Double A-arm suspension

[volkdent]

Pure55, what's the latest?

Jason

[pure55vw]

Progress has been disappointingly slow due to other commitments, but so far: The suspension has been on the car about 3 months (car is an otherwise bone-stock '74 beetle). Subjectively, the ride is better, but needs some tuning with the adjustable front and rear shocks it has. Steering is very light (almost too light), which causes it to "dart" slightly with any bit of steering input. May need more caster (has 3 degrees now). Still looking at roll angles and intial turn-in feel of the steering, and I'm considering a stiffer anti-roll bar although I can't do too much with the skinny stock tires. Nothing seems to be wearing out too fast, but I'm still planning to replace the urethane a-arm pivots with OEM-style rubber bushes. I promise to post later with more info as it comes in and those always-popular pictures!

Jay

[volkdent]

I'm glad to hear its still on the go. How come stock rubber bushings vs PU? I made some serious progress tonight. I bolted on the complete suspension chassis mockup(wood) and it fit like a charm. One snafu though, it looks like I may have to raise my ride height a bit so the input shaft for the steering rack will be able to make a decent angle with the stock steering shaft. We'll see.

Jason

[Vincent]

you could always use a steering knuckel like in some modern cars to fit the angle. I rember when we put a new front end in my grandfathers 1959 International truck we had the same problem and just put in one of the universial joints to make the angle worked pretty slick.

[volkdent]

Universal joints don't work at severe angles, which is the situation I'm in now. I'm planning on using 2 high angle joints, but at this point I think the angle may be too much. The input shaft is inboard quite a bit, as well as being very high, almost the same level as the stock steering shaft. So, we're talking about an abrupt 90 degree turn, no universal joints can handle that!!

Jason

[volkdent]

I recieved a MkII non-powered rack universal joint today, so I can hack off one end and see what its max limit for angulation are. I did some more brainstorming, and I figure that if I put the second UV joint up inside the tube the steering shaft is in, it will give me some more room to work with and shouldn't effect much of anything.

Jason

[pure55vw]

Jason, going to try rubber bushings for the same reasons the OEM's do: less maintenance, less suspension friction (good in a light weight car like this), and less cost! Since my lower A-arm pivot doesn't have to "twist", I can use a stiffer bushing to keep the radial stiffness high (though not as much as PU). I've done the "wooden mockup" thing too, so I know what that's like! I solved the steering U-joint problem with wide spaced A-arms allowing the rack to sit closer and further forward on the pan. The tie rods are at a slight angle in the top view, but not bad. Since T-III knuckle steering arms are bolt-on, they're easily changed or shifted to adjust the Ackerman. With the second ujoint inside the steering tube, you'll need to put another through hole in the firewall, something I also considered

[volkdent]

Actually, it looks as though I'll be OK with the steering tube just trimmed down till it is just meets the rubber grommet in the bulkhead. I've had a Teflon bushing made to reside inside the steering tube, and I've ordered a Flaming River 5/8" - 5/8" U joint. Here's a peak at what I've come up with thus far. This was designed by Bob Frost-Stevenson at Rorty Design in Melbourne AU.

Suspension View

[volkdent]

Its not all in yet, but I found that with a 20deg. roll of the rack, I could get a decent angle to the output shaft. I've cut down the stock steering shaft now, and pressed in the Teflon bushing and all is good. STILL waiting for the Flaming River U joint, they must be slow on the draw right now. Bob wanted to machine down the rack to allow it to be rotated at any angle, but then I'd have to have a clamp machined and then it would also be a solid mount, more noise. I have PU bushings for the rack now, and I may switch to rubber in the future if the road feel is too much.

The design is finished, so just waiting on parts before fabrication begins!

Jason

[pure55vw]

Just a consideration: are you hard-mounting the bottom end of the steering tube to the body? As you know, stock form uses just the rubber grommet isolator between the tube and firewall. I originally tried a metallic bushing in the steering tube to support the bottom of the shaft, but found that steering reaction forces working against the grommet kept causing it to back out of the firewall hole, in turn causing the shaft to become loose. I built a seperate lower bearing support that attaches to the suspension subframe, so the bottom half of the tube no longer has to support the shaft (like stock).

[volkdent]

Apparently you just saved me a lot of time. I was planning on using the stock grommet, but as of today, I've realized I have issues with the U-joint that will push it through the firewall anyway. So, I'll be making a bracket too, but on the inside of the firewall. Do you have any pics of your steering setup?

Jason

[volkdent]

Well, it turns out that the whole upper U joint is going to have to reside on the INSIDE of the bulkhead. I'll have to shorten the steering column some more, then have a clamping bracket made that holds the lower end of the steering column. The Teflon bushing will sit inside that, then the upper U joint, then the intermediate shaft through the bulkhead, then the stock U joint attached to the input shaft of the rack. The angles are tight, but it looks like its going to work, so I have one less thing on my todo list.

Jason

[volkdent]

The shafts and U joints are at the gear cutter as we speak to be splined. I have a pair of QA1 Proma Star 11 1/4" shocks sitting here, and I have someone working on another balljoint option. So, nothing too concrete, but getting warmer!

Jason

[volkdent]

Pure55, can you take some pics of your steering linkage as it attaches to the steering shaft? Thanks,

Jason

[lazylongboarder]

WOW, I got to this a little late, but this setup is incredible Pure55! As is yours Volkdent.

I have access to a cnc plasma cutter and a few other play toys, Would it be possible for a set of plans to go up for sale? I'm interested in the setups, but it'll be a little harder to get all the money at once. This'll make things a little easier on the checkbook. This would also be easier to ship to my address (email). You name the price.

I love your ideas guys! I like the idea that i can upgrade to a higher end shock because it is a more common performance application. If only Ohlins shocks weren't $3010 each.

Let me know the price.

Thanks a lot,
Russ

I would rather use your guys ideas and pay you, but I'm pondering the idea of a 996 macphereson strut front setup. I'm sold on the Multi-link 993 rear setup. All one clip, just have to worry about the angles of the strut towers.