3 motor drive train

I was wondering if teams will start going to 3 motor drive trains since first made it sooooooo easy to have 2 motor drive trains.

Why would you use an odd number of drive motors?!

3 per side. 6 Total.

i think he means three motors per side, totaling six motors. i guess you would add the fisher price motor somehow. i dont think it would be worth the trouble. in that case, you might as well design it from scratch, which most teams are already capable of.

why not

yes i mean 6

You’d need a whole mess o’ differentials and torque converters and all sorts of nasty stuff to make an odd number of motors work…

not really just the right gear ratio

Says who? all you have to do is match their speeds. Plenty of teams have done it. 45, 494, 188, etc.

And there’s definitely an advantage. If you figure out how to keep the FP’s cool, and not draw a ton of current with them, you’ve got a 5th and 6th CIM in your transmission, for all practial purposes

i think changing gears on the fly is over rated.

It’s surprisng how many people post without reading the whole thread. Phrontist is talking about an odd number of motors total. The thread starter meant 3 motors per side, 6 motors total. An odd number of motors total in a normal skid steer design would definitley be no easy feat.

As for 6 motors, I do not expect a great increase in the number of them. First of all, I don’t think the gain is that great because every 4 motor robot i have seen loses traction before it puts too great of a load on its motors. Also, if you use your FPs, you aren’t left with much power for your arms between the remaining motors.

In my opinion it will be better to have 3 motors on each side, however that just gives you more stuff to worrie about and more things that can go wrong. I’ll rather stay with two reliable ones, also the FP motor burns easily.


Decisions concerning the number of motors in a drivetrain (2, 4, 6, 8, 10, 12… whatever!), the number of speeds in a drivetrain, and what speeds to gear at, are engineering design decisions.
These decisions are dependant on a robot’s gearing, wheel traction and many other factors.

The output power from the motor must be modified (via gearing) to be “optimized” to achieve desired performance. Sometimes more power must be added (more motors) and sometimes the gearing must be modified for different tasks (multiple speeds). There are many different definitions of “competitive performance”. There are also many different combinations of drivetrain components tha can be used to achieve these levels of performance.

Note: for more information on drivetrain physics, shifting gears, or multiple motor drivetrains, please click the search button.

To imply that this decision can be universally made for all drivetrains, without showing any calculations
(i.e. “6 Motor drive is stooopid. Long Live 4-motors…”) is foolish.

I urge everyone: keep your opinion to yourself; unless you have some calculations to back it up.


Wouldnt that be a 6WD?

well wouldn’t it be a waste of power, as well as weight, because, the weight of the gearbox that FIRST gave us this year is heavy, imagine adding another moter to, as well as the gears needed to get the ratio and the speed right. and the power part, well six motors drawing the power all at the same time, which 2 motors could do, or even 4 is, well alot, leaving little power for the arm, but it might work if you are a pushing robot only. also the chances of something breaking or screwing up are greatly increased. which is always bad in the competion.

Team 772
If it aint broke, get INCENTIVE

Im going to go out on a limb here and guess that with efficient weight reduction, you could make a 6 motor transmission that weighed the same amount as the current kitbot one, or slightly more. It’s all a question of whether it fits the design criteria of your team’s robot.

What do you mean by power? Draining the battery? sure, it does, but any team that makes a 6 motor drive will have considered that and deemed it an acceptable penalty.

You don’t need motors for arms, you can use pneumatics, and there’s still multiple motors left over if you use 6 drive motors.

Would a 6-motor drive train offer any significant advantage over a 4-motor? It wouldn’t be any faster, but you would get more torque. But wouldn’t you also need some hi-traction wheels to take advantage of that torque? And then there’s the extra weight…

So my question is… is it worth it?

You can have a higher top speed, with more torque at that speed than a drive system with fewer motors would have.

Or some high traction treads :smiley: . BTW I would like to thank JVN personally for creating his spreadsheet motor calculator. It helped me tremendously in designing my teams gearbox this year. John, i’ll be shaking your hand at one of the competitions, good work man.

Please everyone read JVN’s post previously in this thread. It is all in how you gear it. Very few conclusions about drive systems can be made in general. You can go much faster with a six motor drive, you can much slower. You can have lots more torque, or a lot less. Adding more anything (motors, gears, etc) to a drive system doesn’t amount to any generality other than more weight, but even that is debatable.

If we are looking to discuss a specific drive system, lets do so but lets refrain from making such general coments as “it wouldn’t be any faster.”