Our Banebots Experience

[Daniel_LaFleur]

I will add our experiance with Banebots and their transmissions at the BAE GSR in New Hampshire.

First off, our drivetrain setup.

4 wheel drive, Skid steer, direct drive, 1 CIM motor per wheel, high traction tires, 16:1 upgrade kit. We are a ramp bot and play solid defense.

When we sent in for our 16:1 hardened plates, Banebots sent us 3 (not 4) 12:1 plates. Since we assumed these were the 16:1 (4:1 secondary stage) plates we just figured we'd pick up 1 more at the regional (since they said they would have spares there). Well needless to say, they did not have any stocked at the regional. The spare parts guys called Banebots and their rep brough us 1 16:1 hardened carrier plate (which is what we asked for) in about an hour.

A couple of hours later (still on Thursday) we took apart our transmissions and found out that they had shipped us the wrong type. At this point we had no choice but to go with the unhardened 16:1 transmissions. The only thing we did to 'protect' these transmissions was to have a software ramp up / ramp down.

8 compitition rounds, and 7 elimination rounds later we (and our wonderful alliance partners 501 and 175) won the BAE GSR. We played each match running hard defense and pushing those transmissions to the limit and they never failed us. They now have more that 30 degrees of backlash and our 'bot doesn't really want to drive straight, but they held out.

So, just to back up what Dr. Joe has been saying all along, These transmissions are not bad. They are inexpensive and we (as robotics teams) tend to push these things beyond their tolerances. We will have to replace them before the Championship event, but we knew, going in, that these may not survive.

All, in all, I believe that these transmissions are good as long as you understand their limitations.


JMHO
--Dan L.

[Hieb]

Originally Posted by Daniel_LaFleur

So, just to back up what Dr. Joe has been saying all along, These transmissions are not bad. They are inexpensive and we (as robotics teams) tend to push these things beyond their tolerances.

Perhaps someone can help me out here then (now that it's after the fact for us). I thought I had done the calculations correctly, but apparently not.

I had a 3.5 foot arm, total weight about 6 pounds. Using the 540 motor into the 64:1 gearbox, we then stepped down 28:10 and 70:10. The few times before shipping that we were able to test the arm it worked fine except for the backdrive. Then on ship day we fried the motor while driving it to the crate.

On Thursday we replaced the motor and swapped the 64:1 with a 125:1 gearbox. We proceded to fry 2 more motors before scrapping motors and switching to pneumatics (which were also abandoned for lack of time and a better strategy).

Also of note--we had a 20 amp breaker on the motor (stall current 42 amps) and in one practice match we completely drained a battery and the motor smoked with only 2 seconds left in the match.

Have I just messed up my calcs and completly abused these poor motors, or is there another issue here?

[WaterFreak]

Originally Posted by Hieb

Perhaps someone can help me out here then (now that it's after the fact for us). I thought I had done the calculations correctly, but apparently not.

I had a 3.5 foot arm, total weight about 6 pounds. Using the 540 motor into the 64:1 gearbox, we then stepped down 28:10 and 70:10. The few times before shipping that we were able to test the arm it worked fine except for the backdrive. Then on ship day we fried the motor while driving it to the crate.

On Thursday we replaced the motor and swapped the 64:1 with a 125:1 gearbox. We proceded to fry 2 more motors before scrapping motors and switching to pneumatics (which were also abandoned for lack of time and a better strategy).

Also of note--we had a 20 amp breaker on the motor (stall current 42 amps) and in one practice match we completely drained a battery and the motor smoked with only 2 seconds left in the match.

Have I just messed up my calcs and completly abused these poor motors, or is there another issue here?

Not sure if I can help, but have a question....

Are you sure that you fried the motors???? We had some problems (you can read in a previous post in this thread) with these motors, thought we had fried the motors, but ended up a transmission problem.

You might want to take the transmissions apart and check the final stage of the planetary gears, where it meets the drive shaft. Also, check the motor when it is disconnected from the transmission.

[Daniel_LaFleur]

Originally Posted by Hieb

Perhaps someone can help me out here then (now that it's after the fact for us). I thought I had done the calculations correctly, but apparently not.

I had a 3.5 foot arm, total weight about 6 pounds. Using the 540 motor into the 64:1 gearbox, we then stepped down 28:10 and 70:10. The few times before shipping that we were able to test the arm it worked fine except for the backdrive. Then on ship day we fried the motor while driving it to the crate.

On Thursday we replaced the motor and swapped the 64:1 with a 125:1 gearbox. We proceded to fry 2 more motors before scrapping motors and switching to pneumatics (which were also abandoned for lack of time and a better strategy).

Also of note--we had a 20 amp breaker on the motor (stall current 42 amps) and in one practice match we completely drained a battery and the motor smoked with only 2 seconds left in the match.

Have I just messed up my calcs and completly abused these poor motors, or is there another issue here?

The biggest issue with the 540 motors (from what I've heard) is running them to 'hold' position because they have poor heat dissapation when not moving (I believe that their cooling is directly related to the shaft moving). As such, when you are powering the motor to hold a position, it heats up very quickly and then lets the magic smoke out. This is compounded even more if you are at stall current.

Example of 'hold position': An arm that is extended and would backdrive quickly (due to gravity, etc) if the motor did not have current running through it. This can be checked by putting an ammeter inline while running the arm in 'hold' position.


The 20 amp snap-action breakers only trip if current is ABOVE 20 amps for considerable time (the amount of time is dependent on the current since the breaker is a thermal device). They also quickly reset and reapply the current to the device, not giving the motors enough time to cool. Spikes can eliminate part of this problem because they have an integrated fuse, but if that fuse goes you lose all functionality of the device it controls.

[114Klutz]

Suprisingly, the BaneBots seem to be working well for us. We're using a 36:1 coupled with a FP motor to drive our elevator - it's been working fine without any problems so far.

[Bruce Newendorp]

I also would like to provide my Banebot transmission experience during the build season and the first week of regional competition.

Our team decided early in the build season to use the Banebot 56 mm transmissions with 2 CIM's per side. We purchased the 2 motor kits and got the basic chassis and drive train done early giving us time to work on the tube handler, ramp and autonomous code. When the transmission problems surfaced, we considerd replacing the Banebots with AndyMark's but decided to not take the time to do it.

We are using a 4 wheel drive 38" wide X 28" long skid steer configuration with 4" Colson's on the back and 4" hard plastic wheels in front. There are 2 CIM's per side with the 12:1 reduction 56mm planetary gearbox. The output shaft has two 17 tooth sprockets and the Banebot beraring support at the end. Each drive wheel has 12 tooth sprockets.

We ran the robot a lot during testing and demonstrations before we shipped. I was monitoring the backlash and it was not bad.

We received the replacement carrier plates and spent the first two hours Thursday at the St. Louis regional reinstalling the transmisisons into the robot. We just made it to our first practice match. The robot performed well throughout the practice sessions.

Just at the end of our autonomous run during our first qualifying match on Friday, the dreaded "one side turns and the other doesn't" happend to us. The transmission output shaft rotated freely. Disassembly revealed the pins had come out of the carrier plate and one of the planet pinions had the teeth stripped off. There is no way to know for sure whether the pins came out first or the gear stripped first.

Thanks to Team 461 we had a replacement part to install. We missed one match while we made repairs. There were no more failures during qualifying or during our two rounds of finals matches but we always had that lingering concern about when the other one will fail.

One of the things we emphasize to our students is to make the robot simple and reliable. The competition site pit is not the place to be making major repairs. Unfortunately, the Banebot transmission did not hold up its part in making our robot reliable. I think the transmission design is good but it appears the manufacturing quality plan failed.

Next year we will do what it takes to have a reliable drivetrain.

I really wish this were better news for those of you who are using the Banebot transmissions.

[Andrew Blair]

Perhaps everyone with old carrier plates should get the pins out and press them into the new plates with press-fit loctite. We'll have an arbor press at competition...

[Nick02]

We (dukes #991) at the elimination rounds in phx stripped out bb gearbox plate out.
We had the stock plates and during lunch I noticed that the drive shaft turned ¼ turn freely. The motors are in the worst part of the robot to get to taking them out would take at least an hour. The team captain said “lets just run with it” I agreed, and for two matches it did fine until our drive wheels became “spinners”. Needless to say we had to dropout since we couldn’t fix the problem in time. And yup the output plate was stripped crappy gearbox!@@@
the gearboxes's now make nice gyroscopes.
http://www.youtube.com/watch?v=p_D4-l_wOGo