Fisher Price Motor Replacement Gearbox

[Joe Johnson]

Disclaimer: My company, Robotic Amusements, Inc., uses them as a source for motor/gearboxes for our robots, but other than than, I have no financial ties to Banebots, Inc. what so ever.

I just visited the Banebots website and saw the have a lot of great new products.

Old timers will recall that last year, I advocated that teams use Banebot's 36mm planetary gearbox with their Fisher Price motors. While the 36mm gearbox was much better than the plastic transmission that Fisher Price donated to the kit, to be honest, it was not as robust as I would have liked for some of the more demanding FIRST applications*.

Now I see that Banebot has a 42mm gearbox that would be a great step up in performance from the 36mm gearbox. Note that these gearboxes are shipped with an RS-550 motor (the FP motors are 550 series motors == about twice the power as a 540 series motor) but that they are designed to be used with the RS-775 motors (which are effectively drill motors => very high power motors > 300W).

While I have not held one of these jewels in my hands, I can tell you that if I were still on the ChiefDelphi team, I'd be ordering a few of these beauties right now just to find out where we could use them and to make sure we had them in case the Banebot warehouse runs short...

...I am just saying...

Joe J.

*Note: it takes about 15 minutes from start to finish to take a FP motor and get it running in either the 42mm or the 36mm gearbox from Banebots. From my point of view, it is easier and less costly to use one of these gearboxes than it is to design and build a method to mount the plastic Fisher Price gearbox and get a torque out the business end. The mount so easy and they have long juicy shafts that are easy to support if needed and make getting torque out of them is a dreams plus you get the ability to easily change ratios if you screw up a calculation (or guess wrong about the game). For $40/$60 bucks for the 36mm/42mm gearboxes, it is hard to beat.

[Greg Needel]

joe and all,
I spoke with Ed Yakey (the owner of banebots) this morning about upcoming stock and new products. He is well aware of FIRST and has stocked up on all products. There will also be a link on the front page outlining the gearboxes which are compatible with FIRST motors to make the selection easy.

In addition to the new gearbox which joe mentioned the other thing which I am very excitied to see is the new encoder option for the 42mm gearbox. For ~$38 you get a digital encoder for the gearbox which mounts directly to the output shaft of the motor. This is a very nice tool for people who wish to have some feedback on motor performance. Check them out http://www.banebots.com/p/EN-G0421-KT

I personally have used banebots for both the FIRST robot in 2006 and my most recent battlebot

I know that I will be ordering these gearboxes one it is determined what speed/torque will be needed with the FP this year.

[sanddrag]

Greg, you awesome. Thanks for doing that.

[Joe Johnson]

Originally Posted by Greg Needel

For ~$38 you get a digital encoder for the gearbox which mounts directly to the output shaft of the motor.

Just to be clear, the encoder mounts directly to the output shaft of the motor/gearbox (not the motor itself).

While we are taking about Banebot goodies, they also have a new divider board that takes the encoder output (128/rev???) and divides it down to whatever number of pulses per rev down to whatever you need (e.g. 32, or 16 or 2). It is also rumored to have a "direction" output. Both features help simplify the code and reduce load on the CPU.

And they have version for all three of the larger planetary gearboxes they sell 32mm, 42mm, & 56mm.

I have had home brew encoders fail enough times that I highly recommend that folks consider spending the $38 on these custom encoders if you need to keep track of speed and/or position. Actually, I have had high quality encoders fail often too now that I think about it... ...but the problem was always mine not the encoder: I somehow mounted them where the chain or whatever was putting too much load on the encoder shaft or where they came disengaged from the chain or belt -- the Banebot encoders totally eliminates these failure modes. Highly highly recommended.

Joe J.

[Madison]

Any idea why the encoder is sold separately for $38, but the "add encoder" option on the gearbox page (http://www.banebots.com/pc/MP-42XXX-550/MP-42036-550) lists it as $48.50?

Is it the difference between buying it preassembled and self-installation?

[Gdeaver]

I remember last season there were a couple of posts concerning these gear boxes and mounting the fisher price motor directly to the housing cutting off the air flow of the motor causing over heating. Is this still an issue. Is there enough shaft Length to allow use of spacers? You got let those can motors breathe.

[Don Wright]

We NEVER had any issues with these mounted to the fp's and ours almost ran almost continously...even for hours during practice and set-up...

[Joe Johnson]

Originally Posted by Gdeaver

I remember last season there were a couple of posts concerning these gear boxes and mounting the fisher price motor directly to the housing cutting off the air flow of the motor causing over heating. Is this still an issue. Is there enough shaft Length to allow use of spacers? You got let those can motors breathe.

Yes it is true that airflow can be the difference between a motor and a toaster. The FP motors are especially problematic because they have so much power in such a small package.

For the most part, my experience is that you will be fine with blocked air holes on the front of the motor if you design your motor to work on the left half of the speed/torque curve (and preferably on the left 1/3). But if this is not possible then you will need the flow from the front of the motor.

This is pretty easy to accomplish with simple washers or spacers because the FP motor shaft has to be shortened in order to fit with the gearbox -- all you have to do is keep the shaft a bit longer and then space the motor back a bit from the gearbox.

Joe

[Jonathan Norris]

My team last year used 2 of these gearbox's on our robot for our collection and conveyor system. We had good success with them, but had a few issues. When using these you have to remember why they are so inexpensive, they are not made from the highest quality of materials. Through the ware and tear of 2 regionals we actually had one of our two gearbox's blow up (i wish i took a pic of the insides) just before our quarterfinal match at the championship. Luckily we bought some spares and was able to fix it just in time. But if you plan on using these gearbox's in this upcoming season i would strongly recommend buying spares, we broke one output shaft early season buy making a design mistake of putting too much load on the shafts of the gearbox (bad idea), and had to replace both gearbox's during the season. Through 2 regionals and the championship my team, team 610, went through 5 of these gearbox's. So if you are using these gearbox's in a medium load situation i would recommend having spares on hand.

I am personally very interested in these new versions of the gearbox's and even with the troubles i can foresee us using the gearbox's again. They fit our needs very well and with the range of gearing options available it makes implementing these gearbox's very easy.

[Joe Johnson]

Originally Posted by Jonathan Norris

My team last year used 2 of these gearbox's on our robot for our collection and conveyor system.

I don't think that you used the 42mm gearboxes last year because they were not available last year. The 36mm gearbox was impressive for the price, but was not really up to the task of some of the heavier duty applications. I think the 42mm gearbox is a significant step up in terms of performance. Even so, I am not sure I would use them for driving my robot -- I may use them for an auxiliary drive system but my main drive is too important*.

Joe J.

*Of course this is all sight unseen. If I actually saw them I may bump up or down my advice.

[Gary Dillard]

Originally Posted by M. Krass

Any idea why the encoder is sold separately for $38, but the "add encoder" option on the gearbox page (http://www.banebots.com/pc/MP-42XXX-550/MP-42036-550) lists it as $48.50?

Is it the difference between buying it preassembled and self-installation?

Encoder Option
You can select to have an encoder mounted and calibrated on this gearmotor.

Probably cost of assembly and calibration.

[Jonathan Norris]

Originally Posted by Joe Johnson

I don't think that you used the 42mm gearboxes last year because they were not available last year. The 36mm gearbox was impressive for the price, but was not really up to the task of some of the heavier duty applications. I think the 42mm gearbox is a significant step up in terms of performance.

Yes the ones we used last year must have been the 36mm ones, I wish i took a picture of the number of destroyed planetary gears we had. When we opened one of them there were small goldish metal filings which fell out of the gearbox's, these filings were the teeth of the small planetary gears . That is why I said we were interested in these new revisions of the gearbox's, with hopefully better performance.

[Joe Johnson]

Originally Posted by Gary Dillard

Encoder Option
You can select to have an encoder mounted and calibrated on this gearmotor.

Probably cost of assembly and calibration.

Hmmm.... "calibrated" can't think what that must be -- perhaps there is a way to adjust the phasing between A & B channels and "calibrated" implies something closer to 90Deg that an "uncalibrated" one would be?

Anybody have a users manual or other input that may shed light on this question?

Joe J.

[dtengineering]

Originally Posted by Gdeaver

I remember last season there were a couple of posts concerning these gear boxes and mounting the fisher price motor directly to the housing cutting off the air flow of the motor causing over heating. Is this still an issue. Is there enough shaft Length to allow use of spacers? You got let those can motors breathe.

We used a 5:1 36mm reduction on our shooter last year. As I recall we had to cut a little bit off the FP shaft to get the motor to fit snug without spacers... so the 36mm gearboxes probably have enough shaft length to add a few small spacers. We did find, however, that ordering some extra gears to press on to the FP made life easier as we cracked them pulling them off the banebots motor.

As for overheating... well, we did smoke one FP in Portland after running it for about 10 minutes straight, but after adding a heat sink to the motor for Toronto we never had any problems with it there. We NEVER had a problem with the gearbox... mind you, it is quite possible that quality may vary. Having a spare gearbox (with a spare FP mounted on it!) on hand at the competition is cheap insurance, especially for critical functions.

Also keep in mind that FP's are thoroughbreds, not draught horses... they need to run, and run fast.

Jason

[jgannon]

Originally Posted by Joe Johnson

Note: it takes about 15 minutes from start to finish to take a FP motor and get it running in either the 42mm or the 36mm gearbox from Banebots.

Dr. Joe, could you briefly go over what the 15 minutes entails work-wise and tool-wise? We like to fly by the seat of our pants with respect to tools ("Chain breaker? What's that?" was a phrase I was not thrilled to hear three weeks into build last year), so if we end up ordering one of these gearboxes after kickoff, I want to make sure we have what we need to make it work.