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Buell Motorcycle Forum » Quick Board Archives » Archive through December 17, 2008 » "Rocket Science" and Keith Code « Previous Next »

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Aeholton
Posted on Friday, December 12, 2008 - 08:51 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Did any of you engineer types (or anyone with an opinion for that matter) read Keith Code's "Rocket Science" piece in the Jan 09 "Motorcyclist" magazine? Was his application of Newton's 3rd law accurate?
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Kilroy
Posted on Friday, December 12, 2008 - 12:02 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

What was his application of the law?
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Wolfridgerider
Posted on Friday, December 12, 2008 - 12:30 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

He was talking about foot pressure on the pegs and how the "For every action there is a equal and opposite reaction" did not hold true to motorcycle riding/racing.
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Xl1200r
Posted on Friday, December 12, 2008 - 12:46 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Well, without even reading the article, I can say with certaintly that every law of Physics ALWAYS holds true on a motorcycle, just as it does everything else.

I think it's more likely that, in regards to peg pressure, not all of the "action" or "reaction" are being taken in consideration.
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Aeholton
Posted on Friday, December 12, 2008 - 12:58 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

I hate to paraphrase, but I understood him to say peg pressure had little or no effect on steering. It was all due to steering head input and counter steering. I looked on the Motorcyclist Magazine website, but it doesn't appear to be on there (at least in the free access part).

Anyway, I just found it to be an interesting article and brought back some memories of a counter-steering thread here on Badweb. I remember some interesting points were made regarding peg input and shifting of weight.
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Xl1200r
Posted on Friday, December 12, 2008 - 02:09 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Peg pressue likely does have little to no input to steering given a)how close it is to the centerline of the bike, and b) putting more pressure on a peg does not mean any weight is being shifted.

Think of this way - ride with you feet hovering just above the pegs. Now ride with your ass just above the seat. Peg pressure when from 0% to 100%, and yet the center of mass for the bike didn't change.
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Swordsman
Posted on Friday, December 12, 2008 - 02:48 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Where's Tramp? He should be popping in any minute to explain how he rides using only telekinesis or something....


~SM
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Hexangler
Posted on Friday, December 12, 2008 - 03:24 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

I believe every input has some effect on the combined motorcycle-rider system.

For example, I notice that if I am riding at at 50mph or more, and I stick one knee out into the airstream, we (bike-rider) will drift from straight towards that direction. There are probably several factors even in this example: change of center of gravity, drag induced forces, balance of rider with new dynamic, etc.

Counter-steering has an obvious effect,
Foot pressure has a less obvious effect on the system, but it is still there.

Learning how to use every effect great and small comes with practice, perception, and intention.

I did not read the article, it would be nice to see it quoted or a hot link.
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P_squared
Posted on Friday, December 12, 2008 - 04:18 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

The main point he made was basically that the truth is there, but most folks understanding wasn't.

e.g. If you put 10 lbs. of force against a wall, the wall would in essence be reacting with 10 lbs. of force, thereby effectively cancelling out your action.

Same with weighting the pegs on a motorcycle. The weight of the bike (greater than the rider) is exerting an equal/near equal amount of reaction to your input, thereby effectively cancelling it for most purposes, thus why countersteering is the most effective means of steering.

I'm paraphrasing what he wrote, so don't flame me if you don't agree with it. I'm just trying to put it here for the general discussion of this topic so everyone has a common reference to what Keith was writing about in the referenced article.
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Hexangler
Posted on Friday, December 12, 2008 - 05:15 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

The motorcycle is a hinged system.

The main hinge is located at the steering head.

When you put force on the handle bar as in counter steering, the hinge changes position, and an effect on direction is the result.

When you put more weight on one foot peg, the hinge also changes position, and an effect on direction is the result.

Imagine how a motorcycle would handle with a rigid steering head.
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Krassh
Posted on Friday, December 12, 2008 - 07:27 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Hopefully not against policy to just post the article to help this discussion. If it is please remove. When I was reading this I recalled the body steering thread that Tramp was involved in.

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Aesquire
Posted on Friday, December 12, 2008 - 08:32 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

I only half agree with this far better rider.

I don't see the "desk presses back with a force of 10 lbs"

If you are pushing on an object that has more friction than your push can overcome, or is other ways blocked from moving, the resistance is coming from your other contact points with the object. or...

If you stand on a scale, and push down on a desk, it won't move, and the scale will show a reduction in weight...( figuring in the angles & such will give you a more accurate figure, but if you do it without slippage, parallel with the push etc.... a push down with 10 kilos force on the desk will reduce the scale reading by about 10 kilos. )

If you push forward evenly on both handlebars on a bike, the "reaction" is your butt on the saddle trying to go backwards. ( if you use armor all you may slide )

On a moving bike, sitting on the seat, pressing down on 1 footpeg means you are either shifting your weight or trying to torque the bike, or some combination.

I do agree that counter steering works, but with the snow storm outside, it will be a while before I can try little toe precision addition to my riding skill set, small as it is.
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Aeholton
Posted on Friday, December 12, 2008 - 10:45 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

When I was reading this I recalled the body steering thread that Tramp was involved in.

Me too. That's why I started this thread. This article confused me more than it helped.
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Slaughter
Posted on Friday, December 12, 2008 - 11:26 pm:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Peg weighting is a myth in that if you put an extra 20 pounds on that peg, that 20 pounds MUST be reacted back into the chassis, seat, bars... and unless you are twisting the frame, you have done nothing except to change your position slightly and THAT might have an effect. If your weighting the peg causes other unconscious effects then it will be the "peg weighting" that caused what you perceived.

Here is an old trick that will make you an absolute believer in countersteering.

Get going on a long straight road, no traffic around you. Take your left hand across to grip the throttle. NOW consciously THINK COUNTERSTEERING and the bike will respond. If you try anything else, you're going to feel like you're going to crash.

Try peg weighting, try body shifting on the same road and share your results with the group.

PERCEPTION of something is different than the ACTUAL CAUSE that produced the EFFECT. IF you FEEL that weighting the inside or outside peg can get the desired effect then feel free to continue to use it.

Meanwhile, carry on with the discussions of the peg weighting... it'll go nowhere (again) - you may as well argue religion(s).
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Hexangler
Posted on Saturday, December 13, 2008 - 12:55 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)



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Just_ziptab
Posted on Saturday, December 13, 2008 - 01:06 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Counter steering doesn't work at 3 mph. Counter steering doesn't work...... and then does works, at some point between 200 and 300 mph in a streamliner.......depending on the particular streamliner.......
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Slaughter
Posted on Saturday, December 13, 2008 - 10:41 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Zip - countersteering DOES work at some transitional speed down around 20-ish.

What Eric sketched out above is EXACTLY what I was attempting to state: there is a very real difference in the EFFECT of weight shifting (example 2 above) as compared to just pushing on the peg (example 3). Good free body diagrams.

Same net-effect of ZERO in example 2 if the rider just "presses" his knee or thigh against the tank. HOWEVER If his butt is off the seat, YES, he is pressing his knee on the tank but that is because he has shifted his weight and is "holding" himself with his knee.

(Message edited by slaughter on December 13, 2008)
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Babired
Posted on Tuesday, December 16, 2008 - 08:20 am:   Edit Post Delete Post View Post/Check IP Print Post    Move Post (Custodian/Admin Only)

Guys when I have a student who is having a problem with counter steering I ask them to simulate a large jet airplane that they have been in. Turning into the left in the air left wing is down and right wing is way up. Thanks for the article I was looking for it. When I was being interviewed for Stayin Safe MC training they actually teach the body and press steering as 2 other things you can do to help steer the bike. And when I teach MC safety to beginners I ask the students to roll on the throttle and let the throttle pull you out of the turn. Code say the throttle won't bring the bike back up, I would have been one of the 7 saying yes, this is confusing me now! K
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