Laverda 1000/1200/ Jota braced swing arm

sideshow

sideshow

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I am looking at  modifying a swing arm with bracing.  Does any one have any drawings or dimensions etc so that I can do this locally rather than go through the pain of shipping of the swing arm to someone who will take several months to do the job?

I don?t want to change the wheel adjusters or anything like that, it?s just the bracing that I would like to do 

Any help given is much appreciated

 
Hi,
question is what would you like to modify.
The Laverda swinging arm is relatively stif and as how the swinging arm is integrated in the frame it is a classic triangular static system. Almost no bending forces in the swinging arm.
Regarding sidewords forces you could do some embracement but it is really not necessary, for twisting forces you could close the box between the bearing tube and the plate behind.
Regarding my experience it is not necessary as the Laverdas do not have a problem whit h a weak swinging arm.
 

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Perhaps worth noting that the two rear axle supporting sections of the RGS swing arm are rectangular, and not round, as used on the earlier triples.  Was this because of an inherent weakness in the earlier swing arm?
 
Big improvements in fitting modern tyres and setting up the suspension properly. I ride my 1974 3c pretty hard with the standard swingarm, and it?s carrying enough weight for 2 up, no weakness found. I?m 112 kg, Vince is about the same weight, no problems with swingarm, don?t mention spokes........
 
More to be gained by extra bracing on the swingarm pivot area on the frame.
 
sideshow said:
I am looking at  modifying a swing arm with bracing.  Does any one have any drawings or dimensions etc so that I can do this locally rather than go through the pain of shipping of the swing arm to someone who will take several months to do the job?

I don?t want to change the wheel adjusters or anything like that, it?s just the bracing that I would like to do 

Any help given is much appreciated
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112kgs, I wish. If the swingarm was weak, you would be lots of wallowing in fast corners. With even relatively cheap Icon shocks, this is easily dialled out. But braced swingarm look sexy as hell
 
tom3c75 said:
Perhaps worth noting that the two rear axle supporting sections of the RGS swing arm are rectangular, and not round, as used on the earlier triples.  Was this because of an inherent weakness in the earlier swing arm?
Click to expand...

Reckon this was a fashion statement, more than anything else.  EVERYBODY wanted box swingarms back then.  I remember Massimo describing the alloy 1000SFC swingarm as "only for spectacle", ie, totally needless from an engineering point of view!

The original swingarm has no inherant weaknesses in its intended role, if everything else is in order.  I have seen swingarms broken at the axle mount due to collapsed wheel bearing spacers, allowing the wheel assembly to wobble and bend the wheel mounting plates.  750SFCs had the lower shock mounts moved aft of the axle, perhaps to reduce forces acting on the plates?  But, that's for racing, the SFC plates were also of thicker section than the cooking models iIrc.

I've never felt the need for any strengthening of the stock twin or triple swingarm, an underslung brace only adds to the hassle of renewing chains.  Chain run and exhaust clearances need to be carefully considered when adding bracing.

piet
 
Interesting thread this is. when I first got my jota back in 84 its handling was a shock having come from a Ducati 750 Sport, basically its didn't go round corners.
I contacted Windy Corner and told them of my problem and they suggested one of their braces swinging arms in conjunction with a Kawasaki steering damper.
Long story short, swing arm and steering damper were ordered and duly fitted.  These two items transformed the handling 101%. I'm now on my 3rd swing arm, this being a JMC item and I find it perfect. Now I know that some say a braced swing arm makes no difference by my experience says otherwise.  Ya pays your money, ya makes your choice!
 
RCGBOB44 said:
Interesting thread this is. when I first got my jota back in 84 its handling was a shock having come from a Ducati 750 Sport, basically its didn't go round corners.
I contacted Windy Corner and told them of my problem and they suggested one of their braces swinging arms in conjunction with a Kawasaki steering damper.
Long story short, swing arm and steering damper were ordered and duly fitted.  These two items transformed the handling 101%. I'm now on my 3rd swing arm, this being a JMC item and I find it perfect. Now I know that some say a braced swing arm makes no difference by my experience says otherwise.  Ya pays your money, ya makes your choice!
Click to expand...

Having made two changes (any others not mentioned? Like different shocks?) it's impossible to identify the handling issues as swingarm-related. Unless the new swingarm fitted altered the geometry of the bike I personally can see nothing there that would suddenly make the bike go round corners. Definitely not doubting you experienced and improvement, but casting doubt on the source of the fix.

You can't compare the Laverda swingarms (twin and triple) with what was being offered on Japanese bikes that definitely had flex issues back in the day.
 
Looking at the massive swing arms on modern bikes makes me wonder how stiff our old steel tube swingers are. They look quite puny in comparison.

The thing that put me off building a stiffer swing arm was talking to someone who fitted a massively stiff braced alloy swinger to his Laverda triple, and he said he couldn't notice any difference. The memory is a bit vague now as to who it was I spoke to, but it was someone I respected as a capable rider who would be well able to assess the benefit, or lack thereof. It might have been Ants Carberry with his 1200, but there was probably alcohol involved so I can't be sure.
 
Modern bikes can have to cope with 180+hp and lean angles that our old clunkers probably can't, then there's the super-wide tyres.

I wouldn't have fitted a different swinger to the SFQ had I not needed extra length to compensate for a steeper front end and reduced wheelbase.
 
Modern MotoGP bike chassis have become so stiff that a certain amount of flex needs to be introduced in certain areas to regain traction and feedback for the rider.  Don't know how much of this technology is transferred to road bikes, maybe electronic traction control devices are simply a lot cheaper...

piet
 
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