Self-build bike nearing completion..couple of questions

[morphix]

Hi all,

I have not been posting to the forum since before Christmas, so best wishes to everyone and hope you're all well.

Some of you may remember my posts last year reviewing a Chinese Wisper clone which I subsequently returned (too heavy, under-powered and over-priced). I had planned to do a self-build instead and was on the look out for a suitable folding bike but decided to put my plans on hold until the new year.

Fast forward a couple of months...I finally found a suitable folding bike which is a full-size MTB with 26" wheels. I bought a conversion kit (250W 36v) and finally got around to installing it over the last 2 weeks. I opted for a front-wheel drive and 5Ahr power source, which I'm installing behind the seat. I tried a handlebar bag setup but felt there was too much weight which would affect steering..decided it would be better distributed if the battery and controller were further back. I want to keep the rack free and keep the bike looking as inconspicuous as possible, so mounting the power+controller behind the saddle/seat post seemed the logical place.

Anywaay.. no major problems so far. Still a few more things to do before I can take it out for a test ride. I've also met a few little challenges I have to work out which I'm hoping someone will be able to help me with.

The bike itself had some nice neat torque washers on the front fork which I was hoping to use (assuming they would be suitable - the motor is 2.5kg). Of course, they wouldn't fit though over the wider motor axle. Does anyone know where I might find some washers of a similar design that might fit? I don't even know what this type of washer is called, so don't even know what to search for.

Second challenge I've had is with fitting the torque sensor. The conversion kit I have has German instructions which even when translated are a bitch to fathom. There seems to be three different ways to install the sensor: left or right side of crank, or rear wheel. Installing on the crank opposite side to chainset seems the most logical and least challenging. Does that sound ok? If anyone knows a good howto or has an english installation guide for installing a torque sensor I'd appreciate it.

Finaally, my last questions relate to battery charging.. I purchased from the same China source on eBay as OldTimer (perhaps if he is around or anyone else who purchased from same source, you could shed some light on this).

The batteries I received came with no instructions whatsoever which is a bit worrying as I have no idea how long to charge them for, and whether it's safe to leave them on charge longer than the recommended charge time (whatever that is!). I'm assuming the charger or BMS simply cuts out when the battery is fully-charged? But you can't be too careful with stuff from China. I asked the seller, but his English is very poor and he basically told me to charge them until the LED changes to green on charger, then leave it another 1-2 hours..well it took 1 hour for the LED to change to green. It then alternates between green and red for hours..I left the battery on for 3 hours (4 hours total) and the LED was still alternating..the battery itself wasn't even warm. I assumed it would of been? These are 36V 5Ahr batteries.

Thanks for your help guys, I will post some pics up shortly when I'm done with the rest of the assembly work.

Morphix

 

[Biged]

Can't you file the washers to fit the axles? (i suppose 23 years in engineering helps)
Most large batteries don't get warm unless there is a high charging current, bike batteries tend to get more of a trickle charge (better for the battery as well)

 

[Deleted member 4366]

Can we see a picture of the torque sensor?

 

[morphix]

Can't you file the washers to fit the axles? (i suppose 23 years in engineering helps)
Most large batteries don't get warm unless there is a high charging current, bike batteries tend to get more of a trickle charge (better for the battery as well)

I was thinking the same earlier, maybe drilling out instead of filing.. will have to see if it's feasible. Thanks for the suggestion and info about the battery Biged.

 

[morphix]

Can we see a picture of the torque sensor?

Oops should of uploaded that earlier, just updated it with a pic :-}

 

[morphix]

Can't you file the washers to fit the axles? (i suppose 23 years in engineering helps)
Most large batteries don't get warm unless there is a high charging current, bike batteries tend to get more of a trickle charge (better for the battery as well)

I just had a look again at the washer and axle, and it looks like its only a mm too small..so maybe filing is the best way.

 

[NRG]

That's a pedelec sensor not a torque sensor. You can fit it either side of the BB but you will need to play around with the orientation of the magnetic disk. Get it wrong and it may operate in reverse.

You can see the direction arrow on the disk it but it depends on the type of sensor (the other bit) as to which way 'round it goes on the axle.

 

[morphix]

That's a pedelec sensor not a torque sensor. You can fit it either side of the BB but you will need to play around with the orientation of the magnetic disk. Get it wrong and it may operate in reverse.

Ah thanks for that. Will have a go at getting it installed tomorrow when my crank puller arrives hopefully.

 

[morphix]

That's a pedelec sensor not a torque sensor. You can fit it either side of the BB but you will need to play around with the orientation of the magnetic disk. Get it wrong and it may operate in reverse.

You can see the direction arrow on the disk it but it depends on the type of sensor (the other bit) as to which way 'round it goes on the crank.

Am I right in thinking that this sensor is used in establishing the normal 15mph speed restriction in the controller? I.e. when you pedal above a certain rpm the motor cuts out? Or is that normally done by monitoring the motor itself?

There's three wires from the sensor, one is for speed signal, the other are +5v and ground. On the wiring diagram I have it shows a fourth wire for torque signal which is obviously missing.

 

[onmebike]

I have the 10ah version of your battery. In the final stages of charging the led's will alternate between red and green until battery is fully charged, when it should remain green. I believe this occurs while cell balancing takes place.
The pedelec sensor simply detects the pedals are being turned and adds assistance this can usually be over ridden by a throttle control where fitted.
The speed is restricted by the motor/controller as far as I'm aware.

 

[jerrysimon]

I just had a look again at the washer and axle, and it looks like its only a mm too small..so maybe filing is the best way.

Yep usually you have to take a mm or so off the fork drop out width just to get the motor shaft in, or at least scrape the paint off.

Many motors (the Tongxins anyway) come with little torque washers but then you usually still have to file the dropout even deeper, so the torque washer will fit and the lug locate in the hole as I did below. See this thread for details

Regards

Jerry

 

[NRG]

Am I right in thinking that this sensor is used in establishing the normal 15mph speed restriction in the controller? I.e. when you pedal above a certain rpm the motor cuts out? Or is that normally done by monitoring the motor itself?

There's three wires from the sensor, one is for speed signal, the other are +5v and ground. On the wiring diagram I have it shows a fourth wire for torque signal which is obviously missing.

The rotating sensor inputs a series of pulses to the controller. The controller interprets these and spins the motor up to it's maximum speed. Above it's max speed the pulses are still being interpreted by the controller but the motor cannot be driven any faster as we are now limited by the maximum battery voltage. The motor generates a back EMF (voltage) as it rotates, as it spins faster this BEMF increases until it equals the battery voltage and the motor won't spin any faster.

Now there may be some control of the motor speed via pedal cadence but it depends on the controller. IE pedal slowly will slow the series of pulses and the controller may limit motor speed. In practice the cheap controllers don't work that well in this respect on the pedal sensor is more like an on/off switch.

 

[morphix]

Jerry, I forgot to ask..are those little torque washers sufficient then to manage the torque from 250 36v motor on a 26" wheel in your opinion? I've seen other posts recommending more substantial torque arms and brackets but I think they look unsightly and would prefer the washers.

 

[morphix]

The rotating sensor inputs a series of pulses to the controller. The controller interprets these and spins the motor up to it's maximum speed. Above it's max speed the pulses are still being interpreted by the controller but the motor cannot be driven any faster as we are now limited by the maximum battery voltage. The motor generates a back EMF (voltage) as it rotates, as it spins faster this BEMF increases until it equals the battery voltage and the motor won't spin any faster.

Now there may be some control of the motor speed via pedal cadence but it depends on the controller. IE pedal slowly will slow the series of pulses and the controller may limit motor speed. In practice the cheap controllers don't work that well in this respect on the pedal sensor is more like an on/off switch.

Interesting, so I guess it varies a bit depending on the controller.. I will have to carry out some tests and see if this controller is any good then report back.

 

[morphix]

Quick update

I've finished the wiring this evening after installing the battery and controller onto the bike...found the wiring a bit confusing at first as I had to work from a diagram which had some variations in colours. I also had to fit an IEC power connector to the controller power leads to fit the battery which I bought separately from the kit.

Anyway, powered it up and was surprised but it all worked first time! A twist of the throttle and the motor whirred into action. I've installed an LCD for the controller which has a speedometer...with the front wheel up off the ground and the throttle fully open it was reading 32km/h, which is about 20mph.

I was tempted to take it out for a quick spin around the block but have decided to wait until it's completely finished. I still have to fit the pedal sensor but I'm waiting on a crank puller before I can tackle that. Should be able to have it out tomorrow or the weekend and I will post some pics of the build and finished bike then.

 

[theskip1]

Hi all,

I have not been posting to the forum since before Christmas, so best wishes to everyone and hope you're all well.

Some of you may remember my posts last year reviewing a Chinese Wisper clone which I subsequently returned (too heavy, under-powered and over-priced). I had planned to do a self-build instead and was on the look out for a suitable folding bike but decided to put my plans on hold until the new year.

Fast forward a couple of months...I finally found a suitable folding bike which is a full-size MTB with 26" wheels. I bought a conversion kit (250W 36v) and finally got around to installing it over the last 2 weeks. I opted for a front-wheel drive and 5Ahr power source, which I'm installing behind the seat. I tried a handlebar bag setup but felt there was too much weight which would affect steering..decided it would be better distributed if the battery and controller were further back. I want to keep the rack free and keep the bike looking as inconspicuous as possible, so mounting the power+controller behind the saddle/seat post seemed the logical place.

Anywaay.. no major problems so far. Still a few more things to do before I can take it out for a test ride. I've also met a few little challenges I have to work out which I'm hoping someone will be able to help me with.

The bike itself had some nice neat torque washers on the front fork which I was hoping to use (assuming they would be suitable - the motor is 2.5kg). Of course, they wouldn't fit though over the wider motor axle. Does anyone know where I might find some washers of a similar design that might fit? I don't even know what this type of washer is called, so don't even know what to search for.

Second challenge I've had is with fitting the torque sensor. The conversion kit I have has German instructions which even when translated are a bitch to fathom. There seems to be three different ways to install the sensor: left or right side of crank, or rear wheel. Installing on the crank opposite side to chainset seems the most logical and least challenging. Does that sound ok? If anyone knows a good howto or has an english installation guide for installing a torque sensor I'd appreciate it.

Finaally, my last questions relate to battery charging.. I purchased from the same China source on eBay as OldTimer (perhaps if he is around or anyone else who purchased from same source, you could shed some light on this).

The batteries I received came with no instructions whatsoever which is a bit worrying as I have no idea how long to charge them for, and whether it's safe to leave them on charge longer than the recommended charge time (whatever that is!). I'm assuming the charger or BMS simply cuts out when the battery is fully-charged? But you can't be too careful with stuff from China. I asked the seller, but his English is very poor and he basically told me to charge them until the LED changes to green on charger, then leave it another 1-2 hours..well it took 1 hour for the LED to change to green. It then alternates between green and red for hours..I left the battery on for 3 hours (4 hours total) and the LED was still alternating..the battery itself wasn't even warm. I assumed it would of been? These are 36V 5Ahr batteries.

Thanks for your help guys, I will post some pics up shortly when I'm done with the rest of the assembly work.

Morphix

this is the bms balancing the cells. you will just have to be paitient on the first charge. i have heard of batteries taking up to three days to balance out.

 

[jerrysimon]

Jerry, I forgot to ask..are those little torque washers sufficient then to manage the torque from 250 36v motor on a 26" wheel in your opinion? I've seen other posts recommending more substantial torque arms and brackets but I think they look unsightly and would prefer the washers.

I would have to err on the side of caution if advising you and say yes a torque arm is preferable/a belt and braces solution. The Tongxin motor above is not over powerfull and the torque washers seem sufficient for the Brompton.

On the Alien kit I got although I think it had torque washers with it (maybe not I can't remember) unlike your bike the dropouts on mine did not have the little holes in the ends, so I could not fit them. The torque arm doesn't have to be huge and shown below is a small one, I had made in place of the torque washers. In many ways its not much more than a large torque washer and considering you would have torque washers both sides you will probably be fine. Fitting the torque washers is definately better than nothing but in my case I could not, so had to fit a seperate torque arm. The good thing is you can at least fit one either side and it will "probably" be ok.

Details here

Regards

Jerry

 

[GT3]

Jerry, I forgot to ask..are those little torque washers sufficient then to manage the torque from 250 36v motor on a 26" wheel in your opinion? I've seen other posts recommending more substantial torque arms and brackets but I think they look unsightly and would prefer the washers.

Depends upon your frame material. My similar motor is a snug fit into the cutouts of a steel frame and I'm happy without washers. If the fit is less good, or the forks are ally, then I would consider washers. No need for torque arms at 250W unless your frame is made of cheese IME.

 

[jerrysimon]

GT3 raises a good point if your forks are not steel then almost certainly you would need to fit a torque arm. A simple test with a magnet will confirm that

Regards

Jerry

 

[morphix]

I have the 10ah version of your battery. In the final stages of charging the led's will alternate between red and green until battery is fully charged, when it should remain green. I believe this occurs while cell balancing takes place.
The pedelec sensor simply detects the pedals are being turned and adds assistance this can usually be over ridden by a throttle control where fitted.
The speed is restricted by the motor/controller as far as I'm aware.

Many thanks for the info the battery charger had me puzzled..how long does it take normally for yours to reach full charge once it starts alternating? The charger is a bit of a brick isn't it!?

Do you know if it's safe to leave the battery on for longer once the LED is permanently green?