XCProMD wrote:Any idea of that T1SL reliability?
The limits with titanium and steel are fatigue and buckling. In the case of Ti add deflection.
At 2E6 cycles the fatigue resistance of a well executed fillet weld in Ti is around 60MPa. Mitering is crucial as root propagation is something you don't want. A good weld has to crack from fatigue from the toe.
The load spectrum on a bike depends a lot on the user. A pro can beat a thin Ti frame in very little time. The first crack is usually the toe of the weld of the bridge joining the chainstays or the toe of the weld between right chainstay and dropout. MTB's crack at the seat tube-top tube junction as well.
The thinner you go, the higher the stresses are in the material, and as I said, there is only a number of cycles a Ti weld can withstand above 60MPa
I can't see why the 1000g T1SL shouldn't be reliable.
I know the legandary sub 800g Ghiasello from the early 00's where neither reliable nor duarble - but in 2006/2007 Merlin/Spectrum was able to produce the Tom Kellog designed CR Works range weighing 1050-1300g (from small 6.4 to XL 3/2.5) that where very reliable and hyper durable.
I have a the 2006 Merlin CR 2.5/3.5 in size ML (equivilant of a size 55-56cm non-compact).
The frame weight is 1115g, the ti 6/4 version was only 1080g. Both framesets used non butted tubeing, both frames where 'mass produced'. You can hit it with a large hammer and it will survive; you can throw it directly into an airplaine without a soft or hardshell suitcase and it will survive, you can crash it and it will survive.
Its sufficiently stiff when ascending and decending the Ventoux with a 95kg rider and 10kg of luggage (credit card touring). It even fits 27mm Pave tyres.
Its been 10 years since Spectrum/Tom Keollog designed the Merlin Works CR range and today you should be able to save additional weight and increase stiffness even further by incorporating:
PF30 BB shell
A milled tapered headtube design
Different dropouts
A lighter aluminum deralliuer hanger compared to non-replaceable TI hanger.
Butted tubing instead of plain gauge (sensible for racing, not for a do-it-all & last-forever frameset)
- add to it that the CR Works range had relatively long chainstays, a beefy brake bridge and a brigde in the chianstays where additional weight can be saved.
The tapered plain gauge size specific top and down tubes Tom Kellog designed for Merlin in 2006 is still state of the art as of 2015 and the reason why he could design a durable high perfomance lightweight frame
Tom owns the intelectual property which is why neither Seven, ABG (Litespeed, ex Merlin) or Competitive Cyclist (todays Melin) can use those tubes - today only Specrum can use them.
But 10 years has passed and im sure it can be improved (especially for racing) if the same design resorces where allocated in 2015 - next obvious step would be to look into the remaining tubes.
A sub 1000g raceday TI frameset anno 2015 for a 60-80kg rider shouldnt be a problem - however most people buying a 3-5000$ custom TI frameset wants the frame to last for 10-15 years so they tend to want 'extras' for everyday usage and options for a heavyer build that will be indestructable.