If he removes the center idler, wont he be loosing power to the center wheel? If all the wheels are to be belt driven, the I would guess there would be a need for all the idlers.
I would not be surprised if I am missing something. 
Hi Rick, keep talking buddy… lol 
OK I’m coming clean. Here is all the data so far. I’ve been meaning to do this anyway…
The pulleys are all 32 tooth and can accept belts up to 0.289". I’m using a standard 0.250" wide MXL belt. The idlers are 0.125" ID, 0.375" OD and 0.156" wide, I’m using two of them per position. The tires are 2.125" diameter and 1.5" wide.
I completely expected comments about the timing belts. This is uncharted territory for many. If I were building for Japan rules, vacuum and or magnets, then it would be out of the question. But with just 3kg pushing down on the drive train the bot is likely to bounce before anything breaks. Off the forum I have received comments ranging from “Those timing belts will not be a problem at all” to “The thing will fly apart!”
Here’s the information on the cobalt motor.
Maxx Products PMX4812.
Diameter 1.14"
Length 2.13"
Weight 4.1 oz.
Shaft 1/8"
Winding 12/#22.5
Typical voltage 8.4-9.6vdc
Test voltage 8.0
Static RPM 15,600
Static amps 19.2
Static Power 154W
I believe static means not flying?.. These motors are for airplanes. The current demand is what made me want to try these before going to the 05 model.
The gear box is a planetary box with 27:1 reduction and dual planetary gears, just double the height of the current planet gears for more strength. Dual ball bearings on the final gear of course. 15,600 rpm with 27:1 is 577 rpm at the wheels. Which is 64.2IPS! We can slow it down from there if necessary.
I agree to some extent that 4WD has inherent advantages over 6WD, especially in my situation, but I really want 6WD…
I hope to have it moving under it’s own power in a few days. 8)
I think this will work. The only thing I can think that might go wrong is when the motor goes from 0 rpm to 15,000 rpm in an instant, there is a slight chance that the belt going around the drive pully could jump out of the groves from the stress, and go Zzzzzzip!
If the power is ramped up then I think it will be ok. I say try it full on power and see what happens first. Just a thought I wanted to throw out on the table.
EDIT
Second thought, if both motors work together then there might not be as much stress since all six wheels and two motors are working together.
Jim,
I’m still working on the bounce problem. After five years I still don’t have a good solution. The bounce will put shock loads on the timing belts.
Static in this case means with a 6X4 prop and not moving. In an airplane this would be a worse case scenario, i.e. maximum current draw and heat build up. In a robot that has its maximum load at 0 rpm, the current draw will be much, much higher. I’d double or triple the current to 40 - 60 amps for the speed control design.
Your motors are 12 turn, 22.5 ga. The big brother 05s are 6 turn 19 ga. That will be a huge jump in current. I’d plan on 90 to 100 amps per side. That is why I stuck with the stock R/C car armatures with 27 turns.
The gear box is ideal for the application. Too bad you don’t have more of those PGHM-14s like I use. At under $30 they were a steal. No, you can’t buy mine back at any price. 64.2 IPS is good. Don’t even think of slowing it down. I just noticed that I haven’t measured Executioner’s speed in its present configuration. Early on, with 6 cells, it did 85 IPS. Now it has eight cells, so I guess it is over 100 IPS.
No problem with that. 6WD was always much more intimidation than 4WD. And, once your opponent knows that he is going to loose, the rest is easy.
Rick BrooksMike,
The suggestion was to remove the idlers and the center wheel.
Good call. Ramping in the speed control is absolutely necessary.
Rick BrooksHi Rick!
Well I have found the original source. I have been wanting to get them back on the website. 8)
Hmmm, I must have missed that little detail when I was spying, um I mean researching your robots. Huh, 85 IPS, really…
I’m not going to get too caught up in specific numbers. The goal will be to move as fast as what is controllable. If we can control it well at 65 IPS we can add more cells till it becomes less stable. Then slow down in software. The most headroom possible, the most performance possible. Weeeee!
That is great news. I have wondered what I would do if one of the gears broke. There is nothing else on the market that comes close.
Bot Brawl 2006 when Executioner spun off its rear tires and Bot Brawl 2007 when the speed control smoked the speed was 85 IPS. When I rebuilt the smoked control, I found much better N and P channel MOSFETs. They were so much better that I added two more batteries. It is scary fast and I am intimidated every time I plug it in. I must have forgotten to update my web site with that information.
That is the way to do it.
I spent last weekend in Marion, Ohio, at the National Robotics Challenge. There sure was a lot of your stuff there.
Rick BrooksHi Rick,
I have a small batch of the original gearboxes that were returned for one reason or another. So a replacement gear wouldn’t be a problem. Just need to ask.
The place making them was a startup business. They had some quality issues, so I left them to work out their issues. I have made contact with them again, actually lost the info for a while. I just need to do the foot work to get them going again. Guess I have to now… lol
Found a new place to get gearboxes. These are designed specially for the cobalt motors pictured earlier in this thread. This image is of the prototype. Waiting for them to get here. And it only took me 6 and a half months to get to it! 
Nice looking gearbox Jim, a note about using the belt drive set-up. Beld drive is a very strong set-up as long as it is configured correctly. Belts with kelvar is the way to go do to their tendencie to streatch less. There is a reason Harley went to the belt drives on the bikes, strong, and virtually maintenance free. The only downfall I would see in the application is the pullies not the belt. The pullies need to be of good enough quality so that it meshes with the belt smoothly without play in the mesh on the teeth of the belt. If there is play there you can tear teeth off in hard direction changes. Just a thought for you to look at in assembly of the drives.
Another thought too is to use a belt that is as wide as allowed in the pully, a belt that is the full width will wear less than one that has room to move side to side.
Yeah I know there are hurdles to overcome. I’m very likely to convert this to 4 wheels instead of 6. This will reduce the complexity and improve the efficiency of the entire drive system. Can’t wait to get the gear boxes here so I can finally get this guy moving! 8)
Jim,
That gearbox looks wonderful, obviously very high quality. Too bad I am not building a 3Kg sumo.
March is only four months away.
Rick BrooksHello Jim,
Great start to your bot!
I know all about chasing the guy in 1st place.
This was my first entry into 3kg Sumo & where Rick brooks embarassed it by beating it with Expendable.
thebabcocks.us/1st.htm
I made it my mission to get even. 
Here was my second attempt:
thebabcocks.us/2nd.htm But lost again due to a bad plow design.
3rd time was the charm with my tracked revision:
thebabcocks.us/3rd.htm Victory!!!
Here are more pics if anyone is interested: thebabcocks.us/sumo.htm
I used custom conveyor belts for the tracks. The only bad part was I didn’t do my research first and built it to the NEIRG Rules and it’s a 22cm 3kg robot so I can’t compete it anywhere else.
Nice bot! where’s the videos? 
I don’t think I have any… 
I just got it working again, bad batteries, so I upgraded and went upto 8 cells to increase the speed. I’ll have to take some new ones and maybe post them this weekend.
Wow you even posted his winning match. What a standup guy. Thanks Rick!
Thanks Rick!
It would only be fair to post this one then:
brooksbots.com/Movies/NEIRG%2005/9b%20Titan%20vs%20Sticky.wmv
Hi Brandon (aka Trackman),
I wondered what happened to you and Titan. Are you planning on a return to NEIRG in February?
It will me more interesting at the CIRC Bot Brawl with Jim’s new robot to go against Executioner and Cheeky-san. Perhaps Mike an I won’t have to drag out our old 3Kg sumo robots (Brutus and Excuse) to fill out the field.
Titan is a very interesting robot, it would be good to let the competitors in Peoria see it. Perhaps you could enter it in the “Best in Show” class there.
Rick BrooksHi Rick!
Titan got lost in a move & while in storage had one of the Nimh cells explode and leak all over. 
It’s all cleaned up now, new nimh cells, went from 6 to 8 cells to increase the speed a little. Titan is a little slow, but better now. Also changed some sensors and re-wrote all the programming to get rid of some bad code. I’ll be at NEIRG, and CIRC sounds like it would be cool to go to too.