paul v6
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| posted on 20/9/05 at 10:45 AM |
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Axle or IRS??
What do you BEC chaps have in your Locost?
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awinter
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| posted on 20/9/05 at 02:11 PM |
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english live axel in a sylva strika ZX9r
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kb58
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| posted on 20/9/05 at 03:39 PM |
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On a track, both are similar in performance and this reasoning is why many S7s use live axles - it's also simpler and cheaper. However, the
fact is, many/most owners don't drive on the track which makes this argument much less valid due to ride quality. If (and it's not
guaranteed) unsprung weight on an IRS rear end is 1/2 that of a live axle, the ride will be twice as nice. "Nice" means if the car
bounces 1" over a given bump with a live axle, the IRS version will bounc only 1/2" over the same bump. This is an enormously improtant
issue with a car meant to be fun... it makes the difference between a "30-minute car" and a "Two-hour car." Said another way,
it's far more pleasent to drive and as a result you will drive it more. Having the car bound across bumps with the driver's jaw clinched
so he doesn't bite off his tongue isn't fun.
*If* a very light live axle can be obtained, great. But more then likely it'll be an extremely over-engineered, over weight, assembly. Before
you build the car you can, with a bit of research, find what the unsprung weight of each will be, and make a more educated decision.
Better yet, get a ride in a live-axle S7 on some real-world roads. Now get a ride in an IRS S7 on the same road to see how they compare. It really
comes down to you.
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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Memphis Twin
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| posted on 20/9/05 at 07:40 PM |
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Trawling through the Lotus 7 forums I found this.
Live axle full of oil 45kgs
Total de Dion set-up 70kgs
Bearing in mind that the de Dion diff weighs 25kg (Sierra) it clearly shows that the difference in unsprung weight is negligible.
You need a well located live axle! 
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ChrisGamlin
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| posted on 20/9/05 at 08:34 PM |
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But you also need to add to the diff weight half the driveshaft weight, as they are not totally unsprung weight. Also, a proper IRS will have much
better unsprung weight than either.
As an owner of a Live axled car, I agree with what kb58 says, on track there is little advantage with either, but on bumpy roads my live axle is far
worse than my mate's (IRS) Megablade.
Chris
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