ian.stewart
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| posted on 2/6/16 at 07:29 AM |
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4 bar suspension design
I'm in the middle of putting the rear suspension together a Austin a35 tow van parts getter, I was going down the route of de cambered leaf
springs but I am going to struggle to get the van low enough without using lowering blocks too.
So the option of fitting a 4 bar has been looked at. I do have the luxury of a high floor and a flat vertical panel behind the seats which will be
helpful for mounting brackets. I think I know how to align the bars, logic says parallel, but something says I need to pay attention to the
theoretical intersection of the top bar to the front axle to provide squat? under acceleration ? I think the top bar should have a line that
intersects or runs below the front stub axle ?
So, if that is the case, the design of the 4 bar gets more technical, and now the bars need to be different lengths? to maintain pinion angle
Something different, Very different..............
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hizzi
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| posted on 2/6/16 at 07:58 AM |
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im sure the bars need to be different lengths have a look at some of the stuff on the web about guys converting mk2 escorts to four link and coilover,
companies like ralloy and densport have some good build photos on their sites
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nick205
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| posted on 2/6/16 at 08:16 AM |
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I believe the 4 link bars should be parallel to each other, but that the top bar is shorter than the bottom bar.
One other place to look at this maybe the "Build Your Own Sportscar for £250" book. IIRC that uses a 4/5 bar linkage and solid rear axle
and may show you some dimensions for the links and mounting points.
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Slimy38
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| posted on 2/6/16 at 10:07 AM |
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quote:
Originally posted by nick205
One other place to look at this maybe the "Build Your Own Sportscar for £250" book. IIRC that uses a 4/5 bar linkage and solid rear axle
and may show you some dimensions for the links and mounting points.
Yes it does, but they're not different lengths. All four linkages are the same length.
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ian.stewart
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| posted on 2/6/16 at 11:29 AM |
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Something different, Very different..............
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nick205
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| posted on 2/6/16 at 12:51 PM |
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quote:
Originally posted by Slimy38
quote:
Originally posted by nick205
One other place to look at this maybe the "Build Your Own Sportscar for £250" book. IIRC that uses a 4/5 bar linkage and solid rear axle
and may show you some dimensions for the links and mounting points.
Yes it does, but they're not different lengths. All four linkages are the same length.
Could well be wrong, but from the images posted above it looks like the top linkage is shorter than the bottom?
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Slimy38
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| posted on 2/6/16 at 01:09 PM |
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quote:
Originally posted by nick205
quote:
Originally posted by Slimy38
quote:
Originally posted by nick205
One other place to look at this maybe the "Build Your Own Sportscar for £250" book. IIRC that uses a 4/5 bar linkage and solid rear axle
and may show you some dimensions for the links and mounting points.
Yes it does, but they're not different lengths. All four linkages are the same length.
Could well be wrong, but from the images posted above it looks like the top linkage is shorter than the bottom?
Quite possibly, but neither of those are the £250 book linkages! 
I don't know the ins and outs of equal vs unequal length linkages, I just know that the £250 book keeps things very simple and keeps them the
same length and parallel to each other.
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sprintB+
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| posted on 2/6/16 at 01:30 PM |
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Top link should be about 70% of bottom link length, You are right to find the centre of roll and centre of balance etc. Top link does aim down
slightly at front and lower link may rise slightly. Get them as parallel front to back as possible to avoid binding which will just ruin bushes etc
pretty quickly. Remember to panhard link it to. Loads of stuff on the interweb, you will have conflicting opinions, so in the end you just pick one
that seems the right one. I did my rear end with 5 links and have done my friends hot rod jeep with the same. Transformed the ride and handling, well
worth the effort getting it correct. I also went back to rubber bushes on the chassis and floflex on the axle, seemed to allow more movement and
quieter. My mate has rose joints and blinking noisy they are too.
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nick205
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| posted on 3/6/16 at 07:46 AM |
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Having studied front A arm suspension the top A arm is generally shorter than the bottom A arm. I believe this is done to control front wheel camber
during suspension travel. Granted the rear arms are in a different direction and dealing with a rigid axle across the width of the car, but there may
be some similarity in controlling travel and bush wear on the rear suspension.
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Camber Dave
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| posted on 6/6/16 at 12:19 PM |
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Lots of info above about 5 link or 4 link plus Watts linkage
Search this forum for 'Satchel link'
It works with no chassis needed behind the seats
Mr Satchel is one of the posters.
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