2 speed transmission idea

[Horshu]

He didn't actually build the tranny...just used the Yomega-style yo-yo as an example of a mechanism. The problem with using that is gonna be one of balance vs. weight. You'd need at least 3 arms to keep the load on axle reasonably balanced, but those arms add weight at a very hi-speed portion of the drive train, where that kind of weight makes a difference. Plus, I had an idea of an expandable collar, but before I even thought about figuring out what it would be made of, I just looked in there and could not find the space. I think given the space and weight requirements, the ideal tranny would have to be electronic so that anything outside basic actuators could be offloaded to another portion of the chassis; with a mechanical transmission, you have to do it with more physical parts (weight) *at* the point of gears meshing.
The biggest step then would simply be any kind of gear-switching mechanism. I'm thinking a raised motor whose polarity has been reversed (either at the motor or at the ESC or, if you connect via Dean's, a polarity-reversing adapter) In that space you've created, two tiny gears of differing ratios (maybe if you're lucky, the stock RS motor pinions will work, and just cut them in half to shorten them) gears connect the motor to the pinion; the gears themselves are connected to each other on a rocker switch. The rocker needs to be electronically flippable so that at any given time, one of those two gears are between motor and plastic pinion (maybe have electro magnets behind each so that turning on one pulls a gear away and pushes the other into the system). Need to shift can be determined any # of ways, but since we're electronic and using Dean's connectors (I'm not trying to shill them, but they're relatively universal), we can add an amperage (load) detector between the motor and ESC such that when load is high, we can upshift; if load is low, we can downshift. Looking in my chassis, there does seem to be room for this, so the big issues would be getting gears of adequate ratio and then...GEAR SYNCHRONIZATION! Maybe if you could electronically lift the motor a hair during shifting, it wouldn't be a problem, but outside that, I really can't think of a good way to get a shift to occur without tearing up the gears.

[Capt.ArD]

that's a little like what i had imagined originally. i had wanted to stay away from an electric actuator, cuz that would require more wiring and is a huge hassle. but i guess that is probably the most weight/space efficient and simplest design.

as for the gear, i put up a picture earlier of a gear that had teeth that tapered out, so one end had 2x the teeth of the other end. something like that would provide the more "seamless" or smoothe gear shift that you would want.

to keep the tension on the system, or get you extra hair of lifting for the motor, put the motor on a mount with a hinge on one side and a tension spring on the other. when the larger gear engages, the motor is allowed to move up, but the spring keeps it in contact by pulling it back down. this would also let you shift back down.

hope it helps.

PS: i have a friend that has a small mill, i will show him our ideas and see if he can make a prototype.