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Thread: 3 link axle setup, attaching mount to diff housing.....

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    3 link axle setup, attaching mount to diff housing.....

    Ok, so I have an axle setup on a car which lends itself to a 3 link setup......

    The lower links will be parallel to the ground at ride height using the lower half of locost style axle brackets, and the original spring hangers.



    I had considered the upper links on a 4 link setup but theyre going to be hard to package so I wondered about a 3 link setup, but Im unsure how to attach the top arm to the diff.

    At full compression the housing is VERY close to a crossmember above it but there is plenty of room forward of this.



    Found some better pics....

    Looking at something like this:





    The length of the bottom links is largely fixed, but the top a frame can be as long as needs be.

    Still thinking aloud (and now talking to myself, would there be any adverse effect if I were to use a conventional axle bracket on the axle tube just to one side of the diff housing, and make the A frame a right angled triangle?

    Anyone got any thoughts or experience?

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    Re: 3 link axle setup, attaching mount to diff housing.....

    Alistair,

    Not sure what you mean about the type of diff mounting but,

    Your layout is similar to the Lotus 7 'A' frame which loads a live axle not as it was originally intended and lead to oil leaks and other problems, this is the basic Lotus system:



    The red area (behind the axle) shows how and where these axles needed to be braced to help minimize these problems

    An example:



    Also in the example you show your 'A' frame is the 'upper' connection and as such will have a high roll centre, IMO a live axle already has a very high roll centre to start with so going higher is not the direction i'd choose.

    But I know that Anglia's uses a 'Milton' setup which is still a 4 link but the mounts are either side of the housing and might fit in with your packaging, I'm sure some of the guys using this setup know better about it's behaviour

    Cheers

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    Re: 3 link axle setup, attaching mount to diff housing.....

    Id missed the roll centre height aspect, I should have spotted the correlation between panhard height and this A frame link!

    The milton link sounds a lot like the satchell link?



    Its jut while the bottom links are easy, I'm stuck with the cross member outriggers and any parallel upper links would have to either go through these, or mount to the back of them giving very short arms like the Locost (12 inches or so)

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    Re: 3 link axle setup, attaching mount to diff housing.....

    Sorry when I said the Milton setup was 4 link I mean't that it had two links as the upper part of the 'A' frame as they still use leaf springs with this setup for the lower connection (I think so anyway!)

    Whilst I am not sure (I have tried to get clarification) I believe a 'Satchell' link has the vertex of the 'A' frame bit at the chassis end of the 'A' frame connection (Not that a 'Satchell' is a 3 link but you know what I mean)

    With the 'A' frame setups I have modelled I have found that any side view link angle changes (such as anti squat) can move the roll centre height in a way you are not necessarily expecting, invariably higher than it would be with the links parallel (side view)

    I hasten to add that all the modelling work I have done is not correlated so it is to the best of my knowledge correct but I don't have any physical test data to compare with for live axles, the same simulation software gives the correct answers
    (i.e. correlated with physical data) for pretty well all other suspension types, Macpherson, sla, beam etc...

    The Caterham / Lotus 7's must run with short upper links if they keep thinks within the side bodywork? (well pre IRS anyway) can't you run the upper links outside the bodywork? I'm sure I've seen 7's like this

    Cheers
    Last edited by Aubrey_Boy; 18-05-2010 at 16:31.

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    Re: 3 link axle setup, attaching mount to diff housing.....

    Hmm, so short parallel trailing arms on locost style brackets mounted up the back of the crossmember then!

    Pays to keep it simple at times, it will still be a huge improvement on a leaf located axle with shot bushes!

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    Re: 3 link axle setup, attaching mount to diff housing.....

    That' s about where I am with the Midget at the moment as the packaging sounds similar to yours, 4 parallel links (plan and side view) just getting the links as long as I can but still pretty short but also some adjustment to allow the top links to give some anti squat / roll steer behaviour.

    I am just doing some more work to decide on what lateral location to use but I am lowering the roll centre at the same time via the lateral location mechanism

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    Re: 3 link axle setup, attaching mount to diff housing.....

    Yeah Ive been following you thread with interest both here and on vauxsport!

    I suspect Ill end up with a panhard rod, and I guess the lower the better but as its a road car realistically its not going to be lower than the diff housing!

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    Re: 3 link axle setup, attaching mount to diff housing.....

    Here is a picture of the Milton A Frame on an Escort although more commonly found on Anglias as Escort people tend to stick with the traditional Tramp Bars and Panhard Rod set up.

    Although a recent test in Retro Ford Magazine showed the A Frame significantly reduced the body over axle movement compared to the panhard rod set up.



    And heres one on an Anglia




    Three Links are often found on short oval cars, a few of the Classic Hot Rods I know of have that set up on the rear, how that works on the road I dont know, but it seems to work well on the track.

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