On a cycle car putting on rear suspension is simple but I know on mountain bikes when they have shocks on the back wheel you loose power. How does this affect electrathons? Will it loose power, or since it is all flat it will just make the ride more comfortable without loosing power.
All suspensions cost a small amount of power, the question is how much you are willing to sacrifice for comfort.....
I have been racing electrathon for 11 years now and have never had a suspension.... Mike Hodgert (pres. electrathon America) from Willamette High has been racing near 20 years without suspension... and he has a bad back... and out here in the pacific northwest we have some pretty rough tracks.
We have found that seat design can be a much better "shock absorber" than wasting the weight & energy loss of suspensions.
Why does a suspension on a mountain bike cost energy? My guess would be that when the rider pumped the pedals, some of the motion would compress the rear suspension rather than force the pedal down (and the bike forward). The dampener (which is misleadingly called the 'shock absorber') absorbs that energy and releases it as heat.
In an electrathon vehicle, the only equivalent might be when abrupt acceleration causing weight transfer to the rear and thus compress the rear suspension. I expect the amount of energy would be negligible.
i think the real trade off is this: A effective rear suspension will allow the driver to carry speed through a tight corner that might require a throttle lift without a suspension, but building a vehicle with a suspension will be slightly heavier than no suspension.
So, a well designed light weight suspension could have worth on tight bumpy tracks.
Hi all,
Long-time lurker, first-time poster.
Ryan, the reason to use suspension on any two or three wheeled vehicle is to keep the tyre connected to the road surface for longer, and to keep the amount of load on the tyre as constant as possible. If you don't have suspension and run over something that upsets the wheel, it will elevate easier and jump around more than with no suspension, and a tyre above the ground doesn't give any grip. Suspension helps to keep some grip on the vehicle corner whenever the vehicle is "upset" by cornering or running over bumps/objects etc.
This is true for one, two or three-wheeled vehicles. A unicycle rests on it's wheel and needs forward and sideward balance to stay upright, a bicycle needs sidewards balance, a dicycle (like a Segway) needs forwards balance, and a tricycle needs none, as it naturally rests on it's three prongs!
A four-wheeled vehicle, however, is "over-constrained". If you raise a wheel on a quadricycle without suspension, you have to raise two wheels! Pick up the rear left on a go-kart, and you either pick up both rear wheels, or both left wheels. To keep all wheels working together, you therefore need some suspension on a four-wheel vehicle, otherwise at least one wheel is always superfluous. This suspension can include tyre deformation (like a go kart) or a mechanical linkage system.
For Electrathon, a cycle car with or without suspension have the same cornering capability. It's just as to whether undulations and/or driver smoothness are going to cause it to lose traction often, where a well-designed suspension system will help the car settle faster. I would suggest not worrying about it for a cycle car.
Brendon, all the way from Australia...I agree with you. I do not see a need for much if any suspension with a cycle car or tricycle. I have seen rubber bushings used on the axle mounts so that they dampen the bounce a little but not enough to cause an outward lean on corners or any other item that student suspensions often have trouble with. I you are just worried about driver comfort make you seat a hammock style so that the seat itself absorbs most of the bounce. then you can pad the top and bottom tubes that support the seat so that you are totally suspended and not touching any hard surfaces. I have that and we race on several tracks with large bumps and potholes and I seldom feel discomfort from them.
it is always good to hear other people's experience but I am confused. You wrote:
If you don't have suspension and run over something that upsets the wheel, it will elevate easier and jump around more than with no suspension, and a tyre above the ground doesn't give any grip.
But then you say:
For Electrathon, a cycle car with or without suspension have the same cornering capability.
If a vehicle loses grip, it's cornering capability is less. So with suspension, the vehicle should have more cornering capability.
There should be an advantage running a well designed suspension on a bumpy track. On the other hand, would a team get more advantage using the resources (time and money) that designing, building and testing the suspension would require on other aspects of the car? Quite possibly.
Hi gents,
There's definitely design criteria that can be combined or assessed seperately, and that's whether you're creating suspension for the driver's comfort, or for performance of the vehicle package. A cycle car that inherently balances itself on it's three wheels will get upset by a bump on the course, particularly while cornering, but will always come back to rest on all three wheels. Unless it flips. Oh dear.
Rubber bushings within the steering axis is a pretty good idea; this allows a little spring and damping in the direction that is needed (known as wheel compliance), while still keeping the steering inherently stiff. Very ideal, as you don't want bumps altering your steering angle! And, it's very easy to design; all you need is a slightly larger kingpin bushing.
Sorry for the confusion Cliff; let me try to explain that a little better.
Tyre grip, and hence cornering and tractive (Braking and accelerating) capacity, is proportional to the amount of vertical load on the tyre. If the tyre is in the air, it can't help turn the car, which is pretty obvious. When the tyre doesn't have much downwards pressure on it, though, it also can't impart it's normal amount of loads to turn or slow/speed the car up either. It's best to get the tyres settled as quickly as possible, which is where performance suspension comes in. And, if you can trade-off some vehicle drag, perhaps wings to create downforce would increase the forces available too!
For the second statement, for a cycle car that is cornering at it's full capacity and doing no braking or accelerating, virtually all of the load is on the outside wheel, with the rear wheel only holding it's share of the mass distribution. Suspension doesn't matter here, as suspension that isn't moving (called it's "steady state") has the same properties as a rigid system. It's when a bump comes along, that a non-suspended system will bounce, while a well-designed suspension system will still bounce, but will return to it's steady state sooner and grip sooner too. So yes, the absolute cornering capacity of cars with identical track, wheelbase, mass, center of gravity and aerodynamic package should be the same, but a well-designed suspension car will hold more of it's possible cornering, braking and acceleration forces for longer.
Hope that clarifies!
Ryan,
In a simple statement that you can Google the meanings for:
If you design a rear suspension and drivetrain system that has the chain line parallel to the line between the suspension instant center and the rear axle, you will have no suspension movement under acceleration. That just might set you on your way
It is important to dig a little deeper into what the suspension does. It is not just about vertical load, but also about optimizing the way the tire meets the road.
Think of it this way. When we design a fixed suspension, we have to choose a setting for tire camber and toe. As a general rule, zero camber gives the lowest rolling resistance and negative camber on the outside wheel improves cornering grip. So a fixed tire camber setting will be a compromise, sacrificing either efficiency or cornering.
A properly designed suspension moves in a way that changes the camber in the corner. Done properly, you end up with the best of both worlds, zero camber on the straights and for the corners, negative camber on the outside wheel and positive on the inside wheel.
Hi Cliff,
Oh absolutely, I'm oversimplifying quite a bit with this. The one-dimensional model, where you only look at the tyre adhesion and forces imparted, is too simple to use to effectively design front suspension on a cycle car, but it's relatively useful for rear suspension for the same vehicle, or whenever you have a single-track axles (front and rear wheels on a bike, front wheel on a rear-steer delta etc). Damping and spring rates can be analysed with known linkage ratios (and estimated tyre spring/damping/inertance rates) to have a close approximation of the system.
A swinging arm imparts an arc motion to the rear axle relative to the chassis, but the horizontal change in distance is relatively negligible for the short suspension travel that would be required for Electrathon cars. And, unless rear wheel steering is also designed in, the rear wheel and suspension setup is typically assumed to be rigid laterally, so the 1D model works relatively well for the rear suspension.
Suspension on steered, dual-track wheels, though? A whole different world. Particularly with the relative lateral flexibility in bicycle wheels, there would be many compromises to be made! Electrathon chassis with their side impact structures certainly lend themselves well to double wishbone implementation to enable camber-gaining geometries...
