Aluminum sprockets for drive train - several questions

[IndySam]

We have used them for three years without any trouble.

[Cory]

254/968 have been using aluminum drive sprockets the last two years. 7075 will not be eaten up by the roller chain. We have used ours both plain, anodized, and hard anodized, and have seen no noticeable wear on any of the three surface finishes.

[RyanS]

294 has used AndyMark aluminum sprockets with #35 chain for the past two years in our drivetrains. They have held up fine and show no signs of wear. We are probably going to try #25 chain with 7075 hubbed sprockets this year

[dtengineering]

We had some aluminum sprockets custom-cut from 1/8" plate using a waterjet cutter for the "aim high" game. We had a six wheel drive train (4x6" IFI traction wheels, 2x6" AM omnis) powered by four CIMs using the KOP transmission. We got into several pushing battles in Portland and at GTR, did a fair bit of ramp climbing, and basically slammed that poor little robot around pretty hard.

Although we broke lots of stuff on it and have put more "miles" on it as a demo robot than we have on any other machine, the sprockets are just fine.

Had we used steel we would have been in trouble... we weighed in for the eliminations at GTR weighing 120.0.

Jason

[MrForbes]

Just for perspective....the blower (supercharger) drive on my 55 chevy uses aluminum pulleys with a 1/2" pitch toothed belt, 3" wide. I've worn out two sets of plain pulleys, each lasted about 20k miles. The last time, I paid extra for anodized pulleys, they're still doing fine after about 15k miles, no noticeable wear.

How many miles do you put on your robot?

[AdamHeard]

I've worked on several drivetrains based on AndyMark's plate sprockets (both #25 and #35). So far have never had an issue with wear or failure. If you run the numbers, the size of the sprockets in a usual dead axle drive and the usual torques in such a drive show they are plenty fine; and if they aren't, just bump up to a larger sprocket until they are. I love them so much that all dead axle drives I work with are designed to specifically interface with the plate sprockets stock.

We've only had one issue, and that was a set of #25 with slightly misshaped teeth (Andy said because of feedrates). We mentioned it, and they were very promptly replaced.

[Triple B]

233 has used #25 chain on our drive wheels for 10 years with no wear problems. They were manufactured from 6061 aluminum with no anodizing. Our robot from 2003 still runs and has the original sprockets. Before we went to direct drive we used steel sprockets on the output shaft for strength of the shaft/sprocket interface.
mike d

[ChrisH]

Originally Posted by squirrel

How many miles do you put on your robot?

Thanks to some of the added capabilities of the new control system, we are planning to include an odometer in our code. That way we can track repairs etc. by distance traveled and figure out how many tires we will need this year.

Of course, figuring out just what the milage really is is complicated somewhat by our tendencey to spend much of the time driving backwards.

[MrForbes]

I guess you need to ignore the direction signal from the encoders when incrementing to the odometer?

Very neat idea! I wonder what other stuff might be useful to keep track of?

[M. Mellott]

Everyone,

Thank you all very much for your testimonials--it's very helpful to know so many quality teams have used them successfully.

[Elgin Clock]

Chain shouldn't tear up the gears, but if you have something other than a drive train (ie: something that will include a huge load on it - arm, or other such load) your gears could get their teeth torn up...

We made a gear box my first year in FIRST (2001) and by the end of the season, the welds we used to attach the gear to the shaft help up awesome... but left the teeth the weak point, & it resulted in a half-moon shape gear. (The application was just a gear on gear mesh without using any chain & we were lifting full size robots & the goal that year which was about 150 lbs as well, all while putting that gearbox to it's full potential, & obviously past it's limit.)

Would have worked great as a cam, but unfortunately that wasn't our intended application of course.

We have since learned quite a bit about drive trains, & gearboxes & don't have that problem any more. (knock on wood).

[Mr_I]

We've used AndyMark and IFI sprockets for years, with both 25 and 35 chain, and the only real slip we’ve encountered came when the robot took a hit, bent a frame and introduced slack. So the two important lessons are A) have a tensioner system (with lots of room for movement), and B) the tendency to slip is directly proportional to the number of degrees of wrap that the chain makes around the sprockets. Make lots of >150 degree turns and you should be fine.

[AdamHeard]

Originally Posted by Elgin Clock

Chain shouldn't tear up the gears, but if you have something other than a drive train (ie: something that will include a huge load on it - arm, or other such load) your gears could get their teeth torn up...

We made a gear box my first year in FIRST (2001) and by the end of the season, the welds we used to attach the gear to the shaft help up awesome... but left the teeth the weak point, & it resulted in a half-moon shape gear. (The application was just a gear on gear mesh without using any chain & we were lifting full size robots & the goal that year which was about 150 lbs as well, all while putting that gearbox to it's full potential, & obviously past it's limit.)

Would have worked great as a cam, but unfortunately that wasn't our intended application of course.

We have since learned quite a bit about drive trains, & gearboxes & don't have that problem any more. (knock on wood).

Are you referring to gears or sprockets? I can't really determine from what you're saying.

Somewhat related;

I have used 60T #35 Aluminum sprockets on extremely high powered and high reduction arms (As in the final stage of a 2500:1 reduction directly attached to about a 5' arm that was rather heavy [forgot specifics] and held the trackball at the end of that. It also hit the rack when extended at drive speed many times) with no signs of fatigue or tooth wear. I believe this is true of 330 as well.

[EricH]

Originally Posted by AdamHeard

I have used 60T #35 Aluminum sprockets on extremely high powered and high reduction arms (As in the final stage of a 2500:1 reduction directly attached to about a 5' arm that was rather heavy [forgot specifics] and held the trackball at the end of that. It also hit the rack when extended at drive speed many times) with no signs of fatigue or tooth wear. I believe this is true of 330 as well.

True. 330's are custom-made; I don't know the metal. See also 330 2005 and 2007.

We also used some mid-size ones in 2007 for deploying ramps. Those took everything we threw at them and still worked. They were on the outside rear of the robot, virtually unshielded, IIRC.

Aluminum sprockets are a good thing if you use them correctly, in any application. The trick is to use them correctly. (I know 330 has used them in drivetrains and arms for some time. Other things, like tires, have or worn, but not the sprockets.)