DIY electric hand cargo trailer

io0

100 µW
Joined
Oct 20, 2018
Messages
8
Hi everyone, my name is Marco and English is not my native language so please forgive my grammatical errors.
I am trying to build an electric hand trailer capable to move 400-420 kg at a more or less constant speed of 3.2-3.6 km/h both on paved and unpaved road (though not a completely rough bumpy road). My main inspiration comes from the Carla Cargo trailer (here is an image)
electric-powered-bike-trailer.jpg

There are different models, but the main one can carry 150 kg. I like this design because it is relatively simple, cheap, wheels are not too high (20") and most of all it is missing a suspension system which would be too difficult for me to build. But considering the weight I need to move I don't know if such a deficiency is redeemable. I have many questions, of basically two types: 1) Wheel tolerance 2) Motor. I know that to answer my questions precisely there are too many variables to take into account, however I'm searching for a rough practical estimate (but if you want to share precise calculation I would be really happy too). So

1.1: In the Carla Cargo trailer 150 kg are distributed on two (maybe 2,5) wheels, which means about 75 kg per wheel. Is this assumption valid? Is it reproducible for higher loads? Would be enough to add two couples of wheels for a total of 6+1 wheels (75*6=450)?
1_2: Would using different type of wheels ( for mtb, fat bike, pitbike / made of steel, carbon fiber, special alloys) be necessary?
2.1: Are common ebike motors (like dapu M155CD) suitable for such high weights and low speed? Are special modifications needed (like changing the controller's program)?
2.2: 350-500 W motor would be enough?

If such a design is not scalable I have been thinking to use one or two braked trailer axles with elastic suspensions like the AL-KO B400 (which I don't consider ideal because of the distance from the ground (too high) and the market prices of the axles). In this case certainly weight wouldn't be a problem, but then would a propulsion given by an ebike wheel be appropriate for larger trailer wheels ( even connected to a braked axle)?

Thank you in advance for your suggestions.
 
io0 said:
and most of all it is missing a suspension system which would be too difficult for me to build
At those speeds, a suspension is probably not useful.

Instead, use the largest diameter wheels you can (29" if possible, 26" if not) because it will roll a lot easier on larger wheels over rough surfaces, curb and driveway edges, etc.

Suspend the deck from the wheels like the Carla, like my Mk IV / Mk V trailers, like my Raine Trike, with the dropout for the wheel *above* the triangulated frame around the deck. Dropout above is so you can change a wheel without tipping it up high enough to pull the wheel out from underneath, which quite difficult without unloading it. Then you can carry a spare wheel (or more) in case of flats, since it doesn't weigh that much compared to your cargo and trailer weight.




1.1: In the Carla Cargo trailer 150 kg are distributed on two (maybe 2,5) wheels, which means about 75 kg per wheel. Is this assumption valid?

It's actually distributed among three wheels, because the front wheel carries a full portion of load (or else it wouldn't have traction for the hubmotor to pull with).

The exact distribution depends on your cargo's weight distribution, and where the wheels are on the trailer.



Is it reproducible for higher loads? Would be enough to add two couples of wheels for a total of 6+1 wheels (75*6=450)?

This depends on the wheels' strength. I used four random 26" bicycle wheels on my Mk IV.5 trailer to haul a piano, which is probably similar to your cargo weight needs.
https://endless-sphere.com/forums/viewtopic.php?f=2&t=94215&p=1387398#p1387398
file.php



I used mine as side-by-side "dualies", rather than tandem, because the trailer isn't long enough to support tandem wheels, and I didn't mind the extra width.

Plus as side-by-side, they are also redundant in case of a flat or a wheel problem, since they support the same spot on the trailer and load.


1_2: Would using different type of wheels ( for mtb, fat bike, pitbike / made of steel, carbon fiber, special alloys) be necessary?

I'd recommend regular aluminum-rim bicycle wheels, just with good spoke tension and trueness. (you can learn to true, tension, and test these yourself if necessary, but if you have a competent local bike shop they could do it for you).

If you use hubmotors, I'd recommend geared hubmotors with teh slowest winding you can find. If you use DD hubmotors, use the slowest winding of those.

The DD hubs have the advantage that you can also use them for regen braking, which is helpful on slopes.

The geared hubs can't do that, but generally they will be more efficient at a higher load at a slower speed.

Build the motors into the wheels yourself, or have the LBS do it, because I don't trust the build quality of the wheels motors typically come in (and they usually have the wrong spokes; too thick for the rims they come in).

I also recommend putting one in each wheel, each with it's own controller, slaved to a single throttle (or whatever speed control you're going to use). This way you have both redundancy and can spread the load between multiple motors.

2.1: Are common ebike motors (like dapu M155CD) suitable for such high weights and low speed? Are special modifications needed (like changing the controller's program)?
2.2: 350-500 W motor would be enough?

If you're not going up any slopes, and don't need quick acceleration, it doesnt' take a lot of watts to move it, if you have low rolling resistance (higher pressure in the tires).

If you have slopes or hills, you're probably going to need significantly more power to go up; the steeper the slope the more you'll need.

I don't know the Dapu motors, so can't say.

I'm using the MXUS 3K, a pair of them, in the trike I use to pull those heavy loads, but in traffic I have to be able to accelerate very quickly to 20MPH even with a load, and am using generic controllers, one modded for 80A+, and one just 40A unmodded.

So you could use much smaller motors and controllers, if you don't have slopes or hills.
 
Thank you very much for the exhaustive reply, it was really helpful. I think I will use 6 wheels in tandem because of the width and the design I have in mind, plus only one motorized with a 350W/500W because it would exceed my budget otherwise and I can always use my arms and legs if necessary (I think I can even gain something using 6 29" wheels and a 20" one for the motor, right?) . Now I have another question: I would like to have brakes , so I was thinking of using 6 hydraulic brakes; Is there an easy way to join the hoses to one lever preserving its sensitivity? Should I use little oil boxes to multiply and balance the pressure on the discs? Or would a simpler configuration with mechanical brakes be better?
Thank you.
 
If you use one hose for all the brakes, then when it fails you lose *all* braking.

I'd just use mechanicals, as equalization of braking would be much simpler, much better redundancy, it costs way less, and given the very low speeds (despite high mass) and multiple wheels with brakes, it should still have sufficient braking power.

Plenty of good pads out there that fit any generic rim brakes; I use Koolstop.

I use two mechanical rim brakes on just one wheel (front) and it will skid the wheel if I squeeze hard enough.

Easier to use rim brakes than disc (can cut the tube sections with the bosses off existing bike frames and weld them to your trailer frame), and more braking force (for any comparable generic type) since the rotor is MUCH larger diameter.

You can insert a mechanical-advantage-multiplier (pulley, etc) between the handle and the brakes if you find you can't squeeze hard enough. Problem Solvers makes one.

You can also easily make a lock for the brake lever as a parking brake. Or add individual wheel parking brakes, like I did on the rear wheels of the trike, using something like wheelchair hand brakes.
 
Thank you deeply, your answers are always spot on and incredibly valuable. I think will post my progress as soon as I start this project.
 
amberwolf said:
If you use hubmotors, I'd recommend geared hubmotors with teh slowest winding you can find. If you use DD hubmotors, use the slowest winding of those.

Is there a broad range of available direct drive motor windings? What I've seen has been optimal for bicycle speeds, but of course that's because I was shopping for a bicycle hub.
 
io0 said:
I think I will use 6 wheels in tandem because of the width and the design I have in mind,

That will result in wheel scrub that seriously impairs maneuverability. The benefit of single or dual wheels on the same axle is that the trailer can rotate around the axle center without resistance. With multiple axle centers, the difference must be reconciled by skidding. When there's a large weight on the wheels that are skidding, it's both inefficient and hard on the wheels and structure.

You could attach extra wheels in the form of casters, which would reconcile themselves with the fixed axis wheels as needed.
 
Chalo said:
io0 said:
I think I will use 6 wheels in tandem because of the width and the design I have in mind,

That will result in wheel scrub that seriously impairs maneuverability. The benefit of single or dual wheels on the same axle is that the trailer can rotate around the axle center without resistance. With multiple axle centers, the difference must be reconciled by skidding. When there's a large weight on the wheels that are skidding, it's both inefficient and hard on the wheels and structure.

You could attach extra wheels in the form of casters, which would reconcile themselves with the fixed axis wheels as needed.

This is definitely a problem. I need a trailer long about 2.6/3 m and not wider than 1.3 m, but I need to be able to maneuver it. Initially I wanted to use a braked trailer axle (like the AL-KOs'), but I doubted a 500W geared ebike motorized wheel could produce enough torque for a regular trailer system like that and for wheels even smaller than itself, so the (impracticable/bad) idea was to use a gear motor with 55 rpm, with transmission and an homokinetic joint for a frontal steering motorcycle wheel. When I discovered that people realized all kinds of trailers with regular bicycle wheels, loading even heavy weights, I thought it could be possible to implement that design reducing width and increasing loading capacity while benefiting an ebike system with easy to roll bike wheels. However if it is necessary to have one axle to gain decent maneuverability at those weights I may very well prefer the original idea. Yet I don't know how to easily obtain propulsion and steering for such a system. Maybe with a fat bike wheel?
I did not understand your suggestion about casters, but if it adds width or moving parts I'm afraid it's not for me.
However thank you very much for replying and highlighting the problem.
 
io0 said:
I am trying to build an electric hand trailer capable to move 400-420 kg at a more or less constant speed of 3.2-3.6 km/h both on paved and unpaved road (though not a completely rough bumpy road). My main inspiration comes from the Carla Cargo trailer
Chalo has lots of experience with pedicabs and could steer you to rugged wheels/tires for things in this capacity of the bicycle type, but for a scratch build I would lean to moped tires and matching wheels for the two primary wheels since weight is not an issue (puncture resistance). Fat bike wheels/tires would be my last choice for this reason. This is definitely not a bicycle and I don't see a strong reason not to jump up to more industrial wheels/tires and sticking with the simple Carla two-side-wheel design.

Even small obstacles like door sills or driveway lips will prove to be fairly formidable obstacles from a dead stop for a 1000lb gross weight cart. You can certainly back up a bit for a short running start, etc but this is just a huge load. Gear motors certainly have an advantage for getaway torque but the typical freewheel clutch is problematic for this situation since you want a controller with reverse capability. If you want to go geared, I would recommend a Mac 16T with a locked plate adapter instead of a freewheel. Although all Macs can develop the same torque on getaway, the higher turn count motors will require less phase current to do so and so the controller and phase wiring can be smaller.

That said, this is still a huge load and the rpms are very very low. The classic Cycle Stoker comes to mind. I might think about salvaging the back end of a hardtail donor bike and grafting it onto the fork. Use this to mount up a Mac using bolt-on disc brake sprockets and get an additional 4 or 5 to one reduction. This will get the motor up into a less lossy rpm range while giving you some serious torque. This frees you up to perhaps use a double disc front hub with the brake-sprocket on one side and a regular disk with maybe BB7 disc on the other. Or a regular disc hub and vbrakes if that's your preference. The (gas) motorized bike guys also use a brake adapter that lets you put a disc rotor and an offset sprocket on the same side hub mount. Anyhow - just a thought....


StokerHandcart.png


Also:
earlier fork discussions here
reference to EM3EV Mac fixed clutch replacement
 
Maybe grin would do a custom winding in their all-axle?? And use stub axles.
Use two of them for the primary wheels to give steering and reversing, and 4x castors for the corners.
 
StuRat said:
And use stub axles.

For this weight, it's much sturdier not to use stub axles, which carry the entire load on one small part of the axle, making it much easier to bend or break them, or the frame they attach to. So the axle and the mounting point have to be larger and/or tougher materials for the same loading.

Full axles mounted on both ends to the frame will be sturdier, and carry the load thru the whole axle and both ends and the whole frame the wheel mounts to on both ends.



Regarding motorcycle or moped wheels, they would be potentially much stronger than typical bicycle stuff, and the weight doesn't make much difference given the cargo weights involved. Much more flat-resistant, too, given the difference in tire thickness. I'd still use the largest diameter tire/wheel you can find, though, so it will go up edges, curbs, potholes, etc., easier.

The main reason I didn't suggest them is that using multiple hubmotors would be harder that way (you'd have to custom-lace the wheels, and coudln't just go buy the wheels premade, like used wheels off old motorcycles/etc., or new ones from a shop, etc.).


I've considered using a pair I have here, but they're different diameters, so I'd need to build the frame of the trailer offset in height on each side to accomodate the diameter difference. In my case the wheels weigh as much as the trailer itself, but are virtually indestructible as far as my usage is concerned (I rarely need to carry half-ton loads (just the piano so far, in that range), but quarter ton ones happen every year at least (for dog food), sometimes two or three times, and now that there's four St Bernards that weigh that much in total, if I took them anywhere all at the same time, doing it in one trailer would be easier than stringing multiple trailers together.
 
amberwolf said:
four St Bernards that weigh that much in total, if I took them anywhere all at the same time, doing it in one trailer would be easier than stringing multiple trailers together.

Come on! Do it! I wanna see a bicycle road train!
 
OT, but it's been done:
https://www.google.com/search?newwindow=1&gbv=2&biw=891&bih=767&tbm=isch&sa=1&ei=s_vPW_XnIeqf0wL3np7YCg&q=bicycle+trailer+train&oq=bicycle+trailer+train&gs_l=img.3...8369.29695..30783...1.0..0.677.6121.0j26j3j5-2......1....1..gws-wiz-img.......0j0i8i7i30j0i7i30j0i8i30.rMTuW77bieg

;)

FWIW, I could probably do it with two trailers and the trike, with Kirin or Yogi in the trike, the other in the small trailer, and the puppies in the big trailer. Would have to add a hitch to the big trailer to attach the small one to.
 
Also ot, but I used to use a pedal powered trike, and two garden wagons to get a train load to the house I was painting in one trip, at the condos I used to maintain.

Trike carried tools in its basket, brushes, masking dispensers, etc. Trailer one carried 20 gallons or so of paint, in three colors. trailer two was nothing but dropcloths. Ladders I kept overnight closer to the house, but each Monday two separate trips for them.


On topic, I start to see something like the tugs used in airports to drag around airplanes might work. Something like this trailer dolly, but with electric hub wheels. Then the platform is basically a trailer with a normal hitch. With a jack on the trailer, you can unhitch when you want to, like to put the power unit away at night.


https://www.harborfreight.com/600-lbs-heavy-duty-trailer-dolly-60533.html
 
I saw this at my local lumber yard yesterday. It even had dual headlamps.......a dual battery system with a rocker switch to select one or the other, and uses common Makita tool batteries.
https://www.makitatools.com/products/details/XUC01X1
 
teklektik said:
This is definitely not a bicycle and I don't see a strong reason not to jump up to more industrial wheels/tires and sticking with the simple Carla two-side-wheel design.

amberwolf said:
Regarding motorcycle or moped wheels, they would be potentially much stronger than typical bicycle stuff, and the weight doesn't make much difference given the cargo weights involved. Much more flat-resistant, too, given the difference in tire thickness. I'd still use the largest diameter tire/wheel you can find, though, so it will go up edges, curbs, potholes, etc., easier.

I would be really happy to stick to Carla design changing just the wheels (because of my wallet), but searching specifics for the other design (with a trailer axle) I realize even the 8" wheels with 5" tires have a max loading capacity of 275 kg each and in the Carla design there is no axle, so I am not so confident that motorcycle wheels would be reliable.

teklektik said:
That said, this is still a huge load and the rpms are very very low. The classic Cycle Stoker comes to mind. I might think about salvaging the back end of a hardtail donor bike and grafting it onto the fork. Use this to mount up a Mac using bolt-on disc brake sprockets and get an additional 4 or 5 to one reduction. This will get the motor up into a less lossy rpm range while giving you some serious torque. This frees you up to perhaps use a double disc front hub with the brake-sprocket on one side and a regular disk with maybe BB7 disc on the other. Or a regular disc hub and vbrakes if that's your preference. The (gas) motorized bike guys also use a brake adapter that lets you put a disc rotor and an offset sprocket on the same side hub mount. Anyhow - just a thought....

This thought theoretically solved every problem I had, thank you very much. My idea now would be using the trailer axle plus a pit bike wheel in that configuration. I unfortunately found out that here in Italy I need to use a 250 W motor to make my project legal. I found this https://www.ebike-solutions.com/en/...-motor-250w-150rpm.html?action_ms=1&opt_29=49 150 rpm Puma motor which is 250 W, but I think that of the declared maximum input power of 900 W, at least 500 should be sustainable and with a proper reduction should be possible to move this thing. I need learn how to do a proper fork with a motor attached to it, but everything else should be easier.

dogman dan said:
On topic, I start to see something like the tugs used in airports to drag around airplanes might work. Something like this trailer dolly, but with electric hub wheels. Then the platform is basically a trailer with a normal hitch. With a jack on the trailer, you can unhitch when you want to, like to put the power unit away at night.


https://www.harborfreight.com/600-lbs-h ... 60533.html
Thank you for the reply, but I did not understand your idea very well; I need anterior brakes and I am not sure two anterior wheels would be better and more maneuverable than one; I don't even know if would be necessary to manage different rotations with a differential there.

craneplaneguy said:
I saw this at my local lumber yard yesterday. It even had dual headlamps.......a dual battery system with a rocker switch to select one or the other, and uses common Makita tool batteries.
https://www.makitatools.com/products/details/XUC01X1
Originally something very similar made me want to build this trailer. :)
 
io0 said:
...I am not so confident that motorcycle wheels would be reliable.
Just a question of getting front wheels from a bigger motorcycle instead of a moped. Box the wheel with an outer strut to carry the other side of the stock motorcycle front axle and things get simpler. Likely needing brakes on the side wheels is an unfortunate complication, otherwise common trailer wheels would work fine.

io0 said:
I unfortunately found out that here in Italy I need to use a 250 W motor to make my project legal.
Really? Is it even a vehicle? In my state in the US it's not a vehicle or even a trailer (because it's not attached to a vehicle).

If the whole 250W thing is unavoidable and you are thinking about using the chain-driven gimmick, you might also look at something like a 250W GNG mid-drive motor and a jackshaft to get further reduction using standard pillow block bearing mounts to make it easier to fabricate. The point being that once you go to the chain drive you are no longer constrained to use a hub motor.
 
teklektik said:
If the whole 250W thing is unavoidable and you are thinking about using the chain-driven gimmick, you might also look at something like a 250W GNG mid-drive motor and a jackshaft to get further reduction using standard pillow block bearing mounts to make it easier to fabricate. The point being that once you go to the chain drive you are no longer constrained to use a hub motor.

donn said:
If it would help to consider a different kind of motor - here's someone putting a 24V electric wheelchair motor on a basic tricycle. Still essentially like a "mid drive". https://www.instructables.com/id/DIY-Electric-Trike-From-Electric-Wheelchair-Motor/

But is there a benefit (for example in terms of torque) using a different kind of motor? What do I lose not using a hub motor (for example are rpms fixed in other types of motors?)?
 
io0 said:
But is there a benefit (for example in terms of torque) using a different kind of motor? What do I lose not using a hub motor (for example are rpms fixed in other types of motors?)?

I'm not the best person to answer that question, but in that example, he is using a throttle/controller to vary the motor speed. It's essentially similar to a geared hub, in his case with a ca. 10-fold gear reduction, but the point is that there could be electric motor applications, like wheelchairs, that are designed to operate closer to your desired speed and might be a simple matter of mating it to the wheel with another modest gear reduction. Where bicycle systems are kind of a special case that want to work well at an unusually wide range of speeds.

This direction actually occurred to me in the context of your regulatory issue - are wheelchairs subject to any motor power limits at all? My guess is that they aren't, and neither is your cart, as long as it doesn't over resemble a bicycle. An electric forklift would be another example, are they regulated? (and while the motors in those things are more popular for do-it-yourself electric cars, there may be lighter duty versions that could be of interest.)
 
io0 said:
But is there a benefit (for example in terms of torque) using a different kind of motor? What do I lose not using a hub motor (for example are rpms fixed in other types of motors?)?
I originally proposed using the hubmotor because of the fabrication simplification and the ease of upgrade - just buy a more powerful motor and bolt it up. The dropout mounts and brake disc offset are standard so no/few issues regarding interchangeability. A consideration will be the size sprockets you can obtain to bolt up to the brake mounts. A non-hub motor can certainly get a smaller drive sprocket on the shaft.

As donn mentioned above, I was just trying to put some other options on the table, particularly in light of your apparent (and baffling) regulatory snafu. With no idea of your budget or fabrication situation, more options seem good... :D

Although theoretically a big hubmotor with a controller that can provide huge current will work the most efficiently, this isn't a theoretical exercise and the problem of being constrained to a mere 250W motor makes gearing look attractive in spite of minor drive losses. With such a tiny motor you need to look at approaches that will get the motor operating a fairly high rpm to reduce the motor torque. Power is Torque times RPM so you can spend your power in many ways. But since torque comes from amps and amps mean heat, the best way to spend the power is to go for high motor rpm and low torque. This will reduce the heat generation and reduce the load on bearings, etc. Adding a jackshaft and another stage of reduction will improve your torque and heat situation regardless of the motor you use.

Personally, I remain somewhat unconvinced about your regulations and would suggest revisiting this for clarification. You are not riding in the kart, you are not towing the kart, it is controlled by a pedestrian walking it like a wheelbarrow - as what kind of thing is this being regulated? I realize I'm from a different country with different regs, but this seems just plain strange. If this 250W limit went away, you could look to simpler and more robust solutions.
 
Thank you both for replying.

donn said:
This direction actually occurred to me in the context of your regulatory issue - are wheelchairs subject to any motor power limits at all? My guess is that they aren't, and neither is your cart, as long as it doesn't over resemble a bicycle. An electric forklift would be another example, are they regulated? (and while the motors in those things are more popular for do-it-yourself electric cars, there may be lighter duty versions that could be of interest.)

teklektik said:
Personally, I remain somewhat unconvinced about your regulations and would suggest revisiting this for clarification. You are not riding in the kart, you are not towing the kart, it is controlled by a pedestrian walking it like a wheelbarrow - as what kind of thing is this being regulated? I realize I'm from a different country with different regs, but this seems just plain strange. If this 250W limit went away, you could look to simpler and more robust solutions.

Unfortunately Italian law is not completely clear, but is clear enough: 1) every human driven machine is a vehicle, even wheelbarrows and wheelchairs, though those have special status (work vehicles and vehicles for disabled, if they respect certain parameters that I can't respect given what I need) and can be driven freely; 2) my vehicle cannot be considered an "arm vehicle" because there is a motor ==> 3) it needs to be a "velocipede", so it can't be bigger than 3 x 1.3 x 2.2 meters and must have a motor under 250W and max speed equal to 25 km/h; if one of those parameters is not respected it will be considered a "cyclemotor" = moped and it will need approval and assurance. So it sucks and I can't do anything about it.

teklektik said:
Although theoretically a big hubmotor with a controller that can provide huge current will work the most efficiently, this isn't a theoretical exercise and the problem of being constrained to a mere 250W motor makes gearing look attractive in spite of minor drive losses. With such a tiny motor you need to look at approaches that will get the motor operating a fairly high rpm to reduce the motor torque. Power is Torque times RPM so you can spend your power in many ways. But since torque comes from amps and amps mean heat, the best way to spend the power is to go for high motor rpm and low torque. This will reduce the heat generation and reduce the load on bearings, etc. Adding a jackshaft and another stage of reduction will improve your torque and heat situation regardless of the motor you use.

This is now probably the most important point for this project, so I really need a more technical explanation. I am confident (maybe wrongly) that giving let's say 500 W motor and 60 rpm at the end, torque should be about the same regardless of the gear reduction or motor rpm. However I don't know what construction differences between high and low rpm motors are, so can't really understand why should they behave differently. The 250 W Puma motor I posted before can be bought with different specs, from 150 rpm to 320 rpm; they are the same 250 W 36 V motor (about 6.9 A), so the only thing I know is that the 150 rpm one has an higher torque. For both I will need to almost double the amps (or should I increase the voltage too?) to have 500 W in the end. Naively I would think that the 150 rpm motor, being the "mule", would tolerate better more amps and heat so why should I choose the other one? In the end they both have to generate the same torque operating at the same power; why should one generate more heat than the other? What are the constructive differences that make one better than the other?
 
io0 said:
However I don't know what construction differences between high and low rpm motors are, so can't really understand why should they behave differently. The 250 W Puma motor I posted before can be bought with different specs, from 150 rpm to 320 rpm; they are the same 250 W 36 V motor (about 6.9 A), so the only thing I know is that the 150 rpm one has an higher torque. For both I will need to almost double the amps (or should I increase the voltage too?) to have 500 W in the end. Naively I would think that the 150 rpm motor, being the "mule", would tolerate better more amps and heat so why should I choose the other one? In the end they both have to generate the same torque operating at the same power; why should one generate more heat than the other? What are the constructive differences that make one better than the other?

No, you're right - 150 rpm is for you. Where previous discussion has talked about the need for "fairly high rpms", that means, relative to this figure, 150, "Rotational speed at 36V". The higher that standard parameter, the higher the rpms you need to achieve for the same performance, so the lowest "speed at 36V" is the best for your purposes. Though since you will likely need gear reductions to match your wheel speed to the motor speed anyway, this may not be the most important thing.
 
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