My RI Shock snapped tonight

[davidblythe]

Not impressed, doing usual mad mile testing

thought i had a blowout, bike is all over the place, front brake only slowly to a halt

tyre is okay, hub is still on

lift the rear end of GP and it keeps lifting

R1 Shock has snapped at the top mount

more crap to add the lambretta pile

[Dazza]

David, following on from your experience and the other stories here:http://scooterotica.org/forum/viewtopic.php?f=7&t=3547

Mine is coming off and being replaced with an Escorts standard jobby before i ride it again

[Andy Pickering]

This is a bit of a worry as I have 1 in the shed waiting for adaptation to lambretta..?

[soullad]

David, glad to hear you Ok.
Im convinced the conversions, by engineering principles, are wrong.

[tony]

I think if they can handle the forces an R1 puts through them then the fitting is somehow at fault.

[davidblythe]

I think if they can handle the forces an R1 puts through them then the fitting is somehow at fault.

had one shock snap on a 250 superdream in the early 80's, never had another one snap in 28 years of continious daily riding

fitted as supplied with the brass bushes, been on for the last 2 years

strangely the shock doesnt have so much unsprung weight to cope with on a R1

have seen other makes of shock snap on Lammies, so am interested to know and find out where the issue is

all advice welcome

[soullad]

as has been posted before, the link below are my experiences after delving abit deeper.

http://scooterotica.org/forum/viewtopic.php?f=7&t=3547

The current conversions do not allow for any rotational stress to be absorbed, which in turn acts on the central rod. In ours cases to the point of failure.
The rear of the lambretta engine will follow a circular course when it is forced to dampen, as it is pivot fixed by the engine mounts. In atraditional shock set-up this is absorbed by the rubber mounts which flex within their housings.
The current conversions only allow linear damping due to their fixed solid mounts. It is probably testament to the R1's great build quality that they have been able to withstand such forces in such numbers.......but for how long?
There is also the issue of the sideways movement caused by the fitting of the smaller springs which im sure just increases the above stresses.

[joespeed]

try this fit the shocker to the engine ,tighten with washer fitted and check if it can swing freely if it cant fix it! then try the same on the frame,
if you fit something on a lambretta that is a 'force fit' then it will bust sooner rather than later,this simple rule applies to anything that vibrates,
my early learning of the lambretta exhaust was riving it onto the studs ,bashing it on with the knobbly style hammer (the sort you see in comics) was a sure recipy for disaster ,the exhaust fell off i ran over it and my little brother fell off and broke his arm ,yes i got a clip round the ear of my mam!
be warned!
regards
joe

[tony]

I think if they can handle the forces an R1 puts through them then the fitting is somehow at fault.

strangely the shock doesnt have so much unsprung weight to cope with on a R1

yes I agree.. static unsprung weight that is. However I dont know the maths but whats a say 'shock' with say 20kg at 60mph compared to say 5kg at 170mph? My guess is the difference is massive. Also the loading a 130hp bike can put through it compared to a 20hp lambretta is massive. It has to be the fitting. Its putting stress in an area it wasnt designed for...ie the 'solid' mounting.

[davidblythe]

agree Tony, thinking it through, the solid mounting is the problem area, the rotional forces are acting across the strut due to lockdown and not as they should be translated through/down the strut

just got to find a solution