Rear Engine Suspension

[wracing 19]

This may be an epic post as i have a few questions that cant really be split up.

 

Currently im building a 205 with a twincharged engine. after a couple of simulations and strength tests on the 205 monocoque I soon realised that it wasn’t going to cope with any real power without adding massive amounts of roll cage, strut bracing, seam welding....

 

as a fast well balanced car is not about power its power to weight....what is the solution to meet this criteria.......a space frame.

 

Currently the tunnel has been designed and fabricated leaving the suspension geometry and 'sub frames' to design.

 

Static on the front:

 

STATIC VALUES

Camber Angle (deg): 0.00

Toe Angle {Plane} (deg): 0.00

Toe Angle {SAE} (deg): 0.00

Castor Angle (deg): 1.41

Castor Trail (hub) (mm): -0.42

Castor Offset (grnd) (mm): 5.96

Kingpin Angle (deg): 6.50

Kingpin Offset (w/c) (mm): 39.78

Kingpin Offset (grnd) (mm): 14.15

Mechanical Trail (grnd) (mm): 5.96

ROLL CENTRE HEIGHT (mm): -32.52

 

GENERAL DATA VALUES

TYRE ROLLING RADIUS (mm): 225.00

WHEELBASE (mm): 2420.00

C OF G HEIGHT (mm): 250.00

BREAKING ON FRONT AXLE (%): 60.00

DRIVE ON FRONT AXLE (%): 0.00

WEIGHT ON FRONT AXLE (%): 35.00

OUTBOARD FRONT BRAKES:

OUTBOARD REAR BRAKES:

INDEPENDENT FRONT SUSPENSION:

INDEPENDENT REAR SUSPENSION:

RACK TYPE STEERING ARTICULATION:

 

These values subject to change

 

 

Static on the rear

 

STATIC VALUES

Camber Angle (deg): 0.00

Toe Angle {Plane} (deg): 0.00

Toe Angle {SAE} (deg): 0.00

Castor Angle (deg): 0.11

Castor Trail (hub) (mm): -0.26

Castor Offset (grnd) (mm): 0.69

Kingpin Angle (deg): 6.03

Kingpin Offset (w/c) (mm): 39.71

Kingpin Offset (grnd) (mm): 15.93

Mechanical Trail (grnd) (mm): 0.69

ROLL CENTRE HEIGHT (mm): -4.12

 

GENERAL DATA VALUES

TYRE ROLLING RADIUS (mm): 225.00

WHEELBASE (mm): 2420.00

C OF G HEIGHT (mm): 250.00

BREAKING ON FRONT AXLE (%): 60.00

DRIVE ON FRONT AXLE (%): 0.00

WEIGHT ON FRONT AXLE (%): 35.00

OUTBOARD FRONT BRAKES:

OUTBOARD REAR BRAKES:

INDEPENDENT FRONT SUSPENSION:

INDEPENDENT REAR SUSPENSION:

 

These values subject to change

 

 

Front suspension is a double wishbone setup with a rocker to coil over.

 

 

INCREMENTAL GEOMETRY VALUES

 

Bump Camber Toe Castor Kingpin Damper1 Spring1

Travel Angle Angle Angle Angle Ratio Ratio

(mm) (deg) {SAE} (deg) (deg) (-) (-)

(deg)

 

60.00 -0.4005 -0.1188 1.5865 6.8954 2.693 2.693

40.00 -0.2242 -0.0700 1.5273 6.7204 2.405 2.405

20.00 -0.0911 -0.0310 1.4683 6.5881 2.248 2.248

0.00 0.0000 0.0000 1.4093 6.4977 2.159 2.159

-20.00 0.0495 0.0247 1.3504 6.4486 2.110 2.110

-40.00 0.0573 0.0445 1.2915 6.4411 2.086 2.086

-60.00 0.0228 0.0610 1.2327 6.4758 2.076 2.076

 

 

INCREMENTAL SUSPENSION PARAMETER VALUES

 

Bump Anti Anti Roll Roll Half Wheelbase Damper1 Spring1

Travel Dive Squat Centre Centre Track Change Travel Travel

(mm) (%) (%)Height {toHeight {to Change (mm) (mm) (mm)

Body} (mm)Grnd} (mm) (mm)

 

60.00 13.15 0.00 -45.54 -105.54 -5.54 0.39 -25.62 -25.62

40.00 11.82 0.00 -41.23 -81.23 -3.04 0.25 -17.72 -17.72

20.00 10.73 0.00 -36.89 -56.89 -1.19 0.12 -9.10 -9.10

0.00 9.83 0.00 -32.52 -32.52 0.00 0.00 0.00 0.00

-20.00 9.07 0.00 -28.13 -8.13 0.54 -0.12 9.38 9.38

-40.00 8.43 0.00 -23.69 16.31 0.43 -0.23 18.92 18.92

-60.00 7.88 0.00 -19.22 40.78 -0.33 -0.35 28.54 28.54

 

Would you think the current set up is stable enough?? or should I try and stabilise the values and remove all parabolas??

 

Rear suspension is a double wishbone setup coil over to lower.

 

 

INCREMENTAL GEOMETRY VALUES

 

Bump Camber Toe Castor Kingpin Damper1 Spring1

Travel Angle Angle Angle Angle Ratio Ratio

(mm) (deg) {SAE} (deg) (deg) (-) (-)

(deg)

 

60.00 -0.5667 -0.0621 0.1399 6.5981 2.058 1.735

40.00 -0.2470 -0.0714 0.1295 6.2784 2.146 1.814

20.00 -0.0608 -0.0541 0.1188 6.0922 2.233 1.891

0.00 0.0000 0.0000 0.1081 6.0315 2.318 1.966

-20.00 -0.0652 0.1016 0.0972 6.0969 2.402 2.040

-40.00 -0.2663 0.2639 0.0862 6.2983 2.484 2.112

-60.00 -0.6261 0.5058 0.0749 6.6586 2.563 2.182

 

 

INCREMENTAL SUSPENSION PARAMETER VALUES

 

Bump Anti Anti Roll Roll Half Wheelbase Damper1 Spring1

Travel Dive Squat Centre Centre Track Change Travel Travel

(mm) (%) (%)Height {toHeight {to Change (mm) (mm) (mm)

Body} (mm)Grnd} (mm) (mm)

 

60.00 3.46 11.72 -83.92 -143.92 -5.95 0.47 -27.44 -32.45

40.00 3.00 9.82 -57.32 -97.32 -2.71 0.29 -17.92 -21.17

20.00 2.56 7.85 -30.74 -50.74 -0.73 0.14 -8.79 -10.37

0.00 2.13 5.85 -4.12 -4.12 0.00 0.00 0.00 0.00

-20.00 1.71 3.80 22.62 42.62 -0.51 -0.10 8.47 9.98

-40.00 1.27 1.58 49.56 89.56 -2.28 -0.16 16.66 19.62

-60.00 0.79 -0.96 76.71 136.71 -5.31 -0.15 24.59 28.93

 

im not quite happy with the rear is anti squat high enough??

Are the values stable enough??

 

All outboard joints will be rod ends and compliant bushes

All inboard joints will be rose joints. to allow adjustment

 

Any advice would be great

 

Thanks in advance

 

James

[GLPoomobile 958]

Any advice would be great

 

Thanks in advance

 

James

 

I advice clincial evaluation. You are either certifiably insane, or a kid genius!

[taylorspug 7]

All those figures, and you have mis-spelled suspension in the title!

Edited July 8, 2009 by taylorspug

[Batfink 201]

this is technically way more advanced than most projects on the forum. Interesting stuff but in the end you will probably just have to build it and see

Are you keeping the trackwidth the same front and rear?

Edited July 8, 2009 by Batfink

[Cameron 16]

Maybe if you arranged the data so it was almost legible..

[wracing 19]

sorry about the spelling i posted half asleep, i feel like an arse! could a admin edit please......

 

track is increased by 60mm a side on the front and 80mm a side on the rear

 

i know thats what im dreading, i think i should use rose joints all over as then i can edit almost every value.

 

i want every value to be as stable as possible throughout deflection allowing a well rounded car.

 

james

[welshpug 1,655]

Ask Rippthrough!

[bales 1]

You copied and pasted by the look of it all the values from Susprog (at least it looks like susprog from the screenshot)

 

I don't get why you are doing this, I can't work out whether you are trying to appear very clever or whether you genuinley think someone on here who has an initmate knowledge of susprog (or whatever suspension dynamics program it was) is going to be able to look through a list of numbers and actually work out anything from them??

 

They aren't presented in any sort of readable manner and they mean absolutely nothing to 99.9% of the population.

 

I have used this software (or very similar) and unless we know what numbers you put in then it is useless to try and ask someone what they think??

 

Build it, test it, adjust it.

 

If you have built lots of race cars then you should know this is how it works.

[pugpete1108 62 1 Cars]

I advice clincial evaluation. You are either certifiably insane, or a kid genius!

 

i'd go for the latter.....actually saying that

[Rippthrough 98]

i want every value to be as stable as possible throughout deflection allowing a well rounded car.

 

james

 

 

I'd question that, look at the rear toe curve on an Elise....

[wracing 19]

rippthrough could you expand on that, i couldn't find much information on the elise, i may be looking in the wrong place. thanks

 

the software im using is a lesoft application. i've designed the suspension system then the detail above are a copy of a report for that system.

 

bales the post is merely a copy of an email i posted for possible education purposes and if anyone else had any input. there is plenty of information with out divulging my pick up points which i don't want to do. ive had a response to my email and have a few changes to do to the anti squat and we are going to try remove the parabola from front toe.

 

the reason im spending time developing my ideas theoretically is to hopefully reduce costs and 'time to market' im not a bottomless pit.

 

pete hows the megasquirt going if you get stuck ill try and get down in the near future!

 

thanks

 

james

[wracing 19]

this is the overall layout of the car. im going to shorten the front wishbones to reduce manufacuring costs as they didnt fair well under fea.

 

 

james

[gti-si 0]

You make me jealous James. I'm only just getting to grasp Solidworks now, I've been trying to use it over the past month or so...I'm doing mech eng so I'll be using it alot next year. Cracked a simple FEA last night though on a piston/rod I designed in COSMOS, really interesting stuff

 

Just wanted to say though, great seeing some of this stuff being used, was looking at your turbo manifolds and the design work you did for that, damned good stuff.

 

Good luck with the project, wouldn't mind seeing more of the design work as you go on

[bales 1]

bales the post is merely a copy of an email i posted for possible education purposes and if anyone else had any input. there is plenty of information with out divulging my pick up points which i don't want to do. ive had a response to my email and have a few changes to do to the anti squat and we are going to try remove the parabola from front toe.

 

This is a genuine question and not a dig but why would you not want to divulge your pickup points?? I'm lost what information they contain that people can do things with....are they not just x,y,z components in relation to a datum on the chassis??

 

Are you thinking of making a rear engine conversion kit or something and don't want people to steal your design?

[Cameron 16]

It encourages laziness I guess.. There's only so much information you can give for free, the stuff that takes real effort to find out is worth hanging on to.

[wracing 19]

about 2 years ago I designed and published a network protocol for distributed industrial control, I didn’t patent the idea, even though I have intellectual property rights on certain aspects, an unnamed company is now producing units with my design and returning a tidy profit as Allen Bradley, Mitsubishi, modcon haven’t caught up yet. So essentially im not sitting on a tidy sum because of some over zealous posting. Lesson learnt

 

I don’t want to make the same mistake it may seam pathetic as it’s just an idea but you never know!

 

Once I’ve built mine, the drawing will be available I doubt anyone will want them though.

 

thanks gti-si one bit of advice make parts as simple as possible and mate them together as assemblies, many people try and put to much detail into one part. For the tea results and cad drawings ill post them in my build thread it’s on here somewhere...