Margo C-T you make some very good points, and these are all things you need to consider when building your own cart, or when you try to retrofit an existing cart. I've had some success with changing from the coik springs to "C" springs. Usually the coild springs will break at some point, and that's when you can most easily switch to the "C" springs. If you have or can make a flat surface to mount them to, its easy to just put them on the frame under the seat at the same place the coil springs were mounted. As far as springs for the seat go, I'm trying a new idea, repurposing school bus seat cushions. I drive a school but, and the company I drive for has a garage full of the cushions. They are 36" wide, very nicely upholstered,have good quality springs inside and also hace heavy duty foam. I figure if those cushions are comfortable enough to ride several hours on a field trip or even an hour or so to school, they are way better than most of the seats you get on a basic EE cart with 2" foam cushion. I'll come back on here to provide an update.
As far as the wheels are concerned, you are right on there too. The solid rubber tired wheels don't provide any cushioning, but I feel the trade off is the no flats, strength of wheel and looks of the wheels. Just my opinion, everyone is entitled to theirs.
I did have a cart that had the best suspension I've ever used, it had elliptical springs under the seat, one on each side, mounted lengthwise, You can get the cart from Fairview Country Sales, Millersburg OH. No website, but phone is 330-359-1501. Problem is, the smallest cart is pony size, and is too big for anything under about 36". They do have very nice wire wheels in a variety of sizes, and also list the flat-free inserts for pnuematic tires.
Building your own cart can be a lot of fun, and with some imagination you can find new solutions for some nagging problems, but can be frustrating, too.
