how long can a f2 chain run be before its too long

[steve-e]

Brian stop worrying As long as it doesn't hit the back of your neck it will be fine

[Bob B]

Typical passenger view of all things mechanical

[Thundersport Syd]

On the subject of long chains...

We were parked next to a world endurance team several years ago when my Steve raced, I noticed their R1's had rather large front and rear sprockets, so I inquired to the team manager about it. He told me it improved BHP and torque delivery to the back wheel by reducing drag created by what he likened to trying to turn back a bullet fired from a gun and of course, the sharper angle turned, the more power lost and intimated it to be be the same with a fast traveling chain.

I decided to embark along this route in the usual pursuit of 'an edge' for my rider and you know he was right, but only up to a point. Using a dyno, I tried various combinations of sprocket sizes, but once the sprockets got over a certain size, it became obvious that the drag created by the centrifugal weight of the extra long chain required, actually began to drain the advantage gained by the larger sprockets.

I did definitely find a 'Goldilocks' (that's where it's 'just right') situation, that won me a significant power enhancement over my competitors though. Warning: I had to modify the engine casing to take the sizable front sprockets I needed to make this work.

I don't suppose this is much good to an F1 machine, as they seem to constantly spin up the back wheel with ease thereby losing any advantage gained anyway, but it occurs to me that with a lower powered machine like a 600cc or less sidecar (and also be warned, you could write what I know about sidecars on the back of a postage stamp) that has to pull two bodies around the circuit, one may indeed redeem even more fruitful benefits than I enjoyed with a solo.

Just a thought and probably been covered on here BS (that's 'Before Syd').

[Lumley32]

syd when you did the testing did you have the same drive ratio each time?

[Thundersport Syd]

Yes, or near as I could anyway. As I recall, I think one particular combination was half a tooth out is all, but it was a very interesting exercise and no one ever out dragged our bikes after that.

It put me into new territory with regard to chain slack though, I had to detach the rear shock, jack the chassis up and bring the drive sprocket, swing arm fulcrum and rear spindle into line to set that correctly each time we went to a new circuit with the new configuration and needed to change the ratios to suit.

It also created slightly more centrifugal and gyroscopic weight forces that I had to dial out via the low speed compression and rebound on the rear suspension, with about 2ml extra sag in the end too, but nothing really insurmountable. I don’t know how that would affect an outfit quite honestly, different forces involved I guess…

Had to have the sprockets made though, they weren't available off the shelf, I seem to remember them thinking I was rather mad at the time!

(probably was then and most definitely am now! )

Syd

[powerhouse]

Ok steve I get the subtle hint I'll shutup taxi