PAS Setup on Single-Piece Crank Possible?

[Reggie Curry]

Hello out there. So, I'm trying to get some kind of PAS setup done here with my cruiser bike, but I canNOT, for the life of me, figure out how I'm gonna make this work as far as mounting everything goes. The actual function works because I held the disc in my hand and moved both sensor types (the ring style that came with my ebike kit) and the split PAS kit that I bought from Amazon 2 days ago and tried them out, and the bike actually moved forward an inch by itself. I thought that maybe I could drill out space within the center of the split version and just slide it over my crank arm (because it was originally too tight to fit anywhere near the frame) so that I can mount it because, as you can see, I have a single-piece crank and not a two-piece version and try to do to set up that way, but it doesn't seem like the disc ever stays on what bit of threads that it's able to sit on. I would try the original disc, but it's already too small to fit in any way, which is why I bought the split version to see if I could just snap through two pieces together without having to modify anything, which obviously didn't work like I thought it would, so that's one issue.

The other issue is that the one time that I actually had it sitting there and then mounted the sensor itself, it acted like it never wanted to activate when I'm pedaling regardless of how I mounted it, whether it's super close to the magnets or just a bit away from them after zip-tying the thing in multiple ways. The red light will turn on but never do anything; only when I intentionally moved the sensor against the magnets does it actually bother to make the PAS kick in a little bit. The sensor ring that came with my ebike kit works much more consistently than the one that I kept trying to work with first, but again, I run into mounting issues with it because I don't know how you would mount that on a single-piece crank.

Of course, yes, it would be simple to just swap out the crank to a two-piece and save myself the headache of trying to make this work with what I've got, but I have no experience with taking this apart so I don't feel comfortable doing the job on my own, and my local bike shop is the only one around for several miles that can do it but charges a good bit for labor work, and I don't quite have a lot of money to spend to let them do it.

So, to simply ask the following: Is it even possible at all to use either set to have a mountable PAS setup, or will I have no choice but to swap out the crank set?

NOTE: The information on the split version that I got strictly mentions that it's for the left side, so I know for a fact that this isn't the case of me trying to mount everything on the wrong side of the bike.

 

[fill]

You have the two sensors that would have worked with my kit but mine arrived with a 3rd type that was a pita.

Anyway have you considered fixing the magnet disk to the hub of either of your wheels and cable tieing the pick up sensor to the fork leg or rear wheel arm (dunno the correct term) .

Afaik the pas (magnet ring) just needs to rotate in the correct direction when you want to move, it may take a bit longer for the pedal assist to kick in as the wheel will rotate slower than your crank but that should be simple to accommodate and get used to. .

when fitting the 2nd sensor i got, same as the one with the sensor attached to the metal bracket in your pic, I had the magnet disk facing the wrong way round, and Nothing, flipping it to face in the other direction fixed it.. and that sensor seems to require very close proximity with the magnet ring to work?

the other sensor you have (split ring) may work on the crank ok if your ok using epoxy to secure it to the crank

flipping the disk to face in the opposite direction is also a fix for using a right side sensor on the left and visa versa

Im probably wrong but i suspect your problem with the sensor not working when fitted but working when manually activated may be a wrong way round issue?? if not its most odd.

edit btw i had to coax my magnet ring onto my crank with a big mallet!! using a large socket to wallop it home.. without the hammer action the chain-ring wouldnt fit back on and the securing screw couldnt engage. and then i had to pull it all off again and flip the bloody disk, they are quite resilient.

 

[E-HP]

Anyway have you considered fixing the magnet disk to the hub of either of your wheels and cable tieing the pick up sensor to the fork leg or rear wheel arm (dunno the correct term) .

Afaik the pas (magnet ring) just needs to rotate in the correct direction when you want to move, it may take a bit longer for the pedal assist to kick in as the wheel will rotate slower than your crank but that should be simple to accommodate and get used to. .

So this would be like cruise control with the only way to stop the bike is to rely on brake cutoffs or turning off the controller? Sounds dangerous.

 

[E-HP]

Of course, yes, it would be simple to just swap out the crank to a two-piece and save myself the headache of trying to make this work with what I've got, but I have no experience with taking this apart so I don't feel comfortable doing the job on my own, and my local bike shop is the only one around for several miles that can do it but charges a good bit for labor work, and I don't quite have a lot of money to spend to let them do it.

So, to simply ask the following: Is it even possible at all to use either set to have a mountable PAS setup, or will I have no choice but to swap out the crank set?

Swapping to a two piece crank isn't so easy, and still may not solve the problem. There are several solutions/posts on the forum if you use the search tool

Installing PAS sensor on one-piece cranks - looking for ideas

I am installing a PAS sensor on the cranks of a steel-frame Huffy cruiser. What creative workarounds have y'all come up with? Or is there an off the shelf model for the big bottom brackets? Any tips or photos would be appreciated.

endless-sphere.com

 

[docw009]

I have mounted the magnet disk to the crank. STill had to fab a bracket to hold the sensor next to it. but it works. Have to make sure you have a PAS that works with the disk on the outside, and turning in same direction as wheels, In the worst case, you cut the disk into sections of magets and glue them symmetrically to the chain gear, and realign the sensor to the new magnet position,

 

[amberwolf]

I'd use the split magnet ring, and then use the sensor that actually works. The magnet rings are almost certainly identically magnetized and should then do the same job, but the sensors have several possible output methods, and the one you got might not be compatible with the kit (while the one with the kit ought to work).

Distance usually has to be somewhere around 5-10mm away from the magnets, and there may be arrows on the magnet ring to ensure you ahve it rotating in the forward direction.

The sensor has to be parallel with the magnets at the right distance and angle, it should also have a marking on it to show where the magnets should line up with it.

You might have to modify it's mounting bracket (or make your own) that will secure it properly to the frame and still leave it in the correct location for reading the magnets.


If you cannot make any of the magnet rings fit you could simply mark all the magnets so you can tell what orientation they had in the ring and which side is which, and pop them out and then just stick them on your chainring in the right circle to line up wiht wherever the sensor best fits. If the chainring is steel (usually is for Ashtabula / OPCs) then you dont' usually even have to glue them down (but you can).


Note that you also have to be in the right mode on the display for PAS to actually do anything (usually mode zero doesn't respond to any input, for instance, and you may also ahve a throttle-only mode, and a walk mode).