pic: Team 610 Off-Season Tank Drive Prototype



Team 610 has been working on a prototype tank drive system since the end of of last season. We saw great advantages in last year’s game to implement a tank drive system and saw that it would be a useful prototype that we could possibly implement in our future designs. We did a lot of research on to the advantages and disadvantages of implementing a tank drive system, much of which tells us that for most games there may not be an advantage over our traditional 6-wheel design. Thanks to team 1114 for all the information and resources that you shared, your success last season was our main inspiration to create this prototype. And great job by Andrew Yeung who took on the task of CADing this drive system. We designed this in a way so that we could hand machine all the parts in our shop. We are currently in the process of machining the parts and will post pictures of the finished prototype later.

so how are you going to trnansfer the power to the treds? aren’t the drive wheels not in the middle of the robot?

Looks nice. I have one question. How do you tension the belts?

Keep tweaking it, because teams last year went through lot of belts at the competitions. One of my mentors once said, “A design is never perfect, there is always something you can work on and make it better.”

Also, I wanted to point this out. Looks like team 1114 is really out there helping teams out. About two nights ago Tyler and Karthik helped me out big time. Tyler (holtzman) talked to me for about 3 hours about the chassis they have had in the past and the ones they have been working on. I can’t imagine how much I learned from them. They are the reason, team 1345 has a prototype chassis designed and somewhere close to be manufactured. So, thank you team 1114.

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… I am going to go ahead and try to answer the question George asked above. If you look closely they have a sprocket all the way in the back which drives the pulley. They are running a chain from the AM shifter to that back sprocket. I hope that helps you understand.

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Looks very nice, just a few questions…

How are you going to drive the belts off of the drive wheels?
Why not move the transmissions to the back in order to give more pushing power if pushing from that side?
How are your going to run a chain from the transmission when the sprocket seems to be mounted below the drive wheel?, the tranny housing will be in the way.
And finally
Why is the frame so “skimpy” for a tank like that?, if you want a powerful drive train build a frame to take a lot of beatings

Neat. I think our team was going to try to prototype a tank tread style drive train after seeing their success in last years game, but I don’t know how far they got.

I like the use of sheet metal, it looks like a nice cheap way to build a strong frame. It looks like you may want some diagonal braces in there though, it doesn’t appear to have too much to prevent it from getting knocked out of square. I might be missing something, though. I look forward to seeing how it turns out, looks like fun!

How are you going to drive the belts off of the drive wheels?
Why not move the transmissions to the back in order to give more pushing power if pushing from that side?
How are your going to run a chain from the transmission when the sprocket seems to be mounted below the drive wheel?, the tranny housing will be in the way.

Wow thanks for all the questions. So to drive the belts there is going to be #35 chain from the gearbox’s to the rear sprockets (you can see one in the back left corner). The reason the gearbox’s are place in the center and not in the rear is because of the HUGE importance of keeping the center-of-gravity over the center idlers in a tank drive system. In my discussions with 1114 they couldn’t stress this point enough to me, how important it is to have the CoG centered. The sprocket is mounted directly on the rear axle, the drive wheel (pulley in this case) is 4" diameter and there is plenty of clearance for the transmitions.

Why is the frame so “skimpy” for a tank like that?, if you want a powerful drive train build a frame to take a lot of beatings

the reason this design is so “skimpy” is because of our experiences last year and having to drill thousands of holes in out robot you can say we are a little weight conscience :stuck_out_tongue: . Also, this is a prototype, it is designed to be simple and prove the concept. In an age with bumpers there is no need to have 1/2" aluminum walls for your robot to survive a season, but yes for a FIRST robot we would beef it up a bit. As well we were only able to find 1/4" thick 3" square aluminum, where this CAD is 1/8" thick. So the real thing will be beefier that this CAD makes it look.

We are actually planning on testing two different spring tensioner system. The first one is on there, if you look closely at the top of the tracks you can see an area cut out where we have a tensioner pushing up on the bottom of the track. Also, we are planning on testing the traditional spring tensioner pushing on one of the wheels to tension it.

I like the use of sheet metal, it looks like a nice cheap way to build a strong frame. It looks like you may want some diagonal braces in there though, it doesn’t appear to have too much to prevent it from getting knocked out of square. I might be missing something, though. I look forward to seeing how it turns out, looks like fun!

We just bought a new break/shear system which we will be using for the first time on this robot. We have heard a lot of great things about working with sheet metal, it will be interesting to see how this build goes for us.

thanks for all the questions, keep them coming,
Jonathan Norris

Andy Y. here,
Designer/CADer of the tank drive

Thank you for your questions. It could help us later after we build it in troubleshooting problems. I see Jonathan Norris has already answered the questions above. I’ll check for further questions if any of you have some.

Note: Special thanks to Jonathan Norris, Derek (our amazing lab technician), Mr. Morrison, and Mr. Grant for helping me with the tank drive design. Without them it would no doubt have been a half baked job.

Andy

I don’t know if it’s worth the hassle of dealing with ordering from the US, but onlinemetals.com has 3"x3"x.125" tube.

1/4" wall is an enormous weight penalty and very likely much too beefy for nearly anything you’ll throw at it.

Thank you for the site reference. We chose to use 1/4 in thick 3 in square for several reasons. Firstly, yes it is stronger. Secondly, we wanted the extra weight for our prototype since we won’t have the weight of a robot on top of it. And finally, I forgot to add the wall thickness on my parts list XD so we got 1/4 instead.

Andy

Looks great :smiley:
what are you thinking for mph or fps ?

Tim

Hello Tim,
With the tank drive, we probably won’t get as high a speed as we could with our last year’s 6 wheel drive. I personally would be happy with a speed of up to around 5-10 ft/s (with or without weight). We haven’t done any tests yet so that is what this prototype is for. Using this, we will be able to decide our drive system (6-wheel, tank drive, etc.) depending on the challenge.

Andy

Just wanted to share a pic of our tank tread tensioner design. We came up with this design after breaking so many belts in 2004. We only broke 1 belt in 2006, and we believe that was due to someone overtensioning the tread in the pit.

Basically, for each of our tread modules, the non-driven pulley wheel axle rides inside slots on the frame. A u-shaped 1/4" aluminum assembly straddles the pulley wheel. This U-assembly is pushed by a bolt which passes through a threaded hole on a thicker frame member. Turning the bolt pushes against the U-frame and provides the tension adjustment. A jam nut lets us lock the bolt into position once the sweet spot has been found.

Big? Yes. Beefy? No doubt. But the results speak for themselves.





Sweet Design. We were thinking of the same thing, except instead of an adjustable screw, Derek (lab technician), our mentor, and I discussed a spring loaded system where a piece of u-channel would keep constant regular pressure on the 2 pulleys maintaining tension. Ofcourse we would have to calculate the tension needed to ensure we don’t over/under tighten the belt like you mentioned. Thanks for the pic :D; sweet drive design too.

Andy

45’s tensioner in 2003 was pretty cool

That’s interesting. I’d seen that pic quite a bit before, but never realized exactly what that piece did. Now I know! :slight_smile:

There was a pretty good discussion on tracks a while back here. It’s worth reading.