Half-Track Drivetrain

[Tommy Styrvoky]

I'm planning to build a halftrack in the next month or so and I'm wondering if it has front wheel drive and driven by the tracks, should I have a different ratio for the front wheels and for the tracks. Because there is a difference between the circumference of the wheel and the number of tracks moved by a sprocket in a rotation. Also there will be a braking mechanism for the drive sprockets for turning.

Edited June 2, 2014 by Tommy Styrvoky

[Bzroom]

Let us know. It will be awesome!

[MrNumbskull13]

Have the front wheels as close in diameter to the height of the tracks, put a centre diff between the front wheels and tracks and have a normal diff between the 2 tracks.

[Tommy Styrvoky]

Have the front wheels as close in diameter to the height of the tracks, put a centre diff between the front wheels and tracks and have a normal diff between the 2 tracks.

yeah I think a diffrential would work best,and I wouldn't have to worry about it. I could also have that differential be locked too.

[Tommy Styrvoky]

The only problem is that I have only 2 diffs.

[Rockbrick]

I always wondered why half tracks were called 'Kegresse' a quick wikipedia lookup and now I know and want to share with you that Adolphe Kégresse was a French military engineer, inventor of the half-track and the dual-clutch transmission. Worked for Tsar Nicholas and Citroen.

Edited June 3, 2014 by Rockbrick

[Tommy Styrvoky]

This will be for my upcoming Sd.kfz 9 famo and that is a really long half track and its like 70 studs long in 1/15th scale

[Nazgarot]

I've made a proof of concept of a half track using a subtractor for turning (the tracks) as well as a servo for the steering. It works, but requires that the main drive is locked to a single speed. The servo and the M-motor controling the subtractor is driven of the same channel, making the delta in speed correspond with the turning angle of the wheels. This is only possible to achieve at a given speed, but gives the model very smooth turning. In a model of that size you could easily fit it, even using stronger custom diffs.

I've also planed to use this to make a rally car (if i can ever get my hands on a buggy motor) with vectored rear drive and a torsen center differential. It will not have the option of loosing grip... =]

If you want to see the concept and exchange ideas, please send me a PM. I don't want to publish it just yet as I have some more R&D to do before I base a model of it. But eventually it will either hit brickshelf or be posted here, based on how successful I am...

-ED-

[Tommy Styrvoky]

I've made a proof of concept of a half track using a subtractor for turning (the tracks) as well as a servo for the steering. It works, but requires that the main drive is locked to a single speed. The servo and the M-motor controling the subtractor is driven of the same channel, making the delta in speed correspond with the turning angle of the wheels. This is only possible to achieve at a given speed, but gives the model very smooth turning. In a model of that size you could easily fit it, even using stronger custom diffs.

I've also planed to use this to make a rally car (if i can ever get my hands on a buggy motor) with vectored rear drive and a torsen center differential. It will not have the option of loosing grip... =]

If you want to see the concept and exchange ideas, please send me a PM. I don't want to publish it just yet as I have some more R&D to do before I base a model of it. But eventually it will either hit brickshelf or be posted here, based on how successful I am...

-ED-

The only problem is Thai don't have a servo motor and I will also have a crane at the back of the model.

[Zerobricks]

If you have different wheel/track sized you can always use a central diff to compensate for the size differences... As other stated. But try to have the right as good as possible, otherwise the diff wont split the torque equally.

[ms09]

As far as I know, german half-track vehicles in WW2 normally don't have front wheel drive-shaft, maybe only schwere Wehrmacht Schlepper (sWS) is an exception. On the other hand, american half-track vehicle in WW2 normally have front wheel drive-shaft. But ok, who cares...

Once upon a time I built a half-track Panzerwerfer Sd.Kfz.4/1 with front wheel drive-shaft but no center differential, the combinition of 81.6 x 38 R tyre and 40.4 tread sprocket wheel provides a smooth driving for whole drivetrain. Depends on steering angle, differentail or differential lock (1:3 or 3:1) are applied for track steering.

Hopefully it can give you some inspiration in building your famo.

[Tommy Styrvoky]

looked at the underside of the chassis of the FAMO and it doesn't have front wheel drive

[TheItalianBrick]

It will be cool! Love half truck! About the ratio only you need to consider is the diameter of the wheel that has to be similar with the height of the tracks, the closer the better.

then if you want to get something crazy you must got for a double clutch system, therfor you won;t need any middle differential. The tricky part will be to calibrate the speed of the left and right tracks according with the steering whells. for istance a servo that while steering actuatues the 2 clutches! this way you will get a good ratio!

if you won't do it, then I'll do it!!