DIY Onyx style build advice

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Shazzy   1 µW

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DIY Onyx style build advice

Post by Shazzy » Mar 23 2020 10:02am

Hi all,

Ebike newb here, but with experience in electric skateboards.

I am looking to build a DIY Onyx style moped like the image below to carry two people (roughly max 170kg combined) and will be used for a runaround rather than anything major.

Image

I was planning on welding my own frame together and making my own batteries, most likely from Samsung 30Q cell. Any other suggestions for cell?

My question is what power rating for the hub motor should i use to sufficiently carry a maximum of 200kg at roughly 20mph?
Links to products that ship to the UK will be appreciated.

Thanks!

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dogman dan   100 GW

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Re: DIY Onyx style build advice

Post by dogman dan » Mar 25 2020 6:49am

For two, you will want to run a larger DD motor than typical in the 1000 w kits. Select a voltage to match the max speed you would like, but have a big motor with lots of copper in it, because an uphill start with two people on it, or a longer steeper hill, will require 2000w.

48v might be fine, and 40 amps controller. Better to overkill the motor, then underkill the controller, than run a motor so overloaded that it heats up. Even if melting is not an issue, running it inefficient will still be a problem for battery capacity.

Shazzy   1 µW

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Re: DIY Onyx style build advice

Post by Shazzy » Mar 26 2020 4:51am

Thanks appreciate the feedback.
To get started I was thinking about the voilamart 1500w kit and slowly upgrading over time.

Would you recommend any other hub motors below the £200 mark?

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dogman dan   100 GW

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Re: DIY Onyx style build advice

Post by dogman dan » Mar 26 2020 5:57am

Been so long since I actually bought anything. Literally, 10 years. People used to just send me stuff to test to destruction. Still have a garage full of survivors.

But for the type of power you would be looking for, just make sure the motor is heavy enough to handle some watts. If the motor laced in the wheel is 15 pounds, its a 500w rated motor.( used in the 1000w kits) you need the one that weighs a lot more, in more copper and magnets. Then its able to go a lot higher watts.

What you are looking for is the wider motors, wider magnets bigger copper core. You can see in the picture that the bike has a bigger motor than used in the typical, affordable kits.

MikeSSS   100 W

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Re: DIY Onyx style build advice

Post by MikeSSS » Mar 27 2020 11:54pm

As an example of a heavier direct drive, my front hub wheel weighs 25 pounds, this is on a 26" wheel, with tire and tube installed. Battery is 48v, 13s, 4p. The motor winding in this hub delivers about 25 mph top speed, about 40 kph.

This DD hub motor would be inadequate for your use. My total weight, bike, stuff and me is about 265 lb, 120 kg. Starting from a stop I down shift into 42x22 and pedal with some effort, using just enough throttle to move away at a normal non ebike acceleration. Once rolling the hub gives a nice cruise in the 14 to 18 mph range, with me pedaling at a non ebike 12 mph effort. Well, 12 mph when sitting upright acting as an air brake. That same effort on a road bike, on the aero bars, would be faster.

Climbing is done at slower speed, downshifted and pedaling at a cadence of around 80 and a heart rate of about 150 bpm. Enough throttle is used to reduce the pedaling effort some. The hub motor heats to a few degrees above ambient, but this climbing is slow and much like pedal only riding. Carrying a passenger would be too much load for this hub motor. I mention this because it's my experience with a 25 pound wheel, using a direct drive hub.

Dog Man Dan has far more experience to advise and I agree with him. To carry two people and pedal less vigorously, the wheel would have to weigh substantially more than 25 pounds. At least that's how it looks to me.

Keep us posted on your plans, what you do and how it works.

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dogman dan   100 GW

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Re: DIY Onyx style build advice

Post by dogman dan » Mar 28 2020 8:03am

Perhaps I was not clear enough. I meant motor alone weighs 25 pounds for the bigger motors. The 500 w rated typical kit motor will weigh about 25 pounds with rim, spokes, rubber, and a pound of slime in the tube. 15 pound bare motor weight.

My 5304 motors weigh about 35 pounds in the wheel with rubber. They have a 35 mm wide magnet or something like that. Typical for the 500w rated dd motor is 27 or 28 mm.

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