Sunday 3rd April 2016

Bicycle tech for Caterham - UPDATE

Price and weight saving estimate released for the butted steel chassis

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Back in October - see the full story below - Caterham released news that it was collaborating with Reynolds to build chassis with butted steel tubing. The aim was to make a Seven even lighter still, while being stiffer and stronger as well.

Now Caterham has announced further details on the project, with a prototype chassis produced through Simpact's Computer Aided Engineering expertise. The interesting news is that Caterham has claimed more than 10 per cent has been taken from the weight of a Seven chassis. Given how light it is already, that's quite some achievement.

As for cost, Caterham is predicting the butted tube chassis will cost between £1,000 and £2,000 as an option. But if you want the ultimate lightweight Caterham...

The prototype chassis will continue to be refined by Caterham in the coming months, with a view to creating a production version "in due course." We'll keep you posted!

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October 26, 2015
As anyone from the more beardy end of the Pedal Powered forum will gladly tell you, butted steel tubing remains the purist's choice of material from which to build a bicycle. Modern-day MAMILs may dote over their flashy carbon fibre or titanium but the 'ping' and feel of high quality butted steel tubes retains a unique appeal and strong following. And in terms of stiffness and weight can actually compare well with more apparently space age materials too, providing an interesting contrast with Ariel's investigations into using titanium for building ultra lightweight (and expensive) Atom chassis.

For the uninitiated, butted tubing has thicker walls at the ends to support welded joins with staged thinning to potentially just fractions of a millimetre towards the centre to save weight. The length of the butts, the sophistication of the alloys used and thickness of the walls are all proprietory tech unique to each manufacturer but, at its best, it can be lighter, stiffer AND stronger than cheap, plain gauge piping, albeit at a cost.

Meaning if your business is building lightweight cars based on tubular steel frames the technology could well be of interest. Step up Caterham, which has announced a collaboration with iconic tubing manufacturer Reynolds and Simpact Engineering to investigate its application in the construction of chassis for its iconic Seven range.

"Our target is to end up with a chassis that delivers a 10 per cent mass saving in weight," says Reynolds Technology's Keith Noronha. "Our butted tubes have contributed to weight reduction in diverse applications from bicycle frames to NASA spacecraft projects. This project aims to prove that car designers can re-think how to use steel - a sustainable and recycleable material - whilst meeting challenging targets on stiffness and driveability. The Caterham Seven should be the first car to incorporate these innovative aspects."

To put the theory to the test Simpact Engineering will use its CAD expertise to 'build' a Seven chassis out of butted tubing and conduct virtual testing ahead of construction of a physical prototype from Reynolds tubing. Support for the project comes from the Niche Vehicle Network, funded by Innovate UK, the Office for Low Emissions Vehicles and the Department for Business Innovation and Skills to illustrate the wider applications of such technology for building simple, cost-effective and lightweight cars.

And if the way of doing that is building a lighter, faster Caterham with the zing of a classic, high-end steel racing bike at its core consider us sold on the idea!

[Ex Boy Racer]

Very interesting. But it reminds me of the people I see at track days, with highly expensive carbon bits and bobs, light alloys, racing seats etc who could save 10 times as much weight by going a bit easier on the pies...

Ps. I admit that my pie input leaves much to be desired too...

[MustardCutter]

I would imagine the zing (i.e. minute deflections / damping) of the steel bicycle frame becomes irrelevant once you introduce car suspension travel with deflections orders of magnitudes greater. I imagine a switch to butted tubes for the 7 will only tangibly yield weight savings. I am suprised they weren't using butted tubes already, the bicycle industry has been using it on spokes and frames of various materials for a long time to save weigth where you don't need the material for strength.

[battered]

MustardCutter said:

I would imagine the zing (i.e. minute deflections / damping) of the steel bicycle frame becomes irrelevant once you introduce car suspension travel with deflections orders of magnitudes greater.

Probably right. The spring of a steel bicycle frame is only of interest when it is the only means of shock absorption other than the pneumatic tyres.

[quote] I am suprised they weren't using butted tubes already, the bicycle industry has been using it on spokes and frames of various materials for a long time to save weigth where you don't need the material for strength.

Cost, basically. The existing 7 chassis has a lot of box tubes. That stuff is dirt cheap and presents nice flat surfaces for welding. Now take round tubes and weld one to another at 90 degrees. Ah, can't just cut them square any more, can you? In addition butted tubes demand that you know the length in advance, because the middle of the tube is too thin to take the braze. That adds cost.

[T0MMY]

Ex Boy Racer said:

Very interesting. But it reminds me of the people I see at track days, with highly expensive carbon bits and bobs, light alloys, racing seats etc who could save 10 times as much weight by going a bit easier on the pies...

Ps. I admit that my pie input leaves much to be desired too...

Worth remembering just how much difference even modest weight savings on very light cars can make though. I'm looking at changing the wheels and tyres on my MNR which alone would drop the weight of the car by 5% at least. If you're "powerfully" built it certainly would be cheaper to lose weight from yourself than your car but it wouldn't be as easy!

[Ozzie Osmond]

"Shiny bits" and "noisy bits" rarely make any difference to performance.

"Oily bits" do, although you can't show them off to your mates quite so easily....

[Evilex]

I wonder if Reynolds have developed a steel alloy specifically for the Caterham application, or if they're using an existing (bike related?) product.

A 753r or 531c sticker on your dashboard would be quite cool.

Some of the alloys are also very corrosion resistant, which can only be good.
Also, the higher quality bike tubes are drawn, not seamed. That'd be nice in the car application, too.

Presumably, Reynolds will effectively manufacture tube "sets" with everything cut and contoured in the right place.
Caterham pop them in a jig, weld them up, clean, powder coat and away it goes.

[scubadude]

Brilliant to see the 50yr old design still evolving and improving, the market for expensive toys seems remarkable alive so Caterham have to keep moving just to maintain their market.

[The Wookie]

Ex Boy Racer said:

Very interesting. But it reminds me of the people I see at track days, with highly expensive carbon bits and bobs, light alloys, racing seats etc who could save 10 times as much weight by going a bit easier on the pies...

Yes but by spending the extra money you get to go faster AND enjoy the pies...

[iloveboost]

MustardCutter said:

I would imagine the zing (i.e. minute deflections / damping) of the steel bicycle frame becomes irrelevant once you introduce car suspension travel with deflections orders of magnitudes greater. I imagine a switch to butted tubes for the 7 will only tangibly yield weight savings. I am suprised they weren't using butted tubes already, the bicycle industry has been using it on spokes and frames of various materials for a long time to save weigth where you don't need the material for strength.

As someone else said it's far more expensive. I doubt anyone mass produces steel tubing with varying wall thickness, which is why they've gone to Reynolds. I guess this may be the final evolution of the seven in it's current form? The Caterham 620R superleggera?!

[Sway]

Evilex said:

I wonder if Reynolds have developed a steel alloy specifically for the Caterham application, or if they're using an existing (bike related?) product.

A 753r or 531c sticker on your dashboard would be quite cool.

Some of the alloys are also very corrosion resistant, which can only be good.
Also, the higher quality bike tubes are drawn, not seamed. That'd be nice in the car application, too.

Presumably, Reynolds will effectively manufacture tube "sets" with everything cut and contoured in the right place.
Caterham pop them in a jig, weld them up, clean, powder coat and away it goes.

I'd imagine their catalogue of steels will cover all requirements...

The tubeset is the only way with butted tubes - which may prevent the outcome being high end models only. Will be interesting to see the difference in BOM costs versus the reduced labour in measuring, cutting, prepping, etc.

[Oz83]

I'm sure they have done their homework but the thing with bike frames is that they don't have to take any sideways loads. I wonder how these butted tube sets fare in the event of a side impact crash.

[lostkiwi]

I wonder if we'll start seeing Caterhams ditched in the canal when they start using old bike frames.....

[AdamAJP]

Interesting tech although I know very little about this bicycle thing (seems to be quite popular however!)

One of my friends went all wobbly at the knees when he saw a carbon fibre framed bike ridden by another bloke in lycra - surely CF (not lycra) is the future as costs reduce...?

Or composites (a la new TVR) from Gordon Murray's iStream tech...
"Rather than stamped steel, iStream uses a tubular frame and a composite monocoque, promoting manufacturing efficiency and reducing weight."

[Barchettaman]

" [the steel] used and thickness of the walls are all proprietory tech unique to each manufacturer but, at its best, it can be lighter, stiffer*AND stronger than cheap, plain gauge piping, albeit at a cost."

• Incorrect. The specific stiffness of the steel doesn't change if you use 'posh' tubing instead of 'gas pipe'. What exotic tubes enable you to do is use thinner walled tubes but retain STRENGTH.

It's one of the reasons my Eddy Merckx Corsa Extra has a 'whippy' feel to it, it's made from Columbus SLX tubing, whereas my commuter (cheap thick-gauge steel) is miles stiffer and consequently better with a fat rider and fully loaded.

I believe Reynolds made exotic thin-gauge steel tubing for British helicopters in the late 1950s so they will have some experience of working with larger-diameter, thin- gauge tubing.

Edited by Barchettaman on Monday 26th October 15:32

[anonymous-user]

I think Caterham should be a bit more concerned about the bigger picture than gains from tubing


edited to add that I think the new metric chassis's feel much nicer than the previous brazed ones.

Edited by anonymous-user on Monday 26th October 15:47

[toobusy]

T0MMY said:

Worth remembering just how much difference even modest weight savings on very light cars can make though. I'm looking at changing the wheels and tyres on my MNR which alone would drop the weight of the car by 5% at least. If you're "powerfully" built it certainly would be cheaper to lose weight from yourself than your car but it wouldn't be as easy!

and much less enjoyable....

[anonymous-user]

AdamAJP said:

Interesting tech although I know very little about this bicycle thing (seems to be quite popular however!)

One of my friends went all wobbly at the knees when he saw a carbon fibre framed bike ridden by another bloke in lycra - surely CF (not lycra) is the future as costs reduce...?

Or composites (a la new TVR) from Gordon Murray's iStream tech...
"Rather than stamped steel, iStream uses a tubular frame and a composite monocoque, promoting manufacturing efficiency and reducing weight."

It's all dependent on the type of carbon and the layup of it, as well as the design of the tubing etc. Actually aluminium is making a bit of a comeback at the moment due new forming techniques. Aluminium used to be harsh but the top end carbon frames are not forgiving at all, the new alloy stuff is just better. Carbon as a material for bicycles IMO is actually pretty crap. It is light but has a shelf life and doesn't crash well. I can't deny there are some amazing designs out there though....at a price

[Jex]

The manufacture of double-butted tube is miraculous. A bar that is thinner at the ends than it is in the middle, known as a mandrel (not to be confused with a mandrill which is a sort of ape, or could be something you keep in a mancave) is put inside a tube, the tube is then drawn so its i.d. is smaller at the ends, giving a greater wall thickness at the ends where you need to make joints. The o.d. is constant along the length. The mandrel is then trapped. It is the miraculous part of the process which enables the bar to be removed. By passing the tube through angled rollers, the mandrel inside can be extracted from the tube. See http://www.reynoldstechnology.biz/materials/how-bu...

[Munter]

yonex said:

It's all dependent on the type of carbon and the layup of it, as well as the design of the tubing etc. Actually aluminium is making a bit of a comeback at the moment due new forming techniques. Aluminium used to be harsh but the top end carbon frames are not forgiving at all, the new alloy stuff is just better. Carbon as a material for bicycles IMO is actually pretty crap. It is light but has a shelf life and doesn't crash well. I can't deny there are some amazing designs out there though....at a price

So just because it works well on a velodrome in an Olympic final, doesn't mean it's the best thing for Brian from accounts to use on his cycling holiday through Derbyshire? Who would have thunk it.

[anonymous-user]

Munter said:

So just because it works well on a velodrome in an Olympic final, doesn't mean it's the best thing for Brian from accounts to use on his cycling holiday through Derbyshire? Who would have thunk it.

It's awesome. Brian buys £8K bike, rides around Richmond park, it rains so Brian goes home. 6 months later Brian puts bike on eBay.

We need Brian.