What is your interest in having a bolt-on A-Arm front suspension???

[GS guy]

That Volksworld suspension looks interesting Jason - but would appear to have very poor (short!) virtual swingarm lengths and excessive RC movement? I wonder how much additional bump movement those ball joints have left!
Definitely looks like a "hot rod" & cruiser set-up, not really for any kind of performance application. It's purdy though!

I'm finally getting the design finalized for my fiberglass buggy A-arm front suspension - using MII spindles and Chassisworks A-arms. I did spend hours and hours on the computer re-working the inner pick-up points to optimize the geometry, the "design" aspect definitely something one shouldn't take lightly! Talk about variations on variations!
I'm winding up with a RC about 2" or so above ground, with minimal RC movement in roll, and not too bad in bump and roll. I'm making my upper pick-up points fairly adjustable for camber, caster and RC changes - if necessary.

When I finally get something in real hardware I'll put up a few pics. Not really applicable to a VW front end though - but maybe food for though if you want to go fully custom forward of the firewall?
Jeff

[Shadowbug]

Originally Posted by GS guy

one shouldn't take lightly! Talk about variations on variations!
I'm winding up with a RC about 2" or so above ground, with minimal RC movement in roll, and not too bad in bump and roll.

thats the devil in the details, a nonequal nonparalell a-arm suspension by design is a racecar suspension, performs well in bump, and also in roll, but in a bump/roll (both at the same time) not so well. so you can compromise and have a roll center that moves more thanit should in bump or roll, but moves less in a combined bump/roll

in a dune buggy, if its an offroad machine, this shouldn't be too bad since suspension movement is for the sake of articulation, not handling. but street machine, you can offset this with a big antiroll bar (what I will be doing on my lotus) front and rear.

perhaps its possible to build a perfect suspension, but we don't have the budget. so even F1 suspensions are all about compromise.

OH ya one more thing. If you want to bag your ride for adjusting your ride height, go with a equal length paralel A-arm setup, otherwise you'll have horrible handling at any height.

[GS guy]

Mine's definitely a street (and maybe sometimes track) "buggy" Shadow. It'll look more like a Can-Am race car under the skin - tube chassis and mid-engine. Anti-roll bars and wide low-profile tires are definitely part of the equation.

One interesting thing I discovered while going through the multitudes of geometry variations, as the (static) RC was moved up the bump+roll dynamic RC movement became less and less - to the point of essentially no RC movement at all - but with a RC height at 6-7" or higher! Everything I've read suggests keeping the RC closer to ground, generally 1-3" high or so, so that's where I put it. But watching the dynamics of RC movement in all the different variations sure was interesting - and informative. One thing I definitely learned - if you're going to design your own layout having a computer program to model it on is pretty much a must-have tool.

Jeff

[Shadowbug]

I ususlly rough model mine in autocad, then refine with an suspension program. and abolutly you need a suspension program, you can do in 5 minutes what would take 3 hours to do in autocad, and do it more accuratly

considering it all comes down to 1/8" to get optimal geometry

[The Pirate]

Which suspension programs are you 2 using? I have modeled my single A arm against the stock I arm and they seem to preform the same in Front Suspension Geometry Pro. This is due to the fact that the A arm is the exact same length as the I arm. However I would like to double check against another program.

Thanks.

[GS guy]

I use Performance Trends - Roll Center Calculator. It's not their full blown Suspension analyzer software, but a lot less expensive and does 95% of what I need it to do.
http://www.performancetrends.com/

I sarted modeling mine on paper - scale drawings. That was an interesting exercise for a "first cut", but quickly became apparent that method was going to be too time consuming and tedious to give me the information I needed. The PT software really opened my eyes in seeing how small changes affect the geometry. You quickly realize that trying to "wing it" when laying out a suspension design could yield less than desirable results!

Jeff

[Shadowbug]

I do most of my modeling in Autocad, then fine tuning using the performance trends software.