Is there anyone that can service PowerTap hubs on here?
- Thread starter rjsdavis
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glpinxit":3dbqfl3g said:
I did not know this... but have just been reading up on it as a result of your post. I see that they've bought Time pedals as well to help remove competition from the market.
The point of the post, was that I was hoping that one of the techs at either Palligap or CycloPowerMeters might trundle onto this forum sometimes... or someone on here might know one of the techs to take on some private work? Something like that anyway. It's a small world sometimes, but not small enough at the moment!
I run Rat Race Cycles in Nunhead, London SE15 and we've serviced plenty of PowerTap hubs - HOWEVER we're definitely not an authorised service centre.
That is to say, if it's the electronics / torque tube side of the hub that's problematic, it usually works out more economical to replace the hub than to repair it (certainly so these days, which is probably why Paligap / CPM don't really deal with them any more.
Apart from that, it's basically a Novatec hub axle and freehub and sealed bearings so relatively easy to service / swap freehub body if needed.
The things to remember are:
1) most important the "Powercap" on the non-drive-side is connected by a tiny thin ribbon-like connector. Once you've used the tool to unscrew the three-sided lockring that holds it in place, do not twist the powercap to remove it - it pulls straight away from the hub. If you take it off and have a look at the connector, you'll see why... it's the tiny thin thing on the right hand side of this photo, which will get destroyed if you twist the Powercap:
2) the axle has a small magnet attached to it - it's how the electronics of the wheel can tell that it's turning, so calculate RPM and do the torque-calculating maths. It's only taped on, but it's a) vital that it's there and b) easy to pull off if you're not careful about removing the axle through the hub by lining up the magnet with one of the wider spaces for it to go through (a hex shape, IIRC)
(DC Rainmaker's photo)
3) ...so remove the axle toward the drive-side, with the freehub body still attached if you prefer.
That is to say, if it's the electronics / torque tube side of the hub that's problematic, it usually works out more economical to replace the hub than to repair it (certainly so these days, which is probably why Paligap / CPM don't really deal with them any more.
Apart from that, it's basically a Novatec hub axle and freehub and sealed bearings so relatively easy to service / swap freehub body if needed.
The things to remember are:
1) most important the "Powercap" on the non-drive-side is connected by a tiny thin ribbon-like connector. Once you've used the tool to unscrew the three-sided lockring that holds it in place, do not twist the powercap to remove it - it pulls straight away from the hub. If you take it off and have a look at the connector, you'll see why... it's the tiny thin thing on the right hand side of this photo, which will get destroyed if you twist the Powercap:
2) the axle has a small magnet attached to it - it's how the electronics of the wheel can tell that it's turning, so calculate RPM and do the torque-calculating maths. It's only taped on, but it's a) vital that it's there and b) easy to pull off if you're not careful about removing the axle through the hub by lining up the magnet with one of the wider spaces for it to go through (a hex shape, IIRC)
(DC Rainmaker's photo)
3) ...so remove the axle toward the drive-side, with the freehub body still attached if you prefer.
Pierre":25yhdr5s said:I run Rat Race Cycles in Nunhead, London SE15 and we've serviced plenty of PowerTap hubs - HOWEVER we're definitely not an authorised service centre.
That is to say, if it's the electronics / torque tube side of the hub that's problematic, it usually works out more economical to replace the hub than to repair it (certainly so these days, which is probably why Paligap / CPM don't really deal with them any more.
Apart from that, it's basically a Novatec hub axle and freehub and sealed bearings so relatively easy to service / swap freehub body if needed.
The things to remember are:
1) most important the "Powercap" on the non-drive-side is connected by a tiny thin ribbon-like connector. Once you've used the tool to unscrew the three-sided lockring that holds it in place, do not twist the powercap to remove it - it pulls straight away from the hub. If you take it off and have a look at the connector, you'll see why... it's the tiny thin thing on the right hand side of this photo, which will get destroyed if you twist the Powercap:
2) the axle has a small magnet attached to it - it's how the electronics of the wheel can tell that it's turning, so calculate RPM and do the torque-calculating maths. It's only taped on, but it's a) vital that it's there and b) easy to pull off if you're not careful about removing the axle through the hub by lining up the magnet with one of the wider spaces for it to go through (a hex shape, IIRC)
(DC Rainmaker's photo)
3) ...so remove the axle toward the drive-side, with the freehub body still attached if you prefer.
Hi Pierre
Many thanks for this helpful response Pierre - thank you!
I know exactly what you are saying about the Powercap. I've had to change the battery a number of times, and am well aware that this pulls straight off. It is definitely not physically damaged.
The hub does work, it does register and transmit power readings, but in my non-professional opinion, they have become a little erratic and I don't think that they're completely accurate. This is where my problem lies...
In such a scenario, I am fully expecting CPM to simply tell me that they need to replace the torque tube, replace it, and I've would have had no doubt that this would have cured the problem and I would have a working wheel again, BUT I'll be down the best part of 400 notes for the priviledge. I've seen from other users elsewhere on the net, that a possible cause is that the taped down magnet that you've helpfully provided a picture of, is the root cause, but because I don't know enough about how the electronics of this hub actually work, don't know if this is something that can be adjusted by a knowledgeable tech to cure the problem, or if it is something that actually needs to be replaced?
Surely, if it's just a magnet (which I didn't know that's all it was before), that really can't become faulty (I totally accept that it might have become loose or positioned incorrectly, or something similar though with the passage of time and use)? I had envisoned that the torque tube had far more complex internal electronics involved within it than simply having a magnet taped to the outside of it to provide measurement data!
I haven't attempted to do anything with the hub at all. I simply continue to use it as is, and put up with what appears to be the slightly iffy looking data for now, until I can find a more cost effective solution to fix it. Am I right in guessing that the Powercap then takes readings from the magnet, taped to the torque tube, and that in fact it is more likely that it is the Powercap to have developed a fault than the torque tube/magnet itself?
Many thanks again for any info...
If you're getting iffy readings, it may well be that the torque sensors are on the blink - that's the bit that _can_ be expensive to remove and replace. The hub basically measures two things: the torque between the freehub body and the hub body, and the number of RPM the hub is doing. The Powercap does the maths bit, basically working out force per revolution and / or per second and turning that into a measure of input power.
The magnet can't really become faulty, although technically they can lose their magnetic charge if you bash them around a lot but I've never seen that happen. They sometimes come dislodged but usually you get no readings at all rather than erratic readings. The magnet is taped to the axle, not the torque tube.
The torque tube is a separate part that sits between the driven part of the hub body (the ratchets the freehub pawls engage with and drive) and the hub body itself. It's a set of strain gauges that measure the _tiny_ amount of flex when you put power in - they're the sensitive bit that needs calibrating carefully to give you accurate force readings. If they are damaged, worn out or on the blink they'll give you wonky readings.
So it sounds like you may be in for torque tube replacement and recalibration if you want to keep the hub, and that's potentially expensive... sorry. However, if it's going to cost you £400, there are certainly other power-metering options for that sort of money. I've got a 4iiii crank and it's been flawless.
The magnet can't really become faulty, although technically they can lose their magnetic charge if you bash them around a lot but I've never seen that happen. They sometimes come dislodged but usually you get no readings at all rather than erratic readings. The magnet is taped to the axle, not the torque tube.
The torque tube is a separate part that sits between the driven part of the hub body (the ratchets the freehub pawls engage with and drive) and the hub body itself. It's a set of strain gauges that measure the _tiny_ amount of flex when you put power in - they're the sensitive bit that needs calibrating carefully to give you accurate force readings. If they are damaged, worn out or on the blink they'll give you wonky readings.
So it sounds like you may be in for torque tube replacement and recalibration if you want to keep the hub, and that's potentially expensive... sorry. However, if it's going to cost you £400, there are certainly other power-metering options for that sort of money. I've got a 4iiii crank and it's been flawless.
Pierre":3gap4331 said:
Hi Pierre
Brilliant reply - thank you so much. No-one I've ever seen has been able to simply explain how the PT hub works in such a straightforward fashion!
I'm wondering... as I sense that you know your onions - are you able to supply/fit a new torque tube? I'm hoping you're not going to say that this something that only CPM can do in the UK under license or some other nonsense!
If it is CPM only that can obtain torque tubes - if I was able to get my hands on another torque tube from SRAM, would you be able to fit it?
Many thanks for the really helpful responses.
Agh - that's the bit I have no experience of, sorry. I'd imagine it requires a couple of specialist tools to remove and refit, and probably the right kind of epoxy, followed by specialist calibration equipment, which is probably why they charge so much for it.
The article I took the axle magnet photo from is a factory tour by Ray, "DCRainmaker", who has a _lot_ of information on almost every post but this one is pretty interesting to see how they make your hub:
https://www.dcrainmaker.com/2013/10/sce ... ters.html/
...the 60Nm torque wrench is no problem, but I'm guessing it's also bonded in and I'd assume the calibration equipment is pretty specific too. So although the process itself is relatively straightforward, the tools would be eye-wateringly expensive, which is why CPM charge so much for it.
So I'm totally fine with servicing the hub bits because once you understand which parts are common to many hubs it's not a dangerous mysterious black box, but unfortunately the parts involved with torque require equipment and knowledge we don't have. Sorry!
The article I took the axle magnet photo from is a factory tour by Ray, "DCRainmaker", who has a _lot_ of information on almost every post but this one is pretty interesting to see how they make your hub:
https://www.dcrainmaker.com/2013/10/sce ... ters.html/
...the 60Nm torque wrench is no problem, but I'm guessing it's also bonded in and I'd assume the calibration equipment is pretty specific too. So although the process itself is relatively straightforward, the tools would be eye-wateringly expensive, which is why CPM charge so much for it.
So I'm totally fine with servicing the hub bits because once you understand which parts are common to many hubs it's not a dangerous mysterious black box, but unfortunately the parts involved with torque require equipment and knowledge we don't have. Sorry!
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So that's an internal ish, probably hall effect sensor, standard revolution counter (same as external ones), probably cost peanuts to make.
And the strain gauges probably don't cost a lot in the freehub ratchets whatsit.
They can charge a lot because they can charge a lot. I doubt it's the part cost or even labour.
The choice between a paying a lot for a bespoke ring tube or a new wheel.
Off to have a skeg of that link.
Edit
Great to see the semi automated wheel build process.
So that's an internal ish, probably hall effect sensor, standard revolution counter (same as external ones), probably cost peanuts to make.
And the strain gauges probably don't cost a lot in the freehub ratchets whatsit.
They can charge a lot because they can charge a lot. I doubt it's the part cost or even labour.
The choice between a paying a lot for a bespoke ring tube or a new wheel.
Off to have a skeg of that link.
Edit
Great to see the semi automated wheel build process.
Thank you Pierre. Gutted.
