Practical 400kg sports car
Discussion
Big weight savers:
1) Shift linkage. All you really want is a tube leading to the selector and a lever. Cables and guides go all over the place and end up heavier than a single 3/4x.035 tube.
2) Fabric bodywork. Tubular sections that never need to be removed can be covered in Dacron at under 3 ounces per square yard. Fiberglass and even carbon are heavier.
3) Careful battery selection and location. Lithium-iron-phosphate "Zippy" batteries weigh virtually nothing and deliver a LOT of starting current. If you can mount it RIGHT next to the starter, have the starter and battery right by the firewall, and have all the current go through a big CalTerm (Northern Tool, USA) starter button, you will save a lot of wire weight.
4) Kart seats are very light and hold you in very well. You don't want to be in a big broadside or rear-end crash in one; build a good backstop/headstop.
5) Honeycomb sandwich panels absorb energy in a crash very well. Bonding them in can eliminate inconvenient cross tubes that take the shear load.
6) "A poor man blames his tools". 20-gauge (.035") sheet steel weighs twice as much as 26-gauge, which weighs twice as much as 33-gauge. If you have sheets of 33-gauge lying around, you can make lighter parts, and you won't be tempted to leave in big, floppy flat sections. Instead, you'll put good edges on it.
7) A couple carefully-designed wood ribs bonded into a too-light fiberglass section will make it a lot less floppy.
8) If wire's heavy, water's a boat anchor. It's 8 lbs a gallon. Use the smallest radiator you can possibly get away with. The 92-00 Honda Civic radiator is 13 1/2" x 13 5/8" x 1" and is a decent start. There are smaller-capacity motorcycle radiators. If you have trouble cooling the engine you have an aerodynamics problem that most people cover with the bandaid of additional surface area and heatsink size. You need air to enter from a high pressure area and leave in a low-pressure area.
9) Same goes for oil at 6 lbs/gallon. If you have an external oiling system, an ATV oil tank makes a nice little reservoir that'll supply your pressure pump no matter what.
10) Think about your tube diameters and wall thicknesses. You gain stiffness with the third power of diameter and the first power of thickness. Getting rid of a 1"x.095" tube and swapping to a 1 1/2x.035 tube makes a big gain - and your welding to the 1" x .035" tube that connects to it will be easier.
1) Shift linkage. All you really want is a tube leading to the selector and a lever. Cables and guides go all over the place and end up heavier than a single 3/4x.035 tube.
2) Fabric bodywork. Tubular sections that never need to be removed can be covered in Dacron at under 3 ounces per square yard. Fiberglass and even carbon are heavier.
3) Careful battery selection and location. Lithium-iron-phosphate "Zippy" batteries weigh virtually nothing and deliver a LOT of starting current. If you can mount it RIGHT next to the starter, have the starter and battery right by the firewall, and have all the current go through a big CalTerm (Northern Tool, USA) starter button, you will save a lot of wire weight.
4) Kart seats are very light and hold you in very well. You don't want to be in a big broadside or rear-end crash in one; build a good backstop/headstop.
5) Honeycomb sandwich panels absorb energy in a crash very well. Bonding them in can eliminate inconvenient cross tubes that take the shear load.
6) "A poor man blames his tools". 20-gauge (.035") sheet steel weighs twice as much as 26-gauge, which weighs twice as much as 33-gauge. If you have sheets of 33-gauge lying around, you can make lighter parts, and you won't be tempted to leave in big, floppy flat sections. Instead, you'll put good edges on it.
7) A couple carefully-designed wood ribs bonded into a too-light fiberglass section will make it a lot less floppy.
8) If wire's heavy, water's a boat anchor. It's 8 lbs a gallon. Use the smallest radiator you can possibly get away with. The 92-00 Honda Civic radiator is 13 1/2" x 13 5/8" x 1" and is a decent start. There are smaller-capacity motorcycle radiators. If you have trouble cooling the engine you have an aerodynamics problem that most people cover with the bandaid of additional surface area and heatsink size. You need air to enter from a high pressure area and leave in a low-pressure area.
9) Same goes for oil at 6 lbs/gallon. If you have an external oiling system, an ATV oil tank makes a nice little reservoir that'll supply your pressure pump no matter what.
10) Think about your tube diameters and wall thicknesses. You gain stiffness with the third power of diameter and the first power of thickness. Getting rid of a 1"x.095" tube and swapping to a 1 1/2x.035 tube makes a big gain - and your welding to the 1" x .035" tube that connects to it will be easier.
The main reason for not modifying an existing car (such as my Fury), is simply that I want this car to also be jaw-droppingly beautiful. I figure that I'm only going to do something like this once in my lifetime. Because this car will be purely about driver involvement and not lap times and downforce, I've also set myself the much harder objective of creating the most beautiful car I've ever seen.
And people thought hitting the 400Kg weight target was the difficult bit! ;-)
Rob
And people thought hitting the 400Kg weight target was the difficult bit! ;-)
Rob
robcollingridge said:
One simple example of what I'm talking about is this indicator stalk/switch I've fabricated using carbon fibre this weekend. I can do this because I'm using clever electronics, which also mean much of my wiring loom can be 7/0.2 wire (which weighs just 3.5g per meter). This indictor switch will be mounted on the carbon fibre paddle shift and it weighs just 8g.
I'm not saying 400Kg is an easy target to reach but, these are the kind of things I'm doing to make it happen.
Rob
ISIS, MoTeC PDM, OBM or something else? I'm not saying 400Kg is an easy target to reach but, these are the kind of things I'm doing to make it happen.
Rob
wildman0609 said:
You need to take a look at the Porsche 909 berg spider. It weighed 375kg and had a flat 8 in the middle. Some of the weight saving measures are genius. You may need to fit a bigger fuel tank than a Hill climb car though. Also one of the most beautiful cars in existence.
I think 400kg is a very achievable goal, even on the platform the OP already has (though I realise this is not your goal).
Not sure on the exact spec of the OPs existing car, but here's how I see some easy weight being lost from a 450kg BEC:
Swap Compomotive CXRs for Image billet or Barnby rims - 4kg saved
Use the lightest tyres poss - ACB10s or CR500 - another 5kg?
No seat - use self expanding foam inserts - also very comfortable - lets say 2kg
No roll bar - most roll bars on kits are too small anyway and since there is no front hoop, I guess they are next to useless anyway? - an easy 8kg or so?
Using the smallest 6.5" Sierra diff and shafts (assuming not already in use) - about 5kg?
Bike calipers on the back as someone has already suggested - a good couple of kg
Bodywork made from a nice thin layer of woven GRP, not cheap, heavy CSM - say 8kg for a car with as much GRP as the Fury?
I think there could be about 30kg of savings to be made there.
Other easy things to do:
Use socket head bolts instead of hex head, all chopped down to correct size.
Aluminium wheel nuts
Tiny switches
Use Form B washers instead of Form A for all bolted connections(they're thinner!)
Good luck with the project. My advice would be to avoid a carbon tub at all costs. I think you can still hit your 400kg target without it. A simple steel spaceframe chassis can be designed successfully 'by eye', using rules of thumb and experience, and will be very light. Designing using carbon fibre is so much more complicated. If your lightweight steel frame starts to crack, you can weld in extra tubes and gussets. If your carbon tub does the same, it won't be so easy to sort! Save the carbon for bodywork, flat panels or anywhere else you'd use GRP or aluminium sheet.
Not sure on the exact spec of the OPs existing car, but here's how I see some easy weight being lost from a 450kg BEC:
Swap Compomotive CXRs for Image billet or Barnby rims - 4kg saved
Use the lightest tyres poss - ACB10s or CR500 - another 5kg?
No seat - use self expanding foam inserts - also very comfortable - lets say 2kg
No roll bar - most roll bars on kits are too small anyway and since there is no front hoop, I guess they are next to useless anyway? - an easy 8kg or so?
Using the smallest 6.5" Sierra diff and shafts (assuming not already in use) - about 5kg?
Bike calipers on the back as someone has already suggested - a good couple of kg
Bodywork made from a nice thin layer of woven GRP, not cheap, heavy CSM - say 8kg for a car with as much GRP as the Fury?
I think there could be about 30kg of savings to be made there.
Other easy things to do:
Use socket head bolts instead of hex head, all chopped down to correct size.
Aluminium wheel nuts
Tiny switches
Use Form B washers instead of Form A for all bolted connections(they're thinner!)
Good luck with the project. My advice would be to avoid a carbon tub at all costs. I think you can still hit your 400kg target without it. A simple steel spaceframe chassis can be designed successfully 'by eye', using rules of thumb and experience, and will be very light. Designing using carbon fibre is so much more complicated. If your lightweight steel frame starts to crack, you can weld in extra tubes and gussets. If your carbon tub does the same, it won't be so easy to sort! Save the carbon for bodywork, flat panels or anywhere else you'd use GRP or aluminium sheet.
honest_delboy said:
xRIEx said:
For comparison, the R1-powered MEV Atomic weighs a claimed 334kg
Minimal bodywork, small plastic flyscreen, no roof, one seat and half a floor.
It's an impressive ambition, but adding practicality is going to add weight. What materials are you planning to use to keep the weight down?
Looks awesome but there is no way i could live with the guilt of eating breakfast before getting in it. Minimal bodywork, small plastic flyscreen, no roof, one seat and half a floor.
It's an impressive ambition, but adding practicality is going to add weight. What materials are you planning to use to keep the weight down?
stropley said:
honest_delboy said:
xRIEx said:
For comparison, the R1-powered MEV Atomic weighs a claimed 334kg
Minimal bodywork, small plastic flyscreen, no roof, one seat and half a floor.
It's an impressive ambition, but adding practicality is going to add weight. What materials are you planning to use to keep the weight down?
Looks awesome but there is no way i could live with the guilt of eating breakfast before getting in it. Minimal bodywork, small plastic flyscreen, no roof, one seat and half a floor.
It's an impressive ambition, but adding practicality is going to add weight. What materials are you planning to use to keep the weight down?
Cupholders
thinfourth2 said:
stropley said:
honest_delboy said:
xRIEx said:
For comparison, the R1-powered MEV Atomic weighs a claimed 334kg
Minimal bodywork, small plastic flyscreen, no roof, one seat and half a floor.
It's an impressive ambition, but adding practicality is going to add weight. What materials are you planning to use to keep the weight down?
Looks awesome but there is no way i could live with the guilt of eating breakfast before getting in it. Minimal bodywork, small plastic flyscreen, no roof, one seat and half a floor.
It's an impressive ambition, but adding practicality is going to add weight. What materials are you planning to use to keep the weight down?
Cupholders
I reckon 400kgs is easily achievable. An old triumph spitfire with a cast iron engine, heavy gearbox and overdrive, steel rad, steel chassis body tub and wheels weighs in at less than 800kgs.
If we can't do much, much better than that with modern materials, and no interest in girly things like heaters, comfy seats and sound deadening, then I'd not be very impressed...
If we can't do much, much better than that with modern materials, and no interest in girly things like heaters, comfy seats and sound deadening, then I'd not be very impressed...
Watchman said:
It's the style I'm after rather than the fly-weight... but this isn't my thread. I just love the intended style.
I know how heavy the VAG unit is.
I really want this:
But Suzuki won't make it. More details here:
http://www.suzukisport-racing.com/english/product/...
Sorry to hijack but why won't they make it, I flipping love it.I know how heavy the VAG unit is.
I really want this:
But Suzuki won't make it. More details here:
http://www.suzukisport-racing.com/english/product/...
RichyBoy said:
Watchman said:
It's the style I'm after rather than the fly-weight... but this isn't my thread. I just love the intended style.
I know how heavy the VAG unit is.
I really want this:
But Suzuki won't make it. More details here:
http://www.suzukisport-racing.com/english/product/...
Sorry to hijack but why won't they make it, I flipping love it.I know how heavy the VAG unit is.
I really want this:
But Suzuki won't make it. More details here:
http://www.suzukisport-racing.com/english/product/...
I guess the Elise tub might be a decent place to start? It's 68kg, which is probably as light as you could get a steel space-frame and significantly stiffer. Stick on a custom rear sub-frame designed to carry a transverse bike engine; add steering rack, suspension and wheels you should have a powered, rolling chassis at around 200kg? Maybe 250?
Edited by kambites on Monday 9th July 16:25
thinfourth2 said:
Ferg said:
rhinochopig said:
You wouldn't want to drive it in baggy shorts.
or something like that
Gassing Station | General Gassing | Top of Page | What's New | My Stuff