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Old Apr 13, 2004, 10:01 AM
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United States, AZ, Tucson
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Some R/C motorcycle questions

Hello,
I have a few R/C bike questions. In regards to the steering, how does that work? I am familiar with the steering of a real motorcycle, and bicycle too of course, how at speeds around 10~12 mph and lower, the wheel has to be turned in the direction you want to go. Then from 10~12 mph and higher the gyro effect takes over and counter steering takes effect. Does this hold true for these little guys? Do you set them up for traditional car steering, or do you set them up for the counter steering and just deal with the lower speeds?
Also, whats available now in this market, are those Kyosho road race motorcycles still around? Is there any "best" website that carries several brands?
thanx
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Old Apr 13, 2004, 10:15 AM
STeve B in NC
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North Carolina, USA
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They countersteer just like real bikes. It works well even at lower speeds, but it takes practice.

Try www.crazynutracing.com for bikes/parts. CNR now carries Thunder Tiger, Nuova Faor and Bergonzoni 1/5 bikes which are the most popular. The Kyosho bikes haven't been produced in a while, but can still be found (e-bay, etc.).

Steve B in NC
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Old Apr 13, 2004, 11:48 AM
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In order for the R/C bikes to stay upright and balanced there is a little play via springs on the steering servo. This allows the front end to reach equilibrium and maintain balance. Also, with small imperfections in the road the steering springs act like shock absorbers in a way. This is all without a “gyro”, in fact the rotation of the wheels generate most of the gyroscopic effect to keep the bikes up. So in essence you need a reasonable speed in order to keep the bike safely upright. If it falls, that's ok because there are wire loops on the sides to keep it propped up on the ground. There is just enough contact patch to get the bike righted again.

In order to initiate a lean (not the same as turning), the steering head turns the opposite way and the bike center of gravity is moved the other way. This is similar to real life however the rider also shifts the cg so you can flip the handlebars in the direction of lean immediately after you initiate the lean. “Leaning” is not the same as “turning” in this case. True the more you lean the bike the much tighter your turns can be however speed plays a big part. The slower the speed the tighter the turns and vice versa. This is what makes R/C bikes so difficult to control at first. But the frustrations are also the funnest part of driving them.

-Ian
RCMCC
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Old Apr 14, 2004, 06:35 AM
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Have a look at Graham Swallow's Steery Theory article reproduced in the Tech Tips section on rcbike.com at:

http://www.rcbike.com

click on 'Tech Tips'

Hope this helps.

kevin@rcbike.com
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Old May 03, 2004, 06:54 PM
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i'm not sure if this applies to you guys, but on a bicycle there is something called "fork trail" at work that is not mentioned in this article. the fork trail is the difference between two points on the ground. the first point is the spot on the ground that the head tube of the frame would point to, and the second point is directly beneath the front axle. that's part of why a bicycle is "naturally stable" as mr swallow puts it in his article, and why actual castors sometimes look like they are on backwards (if you are used to looking at bicycles all day like me). a longer trail increases stability by increasing the self correcting nature of the front end of the bike, and less trail is more responsive, but less stable over bumps for example. wheelbase, head tube angle, fork rake, and the gyroscopic effect of the wheels are all working at once along with the rider - or in this case the input from the servos via the remote.
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Old May 03, 2004, 10:35 PM
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Rake and Trail are also adjustable on most of the 1/5 bikes.
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Old May 03, 2004, 11:41 PM
STeve B in NC
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Quote:
Originally Posted by robbie
i'm not sure if this applies to you guys, but on a bicycle there is something called "fork trail" at work that is not mentioned in this article. the fork trail is the difference between two points on the ground. the first point is the spot on the ground that the head tube of the frame would point to, and the second point is directly beneath the front axle. that's part of why a bicycle is "naturally stable" as mr swallow puts it in his article, and why actual castors sometimes look like they are on backwards (if you are used to looking at bicycles all day like me). a longer trail increases stability by increasing the self correcting nature of the front end of the bike, and less trail is more responsive, but less stable over bumps for example. wheelbase, head tube angle, fork rake, and the gyroscopic effect of the wheels are all working at once along with the rider - or in this case the input from the servos via the remote.
Hey Robbie!

These 1/5 bikes have rake adjusters for the forks. They also have reversed triple clamps (fork tubes mounted relatively far behind the steering stem, which increases the effect of trail, relative to the fork rake. This makes the front ends very stable, but also leaves them able to respond quite well to transmitter imputs. (The rake can be adjusted to the point that the steering is very quick.) This helps overcome the liability of not having an actual rider on the bike, but just the ability to steer the front wheel.

STeve B in NC
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Old May 06, 2004, 03:38 PM
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Brno Turany, Czechoslovakia (former)
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page about steering theory

Hi Robbie,
look at this site : http://ist-socrates.berkeley.edu/~fa...eerBikeAJP.PDF It´s very interesting reading about steering theory.
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Old May 06, 2004, 03:55 PM
STeve B in NC
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Quote:
Originally Posted by aveox
Hi Robbie,
look at this site : http://ist-socrates.berkeley.edu/~fa...eerBikeAJP.PDF It´s very interesting reading about steering theory.
Yes that was some read. I especially liked the part that said, (slightly paraphrased):

"wIo\ + IsO =Ns- Mgb^ / L - Mbv2^ / L2 x o".

See, that's what I've been saying about countersteering all along!!

Steve B (mathmatically challenged) in NC
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Old May 06, 2004, 04:13 PM
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I don´t see what you can´t understand on this simple equation And now seriously. On the first page there is very good explain of steery theory. Really.
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Old May 09, 2004, 04:13 AM
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Noord-Holland
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Hi guys,

I'm now making my fifth bike. The first ones were made from wood, now I moved to aluminum. My bikes always steered by moving the battery pack from side to side, this always worked great! But now I see everyone steers by "turning the steer". This is easier to make than a system which swings the pack and it also allows an easier body fitting. But I now have some troubles steering, when I pushe the bike forward it falls . So now I made the link between the servo and the steer even more flexible. Now it stays upright, but I think it will not steer because there is too much flex in the steering. I can now move the front wheel to the left and the right with ease (by hand )...is that the amount of flex required? The bike is about 1:8 scale so also less stable (I think), any suggestions to make it better?

Thanks, Luuk
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Old May 09, 2004, 06:31 AM
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Quote:
Originally Posted by boss
Hi guys,

I'm now making my fifth bike. The first ones were made from wood, now I moved to aluminum. My bikes always steered by moving the battery pack from side to side, this always worked great! But now I see everyone steers by "turning the steer". This is easier to make than a system which swings the pack and it also allows an easier body fitting. But I now have some troubles steering, when I pushe the bike forward it falls . So now I made the link between the servo and the steer even more flexible. Now it stays upright, but I think it will not steer because there is too much flex in the steering. I can now move the front wheel to the left and the right with ease (by hand )...is that the amount of flex required? The bike is about 1:8 scale so also less stable (I think), any suggestions to make it better?

Thanks, Luuk
Luuk,

Steering a bike with the servo through the springy suspension on the servo arm should be just the right tension, you may need to experiment with this until you have it just right.

It took a little while for me to understand this for a bike because I too was accustomed to the method of weight (battery) or (rider) shifting to turn the bike, but making an analogy to the way a helicopter is controlled, which I am very familiar with, it became clear to me why the direct servo to steering colum method is preferred.

In my opinion, the steering on an RC bike is not relly direct though, but indirect, since it has to go through some damping of just the right resistance or tension (spring or fuel tubing couplers) for smooth controlled steeering. In analogy to helicopters, it would be the servos through the swashplate to the flybar paddles to steer, where the Hiller paddles (of course this has to do with correct weight size and distance fron the center of the flybar) are actually providing the steering damping and is why we are able to control RC helicopters with greater ease. On the bike you also have to have good suspension and this is also a factor which only by trial and error one can arrive at Just the right feel for control.

Hope this makes sence. Great to hear someone else likes making stuff from scratch.
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Last edited by Mario; May 09, 2004 at 06:52 AM.
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Old May 09, 2004, 02:08 PM
STeve B in NC
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Actually we are not "steering" the bikes, but leaning them. Boss, make sure you have your servo controls set up reversed, i.e. to turn the bike to the left, the servo should turn the front wheel to the right, so the bike leans and subsequently turns left.

any pics?

HTH

STeve B in NC
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Old May 10, 2004, 05:00 AM
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Noord-Holland
Joined Dec 2003
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thanks for all the help!

I tried the bike and it goes quite well, not as good as the previous ones but I still have to try it on a flat surface . Yes I first hadn't the controls reversed...but after some fresh thinking I got it right. I'm going to try it on tarmac now...but first the picture...Yes those are LiPo's .

Hope to tell you about a good run later .

Luuk
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Old May 10, 2004, 05:13 AM
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Noord-Holland
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Well, the motor did quite well. But the topspeed is to low and I need better tires. I now use plastic ones around wich I glued rubber from a bicycles inner tyre. This gives me a very hard tyre so there is no suspension in the tyre. Has anyone ever made their own tyres? I tried many things but most didn't work well.

Luuk
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