Hub motor AXLE Cutting and modification

[edgefx1]

i have a question pertaining to axels of hub motors for ebikes. i have a typical generic 750w hub motor kit from amazon: ( https://www.amazon.com/ZeHuoGe-Electric-Brushless-Front-Delivery/dp/B07L88F7L2/ref=sr_1_13?crid=2EZL9RKK7VMJT&keywords=750w+motor+kit&qid=1671465207&sprefix=750w+motor+kit%2Caps%2C75&sr=8-13) , the hub motor is a direct drive with 2 axels meant for a front drive set up, my question is as follows:

can i cut the axel on one side, effectively turning it into a single axle mount?

i plan to modify my razor pocket mod frame to a delta trike with independent suspension, at current my set ups is 2 hoverboard motors converted to air tires, mounted on a mountain board truck, thats tilted at an angle and can lean:

i plan to replace the truck with atv suspension arms ill be welding to the frame. i already have one of these motors and cost wise buying another is the most economical route as opus to getting a specific single axel motor x2, i plan, if mechanically feasible, to cut the axle off of one side and mounting it as a single axle motor, but im not sure if thats mechanically strong enuff, worse case scenario would be just outright pressing out the current axel and just replacing it with a purpose built single axel instead.

the reason im doing this is to add more height for better visibility when i have ot be in the streets, and to have the ability to properly lean the trike. thanks to anyone that has some cents to share on this.

 

[amberwolf]

i have a question pertaining to axels of hub motors for ebikes. i have a typical generic 750w hub motor kit from amazon: ( https://www.amazon.com/ZeHuoGe-Electric-Brushless-Front-Delivery/dp/B07L88F7L2/ref=sr_1_13?crid=2EZL9RKK7VMJT&keywords=750w+motor+kit&qid=1671465207&sprefix=750w+motor+kit%2Caps%2C75&sr=8-13) , the hub motor is a direct drive with 2 axels meant for a front drive set up, my question is as follows:

can i cut the axel on one side, effectively turning it into a single axle mount?

Yes...but the motor's axle was designed to have support at both ends for the weight it was specified to handle (if it has any spec for that), so the single axle may bend or fail under the single-sided loading. Many axles are not very hard metal.

If you do use them this way, I recommend installing the axle so it's flats are vertical, at the sides, not at the top and bottom; this will slighly increase the axle thickness vertically and put the stress risers of the shoulder-to-flats perpendicular to the vertical stress. Without changing the axle out for one better designed and made for this application, it's more or less the best compromise.

If you do have problems anway, you could have a new axle made, and change the bearing on that side to one with a larger ID (same OD so the cover doesn't have to be changed too), that is larger in size and of better harder metal. While you're at it, you could use the same torque-transfer method that the Grin All Axle motor or GMAC motor uses, with splines on the shoulder and a long torque arm on those splines, and then a regular round axle, so you get better torque transfer without the flatted-axle problems (which include less thread area for nuts to torque against, and stress-riser problems at the cuts on the axle flats-to-shoulders, etc).

 

[amberwolf]

Regarding the motor changeout, then other than wheel size, are you having problems with the existing motors?

Or do they overheat in the application, or not provide enough torque, speed, etc?

If they aren't at a heat limit, you can increase torque by increasing phase current from the controller.

Speed can be increased by increasing system voltage (and possibly power, if present power is not enough for overcoming air resistance/etc at those speeds).

To use bigger wheels on the existing motors, you could machine a spoke flange for the existing motors, and build whatever size wheel you want. It could be bolted on using the cover bolt points on the inboard side, and if you machine it for an interference fit on the hub shell it'll be even more secure (just heat it to do the install, then as it cools it will clamp tighly to the hub shell).

 

[edgefx1]

Regarding the motor changeout, then other than wheel size, are you having problems with the existing motors?

Or do they overheat in the application, or not provide enough torque, speed, etc?

If they aren't at a heat limit, you can increase torque by increasing phase current from the controller.

Speed can be increased by increasing system voltage (and possibly power, if present power is not enough for overcoming air resistance/etc at those speeds).

To use bigger wheels on the existing motors, you could machine a spoke flange for the existing motors, and build whatever size wheel you want. It could be bolted on using the cover bolt points on the inboard side, and if you machine it for an interference fit on the hub shell it'll be even more secure (just heat it to do the install, then as it cools it will clamp tighly to the hub shell).

well no, theres no problem right now as it is, it runs and works just fine, its a joy to ride, more so than i could possibly admit, but in this field when we get that itch to do more or upgrade, it hits hard, so upgrading to atv style independent suspension would naturally push the rear higher than the front, i can offset that by simply switch the front to a bigger wheel too, but i also want to make changes to my ebike as well, move from a front dd to a rear dd or geared hub, but when i do that ill be left with a front hub, so i figure i could repurpose that to fit the trike, but i dont want a front drive on the trike, and its alot cheaper to get another wheel kit from amazon than to get purpose built20" single shaft motor from aliexpress.

this project is basically shuffling things around to see what will end up working best, the current trike only hits 25mph max, so its not fighting any winds lol, plus im not about that speed life, this is strictly a chassis design thing more than a motor thing beyond the axle

i thought about drilling spoke holes, but was scare of the idea of not knowing the strength of that aluminum used for the motor shell of the hoverboards, right now they are already fighting back the pneumatic tires which are steel bead, in fact i blew out the original threads so i had to drill and tap new ones, interesting thing about those motor shells, if you drill deeper into the original threads that hold the covers on, you will hit steel after the aluminum, i tapped into that and used longer screws and now the cover plates are held really securely

so 1) no i have no issues with the existing motors 2)they do not over heat and have plenty of torque, and the speed is perfectly fine, from 36v motors over voted to 52vsystem 3) i dont have a lathe or mill to be bale to make exacting parts sadly, other wise id have just machined a new axel and be done lol 4) the axel being designed for double side clamp was the issue that caused me to come here, and you confirmed my suspicion along with it too, ill definitely have to fab a new axel to replace the original axel of my amazon kit

 

[amberwolf]

but in this field when we get that itch to do more or upgrade, it hits hard,

I'm sure that has never happened to anyone on this forum before.

i thought about drilling spoke holes, but was scare of the idea of not knowing the strength of that aluminum used for the motor shell of the hoverboards,

It might work fine to drill directly into the existing flanges, but I don't know how they are made or of what alloy....so unless you're willing to just try the experiment (which will ruin the rim for holding a tire), I wouldn't drill them in the rim flanges of the motors themselves, but rather make a set of flanges that bolt onto the motors in place of them.

interesting thing about those motor shells, if you drill deeper into the original threads that hold the covers on, you will hit steel after the aluminum,

That's probably the rotor back-iron (that the magnets mount to, and which carries the flux from the magnets).

i dont have a lathe or mill to be bale to make exacting parts sadly,

You wouldn't need either of those to make the flanges. If you can weld and use a hacksaw and angle grinder and drill, you can make them out of steel the same way custom wheel hubs are often DIY'd for bicycle wheels. Use a steel pipe / tube of an inside diameter that is as close as possilbe to that of the OD of the motor shell. There are a few ways to make the flanges themselves from flat steel plates. To finalize the roundness before drilling the spoke holes you just bolt the flanges to the motor, and spin the motor itself as a lathe head, and fix a tool (or angle grinder, etc) to the same thing the motor axle is attached to, so it can't move relative to the motor, and slowly move it into the plate's outer edge until it's rounded it as you like. Mark the flange and the motor while in place so you can always put it back on the same way relative to the screw holes in each one, in case any of them are not exactly the same spacing, etc., it will save a lot of trouble later if you need to take them off and reinstall them for anything. (do this anytime you take a motor apart with all the covers/etc.)

If there are screw holes (for the cover, etc) in the outboard side of the motor, you can skip the pipe / tube and welding and just use the flange plate mounted directly to those just like on the inboard side.

the axel being designed for double side clamp was the issue that caused me to come here, and you confirmed my suspicion along with it too, ill definitely have to fab a new axel to replace the original axel of my amazon kit

If you want, you can try it out first, but based on my experiences of various motor axles so far, it's probably not hard enough. (I have an old Crystalyte X5304 somewhere around here that was used always double-ended on the front of a regular bicycle by it's original owner, and probably not very hard because it was a non-suspension bike with a fairly lightly-built fork...yet the motor's axle was bent downward slightly at the ends. (and the axle actually broke off on one end when I hit a pothole with it mounted on the rear of my big heavy SB Cruiser trike, but that usage is more or less abuse of most of these motors :lol

 

[endlessolli]

I tried using a std hub motor in a one side only support szenario for a dog trailer. The trailer plus dog where only 40kg. Still, after about 300km, the axle broke.
I think due to fatigue stress. Also, the ‚spiky‘ surface due to the thread amplifies the stress in the down areas of the thread. That is where mine broke.
-> For a std Hubmotor w/ std axle, you need two sided support for a save setup.
Pressing out the axle was in my case also not possible due to the geometry of the axle and how it was glued to the motor-coils