pic: Butterfly Drive Concept



This is a Butterfly drive train design that I’ve been working on for awhile and I’m looking for some feedback on the design. It uses vexpro 3 cim ball shifter with 2 cim 1 minicim in each. It is geared for 14.72 ft/sec and 6.81 ft/sec adjusted speed. Most of the parts are designed to be COTS and all the custom plates are 1/4 inch. Inventor gives the weight at approximately 50 lbs. Any feedback would be greatly appreciated.

Wouldn’t this be like an actuatable slide drive due to the center wheel? I thought butterfly didn’t implement that.
50lbs is a lot for a drivebase. Do you really need those upper supports? It also looks like you’re running a 7-cim drivetrain right now, which I’m not sure you need.
I like the design of the modules. I think they’re missing a few spacers on the screws though.
That cylinder setup is not the most efficient because of the sharp angle it pushes the module down at. Is it possible to use a shorter cylinder that’s more above the module so that it points almost downwards?

The addition of the slide drive is cool, but I think the extra wheel in the center is unnecessary - you’ll should be just fine using a single wheel in the middle. I have a feeling you’ll also need to increase the motor count in the center if you want an appreciable speed for your sliding - going down to 2 CIMs per shifter and 2 cims in the middle should give you a pretty good balance. That should also reduce your weight a little - as mentioned above, 50 lbs is a lot for a drivetrain. I figure you should aim to be in the ballpark of 25 - 35 lbs for most drivetrains in FRC. That said, that estimate does seem a little high. Make sure you have the proper weights assigned for the various motors (override part weights), and the correct materials for the tubing / plates. You might also be able to reduce the thickness of your tubing - while I can’t quite see what thickness the tubing is, you might want to consider using something in the range of 1/16 - .09" tubing.

Speaking of the plates - those plates look a little too pocketed, and I’d be seriously concerned about their rigidity.

Naming it an actuatable slide drive would probably be more accurate, I hadn’t thought of that. I called it a butterfly due to the shifting of the wheel modules.
I know 50lbs is a lot for a drive base and I’ve been working on lightening it. The upper supports are there for bumper mounting purposes but I will probably work on revising it by maybe removing the front and back rails.
Yes 7 cim is overkill if I were to actually build it I would almost certainly just use 2 cims in each gear box and a minicim for the center (depending on game)
As for cylinders I’m trying to design to take advantage of some 3/4 inch throw that were bought for last season but never used. So the cylinders in the CAD are just place holders. I can edit the design to change where the cylinders are placed.

The extra wheel in the center is to make it function so that the wheels would dig into the ground when they are powered. This is so the wheels still have contact on slightly uneven surfaces.
I checked through the weights in inventor and I’m fairly sure there all assigned right.
The tubing is versa frame which is already .1 inch wall.
The plates might be pocket a little much I will probably change that for the next revision.

what you have here is a nonodrive (i think thats how its spelled). Anyways check out 148’s 2014 drive system, which seems to be the inspiration for this.

It looks like the two center wheels are part of a tipping kicker wheel that applies a force into the ground when it tips. We used this design this year, and it worked out pretty well for us.

I would suggest supporting all of your wheel modules on both side, instead of cantilevering them on one side.

Another thing that I noticed is that if you break a belt on your drive train, you have to literally disassemble the frame in order to put another belt on. You definitely want to figure out a way to make replacing belts easier and actually possible.

You should also consider swapping the positions of your wheels so that the modules pivot off of your traction wheels. Last summer I designed a drivetrain very similar to this one with the same wheel configuration, but one of my mentors pointed out that you’re going to be hitting and pushing against people primarily with your traction wheels and the resulting contact might damage the modules in the current configuration. If you swap them, most of the energy will go into the stronger frame which is what you want.

I believe that this particular design is called a decadrive because it has 10 wheels. A nonadrive is very similar, but there is only one center wheel giving a total of 9.

In response to the belt breaking I had thought about that which is why that is actually #25 chain. And yes decadrive is the proper name (thank you I couldn’t remember what it was called).

Ah, gotcha. While I can see how that design will make it so that only one of the two wheels is on the ground when turning, did you guys have a mechanism in place to balance the module when the motor wasn’t turning (some sort of spring return, maybe?), or was that not necessary to keep both wheels off the ground?

I also see that your design from this year used a single CIM motor on the slide - what lateral speed were you guys capable of with that?

Personally I’m a fan of the name butterslide drive :smiley:

It looks like it uses chain, not belt.
+1 on making it pivot around the traction wheel, although I would want to for the suspension effect as well.

It appears as if it pivots on the omniwheels. I’d have some concern about the load the traction wheels will apply to the pivot axle when the machine is pushed sideways.

Although we thought about having some way to return the module to its level position (mechanical or code), we found that it was necessary. In addition, we found that we needed to keep the module from tilting with gravity to reduce “hopping”, basically when the module hits the ground but can’t get traction and causes the whole robot to jump up a little. We solved this problem with a ramp up in the code and a friction plate that we would tighten in place made out of a VersaHub and gum rubber.

In response to the belt breaking I had thought about that which is why that is actually #25 chain. And yes decadrive is the proper name (thank you I couldn’t remember what it was called).

Ah yes, after taking a closer look, I saw that it’s chain. Haha sorry about that

Perhaps you can explain because I have never seen a drivetrain like this before. What are the advantages of this over octocanum? Based on the picture and description it looks heavier, more complex, uses more motors, and is harder to build than an octocanum equivalent. I’m sure I must be missing something or someone else would have brought this up earlier, but I don’t see it.

With Mecanum you have to run each wheel individually. Here they can run each side resulting in the ability to run 3 cims per side.

I’m actually not all that sure what the advantages are over octanum. I know that mechanums are a little trickier to code. I also know that some people just don’t like mechanums for whatever reason (not really a valid argument).

I’m definitely not the best person to answer this question. I curious to see what other advantages people can think of.

:slight_smile:

Everything I thought I knew has been nothing but a lie…

I was hoping Mecanum Wheel would reply, but quoting “it” is just as sufficient

By the way, Mecanum AB is the company that either invented or popularized the wheel, but is nonetheless where the name came from

Yep this is why it was designed like this. Also I wanted to ability to have a 2 speed shift with the wheels at a 1:1 ratio so this seemed like the simplest solution. Also the next iteration of the design will (probably) have the traction and omni flipped.