longer cardan bar?

[sp838]

So, Rossopuro seem to have discontinued their beautiful billet cardan bar, I've been emailing them every three months or so to check in and every time they reply saying "sorry, not yet, hopefully soon, bla bla bla." In the meantime, I've been in touch with Ghezzi Brian, they still have their version of the cardan bar, which was part of the "Furia" package. For some reason though, they make theirs 10mm longer than the stock one. Curious to know what the opinions are on how this might affect the bike's geometry and handling. Would that raise the rear? Will it even fit? I have seen pics of it installed, so somehow I guess it does. Just makes me scratch my head, would like to get some thoughts on this.

 

Thanks!

[sp838]

According to Ghezzi Brian: "Hi sp, don't worry about the push rod, the longer lenght lets the transmission work better thanks to the different angle"

 

I'm sure they know what they're talking about (they designed and built the MGS-01 after all) but still would love to get some feedback on this.

[jwh20]

I assume your talking about a V11 model and this is what Guzzi calls a "reaction rod" in the V11 parts diagram...

 

If so, it seems to me that on the V11 a longer bar will force the rear gearbox to a different angle than originally designed.  As I understand the operation of a cardan shaft (i.e. the drive shaft) you want to keep the angles for the front and rear U-joints as close to the same as possible in order to get the smoothest power delivery to the rear wheel.  If one end is angled more than the other you will get uneven motion due to the un-matched U-joint motions.

 

But it also seems that with 10 cm of extra length you are going to push the angle past 0 degrees and end up with an additive effect of the motions and make for a very uneven rotation of the shaft.  It might be ride-able but probably will certainly add stress to the shaft, the transmission, and the rear gearbox.

 

I suppose you could get the longer shaft and have a local machine shop cut 10 cm out of it and weld it back together.  But for that cost you might even have a local machinist cut you one from a block of aluminum, titanium, or whatever your budget allows.

[sp838]

Not 10cm, 10mm.

[PhilPassmore]

I have just been and measured the rod on my Sporti (not sure how close it is to the V11). The standard rod measures pretty close to 410mm centre to centre, with the swinging arm being 400mm pivot to axle centres.

 

So already there is something about the geometry that takes it outside of being a simple parallelogram, and I can't imagine that another 10mm is going to make an enormous amount of difference. In fact, the differences in length may be something to do with the distances between the rod ends and the axle and pivot centres, I'm afraid I didn't measure that.

 

Making the rod longer won't have any effect on your ride height, what it will do is rotate the bevel box backwards slightly beyond what it is already. This MAY improve the way the two universal joints interact, I am not smart enough to figure that one out.

 

Phil

[jwh20]

Sorry, I guess I mis-read that mm vs. cm...  So the idea is the same, just not to the same degree.  The rod is intended to make a parallelogram and keep the two U-joints in the driveshaft at the same angle as the suspension goes up and down.  So this will change the angle by a bit and it may help slightly or hurt slightly.  My guess is that 10 mm will not be a significant change.

 

Now if you're just getting this to look cool, be sure you have a single-sided exhaust because on my bike the rod is almost impossible to see unless you get down on the ground. 

[Camn]

http://www.v11sport.de/forum/viewtopic.php?f=10&t=5706

(See the photos on the thread above), what can happen if there are "thin & lightweight" parts in the system. For normal safe street use with no extra checks with the reaction rod, I would not use any other than the original part.

[PhilPassmore]

I confess I have been thinking about making one for mysely out of some hex alu bar and a couple of heim joints.

 

Not sure how much I would have the bottle to machine it for lightness though.

 

Phil

[sp838]

yikes, that broken rossopuro bar incident looks scary. hard to say though if it's because of a flaw in the design, the installation was

done wrong, or just an unlucky and rare defect in the bolt that apparently snapped. rossopuro and ghezzi brian are both experts. i have a real hard time believing they make poorly engineered products, given their experience and pedigree working with guzzi bikes.

[jwh20]

That does look like an unlikely break.  I don't believe this part should be under anywhere near enough stress to break a bolt that way.  

[Bbennett]

I have had the Rossopurro reaction rod on my 2001 V11 for years with some reasonably heavy cornering both on and off the track - with no issues.

[Camn]

The owner of the broken reaction rod wrote that the bolt was M8. The bolts on the original Guzzi reaction rod were at first M10x59 (1,25 thread) and later M10x55 (1,5 thread), which is still available as spare part. Although the original reaction bar has rubber bushings; still there have been reports of broken bolts on this also. It could be, that on this ("M8") case the bolt had some kind of fault originally? I read that a M8 bolt has an inner thread diameter of 6,9 mm, and area of 38 sq mm. The pulls and bends when driving could be too much?

 

PS. "Pre fuel injuction" Daytona and Sport1100 had also a similar structure on the reaction bar like the broken one had.

[sp838]

Camn - hate to say it, but it looks and sounds to me like he installed it wrong.

 

Bbennett - is the length of the Rossopuro rod between pivot points the same as the stock one?

[Admin Jaap]

I have had the Rossopurro reaction rod on my 2001 V11 for years with some reasonably heavy cornering both on and off the track - with no issues.

Me too, No problems whatsoever

[grossohc]

I also have the rossopuro rod, have just changed the rose joints on them as i was getting some wear/play on them.

SP388 you can adjust the length by screwing in/ out the rose joints.