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SlowLearner

Joined:

Feb 10

Posts: 1953

SlowLearner says:

Tight turns / U-turns at speed

Comrades - here's an interesting demonstration of some tight turns being taken at a lively pace:

http://www.youtube.com/watch?v=4B9L5XkPr0A

Note that this guy isn't working it all through the back brake, revving hard and slipping the clutch - this is all done through locking and leaning.

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  • Posted 3 years ago (30 January 2012 02:52)

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Amateurcynic

Joined:

Jun 09

Posts: 1050

Amateurcynic says:

Think this

Is a demo' of the new third directive mod1, the mod 2 will be even harder, don't forget you'll need to do this at least 3 times on different bikes to get a full licence!!??:blink:

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bbstrikesagain

Joined:

Nov 08

Posts: 879

spot the

dinner plate rear sprocket, riser bars, crash bars, not your average CBR600RR...


Not your average rider either, but he is working both brakes all the way...

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philehidiot

Joined:

Feb 09

Posts: 4758

philehidiot says:

Yeh

Motorcycle gymkhana. Bike set up for it and also a competition.


It's a difficult ride on the road and also you need a nice surface.

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SlowLearner

Joined:

Feb 10

Posts: 1953

SlowLearner says:

Missing the point maybe

Yeah, I get it that this isn't a standard bike or rider, but look at what he's doing compared with the way many instructors insist U-turns should be done.

Nearly all tutorials say you feather the clutch, work the back brake, keep the revs disproportionately high for the speed.

I've even been personally told by an advanced trainer, that the gyroscope effect of the engine at high revs is what stops the bike falling over.  (Actually, he was confused and said the action of the pistons going up and down vertically is what kept the bike up, but I understood the principal to which he was trying to refer.)

Seems to me like that's not likely - the bike wants to fall out of the curve by the substantial force of the tight corner - made very tight by the lock with the lean, almost like trying to fall over immediately on one side or the other.   It's only the power being pretty harshly applied, a twist of the head and handlebars that stops that happening .  It's balanced between fall in/ fall out by the substantial lean - even while going relatively slowly.   Fall into the corner, power and straighten out.  Not exactly in the standard texts.

If it was all due to the gyroscope effect of the engine, you would have the exact same effect making it a problem to change to any new direction at all while revving hard!

To get a very, very tight turn it's the three L's - Look, Lock & Lean.

Anyone disagree?   I'd like to be straight on this.

.

[Edit note:  Wrote "than" instead of "that".  Expanded a point.]

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philehidiot

Joined:

Feb 09

Posts: 4758

philehidiot says:

You want

to learn how to turn like this?


Bear in mind these guys are in a race and therefore on the extreme limit of what they/the bike can do. Trying to emulate this level will lead to you doing what they do all year round - falling off.

The basics of turning fast at low speed include getting the lean on to counter the centrifugal force (yeh yeh, only present in the area in which is is being observed and in the rotating region of observation, and whatever other physics gubbins I HATE... f**k y'all!). The lean you're looking for is to get your shoulder by the mirror - you're not just moving a head, it's got to be the entire body weight. Do this and you'll be amazed at how quickly you can turn at low speeds.

I don't believe the clutch is employed when you are increasing these speeds but the back brake defo is used. He may be using the front brake but that seems like it's asking for trouble and as above - it takes a lot of bike dropping practice to get these things right.

The gyroscopic effect from opening up the throttle would be useful I suppose if you feel you're going over. Pulling the clutch in might help but then you'll lose speed to two of three gyroscopes, increasing only one. If you've an open space and you feel you're going over, I'd say opening the throttle slightly whilst making your position neutral is probably the way to go. But I dunno, I've not tried it.

The downside is tyre warmth at this time of year - don't bother pushing it unless you have confidence in your tyres to grip. The other bike related issue is to consider the type of bike you have. Clip ons do not work properly. A supermoto is the best kind of bike to learn this on.

So really for the basic effect just turn with a lot more lean - move towards the mirrors. You'll see if turns faster and easier at low speeds. Then you can increase the speed and get tight turns at higher speeds. Use the back brake to settle the bike and finely moderate the speed. You will hit the limit if you push it and I suggest if you want to practice this then you either protect yourself and your bike or get a second set of jacket / trousers and a second bike.

There may also be motorcycle gymkhana training going in in your area - the IAM people may also know someone.

If anyone thinks the advice I've given here is bollocks, please correct me as this is only from playing around myself and not proper training.

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bbstrikesagain

Joined:

Nov 08

Posts: 879

Look, Lock, Lean?

Or maybe Look, Countersteer (as the thing has to fall in fast) and Collect (before it hits the deck, and with just enough grip left that you can steer in to flick it back out again) - no good pulling a 65° lean only to lose the front trying to flip it back up...

PS this is just observation, not advice or recommendation!

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SlowLearner

Joined:

Feb 10

Posts: 1953

SlowLearner says:

Turns

philehidiot:  Brilliant stuff, thanks - that's exactly the sort of explanation I was looking for.  Nice one.  I'm not expecting to get to do the sort of thing in the video, but hoped that something could be learned from what that dude's doing.  Obviously you don't start out like that from day 1, you've got to start slower and keep pushing it a bit.

And as you say, this is crap weather right now - roads are greasy as could be.

bbstrikesagain:  I don't think he's doing any counter-steering, the speed is too slow,  surely positive steering is what he's doing (to the point of a lock half the time)?



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bbstrikesagain

Joined:

Nov 08

Posts: 879

SlowLearner

It is all about countersteering.  The guy wants big left lean from straight ahead.  The ONLY way to get that, and get it quick, is to push the line between his the contact patches well off to the right, out from under the centre of gravity of the bike and rider so that they can start to fall.

The actual fall, or build up of lean, is achieved by gravity alone, but if you don't countersteer you don't let it happen.

When there's enough lean he smoothly catches the fall by steering the front back in to push the bike around.

To exit the turn he has to lift it up again - that means steering tighter to bring the contact patches in to push the bike back up.  The harder he's leaning and cornering, the less spare grip there is for this, so again it's about knowing how much will work.

The basics of the countersteering can be safely explored on a bicycle, preferably a mountain bike on grass - this I would dare to recommend. Braking and power are secondary.

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James600zx

Joined:

Sep 07

Posts: 2821

James600zx says:

SlowLearner,

I think the balancing effect of the engine gyro comes to the fore at low speed where the wheels are contributing less. If a learner could launch into a full lock, rapid 180 in the street and pull it off safely I expect it would be a pass, but since that's unlikely to happen we are all taught to slip the clutch, use the back brake, keep the revs high and creep round.

I've been curious about this gyroscopic effect too. The thread below has some amusing examples of riderless bikes keeping upright.

http://www.motorcyclenews.com/MCN/community/Forums/Categories/Topic/?&topic-id=423996
 
I think when Phil leans head and shoulder toward the inside mirror he's putting weight on that side but more importantly he's positioning arms and shoulders in such a position relative to the centre line of the bike that he's pulling on the outer bar and pushing on the inner one, ie: initiating a turn with counter-steering. If you're sitting in an office chair with arm rests, grip the rests and lean your body to one side. Now remove one hand and feel what the other arm is doing, pushing, or pulling. Works for me. Now I just have to explain to my colleagues what the hell I'm doing!

(Blimey, I've been trying to submit this post since yesterday. I tried multiple times from work and home, and also tried submitting a dot and then editing which has finally worked after several attempts. Strangely, I was able to post "test dots" to other categories without problem. I've now deleted those. MCN, this is a poor show when you're offering a forum for discussion  and your business is publishing!)

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philehidiot

Joined:

Feb 09

Posts: 4758

philehidiot says:

I doubt

he is likely to be any counter steering. Speeds are too low to require it and this is a different type of cornering to that done in the twisties. Doing even 10mph is fast at those cornering angles and I doubt most people counter steer at 10mph - 15mph.


Counter steering precipitates lean. In this the required lean can be achieved without the aid of counter steering. You can just turn the bars as long as you are in a position to counter the spinny outy forces generated by shifting sufficient weight and the centre of mass inwards. You do not have to counter steer if this can be shifted sufficiently without. At higher speeds it also rolls the bike onto the side of the tyre but really doing this at the basic level it's not an issue as you won't get that far over. 

I suppose it's possible he is using it but we'd be able to tell by the front wheel wiggling before the turn in. Anyone who can be arsed looking, feel free. Let me be clear though - you do not have to counter steer to pull this off at a basic level and I would recommend against it as it's just stressing your front tyre even more.

EDIT: makes sense me counter steering when moving body but I make a conscious effort with the steering so I doubt I am unless I'm doing it before hand and not noticing. It's not something I do this time of year - I'm a slow pootler when it's cold and even slower on these new bastard tyres!

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