Help for a Newbie please??

[Gotwind ben]

Hello.
I tried posting this in the Technical section but was not allowed for some reason.
I have bought a rear hub motor without a rear freewheel gear.
I then bought a 5 speed screw on freewheel.
As the image shows, it doesnt screw on as close to the hub motor as I would like and therefore will not fit into the rear dropouts where i have 135mm of space.

Am I missing something?, do hub motors require a special type of freewheel?

Many thanks for any help - very frustrating

 

[flecc]

No, they are standard freewheels, but as you will have seen, they don't have much length of internal thread and on many like those from Shimano, there's an internal shoulder stopping threading right through.

It looks like there's too much length of thread on this hub motor.

If this was one of Suzhou's usual motors, the cable would be on the freewheel side and you'd be able to take that motor sideplate off and grind off the surplus thread. That's still possible, but with that motor you'll first have to take off the freewheel, then remove the motor sideplate opposite the freewheel, then remove the spindle nut that holds the motor core into the hub and withdraw the motor core.

With the motor spindle out of the way, you could then use an angle grinder to carefully remove the surplus thread from the hub side, leaving about 10 mm width of thread only for a standard Shimano multi-freewheel.
.

 

[Gotwind ben]

Thanks flecc.

I went to my local independent bike shop today and they found a single screw on cog, meant for somekind of hub gearbox, charged me £10 though

At 13 teeth it suited my purposes as I am making a pedal generater, all be it without a freewheeling ability.

Today, I managed to generate 300 watts via pedal power with a 24v hub unit and a gear ratio of 3.4:1 (43:13)
That was hard going, 100 watts was sustained for 15 minutes, then I was knackered.


I managed to choose the warmest day of the year so far, hence clothing removed in the background

Well, 299 watts peak.

 

[NRG]

.....

At 13 teeth it suited my purposes as I am making a pedal generater, all be it without a freewheeling ability.

Today, I managed to generate 300 watts via pedal power with a 24v hub unit and a gear ratio of 3.4:1 (43:13)
That was hard going, 100 watts was sustained for 15 minutes, then I was knackered.......

I've got to ask as I'm curious....why? What's the generator for?

Did you see this? YouTube - Human Power Shower - Bang Goes The Theory - BBC One

 

[onmebike]

When I first looked at the picture I thought it was a trick question, the freewheel appeared to be on a thread intended for a brake disc. The cable coming out of the other side appeared wrong as I've never seen that before.

 

[Old Timer]

It`s been a long time since i built my rear block on my evans but I seem to remember selecting each ring one at a time and screwing them on as opposed to buying a pre made block with no gear choice. Maybe that would help?

 

[Blew it]

Just to refresh your memories.

This is about man-powered electricity generation, I don't think the machine is going to ridden as a bicycle.

Preliminary

 

[flecc]

Thanks flecc.

I went to my local independent bike shop today and they found a single screw on cog, meant for somekind of hub gearbox, charged me £10 though

At 13 teeth it suited my purposes as I am making a pedal generater, all be it without a freewheeling ability.

Today, I managed to generate 300 watts via pedal power with a 24v hub unit and a gear ratio of 3.4:1 (43:13)
That was hard going, 100 watts was sustained for 15 minutes, then I was knackered.

Single freewheels and cogs usually don't have that internal shoulder the multi ones need for strength, if I'd know it was just for generation I'd have suggested that.

As you've found though, generating power is hard work. Research figures suggest that a fit male in their best years can sustain when cycling roughly the following:

300 watts for about 10 minutes continuous.
200 watts for about 1 hour continuous.
100 watts for about 5 hours continuous.

but since the energy conversion involved efficiency loss, you can't get those out. These motors may only be 70% efficient as motors and probably less when used as generators, so you may get half or less those figures in practice.
.