tachco drive ratios

[raptorkev]

hi ive got a unit t120 and i want to use a chrono revcounter insted of the magnetic type cable all fits fine and the revcounter works off a drill but it doesent seem to work when connected to bike could the ratios be wrong any ideas

[L.A.B.]

The chronometric may require a cable drive that rotates in the opposite direction?

Did you have to put your drill  into reverse to drive it?

If not then the T120 cable will be driving it the wrong way.

[raptorkev]

yes your right my drive is wrong for the chrono rev counter i think the t140 goes the right way but does it fit the early t120 unit motor ?

[L.A.B.]

i think the t140 goes the right way but does it fit the early t120 unit motor ?

I'm not sure which "it" you mean (tach?/cable?/tach drive gearbox?) but, probably (if the tach cable fits both ends?) however the tach drive gearbox was different 1969-on (L/H thread into the case) and the tach cable also changed 1971-on. 

[raptorkev]

MINE IS A 65 MOTOR IVE BEEN TOLD THE T140 ETC TACHO DRIVE TURNS A MAGNETIC SPEEDO IN A CLOCKWISE DIRECTION
BUT MINE DID THAT AS WELL MAYBE IVE GOT THE T140 TACHO DRIVE ? AS I UNDRSTAND IT THE EARLY UNIT MOTOR HAD A ANTI CLOCKWISE REVCOUNTER AND LIKE YOU SAY THE CHRONOMETRIC SPEEDO WORKED OFF THE ELECTRIC DRILL IN THE FORWARD MODE SO MAYBE ALL I NEED IS AN UNIT TACHO DRIVE ?
ITS ALL A BIT CONFUSING

[L.A.B.]

MINE IS A 65 MOTOR IVE BEEN TOLD THE T140 ETC TACHO DRIVE TURNS A MAGNETIC SPEEDO IN A CLOCKWISE DIRECTION
BUT MINE DID THAT AS WELL MAYBE IVE GOT THE T140 TACHO DRIVE ? AS I UNDRSTAND IT THE EARLY UNIT MOTOR HAD A ANTI CLOCKWISE REVCOUNTER AND LIKE YOU SAY THE CHRONOMETRIC SPEEDO WORKED OFF THE ELECTRIC DRILL IN THE FORWARD MODE SO MAYBE ALL I NEED IS AN UNIT TACHO DRIVE ?
ITS ALL A BIT CONFUSING

What often leads to confusion is understanding cable rotation.

"Clockwise" drive refers to the direction of rotation of the cable when viewed at the drive end (imagine looking down through the instrument) which means that to turn a clockwise instrument in the correct direction with a drill it must be set on reverse because the drill's rotation has to be viewed looking at it from the chuck end.