Our titanium frames are constructed from seamless aerospace grade tubing, selected specifically for each and every frame. Main frame tubes are double butted, a process of drawing which can make the ends of the tubes thicker, usually .89mm and thinner in the centre where there are less stresses. I'll be posting a video showing the butting process soon. Typically the wall thickness of lets say a double butted top tube can be as thin as .6mm, these are figures from a Reilly frame. Lots of cheaper far Eastern produced frames don't have double butted tubes at all, just to save money.
So, down to the grades of titanium
3AL2.5V known as grade 9 in the engineering World.
The most widely used titanium grade for making bicycle frames as its relatively easy to work and draw into tubes and has excellent mechanical qualities.
The 3AL2.5V description just means that grade 9 is an alloy of 3% aluminium and 2.5% vanadium, a few other trace metals and the rest titanium itself. At Reilly Cycleworks we only use 3AL.2.V titanium for frame tubes and this yields brilliant ride qualities.
Our 3AL.2.5V tubes have an ultimate tensile strength of 960MPa, MPa is unit of measurements and means Megapascals, a very important figure for designers. 3AL.2.5V titanium has a density of 4.48gr/cc, very light indeed. Our final tubes have a elongation figure of typically 12-15%, again very important and all tubes are Cold Worked and Stress Relieved, CWSR.
CNC 6AL4V machined headset spacers
6AL4V known as grade 5 in the engineering World
Seamless 6AL4V titanium tubes are extremely rare and something I developed as a designer with a famous British tube mill back in the 1990's, production was stopped due to the mill's full order book with Boeing taking priority. 6AL4V is outrageously hard to draw into tube form, given it's colossal strength.
The 6AL4V description just means that grade 5 is an alloy of 6% aluminium and 4% vanadium, a few other trace metals and the rest titanium itself. At Reilly Cycleworks we use 6AL4V titanium not only for frame tubes but also for head tubes, BB sleeves, braze ons and head tubes etc as not only is it incredibly strong but is easier to machine. Yes, easier to machine but hard to draw into tubes, a very complex material.
Our 6AL4V parts/tubes have an immense ultimate tensile strength of 1150MPa, MPa is unit of measurements and means Megapascals, a very important figure for designers. 6AL2.5V titanium has a density of 4.42gr/cc, a little lighter than 3AL2.5V. Our tubes have a elongation figure of typically 15%, again very important and all tubes are Cold Worked and Stress Relieved, CWSR. Our 6AL4V tubes are in addition made from ELI (Extra Low Interstitial gas purity) grade titanium allowing us to butt and shape seamless tubes to much tighter tolerances needed for frames such as our T640.