Titanium GT40 Chassis
- Thread starter James
- Start date
Round tubing would be better as its torsionally much stronger....then use honeycomb bulkheads and floorpan and you will really have a stiff and strong chassis...just a thought.. /ubbthreads/images/graemlins/smile.gif
Obviuosly depends on your chassis design and whether you want to replicate a current design or design a new one for more interior space and a better more effective suspension design...
The specific modulus (stiffness/unit weight) for titanium is roughly the same as steel or aluminum. Every pound you lose because of any strength advantage will be reflected in a more flexible chassis.
Agree with Bob. Unless the chassis design is changed with the stiffness to weight the same as steel, the chassis would be the same weight for the same stiffness chassis. If you accepted a less stiff chassis then you could certainly save weight and have the same strength.
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For the same strength/stifness Titanium is 45% lighter. Basic maths mate.
A chassis made from the same wall thickness as steel should be 45% lighter but just as strong.
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JP, read Bob Putnam's post again. Titanium is superior to steel and aluminum in strength/weight. That means a control arm made from one pound of titanium will be stronger than a similar arm made from one pound of steel. But the stiffness/weight ratio for titanium is comparable to that of steel and aluminum. A chassis member contributes to overall torsional ridgidity due to its stiffness, not necessarily its strength. Titanium is great for applications like suspension members and highly stressed fasteners where great strength is required, or for exhaust systems where high-temperature structural integrity is maintained, but it won't necessarily make a better space fram chassis than steel.
If you want a strong, torsionally ridgid space frame chassis that weighs less, it could be done using an existing chassis design with thinner-section 4130 tubing instead of mild steel. Even then, the weight savings would be on the order of a few percent, rather than tens of percent. The best way to reduce chassis weight would be to completely re-engineer the space frame design (using FE analysis) to use less material in a better way.
For the same strength/stifness Titanium is 45% lighter. Basic maths mate.
A chassis made from the same wall thickness as steel should be 45% lighter but just as strong.
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JP, read Bob Putnam's post again. Titanium is superior to steel and aluminum in strength/weight. That means a control arm made from one pound of titanium will be stronger than a similar arm made from one pound of steel. But the stiffness/weight ratio for titanium is comparable to that of steel and aluminum. A chassis member contributes to overall torsional ridgidity due to its stiffness, not necessarily its strength. Titanium is great for applications like suspension members and highly stressed fasteners where great strength is required, or for exhaust systems where high-temperature structural integrity is maintained, but it won't necessarily make a better space fram chassis than steel.
If you want a strong, torsionally ridgid space frame chassis that weighs less, it could be done using an existing chassis design with thinner-section 4130 tubing instead of mild steel. Even then, the weight savings would be on the order of a few percent, rather than tens of percent. The best way to reduce chassis weight would be to completely re-engineer the space frame design (using FE analysis) to use less material in a better way.
Thanks for explaining that Mark, makes more sense now. I presume from what you have popsted you are referring that Titanium as more tensile strength and less compressive strength. In which case I understand why it would not be such a good idea.
However I was under the impression that Titanium was equal to steel in both compressive and tensile strength. Where can we find some figures?
Regards,
J.P
However I was under the impression that Titanium was equal to steel in both compressive and tensile strength. Where can we find some figures?
Regards,
J.P
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Thanks for explaining that Mark, makes more sense now. I presume from what you have popsted you are referring that Titanium as more tensile strength and less compressive strength. In which case I understand why it would not be such a good idea...
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JP,
What I was talking about is the difference between stiffness and strength. Stiffness is the amount of deflection per unit force. Strength is the unit force required to "break" the material.
Glass has relatively low stiffness while metals are very high. All steels have approximately the same stiffness, even though their strengths may vary widely. It's just a matter of how far they deflect before going plastic. A spring made from soft wire will have the same rate (stiffness) as one made from spring steel up until the metal starts yielding.
I hope that helps.
Thanks for explaining that Mark, makes more sense now. I presume from what you have popsted you are referring that Titanium as more tensile strength and less compressive strength. In which case I understand why it would not be such a good idea...
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JP,
What I was talking about is the difference between stiffness and strength. Stiffness is the amount of deflection per unit force. Strength is the unit force required to "break" the material.
Glass has relatively low stiffness while metals are very high. All steels have approximately the same stiffness, even though their strengths may vary widely. It's just a matter of how far they deflect before going plastic. A spring made from soft wire will have the same rate (stiffness) as one made from spring steel up until the metal starts yielding.
I hope that helps.
JimmyMac
Lifetime Supporter
JP,
Personally I think that fabricating a chassis in Titanium is possible however the cost would really be prohibitive.
I purchased some 2" dia Titanium pipe last year for a personal project and it cost £240 per foot.
A one off chassis design would involve several hundred man-hours of professional engineering work. The usual fabrication tools will not work and qualified welders for Ti alloys are also thin on the ground, so you will need to have your chassis fabricated in a specialist engineering shop, probably not interested in building kit cars. Testing facilities would be another problem.
There are several Titanium alloys available to consider in the design and each have their own particular mechanical properties regarding tensile and compressive loading.
Pure Titanium pipe and sections are also available and are very versatile for more exotic projects demanding low corrosion and extreme mechanical service for example Ti sheet can be explosive bonded to stainless steel plate.
Personally I would prefer an all welded chassis using heat treated alloyed Aluminium - 30 per cent lighter in mass than Ti and a military specification for anodising would prevent the usual corrosion. Sacrificial and charged anodes will also work.
If you really are after some weight reduction and "blow" the cost, you could benefit by removing your stainless piping and installing fabricated thin wall Titanium tube for your exhausts, water and oil jackets but remember hard piping for fuel is generally not used for racing service.
And if you really want to dream - how's about Tantalum ?
Personally I think that fabricating a chassis in Titanium is possible however the cost would really be prohibitive.
I purchased some 2" dia Titanium pipe last year for a personal project and it cost £240 per foot.
A one off chassis design would involve several hundred man-hours of professional engineering work. The usual fabrication tools will not work and qualified welders for Ti alloys are also thin on the ground, so you will need to have your chassis fabricated in a specialist engineering shop, probably not interested in building kit cars. Testing facilities would be another problem.
There are several Titanium alloys available to consider in the design and each have their own particular mechanical properties regarding tensile and compressive loading.
Pure Titanium pipe and sections are also available and are very versatile for more exotic projects demanding low corrosion and extreme mechanical service for example Ti sheet can be explosive bonded to stainless steel plate.
Personally I would prefer an all welded chassis using heat treated alloyed Aluminium - 30 per cent lighter in mass than Ti and a military specification for anodising would prevent the usual corrosion. Sacrificial and charged anodes will also work.
If you really are after some weight reduction and "blow" the cost, you could benefit by removing your stainless piping and installing fabricated thin wall Titanium tube for your exhausts, water and oil jackets but remember hard piping for fuel is generally not used for racing service.
And if you really want to dream - how's about Tantalum ?
Titanium is an exotic material. But even so, its not suitable everywhere. The most important factor for creating a chassis is engineering. A tube welded in the wrong place is of no use, no matter what it is made from.
The Pantera is not very strong as original. My own car was 5000 fp/degree after rebuild with a new and stronger floor.
After a month of work in the twisting bench, I come up with a solution using a cross bracing in there engine compartment.
This stiffened the chassis to 15500 fp/degree! The bars were made from regular aluminum tubing, weighting practically nothing. Moving the bar by only an inch, makes for a smaller number.
My point is, we should concentrate on engeneering, then we can build a fast car, even with a not so thick wallet.
Goran Malmberg
The Pantera is not very strong as original. My own car was 5000 fp/degree after rebuild with a new and stronger floor.
After a month of work in the twisting bench, I come up with a solution using a cross bracing in there engine compartment.
This stiffened the chassis to 15500 fp/degree! The bars were made from regular aluminum tubing, weighting practically nothing. Moving the bar by only an inch, makes for a smaller number.
My point is, we should concentrate on engeneering, then we can build a fast car, even with a not so thick wallet.
Goran Malmberg
You will most certainly not find titanium square tubing because there is no market for it. Titanium in various grades and alloys is available as sheet, round tube and pipe and mainly used for process equipment in chemical plants.
Welding of titanium is a very specialized area. Titanium must be welded in total inert gas atmosphere as it is very reactive at high temperatures. Special measures must be taken to purge the heat effected zone ( also the inside of the tubes) with argon or helium until the weld has cooled down to a certain temperature.
As a rule of thumb: If you retain the metallic shine of the metal, the weld is ok,light coloring may also be ok, but if it looks dull grey,you just lost your mechanical properties and you throw it in the bin.If you want to weld titanium you must be able to purge both sides of the welds. You must engineer and fabricate your frame accordingly.
It can be done at a cost but it is not the same as fabricating a steel or aluminium chassis.
Welding of titanium is a very specialized area. Titanium must be welded in total inert gas atmosphere as it is very reactive at high temperatures. Special measures must be taken to purge the heat effected zone ( also the inside of the tubes) with argon or helium until the weld has cooled down to a certain temperature.
As a rule of thumb: If you retain the metallic shine of the metal, the weld is ok,light coloring may also be ok, but if it looks dull grey,you just lost your mechanical properties and you throw it in the bin.If you want to weld titanium you must be able to purge both sides of the welds. You must engineer and fabricate your frame accordingly.
It can be done at a cost but it is not the same as fabricating a steel or aluminium chassis.
If you want a super light weight chassis, look to the bicycle tubing suppliers, like Prestige, Cinelli, Reynolds, etc. You can get air hardening double butted alloy steel tubes with strength in the 170-180 ksi range with decent enlongation. The fabrication techniques are not that bad, some tubes are suitable for TIG welding, some for lug construction, some for fillet brazing.
Any way you do it, it's a lot of work for only a small ammount of weight saved.
The only thing that makes sense to me is a carbon fiber monocoque construction (vaccume bagged with a foam or honeycomb core of course). You can make a tremendously strong structure with incredible stiffness and light weight also. The materials are not as expensive as titanium tubing, but the cost of molds and layup supplies will make it expensive for one piece. Production of several parts can make the cost reasonable.
Any way you do it, it's a lot of work for only a small ammount of weight saved.
The only thing that makes sense to me is a carbon fiber monocoque construction (vaccume bagged with a foam or honeycomb core of course). You can make a tremendously strong structure with incredible stiffness and light weight also. The materials are not as expensive as titanium tubing, but the cost of molds and layup supplies will make it expensive for one piece. Production of several parts can make the cost reasonable.