Banebot Transmission Issues

[Karthik]

Teams,

Just a warning to all, we recently purchased a 256:1 42mm Banebot transmission, and have had many difficulties. It turns out that the quality of these transmissions leaves much to be desired. The output shaft is attached to the last stage of planet gears via a plate with two flats cut in it. The thickness of this steel plate is insufficient and to worsen matters the steel is rather soft. We managed to round the hole in the plate after a mere two minutes of use. If teams wish to use these gearboxes, I strongly recommend modifying the internals to better transfer the torque via the shaft. In fact, The Team 1114 design team and I, strongly discourage teams from using these 42 mm gearboxes in any reduction above the 36:1.

As always, your mileage may vary. Good luck.

[Joel J]

Really didn't want to hear that . But I guess its good to know now, rather than later.

[Kevin Sevcik]

I'll second Joel J. Any recommendations for a fix for the trannies?

[Karthik]

Originally Posted by Kevin Sevcik

I'll second Joel J. Any recommendations for a fix for the trannies?

We welded the output shaft to the aforementioned plate. It's holding up for the time being, no idea what the longevity of this solution is.

[Kevin Sevcik]

We're using ours in a pretty low-cycle application. We'll go with that and get some spares for backups now. Thanks again for the info before we trashed ours too.

[jgannon]

Karthik, any idea if this issue exists in the 36mm box too?

[Gamer930]

Be careful with the 56mm 12:1 gearboxes also. . . [edit]These are the ones made to run with the CIMs[/edit]

On one gearbox the CIM Motor Shaft was bottom out in the gear box and we had to fabricate a .015 shim because it was running very rough and grinding. . . Seems decent now. . .

Now Thursday night we had problems with our other gearbox. . . We were running it and all the sudden it locked up. . . We took it all apart and there were bits of metal shavings mixed with the grease. . On the output shaft there is a gear that is loosely press fit and we found that when they fabricated the gear there must have been a small burr on the gear and when they press it onto the shaft it made a good indentation and created a circular groove on the shaft that it finally froze up. We washed up all the gears. Took some fine paper to the gear and shaft and regreased it. . . Seems to run fine now. . .

Just a word of caution. . . Highly recommend to take them apart immediately if you hear something not right and after you use it for a while.

[Karthik]

Originally Posted by jgannon

Karthik, any idea if this issue exists in the 36mm box too?

Yup, we just pulled apart a 36mm and noticed the same issue. Soft, thin plate, hard shaft going through it. It may not be as much of an issue with the less powerful Banebots motor, but it looks iffy.

Another issue with these gearboxes is that they use an unknown type of screw to hold the face plate on. We had to grind down slot screwdriver to make it fit. Frankly these transmissions seem like more trouble than they're worth. Definitely not as robust as we had hoped.

[cdfps]

We put both banebot transmissions on a little test platform robot (20lbs?) that we were using for coding while the robot was being built.

We were getting some strange behavior with one of the transmissions where it would periodically develop a tight spot. We ran in the transmission with an old CIM for about 10min with a battery and no load. No difference. We disassembled it and flushed it. There were little silver metal chips in the flushing.

We then ran it in backwards with a dewalt drill on the output shaft for a few minutes with no load and mineral spirits for a lubricant. After this, we flushed it again and blew it out lubed and reassembled it. It ran fine after this.

If you do decide to flush it, remember that the solvent will get into the output shaft bearings.

[Madison]

Karthik,

Can you say how much load, if any, the gearbox was under when you rounded the flats?

We recently ordered two of these for infrequent, momentary use and I'm worried that we'll tax them too much and find ourselves in a bad situation.

Thanks for the warning.

[Viper37]

Today myself, 3 students, and two Mechanical Engineer's spent 6 hours reworking the internals of the Banebot tranny's. We had to grind, file, hack, and rub these things to finally get the inner pins and screws from rubbing other parts of the transmission internals. We also had to re-tap some of the screw holes as some came stripped out FROM THE FACTORY.

An off the shelf part is supposed to go together without any trouble, and work. The Banebots transmissions are the farthest thing from that.

And for what we paid for them, it is totally unacceptable.

In my own opinion, they are a large step backwards from what we have been using the last few years.

[Karthik]

Originally Posted by M. Krass

Karthik,

Can you say how much load, if any, the gearbox was under when you rounded the flats?

We recently ordered two of these for infrequent, momentary use and I'm worried that we'll tax them too much and find ourselves in a bad situation.

Thanks for the warning.

Madison,

We were moving a load of about 5 foot-pounds of torque, while shockloading by changing directions. So, I would call this a small to moderate load.

Also, our solution of welding the shaft to the plate has failed twice, we've re-welded it a third time. Since each piece is a different type of steel, it's just not working well. Also, you have to weld with the bearings in place and you're restricted to welding from one side.

In synopsis, these gearboxes are less than suitable. That's Karthik putting it mildly.

[sanddrag]

We assembled one of our Dual CIM kits today. As stated in the instructions, the key will need to be filed down to fit further back in the key slot for everything to fit together right. We put a wheel on the shaft and backdrove it. It feels nice. The motors haven't been run yet. Will update once we do. As a note, the dual motor kit adds only about 1/16" to the overall length of the gearbox assembly.

[Jack Jones]

Originally Posted by Karthik

Madison,

We were moving a load of about 5 foot-pounds of torque, while shockloading by changing directions. So, I would call this a small to moderate load.

In synopsis, these gearboxes are less than suitable. That's Karthik putting it mildly.

I'd say that's a small load. It's the equivalent of a 1 lb load on a 36" 1 lb arm - held horizontal. Who wouldn't dream of a achieving a 1 lb arm; and who wouldn't want to reach more than three feet?

Mid way thru the build is no time to be finding this out. If we bench tested every component, we'd still be three weeks into the build, with nothing designed.

We go into this knowing it's about teaching engineering problem solving; but it should not be about solving the supplier's engineering problems. I want to know if they plan on paying for our services!

Happy low scoring everyone!

[MrForbes]

The quick reversing of direction can be avoided with careful programming and control setup, and I have a feeling that this is much more likely the cause of the problem than the 5 ft lbs of torque.

It sure is nice to have this early failure report, so we know to be careful with the BB gearmotors, and have contingency plans in mind using either the Globe or window motors.