installing an old speedo cable drive on a rear wheel for prop drive

[meb]

Considering getting and installing a speedometer drive and cable on a rear wheel to drive a prop for the water segment of a kinetic sculpture race. Will the old front speedo drives fit on the left side of a rear axle or is the center hole too small in diameter to fit on the rear axle?

 

[_]

On Sun, 20 Apr 2008 15:52:39 +1000, meb wrote:

> Considering getting and installing a speedometer drive and cable on a
> rear wheel to drive a prop for the water segment of a kinetic sculpture
> race. Will the old front speedo drives fit on the left side of a rear
> axle or is the center hole too small in diameter to fit on the rear
> axle?

Probably too small - typical front axles for which those mechanical speedos
were made had a 5/16" or 3/8" diameter. However, as I recall, the centre
parts were just cheap pot metal and you could probably easily drill or ream
the centre hole to suit.

You may not get much torque before failure out of such an arrangement.

 

[meb]

On Sun, 20 Apr 2008 15:52:39 +1000, meb wrote:

> Considering getting and installing a speedometer drive and cable on a
> rear wheel to drive a prop for the water segment of a kinetic sculpture
> race. Will the old front speedo drives fit on the left side of a rear
> axle or is the center hole too small in diameter to fit on the rear
> axle?

Probably too small - typical front axles for which those mechanical speedos
were made had a 5/16" or 3/8" diameter. However, as I recall, the centre
parts were just cheap pot metal and you could probably easily drill or ream
the centre hole to suit.

You may not get much torque before failure out of such an arrangement.

Turner, Spicer, and the early Christini AWD systems used the speedo drives to turn on the front wheel so torque on a small propellor should work. Althoughm I know Spicer used a slightly lower gear ratio up front so the front would freewheel unless slipping on a low coefficient surface. Turner also has a freewheel, so it probably has a lower front ratio up front. I may be able to pull out my Turner system and see if fits the rear.

As for reaming, anyone recall if it is necessary to ream out to fit the rear axle would, it destroy anything critical?

 

[meb]

Turner, Spicer, and the early Christini AWD systems used the speedo drives to turn on the front wheel so torque on a small propellor should work. Althoughm I know Spicer used a slightly lower gear ratio up front so the front would freewheel unless slipping on a low coefficient surface. Turner also has a freewheel, so it probably has a lower front ratio up front. I may be able to pull out my Turner system and see if fits the rear.

As for reaming, anyone recall if it is necessary to ream out to fit the rear axle would, it destroy anything critical?

The Turner system uses 1/8 chain at the front end of the cable and a Dicta freewheel, and the speedo cable is much bigger in diameter and more robust than a bicycle speedo cable. This cable is fatter than automobile speedo cables.