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

Posted: Apr 16 2018 1:25pm
by Scoot440
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.

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

Posted: Apr 16 2018 1:34pm
by teklektik
Grin Tech PAS_12P, PAS_12P_Chr have basic physical designs that will probably address your needs.

However, both these particular products have been customized to only work with a Cycle Analyst 3. If you are not interested in a CA3, you can likely get the original unmodified versions from other vendors - these are King Meter parts (possibly the T-281 http://www.kingmeters.com/project/t-281-sensor/).

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

Posted: Apr 16 2018 3:16pm
by Scoot440
Thanks! The larger magnet disc on the PAS 12P Chr may be just the thing. I'll do a little more digging.

http://www.ebikes.ca/catalog/product/ga ... 42/id/351/

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

Posted: Apr 17 2018 9:48am
by Scoot440
Second question: Is there any reason I should not harvest the magnets from my existing magnet disc and make a larger disc?

A disc with a 3.5" diameter should accommodate the larger bottom bracket.

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

Posted: Apr 17 2018 10:35am
by teklektik
No problem at all.
You can even stick them to the inner chain ring (or the bolts/arms if there are any on your rig) using epoxy or even just magnetically. The grade 52 magnets are quite fierce and will hold in place with great tenacity if your harvested magnets don't stay in place (see; https://www.kjmagnetics.com/products.asp?cat=1).

The effective diameter of placement doesn't matter, but get the polarity right. Mark them with a Sharpie or similar before punching them out. If your sensor has a LED indicator, then when you're done with your new wheel, wave the sensor by each magnet in the direction of crank rotation and verify that each magnet is installed correctly.

The big thing here is the number of magnets since that determines the angle of rotation before the electronics gets some notion of what is going on - either starting or stopping. More magnets = better response. In the good old days, some wheels only had only 5 magnets, now you can get sensors with 24 poles (!). That said, even 5 magnet wheels work - only the start and stop are affected. The only caveat here is if this sensor is part of some 'smart' controller or unit that expects a specific number of poles then changing the number of magnets might slightly change getaway behavior, etc since the magnet-reported cadence will not be the same with the original number of magnets. This is not generally an issue. In any case - easy to try and verify...

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

Posted: Apr 17 2018 1:47pm
by Scoot440
Okay - that is extremely helpful. I know what I'll be working on tonight.

Thanks again, teklektik for all the great advice/info!