pic: Drivetrain Concept
 

Re: pic: Drivetrain Concept
 

Sorry to pick on you but I can't tell what this is supposed to be. This is due to a couple of factors. Foremost amongst these is the fact that you have large sections of your render in a dark color and it is on a black background. Maybe I'm just old but I really can't see much detail. Perhaps you should make another render that is a little more focused on the model and uses a better background color (might I suggest a light grey?) You could also post some of your reasons for designing it this way as well as weight, speed, etc.

Re: pic: Drivetrain Concept
 

You may also want to post some specs. All I see is 4 traction wheels that appear to be on sliders and some unidentified boxes in the center.

Re: pic: Drivetrain Concept
 

Looks like there's some omnis in there too. Possibly articulating? Seems like it'd be an interesting concept (if not totally unique) with some more info.

Re: pic: Drivetrain Concept
 

It looks like a Nonadrive iteration. The gearboxes are outboard of the modules, unlike 148's 2011 revision which mounts them on the physical module. These are chained to the outest wheel (the pivot).

Re: pic: Drivetrain Concept
 

IT almost looks like there is a set of traction wheels in the center, then a set of omni wheels, then an outer set of traction wheels. depending on how it was articulated that would make a beast of a 12wd, although it may be a tad heavy for what it does.

Re: pic: Drivetrain Concept
 

Yes you are correct, it is based off of 148 modules from this year. The original design had the switching transmissions within the wheel modules but due to difficulties with mantaince and access the design was changed to allow the switching transmission to be completely independent of the modules. The drive is a 4 wheel traction on the outside and then 4 trick omni's on the insides of the modules. Then a chain is linked from the inner transmission to the shaft that the traction wheel is attached to. The switching transmissions drop right out of the bottom for easy exchange. Besides that the gear ratios are rather extreme, the low gear to traction is 1:40 and then omnis are 1:20 and the high gear for traction is 1:8 and the high for omni is 1:4. These should faciaity major pushing power. Any comments would be appreciated. Perhaps someone has already created such a drivetrain in which case I apoligize for that but I did not see any other similiar drivetrains besides 148 as the base.

Re: pic: Drivetrain Concept
 

I do believe that the 4 pneumatic cylinder towers will act more like a shock absorption system when the robot is fully loaded with all of the weight, since air compresses. ~26lbs (60psi) of force per cylinder * 8 cylinders is ~208lbs of to lift the whole thing -- slowing down from high speed may cause an inertial moment that can overcome the 104lbs on the front/rear. This most likely wouldn't be a problem until both wheels of a single module touch the ground. At that point, something's going to rip itself apart (most likely the belt connecting the two wheels).

I believe that's why 148 uses leverage to articulate their modules. It puts the weight of the robot on a pivot rather than directly on the pneumatic cylinder. This reduces the shocks, inertial moments, etc that the cylinder experiences. It also reduces the number of cylinders required to articulate the drive train, thus reducing its weight.

You could also combine each gearbox on each side -- there's no reason to have 4 independent gearboxes since its controlled exactly like a skid steer with high/low gears.

Re: pic: Drivetrain Concept
 

Shows a Top View of the Chain attaching the modules
http://www.chiefdelphi.com/media/photos/37029

A View of the transmissions
http://www.chiefdelphi.com/media/photos/37030

I'll try to render another image soon, it is just very taxing on my laptop to render full images.

Re: pic: Drivetrain Concept
 

Yes, Thank you for that advice, the interia is something that definitly will play a key factor. The choice for the smaller pistons was the fact they use less air then a single large piston. Also the individiual transmissions are used because of the slight boost in efficency and the ease of replacement and custom gearing ratios. However if we encounter difficulties with manufacturing custom gearboxes each side will recieve one AndyMark SuperShifter and that will slide in from the bottom.

Re: pic: Drivetrain Concept
 

Why would you switch from traction wheels to omni's? All other versions of this I have seen switched to mecanums. Also I recommend taking Jesse's advice; this drive is already hard enough, unless you're wildstang I'd try to add as much simplicity as possibly. (Wildstang would also go for simplicity, not because they have to, but because they understand it's importance, hence their awesomeness)

Re: pic: Drivetrain Concept
 

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

Re: pic: Drivetrain Concept
 

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

Re: pic: Drivetrain Concept
 

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.

Re: pic: Drivetrain Concept
 

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

Re: pic: Drivetrain Concept
 

Yeah, like a power slide.

Re: pic: Drivetrain Concept
 

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! :D

- Andrew

Re: pic: Drivetrain Concept
 

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.

Re: pic: Drivetrain Concept
 

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.

Re: pic: Drivetrain Concept
 

good point :P 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.

Re: pic: Drivetrain Concept
 

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).

Re: pic: Drivetrain Concept
 

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.

Re: pic: Drivetrain Concept
 

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.