Ti Monster Frame*Completed Pics*Headed for DucStock

[Howie]

You mean internet bullshit?  

One that crashed into a bridge ripped the tubes from the steering head.

The welds didn't fail. The material was stressed beyond it's capabilities.

I posted at the time the frame and it's welds were not designed to be crashed into a bridge abutment...I stand by that statement.

What?  A motorcycle frame that is not capable of withstanding a crash into a bridge abutment?  Unbelievable! 

[ducpainter]

What?  A motorcycle frame that is not capable of withstanding a crash into a bridge abutment?  Unbelievable! 

Tell me about it. 

[brutALEx]

really?

15K for a couple of seasons?

must be more of that internet bullshit?

Not exactly first hand experience, but I have seen examples at local Ducati dealer who is also building custom bikes. I personally know the owners.

[Randy@StradaFab]

 There are 29 different grades of Ti. I used Grade 9, which is what NCR and Doug used and most bicycle frames are made of. This is used primarily for aircraft hydraulic lines. I don't think that would be an application for low fatigue strength.
  Here's some info on Ti.
 You are somewhat limited in what tubing you can buy. You can get thinwall Gr9 pretty easy, but if you want something thicker it's more difficult. That's why I had the headpiece machined out of a piece of Gr5 pipe. That piece of 7" pipe was $180 and another $80 to machine it. From the pictures I saw it looked like Doug used a piece of thinwall tubing with an aluminum insert for the bearing races. That's probably why his frames were mitered going to the head tubes, the tubing was too thin to bend. Not knocking his frames, that's just how he built them.
  Grade 9 has 3% Aluminum and 2.5% Vanadium. Grade 5 has 6% Aluminum and 4% Vanadium. So if you build your frame from Gr9, guess what, you can't buy Gr9 plate for the gussetts. So you have to weld Gr9 to Gr5. Which isn't a big problem, you just have to choose which filler to use. You would think since they use all of this tubing for hydraulic lines that you could get Gr9 filler pretty easy. Nope.....I found one supplier for Gr9 filler, and it was over $600lb. So I talked with a couple of the bicycle manufacturers and they use Gr5 ELI rod which is slightly over $100lb. Also you need to use Ultra High Purity Argon for a shielding gas. I went through 2 1/2 bottles at @ $180 a bottle.
  I wanted to build a Ti exhaust for this bike but I really didn't have time and finding someone to bend thinwall tube didn't work out.
I got a quote to bend 1- 180 degree elbow from 2" Gr2 Ti tubing with a .049 wall. $1,400!! For 1 elbow. The wife wasn't going for that.LOL
 I hope you guys found this informative and I hope it somewhat explains the high cost of Ti parts. I didn't mention that you also have to consider that Ti takes longer to cut and machine and you use more cutting ,machining materials. I don't think you will ever see "cheap" Ti frames.

  As far as NCR frames welds cracking, I guess it's possible. Can someone name a manufacturer that hasn't had cracked welds at some point?









 

[Syscrush]

That claim about the fatigue strength of Ti sounds like pure BS to me.  This is true of Al, but not steel, carbon, or Ti.

This is why you can buy springs made of steel, carbon, and Ti, but not Al.

In any case, it's also why motorcycles have suspensions on 'em.

[Punx Clever]

That claim about the fatigue strength of Ti sounds like pure BS to me.  This is true of Al, but not steel, carbon, or Ti.

This is why you can buy springs made of steel, carbon, and Ti, but not Al.

In any case, it's also why motorcycles have suspensions on 'em.

One of the big things an engineer learns in machine design is fatigue.  The honest to goodness truth of the matter is that steel is the ONLY material that can be designed for an infinite life span.  The material properties of every metal degrade over time, but steel is the only one that approaches something other than zero.  Aluminum, Ti, whatever, will all become weaker over time due to stress cycles, and will eventually fail.  Period.

As for the suspension... your front forks do nothing to alleviate torque about the steering head from cornering or just the fact that motorcycles have a rake.

[brutALEx]

That claim about the fatigue strength of Ti sounds like pure BS to me.  This is true of Al, but not steel, carbon, or Ti.

This is why you can buy springs made of steel, carbon, and Ti, but not Al.

In any case, it's also why motorcycles have suspensions on 'em.

At the moment I'm choosing the frame for my S4Rt project - the guys who build and guys who ride titanium framed bikes told me these details. So my choice is carbon, Al - second place, Ti - not an option.

IMHO Ti frames are purely commercial - just to have something exotic and rare in the catalog and make some $$$. Customers who buy them are aware of this.

[Syscrush]

There are alloys of Ti that exhibit a theoretical fatigue limit below which continued loading does not lead to structural failure.  I'm not an expert on this, but the choice of Ti for a valve spring material reinforces the notion that a properly-engineered solution can manage 10^6+ cycles before failure.

In the bicycle world, Ti frames are not considered to have a limited service life, but in the motorcycle world where the forces are a lot higher it might be a different story.  It seems to me that if the frame is designed for sufficient stiffness it should be able to stay well below the fatigue limit for an extremely long time - not just a couple of seasons.

Al is more susceptible to fatigue than Ti, and I don't see people worrying about fatigue in Al frames, wheels, or swingarms.

[Randy@StradaFab]

  I agree Syscrush...that's why my frame is a little heavier than other Ti frames you might have seen. Ti is not a magic metal. Like I said before, I don't think you can substitute Ti for Steel and end up with the same result. Mines a little beefiier. I wouldn't build a 9lb frame.
  I am curious about the NCR SBK frame. It appears to be the same O.D. as the stock frame. I wonder if the wall is thicker.
Also, how many people ride hard enough to feel a frame flex. Don't want to step on any toes but how many people on this board can ride a bike to it's limits? I know I can't....OK, maybe right before I crash

  Good discussion....

[Speeddog]

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[Punx Clever]

In the bicycle world, Ti frames are not considered to have a limited service life, but in the motorcycle world where the forces are a lot higher it might be a different story.  It seems to me that if the frame is designed for sufficient stiffness it should be able to stay well below the fatigue limit for an extremely long time - not just a couple of seasons.

Al is more susceptible to fatigue than Ti, and I don't see people worrying about fatigue in Al frames, wheels, or swingarms.

There is a trade off that you have to make.  Sure, a steel frame will be heavier, but I can guarantee an infinite (90% certainty) life if it's built right.  The Ti frame could be designed to last a long time and be light, but I would never say infinite life time with 90% certainty.  Personally, I would prefer a lightened chromoly steel frame to a Ti frame.  Costs would be lower, lifetime would be longer, and the chromoly frame wouldn't be too much heavier.

As for the aluminum frames... looking at my swingarm, the aluminum is quite thick.  To make a similar trellis style frame out of aluminum that would last, the tube walls would have to be pretty thick too.  The question is, would it be cost or weight effective to build an aluminum tube copy of the trellis frame we all know and love?

It sounds like RMartin is taking the more balanced, longer life approach, to a Ti frame.

[stopintime]

What about this cromolly? (spelling??)

[Raux]

What about this cromolly? (spelling??) = steel

[stopintime]

What about this cromolly? (spelling??) = steel

That's not exotic 

Reason I ask is I was offered a custom frame while entertaining the idea of an oversized Monster (matching me)

[Punx Clever]

chromoly steel has a much higher strength to weight ratio than plain steel, while still being able to machine, weld, and bend easily.

http://en.wikipedia.org/wiki/41xx_steel