Wheelbuilders / bodgers help – broken flange

(no sniggering)

This one’s a bit harder. I didn’t pay enough attention to the comment joemarshal made and got a bit enthusiastic winding on the spoke tension – this happened to the wheel I was building.

Any suggestions on how to fix this so I can still attach the normal number of spokes? Has anybody here ever fixed a hub with a broken spoke hole in the flange?

I guess with a bike hub you’d just bin it, but the picture has all the information required to work out just how expensive a replacement for that is…

…oh and before anybody asks, yes I did lace it all the right way in the end.

new hub time

given its a unicycle id relace it at half the number of spokes. only work around for that issue imo

1. Drop a spoke
2. Drill a new hole/weld that piece back on – I doubt it will be that strong – perhaps AL can do it for you with a spoon
3. Get a new hub

How much for hub ?I cannot read the hub well and if it is a unicycle I have no idea how much they cost

Is there enough material to re-lace so that spoke is pulling the other way?

That’s the only method I can think of unless you go even more daft with lacing (see my recent thread), or trail rat’s idea.

Of course, if you had a spoon and some carbon…

that hub is borked!

I rebuilt a wheel for a guy who had done the same thing, he’d then welded the piece back on with extra weld around the affected area and as soon as i put any tension into the spoke it simply snapped off again.

At the risk of being shot down, just have one spoke missing. I’ve ridden with one spoke down a few times with no issues (might be luck though).

And I’m sure I’m missing something REALLY obvious, why are there unicycle hubs, why not just use bicycle front hubs?

Seeing as how it’s knackered now, I’d drill it 12mm or whatever it is in from the old hole,countersink and fit a one-off spoke that’s half inch longer than the rest.

And I’m sure I’m missing something REALLY obvious, why are there unicycle hubs, why not just use bicycle front hubs?

cranks attach to it so needs more strength??

the cranks drive the hub unlike a bicycle front hub.

not only that – this is a schlumph 2 speed i think ……

read UBER expensive .

schlum/ph still in business ? might do something of a deal on a hub shell ?

I rebuilt a wheel for a guy who had done the same thing, he’d then welded the piece back on with extra weld around the affected area and as soon as i put any tension into the spoke it simply snapped off again.

that would be because the weld metal is in an annealed(soft)state,but you could weld it up and get the hub re-heat treated?

my god did i read the price corretly!!??

that would be because the weld metal is in an annealed(soft)state,but you could weld it up and get the hub re-heat treated?

he had re-treated it but to no avail

Actually…fabricate a piece of steel with a hole for a spoke that you can bolt in place under those 2 torx bolts.

I WIN!

or drill a spoke hole to the left and use a longer spoke.

cheap as chips option.

cranks attach to it so needs more strength??

the cranks drive the hub unlike a bicycle front hub.

See, I knew I’d missed something. Doh! 😳

al’s plan is not that bad you could use some pretty thick steel there as well

Given the price – for a **** unicycle wheel- I would try almost anything

Actually, guys, we are missing a trick:

It’s COMPLETELY UNREPAIRABLE, AND YOU CANNOT AFFORD ANOTHER. Time to give up unicycling 😛

trail rat has it – yes mathewshotbolt you did read the price correctly, hence why a new hub isn’t an option and I’m happy to try anything to bodge it. I’ve emailed Schlumpf, but I’m not all that optimistic – they are still in business and making these (some have clearly found out how much a new one costs – I thought I’d let you find out for yourself, but for those who can’t be bothered, here’s a link http://www.unicycle.uk.com/unicycle-parts/hubs-bearings/kris-holm-schlumpf-geared-unicycle-hub.html), but this is a first generation one which they haven’t made for years, so even if replacing the outer shell was possible then I doubt the part is available. There’s also lots of gears and stuff inside there, so even if heat treating worked I don’t think it’s an option.

I’m afraid I have another 3 (cheaper) unicycles, so you’re not getting me that easily.

martinxyz – Member
Seeing as how it’s knackered now, I’d drill it 12mm or whatever it is in from the old hole,countersink and fit a one-off spoke that’s half inch longer than the rest

That’s what I would try first.

If not, make a slightly larger stainless steel flange, and use the existing hub holes to bolt it in. Then you need new spokes. But it’s all doable at home with a bit of careful bodging, and much cheaper than a new hub.

I like Cynic-al’s fix, but in reality I’d just build it with one less spoke, assuming the build’s not marginal on strength.

I think the best solution might be to break your other unicycle hubs too.

Several ways to fix that – I’d probably go for drilling another hole.

Bolt a steel plate to the two bolts at the bottom, drill a hole for the spoke in the steel plate and thread the spoke through the hole in the steel plate. Should work.

Would have thought there would have been enough safety margin in that to be a spoke short, the older the gear, the stronger it usually is. They didn’t have fancy cad, dynamic modelling in them olden days. Everything was overbuilt.

I don’t think there’s enough metal to just drill a new hole – as you can just about see in the background, the hub shell is higher the other side of the flange, so I can’t actually get very much nearer the center than the existing hole, and it’s all cut away between the spoke holes. Though it is interesting that’s bencooper’s suggested solution, as he’s the one person on here who I think actually has one of these hubs, so I’ll have another look. Really not at all keen to go with one less spoke, as I don’t want to risk the strength of a wheel which has a lot of load, on which I’m not all that stable, but can easily do 15mph+ on. I’ll have a think about bolting to the bolts you can see in the picture, but I’d really rather not touch them as I’d be messing with the delicate internals.

If not, make a slightly larger stainless steel flange, and use the existing hub holes to bolt it in. Then you need new spokes. But it’s all doable at home with a bit of careful bodging, and much cheaper than a new hub.

I think that’s the winner at the moment. I’m wondering whether it might be possible to just take out the spoke to the left of the broken one and bolt a bit of plate to that hole, as the spoke forces ought to mostly balance each other, meaning very little static load on the existing hole, and the highest loading being due simply to decrease in spoke tension as it’s ridden. Probably a better solution to take out 3 spokes though to spread the load (if I only take out 2, the force won’t be balanced on the plate).

the older the gear, the stronger it usually is. They didn’t have fancy cad, dynamic modelling in them olden days. Everything was overbuilt.

Not actually that old at all – less than 10 years I think, just rapidly superseded. Certainly far from overbuilt, quite the opposite – that’s the whole problem.

Oh, and thanks for all the help.

Another slightly crazy idea – old Penny Farthing spokes didn’t have heads. The spoke started at the rim, threaded into a nipple, went to the hub and dog-legged through a hole, and then out to the rim again.

You’d need to bodge a double-length spoke – I might do it with two spokes threaded at both ends and joined with a long nipple.

Can’t you just ignor it? A wheel will be plenty strong enough with only one spoke missing and you should still be able to get it true enough (guessing no rim brakes on a unicycle?)

Another slightly crazy idea – old Penny Farthing spokes didn’t have heads. The spoke started at the rim, threaded into a nipple, went to the hub and dog-legged through a hole, and then out to the rim again.

You’d need to bodge a double-length spoke – I might do it with two spokes threaded at both ends and joined with a long nipple.

That would be perfect – much the same as the plate bolted on to the existing intact spoke hole I was thinking about above, but a bit more elegant. Still not quite sure how you’re suggesting making one up – where would I get a spoke threaded both ends which was long enough (I think from what you say that one spoke would have to be significantly longer than the current ones)?

andrewh – unfortunately I do plan to have a rim brake – is quite common now on unis with larger wheels. Was rebuilding on a rim with a brake track having just taken off a disc only rim. Would be a lot more comfortable going fast on the downhills if I didn’t have to brake with my legs (bearing in mind my legs don’t spin at the speed I could freewheel at I have to brake somehow on the downs). Apart from that, having a wobbly wheel doesn’t help with stability on a unicycle at 15mph!

Actually I think I’d drill a new hole in the flange. If you file the bottom of the head off the spoke you can drill close to the shell. A whole lot less ball-ache than a plate bolted to the flange.

highest loading being due simply to decrease in spoke tension as it’s ridden.

It increases too!

There were quite a few failures with early shlumph parts iirc. My be worth contacting roger at UDC, they might have some odd spare parts. I think I’d probably just ride it with one less spoke if it is for road riding. If you want a ‘proper’ repair then you could get a new flange laser cut. Basically an annulus with two concentric rings of holes: one set for some m3 bolt to fix into the existing spoke holes and a new set of holes for the spokes. You’ll probably get away with same spokes and it would only cost £10-£20.

Still not quite sure how you’re suggesting making one up – where would I get a spoke threaded both ends which was long enough

Wheel building specialists should be able to roll a thread on to custom spoke lengths for you*. Just get plenty of thread put on the rim end of the folded spoke to give you something to work with, then trim excess spoke off when you’ve got the length right.

* or get one of the longest spokes you can (un-butted obviously, otherwise you could end up with a butted width bent over and sitting in the flange hole). DT Champions available up to 314mm, so bags of spare even for a 29er wheel build. Just get the wheel shop to snip the elbow off and put a thread at that end. Put the bend where you calculate and then get a normal short spoke and again snip the elbow off and have a thread added.

As there were quite a few failures with the internals of these hubs I would expect that somebody would have a shell kicking around. Either that or ride it with a spoke down, it shouldn’t be a problem.

I get custom spokes from Central Wheel in Birmingham – they cut them from big coils of wire so I’m sure if you talk to them they could make you a long bit of wire with a thread at both ends.

If you want a ‘proper’ repair then you could get a new flange laser cut. Basically an annulus with two concentric rings of holes: one set for some m3 bolt to fix into the existing spoke holes and a new set of holes for the spokes. You’ll probably get away with same spokes and it would only cost £10-£20.

Where would I get to make me one of those? I like the sound of a proper repair, and in the context £20 is an absolute bargain.

Wheel building specialists should be able to roll a thread on to custom spoke lengths for you

Any suggestions? That also sounds like a definite plan, and a pretty immediate fix. At the worst it’s definitely preferable to riding with one spoke missing.

Edit: missed ben’s reply when replying myself – Central Wheel could presumably make me a single spoke the right length if cutting from a roll, so that sounds the best plan. Have just spoken to them and waiting for them to get back to me…

Where would I get to make me one of those? I like the sound of a proper repair, and in the context £20 is an absolute bargain.

First draw it in CAD and export as a DXF. Can you do this or know someone who can? Then fire it off to a few laser cutting firms for a price. You need to find one that will do a small order. I have a couple local to me or some will do it all on line and post the piece.

If you get stuck getting it drawn I could probably help, in fact I’m drawing some parts up for laser cutting today.

Price is an estimate but these light plates were £7 each for example, similar size, a few less holes:

Light plates for interactive exhibit[/url]

Bah – Central Wheel say they don’t do 14G as they only do motorbike spokes which are thicker. What sort of custom spokes do you get from them, ben – did I ask the wrong question? I suppose I could go to 13G if they’d do that (I didn’t ask), but it would make threading it through the hub a lot more difficult – 14G has to be preferable.

I didn’t read all the content.

Wheels are in balance, right? Spokes all pulling different ways, but equalling out. So if you’ve over-stressed one point, could there be damage elsewhere? I think it’s worth stripping and inspecting carefully before you spend more time and money on it.

This is the sort of thing I was thinking:

You might have to play with the outer hole positions a little to keep the same length spokes, and the inner pattern is just an approximation.

Bah – Central Wheel say they don’t do 14G as they only do motorbike spokes which are thicker.

I get 14G spokes from them all the time 😉