Which Side (Left or Right) And Distance Between PAS Sensor And Magnet Disc?

[OldManTomahawk]

Fixing to install PAS and need to know which side it mounts on and the distance between magnet disc and sensor.  How are folks securing senor part to bike/trike?  The instructions say, 'washers or super glue', which seems 'iffy' to me if the distance between the two parts are critical. Thanks for the help/suggestions!

[Bikemad]

I have recently been testing my pedelec sensor that came with my MP Edge and it works fine on either side as long as the arrows on the magnet ring are pointing in the forward direction of the pedal rotation. The spacing does not seem to be as critical as the pedelec sensor I had on my original Magic Pie, as during testing, it still worked with almost a 5mm gap between the sensor and the magnet ring, but I still like to fit them as close as possible without actually touching. 

I like to sandwich the sensor mounting bracket securely between the bottom bracket locking ring and the frame:





If your bottom bracket bearing assembly doesn't have the old style locking ring style of bearing adjustment, then glueing the mounting bracket to the frame might be the easiest option.

Alan
 

[OldManTomahawk]

I don't have the cylinder style sensor, mine is a rectangle.  There is a symbol in the center which I guess is an alignment mark.  As I'm going to have to glue the bracket to the frame I need to get it correct the first time!  My frame will not let the bracket center correctly as the bend in the bracket is too shallow.  I'm thinking I can put the sensor on the other side of the bracket, do you agree? Thanks, Topm

[Bikemad]

Tom, when you say "put the sensor on the other side of the bracket", do you mean on the chainwheel side like this:



There appears to be about 7mm of clearance between the mounting hole and the sensor body:


 
As long as the outside diameter of your frame's bottom bracket is less than 48mm, you might be able to file (or grind) away the portion of the bracket that is preventing the bracket from seating correctly on the frame, as indicated in red below:



If you are reasonably good working with metal (and have access to a hammer and decent vice) it might be possible to remove the sensor from the bracket, flatten the bracket out, scribe a line along the outer edge of the sensor and the outside diameter of the bottom bracket and then rebend it just outside the lines with a much tighter angle which should then fit perfectly.

If you are not overly fussy about your frame, you should be able to radius the edge of the bottom bracket with a file to accommodate the bend in the bracket. if the sensor is mounted below the bottom of the frame, the filed edge would not be seen. 

I don't know whether the magnets are supposed to pass along the centre of the sensor, but I have also shown where the magnets are positioned in relation to my sensor.

Alan
 

[OldManTomahawk]

Hey Alan, No, I'm not talking about the chain wheel side.  The picture with the ruler looks like the bends in the metal move the sensor away from the bike frame?  My sensor in mounted where the cable is toward the back and is under the bend above the large round hole, and I think you show the cable toward the front with the bend on the back side?  Can the sensor be mounted on either side of the metal part of the sensor? If that is correct then my problem goes away?  Is the reason for mounting the magnet wheel so the arrows turn forward so it moves across the sensor in that direction or is it to insure the serrated plastic teeth hold on the shaft?  Sorry for my confusion!! I just want to do it correctly, the first time! Maybe I should just have ask, can the sensor be attached to either side of the bracket using the existing holes?  Thanks, Tom

[Bikemad]

The picture with the ruler looks like the bends in the metal move the sensor away from the bike frame?  My sensor in mounted where the cable is toward the back and is under the bend above the large round hole, and I think you show the cable toward the front with the bend on the back side?

On both of my sensors, the metal bracket moves the sensor back towards the centre line of the frame and further away from the magnet ring, but the different style of sensors are mounted on different sides of the bracket:





From your description, it sounds like your sensor is similar to this one:



If the bracket can be rotated and the sensor still fixes in the same orientation (without having to physically invert it) then it might work, provided there is still enough room between the sensor and the crank for the magnet ring to fit without rubbing against the sensor.

The direction arrows on the magnet ring are basically there to ensure that the magnets move across the sensor in the correct direction, otherwise the pedelec might not work unless you pedal backwards.

Alan
 

[OldManTomahawk]

Yep! I was afraid that would be the answer.  I'll try to modify the bracket or the bike (trike) frame to get the room I need to center the bracket.  Thanks for your help!!  Have you talked with (or emailed) a guy in Wichita Falls, TX? Saw him this morning and he had nothing but good to say about his set-up.  Wish I had gotten his name, older gentleman with a Schwinn Trike and GM he has had for about 4 years he said. Tom