Flick of the Bic
Take apart some Bic lighters and scavange the flintwheels. Ditch the thumb wheel part, you'll need the width. Mount the flintwheels to the rear axle behind the rear wheels.
Depending on the chassis used, you can mount a flint holding bracket to the gear clamp or rear screw post with some minor brass fab. Like a reverse wheelie bar that holds the flints to the flintwheels. Gotta engineer some spring/feed into the design....but I figure a skilled builder like you can work out the incidentals.
Take apart some Bic lighters and scavange the flintwheels. Ditch the thumb wheel part, you'll need the width. Mount the flintwheels to the rear axle behind the rear wheels.
Depending on the chassis used, you can mount a flint holding bracket to the gear clamp or rear screw post with some minor brass fab. Like a reverse wheelie bar that holds the flints to the flintwheels. Gotta engineer some spring/feed into the design....but I figure a skilled builder like you can work out the incidentals.