Look at McMaster.com, catalog page 1012, starting at item 2737T13, and continuing down. I plan to use a 20 tooth myself, to make sure it fits within the radius of the plastic sprocket.
Thanks for your help!
Sorry to the OP for hijacking this thread
I found most of my mechanical parts at Robot MarketPlace. Sprockets, Chain and I think I bought 1/4 inch hubs from there also. Replaced so many parts in so many different tests its hard to remember.
After many tests the base is way to small for any sort of large scale mowing. Plus with the tracks it leaves a 3 inch uncut edge. The platform is great for running around the yard but the gps didn’t work as i planned.
The tracks them self have preformed great there is wear but nothing major even used on concrete or grass. Only trouble i had was was in gravel but that is a flaw in my tracks design.
For some reason i can’t see the pictures i posted on this post any clues why?
Great to hear, I’m looking forward to getting something built. How was the hill climbing ability of your setup on grass? Did you ever do any tests to see how much it could pull? Have you tested these tracks in snow/ice?
What was the problem with the gravel? Maybe I can avoid this problem
I’m not sure about the pics; do you have to have a certain number of posts before you can add pics? I know some forums are set up like that
Pictures can’t be posted to the board itself. One has to use links to the picture that resides on another web site.
I got the pictures working again. With the two cordless drill motors, the tank was able to climb anything i put in front of it, to the point were it would flip it self over if you were not careful. Pulling weight, It was able to pull my 65 lb nephew with no problems, and the tanks weight is about 24 lbs. So close to 100 lbs with only one cordless drill battery, the plan is to add another one to increase the run time… And 500 rpm is way to fast for a tank. I only use about 20% of the motor controller until large weight was added.
The problem i had in gravel is, if you look closely at the bottom of the tracks the aluminum doesn’t come completely to the ground and it lets rocks enter the tracks. Plus my sprockets come to the edge of the tracks unlike the johnny 5 tracks.
Sounds like a pretty sweet setup. I’m gearing my scooter motors down to about 250 rpm with the gears that I ordered from McMaster-Carr.
I had a feeling that’s what was going on with the gravel. Thanks for the info 
I have got new pictures of the robot. The Pictures are very large so i posted them on my website with the old ones. I didn’t know how to make a thumbnail of them on the forum. All the electronics are removed in some pictures because i changed the body some. If there is something you see there you have questions about I can post more detailed pictures now.
Becky Bot
Here is the rebuilt body, a waist rotation will go on top and I will add from there.
http://home.comcast.net/~ccook1289/thumb01.jpg
I still need to cover the body in aluminum to hide all the batteries. Electronics will go in the chest.
Got a new camera so it took some time to figure out how to make the file smaller.
hi ChazBCook , i read your post and show your project but weather a track on robo is still running . if yes its great and thanks to give information. i am trying to run track in my robo. thank again.