24-06-2015 17:05

cbale2000

Re: pic: FTC Custom Drive Train

You might want to consider offsetting one of the motors on each gearbox up a bit to allow the gearboxes to be removed more easily if needed (might also help with wire access to the motors). We've had issues in the past where we didn't allow enough clearance to do maintenance on our gearboxes and it proved problematic.

Otherwise it's a very nice looking drive, I initially mistook it for an FRC bot. =)

24-06-2015 17:39

Gregor

Re: pic: FTC Custom Drive Train

It's hard to tell from the AM page if the motor leads stick out straight back or if they come out the side, but if they stick out straight back your motors may need to be further apart.

24-06-2015 17:47

GarrettF2395

Re: pic: FTC Custom Drive Train

What an awesome render!
I noticed the 90deg gussets you've got on top, but how are you planning on attaching the bottom 1x1 tubes to the drive modules?
The way it's set up now looks like you plan on welding it.

24-06-2015 18:06

hectorcastillo

Re: pic: FTC Custom Drive Train

Thanks for the feedback! It hasn't occurred to me to offset the motors to make it easier to remove the gearbox and give room for the wires. Thanks. As far as how the bottom tubes are attached, they are riveted onto small plates with tabs that fit into small notches in the larger side plates. These small plates are installed during the assembly of the module.

Here's a closer look:
https://drive.google.com/file/d/0B8z...ew?usp=sharing

24-06-2015 18:07

MattRain

Re: pic: FTC Custom Drive Train

They stick out the side. The encoder cable sticks out the back slightly but can be bent up right away.

24-06-2015 18:15

FTC5110

Re: pic: FTC Custom Drive Train

Nice. Do you have a weight estimate?

24-06-2015 18:19

carpedav000

Re: pic: FTC Custom Drive Train

Those white wheels are illegal for FTC. AM designed stealth wheels to take their place

24-06-2015 18:40

Jeremy Germita

Re: pic: FTC Custom Drive Train

Looks great! I love how flexible the FTC rules are getting and I'm excited to see how teams are taking advantage of those rules.

Remember that FTC fields are 12' square(thus far), 6-7 feet per second would clear the field in about 2 seconds. That's ridiculously fast for this scale. Scaling that up to FRC field sizes, it's like gearing for 30+fps free speed.

Here is a custom FTC drivetrain I built a couple of years ago. I clocked it at just under 3 feet per second without any mechanisms on the robot, but it ended up being about 2.5 f/s during competition. I found it was on the cusp of controllability on an FTC field. When 72 made v2 of that drivetrain last season, they geared it for 4fps and the NXT loop execution rate was definitely too slow to control the drivetrain without lag. It would travel about 4-6" between motor controller updates.

Just a warning. These may or may not be valid concerns for the 2015-16 game and control system .

24-06-2015 19:15

hectorcastillo

Re: pic: FTC Custom Drive Train

As of right now it weighs around 13.25 lbs.

Those are actually 4" VersaWheels from VexPro. Although the color and tread pattern does look similar.

Thanks. When I was deciding on my gear ratios I knew I wanted something fast, but I wasn't exactly sure how fast was fast and how fast was too fast. But I figured that someone here could point me in the right direction so that I can make the right adjustments.

25-06-2015 17:19

ehochstein

Re: pic: FTC Custom Drive Train

First off - I love the look of this chassis. My students put something together something that looks similar to this last year. I'll see if one of them can send me a photo and I'll post it.

How do you plan on attaching the motors to the gearboxes? I would assume the 6 mounting holes on the face, loctited?

26-06-2015 01:17

Fusion_Clint

Re: pic: FTC Custom Drive Train

I love it, we are going to try incorporating the FRC Texas tubes this summer on the FTC scale.

I have a question, FTC normally requires the robot to pick up something, how to you plan on this drive-train allowing that? I would suggest leaving the "front" somewhat open.

26-06-2015 01:41

hectorcastillo

Re: pic: FTC Custom Drive Train

There are holes in the gearbox plate that line up with two of the 6 mounting holes on the motor, and yes, I would probably use a little loctite, but not too much in case I need to remove a motor later.

26-06-2015 01:50

hectorcastillo

Re: pic: FTC Custom Drive Train

I originally had the front left open without the front tube. I made it so that you can open up the front and back to fit the needs of the game. Removing the top tubes would make it a little less sturdy, but there are plenty holes along the top of the drive modules to mount whatever structure you need to provide stability and not be in the way. I wanted this design to be as dynamic as possible since we don't know what the next game is going to be.

27-06-2015 01:46

Nemo

Re: pic: FTC Custom Drive Train

Two things:
1) Very cool looking design. I hope you folks end up building something like this.
2) Thanks for bringing my attention to those BaneBots 6mm adapter hubs! That removes a pretty significant barrier to some of the FTC ideas we've tossed around on our teams.

27-06-2015 15:51

ehochstein

Re: pic: FTC Custom Drive Train

I would suggest using more than two of those holes, we found that using a minimum of 3 worked best.

The gears you are using don't appear to be tetrix gears, what are you plans on mounting them to the output shaft? We've been looking for alternatives to the tetrix gears and would be interested if you found a solution! Currently, we are looking at manufacturing our own solution.

27-06-2015 17:14

hectorcastillo

Re: pic: FTC Custom Drive Train

Good to know about the mounting holes. Thanks! I'm using BaneBots 1/2" hex hubs for 6mm bore to mount the VexPro gears into the motors.

Here's a link:
http://banebots.com/c/WHB-HM-HS4-M6

05-10-2015 20:24

IceStorm

Re: pic: FTC Custom Drive Train

Do you by chance have a close up view of just the gearbox with the Banebots adapter or be willing to share your CAD file. were needing to use a 1/2" sprocket for our drive train this year and having a hard time understanding how I might be able to make one of these adapters work.

05-10-2015 20:31

Knufire

Re: pic: FTC Custom Drive Train

What size sprocket? AndyMark recently released this: http://www.andymark.com/product-p/am-3185.htm

05-10-2015 21:33

hectorcastillo

Re: pic: FTC Custom Drive Train

I couldn't find the CAD file for them while I was designing this, and I was kinda lazy so I didn't bother making my own. So there isn't actually an adapter in the CAD, but it's designed to use them.

It's a pretty simple set-up, though. The adapter should tighten right onto the 6mm shaft. You can then slide your sprocket onto there. The adapter has a lip on one end so your sprocket doesn't slide off that way, and it has a groove to add the retaining ring for the other side. You could probably put some spacers in there to get the sprocket into the right position. You could also cut it to length and machine your own retaining ring groove if you have access to a lathe.

If you send me a picture or a better description of what you're trying to do, I can probably be of more assistance.

05-10-2015 23:27

cadandcookies

Re: pic: FTC Custom Drive Train

Here's a CAD file of the 6mm to 1/2" hex banebots adapters that I whipped up. Both in Creo and STEP flavors. Feel free to use however you want-- this is as close to the technical drawings as I think I can get.

This one is three wide, but I can make a 1 or 2 wide if you'd like. It's a real shame that it looks like BaneBots is going to stop selling these.

06-10-2015 03:33

hectorcastillo

Re: pic: FTC Custom Drive Train

My brother managed to make one out of a piece of VEXPro Thunder Hex by drilling out the bore to 6mm on the drill press and drilling a hole in the side through which he tapped the threads for a set screw. It was pretty cool.

06-10-2015 08:52

IceStorm

Re: pic: FTC Custom Drive Train

I thought about doing the same thing with the thunderhex. we did this last year with our FRC team to adapt a 10 turn pot to a shaft to track the height of our linear lift. worked out really great only instead of drilling and tapping a hole in it we cut a slit down it and used a shaft collar to lock it back together. we may have to see if we have a piece of thunderhex around and try this out.

thanks for the cad file. and the explanation of it. do you see any reason this wouldn't work with the #35 sprockets from vex pro?

-Chad

06-10-2015 09:53

Knufire

Re: pic: FTC Custom Drive Train

#35 chain on a FTC robot?

07-10-2015 00:13

cadandcookies

Re: pic: FTC Custom Drive Train

I don't see a reason why it wouldn't work, but I'd probably go with a couple of the #25 sprockets instead of one of the #35 doubles. I'm pretty sure buying an adapter plus two of the VexPro sprockets is cheaper than getting a single sprockets from AM or Tetrix (although I suppose those have the advantage of just dropping in).

07-10-2015 10:22

Knufire

Re: pic: FTC Custom Drive Train

The biggest advantage of the AM sprocket is not having to rely on a set screw to transmit torque from the motor output shaft. AM found the slit + collar clamp method that IceStorm mentioned to be more reliable, which is what that sprocket operates on.