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View Full Version : What kind of freaky physics was this?



Cynos
29th October 2007, 15:56
So, here's the scenario. I live down a gravel road, and they have recently reshingled it. I was riding home on Friday night, it was dark, and that light, greasy rain that sticks to visors really well started falling just as I hit the gravel.

I was trying to pick the tyre tracks in the gravel, when my visibility got too bad because of the rain on my visor.

As I was raising my visor with my left hand, my bike suddenly leant to the right. I thought I was going to be thrown, and then I was expecting to have the bike fall sideways underneath me. Out of instinct I put my right leg down, and that stopped the bike, although it hurt like buggery.

But then, the bike, which was still learning greatly over to the right, leapt back to the left, and once again I thought I was going to be thrown. Just as the bike was leaning enough to the left for me to think that I was going to be dropped, it went back to the right. It oscillated like this two - three more times. but always had more lean to the right than to the left.

All this time I had my right hand on the accelerator, I can't recall what I did with it, and I'm not sure when my left hand made it back to handlebars. I was still trailing my right foot when it straightened out.

Now, I'm pretty sure it happened because of the gravel, but what I'm not sure of is what happened precisely to cause the initial slip, and why it oscillated like that. Perhaps I was subconsciously increasing throttle?

Also, during this I had an instinctive thought of "don't let go of the throttle" - was that smart or stupid?

I've attached an MSPaint diagram of the motion of the bike as viewed from head-on, black bits are tyre, red bit is fiery redhead riding the bike.

Has this happened to anyone else? I just want to minimise my risks if it happens again, as the gravel is a perpetual issue until I move.

DUCATI*HARD
29th October 2007, 16:32
gravel plus unbalanced rider with throttle on =wobble:devil2:

Mikkel
29th October 2007, 17:24
Mood swings? They can be induced by rain I've been told...

jrandom
29th October 2007, 17:30
The rear was spinning, hooking up, then spinning again? If you'd buttoned off the throttle when it stepped out like that, it probably would have thrown you off.

Well done on keeping it upright.

Next time try steering into it and see if you can get a photogenic 'backing it in' slide going ;)

Cynos
30th October 2007, 10:49
The rear was spinning, hooking up, then spinning again?

That was the thought I had last night, that as the bike keeled over, perhaps it was digging through the gravel and biting somehow...

Moral of the story is - ride a three wheeler.

Conquiztador
30th October 2007, 20:55
More throttle and you would have straightened up straight away. Not sure where you would have ended up but...

You are in the middle of what the car tyres have left as track in the gravel. Sort of like a U shaped track. Front wheel goes towards one side, back wheel towards other, then rear grabs and they swap, front beacuse you steer, back beacuse the spinning. More throttle and you would have straighetend her up. But as you had no idea what was ahead I recon the best thing was to try and cut down speed and try to get controll.

Well done. Instinctive.

If in doubt, rev the shit outta her.