Thinking of converting my commuting bike - questions and advice

[pajtaz]

Hello,

I found this forum by doing some searching on the web about different types of e-bike conversion kits. I am thinking of converting my current bike which I use for work commuting in order to reduce my commuting time. That is my primary and pretty much only motivation. I have already done some research and I have focused on Tongsheng TSDZ2 but have some questions and looking for some advice.

Here are my details:

• I live in Netherlands so my commuting is basically all on flat ground and on dedicated bicycle lanes.
• I commute 18 km to work. My current average time is 45 minutes (faster with wind, slower against wind). This is around 23 km/h average.
• Converting would only be worth it if I can reduce commuting time to 30-33 minutes and it is less than 650 EUR for the conversion.
• I want to minimize changes to my bicycle so in case there are problems, I can return to original configuration without going to the bike shop.
• I have 2013 Kona Sutra (http://2013.konaworld.com/bike.cfm?content=sutra). It has Shimano Deore 11-32t 9 spd cassette, Shimano Deore front derailleur, Shimano LX trekking rear derailleur.

Because I want to minimize changes to my bicycle, I was leaning towards TSDZ2 (currently, after 5 years and regular maintenance, shifting is perfect, brakes are great, no adjustments were needed).

Some questions:

• I would definitely not select 42T front chain ring. I would lean towards the option with two chain rings. Can I use the existing front derailleur with this option?
• Can I use the existing rear derailleur?
• Can I use the same chain or does chain need to be changed?
• From experience, is it possible to achieve 33 km/h average with TSDZ2 and my type of a bicycle?

Advice:

• Based on above, which TSDZ2 would you recommend in terms of voltage, power, which battery, and which display?

I appreciate any help and advice from your community. Thank you in advance.

 

[vfr400]

A hub-motor would be much more suitable for your application. A 260 RPM one will get you top speed of around 34km/h and a cruising speed of about 30 km/h. For a cruising speed of 33 mph, you need 48v and a 328 rpm motor, which means running a 36v 260 rpm one at 48v or get a 48v 328 rpm one.

Most 36v cassette hub-motors are around 260 rpm, so the solution is to get whatever one you can and run it with a 48v battery and controller. I recommend a 15 amp KT sinewave controller from PSWpower.com with the LCD3 or the same from Topbikekit.com if you want the tiny LCD4. You can get the battery from wherever you want.

 

[Woosh]

you can use the TSDZ2, as you said, it's mostly flat roads so any kit will do.
I would recommend the XF08C rear hub kit though.
http://wooshbikes.co.uk/cart/#/product/uid-177-xf08c-17ah/xf08c-rear-hub-kit-with-17ah-battery

 

[KirstinS]

Flat roads, go hub for sure imho

 

[pajtaz]

Interesting that you are all suggesting hub motors.

However, then I am changing rear wheel, seems I have to change brake levers, maybe have to use throttle lever(?), move disc rotor from old to new wheel, none of which I want to do. Then can my existing cassette, chain, and derailleurs be used?

Woosh’s link says max speed is 15 mph so how do I allow higher speeds? I am aware of laws, I just want to understand how I can achieve higher than 25 km/h.

Then will everything fit? Plus I have a bicycle trailer hook on the rear axle. Will that fit with the hub motor?

 

[vfr400]

Fit a crank motor. It'll work OK, just not as nice as a hub motor.

 

[pajtaz]

I don't want a throttle, I just want to pedal and get assist when I need to go faster, like mid motor would do. Do I understand correctly that with the kit Woosh suggested, with torque sensor and without throttle, the hub motor would only assist me when I am pedaling? Do I still need to change brake levers or is it enough to just rely on the sensor? Also, this means I can keep using all of my gears as long as my cassette fits, correct?

If hub motor can do that without throttle and changing brake levers, I could accept changing the wheel to get reliability of hub motor and less stress on the drive train.

Woosh can you please answer above questions and explain how hub motor kit you suggested would work. And if possible, how could I then get higher than 25 km/h. Thanks.

 

[Woosh]

If hub motor can do that without throttle and changing brake levers, I could accept changing the wheel to get reliability of hub motor and less stress on the drive train.

the brake cutout switches are there just in case the throttle gets jammed.
If you don't fit a throttle, you don't need to install the brake cutouts, the installation can be quicker.
You can have a torque sensor if you refer:
http://wooshbikes.co.uk/cart/#/product/uid-223-xf08c-ts17ah/xf08c-ts-rear-hub-kit-26700c-with-17ah-battery

And if possible, how could I then get higher than 25 km/h

we of course do not wish our customers tamper with the speed limit setting which is in the LCD manuals.
Our hub motors are chosen to deliver the maximum power at 15mph, so when you go faster, the power tapers off, the hub motors have less chance to overheat.
Changing the speed setting in CD kits will void your guarantee because CD motors can overheat easily without showing signs of stress.

 

[pajtaz]

Thank you for the reply. Now it makes sense. With sensor I don't need throttle and brake cutout switches.

I would not want to replace my crankset so I am assuming I can just install a sensor, correct? I am not familiar with how torque sensor works and how it needs to be installed vs what other kind of sensors I could use. Can I use a speed sensor instead and use assist levels or if I want assist based on my pedaling I can only use a torque sensor? And if I have to use torque sensor, can I use existing crankset?

 

[Woosh]

I would not want to replace my crankset so I am assuming I can just install a sensor, correct?

the torque sensor is built into the bottom bracket, if you want to keep your crankset, you have to choose a cadence type pedal sensor.
The brake sensors are only needed if you have a throttle.

 

[pajtaz]

Can I buy and install my own torque sensor and use it with existing crankset? That would solve all of my problems and it is what I want. I understand cadence sensors are not so good for how I want to ride my bike (nice smooth pedal assist).

 

[Woosh]

Can I buy and install my own torque sensor and use it with existing crankset?

there are some models that can be fitted onto existing bottom brackets but not this one.

I understand cadence sensors are not so good for how I want to ride my bike (nice smooth pedal assist).

Almost all the controllers, including the Lishui controllers we use, deliver a power ramp up before sustain, and when you change assist level, so that you get a quick acceleration when you start from standstill. However, after the initial acceleration, the power delivery is smooth, with either cadence or torque sensors.

 

[pajtaz]

Ok, so cadence sensor would be an option too.

Thank you very much for all the information. It looks like best for me would be hub motor with decent rpm and battery, cadence sensor, 700c wheel. I guess I don't have to change my cassette, derailleurs, chain, and I need to transfer the disc rotor.

Now I need to do some research, save money, do measurements, etc. I appreciate all the help. Maybe I'll be in contact with Woosh in the future to buy a kit.

 

[Nealh]

BMSBattery sell a TS hub BB bracket kit to use with original cranks if sq tapered is used, it comes with a specific KT controller with software programmed for the TS.

Also there is a similar kit on Aliexpress where the vendor also sells replacement controllers.
With the TS kits you can't use a run of the mill controller for cadence sensors.

 

[pajtaz]

there are some models that can be fitted onto existing bottom brackets but not this one.

Almost all the controllers, including the Lishui controllers we use, deliver a power ramp up before sustain, and when you change assist level, so that you get a quick acceleration when you start from standstill. However, after the initial acceleration, the power delivery is smooth, with either cadence or torque sensors.

So I read a bit more and now I understand that because I have a hollow bottom bracket, I cannot use any torque sensors and would have to change the bottom bracket and the crankset (and I would need a hole for the torque sensor wire).

Knowing this, I would have to go for a cadence sensor. But one thing I don't understand is how does the cadence sensor work together with the hub motor and my level of pedaling.

1. Typically, how many assist levels are there and how do they correspond to the power that the motor will give?
2. Do different controllers have different ways of controlling using cadence sensors (more assist levels, more configuration options)?
3. How does pedaling work together with cadence sensor and motor? For example, if I am in a lower gear (pedaling is easier but I am going slower), does the motor provide same power as it would in a higher gear (pedaling is harder but I am going faster at the same pedal RPM)?
4. If it is providing the same power no matter what gear is being used, does it "add" to the power produced by my pedaling or does it reduce power as I pedal harder because that is what the controller will do?

What I am trying to achieve is that if I can currently pedal at max 26 km/h and I want to achieve 33 km/h, will the hub motor with cadence sensor help me get to that speed only if I pedal hard enough?

Woosh, can you help answer? And then can you suggest a kit from your shop where I would get hub motor + 700c wheel with cassette fitting (that can fit 32 wide tire like my Kona Sutra), cadence sensor, battery, and controller? The one you suggested before didn't have cadence sensor and had things I didn't want. Do you do custom kits?

 

[Benjahmin]

A cadence sensor detects the rotation of the peddles and turns the power on so long as they are rotating. A cadence hub kit will give the full power of whichever level setting you are in, regardless of how hard you peddle. So the energy you put in is added that of the motor, hence you go faster. All legally configured kits will cut off at 26kph leaving you to achieve 33kph by your own efforts.
Even 'derestricted' all motors have an rpm limit which is determined by magnetic saturation, which in turn is determined by the way they are wound.

 

[sjpt]

A cadence sensor detects the rotation of the peddles and turns the power on so long as they are rotating.

Exactly. The term 'cadence sensor' is generally misleading as it implies it depends on speed of pedalling. It would be possible to have such sensors, but almost all cadence sensors are just on/off switches.

(1) Typically 5 assist levels; (2) the level of flexibility does vary by controller. (3) Once you are pedalling at all, same power at a given assist level. One nice side-effect when you are feeling tired or lazy is that you can ghost-pedal quite slowly putting in virtually zero effort. (4) It adds to power you are putting in.

As Benjahmin has said, a legal kit will not assist over 25kph (maybe a fraction more because of error factors!); it will help you get to that speed but won't help above that speed. There should be no drag on a typical geared hub motor so it won't hinder other than just the weight of motor + battery.

A direct drive motor will actually hinder when you ride above the assist limit. Almost all direct drive motors are illegal because of power and max speed, and get through battery like mad as well.

 

[pajtaz]

Let me understand this. If I reach 25 km/h with motor and pedaling with cadence sensor, will the motor go off (not working any more) or will it continue to provide power? If it continues to provide power then if I continue pedaling in higher gear, will I be able to achieve over 25 km/h (motor working at max or whatever plus my pedaling)?

 

[sjpt]

In a legal pedalec setup the motor will turn off after 25km/h and will not provide any power; you are on your own above that speed. It should progressively reduce power near that speed so you don't get a sudden loss and resultant jerking in and out. It may well still provide a little just above that speed.

 

[vfr400]

When you buy a kit to convert a bike, the speed limit, at which point the motor switches off, in most cases can be set to whatever you want. If you set the speed to 15 mph, the motor will switch off and disengage at 15mph, allowing you to pedal on to whatever speed your leg power and external conditions will allow. That's the same whatever type of pedal sensor you have.

Most kits allow you to fit a throttle, which will control the motor without pedalling. It will work in conjunction with the pedal sensor and will take over control whenever you twist it.

Just to clarify. Cadence sensors do nothing other than detect when you're pedalling. They have nothing to do with how much power you get or how it's controlled. The controller does that.