I think we took the fabric and wood bit off the pram, and attached the seat to the springs. I believe it was one of those discarded fiberglass chairs . We then dubbed it X-15, and shot it off down a hill. Steered by slowing the wheels with friction from your shoe. I don't seem to recall us using any such washers, here in the States . That carriage was still around when I went to Uni, then shoved on the recycling truck when my nephew left it in front of the house one day, I was told in a letter. I've had a carriage undercarriage shaped hole in my life ever since.