Franz Estereicher on Early Corvette Suspensions

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Scott [00:00:07] Welcome to the EATON Detroit Spring podcast, the podcast bringing you suspension expertise for your classic restoration, resto-mod, custom designs, and way more. Mike, want to introduce our guest for us?

Mike [00:00:21] We got a great guest here today for your listening enjoyment. We have Mr. Franz Estereicher and when it comes to knowing about rear suspensions on the early Corvettes, Franz just may be the most knowledgeable person on the face of the earth. And today we’re here to hear why. OK.

By early Corvettes we’re referring to the C1-C2 and beginning of the C-3 cars. Franz and us go back many many years. We were talking before we went on the air and we figure our relationship probably goes back a good, God, 30-35 years minimum? At least.

And today we’re going to guarantee that some of you will not agree with what you’re going to hear today but arguing about Corvette suspensions with Franz is like telling your doctor he’s treating you wrong. So to get the ball rolling why don’t we give our listeners, why don’t you give some of our listeners some of your background Franz?

Franz [00:01:17] I’ll be happy to.

Mike [00:01:17] Tell us where it all started.

Franz [00:01:19] Started many years ago 1966. I’m one of the founding fathers of the Downriver Corvette Club. And from that day on always been involved with Corvettes either as a supplier… First of all as a wanna be race driver, Corvette enthusiast, and later in life as a Corvette supplier.

And we supply leaf springs, coil springs, and stabilizer bars to what was commonly referred to at Chevrolet at that time for the wide car that we all know as a Corvette.

Mike [00:01:47] Now when you say we, who were we?

Franz [00:01:51] Actually Ontario Steel Products. And they were acquired by North American Rockwell in the late 60s.

Mike [00:01:56] So you made the Corvette springs at Rockwell for Corvette.

Franz [00:02:00] We made them for Corvette. Eaton Corporation, which was a stone’s throw away from our plant in Chatham Ontario.

Mike [00:02:07] Not the same Eaton we are.

Franz [00:02:09] No, no.

Mike [00:02:10] Totally different company.

Franz [00:02:10] Completely, completely different.

Mike [00:02:12] They’re the little guys.

Franz [00:02:13] Yeah they’re they’re the little ones on the block.

Mike [00:02:15] Yeah.

Franz [00:02:15] But they were a supplier of leaf springs to the Corvette platform along with several other leaf spring manufacturers, Detroit Steel Products, DSP, made their spring down in Toledo.

We all, all looked at the GM business as a whole. And then everybody had their own little specialty. In our plant there in Chatham Ontario, which incidentally we had two: one did leaf springs the other one did call torsion bars and stabilizer parts. In our early spring plant we had a low volume line which really fit into the Corvette when it looks at production volumes. Normally leaf springs you like to get, fifty thousand to one hundred thousand springs, and the Corvette as we all know only has a transverse spring, and one per vehicle.

End up being 20-some thousand springs a year which was very very low volume.

Franz [00:03:04] So even though parts may have been sourced in one of the other companies, in most instances Rockwell or Ontario Steel Products did the manufacturing. Just because of the line, the way we had it set up. It takes so several hours for us to set up to do a low volume line. But when you go to set up a high volume production line, it takes you in some instances a week or so.

Mike [00:03:26] Now what exactly was your role?

Franz [00:03:29] Well I I left General Motors, Detroit Diesel division in 68.

I went to work for North American Rockwell as a suspension designer and my responsibility was designing leaf springs, coil springs, stabilizer bars, and torsion bars for our OEM customers. And the OEM industry at that time basically was four companies, three big ones and a little one.

Ford, Chrysler, GM, and American Motors. And we supplied all four products to each of those companies, whether it was the passenger car or light truck. And I design primarily leaf springs. That was my focus.

Mike [00:04:07] Now you say you were involved in the C1 and the C2. Of course those were before 1968. So tell us how you were involved in those ones.

Franz [00:04:16] Whenever you got the leaf spring business, leaf springs were unique in a sense that if you were sourced the production business, you were responsible for all service prior to that point. So Rockwell was involved with supplying a Corvette aftermarket through GMPD General Motors Parts Division, and going back to the 1952 version of the Corvette which was the mule car.

Mike [00:04:39] *table rumbling* That was me. I got carried away with excitment.

Scott [00:04:44] The whole podcast table was shaking with excitement.

Franz [00:04:49] So what we did at that point, is the 68 version of the spring was essentially the same as the 63 to 67 spring. And we were supplying a number of those up until late when they went from the two and a quarter inch wide spring to the two and a half inch wide.

Mike [00:05:11] That was the early 80s, late 70s.

Franz [00:05:13] In that time frame yeah. We supplied… At that point we supplied a hundred percent of everything.

Mike [00:05:17] It was actually an overlap for a year or so.

Franz [00:05:19] Yeah yeah yeah yeah yeah. And then the other thing is General Motors had their own leaf spring plant, it was called Livonia Spring And Bumper. And in the early years, Livonia did a lot of the R and D for the C1 Corvette, and particularly in the racing program. It’s very obvious if you read the work orders, they talk specifically about Livonia’s involvement, which was rather significant.

Mike [00:05:46] We get a heck of a lot of questions about Corvette springs, and probably one of the biggest ones we get is on the C2 C3 springs. What color were they painted?

Franz [00:05:57] You know that’s an interesting question. A very simple question, with an incredibly complex answer.

The reason that in 63 that spring was actually designed in 60-61-62 timeframe and there were a number of various designs that came out. But this first design in 63, the only rust inhibitor – and I want to make a very big distinction between a rust inhibiter and rust preventative.

Rockwell always put a rust inhibitor which was tactile 400 C up to the tension set for the spring and then we would immerse the entire palate of springs into the tactile 400 C as well. And that’s a dry to the touch oil. And then in 64 they applied ioniclad 200 J to the tension surface into the sides of the leaves.

Mike [00:06:53] Now the tension surface on a transverse spring that would be the side.

Franz [00:06:58] Facing down.

Mike [00:07:00] Facing the row.

Franz [00:07:01] On conventional laterally mounted springs its the exact opposite.

Mike [00:07:06] Oh yeah.

Franz [00:07:06] Yes that’s correct. And when we, when we did it at our plant in Chatham, we would use a wallpaper brush and when Eaton made them they would use a sponge. So it would be a very very streaky appearance on the tension surface of the leaves.

Mike [00:07:26] So you could actually tell what plant made the spring by looking at the finish line.

Franz [00:07:31] Absolutely. I mean if if you understand leaf springs and particularly the processing element you could distinguish between Eaton and OSB in a heartbeat.

Mike [00:07:42] Just by just by the paint.

Franz [00:07:44] Just by.. Just by the texture in the appearance of the paint.

Mike [00:07:48] *more rumbling* The whole place is falling down, see? That’s another earth shattering discovery.

Scott [00:07:52] This is what editing is for. Don’t worry about that haha.

Mike [00:07:56] Now we get a lot of customers calling and saying “well I know that GM painted the springs gray” and that’s just not true.

Franz [00:08:03] No that’s just not true. You need to take a step back and go through leaf spring manufacturing 101. Whenever we look at painting a leaf spring, imagine a leaf spring plant is a heat treat plant. So there’s more ambient oil in the air, you literally have to cut a hole in the air to breathe at some point.

Mike [00:08:23] It’s not quite that bad.

Franz [00:08:25] I know, that’s pulling it a little too much.

Mike [00:08:28] We’ll have EPA at our doors so let’s be careful. But it’s true it’s not the cleanest environment.

Franz [00:08:37] And what I would tell people and I’ve talked to a number of people in the Corvette hobby about it, is take a piece of steel, spray with WD 40, and try to paint on top of that surface, and you can see obviously it doesn’t work.

The only place in the plant that we were able to apply ioniclad is right after shot peening because there is about a 50 foot area that the residual heat from the furnace and from the shot-peening area, gives you a pretty clean environment to put the ioniclad on. And like I said before we would use wallpaper brush or paint brush and Eaton, when they made them, they would use a sponge.

Mike [00:09:21] So it’s pretty simple and a Corvette spring that comes out of the heat treat it goes through the shot-peening, there’s no clips or anything on a Corvette spring, so you just run a center-bolt through it, and wham bam thank you, its put together pretty quick.

Franz [00:09:34] Well when we applied the ioniclad we applied it to each individual leaf.

Mike [00:09:39] Oh ok. Even before they were assembled?

Franz [00:09:42] Absolutely absolutely. Because if you look at a spring, each leaf there is about three quarters of an inch or as much as an inch gap between each leaf. And that’s called Nip in IP. And the purpose of that is to get equal stress distribution through the spring once it’s assembled.

And the center bolt actually serves no purpose at all. All it does is keep the spring together, the leaves together, until you assemble it into the chassis.

Mike [00:10:14] The centerbolt lines it on the axle and that’s it.

Franz [00:10:15] Yeah yeah yeah yeah yeah yeah. There’s on the axle seat or the stamping, there’s a corresponding hole to accommodate the centerbolt.

Mike [00:10:25] That’s to keep everything lined up.

Franz [00:10:27] That’s right. That’s right.

Mike [00:10:28] Fantastic. Tell us about the grooved steel, the Keystone steel, that was used on the – He’s laughing already- that was used on the C1s.

Franz [00:10:38] That’s an interesting one. I really enjoy that subject. We were at one of the events one time and a gentleman asked me about the grooved springs and I says “well that’s really not the name” I said. “It’s actually called the Keystone section.”

That’s the technical name that was used by the SAE in early years. And how it got that name is everybody knows the world headquarters for steel is Pittsburgh Pennsylvania. And if you look at a keystone section spring you’ll see that the cross sectional area where the Keystone occurs gives you additional surface area, which gives you a much better rate in your spring. So the Keystone section is probably the most efficient designed section for springs ever manufactured.

Mike [00:11:28] Because it lessened interleaf interfriction.

Franz [00:11:31] Well,  that’s a byproduct. When you reduce the interleaf friction, you get a much better ride out of the vehicle, no question about that. But the cross-sectional area, I mean the surface area, what that does that gives you a better bending moment in there. And that’s the reason that they went to it. But if you look at Keystone section springs, they go back to the buggy days.

Mike [00:11:55] Right.

Franz [00:11:56] And one of the interesting parts about it is when you look at a keystone section and if you actually cut it and look at the green structure you’ll see it’s different than a normal rectangular section spring.

Mike [00:12:10] How’s that?

Franz [00:12:11] Well the green structure is more compressed, during the rolling process. If you roll that groove in there or Keystone section it compresses the steel around there. And that gives you a much better tensile strength in a material.

Mike [00:12:27] Like Dixie steel delves into the grooved areas and kind of pushes and pushes off to the side so it kinda pops back a little bit.

Franz [00:12:37] And then it gives you much higher tensile, which is a great thing for the life of the spring as well as the rate of the spring.

Mike [00:12:44] Well answer me this then, you were around back then. Why did they go away from that, because they stopped, GM was the last one to use the Keystone or the groove steel back in the late 50s, if I remember correctly. Why did they go away from that?

Franz [00:12:57] Basic economics.

Mike [00:12:59] Cost.

Franz [00:12:59] Cost. Three things: Cost cost cost.

Mike [00:13:02] Minor detail, location location location. Yeah same thing.

Franz [00:13:05] And one of the interesting parts about it is the last, there is a plant is still rolls keystone section. But they do it for an entirely different application. The problem is whenever you roll that Keystone section in there, the groove part of the rolling dye gets extremely hot and servicing of that dye is exceptionally expensive.

Mike [00:13:27] That’s what we had heard over the years and that’s why the cost of the dyes  was so so high that it was just cheaper to go with a flat end flat stock bar and that was it.

Franz [00:13:39] Absolutely. Everybody made the Keystone at that time Great Lakes Steel or thry call it U.S. Steel, Wisconsin Steel. And the list goes on and on.

Mike [00:13:49] But still it was only so light. One inch and three quarter.

Franz [00:13:51] Inch or three quarter inch.

Mike [00:13:52] Two inch, two and a quarter and that was about it.

Franz [00:13:54] That was about it. There were some discussions even when I got there. But there were some discussions for some possibly some heavy duty applications to continue making them. But it was in a substantial premium.

Mike [00:14:10] It had to be.

Franz [00:14:11] Substantial premium.

Mike [00:14:13] And we talked a little bit about inter-leaf friction. That’s when tip inserts and full length liners come in.

Franz [00:14:18] Absolutely. Very simple. You reduce the friction, you get a much better ride. It’s a matter of fact, if you get into your Corvette, or any car, and if it’s got a leaf spring rear suspension on it. And the first time you hit a bomb it’s significant you really feel it. And that means that you have to introduce enough load to get the suspension to start articulating.

Mike [00:14:41] Would that be called like hysteresis.

Franz [00:14:43] Yeah. This is called hysteresis.

Mike [00:14:45] So that’s a big term we used here a little while ago, hysteresis. And we’re trying to find a cure, but the only cure for it is a tapered leaf spring.

Franz [00:14:57] Yeah.

Mike [00:14:57] That tapered end, rolled end. Yeah. Go ahead.

Franz [00:15:00] But it’s interesting when you talk about hysteresis, it’s not linear. So there is a hysteresis curve going up, and as a hysteresis curve coming down. So what you tried to do is eliminate as much of that and there’s a couple of ways of accomplishing that.

By putting tip inserts which are typically polypropylene and there’s a cup version of it where you put an insert into the cup and that reduces friction. And in the case of the Corvette they put inter leaf liners and those are extruded polypropylene. And that helps tremendously. The more friction you can take out, the better the ride is going to be.

Mike [00:15:39] On the bottom of the Corvette Springs, I’m talking about the C1s.

Franz [00:15:43] Sure.

Mike [00:15:44] There’s numbers stamped on the bottom of those springs.

Franz [00:15:46] Sure.

Mike [00:15:47] What are those numbers?

Franz [00:15:48] Those are the part numbers and the date. And the supplier code. The supplier code for Eaton Corporation was E, and they used Julian dates like 0 3 0 would be the 30th of January February. E would represent Eaton. And then there’s the part number. There’s the heavy duty part number and the standard production part number. And C1 guys on those four leaf leaf springs.

Mike [00:16:16] Yeah. So if you see the part number like 3 7 4 8 1 43, that’s going to be the heavy duty five leaf spring.

Franz [00:16:23] That’s exactly right.

Mike [00:16:24] And then following that is going to be the manufacturer’s code and the date it was made.

Franz [00:16:30] Correct. Right. Now there’s something that you should know, if you’d notice where that date and that stamping is at, it’s always between the center line of the U bolts. The center line of the U bolts is inert material.

Mike [00:16:43] The center bolt is the weakest part of the spring.

Franz [00:16:45] Absolutely. If you if you have a fatigue failure, the propagation point ninety nine percent of the time will be where the center bolt goes through because that spring is articulating in that area and that materials should be inert. Theoretically if you cut from the inside of the u-bolts, took that material out, the spring should work perfectly.

Mike [00:17:08] We’ve always said if a spring breaks between the u-bolts, it’s loose u-bolts.

Franz [00:17:12] That’s absolutely insufficient u-bolt torque.

Mike [00:17:15] Insufficient torque. So the number is stamped in there to reduce what, a stress risers?

Franz [00:17:24] If you stamp it between the centerline that you bolts that’s fine. A few stamping outside the center line of the u-bolts, it becomes an immediate stress riser.

Mike [00:17:31] Exactly.

Franz [00:17:32] And a propagation point for failure of the spring.

Mike [00:17:35] Okay cool.

Franz [00:17:36] And the GM standards is very specific that you’re not to stamp, or any manufacturer’s I.D. , outside the center line of the pupils.

Mike [00:17:45] Yet there’s other manufacturers that do put it on the outside. Ford Motor.

Franz [00:17:49] Sure.

Mike [00:17:51] Chrysler does .But they put it longitude, like put it across, next to the spring. Not in line with the spring. And typically do it out towards the end of the spring.

Franz [00:18:02] Yes they do a two thirds of the distance from the center line to the end of the leaf.

Mike [00:18:06] There you go.

Franz [00:18:07] Because that’s the low stress area of the spring.

Mike [00:18:09] That’s the less, least stressed the area. That is correct. Highest point stress of the spring is where, the tips?

Franz [00:18:16] It depends on the application. Typically it’s two thirds of the distance from the center line of the eye to the center line of the spring. Now there’s two ways of looking at that: one is clamped and one is unclamped.

Mike [00:18:31] Tell us the difference.

Franz [00:18:32] OK. Unclamped is the full length of the spring. Clamp is the full length of the spring minus the distance between the center line of the U bolts.

Mike [00:18:43] We’ve always used the two thirds the difference. So length of the spring has a lot to do with the strength.

Franz [00:18:53] Oh absolutely. Absolutely.

Mike [00:18:55] So when we take out that two thirds difference distance between the U bolts, we’re effectively making a shorter spring.

Franz [00:19:02] Absolutely.

Mike [00:19:03] So the clamp rate is higher than the unclamped.

Franz [00:19:06] Absolutely, no question because the effective length is less.

Franz [00:19:09] Yes. Correct. Exactly right.

Mike [00:19:12] Good. All right let’s get back to the Corvette springs. Tell us about some of the misconceptions you’ve heard about that. Tell everybody listening that know what you heard is not right.

Scott [00:19:23] Is this where we got to really sit down and get prepared for..

Mike [00:19:28] Hold the mike down so it doesn’t rattle the table.

Scott [00:19:30] Yeah. OK.

Franz [00:19:31] You know over the years I’ve talked to many many people about suspensions and particularly about leaf springs, and one of the misconceptions is that Chevrolet would determine the leaf section. Well that’s not quite true. It’s the SAE leaf spring subcommittee of the SAE spring committee that determines what the leaf sections are.

And those leaf sections have a number of influencing factors. Obviously the steel mill has a great deal to do with that. The rolling mills as well as the OEMs. And the OEMs requirements change over time. As vehicles get heavier the suspension requirements need to get heavier, and the more the suspension needs to do. So from that they go to heavier sections.

They’ll go to a thicker section and in some instances a wider section. Now that’s talking about conventional leaf springs. Now you introduce the taper leaf spring. Well that tells a whole new different set of dynamics to it.

Mike [00:20:31] Okay. What’s that got to do with misconceptions and Corvette suspensions?

Franz [00:20:35] Yeah I’m trying to avoid that subject…

Mike [00:20:38] This whole podcast id geared around Corvette suspensions!

Franz [00:20:45] Well one of the other ones is always “Franz, why did they paint springs gray?” I say “well they didn’t. They only painted the tension surface of it.” And most of its education. People, and I don’t want to say this the wrong way, but from a layman’s perspective they don’t know what the tension surface is. They don’t know what to say. Ioniclad is material that we actually plagiarized it from the heavy truck industry. The truck industry was using it long before that.

Rockwell, we put it on in 1964. And what we did is like I said earlier, we used a wallpaper brush or paint brush, kids down the street used the sponge. But the ioniclad is a zinc rich paint. And Ioniclad has two characteristics to it. One is a rust inhibitor, and that’s why I made the distinction earlier. In the second one it acts somewhat as a lubricant and that aides in reducing the inner leaf friction.

The other thing you should know about the ionicald is, throughout the day it would, if it’s a hot day, much of the water, it’s a water based material, would evaporate so it would get much thicker throughout the course of the day. So if you painted the ioniclad on in a high humidity months like July or August you’d actually see globs of paint on the sides of the spring and on the top of this spring. And what happens is.

Mike [00:22:18] Kind of like it was dripping.

Franz [00:22:19] Yes. Yes yes. And when you put that together, that created a problem because you get insufficient torque on a center bolt and that.

Mike [00:22:27] You get movement between the leaves.

Franz [00:22:28] Yes yes.

Mike [00:22:29] We always tell people don’t paint them between the leaves because you get a little bit of movement at your weakest point of the spring.

Franz [00:22:35] That’s right.

Mike [00:22:35] You know you might have, I don’t know thousands of a half, thickness of paint.

Franz [00:22:39] Right.

Mike [00:22:39] But you got seven eight nine leaves and pretty soon you get maybe ten thousands movements in there and a little looseness in the center bolt. Pretty soon you snap the spring at the center bolt.

Franz [00:22:49] There was a term. What was it. There’s a test called a Yankas test it calculates transversal loads. And a transverse load is one of the reasons you get this premature failures if you get insufficient torque on there. It’s just not a horizontal load or if you’re a vertical load would you get these transverse loads in there. It amplifies.

Mike [00:23:15] Kinda like a twist in the spring.

Franz [00:23:16] Yes. Yes that’s exactly right. Exactly right.

Mike [00:23:19] Yeah. That’s one of the loads that takes into effect on how wide a spring is gonna be.

Franz [00:23:24] That’s exact right.

Mike [00:23:24] And a heavy duty truck spring is not going to live with two and a half inch wide, the truck will never survive.

Franz [00:23:30] No no. Heavy trucks, heavy truck springs are about four inch, one hundred.

Mike [00:23:34] Three and a half to four inch.

Franz [00:23:36] It’s 100 millimetres in today’s technology.

Mike [00:23:39] I remember my old heavy duty truck days. Yeah Four inch, five inch thick. Big stack,.

Franz [00:23:45] That’s exactly right.

Mike [00:23:45] Old Hendricks springs, yeah. 280 pounds a piece nothing to it. Very good. We got some customers sometimes with the Corvette spring. Same year car, same spring but you get a ride height difference. What the heck would cause that?

Franz [00:24:01] Oh. I’ve answered that quite.. Well… Let me go back a little bit. One of the Chevrolet guys, I’m not going to mention names here. He had a 58 Corvette and he put GMPD springs on it and the car leaned to one.

Mike [00:24:18] GM PD being..

Franz [00:24:20] General Motors parts division. Yeah. The GM service wing. And the car leaned, and this individual went to, hate to name drop here, but he went to Duntov, and said “How can I fix this?” Duntov said here’s the guy to go to. So I went over looked at their car and I said “you got GM service spring.” He said,” Yes. How do you know?” I said I could tell by the attitude of the vehicle. So I went back and this was a coil spring problem.

And I designed two, well I didn’t design, but I took two coil springs from our plant. And I gave him a matched set. In that set, we got em on. The car set absolutely perfect. The same thing applies to rear leaf springs. You have a tolerance on the rate and you have a tolerance on the load. When you design, you design either to a spring heighth or to a spring rate. Can’t design to both of those. One has to be a reference dimension. And depending if you’ve got two springs, ones on a high side.

The low side of the rate, you know you’re going to have a little issue there. I tell people when you’re going to have a spring redone and you bring it here to EATON Detroit Spring, and this isn’t an advertising program for free, but I know Mike checks the springs, he’ll check the rate, he’ll check the load, and more importantly he shot peens and that’s the critical part of it. And when he designs or restores a spring to the spring height, I guarantee they’re gonna be within spec.

Mike [00:25:53] Shot peen does what?

Franz [00:25:53] Well shot peening, you have to understand, I wanna give you shot peening 101.

Mike [00:26:00] Go ahead.

Franz [00:26:01] There’s two types of shot peening. Ball eye shot where they make the shot from a shot tower where they take molten steel, they drop it in. And the other ones cut shot, where they just cut it off. Both of those processes put a compressive stress on a tension surface of the material and even after all these years, I remember the GM spec like the back of my hand. It’s a ninety five percent minimum coverage with ball eye shot. And what it does it gives you the strength on the tension surface that gives you the life of the spring.

Mike [00:26:36] My mind just went blank! I had a question! Shot peening we like to say it takes unhappy molecules and you massage them into happy molecules.

Franz [00:26:50] That’s exactly right.

Mike [00:26:51] And it will extend the life of the spring, heck, up to 10 times longer in a spring that has not been shot peened.

Franz [00:26:56] Absolutely.

Mike [00:26:57] I remember a time we did a big job for GM General, and they did not call for shot peening. And I told them, you probably want to shot peen these. The engineer says “Nope we’re going to keep the cost down we’re not gonna shot peen. The springs kept failing.

Franz [00:27:10] Springs will fail.

Mike [00:27:11] It kept snapping. They kept snapping. And they called me over to AM General up here at 8 Mile Road and Moun,d and he says “Mike there’s something wrong with your design.” I say there’s nothing wrong with the design, what is wrong is your specs. You have to shot peen them. So we made up some more for them, we shot peened them. We never heard back from them, they worked the one hundred percent. Next deal comes through from them, make sure they’re shot peened.

Franz [00:27:31] Well you know it’s a very interesting subject. One of the things that we did, particularly on on the race cars, we did what we call stress peening. You took the spring, you put it under load, and you have to calculate what load you wanted to use, and then you would shot peen it under stress.

And what that does, that reduces the load height and the amount of deflection that you’re going to get is gonna be significantly less to accomplish the same thing that you would want with a much higher spring height. But what that does it lowers the gross vehicle weight, or the center of gravity the vehicle down lower, particularly race car applications.

Mike [00:28:15] So what else would you like to tell us about Corvette springs?

Franz [00:28:18] Is there anything specific you want to know about them?

Mike [00:28:23] I think we’re at a point in this conversation, and I’ve been around you long enough to know you like to talk. We’re just going to turn out loose and go at it. What would you like to know, what would you like to say.

Scott [00:28:32] FRANZCast.

Mike [00:28:33] FRANZCast! I think we’ll change the name to FRANZCast.

Franz [00:28:36] Springs, as I tell everybody, is probably a very mundane subject. And it’s one of the last parts of the vehicle to be designed because what you have to do is you do a tolerance stack up, and you figure out what the tolerance is of the gross vehicle weight, and then you design a spring for whatever application it is.

Sometimes it’s the front to back ratio is 65 to 35, sometimes 40 to 60 and on and on. And it depends on the vehicle design. Then you have to calculate the difference between this sprung load and the end sprung load and people say “well what’s the difference?” Well it’s rather significant. You don’t have the weight of the tires, or the weight of the rims, or the weight of the lower control arms.

Mike [00:29:26] The axle.

Franz [00:29:27] And the axle, and on and on. And that is the the unsprung load, and that’s what you design leaf springs for. And then you have to calculate, “well how much of the load is front, how much of the load is rear, and obviously we’re focused on the rear, and then how much is left, how much is right.”

And there are differences in there and you need to compensate for that. And I see a couple of other things.

Mike [00:29:52] Well springs are not like most parts of the car. They’re mundane as you say, some people think they are a commodity. It’s not like a windshield wiper.

Franz [00:30:00] That’s right.

Mike [00:30:00] Windshield wiper doesn’t care what the weight of the car is, doesn’t care if it’s a twp-door or four door. Doesn’t care if it’s got air conditioning, where the battery is located, But a spring does. Absolutely. Because the spring supports weight.

Franz [00:30:13] Absolutely. And then, I don’t recall the exact year, but when we had the automotive trade pact between the United States and Canada in the late 60s orearly 70s. One of the things that we had to do is we had to identify the spring is made in Canada, because called Canadian content, and as an OEM supplier we needed to provide them the information of how much Canadian content that they were purchasing from our spring plants in Canada and those springs if… “Made in Canada” is in yellow, that means it was done in a day shift. And if the paint was in white. It was done in the afternoon shift. And if it had a sticker, just a paper sticker on it, that means it was a service spring.

Mike [00:31:01] So besides knowing what color the paint was here, you could also tell what shift it was made on by the color of the paint.

Franz [00:31:11] Correct.

Scott [00:31:12] You can tell whether the guy went to lunch and had a good one.

Mike [00:31:15] And if there was an off shade of yellow, you could tell what he had for lunch. More beer or less beer?

Franz [00:31:24] Yes, not quite that bad, but it gets pretty close.

Mike [00:31:27] Labatts it’s Canada.

Franz [00:31:31] Let’s see what else, that’s about it.

Mike [00:31:34] What else we want to cover?

Scott [00:31:35] Oh I mean, you had a great story about the time that you got yourself a Corvette in high school. Was it? I like that story. We don’t have to put it out but I thought it was good.

Mike [00:31:46] Run it by anyways. What the heck. You’ll give the youngsters some inspiration..

Franz [00:31:50] Well I was a kid, came to America, and I was born in Graz Austria. And I came to America back in the 50s. Ended up at a place called Ecorse, Michigan. And my mother ended up being a janitor at the high school. And our music teacher, Mrs. Garlington, she drove a ’62 corvette.

And Mrs. Garlington in the summertime worked for the Fred Waring orchestra and she did all of the lighting with the gels and everything, and she asked my mother when I turned 16 if it would be okay if she gave me her car to maintain it for during the summer. And of course I was very reluctant to take that responsibility on. But push comes to shove, my mother twisted my arm, and of course I obliged and I took care of her car for the summertime.

Mike [00:32:35] So you were a typical teenager, showing your independence, giving your parents a hard time, and they forced you to take care of the 62 Corvette.

Franz [00:32:43] Yeah yeah. They forced me to take care of it.

Mike [00:32:46] Man I tell you kids today think they have it rough.

Scott [00:32:50] Right. Yeah I could tell you stories.

Mike [00:32:53] Not only did I walk to school uphill both ways, I had to push a 62 corvette around. Or drive one around I should say. So when you say you took care of it, what you do, take it to get oil change every other day or something?

Franz [00:33:06] Oil changes and of course it had to be washed at least once a day. And then you know, you got to put some miles on these cars, you just can’t let them sit.

Mike [00:33:16] Oh yeah. The seals dry out.

Scott [00:33:19] You can’t drive alone in it either.

Franz [00:33:21] no no.

Scott [00:33:21] Make sure the weight is equal.

Franz [00:33:23] That’s exactly.

Scott [00:33:24] Gotta bring your friends.

Franz [00:33:25] And it was it was very very nice.

Mike [00:33:27] Particularly a blonde would offset the weight.

Franz [00:33:30] Parked in front of a high school like that leaning against the car.

Mike [00:33:33] Cigarette pack rolled up in your t-shirt?

Franz [00:33:37] No wasn’t going that way. Now I was a swimmer so I didn’t smoke. So but it was it was interesting. It was an enjoyable summer I can guarantee you that.

Mike [00:33:46] So I see you brought a lot of paper work with you. Anything special you want to talk about there.

Franz [00:33:52] Well when you were talking earlier about the height of the spring.

Mike [00:33:58] Height of the vehicles.

Franz [00:34:00] I wanna share with you a letter that was written.., Now again I’m patting myself on the back.

Mike [00:34:07] You have to. Guys from Rockwell International: “Dear Franz,  front front coils part number 3 7 5 6 5 4 0 are finally in.

Some knuckle busting profanity and eventually transferral to a spring shop finally got them both installed. What a difference! It not only sits higher and looks better, it even steers easier. As you probably remember, that vintage needed all the help we can get the steering areas. Thanks again for the springs. RR Vogel. Division buyer for Chevrolet Motor Company. This was in 1976.

Scott [00:34:45] Yeah it’s got the official letterhead on everything.

Mike [00:34:47] So even the the official buyer for GM understands what it takes to install springs. Knuckle busting profanity, and the only thing he didn’t mention here is what position the tongue was in when it finally fell into place. Wonderful.

Franz [00:35:03] But we’ve done that for, oh a number of people at GM. We were involved with getting springs out the Waterford raceway to a couple of the engineers out there. Of course Rockwell did not support a factory sponsored racing in any way shape or form. But my boss told me to keep the engineers happy now.

Mike [00:35:24] With some surplus stuff we had laying around and we sent out to them.

Franz [00:35:29] That’s exactly right. It was a great time and we we learned a lot and made a lot of people happy out there. So it was it was a great experience no question about it.

Mike [00:35:37] Fantastic. Scott what do you want to know.

Scott [00:35:40] What do I want?

Mike [00:35:41] Tell me how many podcasts have you done like this with this type of knowledgeable people sitting around.

Scott [00:35:47] Well. Usually what I do with these kind of podcasts with the knowledgeable people sitting around, you might have gleaned my strategy today is I let them talk and I look at the levels make sure people can hear it and that’s my job.

Mike [00:36:00] Wise man wise man.

Scott [00:36:02] Yeah I’m the layman that’s just listening here.

Mike [00:36:04] Just bring in the experts and get out of their way.

Scott [00:36:07] Bringing the experts out of the way very little editing done on these kind of podcasts. Just if we mess up the mikes I’ll delete that out. Other than that it’s just I want to hear from the horse’s mouth. How these things are put together, how this all works and I feel like approaching it from the absolute layman’s perspective is good for the listener who is usually a few steps above me in that OK I’m bringing it down to my level so everyone can understand.

Mike [00:36:35] Did we keep it at your level?

Scott [00:36:36] No.

Mike [00:36:41] Where’d we lose you at? hysteresis?

Scott [00:36:43] Yeah yeah I got excited by hysteresis. From there the science plays past me. But like you’re saying earlier, you don’t even know how to spell physicist but when you talk to people about leaf springs and stuff like that you’re talking about the very scientific, actual, relatable, process behind it and the engineering behind that.

Mike [00:37:09] We’ve always said it it’s spring manufacturer all you are is a glorified blacksmith but you’ve got a hell of a lot of study and a hell of a lot of knowledge and a hell of a lot of experience in doing it. It’s not a simple process, it’s an involved process, it takes skilled people, it takes them a long time to learn how to do it, and you just don’t take a piece of steel and heat it and bend it and cool it off, and say here it is, it’s a spring.

Scott [00:37:29] Right.

Mike [00:37:31] It’s a designed piece of steel as we were talking earlier, every length of the leaf has a certain function they have to be certain lengths. If they’re too long or too short, it’ll ruin the integrity of spring.

Scott [00:37:43] Yeah like you were saying in an earlier podcast I think it was an earlier podcast, but the spring is essentially.

Mike [00:37:49] It’s a podcast we’re gonna be doing yeah.

Scott [00:37:50] Oh yeah. I don’t know if it’s this one or not, but a spring is essentially a fingerprint of a vehicle because every vehicle requires a unique spring to its unique way once assembled ends the final step in the entire process the entire design process.

Mike [00:38:07] There is no such thing as a one size fits all.

Scott [00:38:10] No not even even a little.

Mike [00:38:11] No not at all Corvette can get away with having a very limited number of springs because it’s a very, it’s a limited body style. Engines it’s got a big block and a small block. Bingo. They’re within pounds of each other. I mean different versions of the big block and different version and small blocks and pounds of each other. The differences can be in the rear ends, but that’s again that’s unsprung weight on there so you’re you’re fine, so that can have very limited number of springs.

Franz [00:38:36] Sure.

Mike [00:38:37] But you take, a Corvette it’s going to have what, three different springs the majority of them, but you take an FNX body GM it was, if I remember correctly, there was 243 different rear springs for an FNX body GM, so that makes a big difference so.

Scott [00:38:51] It does so even even within a very small set of variables.

Mike [00:38:54] Exactly right.

Scott [00:38:55] Like there’s there’s still it multiplies out into different kinds. What you thought was once a mundane part, is actually almost the DNA of the car.

Mike [00:39:04] Go ahead and get the cheap version, mundane one size fits all spring, and then come back and we’ll talk to you, getcha the right spring.

Scott [00:39:12] Yeah you’ll have a nice bench afterwards.

Mike [00:39:13] Yes. Exactly right.

Franz [00:39:16] Do you know what I like to tell people when it comes to this Mike? Automotive archeology is no different than any other form of archeology. As new information surfaces we must go back and rethink our previous conclusions. And that certainly applies to suspension design and of course I’m very biased when it comes to leaf springs Corvette hobby’s a great hobby. I mean it’s a wonderful group of people, they’re doing it for the right reason, preservation of a absolutely fabulous car that for many of us actually dictated our working careers. I mean for me is 40 some years. So I thank the Corvette hobby for that.

Mike [00:39:53] Going back probably, I don’t know, almost 20 years now, got it in ninety nine. So yes almost 20 years ago, it was my wife’s turn to buy her car. I had mine, it was her turn, we would rotate buying cars. She said she wanted a… We were at the Woodward Dream Cruise and a 58 Corvette went by. She says that’s what I want. I gotta be honest with you, I looked at that and I say that’s an ugly car. OK it’s your turn and that’s what you want. That’s what you get.

Well we ended up buying… I started looking into it. And I realized that it was not a cheap car. But I began to realize, you wanted a matching numbers car. And they weren’t a heck of a lot that much more expensive. So I’ll make a long story short, we search for about a year and I found a car out in California. Woman had it for sale in Hemmings Motor News. And my good friend out there Jim McGowan used to be the editor of the corvette magazine for Peterson publishing for you old timer’s.

And I called Jim and I say “hey Jim, there’s a car out here I want you to go look at.” And he went out and he looked at it for me. If you don’t mind if you go look at. Couple of weeks later, he went out looked at it. He called me, he says I can tell you this: if you don’t buy it I am. So I arranged with the woman to buy the car. At the last moment, she backed out. She decided she wasn’t going to sell a car. She was the third owner of the car. So it was almost six months, seven months later.

And looking at Hemmings Motor News again, I’m saying Here’s an ad for a 60 Corvette, California phone number, I says my God damn it is the same car. I know it is. So I called her, called the number. The same car, cars in the same condition. She wants the same amount of money for it. Unbeknownst to her, I was heading out to L.A. the next week. So I told her OK, on such and such date at 12:00 I’ll be at your front door. She says and I want it cash and I say I will have the cash for you.

You’re not changing your mind on me. So I fly out to L.A. I was out there for business anyways, and I called her the day before and I says Are you going to be here. You’re not going to change your mind? You’re going to be here, I’m going to change my life. I showed up at the front door and I bought the car.

And then I left it there with Jim before I can get it shipped back. And Jim was kind of like you watching at 62 corvette. He made sure it was kept warm and I don’t think the engine ever cooled off while he had it for about a month before he got it shipped back off. He enjoyed my car or my wife’s car very much. Make a long story short, we get the car home. She starts driving it. I really don’t care about it. That’s fine. First car show she goes to she wins best of show with it.

Franz [00:42:17] Oh my God.

Mike [00:42:18] Maybe this isn’t a bad car. The car was totally frame off restoration in 91. We’ve got all the people work on it. Frame-off restoration. Woman bought car. But the car had a frame off restoration, she was the second owner. Not the third owner. We’re the third owner. She was a second owner.

She would drive it five miles to a gas station, to a drugstore, turn it around, drive it home, wash it, wax it, put it away in a garage till the next Saturday, and the garage was carpeted, fully carpeted garage. And if it was raining she wouldn’t drive the car. So when we picked it up in Rancho Cucamonga, drove it back Jim’s house in Moorpark. We put more miles on it that day than it had in five years.

Franz [00:43:00] Oh my God.

Mike [00:43:00] And the next year my wife breaks her knee. She can’t use the clutch. So I started driving the car. She never let me drive the car up until then. I started driving the car. Boy, the attention that car got.

Franz [00:43:12] Oh yeah.

Mike [00:43:13] Well you know what maybe I do like this. And that was almost 20 years ago now and we still have it is, still parked in the garage, heated on a carpet. Yeah.

Scott [00:43:24] It does draw a lot of attention.

Mike [00:43:26] It sure does. They’re nice cars. Very very nice cars. And you meet a unique group of people.

Mike [00:43:31] Sure you do. I’ve got four of them. I’ve got a fifty seven, a sixty two, a sixty three, and a sixty six. And each one’s got their own little stories or a little history back of it.

Scott [00:43:45] Not counting all the ones that you’re watching for other people.

Franz [00:43:47] Oh yeah yeah yeah.

Mike [00:43:51] So the biggest thing we’ve learned today is GM did not paint the springs.

Franz [00:43:59] GM does not paint the springs.

Mike [00:44:00] They don’t paint to springs.

Scott [00:44:02] I got that on video too. I felt like there was some sort of underlining happening in the moments. I was like OK got a break out the video.

Franz [00:44:12] You know someone even suggested that at one time at one of these shows. How do you know when you ship the springs to GM? Well let me let me reverse the time. When we made springs we put a thing was 168 on a pallet. After they were assembled, we dipped it into the textile.

We shipped them to St. Louis. “How do you know they didn’t take the springs apart and paint each leaf and then put it back together?”.

Mike [00:44:36] It’s not how auto plants operates.

Franz [00:44:39] Not an automotive assembly plant, I guarantee you that.

Mike [00:44:44] If they don’t have the right bolt, grab whatever’s on the shelf and stick it in there.

Franz [00:44:48] And then the other thing, the other thing that’s I just found just absolutely hilarious. One of the gentlemen says “You know Franz, how do you know that they use drawings?” “Well drawings are the basic backbone of automotive assembly.”

He said “no no no, drawings are just references for the plant. Plant doesn’t have to use them.”  I said “is that right? Well I learned something today, I did not know that the drawings were just reference material.”.

Scott [00:45:17] Yeah it’s just, you know, for the wall.

Franz [00:45:20] See thats some of the misconception. Yeah but like I said, the hobby is learning.

Mike [00:45:26] Well you know the other thing, when you get to drawings, you get paperwork. Back then everything was done on paper, today’s everything done on computer.

Franz [00:45:32] Yeah.

Mike [00:45:32] So if they made a running change on an application. Part numbers something. Nobody… Printed catalogs didn’t get caught up. They didn’t scrap all those catalogs and reprint them. They’d put up, Ford and GM would put out these cross-reference and obsolescence books.

And they would change part numbers, they would change dimensions, they would make changes. And it never made it to the books that were published already. So when somebody comes up and says well this part numbers you know… And I had an occasion just the other day, somebody is referring to a GM part number, I said that part numbers no good anymore. It’s been replaced by this and the guy said he said no you’re wrong.

And he took a picture of the page and he emailed it to me. And I say That’s great. That was the part number at the time.

Franz [00:46:17] At the time absolutely.

Mike [00:46:18] Since then it’s changed. But why didn’t they change the book? Come on, let’s be realistic about that. If that ten thousand, one hundred thousand books out there, we’re going to go back and go all right I need your book back as we changed the part. No.

Franz [00:46:30] All right, on chart number 3 2 7 4 5 3, which is the sixty three standard spring in the Z 0 6 spring from SOP, which has started production, to the last service change was made nineteen… Nineteen eighty no, Nineteen sixty seven. There were seventy two engineering changes.

Mike [00:46:53] Seventy two.

Franz [00:46:54] I’ll let you read this.

Scott [00:46:56] Good Lord.

Franz [00:46:56] What’s the number?

Scott [00:46:57] Seventy two seventy two right there. Didn’t even bother numbering them all, they came in so fast.

Mike [00:47:03] They go down with somebody changes, they change things.

Franz [00:47:07] Sure they did. They changed, they changed the clip, they change… The clip was for shipping purposes only.

Mike [00:47:16] Exactly right.

Scott [00:47:17] If they changed their socks.

Franz [00:47:20] They change the TPI which is the taper per inch at the end of the leaf. And here’s an important one in Section A of the drawing, they show what they call the curl up or the turn up the reason.

Mike [00:47:33] End of the leaf.

Franz [00:47:33] Yeah the end of the leaf. The reason they do that is that the leaf doesn’t gouge the subsequent leaf underneath it. But they made several changes to that and I think the reason they did that is they found it by changing that angle depending on how much deflection you had in the spring, that it would actually gouge into the next leaf.

So they continued playing with them till they found the angle here that they need to ensure that it never gouged.

Mike [00:47:58] Because that spring loaded is running basically flat. That’s pretty much flat.

Franz [00:48:03] Yeah. Yeah. At load its just .18,  plus or minus a sixteenth of an inch.

Mike [00:48:16] So yeah it’s flat. It’s no longer smiling, it’s no longer frowning. That’s the other thing about a spring, it doesn’t care which way it’s bent.

Franz [00:48:25] No it doesn’t.

Mike [00:48:26] It can be smiling or frowning. It doesn’t care. A springs a spring It couldn’t care less which way it sits.

Franz [00:48:33] The most efficient spring design is when a spring is totally flat.

Mike [00:48:38] Right.

Franz [00:48:38] That’s when you’re utilizing 100 percent of the unclaimed rate of the spring.

Mike [00:48:44] You get to shackle angle in the right position.

Franz [00:48:46] Exactly right. Exactly right. So when you put the extended shackles on the back of your car for the C1 guys, you’re changing the suspension geometry significantly.

Mike [00:48:57] Yes you are.

Franz [00:48:57] Along with that, you may be changing the drive angle, drive shaft angle if you put blocks or anything underneath.

Mike [00:49:06] All these things that fit together. All those parts are designed to be a certain length of certain thing.

Franz [00:49:10] That’s right.

Mike [00:49:11] So once you start messing with how the OE designed it, you’re changing a lot of characteristics of the spring.

Franz [00:49:19] You’re changing more.. Whenever you change something that’s out of spec, you’re changing something else in a suspension.

Mike [00:49:26] More than just that one part.

Franz [00:49:27] That’s right. That’s right. It’s all related. When you’re talking about rate, you got the rate of the tire. You get the rate of the spring, you get.

Mike [00:49:35] How high is the side wall.

Franz [00:49:37] That’s exactly right.

Mike [00:49:39] What shock are you running.

Franz [00:49:40] The dampening rate of the shock. All those characteristics you have to take into consideration.

Mike [00:49:46] It’s just don’t go off and buy whatever fits. Yeah.

Franz [00:49:49] Yeah. Yeah.

Scott [00:49:50] It’s like having this huge complicated machine.

Mike [00:49:53] Sometimes you should probably listen to the guy that actually designs it and makes these things.

Scott [00:49:56] Maybe.

Mike [00:49:57] We just might know what we’re talking about. Well that’d be a first.

Scott [00:50:00] Or just get your torch out and have fun, see what happens.

Mike [00:50:04] We have all done that.

Scott [00:50:11] That was a fantastic podcast.

Mike [00:50:12] You got anything you want to add into it?

Franz [00:50:14] Thank you for the opportunity to talk about a very very dear subject to mind.

Scott [00:50:18] Thank you so much for coming on and sharing your expertise sharing your stories. You’re welcome to come on anytime Mike wants you on.

Mike [00:50:28] You’re welcome. Anytime he wants to be on.

Scott [00:50:30] And I’d love to hear from you more. If you listen to this podcast and you’re like I missed five hundred things. Well. That’s FRANZCast 2. That’s what that is.

Mike [00:50:41] We can do that. We can make that happen.

Scott [00:50:42] Yeah. Why not.

Mike [00:50:43] The mike is always open.

Scott [00:50:45] Yeah. And then there’s always Mike there too.

Mike [00:50:47] He’s always open too.

Scott [00:50:50] Thank you so much for listening to the EATON Detroit Spring podcast. Make sure you subscribe at www.eatondetroitspring.com/podcast to get these episodes whenever they premiere. And thank you to Franz and thank you to Mike.

Mike [00:51:06] Thank you.