RE: Bicycle tech for Caterham
Discussion
Adam Ansel said:
Have you seen the crashes in Caterham racing?
I was in a Caterham club and most members had had a "big one". The chassis is effectively one big roll cage. Far safer than a folded aluminium modern day Lotus that just tears in a crash.
I still say if you are worried about crash safety go & buy something other than a small, lightweight car. I was in a Caterham club and most members had had a "big one". The chassis is effectively one big roll cage. Far safer than a folded aluminium modern day Lotus that just tears in a crash.
Am I allowed to avoid a discussion Caterham 7 vs Elise now please?
Equus said:
George111 said:
My Dax Rush Bike engined chassis (with the RAC roll cage as above) is all round tube, built in 2002 well before Caterham thought of using it.
I hate to disappoint you, but Caterham, and Lotus before them, have been using round tube on the Seven since the late 1950's.
This all looks a bit square to me . . . http://www.mycaterham.com/117516/117447.html
As you'll know Arch used to (still do ?) make chassis for Caterham. Sure there are some round tube components but the majority is square.
Adam Ansel said:
Far safer than a folded aluminium modern day Lotus that just tears in a crash.
The Elise is extruded aluminium, not folded, and have you seen the crash test results for one?It performed extremely well; they could have basically just bolted on a new front crash box and driven it home...
Equus said:
The Elise is extruded aluminium, not folded, and have you seen the crash test results for one?
It performed extremely well; they could have basically just bolted on a new front crash box and driven it home...
That's what they did with the Evora crash tests wasn't it. Crash, bolt on a new front, crash test #2, bolt on another front, repeat... It performed extremely well; they could have basically just bolted on a new front crash box and driven it home...
Equus said:
The Elise is extruded aluminium, not folded, and have you seen the crash test results for one?
It performed extremely well; they could have basically just bolted on a new front crash box and driven it home...
A real world crash is not usually a single impact, like the tests are.It performed extremely well; they could have basically just bolted on a new front crash box and driven it home...
Talk to an accident repairer about what happens to aluminium in impacts.
See video: https://www.youtube.com/watch?v=nuIijDlH1PI
Adam Ansel said:
Equus said:
The Elise is extruded aluminium, not folded, and have you seen the crash test results for one?
It performed extremely well; they could have basically just bolted on a new front crash box and driven it home...
A real world crash is not usually a single impact, like the tests are.It performed extremely well; they could have basically just bolted on a new front crash box and driven it home...
Talk to an accident repairer about what happens to aluminium in impacts.
See video: https://www.youtube.com/watch?v=nuIijDlH1PI
"10% lighter and stiffer and stronger"
Does it need to be stiffer and stronger? I wonder how much lighter it would be if it was the same stiffness and strength?
Since they are making it stronger the existing apparent stiffness would increase anyway with less load to unstiffen it, I suppose to maintain the "feel" could they not make a lighter chassis less stiff?
Seems rather unChapman-esque to make it better than it needs to be :-)
Does it need to be stiffer and stronger? I wonder how much lighter it would be if it was the same stiffness and strength?
Since they are making it stronger the existing apparent stiffness would increase anyway with less load to unstiffen it, I suppose to maintain the "feel" could they not make a lighter chassis less stiff?
Seems rather unChapman-esque to make it better than it needs to be :-)
Adam Ansel said:
A real world crash is not usually a single impact, like the tests are.
Talk to an accident repairer about what happens to aluminium in impacts.
See video: https://www.youtube.com/watch?v=nuIijDlH1PI
I see your irrelevant video, and raise you this one.Talk to an accident repairer about what happens to aluminium in impacts.
See video: https://www.youtube.com/watch?v=nuIijDlH1PI
Mr2Mike said:
Adam Ansel said:
A real world crash is not usually a single impact, like the tests are.
Talk to an accident repairer about what happens to aluminium in impacts.
See video: https://www.youtube.com/watch?v=nuIijDlH1PI
I see your irrelevant video, and raise you this one.Talk to an accident repairer about what happens to aluminium in impacts.
See video: https://www.youtube.com/watch?v=nuIijDlH1PI
Have you never encountered one of the millions of real-world crashes where dozens of pixies jump out of the hedgerow and tear your doorskins off with pliers?
It all seems a bit 1980 with all this? Butted tubes are good, but you would hope that they have moved on from this.
Steel alloy frames are liked because in a road bike as they have flex, the flavor of chrome molybdenum and other mixtures was part of the mix back in the 70's.
Aluminium is very stiff and is a 'dead' metal hence the bloke with pliers video. But a 1/3 of the weight.
Titanium alloys are used to get the same weight and feel of steel, but the weight of aluminium.
However Carbon fiber took over from this as it lighter than all of them. Hence why F1 cars have used it and in the last 10 years production cars.
The main issue with carbon fiber is that strings of carbon don't like compression so weaving it in the way you want has become an art.
The question is why Caterham isn't just going for Forged carbon composite which has none of the directional issues as it is pressed into the shape that the engineers want.
Steel alloy frames are liked because in a road bike as they have flex, the flavor of chrome molybdenum and other mixtures was part of the mix back in the 70's.
Aluminium is very stiff and is a 'dead' metal hence the bloke with pliers video. But a 1/3 of the weight.
Titanium alloys are used to get the same weight and feel of steel, but the weight of aluminium.
However Carbon fiber took over from this as it lighter than all of them. Hence why F1 cars have used it and in the last 10 years production cars.
The main issue with carbon fiber is that strings of carbon don't like compression so weaving it in the way you want has become an art.
The question is why Caterham isn't just going for Forged carbon composite which has none of the directional issues as it is pressed into the shape that the engineers want.
sisu said:
However Carbon fiber took over from this as it lighter than all of them...
Ironically, at exactly the same time Caterham unveiled their butted tube spaceframe, Westfield unveiled their new low-cost carbon fibre spaceframe prototype (they did the carbon fibre monocoque 'Seven' the best part of two decades ago), powered by an ultra-lightweight rotary engine. Both projects were part funded by the same 'Innovate'/Niche Vehicle Network funding initiative, and both were formally unveiled at the annual NVN symposium a couple of weeks ago.
Of course, this being PistonHeads, Westfield are not nearly over-hyped and over-priced enough to be worth reporting on.
Given that Caterham has recently had sister companies in F1 and composite technologies I would guess there is a good reason they have not gone down the CF route. No idea what the reason is, but it is definitely not lack of expertise or access to the cost, so I can only assume there is a good reason.
A few inaccuracies worth correcting.
Aluminium is not very stiff. It is 1/3 of steel.
Titanium has a higher density than aluminium.
Carbon fibre is typically the same density of aluminium.
Materials are often chosen for their strength weight ratio, joint interfacing and manufacturing method.
Forged carbon fibre parts are not as light as fibre direction optimised parts.
Carbon fibre tubes are good but still require aluminium inserts where parts are clamped together.
Repairability is also a significant factor. How many owners would want to return their car to the factory after a minor shunt.
Not insurmountable problems but neither trivial.
Aluminium is not very stiff. It is 1/3 of steel.
Titanium has a higher density than aluminium.
Carbon fibre is typically the same density of aluminium.
Materials are often chosen for their strength weight ratio, joint interfacing and manufacturing method.
Forged carbon fibre parts are not as light as fibre direction optimised parts.
Carbon fibre tubes are good but still require aluminium inserts where parts are clamped together.
Repairability is also a significant factor. How many owners would want to return their car to the factory after a minor shunt.
Not insurmountable problems but neither trivial.
wemorgan said:
Carbon fibre tubes are good but still require aluminium inserts where parts are clamped together.
Not with the system that Westfield is using.wemorgan said:
Repairability is also a significant factor. How many owners would want to return their car to the factory after a minor shunt.
Similar issue with butted tubes, though - you can't just pick up a length of Reynolds tube butted in the correct places at your local steel stockholder.Talking of accidents, would anyone care to speculate on how predictably the ultra-tin walls of a butted tube spaceframe will fold up in the event of a crash?
Equus said:
Talking of accidents, would anyone care to speculate on how predictably the ultra-tin walls of a butted tube spaceframe will fold up in the event of a crash?
I gather that crash simulations have been performed. I don't know the results, but imagine comparable performance to the regular steel was a target.wemorgan said:
I gather that crash simulations have been performed. I don't know the results, but imagine comparable performance to the regular steel was a target.
The problem with simulations is that they're not able to simulate the often complex circumstances of real-world accidents. You can run a 'simulated' chassis head-on into a 'simulated' concrete block, for sure (and even simulate diagonal front impacts), but the sort of racing accident that sees a car bounced end-over-end, or ricocheting between the armco and other traffic?
Let's be clear, the butted steel tubes that Caterham are using are regular steel (not any of Reynolds fancy alloys), just much thinner, except at the node points.
Equus said:
wemorgan said:
I gather that crash simulations have been performed. I don't know the results, but imagine comparable performance to the regular steel was a target.
The problem with simulations is that they're not able to simulate the often complex circumstances of real-world accidents. You can run a 'simulated' chassis head-on into a 'simulated' concrete block, for sure (and even simulate diagonal front impacts), but the sort of racing accident that sees a car bounced end-over-end, or ricocheting between the armco and other traffic?
Let's be clear, the butted steel tubes that Caterham are using are regular steel (not any of Reynolds fancy alloys), just much thinner, except at the node points.
It's exactly the same principle as the NEDC, we know it's nothing like real life but merely gives a controlled benchmark.
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