Mr. Wibble
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| posted on 1/10/09 at 03:03 PM |
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independent rear suspension
Hello gents, I just got my book and was having a look through and was a bit disappointed to see that the book uses a solid rear axle. I was intending
to use wishbones and a bmw rear diff. Has anyone done this? I'm no engineer and wonder if its hard to change the chassis to make this
happen.
Cheers!
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ali f27
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| posted on 1/10/09 at 03:06 PM |
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Hi you need to have second book haynes roadster uses ind back end
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nib1980
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| posted on 1/10/09 at 03:16 PM |
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whats the real advantage of IRS over Live axle in these types of cars...........
mine is Live axle and i cope just as well as IRS
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ali f27
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| posted on 1/10/09 at 03:40 PM |
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Live axle better at drag style sprints but more unsprung wieght irs bracks away later on corners main advantage is cost of lsd with irs
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Mr. Wibble
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| posted on 1/10/09 at 03:44 PM |
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so stick with the irs? i want this thing to shred corners and peel the tarmac off the straights. I'm not much for drag racing. that's why
i'm leaning toward the supra engine
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MikeRJ
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| posted on 1/10/09 at 05:11 PM |
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On smooth roads the live axle works very well indeed, it's when the going gets rough that IRS has the advantage.
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iank
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| posted on 1/10/09 at 05:27 PM |
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Live axles get a bad rap because of 70's rep mobiles running cart springs.
A well located coil sprung live axle with properly valved shocks is a lot better than a badly set up IRS on most surfaces you'd be prepared to
go quick on.
See Mr Procomp's cars for a good example.
--
Never argue with an idiot. They drag you down to their level, then beat you with experience.
Anonymous
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twybrow
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| posted on 1/10/09 at 06:50 PM |
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I agree with the above. Procomp setup my live axle, and it is fantastic! More compliant and smoother ride than I ever thought possible. I took a mate
out for a whole day across the Cotswolds, and he said it rides better than his tintop (Puma). The biggest drawback as far as I can see is the stigma
of having a live axle!
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prawnabie
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| posted on 1/10/09 at 06:53 PM |
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quote:
Originally posted by Mr. Wibble
I'm not much for drag racing. that's why i'm leaning toward the supra engine
Ciruit racing with no corners then lol - sounds like drag racing to me!
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kb58
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| posted on 1/10/09 at 07:19 PM |
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quote:
Originally posted by iank... A well located coil sprung live axle with properly valved shocks is a lot better than a badly set up IRS on
most surfaces.
I read this all the time and never cared for it. Saying that something well done is better than something poorly done isn't a reason. So, if
poorly-educated people make bad engineers, therefore people should not be engineers?
My brother's Super Stalker has a live axle in it. He drove me down a road that had some bumps in in, and hitting them was like someone taking a
hammer to the bottom of the seats. I then had him drive my IRS mid-engine Mini down the same road and he was shocked that he could barely feel the
bumps at all.
IRS versus live axle can be debated either way on the track, but for everyday street driving, nothing beats the ride quality of IRS.
[Edited on 10/1/09 by kb58]
Mid-engine Locost - http://www.midlana.com
And the book - http://www.lulu.com/shop/kurt-bilinski/midlana/paperback/product-21330662.html
Kimini - a tube-frame, carbon shell, Honda Prelude VTEC mid-engine Mini: http://www.kimini.com
And its book -
http://www.lulu.com/shop/kurt-bilinski/kimini-how-to-design-and-build-a-mid-engine-sports-car-from-scratch/paperback/product-4858803.html
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MikeRJ
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| posted on 1/10/09 at 07:39 PM |
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quote:
Originally posted by kb58
My brother's Super Stalker has a live axle in it. He drove me down a road that had some bumps in in, and hitting them was like someone taking a
hammer to the bottom of the seats.
Sounds like he needs to sort the damping and spring rates out then...
FWIW, I agree with iank; the scope for getting a home spun ISR system wrong is vastly larger than hanging a live axle off the car. That's not
a reason not to use IRS of course, but just something to be aware of if you are designing your own with limited experience.
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Steve Hignett
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| posted on 1/10/09 at 07:47 PM |
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The scope for getting a lot of things wrong on a home built car compared to Mr Ford, Mr Vauxhall etc is huge, but there are thousands of people that
are doing so.
I am not disagreeing with you, it's just that I am willing to side with pure facts quicker/easier than "what-could-be's"... If
you know what I mean!
quote:
Originally posted by MikeRJ
FWIW, I agree with iank; the scope for getting a home spun ISR system wrong is vastly larger than hanging a live axle off the car. That's not
a reason not to use IRS of course, but just something to be aware of if you are designing your own with limited experience.
[Edited on 1/10/09 by Steve Hignett]
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Dangle_kt
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| posted on 1/10/09 at 07:50 PM |
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just a thought, but what BHP are live axles and IRS driveshafts able to cope with? A 3ltr twin turbo has to be pretty big BHP and Torque?
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iank
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| posted on 1/10/09 at 08:02 PM |
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quote:
Originally posted by Dangle_kt
just a thought, but what BHP are live axles and IRS driveshafts able to cope with? A 3ltr twin turbo has to be pretty big BHP and Torque?
hicost is putting down 400bhp and 400ftlb through his live axle
--
Never argue with an idiot. They drag you down to their level, then beat you with experience.
Anonymous
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speedyxjs
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| posted on 1/10/09 at 08:05 PM |
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Supra engine 
How long can i resist the temptation to drop a V8 in?
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MikeRJ
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| posted on 1/10/09 at 08:22 PM |
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quote:
Originally posted by Steve Hignett
The scope for getting a lot of things wrong on a home built car compared to Mr Ford, Mr Vauxhall etc is huge, but there are thousands of people that
are doing so.
Getting them wrong?
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iank
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| posted on 1/10/09 at 08:25 PM |
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quote:
Originally posted by kb58
quote:
Originally posted by iank... A well located coil sprung live axle with properly valved shocks is a lot better than a badly set up IRS on
most surfaces.
I read this all the time and never cared for it. Saying that something well done is better than something poorly done isn't a reason. So, if
poorly-educated people make bad engineers, therefore people should not be engineers?
My brother's Super Stalker has a live axle in it. He drove me down a road that had some bumps in in, and hitting them was like someone taking a
hammer to the bottom of the seats. I then had him drive my IRS mid-engine Mini down the same road and he was shocked that he could barely feel the
bumps at all.
IRS versus live axle can be debated either way on the track, but for everyday street driving, nothing beats the ride quality of IRS.
Even on this forum 99% of people are building someone else's design. Sadly many of those are lashed together by kit manufacturers who just weld
stuff together with minimal design work and little engineering, sometimes just copying someone else's design without any idea if it's good
or bad. Those that do don't bother to get correctly valved shocks for their design and use something off the shelf meant for tintops. For some
reason way too many people put springs far too hard on their car.
Has the superstalker been set up properly? From the description it sounds like dampers are the wrong length and/or the springs are too hard (or so
soft it's hitting the chassis ). I've been in live axle 7's that are perfectly civilised over the roads we get in the UK at legal
speeds.
There's no doubt a well set up well designed IRS can beat a live axle, but there are a great number of poor IRS setups around (bad
design, careless/random settings) that are beaten in all areas by a well designed live axle.
--
Never argue with an idiot. They drag you down to their level, then beat you with experience.
Anonymous
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Ivan
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| posted on 1/10/09 at 08:40 PM |
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The reality is that the car will end up weighing around 750 kg what with the extra weight of the Supra engine and drive train together with the extra
reinforcing of the chassis that the weight and power of the motor and drive train will necessitate.
This extra weight will significantly impact on unsprung weight so a live axle becomes a lot more practical.
Then comes the very nature of the motor which is one of extremely high torque which gives a feedback loop of extra weight and bigger tyres which means
more traction which requires a stronger and heavier diff and gearbox which means more weight hence more traction ad infinitum.
The above means that you are going to have to apply your mind whichever way you go - whether it is independent or live axle.
With the independent option you will need something that minimises camber change with squat if you want to retain traction for all out acceleration
but gives the right camber change with roll for cornering - not that easy to do.
Have fun - you've got a lot of thinking to do if you want a car that is balanced in all aspects and a joy to drive and not just something that
spins its wheels with every gentle nudge of the throttle and ploughs straight on in the corner or gives you instant over steer each time your foot
approaches the accelerator in a corner.
Talking of balance - you will have to get front - rear weight balance right as well.
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Mr. Wibble
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| posted on 7/10/09 at 09:52 PM |
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Well gents after absorbing all of your sagely advice i've decided to use the nissan SR20det. i get considerable weight savings and I've
been told that for a 4 cyl it is quiet torqie. and its easy to tune up. replacement turbo's won't require i sell a kidney on the black
market
from a slightly saddened but grateful Mr. Wibble
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Ivan
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| posted on 8/10/09 at 01:39 PM |
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^^^ An excellent choice  
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kennyrayandersen
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| posted on 9/10/09 at 09:17 AM |
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quote:
Originally posted by Mr. Wibble
Well gents after absorbing all of your sagely advice i've decided to use the nissan SR20det. i get considerable weight savings and I've
been told that for a 4 cyl it is quiet torqie. and its easy to tune up. replacement turbo's won't require i sell a kidney on the black
market
from a slightly saddened but grateful Mr. Wibble
I’ve looked at that engine myself. How does it compare sized and weight-wise to say the 4AGE, or 3S-GTE, or the ford 2.0 duratec?
I guess you have to consider the tranny weight as well. The T-50 is pretty light from what I hear (Toyota), the T-9, not so much – I haven’t heard
much talk of the Nissan, so was wondering. I’m not trying to be a weight-weenie, but it all adds up and I was trying to keep it light.
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britishtrident
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| posted on 9/10/09 at 10:17 AM |
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Live axles work very well indeed they give very good camber control, the main downside comes on rougher surfaces because the sprung to unsprung
weight ratio is bad especially on a light car (ie light at the rear corners) traction is also affected by the propshaft torque acting on the rear
axle pinion.
To work properly IRS as to be desgined and set up properly for the vehicle ie. just transplanting the complete IRS from a saloon car to a Locost
without a redesign isn't a good idea.
IRS always performs better on rough or rippled surfaces but with IRS the camber can never be as near ideal as a live axle.
A de Dion rear end combines most of the advantages of both and a Locost is one of the few chassis layouts that has a suitable layout to accommodate
the De Dion tube.
[Edited on 9/10/09 by britishtrident]
[I] “ What use our work, Bennet, if we cannot care for those we love? .”
― From BBC TV/Amazon's Ripper Street.
[/I]
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Theshed
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| posted on 9/10/09 at 01:25 PM |
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"with IRS the camber can never be as near ideal as a live axle"
Really??? on a live axle in any corner the (outside) loaded wheel will always have positive camber - generally not a good thing. With IRS and a roll
bar you can design in whatever camber you want - hence the infinite possibility of a whole load of crap or....that illusive perfect solution.
Anyhow what about that rather neglected concept of the mono-shock - very similar to a live axle but with adjustable camber etc
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brianthemagical
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| posted on 12/10/09 at 12:00 PM |
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With a live axle roll camber is that of static camber + axle roll due to tyre spring rate, i.e, verylow. In bump camber is the angle from static of
the axle, plus static camber, i.e, during bump the camber isn't very good.
For IRS, simply, long swing axle lengths give better bump camber control, with roll camber being controled by the differnce in the wishbone lengths.
As for RC and the consequent roll mements, live axle RC in drive shaft height, giving lower roll moments, and less roll but quicker weight transfere.
IRS allowsthe RC to be placed whereever one desires, and they are ususally much lower, giving bigger roll moments, slower weight transfer, and much
nicer handling.
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