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help please
welshboy - 3/10/06 at 05:24 PM

my dad and i have built a book chassis but we have not put in the front wishbone bars fu1 and fu2 yet becouse we cant decide to go with a escort rear axle or a sierra is there big difference i have both it looks like the sierra 1 is bigger so not to sure if it will fit in the standerd book chassis can any one help me please

DIY Si - 3/10/06 at 05:28 PM

The sierra has a +4" track, so it depends wether you are making the fron track wider to match or not. Also, don't place those two tubes until you have the wishbones as they can be an ar$e to place so the brackets are right.

Mark Allanson - 3/10/06 at 05:49 PM

Just like to add that it is not compulsory to have the front and rear tracks of equal width

DIY Si - 3/10/06 at 05:50 PM

Sorry, didn't mean to make it sound like that. You don't have to widen the front at all, but having too narrow/too wide a front track is not best.

mookaloid - 3/10/06 at 07:00 PM

Plenty of westfields have a narrower track at the front......

DIY Si - 3/10/06 at 07:07 PM

Narrower than the rear track or narrower than something else? What I meant was that having it too narrow could affect the handling.

welshboy - 3/10/06 at 07:47 PM

so the sierra is 4in wider then the escort is that right ? so is there anywhere i can get plans to fit the sierra axle and if i fit the sierra will i need wider arches and is there anything else id need to alter ? and id just like to say thanks to everyone for there help we are new to this first time builders !

DIY Si - 3/10/06 at 07:51 PM

Are you aware that the sierra doesn't actually have an axle, like the older escort stuff? It's a diff with drive shafts which have semi (?) trailing arms in the sierra. These are normally converted to use either an IRS or De-Dion set up in a 7. Either way, you'll need wider arches since you have a book chassis.

welshboy - 3/10/06 at 08:03 PM

yep i know that iv got both sat on the workshop floor just cant decide what to use escort looks easyer becouse we could follow book for the front then and would be standerd but if we used sierra i did not know if we needed to widen the front wish bones does any one know where i could get plans to use sierra if we decide to

DIY Si - 3/10/06 at 08:08 PM

There's this one for the IRS.
Damn it's too big.

Try here. This is FlakMonkey's website and has many useful little downloads/programs, such as a tube mitre/fishmouth generator.

[Edited on 3/10/06 by DIY Si]

welshboy - 3/10/06 at 08:24 PM

thanks very usefull whats the differance between the de dion and an irs ?

DIY Si - 3/10/06 at 08:29 PM

You're best bet is to search on here. The irs uses wishbones and the de-dion uses a five link way that a live axle does, but the axle tube merely connects the hub carriers. In both cases the diff is attached to the chassis, and the drive shafts are out in the wind. The live axle and de-dion are better on track, with live being best, where as irs and de-dion are better on the road due to a lower unsprung weight. This is also a long, much discussed topic and is somewhat open to personal preference, so expect to find many different views and opinions.

jonbeedle - 4/10/06 at 08:12 AM

Go with the Escort axle. It's easier and it's more in keeping with the original Lotus 7....if that's what you want!

NS Dev - 4/10/06 at 08:20 AM

agree, if you don't know the answers to those questions then go with the escort axle.

It will be a very good car, and you are probably better handling wise to have a matched narrow track than an unequal track front to rear.

MikeRJ - 4/10/06 at 09:48 AM

Have to agree with Nat, use the Escort axle.

If you are having worries just over the difference in track, then I get the feeling that you may not realise what's involved in using the Sierra components. The only parts you should be looking at using are the diff, the driveshafts and the bearing carriers, hubs, brakes etc. The main beam and the trailing arms are not suitable for a Locost.

If you have built a book chassis, then basicly you can not fit IRS without chopping the rear end off and pretty much starting again.

Alternatively you could buy a De-dion axle and this is much easier than using IRS as the same trailing arms are used, but you will still need to make some modifcations to the rear of the chassis.

welshboy - 4/10/06 at 06:27 PM

whats the difference between a de dion and an irs ?

DIY Si - 4/10/06 at 06:55 PM

This is an example of a independant front suspension. The rear just has a drive shaft and a different hub.

DIY Si - 4/10/06 at 06:58 PM

Try again
Bit like the front really. Well tht's what the pics is, but the overall set up is the same.

[Edited on 4/10/06 by DIY Si] Rescued attachment mojo2fntsusp.jpg
Rescued attachment mojo2fntsusp.jpg

DIY Si - 4/10/06 at 07:00 PM

This is de-dion Rescued attachment de-dion.jpg
Rescued attachment de-dion.jpg

Peteff - 4/10/06 at 07:52 PM

The blue bar is solid and joins the two wheels together and the diff is fixed to the chassis.

MikeRJ - 4/10/06 at 08:19 PM

quote:
Originally posted by welshboy
whats the difference between a de dion and an irs ?


The De-Dion axle is very simmilar to a live axle such as the one from the Escort in that the two wheels are directly linked together, so movement of one affects the other to some extent. The main difference is that instead of the differential being part of the axle, it's fixed drectly to the chassis, and driveshafts with flexible joints (e.g. constant velocity joints) are used to transmit power to the wheels. The idea is that it reduces unsprung weight, which is important on a light vehicle like a Locost in order to get good handling on typicaly rough and potholed British roads. On smooth tarmac it has little or no advantage over a live axle.

IRS is technicaly any rear suspension system where the two wheels can move independantly of each other. The standard Sierra rear suspension is an IRS system. However, in terms of Locosts when people talk about IRS they are usualy talking about a system that uses double wishbones just like the front suspension does.

IRS is far more complex to design as it's behaviour when the suspension compresses or the car rolls is crucial to the handling of the car. With a live axle or De-Dion the wheels always remain at a fixed angle to each other irrespective of how juch the chassis rolls in corners etc.

With most IRS systems the camber of the wheels changes as the suspension is compressed and this behaviour has to be properly controlled to prevent undesirable handling traits.