Bike not moving when putted on the ground

[Yves]

Hi,

my specifications:
I have an electric motor 36 V , 450 W and 450 rpm mounted on my old (heavy) bike. I placed three batteries of 12 V, 14 aH in series ( each has a weight of 5 kg) together with a 36 volt controller. I tried to make an electric scooter of it (instead of a bike) so the pedals are useless. Backrear has 18 teeth, motor has 10 teeth. The wheels have a diameter of 68 cm.

my problem:
as long as the backwheel does not touch the ground, the wheel spins very fast. Once the bike is put on the ground, the motor spins together with the (back) gear wheel, but the wheel itself does not move... I suppose I do not have enough Torque to get the bike moving ?? How much watt would be needed to get my old bike moving? Could There be another cause for this problem? As i see a lot of conversies movies on youtube with a motor with less wattage that do move ?(+fast!)

thx

 

[Woosh]

there are several possible reasons.
Post some pictures of your bike so we get an idea what we are dealing with.

 

[Yves]

Hi,

In the attachment you can see the bike in ist original state. Tomorrow i will take some picture of the bike as it is now + the batteries

 

[Yves]

Hi, in the attachment you can find more pictures.

Originally, there was a sturmey archer 3 gear on the backwheel. I removed the inner parts and placed a longer axle that could fit with the motor adapter plat.
Remark: the construction with the controller and batteries is less than 25 kg. Even without a driver the bike does not move. This means if I should take everything off the bike, except the motor, and sit on it (85kg). It would still not move... thatswhy i think the wattage of the motor is not the only problem?

 

[Yves]

I had the construction to get everything in place + the Wheel spinning off the ground on video but i am not able to upload these files ( to big)

 

[Woosh]

let's make sure we know where we are.

1. Can you spin the motor wheel forward by hand without resistance?
2. Can you spin the motorwheel backward?

 

[Yves]

let's make sure we know where we are.

1. Can you spin the motor wheel forward by hand without resistance?
2. Can you spin the motorwheel backward?

When i pull the backwheel by hand , the motor Wheel spins forward and backward without and resistance. More difficult is to directly pull on the motor Wheel itself. It spins back and forward but i have to use more force. Although I think this is normal?

 

[Woosh]

on a conventional hub conversion, you have two freewheels.
The existing freewheel is moved from the old wheel to the motorwheel and performs exactly as before, it lets the normal chain pull the wheel when you pedal and freewheel when the motor takes over.
The other freewheel is built inside the motor's casing. It lets the motor drives the wheel and freewheels when you pedal without power.
I think your motor does not have an internal clutch. You can't realistically pedal the bike without power.
If the motor was originally made to run on a much smaller wheel, it won't have enough torque to drive a much bigger wheel.
You should check with the vendor which wheel size the motor was made for.

 

[Ocsid]

Is it spinning the right way round when off the floor?

 

[Kwozzymodo]

Looks good. Looks heavy, and with the batteries and rider, will likely be 110kg plus. I like the dutch bike look. I have done a couple of front wheel conversions with rear rack batteries.

Once you get it moving, make sure the brakes are up to stopping it!

 

[Yves]

Hi woosh , the following freewheel was delivered together with the motor. (See attachment,)Normally the old freewheel together with the new one are put on the Wheel as in this video

. But because it is an old bike, i am unable to put this new freewheel on the backwheel. So i connected the old freewheel with the motor. I guess that could be the problem? Could it work if i buy a wheel to which the new delivered freewheel does fit?

Regards

 

[wheeliepete]

By removing the internals of your hub, the spocket is no longer connected to the wheel. With the wheel off the ground, it is turning only by friction, there is no mechanical drive.

 

[Yves]

Hi wheeliepete , that could also make Sense. .. Problem is to put the longer axle into the existing sturmey archer gear hub. But i will check and try

 

[Woosh]

Yves, you have a hub gear, you should consider a front hub motor.

 

[Yves]

Hi @Ocsid, it is moving fast and in the right way when off the ground. @ woosh, yes maybe i should have done that... , but first i will still try to get this fixed anyway. It would be sad if I am not able to do this and a waste of money thx

 

[Yves]

Will let you know when I manage to get the gear hub working again. Could take a while as i am not an expert in assembling a gear hub... + not much time during the week. Regards , thanks for the help!

 

[Yves]

Hi,

I put the sturmey archer gear hub back together. 1 small part is lost. ( 1 of the 2 pals connecting the hub with the Wheel...).

I tried it anyway. Again the Wheel was not moving when putted on the ground. On the ground, only the axl of the wheel is turning around. Not the wheel itself. Also, the wheel can not be rotated backwards (manualy) when putted on the ground.

If I keep the Wheel off the ground, turn the motor to full power, and then put the Wheel back on the ground, the bike moves for about 20 cm...

I'll try to order the missing part of the gear hub. But for now, i dont have a good eye on this little project...
In the attachment you can find some pictures of the bike with everything attached.

 

[Woosh]

Hi woosh , the following freewheel was delivered together with the motor. (See attachment,)Normally the old freewheel together with the new one are put on the Wheel as in this video

that motor fits only a hub with threads on both side, the motor goes to your left side, the normal chain stays where it is, on the right side.
The Sturmer Archer is not normally threaded on the left side, so you can't use that motor with the SA gearhub.
Did you install the motor on the left side like on that video?

 

[Kwozzymodo]

Aren’t you just freewheeling the hub with things set up like that?

 

[Yves]

@ woosh, I turned the Wheel so the thread of the sturmey archer was on the opposite side side of the side where the original chain was. As you can see in the pictures.

This afternoon, I turned the wheel in its original position and replaced the motor (Same side as where the original chain was). Same problem, only difference was that the wheel spins backwards when of the ground.

Why would the motor not work on the sturmey archer gear? I cant believe the functioning of the motor depends on the type of wheel you are using...?

@Kwozzymodo , yes I suppose the sturmey archer is not properly fixed... As wheelepete said , i also think the spocket is still not connected to the wheel as i am missing a piece (pal). And because the axl is spinning but not the wheel I assume this is the problem...?

Or does the motor not have enough torque... ? (Hope not )