BUILDING A CYCLEKART
BUILDING A CYCLEKART
BUILD SERIES no. 5: Brakes
The 6” Azusa drum brake (AZ 2551/ AZ2252) has been our most popular. The Azusa 1806 brake pedal has been used (with companion AZ 1811 throttle pedals) on every car except Bloody Mary.
The Panhard brake is located on the right side of the rear axle. Style AZ 2252 has been used. It is mounted directly to the axle bearing flangette on the inside of the frame rail. The Panhard has one wheel drive so the brake is stopping the driven wheel. The brake is controlled by a pull-rod. The pedal pushes on a cross shaft (red) which converts the action to a pull on the brake rod which runs down the inside of the right side frame rail.
The Fiat set up is the same at the axle but the pedal arrangement is different. The pedal pulls a rod between the driver’s legs to a cross shaft (red) located under the driver’s knees. This car has a live axle and so the brake is stopping both wheels.
The Miller has a raised heel plate like the Fiat but the plate extends farther back. The cross shaft is below it. The pedal pushes a rod to the cross shaft which is converted to a pull on the brake. The brake is again on the right side of the live axle.
The Austro-Daimler ran for a while with one brake but braking half a differential axle was only marginally successful. This car now has two 6” drums, one on each half shaft. The brakes are are both AZ 2252 mounted to the bearing carriers on the engine sub frame. Both brakes are controlled from the pedal. The linkage is complex. The brake pedal pushes on cross shaft in front of the “firewall”. This pulls a cable connected to an arm on a second cross shaft under the floor which pulls on the two brake rods. The car now stops without violently hooking. The downside is that all this is very heavy.
The GN was converted to a 6” drum after an earlier attempt to use 4 1/2” band-brakes. The band brake drums were integral to the driven sprockets in the GN’s failed two chain, changeable ratio, drive scheme. The band brakes were controlled by heavy cables. The pedal pushed a cross shaft which converted action to a pull on two unjacketed, straight cables. This was easy to convert to the current scheme of a pull rod on the brake pedal side. The band brakes were actually OK, feeble but OK. What didn’t work was the drive scheme and when the entire, formerly rigid, rear end of the car was replaced with the sprung rear axle the pair of band brakes had to be abandoned in favor of the single drum. The brake is fitted on the left side of the axle on the GN. The axle is live so the drum stops both wheels.
The Peugeot has the ubiquitous 6” drum mounted conventionally on the axle bearing flangette on the right side but it also has a second 6” disk brake. The disk brake caliper is mounted to the outside of the left frame rail. The disk brake is a 6” Airheart, available from the usual go-kart resources. The axle is live and either brake stops both wheels. The reason for the second brake was part nervous parenting and partly a desire to try both brake types. The disk is controlled by a push rod. The pedal pulls on a lever which pushes the rod. The drum is controlled by a hand lever to the driver’s right. Disk/ drum, push/ pull, hand/ foot - the effectiveness is all about the same. The disk has worn through its pads more quickly but I think that has more to do with the natural inclination (for modern drivers) to use the foot pedal almost all the time and for guest drivers, which this car has hosted in abundance, to use the brakes too much.
Bloody Mary recently got a 6” drum as well. Initially this car had two 4 1/2” mini-bike drums. Mary has one wheel drive and the idea was to be able to choose which wheel to stop thereby helping the steering. Both brakes were controlled by cable (not the macho cable used on the early GN) and between the spongy cables and tiny drums the stopping effect was negligible. Nervous parenting decided to switch to the foolproof 6” drum. The free-wheel had been joined to one of the little 4 1/2” brakes with a collar. Now, both brakes stop the same driven wheel. The right side mini brake is controlled by a hand lever. This has been retained because it is such an important part of the look of the inspiration car and it feels fabulously vintage to reach out and pull it! The left side brake (6” drum) is controlled by foot. It is connected directly by a jacketed cable. The brake pedal was fabricated from scratch and is the sole exception to the AZ 1806 pedal hegemony. The tires on Bloody Mary are skinny road tires so the one sided braking doesn’t have the nasty effect it did on the Austro-Daimler. It has very little effect at all!
Sunday, January 23, 2011