Custom length spokes and bending your own "J" end

I'm waiting on spokes to arrive via postage and thinking about other ways to adapt spokes for custom length. It's been fairly time consuming to get spokes short enough for a DD motor in a 24 inch rim.

Why there so much discussion about thread rolling machines to customise length, it sounds cheaper and easier to cut and bend your own "J" end to customise length?

I found a youtube clip on the subject: "How to make custom length spokes cheaper"
https://www.youtube.com/watch?v=EYpGvp_7LoU&ab_channel=GONGALAB
The guy seems to have success bending a "Z" into the end of a spoke to customise length. He uses a steel jig with a spoke hole with rounded edges to bend the spoke.

Has anyone tried this method and can share long term experience and longevity?

I'm unsure if how much cold bending a spoke will weaken it. Would it be better to heat it on a flame before bending?

There is also the old thread on here which shows twisting spokes on the hub flange end for custom length. This appears to work fine, but seems weaker given the tighter bend radius at the flange end.
https://endless-sphere.com/forums/viewtopic.php?f=2&t=55667

cloudy said:

Why there so much discussion about thread rolling machines to customise length, it sounds cheaper and easier to cut and bend your own "J" end to customise length?

Click to expand...

That doesn't work at all. If you get your spokes tight enough to do what spokes are supposed to do, they'll pull right on through if they don't have a head to stop them.

If it were that easy, cheap assed Chinese manufacturers would put that stuff on garbage bikes. They don't.

"Z" bend spokes do work in the right application.
On a small diameter hub the extra length of the "Z" sometimes collides with the neighboring spoke.
A larger diameter hub with more room between spoke holes or a radial pattern it works fine.
"Z" bend is bit more common for aero bladed spokes as they can be used without modifying the holes in the hub.

https://wheelfanatyk.com/blogs/blog/z-spokes-all-you-need-to-know

PaPaSteve said:

"Z" bend spokes do work in the right application.

Click to expand...

They don't, unless "the right application" includes leaving your spokes too loose to do their job, and not stress relieving them at the time you build the wheel.

The exception is "Siamese spokes", where a single spoke passes from the rim, through one hub hole, back to another hole in the rim. Because the spoke is equally tight on both sides of the hub flange, it won't pull through.

Thanks for the responses. The wheelfanatyk page is great, all I needed to know!

For clarity, I am asking about the the use of a Z-bend (as in the video and wheelfanatyk link) to replace the normal J-bend and forged head on a manufactured spoke.

My gut feel is that the threads on the spoke nipple would strip before pulling a z-bend through the hub flange. I suppose I need to try it to find out, but was wondering if anyone has attempted it on a motor hub already. What works on a lightly weighted road bike wheel may not work for an E bike due to the higher loading and torque of the motor.

I'm no manufacturing expert, but doubt forging a head is much more expensive than doing a Z bend. A forged head is also more versatile and will work for more flanges. The only reason I'm asking about z-bend is because I have loads of long spokes on hand, and nothing short enough to fit a hub motor and 24" rim.

I've edited my post to use the correct terminology for spoke head and spoke nipple. Hope it makes more sense now.

I have not seen the Z-bend method before, so I have no experience with it. However, at some point I will need to build up some wheels, and if I have a way to build a tool to make the Z-bends (there are howtos online here and there) then I'd be willing to test out the idea. I don't have much in the way of old wheels anymore to reuse spokes from, but I have enough to test out the idea on at least one wheel, probably a pair of them, to use on my heavy-cargo trailer, or even on an alternate version of the rear end of my present SB Cruiser trike, either of which should abuse them enough to see if the idea works for my usage.

If the hubs I have to make the wheels from can't use them due to length of Z, I can make my own hubs to deal with that (for the new trike wheels I would have to make them anyway, since I will need single-ended axle type hubs that slide onto a trike-mounted axle).

The only "Z" bend spokes I've used were off the shelf aero shape. Hoshi brand.
They worked the same as a "J" bend spoke without the hassle of modifying the hub.
Being an experienced fabricator it would be a simple task to create the tool to create the bend.

cloudy said:

I'm unsure if how much cold bending a spoke will weaken it. Would it be better to heat it on a flame before bending?

Click to expand...

Hi Cloudy,
I was confronted with the same issues you are contemplating now when mounting a Magic Pie V5 to a rear rim.

See my wheel build process here...
https://electricbike.com/forum/foru...t-52v-11-5ah-huffy-parkside?p=50920#post50920

At the time I was unsure how much to depend on a spoke calculator, and my measuring in the process for accurate results.
The expense of a thread roller seemed a bit much for perhaps a onetime use. So why not go the new J-bend rout, forging the new tips, all factored into the needed new lengths.

See the specifics during build here...
https://electricbike.com/forum/foru...t-52v-11-5ah-huffy-parkside?p=51586#post51586

First, I want to start with the results.
With your access to many spokes, you will not be under as much pressure to make every spoke count. As such I miss-measured and cut one too short, and one other broke during the initial spoke tightening procedure. So, I had to buy two spokes made to length for replacements.
After the initial break in period of a couple months. They settled in nicely, and to this day have not given me any problems whatsoever. My biggest regret is that I did not re-paint them before installation. Thinking that they probably would be just temporary until the store-bought ones were ordered and received. But that hasn't happened yet.

Is it worth it?
I probably would not recommend it to others. As I found the calculator to be quite accurate. And the unknown levels of people's skills, and uncertainty of getting it getting it done well enough to prevent failures is high.

But over-all it can, and has been done!

Be glad to provide better detail than offered in the build thread if you're interested in FORGING in FIRE! :lol:








Regards,
T.C.

Wow ... forging a new head ... that's a hot tip ... pun intended :lol:
Applauding the creative process.
Sort of wondering how much the metal's grain structure changes due to the heating ?
A higher tensile strength material often suffers a fair bit of strength loss after heating.
But ... hey, I see you made these spokes in 2017 so if they are still in use, it must be fine.

Wow I'm impressed you worked out how to forge your own heads T.C. I think I'll try the Z bend method at some point, it seems a useful way to quickly repair a wheel. Can anyone say if heat treating a stainless spoke after bending is beneficial? Also is heating prior to bending better than cold bending? I've heard pickling stainless after heating may improve things. This question comes up a bit for glue in U bolts used in rock climbing (my main hobby), these are bent cold from 8mm Stainless rod. I've often wondered if heat treatment would improve corrosion resistance/strength after bending.

Back in the day ...
... when we did engineering drawings by dragging a sharpened piece of carbon across a sheet of velum
... when most quality fasteners used in the US were actually produced in the US
I worked as a tool and die designer for a fastener manufacturer. Most fasteners are "cold formed". Only large fasteners were "hot formed" (5/8 inch structural and larger high strength grades). Likewise only high strength fasteners were heat treated .... the common ones (like you buy in hardware stores and home stores) were cleaned, coated/plated and shipped.

It is common practice to cut spokes to length and roll thread them. That implies that the material is malleable (still in at least a partially annealed condition). It should be possible to produce a tool set that someone could use to cold form "new" buttons on the end of spokes. The problem would most likely be the same as in heading a long bolt ... getting a sufficiently strong grip on the shaft. Considering in this case how long the shafts are that should be doable.

One is not likely to produce such a tool set in their garage because such tools "should" be made from tool steel and depending on the material chosen might require heat treating. However it should certainly be considered a viable alternative to roll threading.

LewTwo said:

It is common practice to cut spokes to length and roll thread them. That implies that the material is malleable (still in at least a partially annealed condition). It should be possible to produce a tool set that someone could use to cold form "new" buttons on the end of spokes. The problem would most likely be the same as in heading a long bolt ... getting a sufficiently strong grip on the shaft. Considering in this case how long the shafts are that should be doable.

Click to expand...

A perfect description of why a cold formed "Z" bend works.
The head of a typical "J" bend spoke is roll formed in much the same way as the threads are roll formed.

So...I get to test this Z-bend idea out way sooner than I wanted to:
https://endless-sphere.com/forums/viewtopic.php?f=2&t=67833&p=1736417#p1736417

https://endless-sphere.com/forums/download/file.php?id=324880



I thought there was a post here showing the design of the tool to make the Z-bend with (so i can make one)...but I don't see it or a link to it now. Any ideas before I just start googling?

amberwolf said:

So...I get to test this Z-bend idea out way sooner than I wanted to:

Click to expand...

What happened? Foreign object damage?

I don't know exactly what happened, everything was normal, then it wasn't. Nothing in the road, so nothing to have gotten into the spokes, just BANG and...that. (see the link in the post above for more details).

The only time I've seen spokes break at the thread ends the spoke and the nipple were not collinear.
Or to say it in a different way ... the spoke exited the nipple at an angle.
From your picture it doesn't look to be the case here.
Larger spoke gauge, more spokes or change of spoke brand ?
Link to homemade or purchased "Z" bend tools are in post 1 and 3 of this thread.

That's a messed up wheel failure AW! I'd probably rebuild the whole wheel with new or different spokes.

The spoke angle looks pretty close to 90 degrees in your wheel. Is it better to use slightly longer spokes to have a more acute angle where they enter the rim? Somewhere between radial and 1 cross pattern. Ive never done this but seems like others have.

The jig for bending z bends is in the video linked in first post of this thread. Im keen to hear how you go with it.

Interesting to note that it was the "inside" spokes that broke ... perhaps a clue to the reason ?

LewTwo said:

Interesting to note that it was the "inside" spokes that broke ... perhaps a clue to the reason ?

Click to expand...

This creative vehicle looks to be rather weighty for the spoke count in the wheel.
Low spoke count combined with some sort of side load likely contributed to the failure.

FWIW, none of the other hubmotor wheels I've used (built by me, unlike this one) on this trike have had this kind of problem, even when I've been unable to avoid some serious potholes that damaged the rim (completely crushing the rim wall down to the inner rim surface (where the rim tape covers the spoke nipple holes), and even one impact that broke the motor axle itself (separate from the times the axles were broken by motor torque).

So it's something specific about this OEM A2B Metro rear wheel itself, either the length of the spokes (threads not fully into nipples) or the quality of them (manufacturing problem?) or even some prior stress the wheel experienced before I got it. Perhaps it's even the rim itself, though I doubt it: this is an Alex DM32, while the ones I built my wheels on are some unmarked 50mm eyeletted doublewall rims that were NOS ex-Zero rims from back when the Zero started out kinda more like a high-powered electric bike vs a motorcycle.

I think these broken spokes are 12g, maybe 13g. Don't know what brand.

They're all 36-spoke wheels. I've used the Sapim 13/14 butted from Grin Tech for some of my builds, and the straight 13g from them for a couple of others. I have had a couple of broken spokes (three? four?) one at a time over the last several years on different wheels, which is normal in my experiences for the kind of heavy cargo hauling I do and the road conditions and whatnot (back before I electrimotorificated my stuff, even my regular bike wheels broke the occasional spoke with this kind of loading).

There is definitely sideloading during turns, but as noted before , it hasn't been a problem with other wheels that I've run much much longer than this one (this has only been on there since the end of April this year... the other one I built with the same kind of motor on the ex-zero rim has been used since June of 2019 (and is presently back on there now as it's my only functioning spare motor wheel that fits the trike. Some pics from back when I built it
https://endless-sphere.com/forums/viewtopic.php?f=2&t=67833&p=1477114&hilit=stromer#p1477114 ; note the damaged rim I used to build it (not really by choice, had to change the motor because of motor problems but didn't have a rim for this new motor); I have a new rim to replace that with...eventually.


And while I'm very glad that none of the outboard spokes broke, I am surprised that it was only the inboard ones (all of them except four around the valve stem area).


Also...I've never experienced a simultaneous failure of more than a handful of spokes, and that was from (IIRC) a stick in a regular bike wheel, ages ago (and all the spokes involved were seriously bent, where all of these are straight except for one that has jammed itself between the rim and the flange and the load on it bent it).

The worst hubmotor problem was way back on CrazyBike2 with a crappy OEM generic hubmotor wheel with crappy rim and their too-thick spokes with the predictable results that spokes started breaking because of the cracking rim around the nipple holes, but they only broke one at a time (even though I lost several during just one ride, before I could replace the rim and spokes with correct ones).


This is a wierd one.....

What is the weight of your creation ?

Too much--it's a few hundred pounds. I don't have a current measurement, but with my almost 200lbs on it, and my tools/daily work stuff, etc., it's probably getting up around 600lbs, and most of that is on the rear end, and just in front of it at the seatbox area. Not much is on the front wheel.

(A future version will use much larger pedicab rear wheels moved farther back to more evenly distribute the load and give a better ride, but the present version is what I have to work with for the foreseeable future).

No where near enough spoke density for the task.
Either increase the spoke diameter or spoke count.
With radial lacing it's super easy to hand drill the hub and rim to double the volume of spokes.

Curious: Why does it work for the other wheels then, with no even remotely similar failure? I have a difficult time believing it would be blind luck, not for this long.

It's much more likely to be something insufficient about these specific spokes, or the wheel build itself, or it's prior stresses before I got it.

Increasing the spoke diameter (assuming these are already 12 or 13g) would be a problem because the rim would not handle the tension required, and I'd be right back to the same problems of the too-thick spokes of OEM hubmotor wheels that did fail easily (where the thinner spokes don't).

Increasing the number of spokes wouldn't be too tough if it becomes necessary, but it has not been so in the past with any other similar wheel--just this one has had this problem, for no "obvious" reason. It has not even seen anywhere near the amount of stress any other similar wheel used on here has seen; not the same loading, distance, torque, impacts, etc--the four primary differences I can think of ATM are that it used a bigger softer tire for almost all of my usage of it, it uses a narrower rim, it uses different spokes, and it wasn't built by me.

I would need to get a new spoke nipple tool, as the one I have couldn't be used properly in a double-density-spoke wheel (at least, not with my hands).


I still need to disassemble the rest of the wheel to see how the stuff that didnt' fail was setup, and examine the broken remains of the rest to see if they are different; I'll post pics in the previously-linked SB Cruiser thread along with my speculations and conclusions.


For now, unless something in the failure analysis leads me elsewhere, I think I will just respoke it as-is, but into one of the two new ex-Zero rims Chalo sent me (because they're a little wider than the Alex and easier to get the Shinko tires on and off of without worrying about pinching the tube), ensuring the threading is fully in the nipple body as it should be, etc.


FWIW, I did use some regular bike wheels (not built by me, just prebuilt from a generic BMX) with many more spokes early on in the trike's existence when it was much lighter and only a front hubmotor, and they didn't work out very well (for various reasons probably not related to the number of spokes).
https://endless-sphere.com/forums/download/file.php?id=163855

First, they were singlewall rims, so not as strong. One was damaged due to a curb strike
https://endless-sphere.com/forums/viewtopic.php?f=2&t=67833&p=1033691&hilit=spoke%2A#p1033691
which caused further problems later
https://endless-sphere.com/forums/viewtopic.php?f=2&t=67833&p=1045919&hilit=spoke%2A#p1045919

Not too long after that post I speculated about possible issues with lower spoke counts
https://endless-sphere.com/forums/viewtopic.php?f=2&t=67833&p=1034847&hilit=spoke%2A#p1034847
but after having not had the problem I expected...I stopped worrying about it.