Wire Drive:

The original tail drive system used on the X-Cell was a wire drive system. This consisted of a 5/64" piece of music wire running in a piece of 1/8" brass tubing.

Wire tail drive systems suffered from a wind/unwind of the wire, creating uneven tail rotor speed as loads were applied to the tail blades.

The torque tube drive was introduced to overcome this  short coming of the wire drive.

Pre 99  Torque Tube Drive:

The torque tube drive was first introduced in the 1993 X-Cell Custom. The unit pictured at the right (pre 99 Spec) used dog bones which were attached to the tube using set screws. The tube had an steel insert glued into the tube which protruded out far enough for attaching the ends.

This torque tube used two support bearings. The bearing assemblies could be removed from these unit for R&R by removing the dog bone .

99 Spec Torque Tube Drive:

The 99 spec torque tube drive utilized a truer running carbon tube and came pre-assembled with the ends glued on.

This torque tube used one support bearing. The Support bearing was pre installed and the inner race was not removable from this unit as the brass sleeve was glued to the shaft.

Dog bone couplers:

The 99 spec and pre-99 spec torque tubes both used the same front and rear coupler unit. The coupler shown is a rear unit. The front coupler has a longer shaft.

Dog bone coupler used with torque tube

#0832 Heavy Duty Front Transmission Support:

With the introduction of faster gyro's and servo's, the load placed on the front pinion, using the torque tube drive system, was greater than the standard  front bearing block could support. The front pinion gear is heavily cantilevered forward of the bearing block and flexing of the shaft allowed for stripping of the main gear.

A heavy duty front transmission support was introduced which provided a bearing in front of the pinion. The bearing block was mounted using the rear bolt of the lower main shaft bearing and required a new lower main shaft bearing block. The block was modified to receive the u shaped tail shaft bearing block. The front coupler shaft used with the HD support was also longer than the standard coupler shaft provided with the torque tube assembly.

The installation also used brass threaded inserts for mounting the standard transmission bearing block. These inserts prevented pre-loading the bearings in the block by over tightening of the mounting screws.

NOTE: The HD front transmission can not be used with the wire drive system. The front pinion shaft of the wire drive coupler is too short. A longer unit is not available. 

Pre 99 support bearing (one of two)

99 Spec torque tube dog bone

# 0832 Heavy Duty front transmission upgrade kit