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Semi Trailing Arm rear suspension discussion
http://www.ozdat.com.au/forum/viewtopic.php?t=10296		 Page 5 of 6
Author:  260DET [ Sun Oct 23, 2016 8:09 pm ]
Post subject:  Re: Semi Trailing Arm rear suspension discussion
Coincidentially I was working on a fully adjustable S14 rear multilink suspension this weekend trying without success to get some dynamic toe in change happening, race car. I'm not a great fan of Nissan multilink, it's certainly an improvement on what went before but really a good double A arm system is better.

As far as the Trailing Arm with Upper and Lower Lateral Links (Bluebird) system goes, thanks for the toe change info Tim, I've been wondering about that and if I could get hold of a suitable suspension programme in due course. For my purposes some dynamic toe in would be good, up to maybe 5mm per side in bump. With the limited suspension movement of a race car, bump control can be less of a problem than with a road car too.

I'm definately going to give it a try, be a while though.
Author:  260DET [ Mon Oct 24, 2016 9:36 pm ]
Post subject:  Re: Semi Trailing Arm rear suspension discussion
On the question of toe change with Trailing Arm with Upper and Lower Lateral Links "TAULLL" suspension, we have discussed that before eg my post 23/8/16 and Honda's solution to the problem which unfortunately is not particularly DIY. However I can see no reason why the arrangement of the lateral links can not be designed so that some dynamic toe in can be gained on bump. Not a lot but some which would certainly be worth while and absolutely preferable to any hint of toe out.

Always assuming that there is space to accomodate the necessary bits in their preferred locations, something that production cars don't always have and which can lead to an inferior compramise. On the C3/4 Corvettes, there are rubber bushes everywhere in them, apparently toe changes due to old damaged bushes and particularly the trailing arm fronts are notorious and scary, see diagram below.

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Author:  xr4x4ti [ Sat Oct 29, 2016 3:26 pm ]
Post subject:  Re: Semi Trailing Arm rear suspension discussion
The simple answer to ensure that you get toe in during bump is to have the two lateral links angling down from the center of the car to the wheels at the normal ride height. Then, as the wheel moves up the distance from the center of the car to the wheel gets longer, since the front of the trailing arm is fixed, the wheel toes in. You obviously don't want the opposite.

Tim
XR4X4Ti
Author:  260DET [ Fri Nov 04, 2016 5:59 pm ]
Post subject:  Re: Semi Trailing Arm rear suspension discussion
That's the plan, of course it's not so good under droop but the idea is to minimumise dive which is always a priority for lots of reasons. In a racing application anyway, it's hella crucial to have toe in gain when the car has been pushed a little bit hard into a corner and wants to kick the back out and spin. At that time the only thing which might save you is some toe in gain, similarly toe out will end it all, sometimes quite dramatically. And how many times in amateur production car racing do we see that :?
Author:  260DET [ Mon Dec 05, 2016 9:20 am ]
Post subject:  Re: Semi Trailing Arm rear suspension discussion
After the trip to Bathurst and driving the 280ZX in anger if not with much skill around that truly daunting circuit, I'm keener than ever to try a TAULLL suspension converted semi trailing arm setup in the Z31 project car.
Author:  SR20Datsun [ Mon Dec 05, 2016 11:15 am ]
Post subject:  Re: Semi Trailing Arm rear suspension discussion
Get cracking Richard!
Author:  260DET [ Wed Dec 07, 2016 8:52 pm ]
Post subject:  Re: Semi Trailing Arm rear suspension discussion
It's coming along nicely, anyone sussed out a suspension software program that I can use?
Author:  SR20Datsun [ Thu Dec 08, 2016 9:10 am ]
Post subject:  Re: Semi Trailing Arm rear suspension discussion
You haven't decided to use the Susprog3D?
Aint nothing wrong with a scale model and a dial gauge!?
Author:  260DET [ Fri Dec 09, 2016 6:57 pm ]
Post subject:  Re: Semi Trailing Arm rear suspension discussion
For one project Susprog is a bit expensive, maybe the demo version will do the job. It's not a project stopper anyway but it would be nice to play around on a screen rather than the alternatives. The Bluebird pic gives a pretty good idea of what's required as far as pivot point locations go and I roughly understand why they are where they are so that's a start.
Author:  260DET [ Sun Dec 11, 2016 12:39 pm ]
Post subject:  Re: Semi Trailing Arm rear suspension discussion
Have now pulled all the rear suspension out of the Z31, first impression is the amount of weight involved, incredible :? Looking at the X member which supports the diff front and the two pivot brackets per side for the STA's it has to be strong, particularly because the inner STA pivots are located about half way along the member each side. But a TAULLL type suspension does not require those inner pivots so that changes requirements considerably.

Still, making a replacement X member would involve some serious jigs so what I'm thinking is to divide the job into three separate pieces, an outer piece each side for the pivots and a front diff mount. The latter would involve a fair bit of metal but if it can also serve as a transmission tunnel brace then that would be OK. These older cars need tunnel braces.

The rest of it is busting my brain at the moment, one part at a time.
Author:  260DET [ Tue Dec 13, 2016 12:44 pm ]
Post subject:  Re: Semi Trailing Arm rear suspension discussion
SR20Datsun wrote:
Get cracking Richard!
Have joined but not paid for the extras http://www.racingaspirations.com/apps/s ... alculator/ Of course the double A arm simulator can be used for my project, so far it's given me a rough idea of the location points, dimensions and angles for the lateral arms.
Author:  260DET [ Fri Dec 16, 2016 6:28 pm ]
Post subject:  Re: Semi Trailing Arm rear suspension discussion
Have ordered some bits to start work on this, actually I'm pretty excited about the possibilities. Just like a double A arm suspension the top lateral arm will be shorter to give negative camber gain in roll/bump, the other thing is there is the prospect of some toe in gain under roll/bump. It probably won't be much but anything which goes against toe out gain is a very good thing.

It looks like the Z31 has heaps of space for a S chassis rear suspension cradle transplant but where is the challenge in that?
Author:  260DET [ Fri Jan 20, 2017 6:35 pm ]
Post subject:  Re: Semi Trailing Arm rear suspension discussion
Seeing that the Z31's OE subframe is being discarded work on mounting the diff directly to the body has started, because racecar it's going to be solid mounted. The rear mounting will be incorporated in a solid bracket bolted to the body at the same place where the OE diff mount was, 2xM10 and 2xM12 bolts. Of course it involves design work as well as fabrication, it can be difficult trying to work out what to do but it's nice when it all comes together.

Where it's really going to get difficult is settling on the lateral arm pivot points locations. Anyone interested in working with this double A arm simulator here http://www.racingaspirations.com/ to advise me on initial locations? For my purposes the results from this programme will be transferable. If I have to then I'll work it all out myself but it would be great to have someone more clued up on this sort of stuff to run some numbers through the programme and advise. All I know now is that the top lateral arm should be shorter than the bottom one to gain negative camber in roll.
Author:  lampy [ Fri Jan 20, 2017 11:28 pm ]
Post subject:  Re: Semi Trailing Arm rear suspension discussion
Great work Richard!
Ill have a go at some simulations when I get some time.
Interesting to see what room you have to mount the arms.
All I can recommend at the moment is the lateral arms be as long as possible to not introduce excessive toe changes under bump/ droop.
Easier in a 280zx, than a 1600 I think
Post some pics if you get time
Author:  260DET [ Sun Jan 22, 2017 11:02 am ]
Post subject:  Re: Semi Trailing Arm rear suspension discussion
Thanks for the offer lampy, on joining that Racing Aspirations site it looks like some simulation enhancements become available including the ability to feed in actual measurements. My idea is to get the diff mounted, that has been started, then the stock semi trailing arms modified firstly to have 3/4"shanked rod ended front pivots. From an engineering point of view it probably would be better to use plain spherical joints there but rod ends give adjustment and hopefully 3/4" rod ends will be stout enough, I use US fine threaded rod ends rather than the coarse thread metric ones.

Making up several alternative pivot points for the diff end of the lateral links should be relatively straight forward, not so for the outers. But that will get done somehow and then measurements to feed into the simulator will become available.
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