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PostPosted: Fri Jan 27, 2017 6:39 pm 
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Location: WARWICK, Q.
Well it's begun, metal has been chopped so there is no going back :| There will be some pics to come in the next few days, basically all that will be used from the entire rear suspension and diff mount assembly will be the suspension arms, converted from semi to trailing. Instead of being mounted to the stock sub frame both the diff and suspension arms will work with made up brackets attached to the body reinforced as required. Diff has been done already, fairly straight forward which I managed to over think.

Stay tuned, as far as I know this is a world first and one which I'm determined to make work to a serious race car standard.

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PostPosted: Sun Jan 29, 2017 3:48 pm 
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Have got as far as solidly mounting the diff and making up the body bracket for the left trailing arm's pivot point, the latter was a fair bit of work because it had to be mounted as high as possible so that the trailing arm will work at a suitable angle. Ended up making a removable bracket so that the pivot bolt could be accessed, it sits in a pocket. The first pic shows a mock up of the arm in place so it clears the body but that makes the track around 30mm wider than stock, with it mounted closer in the arm hits the body. Not sure what's going on there, maybe the track measurements I have are the wrong ones.

Just remember when looking at the pics that the car is on a rotisserie at about 90 degrees, the main build thread for the car is on Auszcar but seeing that there is interest in the suspension here that will be covered in this thread.


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PostPosted: Mon Jan 30, 2017 10:26 am 
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Good to see you are making some progress on this Richard!

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PostPosted: Wed Feb 01, 2017 6:00 pm 
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Two steps forward, one back, typical :) Anyway, pics tell the story mostly. The first photo is turned right side up to be more understandable and shows the two lateral links concept mocked up, at the left is the hub and to the right is the diff and it's 'big for a reason' mount. Just looking to see how the links may be mounted, hmmm.


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PostPosted: Fri Feb 03, 2017 6:34 pm 
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The lateral link pivot brackets are working out quite nicely, there will be multiple alternative locations for the upper and lower pivots so that, hopefully, it will be possible to locate the links so as to give the best locations for handling purposes. In order to keep the bracketry at the hub as light and simple as possible for unsprung weight reasons, the more complicated short top and longer lower links bracketry will be located near the diff.

More pics in a day or two, I'm really enjoying working this sh*t out :thumbsup: well until it comes to the actual alignments required to get all this working to race standard :)

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PostPosted: Sat Feb 04, 2017 3:53 pm 
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Great work!

I haven't had a chance to do some simulations on the arm lengths and angles. Hopefully soon!

I would probably mock it all up with temporary brackets that you can adjust easily and then run it through the expected travel. See what toe/camber change you get.

When I was building my racecar I had it on a two post hoist and clamped a straight edge to the arms of the hoist parallel to the car/front wheel
I then put a rim on the rear hub and clamped a 5mm flat piece of sheet metal to the outside of the wheel face.
I then adjusted the straight edge so it was about 10mm away from the plate
I then used a jack to raise and lower the rear suspension.
Toe was determined by measuring the difference between the front and back of the plate to the straight edge
Camber was determined using a digital protractor from the straight edge to the plate

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PostPosted: Sun Feb 05, 2017 3:05 pm 
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Thanks for the encouragement blokes, at the stage now where the lengths of the shorter upper link and longer lower link have to decided upon, only problem is I don't have any hard info on what the ratio should be. Info on A arm suspension arm lengths would be useful but I've searched before with no luck.

Am starting now to collect various measurements required to use the A arm simulator http://www.racingaspirations.com/ once you join up it's possible to input all the required measurements and then change pivot point locations to try different combinations. My setup is of course fully adjustable so that the best results can be transferred to it.

Any helpful comment on the above is welcome as usual.

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PostPosted: Sun Feb 05, 2017 6:30 pm 
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OK, no messing around here, at last I found some info that looks like it should be useful, from a US replicar maker no less :wink: It shows what looks like a screen shot from a simulator and from what I've seen is worth giving a go for the basics, the upper short arm to lower longer arm ratio works out close to 2:3 which now gives me something to work with.

The one on the right, green is at static ride height.


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PostPosted: Mon Feb 06, 2017 5:34 pm 
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Suspension blokes, I'd appreciate it if you could look at page 11 here http://www.mechanics.iei.liu.se/edu_ug/ ... elat18.pdf and tell me what you think of the setup, it looks like it's taken from a simulator. The upper/lower links measure out at a ratio of 2:3+, note the roll centres and cambers in the various scenarios, note also that there is 2 degrees roll modeled which I think is about as much as you'd want, particularly with a race car.

The lower link on mine is about 550mm long, the final length does not have to be decided until there is a complete set of other relevant measurements and they have all been run through Racing Aspirations A arm simulator. The above looks like a good starting point, what do you think?

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PostPosted: Tue Feb 07, 2017 12:28 pm 
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It looks familiar to me. I think I have seen this in a text book. Not sure if it's from one of the Tune To Win from Carroll Smith or Chassis Engineering by Herb Adams. I think it's from Tune to Win.
Who ever it is, they talk about making 'cardboard models' and testing the geometry with a protractor etc.
It looks like a fair chunk of camber change through bump, but without measuring the bump distance, I am not sure....

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PostPosted: Thu Feb 09, 2017 6:25 pm 
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Now at the stage where there is enough info available from what has been tack fabricated so far to feed the simulator, see pics and note that the 540mm long lower link is only a dummy which shows my preferred location. Roughly horizontal is a good place to start to get the target 100mm roll centre.

The length of the upper link will work itself out, the simulator process involves moving the upper inner pivot point up/down in/out and observing the resulting data to find the best compromise for the intended purpose. From the little bit of playing done so far it's looking promising. :)


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PostPosted: Fri Feb 10, 2017 9:04 am 
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Coming along nicely!

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PostPosted: Fri Feb 10, 2017 6:01 pm 
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Once there is a simulator produced setup that I like it will be posted up for you blokes, it is going to look weird because both links have to be low otherwise there will be insufficient bump travel because the upper arm will hit the chassis. The chassis would be modified, a hell of a job, if necessary in order to get the right figures but so far it's not. This process is a big learning curve for me but at present I'm looking at camber, roll centre and instantaneous roll centre figures in increments of one degree with up to five degrees body roll.

As far as instantaneous roll figures go I'm not too clued up about them, so far they have been located near the roll centre which seems OK to me. At least it looks tidy :mrgreen:

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PostPosted: Sat Feb 11, 2017 5:03 pm 
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Put a couple of slight variations through the simulator, only tested roll so far, not bump and roll. The figures for the best one are: zero static roll has -2.5 degrees camber, 94mm roll centre. 1 deg roll gives L camber 2.8 R 2.4, roll c 95. 2 deg roll gives L 3 R 2.1, roll c 95. 3 deg roll gives L 3.3 R 1.8, roll c 96. 4 deg roll gives 3.4 R 1.5, roll c 98. 5 deg roll gives L 3.5 R 1.1, roll c 95. Camber is excessive for a rear suspension, will start of with around 1.5 negative for the next version.

The roll centre is the green O, the instantaneous roll centres pink O. What do you think?


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PostPosted: Mon Feb 13, 2017 12:52 pm 
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Simulator is my new toy :) How does a roll centre at static of 211mm sound? It reduces in roll to 186 at 5 degrees, am going to have to make a decision on that, too much jacking effect? The rest is excellent, from a static -1.5 degrees camber it moves progressively to -2.9 degrees for the outside wheel at 5 degrees roll, the inside changes from -1.5 progressively to -1.0 which I like very much. Plus the roll centre and instant roll centres don't move around a lot, some lateral movement and that's it.

So, roll centre height, hmmm.

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