Broken spoke ...

[Spoked Wheels]

4 of my bikes have got 36 spoke 4 cross lacing on the rear wheel and there is another 'spare' wheel the same, best pattern for strength/longevity.

Do you have any proof?

 

[speccy1]

Bloody expensive way of life this if wheels just randomly give up the ghost! I wasn't off roading or anything!!

It shouldn`t happen, you must have a duff wheel to start with, it does happen

 

[raleighnut]

Do you have any proof?

Only the advice of John at Bob Warner Cycles who builds my non-standard wheels (a few of my bikes have 'off the peg' wheels) and he has been building wheels since before I was born. (I'm in my mid 50s) John was given the shop when Bob retired and he now runs it as a 'one man band' although John himself is now well past retirement age.
4 cross is a tandem spoking pattern and is usually used on 40 or 48 spoke wheels but will translate to a 36 and he reckons it is better for carrying heavy loads or pulling a trailer because it allows more flex and avoids the 'overload' tension snapping a spoke.

 

[Spoked Wheels]

Only the advice of John at Bob Warner Cycles who builds my non-standard wheels (a few of my bikes have 'off the peg' wheels) and he has been building wheels since before I was born. (I'm in my mid 50s) John was given the shop when Bob retired and he now runs it as a 'one man band' although John himself is now well past retirement age.
4 cross is a tandem spoking pattern and is usually used on 40 or 48 spoke wheels but will translate to a 36 and he reckons it is better for carrying heavy loads or pulling a trailer because it allows more flex and avoids the 'overload' tension snapping a spoke.

4 cross is a tandem spoking pattern? Yes, I agree with that. Most 36 spoke wheels are not tandem wheels so why would I use a pattern that offers no benefit on a standard wheel? In fact, it makes the wheel less stiff or flex more.

is better for carrying heavy loads or pulling a trailer because it allows more flex and avoids the 'overload' tension snapping a spoke? Spokes patterns have no effect on the strength of a wheel. Number of spokes and tension do. Why would it be better to pull a trailer? If a 4 x pattern flexes more then surely that makes it harder to ride as it could rub the brake pads when flexing. Spokes don't just snap, spoke fatigue is very likely be the reason why the spokes brake. Having said that, longer spokes like in 4 x pattern, at least in numerical analysis, have lower strain under large lateral load (Henri P. Gavin) - it might be that in 4 x patter the spokes take longer to fatigue, I'm not entirely sure this is the case when pulling a trailer though.

Jobs Brandt who wrote "The Bicycle Wheel" which has become the "Bible" for wheel builders, says the larger the number of spokes on the Load affected zone the greater the load the wheel can support. In other words, more spokes = greater capacity to support load. The spoke pattern has nothing to do with the strength of the wheel.

Henri P. Gavin wrote an interesting paper "Bicycle Wheel Spoke Patterns and Spoke Fatigue" and he concluded that 4x pattern offers more flex than 3x or 2x, He also concluded that " The spoke pattern affects the over-all radial stiffness of the wheel more than it affects the spoke strains" in other words the spoke pattern makes little difference to the fatigue life of the spoke.

My conclusion is the same as before, why would I build a standard 36 spoke wheel in a 4 x pattern when a 3 x pattern would give slightly more radial stiffness and offer no advantage in strength and life to fatigue?

 

[Yellow Saddle]

Only the advice of John at Bob Warner Cycles who builds my non-standard wheels (a few of my bikes have 'off the peg' wheels) and he has been building wheels since before I was born. (I'm in my mid 50s) John was given the shop when Bob retired and he now runs it as a 'one man band' although John himself is now well past retirement age.
4 cross is a tandem spoking pattern and is usually used on 40 or 48 spoke wheels but will translate to a 36 and he reckons it is better for carrying heavy loads or pulling a trailer because it allows more flex and avoids the 'overload' tension snapping a spoke.

Hmmmm. The number of crosses have nothing to do with flex or avoiding overload tension. Flex is only dependent on:

1) Spoke diameter
2) Rim weight (and thus strength)
3) Spoke bracing angle (hub flange width)

The OP's spokes broke because

1) They were straight-gauge instead of double butted.
2) The spoke line was not corrected by the robot/sweatshop worker who built the wheels.
3) The wheels were not stress-relieved by aforesaid builder.
4) The OP is heavy and the lthus reduces the wheel's lifespan.
5) The wheel could do with 4 more spokes but 32 would have worked had the first four factors been satisfied.

 

[S.Giles]

...why would I build a standard 36 spoke wheel in a 4 x pattern when a 3 x pattern would give slightly more radial stiffness and offer no advantage in strength and life to fatigue?

In my case it was for the somewhat prosaic reason that the spoke size required for three-cross lacing (254mm) was not available from my chosen supplier. Going with four-cross allowed me to use 264mm spokes instead. I don't worry my little head about factors such as the relative radial stiffness or strength of different lacing patterns.

 

[Yellow Saddle]

In my case it was for the somewhat prosaic reason that the spoke size required for three-cross lacing (254mm) was not available from my chosen supplier. Going with four-cross allowed me to use 264mm spokes instead. I don't worry my little head about factors such as the relative radial stiffness or strength.

That's a perfectly valid reason, and like you say don't worry about the other stuff. BTW, there is no increase or decrease of strength or stiffness in 3 or 4 crossings. It is all in the mind of some builders who come up with these claims without any backup.