Posted April 27, 2001 - 11:38 PM
Posted April 28, 2001 - 01:42 AM
Posted April 28, 2001 - 06:32 AM
Originally posted by scouringpad:
The expense of the material is only the start with titanium. Welds need to be protected with inert gas on the backside as well as the front. And they need to be protected until they cool sufficiently, which means a trailing gas boot, and a backup gas bar, or a purge tank. For something like a bike frame, fittings would be required to purge the tubing with argon, and the welding would probably be done in a purge tank to expedite the process. Slow, labor intensive, and costly. And titanium is lighter than steel, but not as light as aluminum. Now magnesium, on the other hand......
When talking of titanium and its expense, I was referring to the job cost, not just the material cost. Titanium absorbs nitrogen in the air at its crytical temperature and therefore, for maximum protection of the material during the welding process it is important that all welding be done within a purge tank, which is a difficult and expensive process for a structure like a motorcycle frame.
You mention magnesium as a potential material for the WR. I would rule out magnesium on material cost, manufacturing difficulty and also it would be prone to fracturing on a structure such as a frame.
Posted April 28, 2001 - 07:05 AM
Originally posted by mike68:
What about using a lighter steel alloy like a chromoly? You can use a thinner wall and get the same strength and workability as regular steel. They may be using a chromoly frame already, I don't know.
I recon this would be a more favourable option. Chromoly as you yanks call it (4130 spec used in aircraft and race car applications), although being no lighter in weight than regular mild steel, has a higher tensile strength, and is generally used in thinner guages to reduce weight. The problem with this is that in order to retain its full strength after fabrication, the whole structure would need heat treatment, and the whole cost of the manufacturing process would be high.
If it is used in heavier guages similar to that of the mild steel used on our frames, I beleive that it would be beneficial when used in perimeter type frames such as is used on the TMs. When usd in slightly heavier guages the heat from welding is dissipated over a greater area of the tubing, and doesn't cause brittleness around the welds, in the way it does with thinner guages in aircraft and race car applications, and so heat treatment could be avoided. Also it can simply be joined with other steels which would further reduce costs.
I recon Yamaha are more likely to choose an alterative material for their WR frames if, like the titanium valve thing, it has a recognised trick value, so some of the reasons we've covered may have little influence. Innovation sells, even if it is not fully substantiated.
[This message has been edited by Derek Burns (edited 04-28-2001).]
Posted April 28, 2001 - 11:45 AM
If I remember right from a materials class I took, the strength to weight ratio for your average alum. is less than most steels (not sure if that was mild steel or 4130 and what type of alum. ... By the way talking about alum. vs. steel is very broad the strengths of each very drastically, (like over 2 fold in some cases) depending on the application vs. cost) The difference is in the structure of alum. frames. You can use more material because it's lighter.
I don't think most alum. frames would hold up in a crash as well as steel because of the design structure. An alum. frame design would use more structure in its most used loads (like up and down) vs. the all around bruit strength of a steel structure steel. Notice the shape of alum. Vs. the steel tube design.
Think about alum. sub frames... they bend easy
:)Plus, the Japanese think alum. sucks! (Because of it's properties (strength to weight ratio) and manufacturing)
:)Plus, your really not saving much weight for the buck.
:)Plus, mild steel is easy for us fabricators to play around with if we want to add on gizmos.
my pretty pennies, joe callan
3years Mechanical Engineer switched to Food Science on my 7th year now!
Schools Cool --> Stay in School
Posted April 28, 2001 - 02:44 PM
Posted April 29, 2001 - 12:00 AM
Also, I wasn't suggesting magnesium would make a good frame, just that it is lighter than aluminum. But many alloys are continually being developed, and it is always a possibility that an adequately strong alloy using magnesium may be developed for some other industry, and then carried into the bike frames if workable. Titanium is a relatively weak material in pure form - it is only through alloying with other materials that some structurally strong materials have been developed.
I believe chrome moly steel IS being used in some bike frames, but I don't know enough about it to know what manufacturers or which bikes. Bicycle manufacturers such as Trek and Cannondale use 4130 for mountain bike frames, and of course it has been used for years in airplanes and racing car frames.
How about a platinum dirt bike frame? At over 1300 pounds per cubic foot, it should be just the thing for those with excess money falling out their pockets, and a need to keep their bike firmly planted on the ground......plus, just think of the polish job!
Posted April 29, 2001 - 12:40 PM
I dont know of any unalloyed metals used in structural situations.
I'm sure somebody would go for the platinum framed WR.
Posted April 30, 2001 - 06:29 AM
Posted April 30, 2001 - 01:26 PM
You make your choice when you select your preferred bike.
Posted May 01, 2001 - 06:51 AM
Posted May 02, 2001 - 04:08 AM
Posted May 03, 2001 - 02:11 AM