Nine Continent Rear Wheel Dishing

[Tiberius]

I've been reading comments about the problems of getting the dishing right on the 9C rear motors.

AFAIUI, the basic problem is that the geometry puts the rim too far to the left once you have a gear cluster on the axle. The right hand spoke holes on the hub are too far to the left.

I've also read that this can be fixed by putting the spokes in the other way round, so that they emerge on the outside rather than the inside of the flange. Now this worries me. Because the angle of the spoke appears to be different, it may look as if the geometry has been altered, but in reality it hasn't. The point at which the force is transferred from the spoke to the hub is the hole in the flange, not the bend in the spoke, and even under tension a spoke is slightly curved to allow for this. So turning the spoke round might make a tiny change in the geometry, but not a big enough one to to fix the problem.

Here's some other ideas.

An offset rim. Ie., one with the holes not on the centre line. This might be difficult with double walled rims, but it should be possible to drill a new set of holes in a single walled rim.

A double rim. Take two narrow rims, weld or other wise join them together to make a wide rim. Then just use the spoke holes on one side.

An adaptor plate on the hub. Machine up a ring out of aluminium plate that bolts to the existing flange using the existing spoke holes, and then provides new spoke holes. You might end up with slightly shorter spokes, or spoke holes moved around half a hole, but that shouldn't prevent the wheel being laced up.

Discuss...

Nick

 

[dnmun]

go read zoot katz's thread on his build. he has some good pictures, he had to cold set the frame to get the dropouts to 140mm on top of respoking and dishing to the max, and will add some more spacing washers to get it centered. maybe a wide rim helps, zoot knows. go read his new cat thread.

 

[johnrobholmes]

An offset rim may be the best final solution. All drive side spokes outbound, and non drive inbound will also help the spoke angles. It at least allows for proper dish without having drive side spokes with no bracing angle.

 

[spike]

My 9C is on a CroMo MTB frame with a 7 speed freewheel. I used spacers on the left side of the hub to get the wheel centered. I know that isn't an option for Alu frames, but is there anything wrong with that for a CroMo frame? It hasn't caused any problems including the gear shifting. It feels like I'm missing some information because a few people have mentioned the problem of dishing and not being able to fit a 7 speed freewheel, yet it was an easy install for me.

 

[spinningmagnets]

spike, could you please post some pics ? close-ups of left and right, then a a rear shot aligned inline with the frame ?Thanks in advance.

 

[jag]

I've also read that this can be fixed by putting the spokes in the other way round, so that they emerge on the outside rather than the inside of the flange. Now this worries me. Because the angle of the spoke appears to be different, it may look as if the geometry has been altered, but in reality it hasn't. The point at which the force is transferred from the spoke to the hub is the hole in the flange, not the bend in the spoke.

I built my 9C wheel this way, and the freewheel side spokes are resting on the side of the hub, thus potentially transferring the load point outward towards the edge of the hub flange.. See the second picture in the build thread.
http://endless-sphere.com/forums/viewtopic.php?f=4&t=9549
I was a bit concerned with the wheel strength in the beginning, but it has worked for half a year now.

Here's some other ideas.
:
A double rim. Take two narrow rims, weld or other wise join them together to make a wide rim. Then just use the spoke holes on one side.
:
Discuss...
Nick

Anyone have more ideas how to join two rims? I read that Alaska snow riders will double rims, but I presume they also double tires.

Some other ideas that came to mind when I built my 9C were:
Bend frame asymetrically to shift wheel sideways. (I did this with some success)
Machine or file the 9C freewheel mount and axle to shift sideways. (I didn't do this)
Try different freewheels to see if they seat differently.

 

[spike]

spike, could you please post some pics ? close-ups of left and right, then a a rear shot aligned inline with the frame ?Thanks in advance.

I'll post some pics after work tonight. Cheers.

 

[Zoot Katz]

I've also read that this can be fixed by putting the spokes in the other way round, so that they emerge on the outside rather than the inside of the flange. Now this worries me. Because the angle of the spoke appears to be different, it may look as if the geometry has been altered, but in reality it hasn't. The point at which the force is transferred from the spoke to the hub is the hole in the flange, not the bend in the spoke.

I built my 9C wheel this way, and the freewheel side spokes are resting on the side of the hub, thus potentially transferring the load point outward towards the edge of the hub flange.. See the second picture in the build thread.
http://endless-sphere.com/forums/viewtopic.php?f=4&t=9549
I was a bit concerned with the wheel strength in the beginning, but it has worked for half a year now.

It does look weird but that's how JRH recommended lacing mine. It helps pull the rim further right but not enough.
I still have to stress relieve and tweak the wheel so maybe I can get the rim another mm to the right.

Hey, thanks for that pic. It doesn't look like you're running torque arms or using those tabbed counter-rotation washers.
Those were puzzling me. Since they weren't engaging the vertical dropout at the bottom, I figured they were for horizontal dropouts or rear fork ends.
I cut them down to make C-washers for spacers on the left side.

 

[spike]

spike, could you please post some pics ? close-ups of left and right, then a a rear shot aligned inline with the frame ?Thanks in advance.

OK. Here they are...View attachment 8

 

[spike]

spike, could you please post some pics ? close-ups of left and right, then a a rear shot aligned inline with the frame ?Thanks in advance.

One more ....

 

[Chalo]

I've also read that this can be fixed by putting the spokes in the other way round, so that they emerge on the outside rather than the inside of the flange. Now this worries me. Because the angle of the spoke appears to be different, it may look as if the geometry has been altered, but in reality it hasn't. The point at which the force is transferred from the spoke to the hub is the hole in the flange, not the bend in the spoke, and even under tension a spoke is slightly curved to allow for this. So turning the spoke round might make a tiny change in the geometry, but not a big enough one to to fix the problem.

Spokes don't understand theory, they only transmit forces along their wires. The directions those wires are pointing show the orientations of their force vectors-- really!

Customary wheel lacing is alternating, with half the spokes laced elbows-in and half elbows-out. To lace them all elbows-in reduces the spokes' average bracing angle and makes a wheel weaker to lateral loads-- without even considering the very small right side flange offset of the hub motor in question. In this light, it makes very good sense to lace the right side spokes of a dished rear hubmotor all outside the flange and the left side spokes all inside the flange. It really helps, especially when wheel dish is extreme. You can tell by using a tensiometer that the change is not merely cosmetic.

Look at it this way-- if a hub has 30mm of left side flange spacing and 10mm of right side flange spacing, the ratio of tension between right and left spokes, with the rim centered on the axle, is about 3:1. (In other words, you have to get the right side cranked up to three times the tension of the left side for it to bias the rim that much towards one side.) If you can move all the right side spokes outboard by 5mm at the hub (3mm thick flange plus 2mm spoke diameter), then the spacing changes to 30mm left/15mm right and the tension ratio becomes about 2:1. That's a significant and beneficial tension difference, made possible mainly because the right side spacing is so small.

Another similar benefit can be had by using an offset drilled rim. Here is one extreme example:

Ritchey, Bontrager, Velocity, Surly, and other manufacturers make offset drilled rims for multi-speed rear wheels and disc front wheels. When using one, the rim can be centered even if the spokes' attachment points on the rim are not.

Chalo

 

[jag]

I built my 9C wheel this way, and the freewheel side spokes are resting on the side of the hub, thus potentially transferring the load point outward towards the edge of the hub flange.. See the second picture in the build thread.
http://endless-sphere.com/forums/viewtopic.php?f=4&t=9549
I was a bit concerned with the wheel strength in the beginning, but it has worked for half a year now.

Hey, thanks for that pic. It doesn't look like you're running torque arms or using those tabbed counter-rotation washers.
Those were puzzling me. Since they weren't engaging the vertical dropout at the bottom, I figured they were for horizontal dropouts or rear fork ends.
I cut them down to make C-washers for spacers on the left side.

Actually both the two tabbed washers and two short 9C torque arms are there, just pointing forward so they are not visible in the closeup picture. Tabbed washers are on the inside engaging into the dropout (old style, long forward pointing grove). Torque arms on the outside at an angle so they will jam against the chainstay if hub tries to spin out.

However, the dropout itself is both thicker and harder than the stamped steel torque arms and tabbed washers together. I think in practice it is the dropout that takes all the torque. When I have it apart next time I'll look for any deformations in the dropout and acle shaft.

 

[Zoot Katz]

I built my 9C wheel this way, and the freewheel side spokes are resting on the side of the hub, thus potentially transferring the load point outward towards the edge of the hub flange.. See the second picture in the build thread.
http://endless-sphere.com/forums/viewtopic.php?f=4&t=9549
I was a bit concerned with the wheel strength in the beginning, but it has worked for half a year now.

Hey, thanks for that pic. It doesn't look like you're running torque arms or using those tabbed counter-rotation washers.
Those were puzzling me. Since they weren't engaging the vertical dropout at the bottom, I figured they were for horizontal dropouts or rear fork ends.
I cut them down to make C-washers for spacers on the left side.

Actually both the two tabbed washers and two short 9C torque arms are there, just pointing forward so they are not visible in the closeup picture. Tabbed washers are on the inside engaging into the dropout (old style, long forward pointing grove). Torque arms on the outside at an angle so they will jam against the chainstay if hub tries to spin out.

However, the dropout itself is both thicker and harder than the stamped steel torque arms and tabbed washers together. I think in practice it is the dropout that takes all the torque. When I have it apart next time I'll look for any deformations in the dropout and acle shaft.

Thanks for the clarification. Both my tabbed washers and torque arms are gone now.
Talking with Justin yesterday he related how he had requested that 9 Continents not install them.
That got lost in translation or it may be a liability issue with 9 C.
I can see how the tabbed washers and torque arms would help beef up a flimsy stamped dropout or rear fork end. They have no control over what frame will be attached to their wheels.

He also said you don't really need torque arms on the rear, even with regen. Just keep tightening the nuts until they stop getting loose.
That's the way my X5 has been running for almost a whole year. I just checked my nuts before every ride.
They got a little loose for the first 5 or six rides and then stayed tight. I always check them a few times after the wheel has been off.

Anyway, back on topic: I stress relieved and touched up the wheel this morning. The final truing was done by loosening off the left spokes where needed. I'm satisfied that it's close enough to perfect for a test run when the time comes. There are no more excuses for not starting to play with the gears.

 

[dogman dan]

Zoot, are you and I and Justin the only guys on the planet that understand that a properly installed motor on good dropouts needs no torque arms?

Why not just run a 5 speed cluster? It should be plenty, especiailly if you have a triple up front.

 

[jag]

Zoot, are you and I and Justin the only guys on the planet that understand that a properly installed motor on good dropouts needs no torque arms?

I agree that when the axle nut is properly tightened, all the torque goes from axle to dropout. (Simply since that will generally be the stiffest connection)

However, due to inattention or otherwise an axle nut is not properly tightened or comes loose, tabbed washers and torque arms provide a backup path for the torque.

Car wheels have 4 or 5 bolts; trucks more. Reasoning is similar: they provide redundancy. There were some Dacia cars with 3 bolt wheels. The loss of one bolt in a 5 bolt wheel is less of a problem than the loss of one in a 3 bolt.

 

[Chalo]

Zoot, are you and I and Justin the only guys on the planet that understand that a properly installed motor on good dropouts needs no torque arms?

My X5305 running at 36V and 35A pried open the tips of two good quality chromoly forks. The axle nuts never worked loose, and the axle didn't spin in either case-- but I would only use dropouts as torque anchors if they were thick, broad plate-style dropouts. Otherwise I'd definitely use some sort of torque arm or sturdy tabbed washers.

Chalo

 

[Tiberius]

I've also read that this can be fixed by putting the spokes in the other way round, so that they emerge on the outside rather than the inside of the flange. Now this worries me. Because the angle of the spoke appears to be different, it may look as if the geometry has been altered, but in reality it hasn't. The point at which the force is transferred from the spoke to the hub is the hole in the flange, not the bend in the spoke, and even under tension a spoke is slightly curved to allow for this. So turning the spoke round might make a tiny change in the geometry, but not a big enough one to to fix the problem.

Spokes don't understand theory, they only transmit forces along their wires. The directions those wires are pointing show the orientations of their force vectors-- really!

Customary wheel lacing is alternating, with half the spokes laced elbows-in and half elbows-out. To lace them all elbows-in reduces the spokes' average bracing angle and makes a wheel weaker to lateral loads-- without even considering the very small right side flange offset of the hub motor in question. In this light, it makes very good sense to lace the right side spokes of a dished rear hubmotor all outside the flange and the left side spokes all inside the flange. It really helps, especially when wheel dish is extreme. You can tell by using a tensiometer that the change is not merely cosmetic.

Look at it this way-- if a hub has 30mm of left side flange spacing and 10mm of right side flange spacing, the ratio of tension between right and left spokes, with the rim centered on the axle, is about 3:1. (In other words, you have to get the right side cranked up to three times the tension of the left side for it to bias the rim that much towards one side.) If you can move all the right side spokes outboard by 5mm at the hub (3mm thick flange plus 2mm spoke diameter), then the spacing changes to 30mm left/15mm right and the tension ratio becomes about 2:1. That's a significant and beneficial tension difference, made possible mainly because the right side spacing is so small.

Another similar benefit can be had by using an offset drilled rim. Here is one extreme example:

Ritchey, Bontrager, Velocity, Surly, and other manufacturers make offset drilled rims for multi-speed rear wheels and disc front wheels. When using one, the rim can be centered even if the spokes' attachment points on the rim are not.

Chalo

Hi Chalo,

What you say about spokes is right for most of their length - they act in tension and the force vector is along the spoke. But look carefully at them near the elbow end. They are slightly curved at the end and the force vector doesn't run along the spoke to the elbow - it continues straight and ends up nearer the middle of the flange.

But if manufacturers are offering offset rims, that's the best solution. Do you have any link?

Nick

 

[Chalo]

What you say about spokes is right for most of their length - they act in tension and the force vector is along the spoke. But look carefully at them near the elbow end. They are slightly curved at the end and the force vector doesn't run along the spoke to the elbow - it continues straight and ends up nearer the middle of the flange.

They are cantilevered the same amount at the elbow whether the spoke is laced inboard or outboard. But lacing the flatter side outside the flange can help address the tension imbalance. The spoke elbow is a lever; you can use the lever to increase mechanical advantage (spokes outside the flange) or reduce mechanical advantage (spokes inside the flange).

But if manufacturers are offering offset rims, that's the best solution. Do you have any link?

http://surlybikes.com/parts/largemarge_pop.html
http://www.cyclelink.com.au/category554_1.htm
http://www.velocityusa.com/default.asp?contentID=599
http://www.universalcycles.com/shopping/product_details.php?id=773

Chalo

 

[Fredo]

Hey,

Just got my 9c rear wheel and as a lot of people I have this 10mm offset on the left.
All the solutions I have seen are based on wheel dishing or frame spacing.
I use a 5 speed freewheel and there is some spare space between the sprocket and the dropout so I was considering just filing/machining the shoulder to get those additional 10mm and use washers/spacers on the other side.
I can not use frame spacing on my aluminum frame (Norco Vermont) and I am reluctant investing hours touching spokes and potential decreasing reliability.

Any comment or feedback on this approach?
Thanks
Fredo

 

[johnrobholmes]

sounds like a good method to me!

 

[spinningmagnets]

Copied from another post (thanks, vim), here's a link for an off-set rim. Useful for a 9C rear hub (or any hub) that has dishing issues. PS...I haven't tried this personally, YMMV.

http://www.everybicycletire.com/Shopping/pc-1779-24-velocity-synergy-oc-rim.aspx

 

[fabiograssi]

Hello!

Finally I am trying to relace my nine continents in a more robust rim.

Measured the motor and rim in Justin's spoke calculator, and got the new spokes (phil wood 13/14 buted). Time to relace!

Well, relace a wheel is not for amateurs, I know. But I am in Brazil, too far away, with too expesive freight costs, and with a hungry customs... So I need to do it myself...

Reading this topic, I found the same pattern that I am trying to do!

At this time, I only screw the spokes a little bit... Please, give a look at the pictures and tell me what you guys think about this build.

All the spokes from chain side are in the outer side of the hub; in the wires side of the motor, all the spokes are in the inner side.

Please, give me your oppinions!

Thanks!

- Fabio

View attachment 3

 

[Zoot Katz]

Looks okay to me.
Just make sure you have a "box" rather than a "cross" over the valve hole and start tightening.
IIRC, the drive side required higher spoke tension to get the rim centered.

 

[fabiograssi]

Dear Zoor Katz, thanks for your oppinion!

The valve section is ok! :wink:

In fact, I cutted the spokes on the drive side 2mm shorter than the wires side, so I believe I can tight with same tension both sides. The spokes on drive side are almost "straight". I will try to take a picture!

Thanks,

- Fabio

 

[Zoot Katz]

Dear Zoor Katz, thanks for your oppinion!

The valve section is ok! :wink:

In fact, I cutted the spokes on the drive side 2mm shorter than the wires side, so I believe I can tight with same tension both sides. The spokes on drive side are almost "straight". I will try to take a picture!

Thanks,

- Fabio

Congratulations on successfully accomplishing something many people fear undertaking.
I screwed up lacing mine the first time and had to redo it.
Good idea shortening the spokes on the drive side. I wished I'd done that when tensioning up the wheel.