Practical mad science

[RamblinRover]

Anybody got any great ideas for a small differential gear set that can rate about 360lb-in torque from an existing worm drive box? Or should I look into friction disk torque limiters?

[Qaaaaa]

Might run into turbo encabulator clearance issues with that setup

[RamblinRover]

One option is to steal the diff gear set from a scooter transaxle and throw the rest away, since those are available on eBay readily for $50-$60 used. By the truckload. I'm just not sure if there's a better option.

E.T.A.: ...and it would only be a little short on power handling. Most such scooters only have about half my desired torque number, but "it'll probably work".

It could be put through the worm drive quite easily, as that has a hollow output.

[Chariotoflove]

@ramblinrover What's the application?

[ClassicDatsunDebate]

@ramblinrover Really depends on the ratio/final drive speed.

[RamblinRover]

@chariotoflove As per the picture, front wheel drive or part of electric 4WD on a 40% scale Land Rover.

The picture is how one would package a Honda GX35 1.5 horse engine and Automation Direct WGA 63M series worm drive gearbox under the hood of one. Potentially.

[RamblinRover]

@classicdatsundebate Well, unless somebody can recommend one that has a 40:1 or 80:1 final drive ratio, what I'm chiefly looking for is something that one could use as just a set of spider gears. Since most of my options require stepping down an input so much (for ~45RPM or thereabouts) and packaging is hard, ideally something to use as spiders.

Now, I did think of how with mechanical advantage, one could probably build one's own spiders out of two lower rated ring gear sets in a custom tube case... possibly with two extra pinions. Those gears would need to be okay for 1/4 the normal rating at most.

Edit: so rather than needing to deal with 300+lb-in, a pinion set suitable for 75lb-in would be fine, most likely. Since the gear surfaces in shear would be quadrupled with four pinions and two ring gears.

[RamblinRover]

I may have my answer:
https://www.ebay.com/i/310724131684?chn=ps

[BaconSandwich]

Right. I saw your post over on DriveDribe about this. I'm almost wondering if there'd be some way of doing it direct-drive with a set of in-hub motors from either e-Bikes or some sort of electric scooter. I wonder how difficult it'd be to make an adapter that, instead of spokes, would hook up to whatever wheel it is you want to use.

[ClassicDatsunDebate]

@ramblinrover Have you thought about a right-angle gearbox or perhaps a lawnmower transmission? If you buy a helical bevel ring gear and pinion, you'd have to build a carrier.

[frinesi2]

https://www.superatv.com/offroad-atlas/polaris-perfect-front-diff/

[RamblinRover]

@baconsandwich I have been waaaaay into that. The problem with hub motor solutions in addition to the aesthetics and cost is the fact that there's way too much speed and way too little torque.

If you go to low-speed hub motors (geared), the aesthetic and cost issues only multiply.

I've looked at trying to do individual packet motor setups one per wheel, but cost starts running away... right before inability to package and other issues do as well.

I looked at managing the diff question with freewheels at each of the front wheels - and if I'm building electric and suffering the problem of no diff function at back, it's easy to make it 4wd when going forward only. If, however, I build a gas-powered FWD alternate, it would need true diff function or be next to undrivable.

[RamblinRover]

@classicdatsundebate The problem with using a classic right angle gearbox is that most don't include diff function. Lawn mower transmissions are an idea, but other than those for a rideon, don't have the kind of torque capacity I'm looking for - and rideon transmissions are expensive.

The disadvantage of having to build a carrier is offset a little by the fact that any such work is easy to duplicate, it can fit the needs exactly, and the spiders don't really have to be that well designed in their support. They just have to "diff" a little, and they just have to bind hard enough to hold the axles against each other.

I'm pretty sure I have a good idea in the back of my head with 2 1/2" 1/8" wall tube, 3" wall tube, a couple of bearings, and two plates.

[BaconSandwich]

@ramblinrover said in Practical mad science:

@baconsandwich I have been waaaaay into that. The problem with hub motor solutions in addition to the aesthetics and cost is the fact that there's way too much speed and way too little torque.

One of the things I've been thinking of is building my own Axial Flux motor. With the right gauge of wiring, it might be possible to drop the RPM enough to do a direct drive. There's a guy who wrote a book about it, and I'm tempted to buy it and give it a shot: http://www.amazingdiyprojects.com/electric_motor.html

I wonder if something like that with a simple gearbox - two gears resulting in a reduction, would be enough.

I'm really itching to do something with an EV, but on a smaller scale as well. Finding all the information about what motors are available, what controllers there are, and how to make it all play nice is... challenging.

If money were no object, I'd go for four of these: https://www.yasa.com/yasa-750/ but at supposedly $10k a piece, that's roughly ... a lot more than I can afford or would want to pay.

[RamblinRover]

@baconsandwich said in Practical mad science:

One of the things I've been thinking of is building my own Axial Flux motor. With the right gauge of wiring, it might be possible to drop the RPM enough to do a direct drive. There's a guy who wrote a book about it, and I'm tempted to buy it and give it a shot: http://www.amazingdiyprojects.com/electric_motor.html

I started off wondering if it would make sense for me to build my own hub motors or kit stuff together, but about at the point where it became clear I'd need to wind my own to get what I wanted and face serious limits on low-speed power, I started reviewing other options.

Just one of those things, where if I ever wanted to be able to replace a motor, off-the-shelf sounds better and better.

[BaconSandwich]

@ramblinrover I understand. It does seem like a ton of work.

At least with the lower RPM stuff, there's fewer windings and thicker wire/ribbon.

[ClassicDatsunDebate]

@ramblinrover I know this conversation would be more efficient over a beer, but have you looked at direct drive with syncronous motors and a Vector drive? Constant torque and speed control via an analog input you could achieve with a rheostat in a throttle-by-wire. Then the transmission would only need to be a cardon shaft.

I love this stuff

[RamblinRover]

@classicdatsundebate Considered motors per wheel and some fancy gimmickry, but ultimately it's hard to get enough torque at the front wheels with a motor solution able to direct drive. If you package individual wheel motors at the middle of the chassis, you're looking at minimal improvement over a motor transaxle, and you can get those brand new with 21:1 reduction (not enough to do serious hillclimbing, but some) brand new for $250.

I considered doing the front motors as "helpers only" with maybe 30% of the overall torque capacity, but it wasn't ideal.