After taking a poll, it seems a lot of the teams who browse Chiefdelphi are going to be building dual transmission robot. I guess I would define this as a robot that can shift gears (low to high).
Now with this information, can someone post what they have done in the past? I’m particularly interested in “on-the-fly” gear switching mechanisms using spur gears or a built gear box. But post anything and everything you’re willing to share.
Last year we used drill motors for propulsion. We used servos to shift gears. The problem is you had to be standing still to shift. We had a spring go from the servo arm to the shift lever. The spring acted as a servo saver and wouldn’t stall the servo. When the servo arm would swing left/right the spring would pull on the shifter. It worked pretty well.
Anton,
If you’re willing to build your own shifting transmission, I suggest you look at a moped/minibike transmission, they do auto shifting AND RC car transmissions. We are attempting to develop shifting but as yet all our ideas are unproven
Best Wishes
Steve Alaniz
“Ted, I think the microwave just exploded your soup” - Sally Forth
" Once agin, technology turns on it’s masters." - “Ted Forth”
*Originally posted by Wayne Doenges *
**Last year we used drill motors for propulsion. We used servos to shift gears. The problem is you had to be standing still to shift. We had a spring go from the servo arm to the shift lever. The spring acted as a servo saver and wouldn’t stall the servo. When the servo arm would swing left/right the spring would pull on the shifter. It worked pretty well.
Wayne Doenges **
Could you post some pictures for this spring lever.
See if someone has a picture of the HOT BOT from last year they had a trick shifting mechanism using little air cylinders. I don’t know if they used it but it looked really cool
It is also possible to shift both drill motors with one servo. We did this on Big MO two years ago. However you still have to stop to shift. On-the-fly shifting is the way to go. By the way, HotBots shifting did work last year. Now if only there was pictures.
Our team is going to try to shift on the fly by having 2 sets of drive wheels that are always spinning (one set for high gear, one set for low gear) and putting the high gear wheels down with a pneumatic. I am skeptical of it but only time will tell.
A transmissiom would be cool - anyome thought of using something smple like a bicycle chain dereiler? This would be failry easy if using one drive wheel - harder if two drive wheels -
you’d need a differential - really hard if using a 4 wheel drive.
The drill press stacked pulleys are really the same thing has the
typical bicycle gear cluster, and I have seen designs for 'infinately variable speed transmissions based on two parabolic cylinders and a drive wheel.
Remember automatic transmissions work because of fluidic coupling - ie they are clutch less. Manual transmission rely on the
very sophisticated feedback system of a human mind to match the
speed of the motor to the speed rnage of the wheels.
So while I see that some of you suoer sophisticated teams will want to be both super fast and have super torque, think about all those gears and sprokets and things getting strewn all over the competition floor. What is the problem you are trying to solve? Is a multi-speed transmission the only way to do it?
*Originally posted by Mike Rush *
**Why shift? Why not a continuously variable transmission? Any thoughts? **
Personally, I love this idea to bits! Being from the “Computer Science” side of the force, I’m not exactly sure what the best way is to make one of these contraptions. I think other teams have done it with varing degrees of sucuess? Could those teams who have made CVTs please tell us about them? Pictures too! Thanks!
One idea which we had, but we did not use it, was that there be a cradle for the chain on the gear. then, a high torque, low speed motor was taken and made to pull this cradle left and right and make the chain go from gear to gear. We did not consider this design because a bike chain is required to be used. It is same like a multi speed bike. Need presicision work
We did consider building a CVT, but we decided against it. We came up with a much better idea, and it is simpler and easier to build. I won’t tell you what it is our how it works, but anyone going to Cleveland or Chicago will get a chance to see our secret drive system in action and on display. I bet you all can’t wait to see…
*Originally posted by thedillybar *
**Our team is going to try to shift on the fly by having 2 sets of drive wheels that are always spinning (one set for high gear, one set for low gear) and putting the high gear wheels down with a pneumatic. I am skeptical of it but only time will tell. **
We are doing essentially the same thing, Fast and Slow wheels, powered by the same drill motors, but to conserve space only skid plates will be used in conjunction with the fast wheels.
We were considering a dual motor CVT using planetary gears and had the basic design, but didn’t have time or expertise to engineer all the details. Maybe next year.
A student on our team suggested spinning the ring gear of a planetary gear set. He argued that in low gear you would realize the benefit of the drive motor and the motor spinning the ring working together to give you high torque, while in high gear you would get increased speed with both motors working together.
I didnt believe this to be true, however. I agree that in one case you do get both working together to give you high torque, but its not a true transmission (since there is no gearing going on), so in the high gear both motors are not in fact working together.
We are, in fact spinning the ring gear this year. I am not divulging how many motors/type (at least, not yet), but we are using the spinning ring gear transmission. The student on your team is right and wrong about the motors working together.
They actually don’t work together. If you simply coupled the output of 2 motors together, you would get more torque, but at a fixed gear ratio. What the spinning ring gear gives you is variable gear ratio. Simply put, if you spin the ring gear and the sun gear in the same direction, you get a low gear ratio (fast output speed). If you spin the ring gear in the opposite direction, you get a high gear ratio (low speed output). The motors do not at all work together! The ONLY thing the ring gear motor does is spin the ring gear and react to the loads of the sun gear motor (input motor). This means of transmission is inefficient, because the ring gear motor has to react to forces normally taken out by locking the ring gear against the housing; but it is very effective in varying the gear ratio.
Bottom line is that we thought it was of value, but have spent a year and a half perfecting it and making it work.
Thanks Paul, you’ve helped to end a long standing controversy. I was trying to attack the problem from a static approach but encountered quite a bit of difficulty and was reluctant to dive into the dynamic problem. But yeah, i figured it was something like that.
