Help! My next project

[Benjahmin]

Well tight wad has won out, so I've decided to go with what I've got.
First was scavenging the rim from a defunct Ezee motor case:


Having removed the spokes I've used the Ryan method of finding the ERD. I tightened nipples onto two old spokes so they would not move. Cut off the j bend and cut and file the spokes to the same length. In this case215mm. Insert the spokes into opposite holes and measure between the two ends, 172mm. Then add the lot together to get ERD, 215+215+172= 602.


Next stop will be Grin Technologies site to remind myself on how to measure the hub motor to get spoke length and offset.
So to spokes and the much debated 'What diameter?'. Remind me is it 12 or 13 guage? I favour Sapim super strongs if I can get them.

 

[saneagle]

Well tight wad has won out, so I've decided to go with what I've got.
First was scavenging the rim from a defunct Ezee motor case:
View attachment 63359

Having removed the spokes I've used the Ryan method of finding the ERD. I tightened nipples onto two old spokes so they would not move. Cut off the j bend and cut and file the spokes to the same length. In this case215mm. Insert the spokes into opposite holes and measure between the two ends, 172mm. Then add the lot together to get ERD, 215+215+172= 602.
View attachment 63360

Next stop will be Grin Technologies site to remind myself on how to measure the hub motor to get spoke length and offset.
So to spokes and the much debated 'What diameter?'. Remind me is it 12 or 13 guage? I favour Sapim super strongs if I can get them.

That's a lot of work to get a simple measurement. I just measure the diameter in two directions and add 5mm.

 

[harrys]

"Having removed the spokes I've used the Ryan method of finding the ERD. "

I like that method. I have some straight spokes that I bought by mistake. Would be a good use for them.

On my last wheel, I used the ERD on the seller's website. Normally, I don't mind if they are a bit long, because I use double wall rims and can add washers too. These .
spokes were so long, they poked past the upper wall.

 

[Benjahmin]

That's a lot of work to get a simple measurement. I just measure the diameter in two directions and add 5mm.

Well there ya go. Experience wins out. Sometimes you've just gotta do it the hard way to see the easy way !

 

[Benjahmin]

The Grin spoke calculator is giving me left spoke length 241mm and right 240.1, so I'm thinking 241 all round.

Online Spoke Calculator for Hubmotors and Ebikes

Our handy spoke length calculator allows for easy calculation of spoke length for custom builds - and is the only one of its kind to include paired spoke holes in the flange as is common with many large diameter hub motors. It also creates an automatic side view drawing of the laced wheel and...

ebikes.ca

 

[saneagle]

Well there ya go. Experience wins out. Sometimes you've just gotta do it the hard way to see the easy way !

What about you try it my way and see if you get the same result or how close it is? I've never done it the proper way so I'd be interested in whether there's any difference.

 

[Benjahmin]

OK, measured it as 598 +5 = 603 against Ryans way of 602. Near enuf methinks.

 

[Sturmey]

........ Remind me is it 12 or 13 guage? I favour Sapim super strongs if I can get them.

Looking at your hub in the spoke calculator you posted above, you have a large dish/offset of 9mm and a spoke tension ratio of 32:68. I would use the lighter 14 gauge rather than the heavier 12 or 13 gauge as there wont be enough tension on the disc side to properly tighten the heavier spokes if you use them.

 

[Benjahmin]

Yeh, definitely leaning towards single butted, so 13 g at the hub down to 14g for the spoke.

 

[saneagle]

OK, measured it as 598 +5 = 603 against Ryans way of 602. Near enuf methinks.

Thanks for that. It's well within the boundary of measurement error.

Yeh, definitely leaning towards single butted, so 13 g at the hub down to 14g for the spoke.

I always use straight 14g and never had any problems. You get a better angle out of the spoke holes.

 

[Sturmey]

Yeh, definitely leaning towards single butted, so 13 g at the hub down to 14g for the spoke.

The picture below helps to explain why 14g at the j bend may be stronger than the thicker 13g. When the spokes are newely fitted, there is a gap at the spoke flange. With the lighter and more flexable 14g spokes, this gap disappears when the spokes are tightened and pre-stressed ( checked and re-tightened if necessary). Those stainless steel 13g j-bends spokes are very stiff and have difficulty bedding in at the j bend. This means that there is movement and eventually fatigue at the j bend. This in my view explains why the lighter 14 g spoke may give better service and why I would keep away from 13g (even butted) if possible.

 

[Woosh]

If you spoke a wheel traditionally from scratch with 13 or 12 gauge spokes, you will notice that at the beginning, there is noticeable friction between the j bend and the flange of the motor and also the angle between the nipples and the rim may look uneven. I usually stop several times when tightening the nipples, take the wheel off the truing stand, put the wheel on top of my trusty bin and push the motor up and down several times to loosen any j bend that may not sit well in the flange of the motor. I give a squeeze where two spokes cross to make sure that the nipples are also centered. Flip the wheel over and do same fir the other side. That adds 5-10 minutes to the build time but it's well worth the effort.

 

[Benjahmin]

I see what you're saying but this is taken care of by having the left side spokes (non drive side) with the bend on the inside of the flange, and the right side on the outside. Whilst reducing the triangulation of the spokes to the rim it helps to bring the tensions nearer together.
Grin say that they 'recommend to anyone who will listen' that you use butted spokes with 13g at the bend and 14g at the nipple, for hub motor builds. This also allows for the flange holes of my AKM measuring a consistant 3.2mm with the calipers.
We'll see, if I break any spokes I can come back and say, 'You told me so !' .
I agree, it's amazing how much squeezing, bending and flexing goes on during the process. Even spokes that get bent during lacing end up pulling straight.

 

[Woosh]

It is good to use 13g at the flange and 14g at the rim but those spokes cost a lot more compared to ordinary stainless or anodised 13g for your AKM, especially if you have to buy singly at a later date.

 

[Benjahmin]

True, but what with the motor, battery and panniers full of shopping I'll be asking a lot from the spokes.
Anyway they're now ordered for £31 inc. nipples and delivery. Considering I'm using a rim I've had lying around for ages, that's not too bad.

 

[saneagle]

True, but what with the motor, battery and panniers full of shopping I'll be asking a lot from the spokes.
Anyway they're now ordered for £31 inc. nipples and delivery. Considering I'm using a rim I've had lying around for ages, that's not too bad.

For comparison, my 14g plain stainless steel spokes cost £9.99 from Amazon. They'll be carrying my weight (100kg) + up to 10kg of shopping.

 

[Benjahmin]

Ouch ! I guess I've paid the price of obsessive over engineering.
In my defence, for various stoopid procedural reasons, I can't use Amazon. I've tried, I'm blocked.

 

[Woosh]

I guess I've paid the price of obsessive over engineering

each spoke can hold as much as 200kgs in traction force, so what gives first is not the strength of the spokes but something that caused the spoke to be loosened like the hole in the rim gets damaged or the spoke gets broken at the J bend. It is rare that spokes break in the middle. When the nipple is so loose, the spoke gets put into compression and snaps. It follows from those observations that the tension needs to be even to distribute the load evenly over many spokes, the nipples should not be too tight that may damage the holes in the rim if you hit a pothole but tight enough so they don't get loosened. I use a drop of linseed oil to help the nipples from getting loosened.

 

[saneagle]

each spoke can hold as much as 200kgs in traction force, so what gives first is not the strength of the spokes but something that caused the spoke to be loosened like the hole in the rim gets damaged or the spoke gets broken at the J bend. It is rare that spokes break in the middle. When the nipple is so loose, the spoke gets put into compression and snaps.

Failure mainly comes from metal fatigue in the elbow as a result of not enough tension in the spoke. When you put weight on the bike, the lower spokes go into compression, which puts a bending force on the elbow. 14g spokes are more elastic, so it's easier to keep them in tension all the time, which is probably why I've never seen an elbow break on one. I've seen plenty on 13g and even more (proportionally) on 12g, which is not the result that most would expect.

If ever you hear spokes creaking, it because they don't have enough tension. You must solve that quickly otherwise you'll be finding broken spokes at the elbow.