PowerTap

[Newboy]

I want to build a new set of wheels. Questions:

1. Is PowerTap compatible with Garmin 705?

2. If so which PT should I use?

3. Can I get the hub alone without the computer? How much?

4. Which rim do you recommend?

[Christie]

1. The wireless powertap will be made ant+ compatible. Not sure if it is available already.

2. Ant+ wireless

3. Can buy hub alone. Not sure about price.

4. Lots of options. If I had to build a set now, I would go for an Edge(the American one, not Taiwanese) 32mm carbon clincher rim.

 

Send a PM to Dr Watt, or phone the agents, Bicyle power trading, for prices etc.  

[Johan Bornman]

TryBoy, I've built several PowerTap wheels for customers. Whilst Christie gave all the right electronic answers, I'd like to recommend you use a flat box-section rim.

 

The reason for that is that with the hub's large flange (70mm vs 35 or so for normal hubs), it leads to the spokes arriving at the rim at an angle other than 90 degrees or thereabouts. This makes for a bend in the spoke where the nipple ends the rim. The nipple cannot swivel enough and the spoke therefore has to take a detour. This bend happens inside the non-threaded lead-in section of the nipple, concentrating the bend on the first thread. The spoke soon snaps there as if a laser has cut it.

 

A good wheelbuilder will choose the flattest rim and go for 2X crossing in order to control the spoke angle.

 

I recommend you use a DRC ST17 rim. It is a Mavic Open Pro lookalike with all the good features of the Mavic product and a reasonable price.

 

Here's a photo of the problem. Put a straight-edge through the centre of the nipple and see how the spoke deviates from that.

 

 

 

PS - PowerTap wheels have to be sent back to the US for bearing replacements. I've just managed to perform the operation right here in SA and re-calibrate the wheel to original specs, something I'm quite happy about since customers really don't like to hear that they have to disassemble their wheels and ship the hub back to the US.

 

 

 

 

[Johan Bornman]

4. Lots of options. If I had to build a set now' date=' I would go for an Edge(the American one, not Taiwanese) 32mm carbon clincher rim.

 [/quote']

 

Christie, what's the nipple configuration on an Edge rim. Is it one of those rims where the nipple is hidden inside?

[TXS cyclist]

TryBoy' date=' I've built several PowerTap wheels for customers. Whilst Christie gave all the right electronic answers, I'd like to recommend you use a flat box-section rim.

 

The reason for that is that with the hub's large flange (70mm vs 35 or so for normal hubs), it leads to the spokes arriving at the rim at an angle other than 90 degrees or thereabouts. This makes for a bend in the spoke where the nipple ends the rim. The nipple cannot swivel enough and the spoke therefore has to take a detour. This bend happens inside the non-threaded lead-in section of the nipple, concentrating the bend on the first thread. The spoke soon snaps there as if a laser has cut it.

 

A good wheelbuilder will choose the flattest rim and go for 2X crossing in order to control the spoke angle.

 

I recommend you use a DRC ST17 rim. It is a Mavic Open Pro lookalike with all the good features of the Mavic product and a reasonable price.

 

Here's a photo of the problem. Put a straight-edge through the centre of the nipple and see how the spoke deviates from that.

 

 

 

PS - PowerTap wheels have to be sent back to the US for bearing replacements. I've just managed to perform the operation right here in SA and re-calibrate the wheel to original specs, something I'm quite happy about since customers really don't like to hear that they have to disassemble their wheels and ship the hub back to the US.

 

 

 

 

[/quote']

 

JB

 

Sorry but I dont know why your spokes is so scew... I have had wheels build onto powertaps and never see this thing you points out.

 

I also to date did not have a spoke broken even (10000 km's+ on one wheel, 4000+ on another and about 3000km on latest wheel)

 

I use axel rims (very nice value for money and actually a very nice rim build with sapim CX ray spokes. ) Use these wheels for training and racing and believe me they even went through a pothole or two and they just seem to be going.

 

The other set was build on easton circuit rims.. Again, I will recomend them anytime...! Never had a problem with them or a broken spoke.

 

Maybe it is the guy that build the wheels that might make a diference also. 

[Johan Bornman]

 

Sorry but I dont know why your spokes is so scew... I have had wheels build onto powertaps and never see this thing you points out.

 

I also to date did not have a spoke broken even (10000 km's+ on one wheel' date=' 4000+ on another and about 3000km on latest wheel)

 

I use axel rims (very nice value for money and actually a very nice rim build with sapim CX ray spokes. ) Use these wheels for training and racing and believe me they even went through a pothole or two and they just seem to be going.

 

The other set was build on easton circuit rims.. Again, I will recomend them anytime...! Never had a problem with them or a broken spoke.

 

Maybe it is the guy that build the wheels that might make a diference also. 

[/quote']

 

Texas, it's elementary geometry. Draw yourself a picture. Make one circle for the hub, another around it for the rim. Draw in one or two spokes coming out of the hub at a tangent.

 

Now draw another hub in that same sketch, with a larger circle. Make that same spoke now come out of the hub into the same hole in the rim. You'll see that the angle changes. As the rim's profile increases, it gets even worse. Most rims hace sockets that allow the nipples to swivel a few degrees but large flange hub exceed that. It's a fact of life. You and I can do nothing about it.

 

You don't seem to understand how spokes fail. They fail from metal fatigue. Potholes don't fatigue the spokes but the the wheel's continuous load and the cyclical tensioning and de-tensioning as the wheel rotates.

 

Your pothole theory suggests the spokes break in tension. They don't. I've posted numerous microscope pictures of the difference in a tension break and a fatigue break. You've been here long enough to know that and to have seen that.

 

Anecdotes don't help the cause. I'm talking about identifying and eliminating root problems which I've studied in many, many wheels.

 

 

 

 

Johan Bornman2008-10-23 11:07:20

[Christie]

Nipples go on the inside. Here is a pic of Edge 38mm tubbies:

http://fairwheelbikes.com/forum/files/thumbs/t_img_4572_126.jpg

 

The rims interest me because the spoke holes are not drilled into the rim, but moulded. This means the fibres are continious & uninterrupted, meaning that the rim can handle more stress at the spoke hole compared to other carbon rims. Spokes can be tensioned up to 170kgf (70% more than Zipp, for example)- perhaps Edge rims will be able to handle stress relieving of spokes after building?

 

They make the rims in 24, 38 (not 32, my bad) and 66 mm height. The rims are not cheap,  $700 (per rim) for the 38, $750 for the 66, +$100 for the clincher versions.

 

66mm ones difinitely not powertap friendly, but perhaps the spoke angle on the 38 or 24 wont be too bad.

Christie2008-10-23 12:00:00

[Johan Bornman]

Nipples go on the inside. Here is a pic of Edge 38mm tubbies:

 

 

The rims interest me because the spoke holes are not drilled into the rim' date=' but moulded. This means the fibres are continious & uninterrupted, meaning that the rim can handle more stress at the spoke hole compared to other carbon rims. Spokes can be tensioned up to 170kgf (70% more than Zipp, for example)- perhaps Edge rims will be able to handle stress relieving of spokes after building?

 

They make the rims in 24, 38 (not 32, my bad) and 66 mm height. The rims are not cheap,  $700 (per rim) for the 38, $750 for the 66, +$100 for the clincher versions.

 

66mm ones difinitely not powertap friendly, but perhaps the spoke angle on the 38 or 24 wont be too bad.

[/quote']

 

The moulded holes sound promising. 1.8mm spokes go into yield at 220kgf, so still not strong enough for a proper stress relieve.

 

I wonder what spoke angle they were drilled (moulded) at. The problem is not somuch the angle itself, but the way the rim limits the nipple to swivel. Eastons for instance, are drilled for  perfectly straight spokes even though the angle is way off 90 degrees.

 

Would you mind giving the photo another bash?

 

 

 

[Speed Devil]

Nipples go on the inside. Here is a pic of Edge 38mm tubbies:

 

 

The rims interest me because the spoke holes are not drilled into the rim' date=' but moulded. This means the fibres are continious & uninterrupted, meaning that the rim can handle more stress at the spoke hole compared to other carbon rims. Spokes can be tensioned up to 170kgf (70% more than Zipp, for example)- perhaps Edge rims will be able to handle stress relieving of spokes after building?

 

They make the rims in 24, 38 (not 32, my bad) and 66 mm height. The rims are not cheap,  $700 (per rim) for the 38, $750 for the 66, +$100 for the clincher versions.

 

66mm ones difinitely not powertap friendly, but perhaps the spoke angle on the 38 or 24 wont be too bad.

[/quote']

 

The moulded holes sound promising. 1.8mm spokes go into yield at 220kgf, so still not strong enough for a proper stress relieve.

 

I wonder what spoke angle they were drilled (moulded) at. The problem is not somuch the angle itself, but the way the rim limits the nipple to swivel. Eastons for instance, are drilled for  perfectly straight spokes even though the angle is way off 90 degrees.

 

Would you mind giving the photo another bash?

 

 

 

 

Johan, I just had a look at my Easton EA90 Earo rims. The rear wheel is radially laced on the non-drive side and the drive side is 1 crossed. On the non-drive side the spokes meet the rim at 90 deg and on the drive side less than 90 deg.

Will this have serious implications, seeing as they came out of the factory like that? I'm sure the engineers who designed the wheels knew what they were doing. Can the drive side be radially spoked so that the spokes meet the rim at 90 deg and still handle the day to day riding without failing?

Speed Devil2008-10-23 12:41:30

[Christie]

Speed Devil, the big problem mentioned here is the large flange diameter of powertap hubs. Deep sections with standard hubs are not so bad compared to deep sections with a powertap rear hub. I think JB is saying that the Easton rims could have been designed better. I guess the wheels were desined in the country that claims to have landed on the moon, but it is also the country that produced George W & Sara Palin, so not all clever people over there.

JB, I got the pic off  http://fairwheelbikes.com/forum/viewtopic.php?t=4437&sid=796b0c702f2bb944b50e6de11918fe58 some more pics, + a review.

Too bad they are still 50kg off on the yield tension, but getting close. 

[bruce]

1. The wireless powertap will be made ant+ compatible. Not sure if it is available already.

2. Ant+ wireless

3. Can buy hub alone. Not sure about price.

4. Lots of options. If I had to build a set now' date=' I would go for an Edge(the American one, not Taiwanese) 32mm carbon clincher rim.

 

Send a PM to Dr Watt, or phone the agents, Bicyle power trading, for prices etc.  

[/quote']

 

The new range of powertaps will all be wireless and all be Ant+Sport, even down to the Pro level.

 

The range will now be SLC+, SL+ and Pro+

 

SLC+ will have ceramic bearings.  They all have increased axle diameter as well.  SL+ is the current SL 2.4 with Ant+Sport compatibility.

 

TryBoy, drop me a PM if you want pricing details.  I help out the Bicycle Power Trading guys up here in Gauteng so I can give you details.  Don't have pricing yet for the new '+' hubs yet, they have just been (or are about to be) released in the US and with the Rand doing what it is doing, who knows!!

 

The current 2.4 hubs are upgradeable to Ant+ though.

[GoLefty!!]

work on exchange rate of R13 to the US$1.

 

It's only going south for now.

[Guest Big H]

work on exchange rate of R13 to the US$1.

 

It's only going south for now.

 

YOOO HOOO!!!!!!! Payday is on the 25th!!!!!!!!!

[Johan Bornman]

 

Johan' date=' I just had a look at my Easton EA90 Earo rims. The rear wheel is radially laced on the non-drive side and the drive side is 1 crossed. On the non-drive side the spokes meet the rim at 90 deg and on the drive side less than 90 deg.

Will this have serious implications, seeing as they came out of the factory like that? I'm sure the engineers who designed the wheels knew what they were doing. Can the drive side be radially spoked so that the spokes meet the rim at 90 deg and still handle the day to day riding without failing?

[/quote']

 

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I had another look at my post and I can see why the confusion. Let me try again. Easton wheels are drilled in such a way that the spokes are not placed under any undue stress other than pure tension. In other words, the guys knew what they were doing.

 

At the hub, where the spokes screw in, they could easily have got it wrong. However, the holes are drilled perfectly for the number of cross spokes and perfectly for the angle of the hub flange to the end point at the rim.

 

At the rim, they arrive at an angle that's slightly off 90 degrees as you point out, but well within the nipple's ability to swivel inside the rim. You'll notice that the spokes and nipples are perfectly in line even though the nipple and rim do not square up.

 

The photo that I posted shows that the nipple can swivel a little bit but that the large flange hub requires even more swivel and therefore the spoke bends where it enters the nipple. Put a piece of paper in line with the centre of the nipple and you'll see the deviation. Deviation is bad.

 

Nipple swivel is best accommodated with a socket or so-called "double-eyelet" in a rim. This allows far more swivel than plain drilled rims.

 

 

Most rims are, as it is, drilled for left and right spokes but for average sized hubs. This photo shows the nipple socket that allows a spoke to swivel in the rim.

This photo shows the worst possible scenario. An internal nipple rim with the nipple inverted and its head now pointing to the hub and its feet pointing towards the tyre. This nipple wants to settle in the 90 degree position due to its flat head. However, the rim designers thought their hub had a diameter of zero and therefore drilled the holes perfectly square. Therefore, the spoke arrives at the rim at an angle, then immediately bends to accommodate the 90 degree nipple inside. Even worse, the rim is about 3mm thick at the hole, making it impossible for the spoke to swivel a bit.

 

 

Here is a photo of an inelegant elegant solution to a very big problem. A Rohloff Speedhub in a MTB wheel.

 

 

It may not look pretty and trap more dirt than a broken tooth in a bar that serves peanuts, but it keeps the spoke line straight.

 

 

 

[intern]

Well now that cleared it up, thanks JB 

[Johan Bornman]

Johan' date=' I just had a look at my Easton EA90 Earo rims. The rear wheel is radially laced on the non-drive side and the drive side is 1 crossed. On the non-drive side the spokes meet the rim at 90 deg and on the drive side less than 90 deg.

Will this have serious implications, seeing as they came out of the factory like that? I'm sure the engineers who designed the wheels knew what they were doing. Can the drive side be radially spoked so that the spokes meet the rim at 90 deg and still handle the day to day riding without failing?

[/quote']

 

These conversations will be so much easier if we all just stick to Right and Left, instead of this clunky Drive Side and Non Drive Side.

 

You ask whether a rear wheel can be radially laced on both sides. The answer is no. In order for the spokes to transmit torque they have to be tangentially laced.  A radial spoke cannot transmit torque.

 

 

Further, the practice of lacing a wheel radially on the one side and tangentially on the other is one that limits spoke life. It means all the transmission forces on a wheel are concentrated on every second spoke only. Making it worse, they've chosen the spokes on the dished side of the wheel, which are already under the highest stress of the lot.

 

Great White once put it very elegantly and said that these incredibly light parts are all sacrificial. He's right.

 

Texas Sally bragged about a wheel that's done 10 000 kms without a problem Whoopee! A well designed and built wheel will easily last 250 000 kms. The original rim wont survive since they get ground down by braking, but the original spokes and hub does go the entire distance.

 

Fotunately for these manufacturers of these poofter wheels their customers think 10 000 kms is some sort of world record and they thus put up with the high cost of going into the wheel's second season of riding. Or, they simply discard them for the next fashion.