15-08-2015 16:29

asid61

Re: pic: Butterfly Drive Concept

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?

15-08-2015 16:53

TheHolyHades1

Re: pic: Butterfly Drive Concept

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.

15-08-2015 17:02

RoboticDaymon

Re: pic: Butterfly Drive Concept

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.

15-08-2015 18:30

wilful

Re: pic: Butterfly Drive Concept

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.

15-08-2015 18:46

hectorcastillo

Re: pic: Butterfly Drive Concept

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.

15-08-2015 18:49

hectorcastillo

Re: pic: Butterfly Drive Concept

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.

15-08-2015 19:39

RoboticDaymon

Re: pic: Butterfly Drive Concept

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).

15-08-2015 20:58

TheHolyHades1

Re: pic: Butterfly Drive Concept

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?

15-08-2015 22:17

Ginger Power

Re: pic: Butterfly Drive Concept

Personally I'm a fan of the name butterslide drive

15-08-2015 22:28

asid61

Re: pic: Butterfly Drive Concept

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.

15-08-2015 23:29

Madison

Re: pic: Butterfly Drive Concept

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.

15-08-2015 23:48

hectorcastillo

Re: pic: Butterfly Drive Concept

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.

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

15-08-2015 23:56

Ari423

Re: pic: Butterfly Drive Concept

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.

16-08-2015 00:12

orangemoore

Re: pic: Butterfly Drive Concept

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.

16-08-2015 00:17

hectorcastillo

Re: pic: Butterfly Drive Concept

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.

16-08-2015 00:24

Knufire

Re: pic: Butterfly Drive Concept

16-08-2015 01:02

hectorcastillo

Re: pic: Butterfly Drive Concept

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

16-08-2015 02:10

BBray_T1296

Re: pic: Butterfly Drive Concept

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

16-08-2015 02:42

RoboticDaymon

Re: pic: Butterfly Drive Concept

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.

16-08-2015 03:43

asid61

Re: pic: Butterfly Drive Concept

You do lose some functionality compared to making the traction wheel smaller, but do you think the loss pushing resistance of this drive is worth the lower gear in omni mode?
Might want to rethink that 6-cim drivetrain. The Roborio browns out so easily...

16-08-2015 13:03

hectorcastillo

Re: pic: Butterfly Drive Concept

Can you explain "browning out" or share share thread that explains this?

16-08-2015 13:19

Dunngeon

Re: pic: Butterfly Drive Concept

Google is a great way to answer your own question, click here.

Click the first result

16-08-2015 17:51

Knufire

Re: pic: Butterfly Drive Concept

Agreed. Software current monitoring/control, good monitoring of battery health, and a bulletproof electrical system are essential to effectively use a 6 CIM drive in a normal (i.e. not RR) game on this control system.

17-08-2015 22:57

RoboticDaymon

Re: pic: Butterfly Drive Concept

For the 6(7) cim I agree for most circumstances it is probably overkill. if this were to be manufactured I would probably just leave a cim out of each of the 2 speed gearboxes or use current monitoring code or both. Realistically this would probably be assembled with 2 cim in each 2 speed and 1 mini cim for the center wheels.

17-08-2015 23:44

philso

Re: pic: Butterfly Drive Concept

Have you designed this so that the complete butterfly module can be removed and installed as a single complete assembly or do the butterfly modules have to be assembled in the chassis? We did it the later way in 2014. It typically took an hour or more to change a wheel. 148 did it in 2014 the first way and it would take them 5 minutes or less to change out a whole butterfly module.

18-08-2015 23:09

RoboticDaymon

Re: pic: Butterfly Drive Concept

The modules should be able to be installed as a complete assembly. They were designed to be put together outside the robot then slide into place. The only parts that might need to be assembled while on the robot are the pneumatics and the drive axles directly off the gearbox.

On a different note after some feedback from my team today there are a few different variations on the design i will be working on. I will post these revisions as soon as i finish the CAD for it.

19-08-2015 00:08

Chak

Re: pic: Butterfly Drive Concept

Are you direct driving one of the wheels straight off the gearbox? If so, you might want to consider how hard it would be to slide the module onto the drive axle. You can't completely assemble the module separately if the gearbox output shaft is required to hold the module together. the direct driven wheel and everything floating in the module would have to line up perfectly to slide the module on. That's really annoying, especially if you're using hex. BTW, I'm assuming these things because it's a COTS gearbox.

My team had a similar design for our octocanum modules this year, and I regret not considering assembly when we designed it. I always chose to assemble half the module on the robot instead of frustratingly trying to lining up all 5 hex components.