fun with planetary gears...

I’ve noticed a great amount of interest in these systems. And yes, they are very cool. But I’ve also noticed that it takes 2 motors to run 1 transmission or wheel with these systems.

The question is this:

Are they practical for next year’s game, as one would have to (in theory) use 8 motors to power all four wheels?

The second question is this:

Would it be possible to use these with Mecanum (i hope I spelled it right) wheels? The movement offered by these wheels may give an advantage while scoring or blocking.

yes 4 motor HS drive, you can just chain the extra wheel if you want

as you have said, you will need 8 motors to power each wheel separately (to utilize the mecanum)

no, i do not think that a 8 motor drive is a good trade off just to have side to side movement

if you want mecanums, its better to do a “normal” (non planetary) drive train

  1. Well it depends on your robot design and strategy. If you really want to use up 8 motors on your drive and only leave 2 for other systems, then I hope your drive is really important, but it’s totally possible.

However, this isn’t necessary because with 4wD, the wheels on each side are usually chained together, drawing from a single power source, or 2 motors each (4 in total).

  1. Yes, you could use it on mecanums, or any other holonomic drive, as long as each wheel is independently powered, requiring 2 motors each. I’m thinking if you’re wanting to shift gears on 4 different outputs, you’d probably want to do some sort of global gearshift system that changes every output with a single actuation (pneumatics, probably).

Yeah, strafing could be pretty useful with the troughs. An H-drive (4WD with a strafe wheel) could also work.

Has anybody tried driving over sacks yet? Does a holonomic drive suffer especially when lifting off the ground?

We drove over the sacks with an omni squarebot for awhile, it really didn’t have any issues. it could easily go over pyramids about 3-4 sacks high and it didn’t go off course much.

Also, YEAH! i love 8 motor mecanum drives!

You could have mecanums in just the rear on transmissions, and use the high-torque mode for strafing and the high-speed mode for forward and back movement. It would be a little weird, but it’s possible.

you can actually run a mecanum drive with planetarys and only use 4 motors.

How? I don’t see how this is possible with keeping strafing capabilities.

it is actually very simple. It may be difficult tryng to explain but i think i will make a video explaining how to. the most difficult part will be spacing and it involves 2 planetarys that have doubled up sprockets.

But how can you control 2 wheel independently of each other with 2 different gearings. For one wheel you need 4 different movements: forward torque, forward speed, backward torque, and backward speed. You can provide these movements with 2 motors (assuming you only use full power) each motor can go forward or backward for 4 total combinations. If you were to add a second mecanum wheel it would take 8 combinations. The only thing I can think of is to use pneumatics to some how change gear settings or weather the bot is strafing or not.

I could see it working with 6 motors potentially and 2 planetary gears per side.

there is nothing to shift on planetarys. it changes depending on which motor you drive. Mecanums are not entirely independent.

It is actually possible if the front-left and back-right wheels are geared/chained together, as well as the front-right and the back-left.
Good use for the new 1:2 gear ratio bevel gears to transfer all that torque across?

The only issue there is that you can’t turn, but do you really need to turn with a mecanum drive? :wink:

So no, it is not possible to power all 4 mecanums independently and with 2 different speed options with only 4 motors, unless you have a pneumatic shifty thing like you said.

I did think of that to but I thought that it was impractical because then your intake would occasionally facing the wrong way.

Not if your whole manipulator system were on a turntable (have fun building that though).

That would waste motors that could have made the drive faster or have more torque.

Exactly my thoughts. Perhaps an independent torque motor for each wheel with its own planetary gear system, with a shared speed motor (for non-strafing trips) or a similar configuration?

You can’t have a planetary gear system that has two speeds with only one motor.

My turntable suggestion was just to show that you need 8 motors if you really want to have a mecanum speed-shifting drive.

No, you misunderstand. You have one planetary gear system for each wheel, with an independent motor geared for torque in the planetary gear system. You use a third motor on each side (bringing the grand total to 6 motors now) geared for speed in both of the planetary gear systems in that side. Strafing is now allowed, yet you still get the speed in going forward/backward/turning if you power this third motor.

Am I understandable or do I need to make a diagram or something?

Oh yes I did, sorry.

So the third motor is shared between the two planetary gear sets on each side?

How would it allow strafing right, strafing left, forward, and reverse (and each in two speeds)?

I can’t picture how the combinations of inputs would lead to those 8 possible outputs.

I was thinking about this too but when you strafe one wheel will be in torque mode and the other will be in speed mode.