Lift-Throttle Oversteer, rear sway bar, Front spring shackle

[oldopelguy]

One option I was seriously considering is a roller vice a slider or shackle. To explain, imagine the poly suspension bushing, basicly a cylinder with a pair of flanges on the ends, like a spool. If a suitable pair of "ears" were welded in hanging down from the front and back of the bottom of the lower a-arm, and the spool mounted between them, then the spring could roll across the top.

The flanges on the spool of material would have to be big enough to center the leaves front to back, the center of the spring would need to be fixed, the eyes would probably need to be cut off the ends of the springs, and what material would you use? On the other hand, if you had a few holes on each arm you could move the spool in or out to change spring rate (well sort of, longer/shorter lever?), you could use bearings to make sure it all spun freely, and your spool size and positioning could set any ride height you wanted. Hey, food for thought?

[RallyBob]

One option I was seriously considering is a roller vice a slider or shackle. To explain, imagine the poly suspension bushing, basicly a cylinder with a pair of flanges on the ends, like a spool. If a suitable pair of "ears" were welded in hanging down from the front and back of the bottom of the lower a-arm, and the spool mounted between them, then the spring could roll across the top.

The flanges on the spool of material would have to be big enough to center the leaves front to back, the center of the spring would need to be fixed, the eyes would probably need to be cut off the ends of the springs, and what material would you use? On the other hand, if you had a few holes on each arm you could move the spool in or out to change spring rate (well sort of, longer/shorter lever?), you could use bearings to make sure it all spun freely, and your spool size and positioning could set any ride height you wanted. Hey, food for thought?

Stephen, I modified my Kadett front end by cutting off the eyelets and using a steel plate (bolted into lower a-arm) with a removeable 1/2" thick piece of HDPE rubbing against the ends of the spring leafs. I'll try to get out to the barn and take some pics of it, but the front end is covered with dust from sitting around for 8 years, so it's a bit filthy. Similar yet different from what you are suggesting.

[jeff denton]

Hey, I like that idea, Bob. The spacer block could be adjustable to vary crossweight and left bias.
As for drilling the center of the springs, what would be wrong with drilling the crossmember and running the centering bolt through it, too? I notice my spring leaves will "walk" to the left, have to check and adjust them occasionally or my wheel weights get weird. Need to do something about this... Had thought about glueing them together in the middle, too...

[Tru-Craft]

Jeff your right, the shackles will be the best & easiest way. I measured everything and came up with a distance of 1.82" between the shackle holes. This is the smallest drop posible with clearance. I'm going to CNC machine the side part from one piece of 1/2 x 1-1/4 x 3.09 stock. Like Bob said the radius is important for proper lower A-arm clearance.
I was thinking of using a thick wall steel tube between the side parts on the top pivot holes, then no welding is required at all.
Jeff your shackles are simpler? How are yours made???

Simpler is cheaper! If someone decides to produce shackles for sale, we should combine the best features of all designs.
Lyle

[jeff denton]

They are just simple 1/8" x 1-1/4 straps, two inners and two outers per side.
They bend a bit to fit around the spring eye. The left side shackles are longer than the right ones in my application. They attach to the A-arm with two 3/8 x 1-1/2 bolts, the holes on the A-arm are beefed up by welding hardwashers on each side. Too simple. Maybe not real durable for lots of road miles, but perfect for what I do.... There's nothing really to sell, it's just few bits of scrap and some grade 8 fasteners...
I like your idea of the hard spring eye bushings, I would then use a bigger bolt through the bottom of the shackles and spring eye. The 3/8 bolt I presently use here doesn't look like enough, especially on the right side where we compress the spring pretty hard in a left turn...

[Tru-Craft]

Left side shackle longer, sounds like your running short track ovals! Having an Opel is unique enough but racing one has to be real rare. I race Enduro Go-Karts for a hobby (WKA) no suspension!!!!!!
I've had Opel's since 1978, before the internet it was a lonely hobby.
This site is great! Should have joined sooner.
True with shackles the spring could shift, a bolt or pin through the spring and cross- member is a good idea for racing loads.

[RallyBob]

I notice my spring leaves will "walk" to the left, have to check and adjust them occasionally or my wheel weights get weird.

True with shackles the spring could shift, a bolt or pin through the spring and cross- member is a good idea for racing loads

You're both quite right about the possibility for the spring to shift. When I take pics of my Kadett front suspension I'll show what I did to prevent this. Basically I bolted the spring pack together in the middle, and slotted the leaves vertically front and rear...then I welded vertical tabs of steel into the void of the crossmember. So the spring center can move up and down, but the tabs 'n' slots keep it located side-to-side. Hard to convey with words, I know.

Bob

[Tru-Craft]

I just finished my (Bob designed) CNC shackles, turned out good. The one piece sides are made from 1/2 stock. I'm going to weld in a cross bar like Bob, I think it's the best way.
By changing the step radius (CAD is great!) I was able to decrease the hole spacing to 1.80" a little less drop in the front, the holes will line up perfect and the side parts are probably stronger than welding.
So I redesigned the wheel and ended up with a more expensive set of Bob's Shackles!!!
Oh well, I made them myself!
I have a CNC program to make more!

Bob, should I worry about the spring shifting on a street GT?
Thanks for a good design.
Lyle

[RallyBob]

Guys, this is how I centered the leaf spring bundle. I removed the strap securing the center of the spring pack together. Then I drilled for two countersunk-head bolts from the top, using a carbide drill bit and countersink. A cutoff wheel on a 4.5" angle grinder cut the slots in the spring, and the steel guide plates were simply welded into the center of the crossmember.

Another pic of the upper control arm camber adjustment I utilized, and the grease fittings I fit to urethane bushings to prevent sqeaking and binding.

At the lower a-arm you can see the eyelet cut off the spring end, and the teflon liners added between each leaf to smooth the spring action and eliminate noise. Unfortunately, I could not find the actual support blocks with the HDPE friction material. The four mounting holes in the a-arm are apparent however. Gotta find where I left them....

Oh yea, when you lower your GT or Kadett, either cut the bump stops in half, or use some aftermarket shorter ones. These are polyurethane stops from Energy suspension which fit the bill just right.

[Tru-Craft]

Hey you're clever!
That's right will have to cut the bump stops.
The camber will probably need to be adjusted once the shackles are installed, and then I will have to lower the back! One thing leads to another!!!!

The camber adjuster you made is great for racing.....simple design! Now you know why I race Go-Karts, no suspension to adjust!

The spring bolts and plate is a real strong design, your not relying just on the bolts for lateral loads.
Do you think my non-racing GT can get by with a single hole through the spring, like Jeff asked? Should I care if it shifts a little?

You and Jeff must be the Opel racing guys!
It's got to be hard racing a rare car like the Opel. You don't have the huge resources of say a Miata!
You guys still racing?
Like they say if you want to win, copy the fast guys!
Copy-cat

[jeff denton]

Actually there are quite a few Opels on racetracks around the world, some of them are right here at gt.com! Two in Oregon are track champs.
The way my car is built, body parts all pop off in a jiffy, can be hammered back into roughly the shape of a GT and then rivet back on. The chassis itself is so strong I don't even worry about it.
You'd be surprised at how many suspension parts are available new or used, quite often homemade works best for me. Whenever you need something this website is the best place to start, there is great help here.
The GT front suspension is a bear to tune, but the rear is real easy once you make the control rods and panhard bar adjustable lengthwise. The torque tube setup limits how much rear steer and roll oversteer you can set up, but I find that I don't need much of either, really depends on track conditions from week to week!
Rally Bob would be the expert here, he's had his fingers into lots of different kinds of racing Opels and knows them better than anyone. When he talks, I listen. There is a lot to be learned! Notice that it takes a lot of homespun ingenuity to do this, in stock form the cars leave a lot to be desired in terms of handling and horsepower... For instance I wish I had seen Bob's non-sliding spring a year ago... I have one side of my car apart this moment to get the leafs lined up right for Saturday's race.

[rockytopmark]

Does the use of Shackles require the spring to be notched, for the purpose of keeping it 'centered?'

[jeff denton]

My recent experience, just since I added a shackle to the right side (left has had a shackle all year) tells me the answer is YES, kind of... In my situation, the spring leafs will shift. But keep in mind that I drive my GT a bit differently than most people do!
All I've learned from Bob's posts yesterday were on my mind today while winterizing boats, by about 3 pm I decided I had to secure my springs. Tonight. Last race is tomorrow night, I really want to do well!
Phone call to my machine shop buddy, he says use a "cobalt drill bit", have the spring leafs all clamped together, have the spring cold, close to freezing is good, use a good cutting oil, and go for it. Slowly.
So a phone call to Lasalle Tool, sure we have a 5/16 Cobalt bit, just $8.95...
Got the bit ran home and yanked the spring pack out in just over half an hour (practice makes almost perfect). It hasn't been very warm out, the spring couldn't have been much over forty degrees. I got the leafs all centered up and hose clamped together and fired up the drill press. I use a real nasty smelly cutting oil from a spray can, "BD" brand, good stuff!
Now would you believe, the hole was drilled through five spring leafs in less than one minute? I was shocked. It was no harder to drill than plastic, I swear!! Now I know.
Next step, put it back in the crossmember, a 5/16 x 3" bolt will go up through the center hole already in said member. This spring will stay put now. OR, do I really need to do the notches and guide plates like Bob did? We'll see.
Gotta go. It takes me about an hour to get the spring back in usually. Not a real fun job, kinda scary too...

[RallyBob]

Next step, put it back in the crossmember, a 5/16 x 3" bolt will go up through the center hole already in said member. This spring will stay put now. OR, do I really need to do the notches and guide plates like Bob did?

Jeff, the center of the spring moves up and down a bit through the spring's travel. So if you use a long bolt through the center hole it *might* catch the threads of the bolt on the crossmember hole. What if you found a short piece of tubing just bigger than the bolt and welded it in the hole in the crossmember, it would kinda act as a valve guide to allow for smooth vertical movement as well as lateral location. More than one way to skin a cat...

[opelwasp]

Lyle what wpuld you charge to whip up a set and mail them to Nor Cali?

[Tru-Craft]

Jeff, glad you drilled your spring. Now we can find out if it will hold up under racing loads. If it does, my street GT will surely work!

Here is some useless info, un-heat treated high carbon tool steel is about (35 Rc.) Spring steel is about (45Rc ) and fully hardened steel about ( 65Rc ). A regular HSS drill is about (65Rc ). So a drill can easily drill spring steel, if speed and feed is correct. A cobalt drill is a little harder than HSS. Carbide can drill HSS. Diamond can .....

Make sure you use a grade 8 bolt with as long a shoulder as you can, remember a 5/16 - 18 bolt is only 1/4 diameter at the root of the thread!
Let me know how it works and good luck with the race.
Lyle

[Tru-Craft]

Chris, I'm not sure if they will work yet. The 1.8 hole distance has to be checked for clearance. I'm going to try and install them this weekend.
I own my own machine shop, I make mostly medical and areospace components. I do no flight hardware or things that go in the body! Liability!!!!!!!!
Brake parts! suspension parts!

If I did make shackles for others I would probably sell them as a kit. The (4) one piece sides and (2) cross bars. Welding of the 2 crossbars to be completed by the customer.
Or maybe I could sell them as a cool CNC machined paper weight!!!
The shackles are really nice, all CNC machined with fillets and I even machined a .25 slot to line up the cross bar for welding! Everthing is machined not sawed!
If I got a few orders probably about $75 a set, not welded.
Lyle

[Tru-Craft]

Bob, I thought Jeff was going to bolt the spring solid to the cross member?

[jeff denton]

I did. It's done. I think I understand what Bob is saying, we'll play with it some more this winter. For one more race I think my way will be better than what it was! Keep in mind, the way I drive my car is kind of bizarre, it only turns left, the right front tire is taking half the weight of the car most of the time. We have no bumps, no jumps on our track. No tire ever leaves the ground, although the left tires really don't do much. The right front spring is so stiff that, at ride height, there is no rebound available, it is all "maxed up".
It would be insane to try to turn it right at any speed...
All I have to do is make one lap of the Main Event Saturday night and I am Rookie Of The Year. Incredible. I really didn't intend to take it so seriously, it's just that my car did better from the git-go than I had dreamed possible, and it kind of went that way every race. Even got to park it in the checkered "Winner's Circle" a couple times. I think I worked on it less than most of my competitors did theirs, but I built it very slowly and painstakingly, it wasn't a "thrown together" race car like so many are. No corners were cut, no expense cheapened. Every decision was "re-thunk" until it looked right. That's how I like to do things, given the time and the money...
One thing is for sure, now thousands of Montanans know what an Opel is!!