Front wheel motor - pros and cons

[Grandad]

Thinking of fitting one on my Spa Audax

[Jdsk]

"crank vs hub power":
viewtopic.php?f=55&t=147858

Jonathan

[hemo]

Probably one of the easiest types of motor to fit barring a friction drive, too powerful and you will get will scrabbling in certain situations. Torque steering can catch a few unaware but above all try and opt for a current control system like the KT (Kuenteng) system.

[Grandad]

above all try and opt for a current control system like the KT (Kuenteng) system.

I'm currently riding an Orbea Gain and have no knowledge or experience of fitting an add-on motor. Is there a current control system in all add-on systems and if so can a different one be specified?

[hemo]

Which control system a bike manufacturer uses is down to them and their research.
Only by asking them which type of control system is used will you know that which is used.

When it comes to add on systems one can't specify to a manufacturer what to fit, only can this be done on a self build bike or one added by an independent LBS willing to do the job.

Cheap systems tend to use speed control which means usually a basic 3 power levels of speed, low, med, high. Each level has a max set speed of approx. 7mph, 11mph & 15.5mph whilst giving 100% current (amps) in each level. For some users find the control abrupt/harsh esp at low speed or setting off and is not to their liking.

Better user systems use current control and invariably have more power levels, each level one can obtain the max speed of 15.5mph but the difference is one can select the current (amps) for a far less abrupt/harsh start off and riding experince.

Any of these systems can use torque assist or cadence assist.

As regards to add on systems generally Bafang and Kuenteng (KT) are the two main players on the market that use current control, there is a cheaper china seller under the name of Brainpower but am not 100% sure if they use current control.
Lishui are another that use current control but are mainly an OEM supplier only but occasionally one does see there stuff on Aliexpress.

[hemo]

The mid drive main brands use torque assist as there pedal assist programme which is simply a torque multiplier that increases the amount of power the rider produces up to about 300%. These systems use current control type, as the power in each level gives more current, eco, tour, turbo etc, etc. Each level giving a different estimate of range possible thus eco being the least power/current provided attributing to the most range one can get out of the system, like any bike range is greater if power isn't used.

[Bonzo Banana]

Front hub motors have many benefits and many disadvantages.

You get the benefit of two wheel drive, your tyres wear more evenly, they work better for heavier riders as they provide more downward force. If you suffer more from rear punctures than front punctures they are better (again weight related). You can have whatever gearing you want on the back including hub gearing etc. You can swop out the front wheel more easily if you want to return it to a acoustic bike occasionally for longer rides etc. They can power through if one wheel slips due to the two wheel drive. They are simpler.

The negatives is if you have a powerful non-legal motor and are going up a steep hill you can lose traction. The steering is heavier especially if a direct drive hub motor.

Hub vs mid-drive.

Hub motor is independent of the normal drivetrain so it actually shares the load going up hills so it massively reduces wear on your chain, cassette and chainring. So they can last much, much longer or you can use lower end components and get good life out of them.

Hub motors are mechanically very simple and a good quality hub motor should be much more reliable than a good quality mid-drive motor. A direct drive hub motor has no moving parts at all except the bearings of the axle.

Whatever the output of the hub motor lets say 45Nm max, you get that in all gears if you want it so can be very punchy and strong even in high gearing.

Mid-drive motors are more efficient in that the power is delivered through the chain so it scales with the gears. So powerful in low gearing and little power in high gearing which is ideal for mountain biking, steep inclines etc. You do lose some power through the chain though like 2-3%.

Generally a front hub motor is a great option for a simple reliable ebike but it makes more sense the heavier the rider or load and only for legal ebikes.

Direct drive vs geared hub motors. Again the direct drive are stronger, heavier and less efficient, better for heavier riders etc where as geared more towards lighter riders. Swytch kit is a typical example of a geared front hub motor.

From the same manufacturer which offered both geared hubs and direct drive hubs the geared hubs were rated to 100kg and the direct drive were rated to 200kg. Also the maximum watts of the geared hub was 350W nominal/rated but the direct drive hub was rated from 250W-2500W (same hub but you would need a different controller).

[Grandad]

Thanks BB

From what you say the only disadvantage of a front wheel motor is if it is a powerful non-legal one, something I have no interest in.

The ability to revert back to a non motor bike rules out any thoughts of a hub drive.

[Grandad]

Which control system a bike manufacturer uses is down to them and their research.
Only by asking them which type of control system is used will you know that which is used.

I'm looking at the Cytronex motor and asked them if they used speed of current control. Their reply is

It’s a patented unique design which does the job of the three sensors other manufacturers have to use.

What is the third sensor that they are referring to?

[Jdsk]

It’s a patented unique design which does the job of the three sensors other manufacturers have to use.

What is the third sensor that they are referring to?

"The smartest element of the Cytronex kit is the sensor. Usually ebikes have up to three sensors: a crank sensor for cadence, speed sensor to limit speed and a brake sensor to cut the motor when stopping."
https://www.bikeradar.com/reviews/bikes ... c1-review/

Jonathan

[groberts]

Which control system a bike manufacturer uses is down to them and their research.
Only by asking them which type of control system is used will you know that which is used.

I'm looking at the Cytronex motor and asked them if they used speed of current control. Their reply is

It’s a patented unique design which does the job of the three sensors other manufacturers have to use.

What is the third sensor that they are referring to?

I'm considering a very similar set-up as you - front wheel motor + Cytronex on a Dawes Audax - so would be very interested to hear what the outcome of your deliberations & (hopefully) conversion?

[stodd]

The three usual sensors they mention for a regular ebike are pedal sensor (at the crank), speed sensor (on the wheel, just like any non e-bike cycle 'computer') and brake sensor. Torque sensor systems usually don't have the brake sensor.

I think this is their (US) patent:
https://patentimages.storage.googleapis ... 272751.pdf
Assigned to Modern Times Ltd, which is Cytronex.
I can't see a link to the original UK patent GB2501496B, which appears to be expired anyway. The US patent is still active.

This is based around a gear rotation sensor. If this is at the rear gears it detects speed if the bike is being driven, but also detects not pedalling as the bike will then freewheel and the rear gears will not be rotating. As it is effectively equivalent to a max-teeth (eg around 30) magnet pedal sensor it should be more responsive to starting pedalling, and in particular to stopping pedalling, hence reducing (eliminating?) the need for a brake sensor.

It looks as if the gear tooth sensor is usually itself two sensors to help determine direction of rotation (claim 5).

This should be enough to ensure the bike is not powered past 15mph (or whatever cutoff is chosen), but not enough to give a sensible speed reading when eg freewheeling downhill.

[Richard Fairhurst]

You might also have a fourth sensor (Mrs F's newly converted mid-drive e-bike does) - a gear change sensor. This drops the power temporarily when it detects that you're changing gear. End result is that the chain is less likely to come off!

[Oldjohnw]

My motor momentarily switches of when changing gears. You rarely notice.

[hemo]

Most modern good hubs will already have an internal speed sensor so that leaves only two, a good controller system can negate having to fit brake sensor's so that leaves just one sensor and that is a pedal/PAS sensor.
With the KT controller's a brake sensor is only needed in the case of having a throttle fitted.