What does CARC refer to?

[brider]

I see this everywhere, searched under "CARC meaning", and it looks like NOBODY asked this question. Must be a really dumb one, but I'm askin' it anyway.

[Tusayan]

'Cardano Reattivo Compatto' - Compact Reactive Driveshaft

I think use of the acronym CARC, and writing it on the bike, was a symptom of Aprilia's cartoonish scooter marketing mentality but I'm sure it made the bike more appealing to those who might otherwise have bought Suzuki's SRAD 

[fotoguzzi]

It’s the style of rear drive on late models with single sided swing arm.

[pyoungbl]

CARC is the Guzzi version of the BMW bevel box where a reaction arm keeps the rear from rising/falling with addition/reduction of power.  Earlier shaft drive systems were noted for the rear rising as power was applied.  The Guzzi version has been generally trouble free whereas the BMW box....well, I would not own one.

[Tusayan]

CARC is the Guzzi version of the BMW bevel box where a reaction arm keeps the rear from rising/falling with addition/reduction of power.  Earlier shaft drive systems were noted for the rear rising as power was applied. 

Guzzi's first such system was introduced on the Daytona in 1993, the CARC setup was the second iteration.

[Chuck in Indiana]

Clanks And Rattles Continuously 

[PJPR01]

Surely someone at Guzzi had a sense of humour when coming up with the CARC acronym as a hidden recognition of the contributions of Carcano (Giulio Cesare Carcano -  engineer with Guzzi from 1936 to 1966, inventor of the DOHC V8 engine and the air-cooled V-twin that became synonymous with Moto Guzzi)

[Orange Guzzi]

It is a acronym and a modified version of the  Parallelogrammo swingarm patented by Magni.   It separates the rear gear box from the swingarm.  The wheel moves up and down instead of an arc because of the "torque arm" attached to the frame.  This arm prevents the wheel from driving under the motorcycle and causing the rear of the drive shaft driven bike from rising when the throttle is opened. 

There are various versions and they have been used on other Brands besides Moto Guzzi.  Including Kawasaki.  It works great.  I have a the original Magni version on my Tonti framed bike.  The bike will squat down under hard acceleration going straight or coming out of a corner.  They do require maintenance because of the many moving parts.  I spay chain lube on the moving parts and grease the drive shaft u-joints regularly. 

[HarveyMushman]

Clanks And Rattles Continuously 

I like that one.

[kidsmoke]

[Kiwi_Roy]

Thanks for the cutaway.
As I understand it the cylinder shape in the driveshaft is some sort of shock absorber?

It certainly does Clank & Rattle at low speed.

[normzone]

My thanks to all of you for the answer to a question I nearly asked at the rally this weekend.

I say "nearly", because the volume of valuable and arcane information being offered all around me was so interesting that I knew if I asked that question I'd get all of the above in a similar manner, and my data intake buffers were already set to max and getting warm.

Nice user friendly explanations, which is an art in itself.     

[Bonaventure]

That cut away picture, the innards look pretty stout to me.  I'd like to think it's one of the better engineered motorcycle shaft drive setups. 

[pete roper]

Thanks for the cutaway.
As I understand it the cylinder shape in the driveshaft is some sort of shock absorber?

It certainly does Clank & Rattle at low speed.

While it appears that the shaft is a single piece it is in fact an inner shaft and an outer 'Tube' for want of a better word. In between the two there is some sort of synthetic rubber material that bonds the two together which acts as the driveline shock absorber.

As for the clanking? This affects earlier bikes mainly and can be improved by fitting a later type, more forgiving, silentbloc bushing at the front of the reaction arm. Another thing that AIDS on/off throttle smoothness is ensuring that there is the absolute bare minimum of free play in the throttle cables.

Needless to say, if your bike is poorly tuned and your throttle body balance is all over the shop nothing you do will improve its rattling and knocking! I have to say that I can go from negative to positive throttle on both my Griso and Stelvio at below 2,000rpm without touching the clutch in lower gears as long as I'm careful and sympathetic and it rattle and clanketh not!

Pete

[bad Chad]

Me too! 

And it's superior in all meaningful ways to the BMW design.

[Sasquatch Jim]

 And I thought it was an expression used by owners when they found chunks in the rear drive oil.
  CARK!

[ohiorider]

Yes .... but CARC is gone, and Paralever is still in use by BMW.  My 1991 R100GS with Paralever has been soldiering on for the past 155,000 miles (not km.)  It appears to be a more fragile design than the CARC, since the final drive 'pumpkin' itself floats on bearings and pivot pins, whereas Guzzi does their magic internally.  Paralever was first introduced on BMWs in 1988, on their R100GS of that year.  In the USA, the 1990 model K1 was the first 'modern' BMW to be equipped with the Paralever.  They (R100GS) did experience driveshaft problems, typically U joint.  Some didn't make it to 30,000 miles before requiring drive shaft replacement.  Mine didn't fail until 122,000 miles.  A BMW Forum member referred me to a shop in Wisconsin that could replace the U joints.  So far so good.  33,000 miles on the repaired driveshaft.  It may be time to pull it and have it inspected by an experienced BMW mechanic, since these shafts can get out of phase.  The front and rear halves of the shaft are joined by some sort of non replaceable rubber coupling, and after 26 years of use, it's probably time to replace the entire shaft.

Bob

[Huzo]

  The wheel moves up and down instead of an arc because of the "torque arm" attached to the frame. 

I don't want to start an argument, but does that need a re think ?
The distance between the swingarm pivot and the rear axle centre is constant, so the axle would travel in an arc.
No ?

[Sasquatch Jim]

 No.

[brider]

OK, THIS is what has been bothering me about this acronym: Posts like THIS  one, where the discussion has nothing to do with drivetrains, but uses CARC liberally:

 
CARC: Riding Through Wintertime, Should I Concern About Oil Over Cooling?

[ITSec]

OK, THIS is what has been bothering me about this acronym: Posts like THIS  one, where the discussion has nothing to do with drivetrains, but uses CARC liberally:

 
CARC: Riding Through Wintertime, Should I Concern About Oil Over Cooling?

Understandable to a degree, but pretty much everyone (including the technically minded) refers to the class of 1100/1200 cc bikes with the single side swingarm as CARCs. It's reasonable to ask a question about the class and its shared characteristics by using the term.

[Huzo]

No.

Well I guess I must be wrong...
We'll see.
Can you bring an explanation to the table ?
See, I'm a bit vague on this stuff, but I'd have thought... For the wheel to be travelling vertically, the distance from the axle to the awingarm pivot would have to decrease as the swingarm reached horizontal and then lengthen again as it took up an angle upon rebound.
How'm I doing ?

[Huzo]

Also CARC
Concern About Rear Carnage !

[beetle]

First rule of CARC: Do not talk about CARC.

Huzo, shaddup!

 

[pete roper]

Nah, you're right. The CARC system isn't like the earlier Egli system, nor is it like the BMW system, although the principle used to negate the torque reaction is the same.

One of the nice things about it is that because the entire reactive bridge is supported in what are effectively the wheel bearings as the suspension moves and the reactive forces act upon the bridge it simply speeds up and slows down the rotation of the bearings minutely.

Unlike the earlier systems there isn't a sliding coupling on the shaft that can lead to the trunnions of the driveshaft being misaligned. The front yoke is retained on the output shaft by a circlip and the length difference created by the reactive movement and suspension travel is catered for by the rear yoke sliding on the pinion shaft.

Problems with the CARC bevel box and driveline are rare. The commonest ones being the pinion nut dumping its preload. If this happens and the bike continues to be ridden it will destroy the crown wheel and pinion in very short order. If caught early it is an easy fix and the component can be saved. It happened to mine on the Griso in Sydney and I rode it back to Bungendore. I only noticed when I rolled off the throttle and it H-O-W-L-E-D like a banshee! I nearly shat meself! Luckily because it had been under load virtually the whole trip when I took the box to bits the CW&P looked fine. The problem is of course that the CARC is supposed to be 'Unrepairable'  :roll eyes: and therefore you can't buy the peg nut and lock washer to repair it.

Only of course you can, because the peg nut and lock washer are exactly the same parts as the lock nut and peg washer used to hold the crank sprocket on to the front of the crank on a T3/LeMans/SP 1000 so you just buy them, clean everything up, install the new washer and nut, (With some green 'You're never bloody coming off again you bastard' Loctite.) and just torque it to the industry standard for this sort of application which is 60-80 inch pounds. Bend the locking tab up on the washer, reassemble it, reinstall it and fill it with oil and see if it sounds like cats screwing on the over run or not! Mine has done 30,000km since I McGyvered this repair and its still going strong and silent.

Pete

[Huzo]

First rule of CARC: Do not talk about CARC.

Huzo, shaddup!

 

Now you've done it !
Wheel moves vertically or in a minute arc ?

[beetle]

Alright, you asked for it.

As the suspension compresses, force is applied to the skookum dinkus, which rotates obversely to the moment of inertia to the frannistan. Thusly, the applied torque is reduced inversely proportionate to the uplift return arm tension. Therefore, a balance is acquired.

Simples!

[pete roper]

You forgot that there is often a goat involved......

[nc43bsa]

60-80 INCH-pounds?

[pete roper]

60-80 INCH-pounds?

Yes, the bearings are pre-loaded by a collapsible spacer rather than a solid spacer system as used on earlier designs.

Pete