pic: Drivetrain Concept

[crazyStone]

Originally Posted by lemiant

Why would you switch from traction wheels to omni's? All other versions of this I have seen switched to mecanums.

148's drivetrain "nonadrive" is the base for this design, and they were pretty successful with using the traction and omni. Yes it can be simplified and it will be simplified but its more fun on cad to design it from scratch when you have the time, and gives good practice instead of just dropping in a STEP. file. Your advice on simplicity is appreciated, the design has been improved to allow much easier access to the modules. Since before the transmissions were IN the switching modules and that would have put a lot of stress on the metal frame of the modules.

http://www.youtube.com/watch?v=RkR3GezFP14

[lemiant]

Originally Posted by crazyStone

148's drivetrain "nonadrive" is the base for this design, and they were pretty successful with using the traction and omni. Yes it can be simplified and it will be simplified but its more fun on cad to design it from scratch when you have the time, and gives good practice instead of just dropping in a STEP. file. Your advice on simplicity is appreciated, the design has been improved to allow much easier access to the modules. Since before the transmissions were IN the switching modules and that would have put a lot of stress on the metal frame of the modules.

http://www.youtube.com/watch?v=RkR3GezFP14

With Nona drive though, there was a 9th omni wheel perpendicular to the other 8 (hence nona). This allowed 148 to strafe. Seeing as it's just for fun, then go right ahead, I just wanted to check that you knew what you were getting into.

Also, nice video

[Aren Siekmeier]

Doing this all from scratch will definitely give you lots of great CAD practice. While people are mostly critiquing the design itself here, the model looks good.

As for the design, yes 148 had their "nonadrive" again this year, but it wasn't really. They removed the sideways omni wheel in the center that gave them omnidirectional capabilities because (I think) of the way their driver liked to do things. So this drive train will not be able to strafe unless you swap in mecanums or add a sideways omni wheel (or do something else).

If you're going to have the gearboxes offboard, you really should combine each side. You will have half the gears and half the pneumatics, and you can use standard Super Shifters which make it waaaaaaaay easier to change ratios. Unless you go with mechanums. Then you need to drive each wheel separately.

[Hawiian Cadder]

Originally Posted by compwiztobe

Doing this all from scratch will definitely give you lots of great CAD practice. While people are mostly critiquing the design itself here, the model looks good.

As for the design, yes 148 had their "nonadrive" again this year, but it wasn't really. They removed the sideways omni wheel in the center that gave them omnidirectional capabilities because (I think) of the way their driver liked to do things. So this drive train will not be able to strafe unless you swap in mecanums or add a sideways omni wheel (or do something else).

If you're going to have the gearboxes offboard, you really should combine each side. You will have half the gears and half the pneumatics, and you can use standard Super Shifters which make it waaaaaaaay easier to change ratios. Unless you go with mechanums. Then you need to drive each wheel separately.

right, but their driver was able to sort of drift, which made it one of the fastest robots in turning around to place tubes.

[Aren Siekmeier]

Originally Posted by Hawiian Cadder

right, but their driver was able to sort of drift, which made it one of the fastest robots in turning around to place tubes.

Yeah, like a power slide.

[Andrew Remmers]

If I'm not mistaken couldn't this also be a 4 speed shifter?

With the two ratios on the gearbox than then the two different ratios given on the wheel sizes and reductions (don't know if they are synced)....

Thats. Insane. I like it!

- Andrew

[crazyStone]

Just realized there was a mistake in the design concerning which Supershifter drove which side. A redesign is nessecary and taking place and should clear up some of the issues of the 2 transmissions. We are now attempting to link both front modules to one supershifter and both back modules to the other. Instead of the linking front and back on each side like it is now.

[lemiant]

Originally Posted by crazyStone

Just realized there was a mistake in the design concerning which Supershifter drove which side. A redesign is nessecary and taking place and should clear up some of the issues of the 2 transmissions. We are now attempting to link both front modules to one supershifter and both back modules to the other. Instead of the linking front and back on each side like it is now.

If I understand this right you're switching from this linkage:

<front>
o o
| |
o o

to this:

<front>
o-o

o-o

If that is the case you won't be able to turn.

[crazyStone]

good point which represents the reasoning behind having 4 gearboxes. You limit mobility if you restrict the ways you can turn if you link front and back together.

[Aren Siekmeier]

I don't get it. You obviously can't have both front wheels and both back wheels together, because both sides are always doing the same thing, and you therefore can't turn. Also, if you try to make the front wheels do something different from the back wheels, you will just shred your tread (at best).

You CAN however have each side on one gearbox, and as already stated many times, there's no reason not to. Standard tank turning is accomplished by running each side at different speeds (or even different directions).

[crazyStone]

yes it can be done and its a good approach and it is our fallback, but if you want to run traction in back and omni in front you can't have different ratios because the wheel size is different whereas if the the gearboxes are seperated the speeds themselves can be altered and allow for the two different wheel sizes to work together.

[PAR_WIG1350]

Originally Posted by crazyStone

yes it can be done and its a good approach and it is our fallback, but if you want to run traction in back and omni in front you can't have different ratios because the wheel size is different whereas if the the gearboxes are seperated the speeds themselves can be altered and allow for the two different wheel sizes to work together.

You can accommodate different wheel sizes driven off of the same gearbox by gearing the wheels at a ratio (to each other) equivalent to the ratios of the wheel sizes. For example, if you have a 4inch and an 8 inch wheel driven off of the same gearbox, by having a 1:1 sprocket ratio between the output and the 4 inch wheel and a 2:1 ratio between the output and the 8 inch wheel they will run at the same ground speed. It is usually lighter to uses different sprockets to accommodate the wheel size difference than to use different gearboxes for the different wheels.