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Brushed DC motor HP requirements for Longboard? Answered

So I have 2 brand new tilt/trim pump motors and thought about making a set of matching electric longboards since products like Boosted Boards seem to have become fairly popular.  I am not too sure whether the tilt/trim motor would be strong enough though, they are a decent size motor though.  But it got me thinking what size is required for an electric longboard?

The main problem with the tilt/trim pump motors is that I can't find specs on them anywhere, just specs for tilt/trim pump assemblies they are off of, but nothing about the motor itself other then SAE J1171 Marine rating.  Because of this I thought of buying another DC motor to do the job.  (Picture of tilt/trim motor)

The constraints for me is that I have a couple 12 - 24v 100A motor controllers already, for brushed motors only.  As well, I want to just pick up a couple cheap $40 12v, 24AH Sealed led-acid (SLA) batteries from the local Ace Hardware and run either a 12v or 24v motor.  

Options on eBay for affordability purposes range from 12v, 24v, 90v and 180v dc, obviously 90v and 180v are out of the question.  Looking through the 12vdc and 24vdc motors, there are many fractional HP motors available.  I was looking at something like this;


Running 1/4 HP at 24v, would 1/4HP be enough though?  I know electric motors HP ratings are lower then petrol engines, a 6.5HP petrol go kart runs about the same as an identical kart with a 1HP electric motor.

If that isn't enough I am thinking a 2/3HP motor from Holley might be better?


Wondering if someone has an idea for sizing.  I know lots of eBikes and Chinese electric mini bikes and things have 500W motors, so roughly 2/3HP, so I can't imagine I need more then that.  As well I don't want it to go too fast (fear of speed wobbles) but if anyone would have an idea of sizing that would be super helpful!

9 Replies

QuadrifoglioBest Answer (author)2016-08-30

This one looks suspiciously like yours, right down to the paper tag that starts P07. If so, it is a 5200 RPM, 12 VDC, 5.3A motor. That works out to be about 1/15th HP and about 60 watts. The recommendation I saw was for 1000 to 3000 watts. At 12V, that is 80 to 250 amps.


No on the Dayton 4Z143. To begin with, it is physically too big.

Take a look at the electric longboards on Instructables. You need to make a conceptual shift from “industrial” to “radio controlled hobby”.

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That does look a lot like mine. Guess I will have to find other uses for those ones.

I wanted to avoid using the little outrunners, that and they seem wildly optimistic in their power rating, the boosted board I believe has 2 rated for 4000W each! I really highly doubt you could actually get 11HP of those 2 little motors they use.

I wanted to do industrial because I am also mounting everything on a Mountainboard rather then a longboard. Part of that reasoning is because I have heard many horror stories of longboards with outrunners being garbage because of all the venting and being mounted rather low to the ground, unless you run the board in a clean room, the life of the outrunners is not worth their cost. They die pretty quick because you get dust, rocks, water and what not in them. I figure, go the sealed industrial (And cheaper) route.

The Mountainboard as well handles better, has "brakes" (which work but are mostly for speed control especially on hills), handles rough or uneven pathways better, etc.

What are your thoughts on the Holley motor? 2/3 HP, 500W, roughly the same power they use on eBikes and things it seems like. Cost is good too! Haha!

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Two Intructables that have actually built and shown the
result of non-outrunner “vehicles” are:



They both used 1/2 horsepower motors.

1. A wheel chair motor style minus the gearbox.

250 watts


2000 RPM

20 amps

That calculates to be 0.58 hp.

It looks like:

12 tooth sprocket

36 tooth wheel sprocket

(RPM x Tire Diameter) / (Gear Ratio x 336) = (MPH x 1.6) =

(2000 rpm x 12.5 inch) / (3 ratio x 336) = (25 mph x 1.6) – 40 kph

2. MY1016 300 Watt, 24V Electric scooter motor



2750 RPM


That calculates to be 0.46 hp.

11 tooth sprocket standard

68 tooth wheel sprocket

Vurp reports “Doing the gear and motor calculations top
speed is about 10-11mph or 18-19kmh which seems about right. I have been
thinking about ways to increase this without spending too much more.” which
puts it right in your expectation of 15km/h.

(RPM x Tire Diameter) / (Gear Ratio x 336) = (MPH x 1.6) =

(2700 rpm x 8 inches) / (5.82 ratio x 336) = (11 MPH x 1.6) =
17 kph

Based on people who have actually done it, it looks like a 1/2
horsepower 24v 2700 rpm electric motor would fit the bill. However, there was not any information on
inclines so you will have to balance the need for more power with the decrease
in battery life. I have done the first two; the rest is up to

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Oh ok, those Instructables are really helpful. I think I might grab a Holley 2/3hp motor there, $40 is a good price and 2/3hp sounds like more then enough then. I am not too worried about inclines, light inclines, but for steeper ones, using it for powered assist to the rider is fine. Thanks for the help.

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Before you buy anything, plan out your drive train. The motor sprocket will need to fit on the motor shaft (diameters). The wheel sprocket will have to be smaller than the tire for clearance (diameters). You will need to figure out how to mount the wheel sprocket and still have brakes.

You will need to work up the gear ratio to select the number of teeth on each sprocket. At 3500 rpm, you will need to go up to a 72 tooth wheel sprocket and find a 10 tooth (less available) motor sprocket to maintain about the same gear ratio Or an 80 wheel and an 11 motor. Or leave it a 68 wheel and an 11 motor. However this will have a higher top speed (est. 22 kph) and less torque and acceleration.

You need to know how you can mount the motor (face mount, saddle mount, u-clamps, band clamps). Also, you only have one mounting position with a clockwise (CW) only motor so make sure it is oriented correctly.

Also, there is lively debate over 12V vs 24V (or 36V, 48V, or 72V) and I really didn't see a clear victor in the 12V vs 24V debate (a hot topic on trolling motors).

Good hunting.

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The difference I have read between 12v and 24-96v is mostly the amperage used. This might be of more concern for someone with more space and can use more batteries or this or that. But I have limited space, so I can use 2 thin 12v, 24Ah batteries in parallel for a 12v motor or those same 2 batteries in series for a 24v motor. The 24v motor would draw 1/2 the current, but the Ah rating for the batteries is also halfed compared to the 12v system. Like wise I could use more, smaller batteries for a 90v system, but overall there shouldn't be really any difference, run time should be the same on all of them. As well I think higher voltage is used if you have longer leads because you have less losses, for a foot long piece of wire to a motor on the back of a board I don't think should be a big deal.

For my purposes, 12v is fine. I ordered 2 Holley motors, they knocked off the shipping, $80 for 2 seems like a decent price (I am wanting to make 2 boards, one for me, one for the SO). I already figured out the drive train, they sell kits for mini bikes and other small vehicles that come with a great length of chain, and a choice for sprockets. I think I have to go with 10 teeth on the motor, its the smallest that comes with a 8mm D bore hole. And then I can get anywhere from 60 to 80 teeth for the driven sprocket. I want to wait and make sure the shaft is 8mm D bore before I order.

For mounting I want to use a aluminum angle iron frame to hold the batteries and mount the deck to and mount a set of MBS trucks to either end of it. MBS sells a brake kit, not entirely sure if I want to use it though, I have one of their Mountainboards already and the brakes are mostly speed control, with small wheels and not too much weight, braking isn't great and they easily lock. I use them for long rides when I don't want to be worked hard constantly trying to control speed by maneuvering the board, and they work best for lighter slopes, steep slopes you have to slalom to keep yourself from getting into speed wobble zone. Might look into using harder yolks in them. If I could use the motor for braking though, that might be helpful.

Mounting the motor shouldn't be too bad, Mountainboard trucks are pretty robust and have holes ready for mounting the brake kits. I plan to use them to mount the motor. Yes, I noticed it is a non-reversible motor. Wheels are also set up to have brake disc fitted to them making it fairly simple to mount a sprocket to. But I did want to make the frame to hold the batteries and mount a deck too, not a curved deck though, just to help keep everything secured better then strapping batteries to the bottom of a curved board and hoping for the best. I have a pretty good plan, I just want to start getting some parts so I can adjust accordingly.

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From the drawing for the Holly (on the Ebay page), the shaft diameter is 0.312" +/- 0.0002" OD vs. 8mm ID (0.314961") for the sprocket. That difference is the preferable condition. The 0.272 dimension is for the "flat"; where the set screw contacts. The shaft has a usable length of 0.750".

Braking has got to be difficult on a MB. Not enough and you don't slow down. Too much and the board stops and you don't. Most of the brakes I saw looked like bicycle caliper pads, however, there were some disc brakes that looked interesting. Of course "interesting" always = $$$$$.

The motor and gear train will provide some "engine braking". How much remains to be seen. Also, the effect of over revving the motor remains to be seen.

Sounds like you have the design well in hand.

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Yes, but my luck they won't be D shaft when they arrive! Haha!

Braking is better on a mountainboard then a normal skateboard, but just the weight, size of wheels, you can't get them to stop fast enough to throw a rider off, although they are usually on the back, and you get better braking ability with front brakes. The motor driving the back, the brakes on the front. That might be a good combo.

Looking at batteries right now, Lithium Iron Phosphate seems to be the battery to go with now a days, like a Lithium Ion, but less explodey. I found 12v 22Ah ones like the SLA ones I was looking at for ~$100 each.

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And they are 2000W motors, 4000W total, still seems a little out there asking 5.5 HP out of 2 pill bottle sized motors. Also, I don't need it too haul me around at 35km/h, like a boosted board, I would be quite happy with about 15km/h top speed, and I have no problem gearing the motor down more as well.

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