Spokes keep op breaking

remichi · Aug 23, 2012

Just had a look at my rear wheel and turns out 6 spokes are broken on the engine sprocket side!

First time I installed the sprocket I broke 2 spokes by tightening too much. Got spokes replaced and next tightened it much much less, but still it seems that the spokes can't bear the stress.

It's a 28 1 1/2 inch 40 spoke wheel as used in India and China on the old style roadster bicycles. The engine sprocket has 5 holes.

I'm flying to the Netherlands from Kenya next week so I'm thinking of all the supplies I should bring back to Kenya.

What is the thickest spoke available for 28 1 1/2 inch wheels? Is there another way of mounting the sprocket?

At the moment I have:

Bolt - rubber - sprocket - rubber - wheel - rubber - 2 metal half circles - washer - nut

Somehow the pressure on the spokes is way too much, also see on the bolts that the thread is disappearing, meaning the spokes rub against the bolt.

Supplies are scarce in Kenya as well as in the Netherlands, so hopefully someone has a kind of DIY solution.

http://www.bit.ly/kenyanbicycles

Bikeguy Joe · Aug 23, 2012

Should be- Bolt through the sprocket, then rubber, spokes, rubber, metal half circles, washer, nut.

I am guessing that the extra rubber on the outside of the sprocket is causing too much flex and that's why your spokes are breaking.

Venice Motor Bikes · Aug 23, 2012

Using a wheel with thicker (12ga) spokes will solve the problem, or you can use a 'hub adapter'.

MotorBicycleRacing · Aug 23, 2012

Venice Motor Bikes said:
Using a wheel with thicker (12ga) spokes will solve the problem, or you can use a 'hub adapter'.

hub adapters probably won't work with 40 spoke wheels.
3 x 13 = 39

The original Chinese engine kits came with 5 hole sprockets
because the bicycles in China used 40 spoke wheels.

5 hole sprockets didn't work with 36 spoke wheels so the kits
changed to 9 hole sprockets.

Bikeguy Joe · Aug 23, 2012

If the OP mounts up the sprocket and rag joint the way I described, he should no longer have the problem of spokes breaking.

remichi · Aug 28, 2012

Will try the other way. First going briefly to Holland to get visa for Kenya sorted.

Ordered new carb on ebay, hope it will arrive on time to take it back to Kenya with me. Will also buy some lock nuts in Holland so I don't keep losing them.

So as I understand a 9 hole sprocket won't fit on a 40 spoke wheel right? They don't have 36 spoke 28" wheels here. And taking a wheel in my suitcase will be difficult...

bigbutterbean · Aug 28, 2012

Is it possible to buy a regular 26" bike with 12g spokes and 36 hole hub? surely in holland or the netherlands you can find one of these type of bicycle and have it shipped back to you in kenya or even check it on the plane? maybe not the cheapest solution, but will certainly save you trouble down the road. you could then also use a hub adapter.

remichi · Oct 26, 2012

Well I'm back in Kenya after a short stay in Holland. Motored bike was doing fine until today when the wheel gave way because too many spokes had broken again.

I have fixed the sprocket as Bikeguy Joe had suggested and it was fine for about a month. Now it turns out 12 spokes on the left side had snapped. Too much force on the spokes. The Kenyan bumpy roads also really aren't helping, but they're one thing I cannot change.

So my next solution is to make my own hub adapter somehow. Seeing that it is a 40 spoke wheel with a sprocket of 5 holes. Has anyone made their own hub adapter and what are some tips? Mind you, half of the tools I'd like to have here are not available to me.

PAracer · Oct 26, 2012

Without a mill, making your own adaptor is going to be difficult.

I see two options:
1. Make up some drawings and have a machine shop do the work.
2. Find a set of 36 spoke wheels and use one of the existing adaptors on the market.

BigBlue · Oct 26, 2012

The Flying Pigeon,

The wheel is too weak and the spokes are going to keep breaking. A 28" 36 spoke wheel is available here in the USA that would help, but probably too expensive at $30.00 per wheel to ship to Kenya. Then you'd have to buy a 36 hole hub. They only have 14 gauge spokes at that. You could then mount a 9 hole sprocket.

As far as I know, no one has handmade their own hub adapter. Doesn't mean it can't be done, it would take some time and ingenuity. The adapter sold on this forum are machined. Look at the Sportsman hub adapter. He is one of the forums sponsors. A link is on the top left hand side of the forum.

Good Luck,

Chris
AKA: BigBlue

2door · Oct 26, 2012

With a little ingenuity and a couple of dollars in parts you can make a sprocket/hub adapter by using a rear wheel with a disc brake mounting flange.
This one has a couple thousand miles on it and no problems but then Colorado roads are probably better than the ones you ride. Not by much, but better.

Tom

remichi · Oct 26, 2012

Thanks for all the input.

I wanted to take a 36 spoke coaster hub from Holland with me to Kenya but seeing that all the strong metal rims here are 40 spoke, I decided against it. Maybe I should've though...

2door, could you send me more and larger pictures of your setup?

Getting it machined here is not an option, have not seen any shops here that might do that kind of thing. Also the eye for detail here is sometimes lacking a little bit.

I have an unused 40 spoke wheel here with a slight dent in the rim. I might try and somehow make an adapter or something. The sprocket has 5 small holes and 5 big holes for beauty which prevent me from drilling 5 extra holes to make it 10 in total. Another problem of course is the fact that I can't weld the sprocket or the adapter to the wheel as I have to be able to disassemble everything to replace snapped spokes.

remichi · Oct 26, 2012

I find it strange that nobody else is having spoke problems. When it comes to people considering a hub adapter or a spoke clamp, I only read about the chain going of the sprocket and nothing about broken spokes.

Is it a combination of bad Kenyan roads and a 40 spoke/5 hole sprocket in my case?!

PAracer · Oct 26, 2012

I'm going to guess that it has to do with the 5 hole sprocket. I don't think 5 holes is enough to tightly clamp the ragjoint together.

You could try lashing your spokes together where the criss cross. You can use wire, or zip ties for this. It's an old trick to increase the strength of a wheel.

remichi · Oct 26, 2012

Thanks for the advice PAracer, I did lash the spokes together with 5mm thick tie wraps last time but that did not seem to help.

Dave31 · Oct 26, 2012

remichi said:
I find it strange that nobody else is having spoke problems. When it comes to people considering a hub adapter or a spoke clamp, I only read about the chain going of the sprocket and nothing about broken spokes.

Is it a combination of bad Kenyan roads and a 40 spoke/5 hole sprocket in my case?!

Had a problem a few years ago with spokes breaking. Once I realized they keep breaking in the same place (Spoke head) I found the problem. Was nothing to do with the wheel or spokes it was the hub causing the spoke heads to break off.

Once I replaced the hub with a new one, had no more problems.

BigBlue · Oct 26, 2012

remichi,

Might be best to setup a jackshaft to drive the front chainring - eliminate the problem of spokes and mounting a rear sprocket. Something like a shift kit from Slick. You'd need a shaft with a couple of sprockets, design a mount and some chain. If a single speed, the pedals would turn as the engine is running. Or put a freewheel sprocket on the jackshaft. if you have a 3 speed with a rear freewheel then the pedals wouldn't turn while the engine is running.

Second thought a freewwheel on the jackshaft would still cause the engine to turn the pedals, but would allow you to pedal with the engine off. I think the 3 speed freewheel wouldn't stop the engine from turning the pedals.

Another possibility would be to make your engine a rear drive friction. Make a mount like the Dax or Staton with 2 tubes to mount the engine which would drive a friction roller. The roller would drive your tire.

Just check your hub really good and make sure it is not broken or cracked.

Just ideas,

Chris
AKA: BigBlue

2door · Oct 26, 2012

Here's the parts I used. They mount onto a standard (iso) 6 bolt disc brake hub starting from left to right.
1. 'O' ring to act as a spacer
2. Sprocket with center cut out to match shape of hub ( I ground out that shape with a Dremel tool and a metal cutting burr)
3. Rubber donut from kit rag joint
4. Adapter to take the six brake hub screws and three that go through the sprocket.

Hope this explains it.

Tom

Roadkill · Oct 28, 2012

I agree with the mill/machine shop stuff. Some machinist there somewhere I bet. Another thought is that Staton-inc custom builds 12g spoke wheels with custom hub and sprocked. I think sprocket is 410 chain and it might be of some use. They offer CNC machining services as well.

remichi said:
Has anyone made their own hub adapter and what are some tips? Mind you, half of the tools I'd like to have here are not available to me.

remichi · Oct 28, 2012

I decided to start by filling the 5 existing holes in the sprocket and drilling 10 new ones. Then make new rubber and also the metal clips on inside of wheel.

That'll be the quick fix, I'll think of a more permanent fix later.

The bicycle taxis here in Kenya also have 10 bolts through the sprocket I noticed in a picture.
(http://www.flickr.com/photos/michisunited/6957926536/in/set-72157629595539665) Those taxi bikes take lots of passengers every day so the extra 5 bolts through the sprocket should help I think.

2door · Oct 28, 2012

Wow, remichi, loved the videos. Funny, the Chinese 2 strokes in Africa sound exactly like they do in the states

Great photos and vids. Thanks for sharing.

Actually the sprocket photo you posted looks like the typical 9 bolt setup supplied with most kits today. They are compatible with all 36 spoke rims.

Good luck with your sprocket problem and please keep us informed about how things work out for you.

Tom

Spokes keep op breaking

New Member

Godfather of Motorized Bicycles

Custom Builder / Dealer/Los Angeles

Well-Known Member

Godfather of Motorized Bicycles

New Member

Active Member

New Member

New Member

Member

Moderator

Attachments

New Member

New Member

New Member

New Member

Active Member

Member

Moderator

Attachments

New Member

New Member

Moderator