Do you know the rpm rating of chinese 500w direct drive motors?

[dgncsk]

I barter a rear 500w motor. Very good condition but on a 26" Wheel. I have a big 700c frame which i want to build a DIY Project based on. Can you please tell me the possible max rpms of 500w direct drive motors? My plan to fit it as a mid drive motor that seen some time ago on cargo bikes. If this is not feasible i will install this on my DIY recumbent as a rear Wheel, or i will buy a tandem bike and replace its rear Wheel for family rides. Thank you in advance.

 

[Wheel-E]

Do you know what motor it is? Different 500W motors run at different speed which also depends on the voltage.

 

[Woosh]

you don't see maximum RPM (aka noload speed) quoted for direct drive motors. This is because they can be so high that it cannot be met when mounted on a bike.
You need to start with the controller. If the controller is a 36V 20A (typically fitted to a 500W direct drive motor), the maximum speed on a bike is about 28rpm on a flat road without headwinds.
If the controller is a 48V 25A (typically paired with 1000W direct drive motor), the maximum speed is 32mph.

 

[dgncsk]

it is 500w 36 volts with hall sensors. there is no clue on manufacturer of this motor. heavier and bigger than my bafang geared hub motors.

actually what i want to try is to run nexus 3 speed hub at back on same chain, then it will be using auto shifter when it accelerates with help of this motor. autoshifter has a hall sensor to detect wheel speed. motor will look very weird between my legs but this is DIY as you know.

if it gets overheated during slower rides, i will try a geared hub instead.

Any comments?

 

[Woosh]

actually what i want to try is to run nexus 3 speed hub at back on same chain, then it will be using auto shifter when it accelerates with help of this motor.

are you saying you have autoshift on your Nexus 3? I haven't heard of this.

 

[dgncsk]

yes sir. that nexus is different than pull push type one. there is a rod coming in and out. so autoshifter accessory is just a motor a hall sensor and 4x aa batteries. it shifts up and down according to the speed of wheel.

please check this link. this is from a local bike shop.
http://www.ozceylanbisiklet.com/Shimano-Nexus-3-Auto-D-Elektronik-Vites-Degisim-Unitesi,PR-6692.html

it is cheap but works like a charm. approx 30 USD.

 

[Woosh]

please check this link. this is from a local bike shop.
http://www.ozceylanbisiklet.com/Shimano-Nexus-3-Auto-D-Elektronik-Vites-Degisim-Unitesi,PR-6692.html

it is cheap but works like a charm. approx 30 USD.

Nice!

I take it that you have a front hub motor?

 

[Deleted member 4366]

They're normally around 28 mph at 36v in a 26" wheel, so 292 rpm, but that's not guaranteed. You need to spin it up and measure it with a cycle computer. You can change the speed by using different voltages, so 24v would give about 200 rpm and 48v around 400 rpm.

Geared motors are better to use as crank-drives because they have the free-wheel in them, otherwise you need a freewheeling crank.

If you want a freewheeling crank-set. I have a couple of new ones from Cyclone, which I would sell at £50 each. They come with bottom brackets.

 

[dgncsk]

Nice!

I take it that you have a front hub motor?

on that bike no motor is being utilized yet. only auto nexus 3 at back. that is why i want to make it mid drive like.

 

[dgncsk]

They're normally around 28 mph at 36v in a 26" wheel, so 292 rpm, but that's not guaranteed. You need to spin it up and measure it with a cycle computer. You can change the speed by using different voltages, so 24v would give about 200 rpm and 48v around 400 rpm.

Geared motors are better to use as crank-drives because they have the free-wheel in them, otherwise you need a freewheeling crank.

If you want a freewheeling crank-set. I have a couple of new ones from Cyclone, which I would sell at £50 each. They come with bottom brackets.

i think i will do something improvized on freewheeling issues. what should be the max rpm when connected to crank set? what do you think?

 

[Woosh]

on that bike no motor is being utilized yet. only auto nexus 3 at back. that is why i want to make it mid drive like.

mid drive is a good choice for the Nexus 3 but you are more or less restricted to the Bafang BBS01B or Tongsheng TSDZ2. Any more power may be too much for the Nexus 3.
http://wooshbikes.co.uk/?cdkit
In your opening post, you were talking about a 500W direct drive motor. They are usually hub drives, not mid drives.

 

[dgncsk]

yes they are. my inteniton is to use huge 500w direct drive hub motor as a mid drive motor by connecting it to crankset or to single gear at back by welding another one on it. may be for a cargo bike...

or i will use this 500w direct drive rear hub motor on a tandem bike with a normal shifter, and forget this project for a while. mid drives are way expensive.

 

[wheeliepete]

Seen a few mid drives using hub motors, great idea if you can do some fabricating of mounts etc. 3 speed hubs can take a bit of stick if you are careful. Great project.

https://www.google.co.uk/url?sa=i&rct=j&q=&esrc=s&source=images&cd=&cad=rja&uact=8&ved=0ahUKEwjcyKal06jZAhWFBcAKHVCLCgUQjRwIBw&url=https://electricbikeaction.com/hanebrink-x2/hanebrinkmotor/&psig=AOvVaw2SqymcZObMUSZfeespZou-&ust=1518808498468944

 

[dgncsk]

i saw this. to use my 26cm wide motor, i have 3 options. 1st, by using normal 700c bike with relatively large frame, between my legs or, right behind saddle upright. 2nd, on my DIY recumbent project, semi finished. 3rd, building a cargo bike for my kids placing motor in front of rider right before the Cargo space ( may b with an additional chain connection for a recumbent tandem rider in front of me). lets see what will happen next. it seems i will not be able to sleep few nights again...

 

[Deleted member 4366]

i think i will do something improvized on freewheeling issues. what should be the max rpm when connected to crank set? what do you think?

About 100 rpm, depending on how fit you are. If you're a regular cyclist, you might want to go to 120 rpm.

 

[dgncsk]

lets make it 90 rpm... i am lazy.

without a freewheeling crank, i realized that pedal assist sensor will have no use since pedals will be moving all the times when motor is on. i will convert single bmx sprocket and a normal crankset into a frewheeling hybrid crank set, i hope.

 

[dgncsk]

can we rename this topic to DIY 500w middrive? ( "poorman's mid drive" yes that is me in this scenerio)

 

[Woosh]

can we rename this topic to DIY 500w middrive? ( "poorman's mid drive" yes that is me in this scenerio)

I think you underestimate the effort in creating a crank drive kit with a direct drive motor. If you absolutely want to design a crank drive kit, start with a geared hub motor, its smaller dimensions, weight and built in clutch will make the kit easier to build. The difference in cost is very small. Direct motors have very poor yield at under 200 rpm, most of your electric energy will be turned into heat. Stay away from them, it's a false economy.
This is one example of CD kits:

 

[dgncsk]

i have a 500w direct drive and a 250w hub. so no problem. setup will be ok for both types.

 

[Deleted member 4366]

Here's one I made long before crank-motor kits were available. maybe it'll give you some ideas or you can learn from my mistakes. It actually worked quite well. It had the advantage that the throttle was completely legal because you could only operate the motor when you were pedalling and the motor stopped when you stopped pedalling, though actually the motor pedalled you rather than the other way round: