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I’m rewording this question so people can better understand it.

On a “caterpillar track” built on a straight line, with 1 or more sprockets driving the vehicle with motors in direct drive.

1.) How would you arrange the sprockets, and idle wheels, for the most efficient forward and reverse drive? For the sake of this question, assume there’s only allowed 3 sprockets or wheels in total.

2.) Also consider the motors. How would the number of motors direct driving each sprocket affect the design? For instance, 4 sprockets and 4 motors, or just 2 motors in the rear?

Any further discussion welcome.

This is just an image for example with 1 possible configuration.

enter image description here

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  • $\begingroup$ Ideal for what? $\endgroup$
    – Solar Mike
    Oct 10 at 8:41
  • $\begingroup$ Why not check out tracked vehicles - many options are used even a triangle - think about why... $\endgroup$
    – Solar Mike
    Oct 10 at 8:42
  • $\begingroup$ I have looked at many. I am asking stack exchange to find out why. $\endgroup$
    – BobaJFET
    Oct 10 at 9:13
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    $\begingroup$ you cannot drive both front and back sprockets without some amount of slip, because such an arrangement would not allow the track to "stretch" when driving over a large obstacle ... if you drive the front sprocket then the vehicle will experience lower sliding friction between the track and the ground when moving forward $\endgroup$
    – jsotola
    Oct 10 at 17:02
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    $\begingroup$ "Ideal" is not a specification $\endgroup$
    – Tiger Guy
    Oct 11 at 13:31
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I'm no expert on this subject but have noticed that conveyor systems always drive the roller at the exit end so that the loaded section of the belt is under tension and the underside can be loose. A bicycle chain works in the same way; the top side is under tension and the return on the underside is slack or lightly tensioned.

In your case the conveyor is upside down but the tension needs to be on the underside so the drive will be at the rear as you suggest. The top side can then hang slightly slack.

The additional wheels will give multiple support points when climbing obstacles. More is probably better as fewer will put a lot of stress on the track.

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  • $\begingroup$ I’ve reworded the question again for clarification. Please consider that with this design there is no underside. We’re talking about a straight line. $\endgroup$
    – BobaJFET
    Oct 11 at 16:08
  • $\begingroup$ The "underside" is the section of track in contact with the ground. My answer doesn't really change after your question edits. $\endgroup$
    – Transistor
    Oct 11 at 16:52
  • $\begingroup$ Is there a need for 2 sprockets, or can the non-driven sprocket be a wheel instead? $\endgroup$
    – BobaJFET
    Oct 11 at 17:29
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Here's an answer I found on reddit as it relates to tanks:

https://www.reddit.com/r/AskEngineers/comments/6mxzo8/comment/dk5t5ss/

There's several pros and cons of each setup and it's one of those things for which there's probably not a 'correct' location. Several have already been mentioned but off the top of my head:

Drive sprockets at the front:

Pros:

Gearbox next to the driver so system for gear changing is simpler to implement

Gearbox at the front gives a big block of metal between incoming fire and the crew for additional crew protection (this reason often given for layout of WW2 German designs and the Merkava)

Returning tracks will shed mud, sand etc before they reach the drive sprockets so wear on tracks and sprockets is reduced

Cons:

A design with rear engine and front gearbox requires a driveshaft to pass through or under the fighting compartment. This either reduces internal space or requires a taller profile.

Hits to the front are more likely to damage drivetrain components and make it harder to salvage the tank.

Drive sprockets at the rear:

Pros:

Engine and gearbox can be packaged together at the rear, giving a smaller and lower tank. This often makes maintenance and repairs simpler as engine and gearbox can both be accessed through the rear deck

Hits to the front are less likely to damage drivetrain components and so tank is likely easier to salvage after being knocked out (this is only really an advantage if crew members are cheap and you don't mind using them as extra armour for your expensive tank)

Cons:

Tracks hit sprockets immediately after leaving the ground so are likely to be covered in mud etc which is then forced through the drive tooth contacts, increasing wear rate

More mechanical complexity in changing gear as the driver must control a gearbox at the rear from his position at the front

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  • $\begingroup$ So what about drive sprockets above, as in top of a triangle? Seen on some Cat dozers... $\endgroup$
    – Solar Mike
    Oct 15 at 7:35
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The pro of the triangle drive is that the track length and cg position can be varied without changing the drive mechanicals. A tracked cable plow tractor wants a different cg than a utility angle dozer. Same with a big cable winch unit.

The con is track wear. The track has to pivot in six places instead of four, and wear follows accordingly.

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