Laverda Crash Investigation

XBCoupeJota

XBCoupeJota

Full member
Location
Race Central - Sydney
I've started a thread on our race site about the investigation done on our bikes geometry to better understand the crash we had at the last round. We discovered some interesting insight and impacts on the bikes behaviour and have now benchmarked the setup from the crash, we probably never would have got to the level of detail we now have if it wasn't for the crash and are at a position where we can dial in different suspension and geometry options and see the impact on the Geometry, steering and braking forces.

http://www.ozlaverda.com/geometry-suspension-and-other-black-arts-t151.html

Cheers Crispin
 
I remember Steve B doing a rough and ready trail measure at the first Eastern Creek race,we had a little bet,I guessed 110mm.It was I think around 70mm really surprised me.Love the in depth analyser Crispin,much more interesting compared to who hates who or who's the biggest crybaby in Moto GP
 
Hey Cripsin

I see you have been reading the bible ............. ;)

http://www.tonyfoale.com/

                Cheers
                      Matt
 
Golgother said:
Hey Cripsin

I see you have been reading the bible ............. ;)

http://www.tonyfoale.com/

                 Cheers
                       Matt
Click to expand...

Hi Matt,

yes I now have his software for measuring and modelling our geometry and suspension setup. It's taken a while to get all the information together and figure out what's what, but now I can slot in another set of springs front or rear, raise or lower the suspension, change the swingarm etc and see the results. It will be invaluable moving forward.

Cheers Crispin
 
very, very interesting, Crispin. I forwarded this to a friend who is building Laverda 750 frames (Egli-Type). I guess he will like it, as it takes away a bit the guess work and brings in some really beneficial information.

Thanks for sharing, glad that there are people out there that do share these very interesting information with us. To many have the mentality of "I found out the hard way, why should I make it easier for others".

Great, thanks again!!

Lothar
 
Crispin, have you got any people experienced enough to help with analysis of your data? This is the stuff that all the top race teams spend endless hours poring over to find a tenth of a second here and there. At the level of a classic racer it should be easy enough for any experienced race tech to point you in the right direction (or up the garden path). There was someone in Sydney with a GMD frame analyser who helped lots of racers onto the right track, it was often reported on in AMCN.
From what I have learnt it seems like there is a hefty weight bias to the rear, making it hard to get enough load and heat into the front tyre. With the rider aboard that bias shows even more.
 
GMD was invented by a bloke in Sydney,there head office is in Sydney.There are franchises all over the world and lots owned by big time race teams but try and get a bike measured in Sydney and its not possible,or at lest when i was looking 5 years ago it couldn't be done.A mate had his GT Bevel done maybe 20 years ago.There are other systems around that do the same thing,what with all the 3D cloud point modelling,if you were any good with a Theodolite you could use that,but the latest gear is fantastically accurate.I ended up sorting my bike with 2 straight edges,a plumb bob, a spirit level and a tape.The wire wheels were out off the centre line by 7mm,I ended up offsetting the rear rim with the spokes.Going to be interesting to see what Crispin does to balance it up and how Blair rates the changes
 
thanks for sharing this Crispin

I have adjustable yokes on my 750 but TBH I have no idea how to set them up so will follow your progress with interest.

cheers John
 
Very impressed Crispin.
Instead of getting all despondent you have got stuck in to some serious work - root cause analysis.
I understand you have serious issues with limiting dive due to the weight of the machine, I take it some sort of anti-dive cannot be fitted? Money might have to be spent.

I remember that racing bikes of yesteryear went through a stage of smaller and smaller front wheels, then they went back to big ones - was it the decrease in trail that hindered them? 
 
Crispin,
From your comments about the locked front wheel I suspect you have already discovered the cause of the crash!
I did a lot of work setting up my spaceframe and discovered it was very sensitive to front ride height. In my experience there is no inherrent geometry problem with a spaceframe [your individual bike might be different of course], but a spaceframe can be very heavy on front tyres unlesss care is taken to establish the optimum front ride height.
My bike was a very sweet handling machine which could be turned in on the brakes and never displayed any tendency to lock or tuck under. I had a set of Cerianis on mine [the shorter ones from a 750] and a set of SFC 750 yokes, that's a known set-up which works well on the bike. The forks had a Maxton cartridge conversion.

Malloryspaceframe.jpg
 
I read this with interest firstly as a frame builder and secondly because I'm currently fitting 17's into a GS1000 post classic racer.

A couple of things come to mind - how does the rear shock length compare as regards Bob's bike - or any other spaceframe being raced ? the modern trend to jack up the rear to quicken the steering is easily carried too far IMO. The rake figure is extreme...particularly for the era the spaceframe was developed. IMO this would make the bike very sensitive to tyre construction - some of the modern radials have deliberately sacrificed self - centering ability in favour of quick steering. One modern racer friend had to sell off a seasons worth of new rubber when he found his bike weaved badly in a straight line on a particular brand.

The GS has 26 deg rake and over 140mm of trail on the std 19 in front - this is stable enough to get up and dance on the tank !
The trick is to retain sufficient stability with the frame as is once on 17's. With the increasing use of 17's on both race and road bikes made in the era when 18's were the standard these problems are becoming more common.

I'll follow your progress with interest.
 
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