Messages

121

VMX Sidecars / Re: Classic Dirt 7 Queensland 2010

« on: June 18, 2010, 10:32:17 PM »

Made the cam at home from start to finish, it is made from billet 4340 steel, with adjustable sproket.
Ignition is off the shelf unit made by PROBE Indudtries in the states.

This is the cam 'rough ground' before it was stress relieved.

122

VMX Sidecars / Re: Classic Dirt 7 Queensland 2010

« on: June 18, 2010, 09:29:14 AM »

Wasp,
Moving the crank around 3 splines is a common and simple way of doing it, works out to be 83.08degrees and apparently works quite well.
To get 90degree, u need 2x #2flywheel (centre left) and a special double ended centre shaft (and a small amount of machining) to get the magic number.
Chuck the #3 flywheel in the bin, as well as the other 3 flywheels from the donor crank

123

VMX Sidecars / Re: Classic Dirt 7 Queensland 2010

« on: June 17, 2010, 10:42:04 PM »

I do not like to rev engines hard. I prefer to grab another gear and let the torque do the work, much the same as the way you use the longstroke GRM power. Reducing vibration should not be confused with reducing 'grunt'.

124

VMX Sidecars / Re: Classic Dirt 7 Queensland 2010

« on: June 17, 2010, 09:34:18 PM »

Geoff was the throttle man, but that thing sounds like no XS I've ever heard. In all seriousness it would be a real treat to record that engine noise in much the same manner as the H16 F1 car from 1949. if you get a chance drop over to YouTube and have a listen to the clip of pink floyds drummers car at  a track in England and you will get the idea. The exhaust note from that chair is by far one of the best I have ever heard.

Gday Bahnsy, I do totally agree about the sound of that XS engine. I asked EML about it and he said the firing order had been changed and the 2 cylinders fire like a big single. It sounded awesome.

Stan.

Thanks for the nice comments lads,

Heres a bit of info on the engine:
The firing order has been changed, however it doesn't fire as a single.
Instead of firing every 360'degrees, (parallel twin 4 stroke), it fires 270'-450'-270'-450'degrees and so on.
The right hand crankpin is 90'degrees ahead of the left one.
This is the same firing offset as a 90degree V-twin (ducati, good noise), but instead of the cylinders being 90degrees apart, the crank is.

The main objective of this was to reduce vibration, which it has done significantly.
It has turned it into a really smooth reving engine with loads of torque, and the traction is amazing due to the un-even firing pulse going through the back wheel.

Matt.

125

VMX Sidecars / Re: Classic Dirt 7 Queensland 2010

« on: June 17, 2010, 08:52:37 AM »

For the people that diddn't hang around till the last chair session on Sunday, u missed an audio delight. One of the chairs was described as sounding like "a sprintcar" don't know what it was or what was done to it but I reckon you would have heard the sweet noise from Brisbane. The noise alone made me want to have a crack at riding it!

I think that mite have been sidecar legend Geoff Udy in the last session having a spin on my XS Yamaha powered Wasp replica 

126

General Discussion / Re: Classic Dirt 7

« on: June 16, 2010, 09:22:55 AM »

Great photo's, looks like u guys had a ball. anyone get any  pics of the sidecars?
Cheers.

127

General Discussion / Re: Classic Dirt 7

« on: June 15, 2010, 04:02:31 PM »

David#46, is that fact or a suposition??

I think it may have been a question but just forgot the '?'   ?