pas / Hollowtech

[simonineaston]

Has anyone experience of the combination of a pedal sensor fitted to a Hollowtech crank set? Any comments?

[simonineaston]

Just to let others know, it turns out that the magnet ring, or moving part, of the pas is available in different forms, some of which are suitable for use with Shimano’s popular Hollowtech cranks. see eBay etc

[simonineaston]

Chapter three.
The plastic pas, ‘specially designed to use with the Hollowtech bottom bracket, complete with the usual 10 magnets, has turned up and indeed has a centre hole large enough to clear the bulk of the external bearing, but the clips moulded into the ring to fit the inner sprocket of Shimano’s Hollowtech road cranks are of no use to me on my Hollowtech Alfine cranskset.
I’m intending to mount the sensor on five stand-offs, each glued to the inside of the crank web - see photo and diagram. Each of the five stand-offs will have its own magnet used to keep the pas in position. Does that sound appropriate to you, dear reader? Can you think of a better way?

Concave crank web

Poor diagram of crank and sensor

[rjb]

Can you use 5 small neodymium disc magnets on the chainring bolt heads to hold the sensor ring in situ with an old steel inner chainring.

[simonineaston]

That would be a cool way to do it, but the sensor dia is too small, I think… the 42t chain ring lies entirely without the circle of the pas.

Picture of sensor & crankweb

[simonineaston]

I’m cutting up some aluminium tube for the stand-offs on a little Proxxon table saw - I’d forgotten (or praps never knew) how quickly ally heats up

[simonineaston]

Nearly there - just got to check the gap between the magnet ring (shown) and the pas itself.

picture of crank web

[Manc33]

I ended up using 4 x 2mm cable ties and attached it to the inner chainring, that had to be 24t (22t is too small). Luckily the inner chainring has holes, making it possible. I had to cut notches in the plastic on the magnet disc so the chainring can recess into it. I have done over 1,000 miles with it like this and it's been fine.







Chain clearance is OK:

[simonineaston]

That looks a great way to keep the magnet ring in situ, Manc33

[Galactic]

I ended up using 4 x 2mm cable ties and attached it to the inner chainring, that had to be 24t (22t is too small). Luckily the inner chainring has holes, making it possible. I had to cut notches in the plastic on the magnet disc so the chainring can recess into it. I have done over 1,000 miles with it like this and it's been fine.

I’m intending to mount the sensor on five stand-offs, each glued to the inside of the crank web - see photo and diagram. Each of the five stand-offs will have its own magnet used to keep the pas in position. Does that sound appropriate to you, dear reader? Can you think of a better way?

I'm just wondering how the cable binder and araldite solutions are working for you? Any feedback after a few months use?

(I'm struggling with how to connect the sensor to an Alfine 39 tooth cranks, really annoying)

[simonineaston]

I'm just wondering how the cable binder and araldite solutions are working for you?

The use of stand-offs to attach the pas magnet ring to the Alfine crank worked out really well. The ring is attached by magnetic attraction alone, however this appears to be perfectly adequate as there are few if any, other forces. As is probably obvious, It's tucked between crank and the bottom bracket in a way that’s very protected.
The work required to measure and prepare the 5 standoffs was within my capability and given the materials - ally tube - quite easy to achieve given that I had a number of key tools ie a Dremel and a dial caliper. The materials I used cost less than a tenner and came from eBay. It wasn't what I’d call an easy project, but for someone with plenty of time and prepared to take it step by step, it went without serious setbacks.
The measured gap between sensor & ring is 3mm which sits nicely in the spec. which is quoted as ‘1-4mm’.

[Galactic]

The ring is attached by magnetic attraction alone

Bit confused by this, I thought the tube was ally? Or are the magnets strong enough to exert enough attraction to keep the assembly in place?

Good to know that this is an option, certainly looks a lot tidier than cable binders, but I suspect I'll be using cable binders plus some kind of glue (2-component?), not having the tools to measure and cut the tubes at the right angle to fit the spider.

[simonineaston]

I did make a brief reference to the magnets pressed into the 5 standoffs but it was easy to overlook. These 5 extra magnets hold the pas magnet ring in place nice & snug. Here's a sketch.

Sketch of design…

[Galactic]

I did make a brief reference to the magnets pressed into the 5 standoffs but it was easy to overlook. These 5 extra magnets hold the pas magnet ring in place nice & snug. Here's a sketch.

Ah, that makes a lot more sense. Thanks for taking the time to reply.