In praise of titanium - and Spa Cycles

[Mugshot]

I find A flat to be particularly fatiguing.

Underappreciated post

 

[jazzkat]

I find A flat to be particularly fatiguing.

Underappreciated post

Agreed, it works on a couple of levels!

 

[Yellow Saddle]

@Yellow Saddle - Without derailing the thread too much, if what you're saying is true and comprehensive (which I have no grounds to disagree with) Then what is it that makes some bikes feel so inherently different from others? Am I to believe that given all materials have zero flex vertically and will make no difference to ride "dampening" (or give it a name, as appropriate") that 2 bikes with similar gemoetries and the same wheels/contacts points but different materials will feel the same?

You raise a good point and some of the answer lies in @Fab Foodie's post above. Very few people have identical bikes in different materials. Think about that for a minute. Only then can we actually compare the rides.
I am in a kinda unique position here but a position that is by no means conclusive.
I bought myself a Cannondale CAAD4 bike way back when and thought it was a great bike. I then took up touring and decided that the Cannondale wont work - it having no bosses for racks and the chainstays being too short for panniers. I then made myself a steel bike with the exact same dimensions as the Cannondale. Because knew nothing about framebuilding and design at the time, I didn't want to experiment with angles etc and I copied the CAAD4 exactly - except for one thing - I made the rear chainstays as long as the tubeset I ordered allows. Obviously this was now a steel bike. The only difference in the frame was the rear end which had a super long chainsta - so long I could fit my fist between the rear wheel and the seat tube.
Opinion in the "squad" at the time had it that the new bike would be super flexy, soft to ride and slow to steer but more stabe - all standard bike magazine mantra.
The reality was that I could not tell you which bike I was riding. Ridiculous maybe but I had plenty moments where I was looking straight ahead, immersed in my thoughts and then coming back to the present, I couldn't tell which bike I was on until I looked down.
There were some differences. The alu bike had 28-spoke wheels, the steel one 32. The alu one had a Ti seatpost, the steel one, an alu one. The bars were a different brand but gruppo was identical. I could not perceive any difference in steering, vibration, flex etc.
Obviously this is not conclusive but it did get me thinking about how much pre-conception affects our perception of the ride experience. I think vibration is over rated. When on the drops, a bike is very well damped and only rough bumps come through. I just don't get this road buzz that's so often mentioned.

 

[Yellow Saddle]

not saying it'll change the answer (not my field) but shouldn't the tubes be same strength rather than same mass?

My assumption is that all the tubes have no vertical compliance to speak of and therefore only the mass has an effect on how it vibrates. But if you want, change the experiment so that they all have the same compressive strength but whatever the required mass for that strength is.

 

[Globalti]

Here's a little story: I had a titanium Global mountain bike and the RH chainstay had been badly gouged by chainsuck. I wanted to sell it but felt it would sell better if I got it repaired and explained clearly in the ad. So I began phoning around local engineering firms and eventually found one who said he could do titanium. Took the frame along one lunch time and walked into a filthy engineering shop with some quite interesting bits of work lying around, to be told: "Ah - you want Mr 'arris, over there!" I wandered over to where a bunch of guys were sitting on old chairs reading their papers and up stood a youngish man with quite a lot of hippy jewellery and a really spaced-out look in his eyes. I showed him the damage and he just called out: "Fred! Have we got any of those ti welding rods?" This was confirmed and Mr 'arris told me: "Twenty quid. Come back tomorrow". I left with my heart in my mouth, thinking either Mr 'arris is a genius and he's going to amaze me with his craftsmanship or he's a plonker and he will ruin the frame, in which case it's toast and I might be able to sell it for a few quid. Oh well.

There followed a worrying 23 hours and the next lunchtime I drove back. Mr 'arris presented me the frame with a near-perfect repair, you could just make out a different colour of metal where he had melted it into the gouges and ground it flat. His only comment was to the effect that the titanium had worn out quite a few sanding belts. I gave him the cash, went home happy and advertised the frame complete with clear photos and got good money for it.

 

[Venod]

Coppaslip

Copperslip is good stuff & less messy than the Rocol ASP we used at work.

 

[Yellow Saddle]

umm, what does half as strong but half the weight mean in practice - same strength for a given weight? So why aren't aircraft made of steel rather than ti? I realise "strenght" is a somewhat vague term in engineering, but I think the point is fine for our purposes

The difficult to work, and only available in certain sizes points are perfectly valid

Yes, approximately that's what it means.
The assumption that aircraft contains no (or little) steel is incorrect. There is plenty of steel in an aircraft and without steel, it will not fly. Same for aluminium. Wing spars for instance, are made of aluminium and wings are covered in alu, not ti. My brother has an airplane with wooden spars and fabric wing covering. It is strong enough and making his Piper Cub from ti will achieve nothing. Horses for courses.
Engineers use the material most appropriate to the application. All materials have limitations of sorts and some are simply manufacturing limitations. Cost, fatigue limit, corrosion etc all play a part in choosing a material for the application.
In your mind, why not design a ball-point pen for yourself. Use a standard Parker ink cartridge at the centre and design the form around that. You'll quickly see that the wealth of materials at your disposal - wood, plastic, gold, stainless steel, carbon , ti, alu etc all have merit but don't all make sense.

 

[Yellow Saddle]

With different densities, how can they have both equal dimension and equal mass?

Equal OD it should read. But don't get hung up on the dimensions. I just want to raise the thought whether or not we really think that little pieces of pipe can display radical different vibration throughput.

I'll now let the cat out the bag and put a 5th tube in there. This one is made of silicone.

 

[winjim]

Underappreciated post

I'm here all week.

 

[Profpointy]

Yes, that's what I

Equal OD it should read. But don't get hung up on the dimensions. I just want to raise the thought whether or not we really think that little pieces of pipe can display radical different vibration throughput.

I'll now let the cat out the bag and put a 5th tube in there. This one is made of silicone.

Haven't done the experiment as stated, but for musical instruments "vibration characteristics" is material dependant.

Also on your original experiment you will feel more vibration through a steel bar than a wooden bar or foam rubber bar to be extreme

 

[Yellow Saddle]

Here's a little story: I had a titanium Global mountain bike and the RH chainstay had been badly gouged by chainsuck. I wanted to sell it but felt it would sell better if I got it repaired and explained clearly in the ad. So I began phoning around local engineering firms and eventually found one who said he could do titanium. Took the frame along one lunch time and walked into a filthy engineering shop with some quite interesting bits of work lying around, to be told: "Ah - you want Mr 'arris, over there!" I wandered over to where a bunch of guys were sitting on old chairs reading their papers and up stood a youngish man with quite a lot of hippy jewellery and a really spaced-out look in his eyes. I showed him the damage and he just called out: cut cut cut cut...

Keep Mr 'arris' details in a safe place.
You were lucky to find him. Welders don't like to do jobs like that because they are so difficult.
Unfortunately he probably would not have been able to successfully repair a crack in the same area as that would have required heat treatment afterwards to anneal the weld.
The different colour of the new material is merely because the alloy was different to what the frame was made of.

 

[Yellow Saddle]

Haven't done the experiment as stated, but for musical instruments "vibration characteristics" is material dependant.

Also on your original experiment you will feel more vibration through a steel bar than a wooden bar or foam rubber bar to be extreme

I just added a silicone bar to the experiment. I wanted to leave that for last to make a dramatic (tadaaaaa) entrance.

I agree that in your case - guitar boxes, tuning forks, cymbals and violin strings, the material makes a difference. But the structure of what we're talking about is different. On a tuning fork you have a free end that's vibrating and by changing the materials the node will be at a different place, producing a different note.
I'm basically demonstrating that chisels of different but similar materials will all transmit shock and none will damp the shock that's transmitted along the plane of the tube.
Your case is relevant at handlebar ends that are not help encased by your hand. As soon as you touch that handlebar you've dampened it and the vibration is gone, as if you've touched your singing tuning fork.

 

[Venod]

Unfortunately he probably would not have been able to successfully repair a crack in the same area as that would have required heat treatment afterwards to anneal the weld

Or maybe he had access to the correct preheat & post heat treatment required for a successful weld, you also need a gas purge at the back of the weld to keep a clean environment, a dirty weld usually fails post weld examination.

 

[Fab Foodie]

I'm here all week.

Oh no!

 

[Fab Foodie]

Another small point .... a double diamond frame is not truly 2 triangles, it's one Triangle and one Rhomboid, so it's not unrealistic to suggest that a frame has vertical compliance and this will be dimension and material dependent.