The lightest kit car?
Discussion
I would say, realistically no. I'm aiming at 450kg for the new bike engined version of the Furore Formula One, the car engined version is obviously heavier. The Mk Sprint is around 400kg in roadlegal trim, maybe a touch lighter, but it's only a single seater. The Malone Skunk is a 2 seater & lighter, but that's a 3 wheeler. I think the Riot is over 400kg?
To get a 2 seater significantly under 400kg with a 1000cc or above engine would require some extensive use of carbon fibre & other exotic materials, could be done but would cost silly money to make it strong enough & light enough. Far better to make it slightly heavier & put a more powerful lump in it, same performance far less cost!
To get a 2 seater significantly under 400kg with a 1000cc or above engine would require some extensive use of carbon fibre & other exotic materials, could be done but would cost silly money to make it strong enough & light enough. Far better to make it slightly heavier & put a more powerful lump in it, same performance far less cost!
I think 350kg is pushing it in terms of overall structural integrity. Cars are the weight they are because, in many instances, they really need to be. If you make the car out of tinfoil and crepe paper it will be light but at the end of your first power run the chassis will be twisted...
My Locost-framed F27 blade has a compact 998cc bike engine/box, no reverse box, no heater, no windscreen, a tiny 3 gallon fuel tank, removable rear lights, no seats, tissue-thin racing-weight carbon-fibre nose cone scuttle and wings, minimal electrics and a tiny battery and still comes in at 420kg. When I add carbon half-doors, a rear venturi an engine-bay undertray and some braced and triangulated roll bars this will probably hit 450kg.
I think that adding a few extra bhp is probably 'easier' than shaving a few kgs off the total weight of the car if it's already fairly light. I know I would be hard-pushed to remove any weight from my own car without resorting to drilling holes in things. An easier way to go is to change to a 'bigger' power unit, or perhaps add a turbo to the one I have...
My Locost-framed F27 blade has a compact 998cc bike engine/box, no reverse box, no heater, no windscreen, a tiny 3 gallon fuel tank, removable rear lights, no seats, tissue-thin racing-weight carbon-fibre nose cone scuttle and wings, minimal electrics and a tiny battery and still comes in at 420kg. When I add carbon half-doors, a rear venturi an engine-bay undertray and some braced and triangulated roll bars this will probably hit 450kg.
I think that adding a few extra bhp is probably 'easier' than shaving a few kgs off the total weight of the car if it's already fairly light. I know I would be hard-pushed to remove any weight from my own car without resorting to drilling holes in things. An easier way to go is to change to a 'bigger' power unit, or perhaps add a turbo to the one I have...
I'm working on a road legal single seater, which I'm confident will be sub-350kg, but as a run-of-the-mill kit car I think you'd struggle... I'm using a composite monocoque tub, a Vee twin bike engine and monoshock suspension amongst the tricks to keep weight down, but with a steel spaceframe 2-seater, it would be very, very difficult.
350kg is easily achievable, with the one small caveat that your name has to be Gordon Murray. The Rocket weighs in at 360kg without fuel, and only limited use of carbon (mudguards & instrument binnacle/parcel shelf).
Engine choice is critical. The Yamaha EXUP motor is very light compared to other bike engines. It's also very stiff - GM used it as a structural member, eliminating several kilos of frame. Many bike engines (and so BECs) are a long way from this strength-weightLayout is also important - more traditional side-by-side seating will add frame and body width, all of which adds weight. To get the Rocket lighter, you would look at:
- Smaller, narrower wheels
- Carbon panels (split into more parts)
- A review of the gearbox/transaxle combination. Fifteen years on I'd consider an 8-speed combined unit
- A use of moncoque structures, or at least replacing cross-bracing with stressed skins.
- A myriad of tiny revisions, each shaving ounces.
For a more traditional road-legal BEC 2-seater, without carbon and without compromising strength and rigidity, I'd say 400kg is pretty damned good. You could:
- Revisit your choice of major systems (engine gearbox)
- Reassess medium systems - can you improve radiator airflow, and fit a smaller radiator?
- Question every last component. Do you need that switch? Can you find a lighter one?
- Then work all of these through the system. If you remove an item, remove the bracket. If you shrink the radiator, fit a smaller nosecone. With the reduced weight, thin down the frame tube.
Engine choice is critical. The Yamaha EXUP motor is very light compared to other bike engines. It's also very stiff - GM used it as a structural member, eliminating several kilos of frame. Many bike engines (and so BECs) are a long way from this strength-weightLayout is also important - more traditional side-by-side seating will add frame and body width, all of which adds weight. To get the Rocket lighter, you would look at:
- Smaller, narrower wheels
- Carbon panels (split into more parts)
- A review of the gearbox/transaxle combination. Fifteen years on I'd consider an 8-speed combined unit
- A use of moncoque structures, or at least replacing cross-bracing with stressed skins.
- A myriad of tiny revisions, each shaving ounces.
For a more traditional road-legal BEC 2-seater, without carbon and without compromising strength and rigidity, I'd say 400kg is pretty damned good. You could:
- Revisit your choice of major systems (engine gearbox)
- Reassess medium systems - can you improve radiator airflow, and fit a smaller radiator?
- Question every last component. Do you need that switch? Can you find a lighter one?
- Then work all of these through the system. If you remove an item, remove the bracket. If you shrink the radiator, fit a smaller nosecone. With the reduced weight, thin down the frame tube.
didn't richard meaden get to a ridiculously low figure with his caterham blade? he did go to extreme lengths (carbon everything) but it went very light. can't remember if it was 290kg or 390kg
www.pistonheads.com/sales/143975.htm
there 369kg
www.pistonheads.com/sales/143975.htm
there 369kg
Edited by ccharlie6 on Tuesday 20th March 13:50
HiRich said:
Engine choice is critical. The Yamaha EXUP motor is very light compared to other bike engines.
That may have been the case back in the early 90's when Murray penned the Rocket, but there are lighter and more powerful bike engines readily available today, the R1 engine for starters is an evolution of the original FZR1000 Genesis/EXUP engine, but a bit lighter and more powerful.
Have a look at this site for an idea on what can be done on a reasonable budget, this Striker R1 weighs in about 390kgs wet, with a splash of fuel.
You are of course correct. But it is still worth remembering that the generic "bike engine" idea is not the full answer. If you are trying to keep weight low, your choice of motor is just as critical as if you were choosing a car engine. You don't just go for bhp/kilo.
I have been told that the Blackbird motor (popular in the early days of BECs) was, whilst powerful, very heavy and with the stiffness of partially-set jelly.
Light weight offers benefits in braking, handling and agility (if done well) as well as acceleration. You shouldn't be seduced by extra power - sometimes the lighter, less powerful motor will give you a faster, more involving car. Having had the opportunity to back-to-back the Rocket with a very well-sorted Caterham (at Llandow), I was astonished most by the difference in how the two cars actually delivered. I really didn't expect them to be quite so different.
I have been told that the Blackbird motor (popular in the early days of BECs) was, whilst powerful, very heavy and with the stiffness of partially-set jelly.
Light weight offers benefits in braking, handling and agility (if done well) as well as acceleration. You shouldn't be seduced by extra power - sometimes the lighter, less powerful motor will give you a faster, more involving car. Having had the opportunity to back-to-back the Rocket with a very well-sorted Caterham (at Llandow), I was astonished most by the difference in how the two cars actually delivered. I really didn't expect them to be quite so different.
Not a kit, and still only at prototype stage, but 385Kg, with a 375BHP V8 engine!
http://dpcars.aprsworld.com/dp1/index
Oh, sorry, not road legal either. Whoops. But still impressive
http://dpcars.aprsworld.com/dp1/index
Oh, sorry, not road legal either. Whoops. But still impressive
Edited by madazrx7 on Wednesday 21st March 12:45
madazrx7 said:
Not a kit, and still only at prototype stage, but 385Kg, with a 375BHP V8 engine!
http://dpcars.aprsworld.com/dp1/index
Oh, sorry, not road legal either. Whoops. But still impressive
http://dpcars.aprsworld.com/dp1/index
Oh, sorry, not road legal either. Whoops. But still impressive
Edited by madazrx7 on Wednesday 21st March 12:45
It looks like it has got inboard disc brakes at the front, but no air flow round them - that'd keep the drivers right foot warm
ETA - sorry, front and rears, but the pics of the car in action seems to show an airvent at the front after all
And it does look very cool
p.s. Tim, have you got the new car now then?
Edited by MTv Dave on Wednesday 21st March 13:10
MTv Dave said:
p.s. Tim, have you got the new car now then?
Edited by MTv Dave on Wednesday 21st March 13:10
Not yet
Still nothing sorted with the settlement yet... Making do with my Dad's old car (he's just bought a new one) in the meantime, and we have a new toy for the track this year, replaced the Series5 (FC) with a Series8 (FD)
Edited by madazrx7 on Wednesday 21st March 14:02
molestrangler said:
Started building a spaceframed glassfibre mini with Suzuki GSXR 1000, not sure what the final wieght will be , but the 2 lay shell can be picked up with one hand,and the tubes are mostly 1" 16swg so should be light. Anyone else tried this?
A lot lighter than my kit car with a 2 litre engine...and i'd guess it's little more than 1/2 a tonne.
My spaceframe is about 1" box section, not tubular and is (no doubt) a much bigger frame.
Let us know and I for one would be interested to follow your project...so some pics please.
Absolutely, the jig has a 2.2 red top in it at the moment as we are building a tubular subframe for another glassfibre mini. I also have to master putting photos on to the site. I am not the most computer competent spannerman. The reason for using seamless tube is two fold, it means that you can bend rather than cut and shut, which looks better , and it is lighter. I have some formula two sidecar guys next door and they build incredibly light structures and talked me into making 16 swg wishbones for my trackday Dutton and they haven't broken yet and they have been worked very hard.
molestrangler said:
Started building a spaceframed glassfibre mini with Suzuki GSXR 1000, not sure what the final wieght will be , but the 2 lay shell can be picked up with one hand,and the tubes are mostly 1" 16swg so should be light. Anyone else tried this?
Westfield did a bike engined spaceframe mini as a production model a few years ago. Difficult to achieve the ultimate in lightnes with a road leagal car, though, 'cos you can't (legally) use polycarbonate for the windscreen and you'll have items like winscreen wiper motors, door hinges and latches etc. that the real flyweight stuff doesn't need. 16 swg isn't especially light tubing, either... properly designed, with decent quality CDS tube, you ought to be using mainly 1" x 18g and 3/4" x 18g if you're really watching the ounces!
Interesting discussion.
Reminds me of the old thread on the se7ens list.
The title was "Should I drill the bolts?"
The poster was asking if he should run a drill down the middle of the bolts holding his back wings on to save weight - seriously.
Opinion was divided, right up to the point when someone pointed out that the guy was 19 stone.
So if you've got a neck like a birthday cake, carbon fibre windscreen wipers aren't going to help a great deal.
Eat less pies or get Kylie to drive it for you, it'll be cheaper in the long run.
Reminds me of the old thread on the se7ens list.
The title was "Should I drill the bolts?"
The poster was asking if he should run a drill down the middle of the bolts holding his back wings on to save weight - seriously.
Opinion was divided, right up to the point when someone pointed out that the guy was 19 stone.
So if you've got a neck like a birthday cake, carbon fibre windscreen wipers aren't going to help a great deal.
Eat less pies or get Kylie to drive it for you, it'll be cheaper in the long run.
Strange thing is, it was never started to be a lightwieght project. A local guy had built a very accurate mould and asked me to make him a trick rear suspension/beam set up and gave me a body from the mould for the price of the materials (£280) and a GSXR 1000 engine fell in my lap...................so what do you do in that situation, you're obliged. And by the way, I'm sure as hell not lightwieght.
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