Reynolds 953 / Rohloff gear shift

[PtP]

Hi All
Just been reading about Reynolds 953 as a frame material.  Sounds quite interesting.  Anyone know if Thorn are looking at it to use in the near future?  Also, I've heard that Rohloff have been discussing making gear shifts for drop bars, any 'goss' anyone?  Reason for my query is that I'm seriously thinking about buying a RST and, as I usually have a lousy sense of timing, have decided to ask questions first prior to buying.
Thanks in advance
Paul

[stutho]

Hi PtP,

Rohloff drop shifter:
This rumour has come up on the web a couple of time in the last two years.  I will believe it when I see it!  Until it does arrive, you could be waiting a very long time, I would suggest mounting the shifter to an accessory bar – it works well for me.

Reynolds 953:
I would love to have a bike made out of that stuff! I have not heard any discussion of Thorn using it.  If they do I would of thought it is likely that it will only be used on the British built bikes because it is difficult to work (i.e. EXP's and Mercury)

[freddered]

If Rohloff ever make a shifter for drop bars then it's likely to be  a modified twist-grip, fitted close to the stem on the bar tops (some company makes one already) and not an STI type shifter (incorporated into Brake lever).

This wouldn't appeal to me as my barbag clamp goes there and I like to have my hands as close to the stem as possible when climbing hills.

The accessory bar is just as convenient as this type of fitting BUT obviously you need enough Steerer tube showing.  Without space for an accessory bar it makes a lot more sense.

[PH]

Reynolds 953 - It seems to be attracting the same hype as titanium did 6 or 7 years ago. I note, like early Ti, it's rolled rather than drawn tube, I hope it doesn’t split along the seam like much early Ti did!  I expect it'll probably loose the premium price in the same way as Ti and Carbon have.  For those reasons I'd wait 5 years.

Rohloff drop bar shifter - I doubt it, the Germans along with most of the world think drop bars are only for racing bikes.  As freddered says if it was a modified twist grip there wouldn't be much advantage.  It'd need to be a complete rethink and I can't see them bothering unless they also develop a road bike hub (another common rumour)  

[bike_the_planet]

quote:Originally posted by PH

Reynolds 953 - It seems to be attracting the same hype as titanium did 6 or 7 years ago. I note, like early Ti, it's rolled rather than drawn tube, I hope it doesn’t split along the seam like much early Ti did!  I expect it'll probably loose the premium price in the same way as Ti and Carbon have.  For those reasons I'd wait 5 years.

For touring bikes, I don't see the advantages of 953 over, say 853, or even 4130 CroMoly. Thos materials result in frames that are plenty strong enough. The only advantage of the extra strength is to make the tube walls thinner so that the frame's lighter. But then thin tubes risk a) denting problems - particularly on a touring bike with baggage handlers, and b) starting to get near the material's buckling limit.

I am a steel fan - I own two Thorn bikes - but cheerfully admit that steel as a material has approached its limits. To create lighter tubes, you will have to look to other materials - ti or carbon. At present, neither of those materials suite inexpensive but reliable frame building.

Cheers

[stutho]

quote:For touring bikes, I don't see the advantages of 953 over, say 853

The advantage for touring bikes can be summed up in one word - stainless.  Lets face it expedition bikes in particular have to put up with some pretty rough treatment.  Now Thorn frames get treated to an very good anti corrosion treatment, however I for one would have happily paid and extra £100 if the tubes were made of a material that didn't rust at all.  (Unfortunately the likely increase in price will be a lot more that £100)

The other advantage will be greater strength from tubes of the same size.

[bike_the_planet]

quote:Originally posted by stutho

quote:For touring bikes, I don't see the advantages of 953 over, say 853

The advantage for touring bikes can be summed up in one word - stainless.  Lets face it expedition bikes in particular have to put up with some pretty rough treatment.  Now Thorn frames get treated to an very good anti corrosion treatment, however I for one would have happily paid and extra £100 if the tubes were made of a material that didn't rust at all.  (Unfortunately the likely increase in price will be a lot more that £100)

The other advantage will be greater strength from tubes of the same size.

I can understand the advantage in terms of corrosion resitance. But strength? 953 has a greater tensile strength than 853 and 4130. Where does that get you on a bike? Have you had tube failures due to tensile strength inadequacies on your Thorn tourers already? I'd be very surprised if you have.

At a gauge that's practical, eg 0.9/0.6/0.9, heat-treated 4130 is way strong enough. Stiffness and strength of the actual frame depend more on the frame design than the material itself. Increasing the tensile strength of tubes still further is of no real value unless you are planning to slim down the tubes and reduce weight. And then you are approaching buckle and denting limits.

Cheers

[stutho]

Having an even greater margin can only be a good thing can't it?

There may be two much greater problems using 953:
Firstly, it may produce tubes (and frames) that are too stiff with little compliance (in normal gauges); Secondly, bikes normally fail at the welds - 953 is supposedly difficult to weld therefore, perversely, it may lead to more frame failures.

I think, like with most things, time will tell - I wouldn't spend decent money on 953 until it is proven. I would still like to volunteer myself, however, as the first test pilot of a Thorn Rohloff EXP 953 ;-)

[bike_the_planet]

quote:Originally posted by stutho

Having an even greater margin can only be a good thing can't it?

There may be two much greater problems using 953:
Firstly, it may produce tubes (and frames) that are too stiff with little compliance (in normal gauges); Secondly, bikes normally fail at the welds - 953 is supposedly difficult to weld therefore, perversely, it may lead to more frame failures.

Stuart - The stiffness of a cycle frame is more dependent on the frame design than the material. A classic example is aluminium versus steel frames. Most people would agree that aluminium frames feel stiffer than steel ones.

It would surprise most people, then, to learn that aluminium, as a material, is less stiff than steel - it has a lower modulus of elasticity. So why do ally frames feel more stiff? Because stiffness of a tube depends on the tube diameter and thickness.
Ally frames have tube diameters twice that of steel frames.

In fact, the stiffness of a tube is proportional to the diameter to the power three.

Changing the frame material from, say 725 to 953 will have imperceptible changes on the stiffness of a frame. If you want a stiffer/less stiff frame, increase/decrease tube diameter.

Materials such as 953 have a higher UTS (ultimate3 tensile strength) and hardness than, say, 853. You may think that increased hardness willl  make the fram more robust, but, once again, when you have a tube of thicknesses less than 1 mm, the dent resistance of the tube is more dependednt on the thickness of the tube wall rather than the actual material used.

A glance through a textbook on materials science will clarify.

Hope this explains,

cheers

[stutho]

quote:A glance through a textbook on materials science will clarify.

Cheeky! ;-)

Aluminium frames are stiffer not because of Al’s material property of stiffness but because of other design constraints imposed by Al.  I know this the same as you.  (Designing for the fatigue life of AL is the main factor.)

The same argument may hold for 953.  953 is not a drawn tube but is rolled and welded.  Any weld is a weakness especially in terms of fatigue life.  Reynolds are claiming great thing in terms of the fatigue life of 953 but I have to wonder if these are the properties of the material or the tube.  If it is the latter then all is good, but marking people being what they are…(Call me a cynic!)

If I am right, and I admit it is a hunch, then the overriding factor in designing a 953 frame may become fatigue life of the welded seams. It is this design constraint that will produce stiffer frames.

Incidentally if anyone is interested in learning more about metallurgy in cycling (and has managed to read though the last couple of posts to here!) there is a very good series of articles at63xc  

[bike_the_planet]

quote:Originally posted by stutho

quote:A glance through a textbook on materials science will clarify.

Cheeky! ;-)  

Stuart,

Apologies if my post appeared condascending. It was (genuinely) meant to be helpful.

But as you appear to know quite a bit about this already, then it probably wasn't much help!

As 953 is a stainless alloy, then the welds should still be relaible if done with the appropriate care and technique. As the fatigue characteristics aren't that different from 4130, the butted sections shouldn't need to be any beefier than normal.

Cheers,