I may be willing to give that a go, but was just under the impression that aluminium snapped really easily when forced beyond its formed shape.

How do you think it got to its present shape? Aluminium's a weird material to form. It's a bit like copper, but harder. If you are able to heat it up, even with one of those hot air blow guns that are used for pain-stripping, it'll be a lot easier. You don't have to bend it while its hot. The heat will anneal the aluminium to make it bendable. You might not need to heat it at all. I reckon that with a good shove, it might go. Put a block that's about 125mm thick between the drop-outs so that you don't over-do it. Once the metal has moved, it goes hard and won't bend again in the same place. If you force it, it can break, so you have to heat it again. I've just remembered that I've got a scrap frame from another bike, so I'll test my theory today and report back, so hold-fire just for now.

How do you think it got to its present shape? Aluminium's a weird material to form. It's a bit like copper, but harder. If you are able to heat it up, even with one of those hot air blow guns that are used for pain-stripping, it'll be a lot easier. You don't have to bend it while its hot. The heat will anneal the aluminium to make it bendable. You might not need to heat it at all. I reckon that with a good shove, it might go. Put a block that's about 125mm thick between the drop-outs so that you don't over-do it. Once the metal has moved, it goes hard and won't bend again in the same place. If you force it, it can break, so you have to heat it again. I've just remembered that I've got a scrap frame from another bike, so I'll test my theory today and report back, so hold-fire just for now.

 

Thanks for the info, and the offer of testing the theory.

One thing that does put me off bending the frame, is that I don't know if the servo brake will then fit on a shorter axle.

I'm making enquiries into getting new spur gears machined, which seems like the logical option.

I'm after a bit of advice here, nylon or steel?

I have no idea how much the noise level will increase using steel gears, but they would last.

Then again, nylon should be quieter, but won't be so robust. But if they're cheap enough, easy to replace if I buy a job lot.

And yes, you can take some spares off my hands if I go down this route

Steel gears increase the noise very considerably. The higher powered Heinzmann motors substitute nylon with steel and they are very noisy compared with their legal hub motors.

Steel gears increase the noise very considerably. The higher powered Heinzmann motors substitute nylon with steel and they are very noisy compared with their legal hub motors.

 

Thanks flecc, I will probably stick with nylon, as the gears seem simple enough to replace anyway.

The guinea pig strikes again... watch this space

Best would be to have a word with the gear-maker. Show them the one you've got and explain what it does.There's various grades of glass-filled nylon that would be stronger and more stable than nylon on its own. A proper gear company will know about all the strengths and life-cycles of the different polymers and should be able to advise which is best. Steel will be stronger, heavier and i guess a bit noisier, but will give more confidence if you want to use higher powers.It's a difficult call.

 

If you use the drum brake, you're back to needing a motor with a long shaft again. I was thinking along the lines of a normal disk rear motor and something like this. but with the torque arm fitted to a "P" bracket around the seat stay. It might be fairly easy to make one out of a bit of aluminium plate and a caliper adapter plate.

Brake Therapy Conversion Kit

 

Edit: Like this but better:

http://forums.mtbr.com/gt/bolt-disc-bracket-gt-187721.html

Quick update on 'The Rat' which arrived about an hour ago...

 

Believe it or not, the owner prior to the lady who sold it to me had fitted a handlebar kill switch and as soon as I turned it on, the bike sprang into life! :D

 

It has a dodgy paint job and the brakes could do with some adjustment, but it seems to go pretty much the same as my new one. It's been adapted for off-road use, with Michelin County Trial boots and a non-standard pair of bars.

 

First thing I'm going to do is the shunt mod

That was good news on your bike, evendine.

Solder about 1/3 of it's length. No more, unless you've got a watt-meter.

 

Jumped on my frame using a 65mm block between the drop-outs and reduced the width by 20mm which is about what would be needed for a standard rear motor:

Before:

http://i451.photobucket.com/albums/qq236/d8veh/General%20ebike/SANY0174.jpg

After:

http://i451.photobucket.com/albums/qq236/d8veh/General%20ebike/SANY0176.jpg

 

I tried a brick as a spacer first (both edge-ways and flat) but the frame just sprang back to 135mm. You have to get it to go over the elastic limit, which will be different for different frames. The wheel still appears to be central with the right offset for the' gears. difficult to tell exactly because a normal back wheel doesn't fit anymore so I used a front one with spacers to check. Make sure that the frame is horizontal before jumping on it or you might be riding round in circles.

No-one can say you lack courage d8veh

Opened the Rat's battery case and found this:

 

http://www.notjustmetal.com/pics/RatBMS.jpg

 

Does it look familiar to anyone? Seems to be an old version (has a 2008 date marked on the board).

 

Was intending to do the shunt mode, but as this board is different, not sure doing it will be safe.

Edited January 15, 201214 yr by evendine

That board is the BMS that controls the battery discharge and charging voltage. There's a shunt in it that it uses to limit the maximum current - probably 20 amps, which is the max safe discharge for the battery.

 

You need to find the controller that's in a little compartment in the frame underneath the battery. The shunt is inside the controller and by soldering it, you can increase the current that it will give from 12 amps to about 18 - a 50% increase in power but not speed, although your average speed will increase. Don't expect too much range from that battery after soldering.

Opened the Rat's battery case and found this:

 

http://www.notjustmetal.com/pics/RatBMS.jpg

 

Does it look familiar to anyone? Seems to be an old version (has a 2008 date marked on the board).

 

Was intending to do the shunt mode, but as this board is different, not sure doing it will be safe.

 

Here you go me old china, give this a go before you blow yourself up

 

http://www.pedelecs.co.uk/forum/technical/9183-cyclamatic-controller-mod-walkthrough-pics.html

The poor chap's way to fixing a hub motor with broken teeth

 

My apologies for the ambiguous title.

 

Was all geared up for replacing the Cyclamatic's broken hub spur gear, with either another nylon one or a stronger steel one.

 

That was until I attempted to remove the defective one.

 

It's held on with a circlip, and I thought that once I removed that, the gear would slip off.

 

Wrong

 

No amount of coaxing and tugging and prising worked to get the gear off its spindle.

 

Plus, the gear's bearing appears to be make of soft cheese, and easily dented and buckled.

 

So in the end I thought f*** it, and cut into the nylon part of the gear with a hacksaw, with the intention of just pulling that part off the bearing.

 

Then after tugging at the split nylon cog to separate it from the bearing, the whole b****y thing popped off anyway

 

So, does the hub work with only 2 spur gears in the assembly?

 

In a nutshell.... yes.

 

Who knows for how long, but that's what experimentation's for.

 

[ATTACH]3069.vB[/ATTACH] [ATTACH]3070.vB[/ATTACH]

 

Sorry d8veh, the steel gears have been put on hold for now.

Understood, but what I'm wondering is should I expect a voltage sag under load sufficient to cause the green light to go out using a brand new fully charged standard 24v pack?

 

Others have said this already, but I can confirm this is normal on a brand-new Cyclamatic & battery. I can tootle along at 1/3rd throttle with the green light still lit, but any more juice and it goes out.

Here's my first 'Rat' shunt mod - probably a little less than 1/3 of the length:

 

http://www.notjustmetal.com/pics/ShuntMod1.jpg

 

Noticeable improvement climbing hills, which is what I was hoping for - motor noise sounds higher pitched than it was...

 

I take it blowing the controller FET's is the main danger in increasing the current further - have been thinking of applying some thermal grease between their heat-sink and the controller case to help lose heat. I don't have a wattmeter and the one d8veh suggested isn't available at the mo - anyone have a spare one I could buy?

Edited January 17, 201214 yr by evendine

So, does the hub work with only 2 spur gears in the assembly?

 

In a nutshell.... yes.

 

Who knows for how long, but that's what experimentation's for.

 

There's a few single offset gear motors about, Heinzmann for example, but much depends on how the centre bearing survives the unbalanced thrust now.

 

I take it blowing the controller FET's is the main danger in increasing the current further - have been thinking of applying some thermal grease between their heat-sink and the controller case to help lose heat. I don't have a wattmeter and the one d8veh suggested isn't available at the mo - anyone have a spare one I could buy?

 

Mine ran at 20 amps OK. Fordulike's blew a hall sensor in the motor during a long uphill slog, but I think he was running at 36v. Not too much of a problem because you can change to a sensorless controller. The trick is not to let things get too hot. Use just as much power that you need and save the high power for short bursts. Don't go flat out all the time and don't be too greedy with amps from the controller.

Does it show what fets and caps are in the controllers?!?

I don't have a wattmeter and the one d8veh suggested isn't available at the mo - anyone have a spare one I could buy?

 

Don't know which one d8veh suggested, but some people fit these:

 

Turnigy Watt up Meter and power Analyzer UK seller | eBay

Not really - just a rough pic of the shunt...

Does it show what fets and caps are in the controllers?!?

In post #1 of this thread.

Rat with original graffiti paint job

 

http://www.notjustmetal.com/pics/TheRat.jpg

 

How about attaching an upgraded controller to the base of the current controller compartment with some heat-sink compound? Airflow / connection to the frame would help lose the heat and it would be a good location wiring-wise too; more space - easier access generally...

Ersatzzahnräder für Bafang 250W Motoren - ebike-solutions.de

Just found this: The 36 tooth one looks the same. You could ask them to check the O/D and I/D sizes, but I'll lay money on that being the one you need.

Ersatzzahnräder für Bafang 250W Motoren - ebike-solutions.de

Just found this: The 36 tooth one looks the same. You could ask them to check the O/D and I/D sizes, but I'll lay money on that being the one you need.

 

Nice find m8.

Have had the hub apart a few times in the last week, and it's a pain in the arse

Don't suppose you fancy doing the donkey work to find out the gear specs, do you?

Nice find m8.

Have had the hub apart a few times in the last week, and it's a pain in the arse

Don't suppose you fancy doing the donkey work to find out the gear specs, do you?

 

I notice that its got SWX written on the bearing. I think I've got a SWXU motor, so I'll open it up and see if its 36T. If it is, I'll measure it. Is your faulty one outside the motor? If so, could you get approx measurements to compare?

I notice that its got SWX written on the bearing. I think I've got a SWXU motor, so I'll open it up and see if its 36T. If it is, I'll measure it. Is your faulty one outside the motor? If so, could you get approx measurements to compare?

 

I destroyed the broken one, attempting to remove it from the spindle.

Counted the teeth on the piccy of the gear I posted, and it's 36T.

I'll be a monkey's uncle if that one on the German sight aint the same.

Hub's running fine at mo, but have bookmarked that site for future reference.

Shame the steel one isn't in a 36T

Nice bonus is that the shipping cost is about £16, no matter how much you order from them.