urethane, pour THIS into a customer's cush drive, and send them merrily down the road?!

 

Just asking. . .

[OldButNotDead]

In the interest of being social and doing my bit for the community and thread....

 

You blithering eejit!

 

Blah blah blah. Blah blah blah blah. Blah blah blah blah blah.

 

I have vastly more experience and insight into this (and all other) topics and you have a distorted view of the essential nature of human beings and reside in a stupid part of the political spectrum. So piss off.

 

HAH!

[Guest ratchethack]

In the interest of being social and doing my bit for the community and thread....

 

You blithering eejit!

 

Blah blah blah. Blah blah blah blah. Blah blah blah blah blah.

 

I have vastly more experience and insight into this (and all other) topics and you have a distorted view of the essential nature of human beings and reside in a stupid part of the political spectrum. So piss off.

 

HAH!

Thanks for your highly enlightened contribution, OBND.

 

Your vastly greater experience and insight -- on this and all other topics, you say! -- has already elevated this particular discussion considerably!

 

The Forum has clearly been graced with an exceedingly rare example of magnanimity and selflessness via your analysis today.

 

Now in my blithering idiocy and distorted views of the essential nature of human beings, I have evidently fallen far short of your vastly superior perspectives, knowledge, wisdom -- oh yeah -- and politics too. How about opening up that vast (though I must say quite well hidden ) oceanic reserve of enlightenment a little, and straightening me out here by spreading some o' that heavenly anointed insight and experience around a little, eh?

 

This would no doubt be an enlightening experience for us all.

 

I beg of you, please do share something. One gleaming morsel of purely radiant, stellar magnificence. A tidbit. Pearls before swine. Scatter a few meager coins o' the realm in the dust for us peans. Anything at all. I'm sure that I, for one, would be MOST indebted. . .

[dlaing]

 

Hey Dave - D'you reckon either Greg or Pete would mix up 2-part urethane, pour THIS into a customer's cush drive, and send them merrily down the road?!

 

Just asking. . .

Nah, they are set in their ways and have made it clear they don't like urethane

Silicone has some excellent qualities that would make it ideal for job if it weren't so weak.

Urethane has most of those same qualities but is much stronger than the silicone.

I don't think any mechanic should do anything in a non-standard way without enlightening the customer to the pros and cons.

If the mechanic explained to the customer that the rubber pucks from Guzzi were mis-engineered and were as hard as chrome-moly steel, I think it would be an easy sell.

I would be about as upset from discovering drilled holes as I would be from globbed in silicone, assuming the bodge was holding up. But I don't think silicone would hold up to the pressure and it extrude off to the side.

I still think urethane is the ideal material and I would have faith that Pete or Greg would know what they were doing. It is not rocket science.

But as I have said, if the rubber pucks are as soft as Docc indicated and the rubber holds up with drilling as you have indicated, than the urethane would be a waste of time, and I'll probably drill it conservatively and fill it with silicone grease, assuming the gasket is not a friction disk.

Or I may just pull three deceleration pucks out and see how that improves things.

Keep in mind that the deceleration force max's out at wheel lock while the acceleration force max's out at about the point of popping a wheelie.

[Guest ratchethack]

If the mechanic explained to the customer that the rubber pucks from Guzzi were mis-engineered and were as hard as chrome-moly steel, I think it would be an easy sell.

Hmmmmm. Yes, quite. But then most riders I know of are at least sharp enough to know when someone is exaggerating to make a point, and tend to take a fairly dim view of service providers who would deliberately flat out lie bald face to make a such a meager sale (or any sale for that matter). . .

[docc]

It is not rocket science.

Ooh, I've been hoping Rockette Science would come up sooner or later . . .

[belfastguzzi]

Let's be serious now! It's obvious to me that y'all are missing the 800 lb. gorrilla in the corner!

 

If you mixed up a 2-part urethane compound and poured it into a mold

You're suggesting that we get rid of the rider?

Could make for less stress on the system right'nuff.

 

So, replace with urethane gnomes and use radio control?

 

 

(Must be edging up the Golden Fifteen page now, surely?)

[Guest ratchethack]

Or I may just pull three deceleration pucks out and see how that improves things.

Uh, oh.

 

Are you now, after all this, "going wobbly" on the Great Urethane Junk Science Experiment, Dave??

 

Please, PLEASE say it ain't so after all this! [. . .sob. . .]

 

You still have my offer to get you "over the hump" of all prior resistance to actually DO SOMETHING, Dave --

 

You will have noticed, however and of course, that my offer of service to remove the bolts for you is CONTINGENT upon you actually going through with what you've been justifying, presenting, explaining, promoting, defending, and of course (your apparent favorite) speculating about ad nauseum for nigh on to 15 pages!!!

 

You simply can't let us down NOW, Dave!

 

I'm NOT ASKING you to do this. No, indeed.

 

YOU'RE DOING IT! You've put a stake in the ground, man! You're committed!

 

YOU'VE JUST GOTTA DO IT NOW!

 

No renegging on this one, Dave.

[mike wilson]

You're suggesting that we get rid of the rider?

Could make for less stress on the system right'nuff.

 

So, replace with urethane gnomes and use radio control?

(Must be edging up the Golden Fifteen page now, surely?)

 

Don't call Ratchet surely. I'm (almost) positive he's male.

[Guest ratchethack]

Don't call Ratchet surely. I'm (almost) positive he's male.

By your combined grace, you must pardon us colonials, Guv'nah's.

 

We're such cloddish bumpkins, you know. Barbarians and rubes, really.

 

It seems that at least a few of us (meself included) aren't quite swift enough for UK humoUr. . .

[OldButNotDead]

Thanks for your highly enlightened contribution, OBND.....

 

...I beg of you, please do share something. One gleaming morsel of purely radiant, stellar magnificence. A tidbit. Pearls before swine. Scatter a few meager coins o' the realm in the dust for us peans. Anything at all. I'm sure that I, for one, would be MOST indebted. . .

 

Well, this IS embarrassing. I only posted to hear myself speak, and shot my ENTIRE WAD!!

Must...recharge...(gasp)....my...load. Please (gasp).....carry..on................without...me...(gasp).

 

Awwww, OK, here's some sharing before I go back to being useful - "peon" is one who walks (rather than rides); while "pean" is a hymn of praise.