Minibot climb rate

[Tobot]

Here's an internal view of the Tetrix gearbox:



It looks possible to mate the brass helical gear to the 40T gear on the output shaft, with a little bit of machining. Sorry this post is a day late.

[Gary Dillard]

Originally Posted by Tobot

Here's an internal view of the Tetrix gearbox:



It looks possible to mate the brass helical gear to the 40T gear on the output shaft, with a little bit of machining. Sorry this post is a day late.

Thanks for the pic. How many teeth on the gear on the input shaft that mates to the 26 tooth gear?

[IKE]

Originally Posted by Gary Dillard

Thanks for the pic. How many teeth on the gear on the input shaft that mates to the 26 tooth gear?

Math would say 10. (40/10)*(25/15)*(30/10)*(26/10)=52:1

[Tobot]

Originally Posted by Gary Dillard

How many teeth on the gear on the input shaft that mates to the 26 tooth gear?

10 teeth on the helical gear on the motor shaft. This makes the ratio input 52:1 output for the gearbox and motor as assembled. Mating the 10 tooth element of the 26:10 brass gear to the 40 tooth output shaft gear would yield
input 10.4:1 output for the same assembly.

[Jared Russell]

Originally Posted by Tobot

Here's an internal view of the Tetrix gearbox:

(Picture Omitted)

It looks possible to mate the brass helical gear to the 40T gear on the output shaft, with a little bit of machining. Sorry this post is a day late.

That is exactly what we did (using only an inexpensive mill and lathe and a dremel), and it works great.

[Chris is me]

Originally Posted by Jared341

That is exactly what we did (using only an inexpensive mill and lathe and a dremel), and it works great.

Do the gains in efficiency offset the lower torque output of the motor, or is this an "experts only" mod for teams that make custom 2" wheels?

How dramatic is the speed gain? 1625-dramatic?

[Chris Hibner]

Originally Posted by Chris is me

Do the gains in efficiency offset the lower torque output of the motor, or is this an "experts only" mod for teams that make custom 2" wheels?

How dramatic is the speed gain? 1625-dramatic?

The dyno data showed a ~60% increase in output power. That makes it 1625 fast. You would definitely have to do some custom gearing and probably custom wheels (custom wheels will remove the necessity for some of the gear ratio). The big thing is to get the gear/wheel combo right so your reflected torque to the motor is ~50% of stall.

[Gary Dillard]

Here's a tip, whether or not you chose to modify the gearbox. We found in years past that cleaning the stock grease from our NBD gearboxes and using light lithium grease had a noticeable improvement in output (efficiency). It looks like this gearbox is pretty clean - don't know if it was that way when you opened it, but even if it was well lubed it might be a good idea to clean it out and put in lithium grease. (which per update 5 is an allowable material).

[Chris is me]

Hmm....

I imagine for a 1:1 (pre mod) reduction it's more efficient to leave the gearbox as is than to take out half the stages and compensate for the speed increase with Tetrix gears.

But for a 0.5:1 (pre mod) - that could be interesting.

[jnapp18]

http://www.youtube.com/watch?v=UqPyHQqQtYk

water bottles attached to simulate battery weight

[waialua359]

nice job.

[pfreivald]

Looks like a nice start!

[Tobot]

Originally Posted by Gary Dillard

...It looks like this gearbox is pretty clean - don't know if it was that way when you opened it...

The photo was taken seconds after opening the box for the first time. It was quite clean and lubrication was pretty light.

[Chris is me]

Considering the use of tiny helical gears I think adding more lubrication will help even unmodified gearmotors.

[thefro526]

Originally Posted by Tobot

The photo was taken seconds after opening the box for the first time. It was quite clean and lubrication was pretty light.

Originally Posted by Chris is me

Considering the use of tiny helical gears I think adding more lubrication will help even unmodified gearmotors.

I looked at one of the transmissions we had, and I didn't notice any lubrication. It may have been there, but I couldn't see it or really feel it.

Does anyone have a good grease for these guys? I'd imagine you'd want a pretty light grease.