Goal: Build a 2 speed or greater, continuous mesh transmission (no gear switching) out of nothing but vex parts. It must be some what small and only use 1 extra motor/servo (so if the standard drive train was 2 motor drive you can use 3 motors/servo).
Lets see if you guys can come up with the answer I got or something better.
There good but they use meshing gears. Meaning you can take teeth off a gear if you shift to may times. From what I have heard from users of that shift is that they tend to go through gears quite a lot (some times it breaks at unhelpful moments). As for the shift I came up with, does not have these problems.
ive never had a problem meshing or breaking teeth. as long as you bevel the gears and a linear shifter you’ll never have problems. i made some impovements to the shifter by locking each set of gears together. it runs fine with out it. im like and open source kind of person and like to show my designs to people cuz theres always ways to improve and the more minds that go into it the better it gets and you find more ways that it wont work, but that could spark ideas in something better.
Well, there’s lots of talk about what people have done with ones that don’t require gear switching but how do you do it? I’ve experimented with a chain, bicycle type, shifter but never really got it to work consistently. So, how do you do it?
For last years challenge that shifter went through 3 complete tournaments, 5 4-hour demenstrations of straight use, and so many hours of testing and driving that I can’t count it.
We never broke a single tooth of a gear, never had to replace anything because of wear and tear, and we are using the same gears we used last year on this years transmission (no new gears were made) and they are still going on strong.
If people are complaining about my teams shifter I haven’t heard a word about it as no one has sent me emails about it. If you have any problems, I would like them to send me a PM, a message, or something so that I can hear them and try to learn why their shifter is breaking and ours is not.
~Team Unlimited (FTC #1) and Head Engineer Patrick
Why don’t you share what you came up with. I’ve done some research and don’t see an effective way, in VEX, to change the gear ratio with out moving some gears around. We can probably improve on your design too. The more minds working on a problem the better.
I’ve been thinking about this for a while (even before lowfategg posted) and can’t come up with a true CVT without meshing gears.
The closest I’ve come is to use the diff from the advanced gear set to sum the output of two motors. One motor is geared for torque, the other for speed. You can run one or the other, or both to get a turbo boost. The downside is that you’d need four motors for tank-style driving.
It should work except that enough back pressure (like in a shoving match) might cause the high-speed motor’s clutch to slip. You could omit that clutch from the design at the risk of stripping the motor’s gears (wasn’t the point of the exercise to protect all the gears?). I suspect experimenting with where the clutch(s) go in the gearing might yield a workable design, but I’ve not tried to build such a beast so it is just a theory.
As for meshing gear transmissions, most of them I’ve seen slide one gear along an axle between two (different) gears in parallel planes such that the teeth are meshing in from the side. Has anybody made one that switches the gears by toggling a drive motor on an arm in the same plane as the gears? I guess the difficulty is keeping the arm pressure high enough to keep the gears from slipping. If it worked, it seems like it might be easier on the teeth. Anyway, I’d like to hear anecdotes about the pros or cons of either design.