Quote:
Originally Posted by maclaren
I agree with replacing the rollers with idler sprockets it would be much more efficient. The noise is the chain lobes bumping over the rollers. Noise like that means inefficient.
I'm guessing from the picture that it's #35 chain?
What size wheels are you running they look about 4"?
What shifting method are you using. Two dog shifters, a ball shifter, or what?
What speeds (FPS) are you estimating from the different gear ratios?
I have to ask do you really need four gears? I mean you don't have a huge amount of traction so having a really torquey gear ratio could mean that you don't have enough traction to actually realize that troque and your wheels would just slip out. And how fast do you really need to go the field is only 50 something feet long so 12-15 FPS means so can get across the field pretty quick. Don't get me wrong a four speed transmission is really cool and I respect the engineering and the maching that goes into the effort.
I would also be interested in the total weight of the system and the weight of the transmissions assembly.
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I'm kind of concerned about some things you are saying....
I'm not sure how we don't have a "huge" amount of traction. The coefficient of friction of that tread was measured to be 1.1-1.2. If we wanted to max it out we could go for natural rubber that 254/968 used this year and get about 1.3. I'm not sure how this isn't the maximum amount of traction teams have been able to get. Tank treads have been experimentally shown to only get a minimal increase (about 3% according to Andy Baker and testing he did with 45), if any (according to most. Paul Copioli will probably fight to the death on this one) at all.
Wheels are 6" btw, and yes #35 chain.
In terms of the transmission, it is an iteration of team 33's 4 speed; which is two crash shifters in a row. This Drivetrain is designed around the AndyMark Gen 3's (or a slightly modified 3 motor AndyMark single speed). We wanted to do something fun and different for for prototype though, and it didn't hurt that the material for the 4-speed was significantly less than the cost of two Gen 3's. Also, we figured the 4 speeds would give a better spread of gear ratios to show in person for prototyping next season (I think most people on the team who aren't into drivetrains would benefit from seeing 6fps vs 9fps vs 12 vs 16 [those aren't the actual speeds, just arbitrary numbers]).
I believe we are traction limited in the bottom two gears, and the speeds depend on the size of the output sprocket on the transmission. I think they have a 10 T on there. I have the excel at home with all the speeds (I'm going home tomorrow, and will post then). Even though the lowest gear is way past traction limited, that isn't necessarily a bad thing; it will allow for amazingly precise alignment and will be able to hold position better while drawing less current. I'm referring to a PID loop that will hold the robot's heading (even stationary, I think the triplets did that amazingly in 2006) very accurately.
EDIT: EricH; thanks for referencing that. The wheels are very similar to last year, just bit wider now. We were losing tread because we had two bolts side by side that almost cut the tread and have, so it was very easy to tear off. We fixed it before champs by changing it to single bolts like in the picture. Haven't lost a tread since. Too bad you won't be seeing it at San Diego again
... but there is allways LA! (although, I'd much rather see 294 on the field with 330 than against.... I think 294 would have a better chance of winning that match with you instead of against)