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The "no Bs" Bike - A Scientific Tool!


John Culbert
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Keith,

 

Your recent article on using the No BS bike to explore what attitude changes occur as a result of throttle control is very significant.

 

I have read a great deal about damping curves, bending forces, modula of elasticity, etc., but this bike - along with your gritted teeth - will show people things they can use.

 

It'll show you why Kaz Yoshima's dinky little suspension-travel indicators work, and will probably let you pick tire sizes and profiles absent superstition on the subject - but there is something else to be noticed in the use of the No BS platform: body position has real effect.

 

Over the years, there has been what I consider unnecessary friction between body-steering and bar-steering fans. It's clear that both principles apply to riding.

 

Well, where's the confusion?

Those I have spoken to are at a loss when I mention a common engineering term: mass coupling. See, if a mass is not rigidly attached in a system, then, when it is accelerated, the center of gravity of that system will move proportional to the acceleration; the direction the center of gravity moves will also not be constant. The rider is certainly elastic; further, (s)he intentionally moves around on the bike.

 

You know very well that on the dragstrip, 60-foot times are critical, and that truly tiny adjustments in the rider's routine will affect the bike drastically. I submit that the same is true in roadracing.

 

In judo, the position of the hands and feet are critical to the outcome prior to any force being applied to one's opponent. On the track, your position on the pavement presents a limited number of options for forward progress. It is only logical that your position on the bike produces small changes which have large consequences for upcoming control input and the resulting action of the bike.

 

The No BS will show all of that, and lay argument aside for reason! Excellent!

 

By the way - you won't get me to take my hands off the real bars!

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  • 2 weeks later...

OK, John, I'll bite.

 

I could only find limited information on Kaz Yoshima's dinky suspension indicators (Ontario Stick?), and not that sure how it relates to the No BS experiment that Keith was performing (Instalment #1). Unless the No BS Bike has these things fitted?

 

Friction between Body-Steering and Bar(Counter?)-Steering? In Australia we don't seem to have this problem. Searched the internet again (40+ Google pages) and there is not a solid definition for Body-Steering, but, I do have some things to try on the track this Saturday so we can save this for a new topic. If someone can give me a good link on Body-Steering before Saturday, I'd appreciate it.

 

Mass coupling? Sorry, I'm not an engineer. I know that when I'm riding, I can affect the center of gravity by using throttle, brakes, steering and body position (ie: hook turn).

 

Sorry, I don't know anything about the dragstrip racing or judo either (other than its better watching these sports with a nice cold beer, in front of a big TV) B)

 

What I think your alluding to is (correct me if I've got it wrong); That body position has a greater effect on the motorcycle than what most people would realise or appreciate?

Ever had a pillion on the back of your bike? Ever had a *bad* pillion on the back of your bike? What did they do, other than breath? They move around on the bike! As the pilot, you can easily feel the changes in the bikes stability and control, even when they only make the slightest of movement (a change in body position). If you've ever had a pillion, they'll know what I mean. If you haven't had a pillion before, all you need is to get a victim. :lol:

 

I rode the "No BS" bike, just over two years ago in the car park at Laguna. Now that was an eye opener! :blink:

 

Looking forward to reading Keith's next instalment of his "NO BS Bike Experiments". Maybe its Will's turn? :ph34r:

 

Cheers!

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  • 5 weeks later...

In my younger riding years, I remember thinking that I could actually change lanes by throwing my hips to the side I wanted to move to and that my bike responded. I truely believed that you could turn the bike by body position alone.

 

I also remember when I got on the No BS bike at CSS/Watkins Glen, I just KNEW I could turn it with body position. I won't spoil it for anyone who is planning on trying the No BS bike this season but it is a very convincing training tool for the uninitiated.

 

Kevin Kane

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Not for me to steal Keith's thunder but I think the essence of the Body Steering drill is to demonstrate that very little, if any useful change in direction is achievable by shifting body weight alone. Sure you can arc the thing around with a turn radius of scores if not hundreds of feet, but that's not much use at Pocono etc.

 

The judo analogy I think is closer to the power/pivot steering drill and is exactly that- setting up for the most efficient postion to push the bars without getting upset by the re-action.

 

I'm no engineer but I know that's Newton's Third Law of Motion at work. Everywhere you go- erudite Englishmen.

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  • 5 months later...

Just remember - you weigh half what the bike does. Of course body position matters for all direction changes. My major point is that the rigidity of the elastic part of the man/machine pair - you, the rider - is drastically affected by how you are seated and how you weight pegs and bars. "First motion" of any bike component, around any axis, depends on how much mass resists accelerative force via inertia. This has immediate and gross effects on handling.

 

I don't know where to find the article, but Kevin Cameron wrote a few pages on this.

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  • 2 weeks later...

oh oh, is this another CS vs BS thread?

 

This ground has been covered well and many times and what riders think they are doing and what is actually happening aren't always the same. By the same token, the physics masters don't always get it right either.

 

I respect Kevin Cameron for many of his good works, his description of spark and combustion is one of the true pieces of poetry in the mechanical world. However, a decade or so ago he wrote an article in Cycle magazine where he stated that there must be a sharp counter, countersteering action to stop the roll-in momentum.

 

In other words, he was saying the bike would just continue to fall into the corner if the rider didn't counter the roll-in that he produced from his countersteering. That is of course a completely false statement but it was consistant with his understanding of the phenomena at the time. I wrote him a note on that and I'm sure he has it straight now.

 

Now I hear that one of Reggie Pridmore's group has put together a bike that shows how BS works and I can't wait to see it.

 

Keith

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