We are building our first cycle car. We have two trikes. We are using a cyclone body and are looking at a wheel base of about 6.5 to 7 ft. with some or all of the batteries in front of the front wheels for weight distribution. We plan to have a wheel track of about 36"-40". We are using 20" BMX wheels with 20mm axels. I have looked at many pix of cycle cars but can't see much or any camber on the front wheels. We have a narrow track on our trikes and have about 10deg camber on ther ear wheels to keep the cars upright on sharp turns. It has worked very well over the last three years. What are some of you using for camber on the front wheels? I see a lot of camber on the steering system but the wheels seem to be straignt up.
Almost everyone is using radiused bike front tires on the front. Caster has a much larger effect on steering then camber does, but they both do work together. We do not run suspension so, uneven control arm length is not an issue like it is on cars (it is the primary reason for tilting tires in (negative).
My best answer to you is to build a simple prototype of your design you want to use and turn it through its movement and see how things react. We did this for our current car being built and it was a lot easier to get it "right" the first time. There is a thread showing our wooden prototype, then the building of the front end.
Attached is a pic of one of the better handling cars in the NW.
Like Aaron was saying, It is alot easier to build a prototype first. I did that for my new steering system when I was designing it. I used it to figure out the angle of caster I needed. I just put it in a vise and tilted it. I built a second one build to the angle I found was best to measure the angles at smaller incriments. The thread is titled "over all steering design".
Vic, My two cents worth: Most of Willamette's cars are set up for short tight tracks and after building over 200 of them we have figured out some general guidelines that seem to work for us. We make the wheelbase shorter--45 to 58 inches. Then we have one battery in front of the axle and the other behind the driver. Our wheel track is about 45 to 47 inches wide (just inside the 48" max). We set our Caster between 5 and 25 degrees and our Camber is around 1 to 10 degrees. Also of course keep the center of gravity as close to the ground as possible.
The short wheel base allows us to turn like a sports car as opposed to a caddy. With the driver's butt as close to the front axle as possible this battery placement with the motor in the rear does a fairly good job of balancing the weight. The wide track makes us more stable on corners. If you have a large Caster (like my car's 25 degrees) then both tires will lean into the corner and you have better grip but it is a pain to get the steering geometry correct. Most of my kids cars are around 5 to 10 degrees of Caster which is fairly easy to work with the steering geometry. Since bike, moped, etc. bearings are meant to be used vertically we have found that if there is too much Camber the bearings tend to ride on the outside of the race and have a little more drag. (take same car-roll it down a ramp and see how far is goes--only change camber and check again.) We also looked at several sports cars and saw that most of them have 2 to 5 degrees of Camber. For the center of gravity if both batteries, the motor and the driver's butt are all 2 to 3 inches off of the ground then the center of gravity will be well below the axle height and there is no way to flip the car or pick up inside tires unless you clip a curb, other car, pot hole, etc.
If you want to go to a higher speed track with long straights and gentle corners--Then I would suggest that you lengthen the wheelbase to 6 to 7 feet like are talking about, use a small caster around 5 degrees and a small camber around 2 degrees. You can also make it narrower like you are planning on. You will not be turning tight corners and so will not need to dig into the corners or worry about rolling as much and you want it to roll in a straight line as well as possible.
Like Aaron said set up a prototype and check it out. Tack all of your frame and steering parts together test then make any adjustments/modification and test again. See what works best for your needs. I would love to hear what you find out. Mike
Thanks for the info. Along the lines we were thinking. Our two trikes will be our short track cars. The new car will be used on 1/4 mile oval tracks and some of our short courses. We plan do debut it at Five Flags in Pensacola in mid April. Its a 1/2 mile banked stock car track. We are also working on a course at the Florida State Fairgrounds for May where we can go with a long fast course. We are planning on role tests for all of our cars. We have a bus ramp just outside the Auto Shop that has an incline for a hundred yds or so. Kind of like the soap box derby.
One of the best ways to test for front end issues is to slowly roll the car on a tile floor over a sheet of paper. If it is dragging/binding when you are turning it will show up instantly.
