Tickle T-5 .

Fast Eddie

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My understanding is that 531 work hardens, hence T45 being the choice of most these days.

A T45 frame is both stiffer and stronger than stock.
 
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johnm said:
eby_at said:
got the complete file last week from a swiss guy.
I just began to transform into CAD and i will put on file to th eboard

That would be excellent !!!!

Thankyou
Ik do my very best, but i cannot promise a fix date
 
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Rohan said:
Elementary my dear Watson.
The tensile strength/yield points of mild steel is quite low, so it is relatively easy to bend to a new shape.
Hi tensile steels like 531 and chrome-moly are made of stronger stuff, so they need (a lot) more muscle to force into a new shape.
Reshaping steel goes beyond the point where springiness comes into it...
It is not about the muscle required to bend the higher strength steel. A decent tube bender can usually cope with ease. If you have a tube bender and usually bend mild steel, you don't get the same radius bend with the same former when you use chrome moly tube. The spring-back is different when you release the clamps on the bender. It means that making a frame from chrome moly takes more work if you want to get the right shaped bends. Also the temperature of the tube when bending is important if you don't want nasty things to happen.

'Reshaping steel goes beyond the point where springiness comes into it' - Love this - have you ever made a frame or are you working on supposition again Sherlock ?
 
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Go away and read up on The Youngs Modulus of steels (elasticity).
Then report back with your findings.
 
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Young's modulus has nothing to do with this. If you bend chrome moly tube you obviously go beyond it's limit of elasticity however it still retains it's strength. It doesn't simply accept a bend and sit there with no spring. When you release the clamps on the tube bender, it must spring back. Even mild steel does that. I suggest you are looking at this with an engineer's mindset, the difference is the reason many engineers talk to trades people before committing themselves. The practice is different to the theory. In one factory in which I worked we had a sheet metal shop which used steel dies to form steel. Spring-back was always something which had to be coped with. Different materials give different results.
Do you believe titanium tube would accept a bend ? I think you could put it in a mandrel bender and pull it around a former and when you released the clamps it would come out straight.
 
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acotrel said:
Do you believe titanium tube would accept a bend ? I think you could put it in a mandrel bender and pull it around a former and when you released the clamps it would come out straight.
Sounds like magic material ?
You could build an airplane out of it, and if it crashed it would spring back to brand new.. !?
If only the crew could be so lucky....

BSA built scrambler frames (what we'd call MX) out of Ti back in the 1950s - when it was truly exotica/unobtanium.
Apart from being light, and prone to cracking back then - and impossible to repair trackside - it wasn't quite so magical it seems.
In bicycles it feels 'dead' to the rider, although modern alloys and frame design has changed that ?

But we diverge...
 
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I could believe in a titanium space frame Norton made out of straight tubes. My Mk3 Seeley is made out of chrome moly. All except one bend are minimal tightness. Most of the later frames from the 60s had fairly straight tubes - nothing like a feather bed. I wonder how many chrome moly replicas of those have been made ?
 
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What would a titanium frame gain, that a good steel one doesn't ?
Apart from slightly lighter, and enormous $$$
Ti is only about half the stiffness of steel in the specs sheets...
 
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you would not do it. I was talking about spring-back, that is the fifficulty with chrome moly, you don't always get the radius bend you expect.
 
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BSA built the Ti framed Moto-X bike after Jeff Smith won two World Champs in the mid 60s. It was a bit lighter, and a lot more flexible, and the constant cracking induced by the extra flexing, required welding in a special inert atmosphere, thus requiring a special portable chamber were two of the features which made it an expensive and very dead end.

I'm pretty sure that I read an article either by Ken Sprayson, or an interview with him where he stated that there wasn't much difference between Reynolds 531 tubing, and T45, apart from sometimes varying availability and minor differences in cost. In the same article he said that "ordinary" cold drawn (i.e. high quality) carbon steel and 531/T45 tubing differed in that the 531/T45 tubing lost less of its properties after welding, all materials loose some of their properties, but some loose more than others. This was in the days when frames were gas bronze welded. 531 tubing has a yield stress of about 550 MPa, T45 has a yield of about 480 MPa, cold drawn 1018 steel tube has a yield of about 310 MPa. If you take the yield stress as a determining feature, then if 531 is 100%, T45 approx 87%, 1018 approx 56%. Reynolds 531 has been pretty much unavailable for several decades, except to "special order" and we all know what that means $$$$$$$$$$! Apparently, these days AISI 4130 is considered to be comparable to R531. This goes some way to explain why Manx featherbeds are lighter than road going featherbeds, the Manx frame is thin wall 531, the roadgoing frame is thicker walled cold drawn steel tube
Springback, all materials suffer in some degree to "springback" when bent. It's how that springback is catered for by the person doing the bending that makes the difference. Its one of the reasons that some frames are constructed from straight or largely straight tubes. Bending a tube accurately in one plane is pretty specialised, bending the same tube accurately in 3 planes is close to artistry.
cheers
wakeup
 
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Good comments.

Its pretty normal to have to bend things beyond where they need to be to get them to the right bend.
You have to exceed their yield strength ...
 

lcrken

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acotrel said:
Do you believe titanium tube would accept a bend ? I think you could put it in a mandrel bender and pull it around a former and when you released the clamps it would come out straight.
Titanium bends quite nicely with a normal tube bender for thicker walled tubing or a mandrel bender for thinner wall. You do have to account for springback, but you have to do that with almost any material, including all the steel alloys discussed here. Look at all the titanium exhaust pipes available nowdays. Tthey are mostly mandrel bent, although its actually quite practical to bend titanium exhaust pipe by packing with sand and heating it to bend around a form.

Re your comment in a later post about a space frame using straight sections of Ti tube, I've seen one for a Ducati, and it is pretty impressive, but not so cheap. Making titanium frames is another case of something cool you could do, but the cost/benefit ratio is pretty high.

Ken
 
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lcrken said:
Titanium bends quite nicely with a normal tube bender for thicker walled tubing or a mandrel bender for thinner wall. You do have to account for springback, but you have to do that with almost any material, including all the steel alloys discussed here. Look at all the titanium exhaust pipes available nowdays. Tthey are mostly mandrel bent, although its actually quite practical to bend titanium exhaust pipe by packing with sand and heating it to bend around a form.

Re your comment in a later post about a space frame using straight sections of Ti tube, I've seen one for a Ducati, and it is pretty impressive, but not so cheap. Making titanium frames is another case of something cool you could do, but the cost/benefit ratio is pretty high.

Ken
A friend of mine told me that in the former USSR where 99% of cars were Trabants, in a particular town that had a military aircraft factory on it's outskirts, most of the Trabants had titanium exhausts. He reckoned that the exhaust would outlive the rest of the car by about 50 years.
cheers
wakeup
 
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