Hi guys,

Having discussed "Losing weight" Ive decided a BEC is the way forward (anyone wanna buy a 2.9 cologne and 4x4 box ) My intention is to use a blade motor and keep the chassis as light as possibe. I'm sure a number of guys here on the forum have already done similar so does anyone have any idea how little a finished car can weigh??

Paul

[Edited on 19/9/05 by paul v6]

MNR have had a VortX RT+ with a fireblade engine weighed at 397kg.
Your choice of components will affect this a lot but I guess if you use lightweight components you can beat this. I believe that the RT+ had a full roll cage not just a braced roll hoop.

That is Light!! In that case my target will be sub 400kg, are there any affordable lightweight components that would help achieve this target??

Paul

Affordabe? Yes. Lightweight? Yes. Both? No!

THe Vortx RT uses sierra bits, heavier steel and has a triangluated roll hoop rather than the full cage. It weighs 30 odd kg more than the RT+. You have to pay lots for the good stuff.

My my secret Excel acceleration model, I estimate that 30kg weight saving will get you 0.2 seconds faster to 60 and 0.5 seconds faster to 100 in an R1 engined car weighing 500kg including the driver vs 470kg including the driver. Only noticable on a race track I think.

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Originally posted by smart51
MNR have had a VortX RT+ with a fireblade engine weighed at 397kg.
Your choice of components will affect this a lot but I guess if you use lightweight components you can beat this. I believe that the RT+ had a full roll cage not just a braced roll hoop.

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397kg sounds too low to me!

My ZX9 Indy weighed in at 468 with half a tank of fuel, thats 71kg less. Where on a 7 style car can you save 71kg???

Hmmm, sounds to me like those figures quoted are VERY optimistic. Chassis and running gear on MNR aren't too dissimilar to those of a MAC#1 or MK.

Without spending Serious cash - and I mean SERIOUS - you'd be lucky to get a car that weighs in at less than 450kg wet.

Realistically, using Sierra running gear (Front Hubs, Calipers, diff etc) you'll probably be around 480 - 500kgs.

Stick lightweight calipers and disks on and you may get the weight down to about 460kg.

After this you're looking at lightweight hubs, Quaiffe diffs and titanium nuts and bolts = ££££££££££££££££

With a blade engine, aim for between 450kg and 500kg (dependant on how deep your pockets are!!)

You can tell those were biased weighing scales... get Chris Mason's calibrated one's in to find a true weight....

[Edited on 19-9-05 by Hellfire]

I don't remember the spec of the MNR off hand. It did have raceleda alloy fronts with solid discs. The RT+ uses thinner but stronger steel in at least some of the chassis. It was in Which Kit as part of their VortX story early on in the year. Ordinary VortXes like mine with the sierra stuff will weigh more of course. The question was "what is achieveable" not "what is commonplace".

My chassis is standard and I have tried to use light weight components where I could. The areas that could be lighter on the MNR compared to mine are the chassis, uprights and any difference in the wheels and tyres. To shave off 71kg I would have to bin all my wheels/tyres and uprights completely

I'd like to be proven wrong, but I don't see how 397kg is achievable with a Seven style car.

Hi

Theres a spec of a nice R1 Striker here

http://www.kerryandjane.com/index.shtml?section=striker&subsection=info

420 Kg's at SVA

Adrian

Always be cautious of the weight at SVA. This is only a combination of the front and rear axle weights and is definitely not the cars true weight.

Its like putting one foot at a time on some weighing scales and then adding the two weights together.

bit of guesswork here

solid front discs are, what, 2kg lighter than vented each?
alloy front calipers 1kg each
alloy uprights and hubs 4kg per side?
thin wall steel in the chassis may save 10kg?
untrimmed seats 2kg each?

that's 28kg. a kilo or so in the wheels and tyres makes up the difference between the vortx RT and RT+ as stated by Which Kit. I bet that there is more than 5kg per wheel and tyre combination between good ones and bad ones

use 0.5mm thinner aluminium for the floor and you could save 2 kg. MNR use a very light radiator and fan. Use a smaller header tank and save 1kg for that litre of coolant just on it's own. Plastic cycle wings will be 1.5kg lighter than GRP for the pair.

Does your car have rear discs. I'm told that drums weigh less, though I can't confirm this.

Interior trim panels must weigh a few kilos. You don't need them all. Have you got a boot box? I bet that weighs 5kg

Of course your car doesn't have a windscreen or heater. Could you fit a smaller battery. Do you have a bike loom and car loom? did you cut out all the wires you didn't need or did you tie them up?

Is your car painted? It sounds silly but paint weighs more than a kilo per litre.

Some things make hardly any difference but added together. lose 70kg from your car? If you are ruthless with the details.

That said, I haven't bothered with mine. Sierra uprights and calipers, LSD, rear disks and vented fronts, boot box, interior trim, GRP cycle wings ... For a road car it makes so little difference. It can be done though and without mentioning carbon fibre.

I know people who have tried all of the above and a lot more besides.

They struggled to get any less than 420kg.

Surely the best way to spend your pennies is to maximise the power to weight ratio which may be better achieved by tuning up the engine for extra horse power and saving a little weight in the obvious areas (unsprung mass etc...).

For example

150 bhp and 450 kg = 333 bhp/tonne
150 bhp and 400 kg = 375 bhp/tonne

160 bhp and 430 kg = 372 bhp tonne
170 bhp and 450 kg = 378 bhp/tonne

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solid front discs are, what, 2kg lighter than vented each?
alloy front callipers 1kg each?
untrimmed seats 2kg each?

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Interior trim panels must weigh a few kilos. You don't need them all.

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Could you fit a smaller battery.

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Do you have a bike loom and car loom? did you cut out all the wires you didn't need or did you tie them up?

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Is your car painted? It sounds silly but paint weighs more than a kilo per litre.

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Originally posted by adam_moore
Surely the best way to spend your pennies is to maximise the power to weight ratio .....

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In my car, one of the heaviest items is the nut holding the steering wheel!

David

[Edited on 19/9/05 by David Jenkins]

Mad Dave,

Wow, didn't expect you go argue point by point. I was just trying to suggest that it is the details that make the difference.

I am told, by the way, that black gel coat is the heaviest. Pink is supposed to be lighter

I'm not arguing, its just to show you that I have tried to make my car as light as I could and it still weighs 468kg. Chris Mason's Blade powered Indy was very similar to mine and weighed a few kg less.

My next build will be lighter still using the same upright/hub assemblies and AP Racing brakes as the Caterham R400. This will save no more than 10kg though.

There's a guy in our car club who sprints a Blade engined road-legal Striker. It has been set up on an accurate flat patch and weighs @390kilos. No bullsh*t.
Just a few pointers in trying to acheive low weight:

A drum- braked Escort live axle is much lighter than a Sierra independent set-up. 30 kgs lighter!! (been lots of discussion on the Caterham 7 website). With an alloy diff. nose it's lighter still.

13" wheels are lighter than 15" wheels. 13" X 6" Revolution 4 spokes are about the lightest readily available 6" alloy you can get hold of. Mine weighed 4kg each on my Striker XFlow. They can be had used for as little as £120 a set.

High tensile cap-head (Allen head) bolts are much lighter than hex-head (and more professional looking).

A VW Polo alloy rad is very efficient and incredibly light compared to a Ford Escort etc.

A Triumph Spitfire steering column and rack is significantly lighter than any Ford you care to mention, and dirt cheap from a Triumph breaker. The standard column cowling is alloy. The rack is quick enough for a Mallock Clubmans car so should be OK on a road car!

I could go on, but I'll be here all day. My GSXR1100W engined Mallock hillclimb car weighed in at 325kgs with a modified Morris Minor rear axle (the diff carrier is alloy as standard!), Triumph rack and uprights etc. The one I'm building now could well have a modified air/oil cooled GSXR1100 motor (no heavy engine coolant and pipe work), and probably not even an oil cooler.

I'm not suggesting eveyone goes out and gets Triumph and Morris Minor stuff! I was just trying to indicate that there is usually a cheap, readily available and lightweight alternative to the usual heavy Sierra gear.

Cheers...

PS

I'm ditching the modified Locost book chassis and building my own from 3/4" and 1/2" 18guage....

I appreciate that the sierra parts are heavy, but I just wanted to build a standard Indy fairly quickly and cheaply. I was originally building it with an open diff and drum brakes, and standard sierra front brakes. Supposed to be a no nonsense track car but when others around were building to a higher spec I didn't want mine to be overlooked so changed to LSD and Wilwoods!

"Triumph and Morris Minor stuff" I know someone who owns a company that manufactures new components for Morris Miners and Triumphs

[Edited on 19/9/05 by Mad Dave]

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Hmmm, sounds to me like those figures quoted are VERY optimistic. Chassis and running gear on MNR aren't too dissimilar to those of a MAC#1 or MK.

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The Cateringvan Supalight is 500Kg FFS... is that a typo?

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Originally posted by marc n

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Hmmm, sounds to me like those figures quoted are VERY optimistic. Chassis and running gear on MNR aren't too dissimilar to those of a MAC#1 or MK.

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hellfire using your mk as a referance

chassis is t45 / cds thinwall mix, weight saving to erw 35 kilos, compared to our standard chassis. dont forget we have a proper integral cage as a stressed member that is structual not bolted.

wishbones t45 as opposed to erw saving .5 kilo per wishbone ( accounting for the fact roadcar has heavy transit drag links and maxi ball joints )

alloy uprights, callipers, drive hubs, drilled discs etc as opposed to sierra, got to be at least 3 kilos a side probably more !!!!drum brake rear end converted to discs, difference between shafts is 2.5 kilos each , diff is 2 kilos lighter, diffrent bearing housings and drive flanges another 1 kilo per side

lightweight bodywork, ( inc carbon fibre ) with return edges no alloy trims etc in cockpit area,
integral dash panel and engine sealing panel in scuttle, plus aeroscreen
alloy footwell panels as opposed to steel

alloy fuel and brake lines

single strand f1 spec wiring loom

just with what i know weigh less we have saved 53 kilos ,
then add the bodywork diffrence etc and you can see where the saving comes from

[Edited on 19/9/05 by marc n]

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pont is many parts are not just a weight saving but also performance enhancing such as uprights ( proper front geometry i.e scrub radius castor etc ) and brakes beleive me when you can brake 8 metres later than a standard setup that is some performance advantage !!!!!

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And all that cost's approximately how much? Which should reinforce everyone's point in the first place...

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Congratulations if you managed it! What was the spec of your orange car at Brands?

orange car was a bit of a mix match to be honest we only built it in a few days,
rt chassis cds cage, big fuel tank etc and upgraded to inboard suspension with rt plus wishbones with no fuel came in at 440 kilos,
so decided i will use this next year as a class b car as its still light enough as i only weigh 63 kilos and i like the colour

[Edited on 19/9/05 by marc n]

The colour is bloody nice!

Still, at 440kg its going go well round the track, out of interest what time did you lap Brands in

[Edited on 19/9/05 by Mad Dave]

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what engine was in it?

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Still, at 440kg its going go well round the track, out of interest what did you lap Brands in

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incidently was running a 3.14 diff and only managed to grab 6th gear 20 metres before the braking point, think a 3.38 may have been better suited

So pretty fast then. What is a decent lap of brands?

can only remember cliocup times 50.8 was pole for one of our drivers in 2003 i think ???

So did the VortX RT+ actually weigh in at 397kg with fluids? If so, I am well impressed.

Oh yeah, and Proven wrong. In which case - APOLOGIES

yep all fluids and 8 litres of fuel takes 14 to fill it as opposed to 28 for the roadcar

it is even lighter today though as the engines come out blew the gearbox at brands!!!, now all the internals are going in a new car for next year so i will have a class a car b car and c car all at current spec suspension wise

[Edited on 19/9/05 by marc n]

I'm not trying to kiss ass here but...

I think this thread just goes to show how much thought and experience Marc has put into his designs...

I did around 14 months of research into the 7 styled kitcar industry before putting down a deposit on a kit.

I met Marc and his Dad at Stoneleigh and then visited him the week after to hand over my money, I was that certain that his design was the best by far...

Just go up and visit them and you'll see what I mean.

Chris.

I had the pleasure of meeting Marc last year - yes, very knowledgeable and experienced. Good set-up and obviously busy as a result of all the development work and continual new products and design's.

It's always nice to be proved wrong IYSWIM - as respect is the result.