Ta
Oh, i makes a difference alright. Dunno about on a bucket, but the chair wheel is taking insane pressure on right hand turns on a full size.Originally Posted by Pumba
Something with a nice stiff sidewall, and plenty of grip. Don't go too wide though, the drag Will just slow you down.
In the riders seat
To much grip on the side can promote understeer on rights, although pumping up the tyre more can fix that
"If you can make black marks on a straight from the time you turn out of a corner until the braking point of the next turn, then you have enough power."
Hardcore Biker
Or move the wheel forward. That would probably take care of it.
I think trying to decrease the grip available of a loaded tyre to cure understeer is a pretty silly notion. You aren't gaining that grip back anywhere, you are just losing overall grip.
I do often wonder what geometry I would go for if I built a chair. And the conclusion I am at is that I would go for a 33:33:33 weight distribution in right handers and a 50:50:0 in left handers (No weight on sidecar wheel). So the centre of gravity of pilot, swinger and rig would be directly in the middle of the two main wheels (longitudinally) and the the sidecar wheel would be half way between the front and rear wheel. This way the sidecar wheel wouldn't contribute to yaw moments (That is what causes understeer or oversteer) and would take its share of the weight around right handers which would maximise overall grip (It would also ensure all tyres want the same slip angle as they are under the same load. As a consequence the steering inputs and yaw rates would be equal left to right which would give a balanced feel. Although it would still have higher corner speed on right handers due to better load distribution across the tyres.
I would absolutely use kart wheels because they are light and cheap. There is no point adding yaw inertia for no reason with big wheels. Suspension on all 3 corners, not for the track surface, but to achieve some camber gain in corners. In simple terms this stops the tyre from wanting to roll out from under the rim. And some good caster on the front wheel. Again this gains some camber on turn in and through the corner.
Track width would be maximum and wheelbase would be minimum to decrease load transfer to/from the sidecar wheel and decrease yaw inertia and yaw damping respectively.
And aero. As much downforce as the little engine will push. Around mount welly where the straights may as well be part of a double apex corner I think you could get away with heaps.
This is all just my own musings and I may be missing half of the plot with not having actually driven one of these things. I have had a swing but was far too busy holding on to worry about the dynamics of it.
Some tyre stuff:
http://en.wikipedia.org/wiki/Slip_angle
http://en.wikipedia.org/wiki/Tire_load_sensitivity
elbow down dreamer
Posted some chair photos from the weekend in my photo thread:
http://www.kiwibiker.co.nz/forums/sh...post1130583865
In the riders seat
Oh fuck I wonder if everyone racing a sidecar everywhere in the world knows they're getting it wrong
"If you can make black marks on a straight from the time you turn out of a corner until the braking point of the next turn, then you have enough power."
Hardcore Biker
Just talking about buckets here.
I don't know the rules for full sized chairs and they would have a rearward weight bias and a need for stability at high speed and longitudinal acceleration. But a bucket chair works under different conditions, and some rule of thumb, while I think it would work, is not necessarily the best option. If you have the option of A: Reducing understeer by decreasing overall grip. or B: Changing the design so that it does not understeer and retain the same amount of grip. Which would you choose?
There is no need to have the sidecar wheel behind the centre of gravity on a bucket chair, so why do it? Why throw grip away on over inflated tyres.
I could draw you a picture if you like.
Race it don't store it !
the the sidecar wheel would be half way between the front and rear wheel. This way the sidecar wheel wouldn't contribute to yaw moments ..
Lots of rules to read before you start your build Moooooools ..
Hardcore Biker
I have done my reading.
That is within rules.
...The sidecar wheel axle shall be between the rear wheel axle and the middle point of the wheelbase.
Also there are a grand total of 7 rules regarding bucket sidecars. Sweet fuck all.
Hardcore Biker
Hey Pumba love your thread. We must be real racers now with terms like yaw and understeer and people worried about side grip and weight distribution.
Funny thing is the sidecar that's still dominating was welded together on a concrete floor without a jig and and receieved negative comments about it on another thread and it runs an underpowered chinese engine. Either the original builder struck the right formula for building a bucket sidecar from years of experience or the rider and swinger on that one are just to good for the rest of us.
Ta
A certain amount of slide, is quite optimal from the rear and chair wheels on a sidecar. You are riding scaled down versions of what we ride, I would think that would remain constant.
Trying to power out of a right hand turn, the chair wheel is fighting the front. You can toe it in to all fuck to combat this, but that creates drag and slows you down on the straight. To combat this, some negative camber helps, but doesn't completely sort the issue. It can also upset things in braking for the turn.
On a short chair, which is what you are sorta working with, slide it into a right and slide it out of a left.
Easy to fall into this trap. Andy (Scrivy) and Steve (Sidecarbob) are several times NZ1 on sidecars. They're chair is inferior to many out there, and nearly all the long chairs. Yet there it was, a huge 1 on the front of the bike.Hey Pumba love your thread. We must be real racers now with terms like yaw and understeer and people worried about side grip and weight distribution.
Funny thing is the sidecar that's still dominating was welded together on a concrete floor without a jig and and receieved negative comments about it on another thread and it runs an underpowered chinese engine. Either the original builder struck the right formula for building a bucket sidecar from years of experience or the rider and swinger on that one are just to good for the rest of us.
The riders can make more of a difference on an uncompetitive chair, than is the case with solo bikes.
Who You Calling a Pig
Hahaha Warren, my Mrs would say it is more about me over analysing everything and being an anal prick. My interpretation of it is wanting as much opinion and fact that I can muster before spending as little as possible to get maximum result (tight I am).Hey Pumba love your thread. We must be real racers now with terms like yaw and understeer and people worried about side grip and weight distribution.
Funny thing is the sidecar that's still dominating was welded together on a concrete floor without a jig and and receieved negative comments about it on another thread and it runs an underpowered chinese engine. Either the original builder struck the right formula for building a bucket sidecar from years of experience or the rider and swinger on that one are just to good for the rest of us.
Not sure if the formula for that particular chair is just that good, the only thing I do know is that the rider and swing are competitive pricks, and a little mad to boot.
For the record Qkkid was in my bed, not the other way round
Hardcore Biker
Hey Pumba got another idea, we should weigh our rigs and use which ever is heavier as a minimum weight rule. That'll slow them down. My mate still bags me for selling that rig doh doh.
In the riders seat
There shouldn't be,it should be on Spikes
Yes they did a great job of beating so caller superior chairs but only up to the point the guy on the long chair learnt to ride it properly, then barring mechanical failure it was winning and breaking lap records every time it went out
"If you can make black marks on a straight from the time you turn out of a corner until the braking point of the next turn, then you have enough power."
Ta
Not now. I mean back when they were winning.
Hardcore Biker
Sliding to an extent can be good for a number of reasons. One is to induce an increased slip angle in the rear tyres, and will result in the lateral grip being higher provided that the tyre wants all that slip angle, and the other is to counteract anti-yaw moments and this understeer.
The easiest way to think about this is that the chair has to both move around the corner in an arc, and rotate however many degrees at the same time say 180* for a hairpin. These are separate events (although they affect each other). When you enter a corner the front wheel leads with a force (because you steer it in) and this starts to turn the rig faster and faster. By mid corner the rear tyre has caught up (it always does) and is producing the same amount of force as the rear then the rig is rotating at a constant speed. And then the pilot removes his steering input and the rear tyre is providing more force than the front so the rig decreases it's speed of rotation. This is all just a moment balance game. see: http://en.wikipedia.org/wiki/Moment_(physics)
So the phenomenon of understeer is the front tyre doing not enough work or the rear doing too much, which means the rig will not rotate quickly enough to sustain adequate slip angle on the tyres. And oversteer is the exact opposite.
I have yet to mention the sidecar wheel in all this. Simply put it will just act like a front or rear wheel depending on whether it is in front or behind the centre of gravity of the rig. If the wheel is right at the rear axle you should find that the vehicle has very little understeer on turn in but lots of it mid corner. As you move it forward this understeer decreases until the wheel is inline with the CoG. At this point if the tyre produces any lateral force it acts directly through the centre of gravity and as such cannot rotate the rig. So it effectively has no effect on oversteer or understeer of the rig but can still contribute fully to lateral accelerations.
Taking this a bit further, the sidecar wheel will now have too much slip angle mid corner. However there are no rules against steering the sidecar wheel on a bucket so you may as well link it up to steer a small percentage of the front wheel.
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