Small hub motor

General Discussion about electric bicycles.
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dogman dan   100 GW

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Re: Small hub motor

Post by dogman dan » Nov 24 2021 7:12am

Very nice setup for flat.

I have a mile or two of flat near my house, but groceries are down a big hill into town. Climb the hill to the store could work, but it always meant climbing the big steep hill to home, loaded with groceries for me.

hemo   100 W

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Location: England, GB ( UK).

Re: Small hub motor

Post by hemo » Nov 25 2021 11:32am

For flat terrain and gentle inclines is it's intended use as well as the odd undulating converted old rail track routes we have in the UK, I have a tow hitch so I can add a light trailer with 75kg pay load ability. My main use is commute and shopping with the trailer I can ferry my beekeeping stuff to the local apiaries within 6 miles of home. We are legally limited to 250w continuous rating in the UK as is a lot of other places in the world, so to comply with no need to register or have insurance with our bikes or to ride on bridleways and cycle ways. No reason why though we can't have the temporary higher power if needed.

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neptronix   100 GW

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Re: Small hub motor

Post by neptronix » Dec 01 2021 12:24pm

For a small hub motor, i would consider ebikes.ca's Shengyi SX2 very very strongly.

It is not the lightest motor in the world but per lb, the power it outputs is great.

Seems to be the most efficient geared hub on the market ( peak efficiency is ~87%, average for the class is 82% ), outside of mechanically questionable ones like Keyde's which claim to be up to 90% efficient.

In my opinion, for 26 inch wheels or below, the Shengyi is a slightly better design, using a *slightly* lower reduction ratio and 1 less pole. This absolutely translates into less iron/gear/magentic loss. It will have nothing like the insane burst power of a MAC as a result but during cruise, you'll see efficiency and thus lower heat, which is the achilles heel of every geared motor that dramatically limit your ability to beat the piss out of them with >3x the rated power :mrgreen: :lol:.

( and afaik we haven't really cracked liquid cooling for geared hubs yet )

Put the Shengyi SX2 in a 20-24" wheel and you will have a hard time keeping the front wheel on the ground at >1kw.. :mrgreen:

Power per weight has a strong correlation to efficiency. I have not ridden a shengyi sx2, only seen it on the ebikes.ca simulator.
So this is speculation and not a lot of people have tried out that motor despite it's super impressive specs.

I'd personally buy one if i had time to play with electric bikes at the moment.
"Love and compassion are necessities, not luxuries. Without them, humanity cannot survive." - Dalai Lama

My first major build: 1.6kW 8T MAC motor on a Trek 4500 MTB.
Monster MTB: Leafmotor 1500w @ 4kW on a Turner O2 full suspension.
The monster scooter: Heavy duty Cannondale semi recumbent - under construction.
Blue Dream: Maxaraya FS semi recumbent and high efficiency mid-drive - under construction.

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