Thanks for the comments so far
@youngs_modulus, cheers I try to work on the theory that in most situations it is better to think before engaging the mouth or keyboard.
@rruff, Thanks for clarifying my error regarding the shear loading and it actually being a bending load, I have some more questions about this below if you don't mind having a look.
@the other guys, sorry to be blunt but
that was not very polite) please read my original post. I am not considering in any way building a set of wheels in this manner I am trying to work out why I keep breaking spokes on a wheel that has the same spoke count as other wheelsets I own but are not breaking spokes on. The manner in which this wheel was constructed/designed by someone else seems to be the key to the issue (to me at least).
In regard to rruffs the comment about it being a bending load and the root cause being a build or faulty spoke issue I hope the following provides some more information.
I did a quick autopsy on the wheel before I took it back to the LBS and have posted the photo's here: Roval Wheel
I took the step of doing this as the last time a spoke broke the LBS had binned the old one and the nipple befere I got a chance to see them.
The holes in the rims show clearly show signs of the spoke threads wearing against them and excuse the poor macro photos but when you look at the inside of the rim from the outside there is a distinct wear patch from the inverted nipple at only one point in the nipple seat area. I am wondering if this has something to do with the bending load being seen on the spokes where they pass through the rim wall? There is also no sign of any lubricant residue in the nipple seat area.
In regard to the spokes Specialized's website says they are DT New Aero and are 3.0 x 1.5mm bladed straight pulls. I have measured them with a vernier and come up with 3.0mm x 1.3mm, what I find strange is that the tech page on DT's website lists the New Aero as 3.3mm x 1.1mm ?????? so I am not really sure what spokes they are.
The last time the weheel was repaired by the LBS I checked the spoke tensions with a TM-1, on the Drive side the TM-1 readings were all between 14-14.5-15 and on the non drive side all were between 10-11 on the TM-1. I am not sure how to convert these to actual tension readings as the this spoke size isn't in the tables for the TM-1 and I can't find seem to find a formula to work it out (I do recall seeing something on the web but not anymore). I did a comparison with the front wheel and sampled a few spokes on it with the TM-1 which showed readings of between 12-13.