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Chameleon Drive

Nate Bloom

By: Nate Bloom
New: 06-26-2012 07:27 PM
Updated: 06-26-2012 07:27 PM
Views: 1571 times


Chameleon Drive

This is a universal chassis that I thought up and designed in the last couple months, and is also my first full CAD project.

The concepts behind the chassis are:
1: It can be completely built with only basic shop equipment (drill press, band saw, etc.)
2: It can accept as many basic drive trains as possible (though only a few are shown):
4WD
6WD (dropped or flat center)
8WD (dropped or flat centers)
10WD (with slightly uneven spacing)
Omni (slide style)

The drop or lack thereof is acheived by rotating the center bearing plates 180 degrees. Their holes are 1/16'' of an inch below the center of the bars, while the holes for the other wheels are 1/16'' above the center of the bar.

Specs:

Bars: 3'' x 1'' x .125'' 6061 Aluminum
Wheels: 6''
Drive: ToughBox Nanos with chains to any unpowered wheels
Overall: 35 x 26.9''

This is version 9, and I am about to start verion 10, which will move from hex to standard axles to reduce costs. Any other suggestions would be more than welcome.

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06-26-2012 09:10 PM

LeelandS


Unread Re: pic: Chameleon Drive

Wow. I'm not much of a mechanic, but I find this concept EXTREMELY interesting. Very well done.

I love the potential versatility! Any chance this would get built so we can hear about it in practice?



06-26-2012 09:23 PM

akoscielski3


Unread Re: pic: Chameleon Drive

Interesting Concept.

Would you always leave the extra bearing blocks inside the chassis or would you take them out to save weight? how easy is it to get at the transmissions and wheels if you wanted to change them?



06-26-2012 09:36 PM

Peck


Unread Re: pic: Chameleon Drive

What size wheels are max and min for each set up? how strong is it? how heavy is it?

as i see it right now, it's worth looking at for a test chassis or demo bot but not for an actual competition bot.



06-26-2012 09:56 PM

Gray Adams


Unread Re: pic: Chameleon Drive

Changing from hex to keyed shafts only reduces costs if you don't value your repair time at competition.



06-26-2012 10:28 PM

jblay


Unread Re: pic: Chameleon Drive

Quote:
Originally Posted by Gray Adams View Post
Changing from hex to keyed shafts only reduces costs if you don't value your repair time at competition.
I love this idea, very versatile. You can argue that the same things can pretty easily be done with the kit chassis.

Is there a reason for not centering the gearbox and motor assemblies? It's a minor thing but it makes your COG much nicer. Also I don't really see the need for the second omniwheel for strafing on the slide drive. I guess it makes you faster at it but not really worth the weight of the wheel, motor, and gearbox especially cause you can use a CIM somewhere else on your robot by not using it there.



06-26-2012 10:55 PM

Nate Bloom


Unread Re: pic: Chameleon Drive

I apologize in advance for this massive response, I just wanted to address everyone's questions/comments.

Quote:
Originally Posted by LeelandS View Post
Wow. I'm not much of a mechanic, but I find this concept EXTREMELY interesting. Very well done.

I love the potential versatility! Any chance this would get built so we can hear about it in practice?
Thank you, we will hopefully build this as an off-season project to test its viability, in which case I will post results.

Quote:
Originally Posted by akoscielski3 View Post
Interesting Concept.

Would you always leave the extra bearing blocks inside the chassis or would you take them out to save weight? how easy is it to get at the transmissions and wheels if you wanted to change them?
I feel that it would be better to leave them in because it allows for faster changes between drives. I intentionally left out anything on the bottom of the robot, with the idea that we could raise the robot and have easy access to the necessary bolts under it. This would theoretically mean that switches could be very quick with a few people.

Quote:
Originally Posted by Peck View Post
What size wheels are max and min for each set up? how strong is it? how heavy is it?

as i see it right now, it's worth looking at for a test chassis or demo bot but not for an actual competition bot.
4WD: 4''-10''+
6WD: 4''-10''
8WD: 4''-8''
10WD: 4''-6''
Omni: 4''-8''+

I would be cautious about 4'' wheels however, due to the three inch bars. The strength is hard for me to predict, but it is entirely .125'' aluminum and bolts. The weight should be about 30 lbs, but there is a lot of estimation in that.

Right now it is very much in the conceptual stage, and hopefully we will build it as a test chassis to determine its viability.

Quote:
Originally Posted by Gray Adams View Post
Changing from hex to keyed shafts only reduces costs if you don't value your repair time at competition.
Really? Our team doesn't have much experience with direct drive, so I hadn't assumed much of a difference.

Quote:
Originally Posted by jblay View Post
I love this idea, very versatile. You can argue that the same things can pretty easily be done with the kit chassis.

Is there a reason for not centering the gearbox and motor assemblies? It's a minor thing but it makes your COG much nicer. Also I don't really see the need for the second omniwheel for strafing on the slide drive. I guess it makes you faster at it but not really worth the weight of the wheel, motor, and gearbox especially cause you can use a CIM somewhere else on your robot by not using it there.
I feel that the big advantage this has over the kit chassis is that it allows easier access and switching between these different drives without modifying the frame itself at all.

As far as the centering, it was simply difficult to accommodate for a dropped or flat wheel with the gearbox also attached.

I debated the second omni wheel for a while, so version 10 might be able to accept either 1 or 2 strafing omnis. That's definitely back up on the consideration list, thanks.



06-26-2012 11:07 PM

Gray Adams


Unread Re: pic: Chameleon Drive

Quote:
Originally Posted by jblay View Post
I love this idea, very versatile. You can argue that the same things can pretty easily be done with the kit chassis.

Is there a reason for not centering the gearbox and motor assemblies? It's a minor thing but it makes your COG much nicer. Also I don't really see the need for the second omniwheel for strafing on the slide drive. I guess it makes you faster at it but not really worth the weight of the wheel, motor, and gearbox especially cause you can use a CIM somewhere else on your robot by not using it there.
I'm not saying the chassis is a bad idea, I actually really like it.
Quote:
Originally Posted by Nate Bloom View Post
Really? Our team doesn't have much experience with direct drive, so I hadn't assumed much of a difference.
We had a grand total of one keyed shaft on our robot this year. We lost the key half a dozen times. Sure you could put more effort into the design and build such that it isn't an issue, but hex is just simpler, more easily repaired and maintained.

The bearings are a bit more expensive, but you could not convince me to go back to keyed shafts. More pieces, less strength, harder to deal with over all. The only advantage is that you can use round bearings (without using a sleeve), which are extremely common and widely available.

I'd really like to try out a drive system that goes 1/2" hex -> 1/2" round -> 7/16" hex. It would be a bit of a luxury, but not unreasonably so (especially if you have a machining sponsor to save you the cost of the necessary tools if you don't have them).



06-26-2012 11:12 PM

IanW


Unread Re: pic: Chameleon Drive

Interesting idea. Just a couple suggestions:
Unless you are planning to weld this, I'd suggest beefing up the gussets between the siderails. Add a few more rivet/bolt holes to them, especially on the insides.
With cantilevered wheels like this, I'm not sure if having the sprockets on the outside of the wheels would be the best idea. If you can figure out how to move them to the inside of the chassis or even to the other side of the wheels without violating your design goals, I'd recommend it.
Finally, I don't think it should actually be used for competition. If you use it for preseason R&D, the modularity could be beneficial, but for competition, choosing one design and sticking with it is almost certainly better. This way, you don't have to make concessions on other parts of your robot just to accommodate this drivetrain.

All told, very nice job for your first CAD project. Keep taking on new projects - it's an excellent way to get better.



06-27-2012 12:19 AM

DampRobot


Unread Re: pic: Chameleon Drive

Cool idea. Although I like the concept, I feel like weight might become a bit of an issue. You have to carry around all that plate and bearings even if you never use them.

Also, do you have any plans for bumpers? These tend to get left out in most drive train designs until the end. You may have trouble supporting the bumper to what the manual requires (I believe every ten inches) with the three bearing blocks in a row.



06-27-2012 07:43 AM

JesseK


Unread Re: pic: Chameleon Drive

"Chameleon Drive" implies the thing blends into the background ... yet I totally see all of that drive in all configurations o.O
(Ok, I kid...)

The most basic piece of this 'drive' is the H-frame. Your H-frame setup is very verstatile. However, I don't think the gearbox configurations are. For the 8WD and 6WD tank variants, why not just use the CIMple boxes that come in the KOP? The chain runs are easily tensioned by sliding the transmission, it's lighter overall, c.g. is lower overall, and the sprocket reductions are adjustable so you aren't stuck with purchasing ~$100 in gears just to get the right speed for a given year.

For the slide drive (your bottom pic), you may find that the robot doesn't need to slide sideways as fast as it moves forward/back. If this is what you find, you may be able to use 2 RS-550's (properly geared...) in lieu of 2 CIMs, thereby putting the 2 CIMs back on the outer wheels for better power characteristics during normal play.



06-27-2012 09:20 AM

Jon Stratis


Unread Re: pic: Chameleon Drive

Two thoughts on what looks like a great design:

- For use as a test chassis, how about emulating AndyMark's nano tube chassis and running power between the wheels inside the frame? That way, you could have every wheel slot powered all the time, making swapping drive trains even easier (just pull off one set of wheels and put on another!)

- If you want to use this for competition, keep the weight rules in mind. Swappable systems like this are really cool, but all of the hardware used in every configuration you bring counts towards your weight limit. So, if you plan to swap between traction and omni wheels at competition, you'll have to weight both sets of wheels with your robot, even though only one set will be on the robot at a time. See R03 in the 2012 game manual for specifics (it's been in the manual that way for years, I doubt the rule will change in the future).



06-27-2012 09:39 AM

Jon Stratis


Unread Re: pic: Chameleon Drive

One more thought... why not push the two cross bars towards the outside a bit more, and set them up for 3 wheels each? That would give you the option of using the center for a strafing wheel like you have now, or setting it up for a wide drive base design, with no wheels on the long side.



06-27-2012 10:03 AM

JVN


Unread Re: pic: Chameleon Drive

Looks pretty cool.

A few comments:
1. Figure out your bumper mounting. This is something most people ignore until the "end" but the sooner you think about it the happier you'll be with the implementation.

2. I've found the 6" diameter AndyMark omni-wheels work a lot better when they're run as duallies -- you should consider that for your H-Drive implementation.

3. I believe you're sacrificing some functionality at the expense of versatility. "Jack of All Trades, Master of None." In my experience, it is very very very rare for a team to switch drive styles mid-season. As a result, it might be better for you to CAD several different configuration specific designs, knowing that you'll be able to do subtle things to make them better than this one design that does all of them. If you prioritize versatility enough that you're willing to make tradeoffs (they may be big, they may be small) then you have nothing to worry about. Your mileage may vary.

-John



06-27-2012 12:21 PM

IKE


Unread Re: pic: Chameleon Drive

Very cool design. I agree with a lot of the other commenters that this looks like a really neat and versatile test chassis. I would suggest talking with your programmers about sensor incorporation and programming goals. A chassis like this could go from good to great with good iterative software and driver interface development.
Even if it is a test chassis, the addition of good bumper should enable you to have a defensive sparring partner.



06-27-2012 02:05 PM

Peck


Unread Re: pic: Chameleon Drive

one more comment: where are you putting your speed controllers and other nessesary hardware?



06-27-2012 02:36 PM

Akash Rastogi


Unread Re: pic: Chameleon Drive

Nice first full project, Nate. Here are a couple things you can check out to help you iterate; another person a while back had a similar idea.

http://www.chiefdelphi.com/forums/sh...ad.php?t=95179

http://www.chiefdelphi.com/media/photos/36921

As with the above project, it could be a great project to make in the offseason to test different drives, but it most likely is not the practical design for a competition robot.

Also, this may be a good chance for you to learn how to create configurations of your assembly within Solidworks.



06-27-2012 02:42 PM

Garret


Unread Re: pic: Chameleon Drive

We switched from swerve to Mecanum at the LA Regional this year; this was because we accidentally fried our swerve steering motors when calibrating the PID at San Diego and didn't want to deal with it at LA. We were able to do this very fast because we design our drive train in modules. Each module uses the same of mounting and has everything already built in (except controllers).

I really like a of things about the the OP's design, especially the design around limited manufacturing capabilities. Also, it looks like it should be able to accept mecanum as well because of the corner gearboxes. Great work!



06-27-2012 04:31 PM

mikemat


Unread Re: pic: Chameleon Drive

Just out of curiosity, how much time do you think it would take to change the drive types? It would add a neat dynamic if you could be a 6- or 8-wheel drive for quals, then switch to mecanums or a slide drive in elims so you can triple, or change drives between matches to better suit your opponents and partners.



06-27-2012 04:44 PM

Peck


Unread Re: pic: Chameleon Drive

Quote:
Originally Posted by mikemat View Post
Just out of curiosity, how much time do you think it would take to change the drive types? It would add a neat dynamic if you could be a 6- or 8-wheel drive for quals, then switch to mecanums or a slide drive in elims so you can triple, or change drives between matches to better suit your opponents and partners.
dude, you would take up your entire weight allowance in just the drive train and be unable to master how the robot drives.



06-27-2012 05:07 PM

mikemat


Unread Re: pic: Chameleon Drive

Quote:
Originally Posted by Peck View Post
dude, you would take up your entire weight allowance in just the drive train and be unable to master how the robot drives.
If you shipped as pictured in 6 or 8wd configuration, all you would need to bring would be the mecanum wheels. A slide drive would be harder because you would need an extra gearbox and motor controller, but not impossible with 30 pounds. I can't speak for driver training, but judging from the teams that already switch mid season, it isn't impossible to adjust to a different drive.



06-27-2012 05:24 PM

EricH


Unread Re: pic: Chameleon Drive

Quote:
Originally Posted by mikemat View Post
If you shipped as pictured in 6 or 8wd configuration, all you would need to bring would be the mecanum wheels. A slide drive would be harder because you would need an extra gearbox and motor controller, but not impossible with 30 pounds. I can't speak for driver training, but judging from the teams that already switch mid season, it isn't impossible to adjust to a different drive.
Modular systems are allowed on a robot, but if a robot can have extra configurations--example, two arms that have different functionality--either you stick with one configuration (or do a permanent change and request reinspection) or all the configurations together must be under the weight limit. That's been in the rules for as long as I can remember.

The governing limit here isn't the Withholding Allowance. It's the robot weight. I don't think that most teams would like cutting into the 120# allowance by 15# or more.


However, I think this sort of drive system could be invaluable to a team, not necessarily in competition use but as a practice robot. Build it Day 1, throw a bunch of tests at it to figure out drive base for the year, use as a practice defender or build the rest of the robot on top of it. It's not unheard of for a competition robot to be designed to handle two different types of drivetrain, but only use one in competition.



06-28-2012 04:04 PM

mschwab013


Unread Re: pic: Chameleon Drive

This is so cool! Can you possibly send me the CAD file so I can show it to my team and we might try and build a prototype of it to see how well it works



06-29-2012 02:09 PM

Nate Bloom


Unread Re: pic: Chameleon Drive

Again, thanks for all of the comments and suggestions! I am taking all of this into consideration with version 10, so this has been a huge help.

Quote:
Originally Posted by IanW View Post
All told, very nice job for your first CAD project. Keep taking on new projects - it's an excellent way to get better.
Thanks, I have been in leadership except for my freshman year, so once in a while it is nice to get back to what I really love about robotics.

Quote:
Originally Posted by Peck View Post
one more comment: where are you putting your speed controllers and other nessesary hardware?
I was hoping to leave the bottom free, but I will try to work around integrating the electronics in the chassis with version 10, especially since we are likely first building this as an independent chassis.

Quote:
Originally Posted by Akash Rastogi View Post
Nice first full project, Nate. Here are a couple things you can check out to help you iterate; another person a while back had a similar idea.

http://www.chiefdelphi.com/forums/sh...ad.php?t=95179

http://www.chiefdelphi.com/media/photos/36921

As with the above project, it could be a great project to make in the offseason to test different drives, but it most likely is not the practical design for a competition robot.

Also, this may be a good chance for you to learn how to create configurations of your assembly within Solidworks.
I was actually inspired by 159's description of their bearing blocks on their final robot. I hadn't realized that it was originally such an adaptable frame, and I only saw them use 8WD in competition.

Quote:
Originally Posted by mikemat View Post
Just out of curiosity, how much time do you think it would take to change the drive types? It would add a neat dynamic if you could be a 6- or 8-wheel drive for quals, then switch to mecanums or a slide drive in elims so you can triple, or change drives between matches to better suit your opponents and partners.
I tried to keep everything simple and easily accessible, with the idea of changing sets between quals and elims, or maybe even between matches in mind. That said, it may be more difficult accounting for weight and having a driver trained for both drives, as others have mentioned.



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