Low Cost Planetary Gearbox Source...
 

While looking for some gearboxes for Robotic Amusements on ebay, I came accross the company BaneBots.



As it turns out, they make some pretty nice transmissions. AND they make some that are that the Fisher-Price and the Mabuchi motors will (pretty much) just bolt to (buy a gear or pull of the one that is on the stock motor, press the pinion on the FIRST legal motor, reassemble the gearbox, and mount it on your robot).

They come in a variety of ratios (5:1, 16:1, 20:1, 25:1, 64:1, 100:1, 256:1). The gearboxes have nice mounting points and beautiful 3/8" Dia output shaft that is long, easy to access (and support) and keyed w/.125 key.




I have 2 of these jewels on my desk right next to me.

Here is my thoughts.

They are sweet! But you are going to have to take the good with the bad.

The good:

• Reasonable Price (~$40)
• Nice mount points
• Nice output shaft (but it should be supported by an added bearing if you sideload it much)
• Compact
• Light
• Easy to use for the Fisher Price or Mabuchi Motors

The bad:

• Not exactly quiet
• I am skeptical that the transmissions can take the kind of torque we may be able to generate if you use a F-P motor and a high gear ratio (256:1 for example) if you stall the motors. I calc. that you could get over 50N-m out of the shaft if you really do use the 256:1 and a F-P motor -- that is alot of torque for a 3/8 shaft. I also have concerns about the face width of the last stage of the gearbox if you actually get to these higher torque outputs -- both the Globe gearboxes and the Dewalt transmissions have much beefier final gearstages than these gearboxes (this is just for comparison, not necessarily a criticism).

The Bottom Line:

• For the right application these gearboxes are AWESOME!
• I don't recommend trying to get 50N-m of torque output.
• I don't recommend using them as drive motors on a FIRST size robot.

FYI, I just talked to them the day before kickoff, they have 1000's in stock.

Good Luck,

Joe J.

Disclaimers:

• I have no ties (financial or otherwise) to Banebots, Inc.
• I have not field tested these on robots. All I can say is that my 11 years of FIRST experience leads me to believe that these gearboxes will be great in the right application on a FIRST robot.
• If you try this and it doesn't work out, I want to hear about it, but I don't want to hear things like "Dr. Joe, you are the reason we lost the Championship." As always, you mileage may vary.

Re: Low Cost Planetary Gearbox Source...
 

Larry Barello asked this question Here

The Fisher Price motors are "550" motor cans. This has become a sort of standard for Mabuchi/Johnson Wantabees to copy. Anyway, as it turns out the "545" can sizes are almost identical only slightly shorter (and less torquey typically). So any of the Banebot transmissions that use the 545 motor can use a 550 series motor. By the way, the Mabuchi motor is "RS-545SH-2485" it IS a 545 series motor already.

To answer your question, Larry, this is the exact motor/gearbox you want.

You also have to buy this pinion or pull the one of the motor that the gearbox comes with.

Good Luck,

Joe J.

Re: Low Cost Planetary Gearbox Source...
 

I talked to Rick Marriot from Bane Bots today and he said the If you order on the internet he can usually ship in about 2 days based on stock avaliabilty.

These are nice gearboxes. (no plastic gears).

Has anyone figured out if the speed controllers are also legal FIRST parts?

Re: Low Cost Planetary Gearbox Source...
 

I can't see how they can be based on my understanding of the rules.

Joe J.

Re: Low Cost Planetary Gearbox Source...
 

I ordered a couple of the 5:1 units to test on my lab dynamometer. Joe, you are not kidding these things are loud! The published 12 Volt 'specs' are as follows:

Free speed = 3120 RPM, Free current = 0.9 Ampere, Stall torque = 192 oz-in, Stall current = 37 Ampere

There is a disclaimer saying these are calculated values and they do not factor in loss from the gearbox.

Using my lab equipment (ISO calibrated stuff: Magtrol HD-715 brake and Sorenson DCS 20-150 power supply) I measured:

Unloaded speed = 3093 RPM, Unloaded current = 2.4 Ampere (note that my dyno drag at this speed is about 1.2 oz-in, due to friction, coupling flex, and un-energized brake drag)

When I increased the load to draw 5.0 Ampere, the speed was 2780 RPM and the indicated torque was 16.7 oz-in

When I further increased the load to draw 10.0 Ampere, the speed was 2070 RPM and the indicated torque was 39.3 oz-in

When I further increased the load to draw 15.0 Ampere, the speed was 1350 RPM and the indicated torque was 60.7 oz-in

When I further increased the load to draw 20.0 Ampere, the speed dropped below 500 RPM and the brushgear started to smoke, so I quickly de-energized the brake to minimize damage.

All the while the little gearbox was rattling and whining, I'd estimate about 100 dB at 1 meter. I would not recommend this unit for extended continuous duty! It's acoustic signature is annoying and losses in the gearbox are clearly significant. However as you point out it may be quite useful for mechanisms with intermittent duty and low endurance requirements. And the price is certainly right.

So my conclusion is that the gearboxes are at best about 80% efficient, and this drops to about 60% at heavy loads. I would not want to take them to more than about 10 Amperes motor draw for longer than a minute or so.

Re: Low Cost Planetary Gearbox Source...
 

Wow, lots of good data, thanks.

As to the conclusions, I am not sure I entirely concur. In particular, much of what you recommend involves the particular motor the gearbox comes shipped with (which is not a legal FIRST motor).

Even so, plotting the data, they don't seem pretty non-linear to me. Any non-linearity seems easily explained by the motor heating up as you increased the load.

The FP motors are prone to heat build up. It is extremely easy to pound more heat into that little package than can be safely passed off to the surrounding air. The same can be said for the motor that the Banebots transmission ships with.

This is well documented elsewhere in other threads, but think about this: A curling iron is typically a 20Watt device. Think of how hot a curling iron gets and it is only dissipating 20W. At 15Amps & 12V, the test above was inputting 180W of electrical power (V*I) to the motor. Of that, only 60W as being converted to Mechanical Power (T*w), leaving 120W to heat up the curling iron, I mean, Motor.

Back to my comments on the data, I think that the data on effeciency is somewhat affected by the heating of the motor. If I assume that the motor data is correct (even when the motor was hot), I get 72%, 80%, 61% and 56% at Freespeed, 5Amp, 10Amp, & 15Amp data points.

I am not sure how to intrepret this data. My experience say that 5:1 planetary gearboxes should be about 80-90% eff. per stage (we have only 1 stage in this case). One way of looking at it is to say that the first data point is off due to drag, etc, and that the last two reflect that the motor was getting hot. But, I could be trying to fit the data to my view of the world, so I don't know what to say.

Based on the data, I would perhaps estimate the gearboxes to be say 70% per stage and (using given that relatively low effeciency) I would try to keep the 12V load point of the FP to below 1/4 of the 12V stall (i.e. keep the motor spinning above 75% of its free speed). My experience with the FP is that if you do this, they'll be able to survive a FIRST season.

My final comment is that the data generally support that these gearboxes are not jewelry. They are cheap and dirty. But... ...I would just say that the price and effort are right... ...for the right application.

Joe J.

Re: Low Cost Planetary Gearbox Source...
 

As Joe correctly points out the conclusions I offered above are based on the motor that came mounted on the gearbox; i.e., on the assumption that the standard motor performs as advertised. My non-linear torque vs. speed results strongly suggest that the motor heated up during testing (as does the smoke observed when load was increased to 20 Ampere). So the gearbox may in fact be more efficient than I concluded, if the motor was operating less efficiently because it was running hot.

In any case, I still would not recommend this gearbox for continuous running above 10 Ampere load. And I still think the noise it makes is annoying.

My team plans to try launching balls using two of these gearboxes, fitted with kit FP motors and 6" wheels. For that kind of loading I would expect them to last through a FIRST season.

Re: Low Cost Planetary Gearbox Source...
 

Thanks for the find, these are very attractive.

As an aside, has anyone opened one of these things up? How are they lubricated? Any opinion of the quality of construction and possible durability issues?

Perhaps a little bit more or better lube could help with the noise?

-Andy A.

Re: Low Cost Planetary Gearbox Source...
 

I have opened them up. They are not great. The basic problem is that in general for a planetary gearbox to work right, the "AGMA Number" of the gears has to increase over a standard spur gear application. I did not actually have these gears checked, but my experience tells me that the gears are an AGMA number lower than typical if anything (if I had to guess, I would say the planets look like extruded pinion wire processed on a screw machine -- not ideal).

The only way go to get lousy gears to even RUN in a planetary gearbox is to increase the backlash -- ALOT!
Add to this that there are only 3 planets per stage and that (with the exception of the final stage) the centerline of the carrier (and that means the sun) is determined by the planets... what do you get??? ...well.. ...This:



Joe J.

Re: Low Cost Planetary Gearbox Source...
 

This is my redacted reply:

This is not true. The FP motors CAN take continuous use. They CANNOT operate near 12V stall or even at 70% of 12V stall (a.k.a. below 30% of their 12V free speed when applying 12V to the motor) for long periods of time without turning into a stinky, smokey blob of copper.

You do not give enough information to know if the conditions you are talking about are reasonable.

At 12V, the FP motor puts out .4 N-m at stall. With 2 stages of 4:1 each @ 70% eff. you will get Tgearbox stall = .4 X 4 X 4 X .7 X.7 = 3.1N-m.

I recommend that you operate at about 1/4 of this number to run continuous and happy all season long (not that you can't muscle through more than that for a short time - a few seconds say - but that you should not need more than this for 10s of seconds at a time).

Can you keep the continous torque on each motor to below .75N-m?

Let's assume that you have 4" pulleys on your <secrect mechanism> This works out to a radius of about 50mm = .05m. That means that you could get 15N (3.4lbs) on the <secrect mechanism> continuously.

Is that enough? It is hard to know without my getting into the nickers of your <secrect mechanism> design.

By the way, the <secrect mechanism> would be FLYING at almost 4 m/s (12ft/sec)* when driven by a 4" pulley with a tangential load of 15N.

If you don't need a <secrect mechanism> that is so fast, use a smaller pulley or a higher gear ratio gearbox.

Joe J.

*I made a mistake in my calc. my initial posting mistakenly claimed 25m/s which was just whacked. Sorry. Even so, 4m/s is not exactly turtle speed.

Here is my calculation for review and perhaps further corrections:

16000 RPM @75% (i.e. 1/4 stall torque) = 12,000 RPM (@ motor)

12,000 RPM (@ motor) / 16:1 = 750 RPM (@ Gearbox)

750RPM = 79 Radian / Sec = w

V=w X R
79 Radians / Sec X .05 m = 4 m / s

Re: Low Cost Planetary Gearbox Source...
 

I never intended to discourage anyone from using the FP motor. As Joe J. points out above, there should be no problem with running it continuously at loads that are less than ~25% of its 12V stall current. When using the single-stage 5:1 BaneBots gearbox with an FP motor, I would not be too worried about running continuously at up to 15 Ampere, because the FP has about 50% higher stall current and is therefore a more capable motor than the one that comes with the gearbox. The gearbox itself will probably wear out faster at FP continuous loading than it would with the standard motor, but that is probably not an issue for a mechanism that will be used for one FRC season.

My recommendation above was just to avoid continuously loading the BaneBots gearmotor at currents greater than about 10 Ampere (about 25% of its 12V stall current). I really don't like to see smoke coming from motors, and this one started smoking at 20 Ampere.

Re: Low Cost Planetary Gearbox Source...
 

I am just having fun with ya'll and while I am at it, trying to give examples of the way you can calculate reasonable numbers for motor loading.

Joe J.

Re: Low Cost Planetary Gearbox Source...
 

How do these transmissions compare with the DeWalt XRPs: efficiency, value, reliability, power transmission, etc?

Tnx ... jon

Re: Low Cost Planetary Gearbox Source...
 

They are nowhere near the quality, reliability, etc. of the XRP transmissions, but the NBD modifications are nowhere near as easy to implement as the changes needed to use these transmissions.

They are quick and easy. They are smaller and cheaper than the XRP transmissions.

That is their main advantage.

As to the right value, it depends on the application. For the right application, I think they provide a fantastic value proposition. For tougher applications (for example an application that involves impact loads or high torque), I would use modified Dewalts.

Joe J.

Re: Low Cost Planetary Gearbox Source...
 

Any recommendations on which modified dewalts and where can they be purchased?

Re: Low Cost Planetary Gearbox Source...
 

You can read the whitepaper here:
Nothing But Dewalts

And read the discussion here:
Nothing But Dewalts

It's among the most well written whitepapers on CD. Where you can purchase the components are well documented.

Matt

Re: Low Cost Planetary Gearbox Source...
 

We want to try out the Banebot gearbox. What advice can you all give for mounting the new pinion on the Fisher Price motor shaft? Is it simply a matter of pressing the new pinion on the shaft? I'm thinking there must be more to it than that. And what tools would you recommend for the job?

-Chip Tucker

Re: Low Cost Planetary Gearbox Source...
 

Chip,
Having done this just this weekend I can tell you what I did.

You will need to pull or otherwise get the pinion off the FP motor, I had to grind ours down a bit to fit into the puller that we got from bane bots. DO NOT GRAB IT WITH PLIERS AND TRY TO PULL IT OFF, YOU WILL DESTROY THE MOTOR because the force you are putting on it will be transfered to the bushings, etc. in the motor.

After you have the pinion off the FP motor take apart the Planetary 4 screws in the face, and 2 on the motor, careful the entire thing will fall apart.

Now would be a good time to wrap the FP motor with masking tape, this is to keep the metal bits and shavings out of the motor, and yes they will get in there no matter what you try so go ahead and wrap the whole motor, leaving only the shaft accessible.

Carefully measure the length of the shaft on the motor that came with the planetary and carefully mark the FP motor shaft the same length and with a dremel (I tried a band saw, didn't work too well, very dangerous, don't do it) and cutoff disk carefully and very accurately cut the shaft of the FP motor to length being very careful not to heat the shaft up too much as you do. I didn't have a problem with the shaft spinning, but if you have this problem you could hold the back side of the shaft with pliers THROUGH the masking tape. After cutting measure the shaft again, as you don't want to have to pull the pinion off to shorten the shaft more later.

Blow or vacuum the residue off the motor.

Take a file and bevel the edges of the cut edge on the shaft and make sure there are no burrs sticking up from the end, It should be a clean cut. DO NOT FILE OFF THE SPLINES ON THE SHAFT only bevel the end and dress the cut.

Clean the motor off, leaving the masking tape on blow or vacuum the shavings off the motor can and wipe down with a clean paper towel, etc to make sure they are gone.

Take your new pinion(only about 1$ when you order the transmissions) and place your motor in an arbor press (a GOOD vice MAY work if it had smooth jaws and very little slop) making sure that the only contact point on the back of the motor was the shaft, not the plastic or the electrical contacts. Keeping the motor and pinion very straight press the pinion onto the shaft, if it looks crooked stop and look very closely, if the assembly cocks in the press then you could bend the shaft and destroy your motor. I had to stop 3/4 through the pressing and remove shavings from the pinion end to allow further pressing. The pinion should be flush with the end of the motor shaft.

Clean the motor off for the last time and carefully peel the masking tape off (our team leaves the tape over the cooling holes in the motor until just before ship just in case) and reassemble the transmission cleaning the screws off(or replacing with socket head cap screws) and lock tite-ing them. If the end blocks don't seem to be seating onto the round center section or the transmission doesn't turn, or is harder to turn than with the other motor your motor shaft may be too long and need to be shortened. If that happens don't forget the tape!

Hope this helps, and if anyone has a better way feel free to chime in

Re: Low Cost Planetary Gearbox Source...
 

Ditto for Justin's post, plus a warning: I'd say the outfit in China which makes these puppies has the same material quality control we've all come to expect for inexpensive hardware coming from that part of the world. Even taking great care, I managed to strip the threads when tightening two of the screws holding the gearboxes together. If we use it, we'll be putting heli-coils in.

Re: Low Cost Planetary Gearbox Source...
 

I was unhappy with the use of phillips head screws rather than torx or socket cap screws. I don't have the screws in hand right now. Does anyone know the thread definition? Based on my memory, I think it was an M4 or perhaps it is a 10-32 (based on the fact that the rest of the metal mounting points are that thread).

If you know, please share.

I think if I were using these gearboxes, I would replace the phillips head screws with a hex socket head cap screw (though I don't know if I would go so far as to install helicoils on any threads as a preemptive measure).

Joe J.

Re: Low Cost Planetary Gearbox Source...
 

i would say for us so far the hardest thing about these trannies is getting the gear off the FP motor. I ended up chucking it up in the mil and milled the gear of. As for pressing the new pinion to the shaft we haven't done it yet. But the plan of attack is to make a spacer from the motors that come with the transmissions that fits between the pinion and the motor casing, then use that same spacer on the FP motor. We are planning to heat up the new pinion and thermally bond it onto the shaft so there is less of a chance of bending the shaft on the FP while applying it. I will write up an after thoughts post after we are done.

Re: Low Cost Planetary Gearbox Source...
 

Am I the only one that that the pinnion gear split when I pushed it onto the FP shaft?

We tried to use one of these on a mechanism and after I pulled the gear off the FP (using a bearing seperator and drive pin punch on an arbor press) I went to install it on the FP motor. I did not do anything to the splines but instead tried to press the gear straight on and heard the dreadful pop of the pinnion.
Pete

Re: Low Cost Planetary Gearbox Source...
 

I turned the splines down to about 0.126 because of the high interference - I was kindof afraid of the brass pinion doing something like that. The splines bring the OD out to about 0.130, while BaneBots says the pinion is for a 0.125 shaft OD.

Re: Low Cost Planetary Gearbox Source...
 

What methods has anyone used for turning down the motor shaft?

_Alex

Re: Low Cost Planetary Gearbox Source...
 

Ours broke, too.... didn't even notice until we powered it up... it lasted about 3 seconds. Great little gearboxes, though... we'll buy some more pinions, though.

Jason

Re: Low Cost Planetary Gearbox Source...
 

I am continually impressed with the Folks at Banebots, Inc.

I have been bringing up concerns and problems and they have been very pro-active in their response.

This is a copy of the latest letter from Ed Yackey concerning the screw threads stripping out:
I think that this is a very reasonable response.

Please continue to keep us posted with your experiences with these gearboxes and this company.

Questiong to the CO teams & FIRST folk: Banebots, Inc is in Fort Collins, how come you guys have not been beating on their doors and getting them involved? We have to find a way to get them to the Denver Regional.

Joe J.

Re: Low Cost Planetary Gearbox Source...
 

That is a very generous offer. Just for general note, we bought the 20:1 gearboxes and i replaced the screws with M3- 30 cap screws. I did have to turn the heads on them down a bit to get them to fit into the clearance holes but after that the snugged right up no problems. I Would recommend that if you haven't taken them apart yet make sure you do it with a proper sized Phillips screw driver, this will help prevent stripping until you can change the screws.


Some other assembly notes i have found through experience:

The spacing that you want from the pinion to the motor body is about 1/16 of an inch, making a spacer plate really helps with the assembly.

you can head the pinion to make it side on but after trying that pressing it is much easier.

when you press it on only support the motor on the shaft, bend the electrical leads out and hold it between the 2 ends of the shaft, this minimizes the chance of bending the shaft. I used a socket for a spacer.

If you have old FP motors lying around make sure they are no where near you when you are working. (good thing i bought extra pinion gears.)

If anyone needs help or advice please feel free to contact me. So far i am very impressed with these little gearboxes and i have a feeling i will be using them for years to come.


Greg

Re: Low Cost Planetary Gearbox Source...
 

Latest update from Ed at Banebots concerning stock of pinions and pullers. FYI.

Also, teams with experience with these gearbox: Please share the the Good, the Bad and the Ugly with us. We are all learning.

Joe J.

Re: Low Cost Planetary Gearbox Source...
 

The screws holding the gearboxes together were very tight on one of our boxes. Tight enough that when the kids used a slightly ill-sized phillips driver, they stripped the heads pretty quickly and we had to drill them out. For those that are curious, they are 3M metric screws, and I believe about 28mm long on the 1:16 and 1:25 gearboxes.

Re: Low Cost Planetary Gearbox Source...
 

Just got our Banebot transmissions and noticed that the air duct of the motor near the output shaft is blocked by the Banebot transmission. The FP plastic transmission has some holes to i assume let cooling air flow. The question is at what loads and duration at room temperature is this detrimental?

Re: Low Cost Planetary Gearbox Source...
 

About the pinions splitting. I think it's only a problem with the 5:1 pinion since it's so small. I split the first one pressing it on the shaft and didn't even notice till the tranny wouldn't work under load. My solution was to grab a new pinion and a .1247 reamer I had from the NBD mod we did last year. I ran it through with a hand drill and it pressed on fine after that. If you can actually chuck up the pinion in a lathe, I'd use a .1250 reamer, as that's what I ended up using on the FP last year when I could chuck the dewalt pinion.

Second comment. Has anyone else gotten one of the trannies with a crooked keyseat on the shaft? We've got one that takes a distinct jog to the side halfway down the keyseat.

Re: Low Cost Planetary Gearbox Source...
 

No data that I am aware of for exactly the effect this will have on the lifespan of the motor. Obviously, it will limit airflow, as a good deal of air does flow out of those front vents.

My suggestion may come to late, but if you can permit some standoff between the front of the motor can and the transmission, obviously airflow would be better. By using longer screws and some very small spacers it would be easy enough to move the motor back. This would require that the pinion be hung out at the end of an unmodified motor output shaft, and you'd probably want to support the end of the motor can to keep strain off of the very small and very weakly threaded attachment screws.

As for 885, we are just hopping that the motor will make it through. In the end, the way FP motors die pretty much negates air flowing through the front vents. If a FP motor dies, its because it stalls and there is no fan moving air period, and all the venting and heat sinks in the world won't help you. A slow, gradual death from heat build up is probably a lot more rare.

Give the motors time to cool between matches, and invest in some canned coolant.

-Andy A.

Re: Low Cost Planetary Gearbox Source...
 

On behalf of Team 1519, I'd like to thank Joe, Richard, and all of the other contributors to this thread.

Our team ended up using three BaneBots gearboxes on our 2006 Robot. Without these gearboxes, we wouldn't have been able to come up with a workable design for our shooter turret. We used a 5:1 BaneBots gearbox on each of two FisherPrice motors in order to drive the shooter wheels. We also used a 25:1 BaneBots gearbox on the Mabuchi motor in order to drive our shooter's "feed roller." The use of these gearboxes enabled us to come up with a relatively small, lightweight turret which was able to track the light effectively.

Our experience with the BaneBots gearboxes was very positive. Our only major problem was that we needed to machine the pinion gears that came with the gearboxes in order to increase the ID sufficiently to get the gears onto the shafts of the Fisher Price and Mabuchi motors. It took us quite a few broken pinion gears to get it right before we got one to work! However, once we learned that piece of knowledge, the BaneBots gearboxes served us very well.

Thanks to all who contributed to this thread -- without this awesome information sharing, we would have had a much more difficult time building a competitive robot in 2006.