BPM Wheel Failure

[Scottyf]

This morning on my standard run to work I managed break my rear wheel.

I done this by travelling nearer to the kerb than I usually do and wasn't looking for a split second when I hit a huge pot hole.
Front wheel is ok due to no real weight being over the front.

Rear on the other hand I hit with an almighty thud. Following that I felt the rear wheel become wobbly as if a couple of spokes had loosened and then took a steady corner where the rear wheel wobbled further ripped the tire of and the tube.
Massive failure within the space of about 5 meters at the low 20mph speed.

Stopped to have a look and I managed to bend 2 spokes and snap 3. I've not had chance to review which sides had sheared off. Chewed up a rear tire and a rear tube.


Managed to Nurse the bike to a friends a mile away who was able to take me the rest of the distance to work. (Only another mile).


So as far as wheel building from BMSBattery goes its not been brilliant - But it was cheape and the rims are still double walled decent quality. But the spokes and the build was a bit ropey.



So based on this does anyone know what spoke length and size I need to fit a 700c wheel please. I will begin rebuilding ASAP.

 

[vhfman]

Hi Scottyf, I am sorry to hear of your wheel problem.
If your rim is still OK for the rebuild then you can measure the spokes you have at the moment. If not then the spoke length depends on the Effective Rim Diameter (ERD) of the rim, the hub spoke hole diameter and the number of crosses of spokes in the wheel build. The Bafan BPM hub spoke hole diam is 168mm, spoke gauge 12/13 36h, the original wheel will be 13G spokes. I see from the BPM technical manual that for 700c rim 240mm length spokes are used for the particular rim they suggest; I think that will be a 2 cross spoke lacing.
But as I say, it depends on the state of you original rim, and if it has been damaged during the drop into the pothole, and ride on the road afterwards. I hope you can find a supplier for the 13G spokes in the lengths you require. I think you may have to get them custom made for the specific length.

Chris

 

[Scottyf]

Thanks for the heads up on the figures. I'll take one out and have a look and measure it.
I believe the rim is ok. But again I'll take it apart and have a look and replace as needed.

What you have detailed sounds about right. Same spoke pattern etc..

I'll let you know how I get on!


For now though I'll be unpowered!

 

[flecc]

Here's two spoke length calculators that have been published in here previously Scotty:

Spoke Calculator 1

Spoke Calculator 2

and here's an extract from the recent post by Just1bike who both build wheels and make spokes to order on a top quality thread rolling machine, including 13 gauge:

We're in Maldon, on the Essex coast about 10 miles from Chelmsford.
I can be contacted via: just1bike[at]gmail.com Skype name: catsnapper

Here's his post link on the equipment and spokes spec.
.

 

[Scottyf]

Spoke Calc one doesn't work =-(

 

[flecc]

Thanks for the tip Scotty, I hadn't tested them, just passed them on from past posts.

The new issue of VeloVision has yet another supplier of short length spokes made to measure:

Yourspokes: 07917 698749

 

[Scottyf]

Just to keep you all updated I have pciked up my bike and removed all spokes from the motor bpm hub.

On inspection I've took out 7 spokes in total.

I've been in contact with Alan @ Just1bike where I have sent off 3 of my spokes with nipples to get a replacement of 40 spokes at 13g DT swiss. Hopefully the quailty of these spokes wil lbe much better.

I will be re-building the wheel myself. I've sent 3 spokes to Alan to measure to make sure I get the correct length. With my metal ruler the spokes do appear to be 240mm exactly but since Alan has the correct tools I might aswell have his professional eye take a gander and await the communication.

Either way the rim is still good, no cracks and still in good shape.

All in all it will have cost £14 for custom dt swiss spokes with nipples and probably a couple hours of my time rebuilding the wheel.

Hopefully when I get them all back on the road the wheel will stay nice and true and not need adjustment every couple of weeks.

 

[piotrmacheta]

Does anyone know if spokes can be re-used? If I wanted to swap a rim can I re-use the original spokes or does the re-tensioning mean that they are weakened? Similarly in Scottyf case, do you need all new spokes as the others may have been overstrained.

 

[Scottyf]

I dont really know but for the cosr I just replaced the lot. Least that way they will be all the same make etc...

I think you could reuse them providing the threads and pins are not damaged.

Metal does stretch etc but not by that much ...

 

[flecc]

Expert opinion is usually that spokes should not be reused, the stretch of the rolled threads being the stated reason.

I have reused old ones as single replacements at times, but always built with all new.

 

[Scottyf]

To keep you updated I hated using public transport for the past couple of days in the working week. So while the bike is awaiting spokes and for me to re lace it once I have the spokes, I decided to just get a puncture repair kit. A cheap free wheel cassette And started removing all the electrical vile
Parts.

I'm going to brave cycling to work unassisted. Hopefully the electric bike has served my fitness well these past few months and hopefully ill be able to make it to work without passing out.

The bike feels nice and light and hopefully on the flat
My top speed will imProve. I'm not expecting memo completethe journey in 30mins but if I can do it in say 40mins I'll be a happy boy.

Who knows it it's not that bad I might ditch electric all together ... He says with some optimism.


I'll let you know how I get on.

 

[Scottyf]

Double Entry

 

[Scottyf]

Just to keep you all updated...

Spoken to Alan @ Just1bike who has been able to dish my spokes ready for the wheel build and communication has been superb!!!

I can not recommend him enough!

I will Add pictures once I recieve the spokes which should be today.

 

[Scottyf]

Pictures as promised

Spokes

Wheel start build

Finished wheel

 

[flecc]

Nice one Scotty, quickly done too!

 

[Scottyf]

Feels really nice too.
Not as perfect as my non powered standard hub. But the wheel is double walled and heavy as standard.

I did manage to bend one spoke while putting them all in. However its all holding up well so far.
I also feel that now I've removed the rack and battery of the rear of the bike it should give the bike better balance and not put to much stress on the rear wheel with weight.