Best source for gears? Smallparts? drivetrain advice wanted!

We need to build custom gearboxes . . and I am put in charge of getting a basic sketch down. I have one using smallparts carbon-steel gears and sprockets, the Atwood/Chiaphuas, and the Bosch drillmotors and transmissions.

the thing is, using the sprokets and gears from small parts, my ratios are off by about .02:1 . .

like, I want one to be 1.3:1, best I can get is 1.28:1

Is this a problem, will my motors burn up if they are out of ration by 1 or 2 percent (ratios for both motors are a bit low, so maybe just <1%)?

Also, whats a reasonable speed/force? My current design gives us 10 m/s and about 350-400 Newtons (200-250 up the ramp)

I have no idea about efficiency either, so I just random-guessed 60%. This is high or low?

Im using Bosch to transmission to one gear-gear connection, then to the sprockets to drive the wheels, and Chip/Atw. to gear-gear connection to sprocket to wheels. Can I hope for higher efficiency? All parts are from smallparts with a total materials tab of ~$215.00, not including the chain or housing materials or axels, just gears and sprockets.

#%#%#%#%, we are really jumping into this. I have never designed a drivetrain in my life . . and our moderator says “Ok, so why don’t you sketch out a drivetrain and chassis for us and bring it in thursday or friday. Ok, greeaaat. And Bob, could you sketch out the bulldozer arms?”

I always get the hard part.

If you look in your MSC catalog, there should be a whole list of gears in all shapes and sizes. You might be able to find an appropriate gear in there.

Try Sterling Instruments NY

We use Stock Drive Products ( They have a pretty large selection. It’s extremely beneficial for us because they’re located on Long Island, and we can call in an order and pick it up the same day or the next day.

To answer Frank’s original question:

Being a few percent off on your gear ration should not be a big deal and if properly designed and built your gear efficiences should be on the order of 95-97% per stage.

Try the “Mechanisms and Components” section of the Metalworking Web Sites Index. Lots of good stuff in there.


Usually, I buy gears from PIC or Stock Drive, but I’m tired of waiting 2-3 or even 6-8 weeks for gears. The perfect gears for our gearbox this year were quoted at a 6-8 week lead time from Stock Drive…


The system was redesigned for MSC gears only and they will be delivered in 3 days. wooohooo!

Yay for MSC! The FIRST discount we got on this purchase was about 8%… not bad.

Andy B.

For gears you could look in MSC, but if you want custom gears, first try and see if you can make them in a machine shop. If not, try Boston Gear. Carbon gears do cost a lot of money too if thats what you wanna buy.

10 meters per second?:eek: :ahh: 10 feet per second would be much more realistic. I’d say most bot’s move somewhere around 5 fps so 10fps would be in the middle of the “really fast group”

*Originally posted by 157#1Driver *
**For gears you could look in MSC, but if you want custom gears, first try and see if you can make them in a machine shop. If not, try Boston Gear. Carbon gears do cost a lot of money too if thats what you wanna buy. **


Theres always a Catch… ($$$$$$$$$$$$)
check Thread “Sources”

About sources for gears:

There are a lot of online places you where can buy gears/sprockets… Here are some suggestions from different people:
“A few good small components sources:” - Keithicus and stock drive products ( are good sources. Also, motion industries is a good source.” -Joe J.
You can search across the industry for the part you want. It is particularly useful for gears and sprockets.” -ChrisH

“We found a company called Motion Industries that carried the identical part. Turns out they have about 500 outlets around the country (check their locator at ).” -dlavery

I just ordered some precision gears from a place called Rino Mechanical Components. The precision gears that usually take 3 weeks or 6-8 weeks from Berg or SDP can be delivered in less than a week from these guys (at least that is what they told me today).

Also, they are reasonably priced.

The only catch is that their minimum order quantity is 10… but they seemed flexible, letting me slide with ordering 8 of one gear.

Rino Mechanical

I warned the salesmen that I would be recommending them as a good supplier… so if you use them, hopefully they will treat you the same.

Looking at their catolog, these guys also sell other mechanical components (couplings, gearboxes, etc.).


Andy B.