Lotus Elan

Lightening 26R Style Chassis

PostPost by: stevebroad » Sun Jun 23, 2013 9:10 am

My chassis has been modifed to 26R tune and beyond. I am now looking to remove weight from where is is not needed using flared holes of various diameters. But where to start? There are some large areas of flat sheet that Lotus didn't put flared holes into. Was this by design or due to cost?

Has anyone on here successfuly done this?

No, I don't want to fit a Spyder chassis, thanks.
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PostPost by: jimj » Sun Jun 23, 2013 9:39 am

Steve, you may only be broad by name and too slim to diet but I can`t help but think that the amount of weight you could remove would be so small that it would be more effective to miss breakfast.
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PostPost by: msd1107 » Sun Jun 23, 2013 8:45 pm

There are five main aspects to performance. Cornering, braking, acceleration, top speed, and fuel economy.

All are negatively affected by weight.

Thus subtracting weight is the most effective method by which to increase performance.

You may turn up you nose at just losing a few pounds. But doing this in a comprehensive manner throughout the car leads to substantial weight losses and corresponding performance gains.

Maybe we could start a thread on weight loss techniques to find out how low we can go and retain a streetable car.

David
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PostPost by: Panda » Mon Jun 24, 2013 5:33 am

Hi Steve, I have recently completed building a 26R replica. The new chassis weighs 41.5kgs bare and I didn't try to lighten it at all. I have managed to get the weight of the complete car with all oils, coolant, fluids, fire extinguisher etc, but no fuel, down to 567kgs. I have used lots of alloy bits, diff housing, gearbox casings, bellhousing, fuel tank,radiator and dry sump. I paid a lot of attention to shortening bolts and using K nuts where possible. I would have been worried about losing stiffness by lightening the chassis.
We are planning the next step which will be fitting an alloy block, this will save about another 19 kgs!
cheers

Alan Pate
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PostPost by: stevebroad » Mon Jun 24, 2013 2:47 pm

With the mods made to take a Cosworth 7 1/2" diff plus triangulating wherever possible to 26R spec and more, my chassis topped out at 51.6kg! So, anything I can remove from it will be welcome :-)

I hope to get the car below 700kg but it is going to be a struggle.

K-nuts are very expensive so I have had to make do with half nuts. However, I have turned down bolt heads. I have also centre drilled bolts that aren't in single shear or critical such as suspension mounting bolts.

Weight has been removed from every component that can afford it or lightweight replacements designed and made (fully adjustable (insitu) for camber and caster aluminium front top wishbones for example).

What power output are you aiming for and do you intend to race or play?
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PostPost by: stevebroad » Mon Jun 24, 2013 2:52 pm

jimj wrote:Steve, you may only be broad by name and too slim to diet but I can`t help but think that the amount of weight you could remove would be so small that it would be more effective to miss breakfast.
Jim


An old racing car builder friend said to me many years ago, once you have removed the easy stuff, to remove another pound take an ounce from 16 places. Each ounce, on its own, is negligable. However, one ounce from 160 places is 10 pounds!

And I can still miss breakfast :-)
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PostPost by: Panda » Mon Jun 24, 2013 10:35 pm

Steve, we have competed in 3 Supersprints since completion in the Combined Sports Car Association events with great success, winning our class C2 easily and seeing off a lot of much later model cars.
The engine was dynoed last year at 201hp. It is a 711M block all steel with two 45's and a very good head.
Dynos obviously vary, but speed on track relative to the competition tends to confirm the number. We are still running with the 4 speed box with Quaife straight cut gears. We are hoping for much more torque to get out of the slower corners with the new 2.0l alloy block when it is installed.
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PostPost by: stevebroad » Tue Jun 25, 2013 12:10 am

Panda wrote:Steve, we have competed in 3 Supersprints since completion in the Combined Sports Car Association events with great success, winning our class C2 easily and seeing off a lot of much later model cars.
The engine was dynoed last year at 201hp. It is a 711M block all steel with two 45's and a very good head.
Dynos obviously vary, but speed on track relative to the competition tends to confirm the number. We are still running with the 4 speed box with Quaife straight cut gears. We are hoping for much more torque to get out of the slower corners with the new 2.0l alloy block when it is installed.
Alan Pate


Hi Alan
My old twincam had 168bhp at the wheels back in 1984 so probably similar outputs (also a Quaife straight cut 4 speed). Are you still at 1558? If you are then that is very impressive power as mine was just over 1700cc.
Steve
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PostPost by: Panda » Tue Jun 25, 2013 12:47 am

Steve, my engine is 1708cc to be precise. On the dyno, I did have a pair of cams which produced 213hp but the revs were too high and not enough low down torque. We have rev limited it to 8500 rpm to extend the life of the engine and even now it doesn't like to be under 6000rpm.
Most of the mechanical bits came from my old S4 race car which was pretty quick despite being about 60kg heavier. I have been a little disappointed that on the track we as yet, aren't as quick with the new car. But it's early days and with a bit more tweaking to the suspension/steering we should get an improvement.
cheers

Alan
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PostPost by: stevebroad » Tue Jun 25, 2013 10:25 am

Alan

Low down torque was always an issue with these over square powerplants, but they do love to rev :-)

At the risk of trying to teach you to suck eggs, I assume that you are using a 4:2:1 manifold to improve low end torque?

Getting the suspension right is much more important, IMO, than extra BHP. What damper/spring set up are you using?

Regards

Steve
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PostPost by: Panda » Tue Jun 25, 2013 12:18 pm

I am using a TTR big bore 4 into 2 into 1 exhaust. Suspension is rose jointed fully adjustable 26R cranked bones in front with TTR rose jointed shocks, big anti roll bar and 325lb springs. rear is similar with Koni top adjustable shocks, Kelsport rose jointed wishbones and 180lb springs. I have made and fitted a 1/2 inch rear roll bar, but have found excessive oversteer, so is disconnected at present. Brakes are Girling AR front and NR rears with dual circuit adjustable balance bar cylinders. Tyres are 205/60 Kumho V700. We can't run slicks in our class. Wheels are 13" by 6" mag. 26R knock ons. Alignment is 2 degrees negative all round, 4 degrees caster, 1/8th front toe in and 3/8th rear toe in.

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PostPost by: stevebroad » Tue Jun 25, 2013 1:32 pm

Panda wrote:I am using a TTR big bore 4 into 2 into 1 exhaust. Suspension is rose jointed fully adjustable 26R cranked bones in front with TTR rose jointed shocks, big anti roll bar and 325lb springs. rear is similar with Koni top adjustable shocks, Kelsport rose jointed wishbones and 180lb springs. I have made and fitted a 1/2 inch rear roll bar, but have found excessive oversteer, so is disconnected at present. Brakes are Girling AR front and NR rears with dual circuit adjustable balance bar cylinders. Tyres are 205/60 Kumho V700. We can't run slicks in our class. Wheels are 13" by 6" mag. 26R knock ons. Alignment is 2 degrees negative all round, 4 degrees caster, 1/8th front toe in and 3/8th rear toe in.

Alan


Can't see anything wrong with that spec :-)

We are running 800lb fronts with helpers (they may not be needed once car is assembled) and 400lb rears with 450lb tenders. We hope to run without ARBs by using droop limiters. Don't ask me how it works, I am just doing what my suspension guru tells me :-)

Camber, caster and toe will probably be similar to yours with at least 3 degrees caster. Don't know what the rear camber will be yet, I am leaving that to my chassis guru.

By the way, how did you adjust the caster?

Steve
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PostPost by: el-saturn » Tue Jun 25, 2013 2:23 pm

then there's all of these other lovey BUT EXPENSIVE paths: CFRP, Honeycomb, Titanium, more chrome-moly, where legal machined components which start at 100% weight and loose 97% thereof. i imagine, if someone
were to go all the way (composite tub and body), k-nuts, low weight everything and aircraft type machined parts
you could probably work for 5 years on it (2000hrs x 5 x 100£ ) and even neglect the material (100000£) BUT it would set you back by a million quid -------------------------- so go for it jay leno and quit wasting your time: ain't I awful .................. and jay, if U read this: I'm sorry! 36 / 4982 sandy
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PostPost by: Panda » Wed Jun 26, 2013 6:10 am

Steve, I only upped the caster by one degree, which was easily done by fitting thick and thin alloy spacers to get the bottom wishbones fully forward and the top ones fully back. Keep in mind the rose joints are much narrower than the original bushes. I don't think I am stressing the trunnion as everything is very free with the springs removed. I used to use Canley Classic trunnionless uprights, but the mounting angle with the cranked bones was causing "necking" in the joint.

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PostPost by: rgh0 » Wed Jun 26, 2013 12:12 pm

[quote="stevebroad We are running 800lb fronts with helpers (they may not be needed once car is assembled) and 400lb rears with 450lb tenders. We hope to run without ARBs by using droop limiters. Don't ask me how it works, I am just doing what my suspension guru tells me :-)

Steve[/quote]


The spring rate of the chassis is lower than that of your suspension :lol: . You must have smooth tracks and love racing go carts

cheers
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