Attempt to alter pedelec assist action (NRG take note)

[Old Timer]

You might remember a thread a while ago where I was discussing the way in which the pedelec works on the alien kit with mainly NRG. The fact that the assistance tends to favour a faster cadence has always been a sore point with me because mainly I need and want help more when my pedals are turning slow rather than when I have the bike going along at a good pace. I understand why some members prefer when they get to a hill to drop a gear and in comes more assistance and thats fine but i ride in an area where although there are some low gear hills a lot of the terrain is flat or gradual hills where I want to stay in a higher gear and still get assistance.

So! Onmebike(tony) and I have been discussing it and decided that to increase the amount of small magnets in the pedelec ring might fool the system into thinking that the pedals were turning faster and thus bring in the power earlier. The original ring has 5 magnets evenly spaced.
First attempt taking a pedelec ring that had 6 magnets as standard and 6 empty holes in between them was a failure when I fitted another 6 magnets into the holes(giving 12 total) Just totally confused things. so we took a more gentle approach and fitted a new ring that just had 6 magnets instead of the standard 5. Road test proved to be an improvement and now when cruising in 5th gear(out of 6) on the flat and the cadence gets a bit lively with an indicated 18mph I changed up to 6th gear and the motor tone did not change and the assistance was still there enough to maintain the same speed Not an earth shattering difference but enough to notice instead of before where top gear saw not much assistance and was forced to drop down a gear again. When pulling away in a fairly high gear now after about half a turn of the crank the assistance is noticeable from before.
We reckon (now that I have a decent selection of these small magnets) it might be worth making up a disk with 7 or 8 holes for magnets, they have to be evenly spaced of course but those extras might improve even further.

Just thought I`d share what I`ve been doing on a wet and dreary day.

Dave

BTW the top gear on this Evans conversion is a 13t rear 48T front

 

[Morag]

Firstly I'd like to say I actually understood what you said which is amazing for me, good explanation. Secondly congrats on getting results going in the right direction, onward and upward.

 

[Andy_82]

great job Old Timer,

it is interesting what say. I personally prefer to run on the higher cadence but I know many other don't. I read that Yamaha crank drive works quite well on the lower cadence.

Can I ask you what happened when you fitted 12 magnets? Why it didn't work too well? It actually should as it should be misleading to the sensor that you actually run on the lower cadence.

Anyway it is interesting to see that you did your own piece of research as I think we really can call it this way

 

[Old Timer]

great job Old Timer,

it is interesting what say. I personally prefer to run on the higher cadence but I know many other don't. I read that Yamaha crank drive works quite well on the lower cadence.

Can I ask you what happened when you fitted 12 magnets? Why it didn't work too well? It actually should as it should be misleading to the sensor that you actually run on the lower cadence.

Anyway it is interesting to see that you did your own piece of research as I think we really can call it this way

Other than the test ride the test was carried out with the bike suspended from the beams in the shed to get both wheels off of the ground so that I could turn the pedals slow and monitor the speedo.

With 12 magnets in place the wheel started up OK till the pedal speed increased and then the controller was jumping from off and on.
I must admit that I don`t actually know what is inside the other part of the pedelec (the sensor with the three wires) Is it perhaps like an alarm contact with a small metal switch affair in a glass tube where the magnet pulls the switch backwards and forwards making and breaking contact??
I reckon with 12 magnets the gap was too small so the switch mech didn`t have time to reset perhaps?

BTW I was careful to make sure the north and south poles of the magnets that I added were in the same config as the originals just in case there was a magnet in the sensor.


What we are trying to ascertain is whether when changing up to top gear at a fairly high speed the effect of the pedelec is being affected by the 15mph(or there abouts) cut of from the motor. The strange thing is that if things were being affected by the 15mph cut off then why when I turn the throttle does the motor kick in regardless of that speed and take the bike up to at least 20mph on the flat? Obviously the pedelc control is separate from the throttle control.

Anyone that can throw any more info in then please feel free.

Dave

 

[Old Timer]

Firstly I'd like to say I actually understood what you said which is amazing for me, good explanation. Secondly congrats on getting results going in the right direction, onward and upward.

Thanks Meg, I`ll get you in that shed yet My wife calls me the mad professor sometimes.

 

[Phil_P]

Hi ,

Interesting info dave thanks for sharing....

On a similar subject does anyone know if it is possible to fit some kind of device that would allow you to incrementally adjust the amount of assistance ? - Something offering a little more control than an on/off swith !

I know some models come with this feature like an economy mode / sport mode etc.

Thanks
Phil

 

[flecc]

I must admit that I don`t actually know what is inside the other part of the pedelec (the sensor with the three wires) Is it perhaps like an alarm contact with a small metal switch affair in a glass tube where the magnet pulls the switch backwards and forwards making and breaking contact??
I reckon with 12 magnets the gap was too small so the switch mech didn`t have time to reset perhaps?

Dave

It's a Hall sensor Dave, a transistor like device that senses the presence of a magnetic field and sends pulse signals to the controller. There's probably some lag in dropping to off again, so 12 magnet frequency probably didn't give enough time.

Hall sensors are also used in our throttles, the gradual transfer of a magnetic field past one enabling the sensor to send an increasing 0 to 5 volts signal to the controller for setting the power level,

Hall was the chap who first discovered the usefulness of magnetic fields for such uses.
.

 

[NRG]

Glad to read you found a solution Dave

, as you know I'm probably going to remove some magnets as I find the assistance at low cadence a little bit on/off. The ramp from some assistance to full on assistance occurs over a very narrow cadence range and the bike is therefore difficult to control at low speed / low cadence in pedelec mode. Removing some magnets I think will be the solution for me....I'm more than happy with the top end assistance as I tend to either put effort in to raise the cadence and thus keep the assistance on or simply open the throttle...Its just a different riding style that works for me.

 

[Old Timer]

It's a Hall sensor Dave, a transistor like device that senses the presence of a magnetic field and sends pulse signals to the controller. There's probably some lag in dropping to off again, so 12 magnet frequency probably didn't give enough time.

Hall sensors are also used in our throttles, the gradual transfer of a magnetic field past one enabling the sensor to send an increasing 0 to 5 volts signal to the controller for setting the power level,

Hall was the chap who first discovered the usefulness of magnetic fields for such uses.
.

Thanks Tony

To be honest I`m ready to make up a new disk using perspex or similar and I make you right about the 12 magnets being too many. Six is working fine and maybe eight will work but i wonder if the difference would be enough to warrant the time involved? The magnetic force of these small magnets is quite strong so I can see how too many would overlap.

 

[Paulius55]

I still prefer the higher cadence = more assistance of the standard set-up as it seems logical to me, as I treat my bike as a normal bike that gives assistance to me, rather than an electric bike that I give assistance to. For that reason I use the "throttle" hardly at all and wouldn't miss it if it was not there. As I said in an earlier post, by the time I am in top gear the bike is going 15 mph + and assistance is irrelevant. Besides, if I want to go faster than that on 2 wheels I just get on my BMW F800ST!

 

[Old Timer]

I still prefer the higher cadence = more assistance of the standard set-up as it seems logical to me, as I treat my bike as a normal bike that gives assistance to me, rather than an electric bike that I give assistance to. For that reason I use the "throttle" hardly at all and wouldn't miss it if it was not there. As I said in an earlier post, by the time I am in top gear the bike is going 15 mph + and assistance is irrelevant. Besides, if I want to go faster than that on 2 wheels I just get on my BMW F800ST!

That`s fine and each to his/her own but it does seem odd that it works the other way to most other e bikes. To be honest (not sure what your age is) if that`s the way you ride then you really almost don`t need any assistance. I`m 65 now and when I go out i want nourishment not punishment now

Take Care

Dave