Electric hub for an alternative project

[samsquatch]

Hey folks, my first message here. I found this place while researching electric hubs. I have an alternative idea to use powerful electric (battery) hubs to move large objects. In particular, I'm asking you kind folks here if any e-bike manufacturers offer a product line that offers high torque, low speed hubs. We're talking max speed at less than human walking speed (1.4m/s, 4.5ft/s, 3.1mph). And I think a standard bike hub/wheel/tire would work (that is, if y'all think a single one could support a 500lb load at these slow speeds) A 26" wheel, then means a max speed of 40RPM.
As for the torque requirement.. I was hoping to be able to climb grades of 30% with that 500lb load - does this seem reasonable?

Are there product lines that offer high torques with a gear ratio high enough to max out around 40RPM? Am I looking at a 48V lithium system? 1000W or is more power required?

Thanks for any assistance!
Cheers

 

[billvon]

As for the torque requirement.. I was hoping to be able to climb grades of 30% with that 500lb load - does this seem reasonable?

Not unreasonable, but you will likely have to do some rewinding of an existing motor.

The approach I would take is:
-Find a good geared hub
-Get the largest # of turns on it (lowest speed) you can
-Put it on the smallest wheel you can lace (or attach somehow)

That gives you the most possible torque from the motor. If that's not sufficient you may have to rewind the motor to change its motor constant. More turns = lower speed/higher torque for a given voltage and current.

 

[samsquatch]

Thanks for the quick reply.
I haven't spent any time in this industry, and I don't plan on it (God knows I have far too many other hobbies to commit time here) - do you have some recommended products that I could Google search?
Also, the project is definitely ad-hoc, so I'm looking for eBay / salvage / used parts to complete this project.

Do you have some literature on rewinding one of these motors? Perhaps someone here has done it before? Thanks
SAM

 

[MadRhino]

Some manufacturers will do the winding that you need, if you are willing to wait. It would not be more expansive than a faster winding. Winding one yourself is PITA, and not certain that you will succeed at first try. I would not use a geared hub to climb a load on 30% incline, for the clutch and gears would not survive this abuse very long. IMO, you’d better order a very slow winding DD hub and reduce your size of wheel to the minimum acceptable for your application.

Then, you need to understand that 500lbs is not a heavy load for a hub motor. Your only problem is the slow speed that you want to do, because all hub motors on the market are wound too fast for it.

 

[markz]

http://www.ebikes.ca/tools/simulator.html?bopen=false&motor=MX4506&cont=C40&wheel=10i&hp=0&mass=170&grade=20&batt=B2412SLA

 

[Chalo]

We're talking max speed at less than human walking speed (1.4m/s, 4.5ft/s, 3.1mph). And I think a standard bike hub/wheel/tire would work (that is, if y'all think a single one could support a 500lb load at these slow speeds) A 26" wheel, then means a max speed of 40RPM.
As for the torque requirement.. I was hoping to be able to climb grades of 30% with that 500lb load - does this seem reasonable?

Your requirements will be orders of magnitude easier to meet by using a gear reduced motor (hub or shafted) coupled to your drive wheels with a secondary sprocket reduction. Hub motors simply don't do that combination of high torque and very low speed. You'd be making, or failing to make, the proof of concept.

Look around you. Every single electric powered device that moves slowly, uses high ratio reduction to do it. What's your reason to use hub motors for this specific job?

 

[samsquatch]

What's your reason to use hub motors for this specific job?

I'm looking to remove the requirement for an axle/transaxle because I want the load to be suspended from a bracket above & between the wheels, for stability & traction purposes.

The load will be a heavy log (as in cut up tree) sections. The load is to be straddled by the wheels, pinched via skidding tongs, and then lifted off the ground by lever force. Then, a remote speed control / potentiometer would control direction/speed of wheels.

Basically, the prototype will be a battery operated log skidder that I can fit into my small trailer for tree removal operations.

Cheers
SAM

 

[Chalo]

What's your reason to use hub motors for this specific job?

I'm looking to remove the requirement for an axle/transaxle because I want the load to be suspended from a bracket above & between the wheels, for stability & traction purposes.

Got it. You can do that, and all wheel drive, with gearmotors located in front or back of the wheels. Further, that would also allow you to use ATV wheels or the like rather than only what you can get to fit on a hub motor. And of course the motor to wheel speed ratio becomes whatever you want.

It also seems like a great application for skid steer, with both wheels on each side chained to the same motor (perhaps above the midpoint between the wheels). That would give you the most compact footprint for whatever load bed size you need. And only two motors would be required to drive all four wheels.

 

[billvon]

I'm looking to remove the requirement for an axle/transaxle because I want the load to be suspended from a bracket above & between the wheels, for stability & traction purposes.

The load will be a heavy log (as in cut up tree) sections. The load is to be straddled by the wheels, pinched via skidding tongs, and then lifted off the ground by lever force. Then, a remote speed control / potentiometer would control direction/speed of wheels.

First off, you are going to be better off with a lot of driven wheels here. Your #1 goal is going to be torque, and if you have 4 driven wheels you need only 1/4 the torque from each one.

Second, you're probably going to need more torque than most bike wheels can give you. Your application is more in line with a motorized caster, which is a common application. You can get them off the shelf; they are very slow and very high torque. If they don't give you the wheel diameter you want, perhaps consider something like the 12T MAC motor mounted in a small a rim as you can find (12" ?) You probably won't be able to lace that like a bike wheel, so you'll have to machine something fancy to carry the rim.

 

[MadRhino]

You won’t have traction to pull logs in the mountain with bicycle wheels. Your problem is not power anymore. You only need one horse power to pull a log in the forest, but you need the traction of a horse.

That is the kind of build that does the job;

 

[samsquatch]

And only two motors would be required to drive all four wheels.

First off, you are going to be better off with a lot of driven wheels here. Your #1 goal is going to be torque, and if you have 4 driven wheels you need only 1/4 the torque from each one.

I'm shooting for only a two wheel machine - for compactness, lightness, traction (two wheels more traction than 4) and ultimately, the two wheels will serve as the fulcrum point of my lever to lift the load (or one side of a longer load) off the ground.

with gearmotors located in front or back of the wheels

Do you have a photo example of this configuation? I could be interested in this, if a hub motor is not my answer.

That is the kind of build that does the job;

Looks like an incredibly versatile machine, as far as log skidding (pulling it out of a forest) goes. But my use case is a little different. I will actually require that at least one side be lifted off the ground, and that the machine straddle the load. The goal being: I want to torque my way up a trailer ramp and drop the load, and walk the machine back over the straddled log, back down the ramp for the next one.


In all reality, 500lbs is a huge load and I can cut logs smaller according to the motor's designed loads. But obviously, I can save time by being able to haul larger chunks up the ramp.
And RE tire size: smaller lends more torque, but larger wheels are beneficial in that they provide a higher fulcrum to lever (larger diameter logs) as well as handling rough terrain / bumps / and trailer ramps easier. I think I'm picturing 2x 26" "fat" tires on hub motors?
Part of me wants to build a non-powered prototype, but I don't want to have to redo the bearing assemblies/hubs once I find a suitable motor, know what I mean? Hey there's an interesting thought - my assembly probably doesn't require a hub, but more of a pillow block bearing?

 

[Chalo]

with gearmotors located in front or back of the wheels

Do you have a photo example of this configuation? I could be interested in this, if a hub motor is not my answer.

I don't. But here's one from the web:

The motor in the photo is a direct drive motor, but you would use a gearmotor with built-in reduction.

The same arrangement works for single-sided wheels. The point to putting the motor in front of or behind the wheel, instead of sticking out the side, is to make room aboard the chassis for your payload.

I think you'll need something with much fatter and squishier tires than a bicycle has, especially if you're trying to do the job with two wheels. 30 percent grade is not fooling around. If you reckon a 500 pound load plus say 150 for your vehicle, then you're looking at having to develop about 200lbf of push just to maintain equilibrium. Add more to overcome friction and rolling resistance, and then even more to accelerate from a stop and gain elevation. It's a lot to ask of bicycle tires, and even more to ask of the little piece of dirt a bicycle tire sits on.

 

[fechter]

I can't think of any hub motors that are geared low enough to be suitable for this application. Something like what Chalo shows seems more doable. You don't need a lot of power since the speed is low, but you need a lot of gear reduction between the motor and wheel.

A motor like this one might be closer to what you want:
https://www.ebay.com/itm/24V-350W-E...594897?hash=item2a18511ad1:g:jzIAAOSwezVW1N92



This motor has one stage of gear reduction built in. Combined with a wheel that looks like the one above, you'd be getting close. The sprocket on the wheel has to be as big as possible and the one on the motor as small as possible.

Electric wheel chair motors would be pretty similar. Sometimes you can get a whole chair on Craigslist for cheap when somebody dies.

 

[MadRhino]

I don’t know if your goal is to pull logs up a trailer ramp only, or to pull them from the spot where you did cut them.

Up the ramp into the trailer, is a winch job ideally. But yes, ramps can be made with enough traction surface to pull them logs on wheels.

Terrain is another story. Forest, even forest roads, offer very different traction potential with seasons and locations. Machines that are made to pull logs to transport facilities, are on wheels taller than a man with 500 lbs chains on them. The only way to do this job with small machines, is to use caterpillar track. The traction that you will have on small wheels, will rely on ideal terrain and that is not often seen in any forest zone.

 

[samsquatch]

Electric wheel chair motors would be pretty similar.

Precisely my first thought, but then the larger wheels and height led me to explore e-bikes as the right industry to find my solution.

Sometimes you can get a whole chair on Craigslist for cheap when somebody dies.

Dear God I LOL'd here, but now me thinks that means I'm going to hell

Machines that are made to pull logs to transport facilities, are on wheels taller than a man with 500 lbs chains on them.

If we're logging 84" redwoods, then yes.

But for the urban arborist trying to load soft maple I'm removing in someone's backyard.. a compact tool that can pick up <30" logs and assist me loading into a trailer is going to be a back- and time-saver. And, I think the added weight and only two tires will add to the traction ability. And 30% may not be realistic for my trailer ramp either, that's just a figure with some error built in.


I did find a potential neat idea: A Stepper motor with a 50:1 worm gear:
https://www.ebay.com/itm/L76mm-Nema23-Stepper-Motor-Worm-Gearbox-50-1-Driver-Kit-Power-Supply-DC48V/202180395178
A stepper would be nice, for going up/down inclines - would negate the need for a hand-operated bicycle style brake. But does using a stepper motor mean I need a fancy (READ: expensive) digital controller?

 

[billvon]

Precisely my first thought, but then the larger wheels and height led me to explore e-bikes as the right industry to find my solution.

The wheels themselves may be what fail you here.

Let's take Chalo's numbers. You are going to need 200 lbs of force at the edge of the wheel. Depending on what hub motor you choose, that means ~400lbs at the hub. That's a lot to expect out of 14ga (or even 12ga) spokes.

You will likely be better off with two of these:
http://kellycontroller.com/car-hub-motor-72v-7kw-p-711.html
These can give you about 60 foot-pounds each, which gets you to 120 lbs of drive (24" wheel.)

 

[markz]

A used forklift motor would work quite well, then gear it to what you want on atv tires, or tracks.
DIY for tracks would be belts for conveyors or snowmobile tracks.
http://www.6x6world.com/forums/general-6x6-atv-discussion/4057-home-made-tracks.html

https://www.kijiji.ca/v-snowmobile-parts-trailer-accessories/calgary/polaris-snowmobile-track-144/1376573543?enableSearchNavigationFlag=true

BC # for snowmobile junk yard --> https://www.kijiji.ca/v-snowmobile-parts-trailer-accessories/calgary/snowmobile-wrecking-yard/1378014406?enableSearchNavigationFlag=true

Studded Track - http://www.2040-parts.com/_content/items/images/74/2009074/001.jpg

 

[John in CR]

A pair of direct drive wheelchair hubmotors is what you're looking for.

 

[Chalo]

A pair of direct drive wheelchair hubmotors is what you're looking for.

Since most of those have worm gear drive, they'll hold fast when stopped, without back-driving the motor. That seems like a good virtue for the application. One drawback is they'll constrain the depth and width of the load bed more than a motor mounted forward or rearward of the wheel.

 

[samsquatch]

Hey! I found this similar topic on this forum:
https://endless-sphere.com/forums/viewtopic.php?t=84843
This poster was talking about a low speed wheelchair hub motor. I think I'll ask what motor they went with - seems like a similar application to mine. I would also appreciate a reverse feature, although I'm not sure if that's possible with a gearmotor?
This gearmotor seems very promising, and they're selling out of my home state MN!
https://www.ebay.com/itm/Bison-336-Series-24V-DC-1-8-HP-30RPM-Gearmotor/122636142124
Cheers
SAM

 

[Chalo]

This gearmotor seems very promising, and they're selling out of my home state MN!
https://www.ebay.com/itm/Bison-336-Series-24V-DC-1-8-HP-30RPM-Gearmotor/122636142124

That one has an applicable speed range, but low power. You can raise the power by raising the voltage, but that raises speed proportionally. If you raise the power by using more current, you will run into overheating issues when working the motor hard. That's a brushed motor-- with cheap and simple controllers available, and reverse by switching polarity-- but the brushes will only tolerate so much overcurrent or overvoltage.

 

[John in CR]

A pair of direct drive wheelchair hubmotors is what you're looking for.

Since most of those have worm gear drive, they'll hold fast when stopped, without back-driving the motor. That seems like a good virtue for the application. One drawback is they'll constrain the depth and width of the load bed more than a motor mounted forward or rearward of the wheel.

I have some old style wheelchair motors and gear reductions that are just like you say, a motor driving a worm gear with a big reduction, 32:1 if I recall correctly. What I was talking about though is a direct drive hubmotor with a very slow wind. I think Amberwolf has or had one, and it was a heavy beast.