Hetzer preselect gearbox compared to Ferret

[David Herbert]

Hi Malcolm,
If there was a fluid flywheel or clutch, it would be between the engine and the Wilson gearbox, not between the gearbox and the steering system.

Also the selection and engagement of gears in any Wilson box is done by engaging the band brake for that gear. Thus the selection and the clutch is combined into one action as there is effectively one clutch (the band brake) for each gear. When you press the pedal down fully, any brake band that was engaged is released (which is why you need to press it all the way down) and on raising the pedal the next selected gear is engaged. Only one new gear can be selected at a time as there is a hinged sprag for each brake band that only engages if pushed out by a cam. All the cams are on a shaft that is turned by the gear selection lever and only one sprag is pushed out at a time. So the CHOICE of gear is controlled by the gear selector lever and the disengagement / engagement by the gear change pedal.

I have no experience of Pz38t but I thought that the steering was similar to the system on British Crusader, ie a bevel box (no differential) to turn the drive 90 degrees and then epicyclic / band brake steering units inboard of each final drive to give: High, low and stop separately for each track ( or at least drive and stop). There must be brakes that work together for stopping the vehicle and on a small tracked vehicle designed in the 30s it would be very unusual for it not to be possible to engage them separately to give a pivot steer.

I expect to be corrected about the steering system so if anyone has a nice drawing of the system used in a Hetzer it would be great to see it.

David