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Since there isn't a section for frame/chassis restoration... and since this fits more than the Chief/Scout/Four, I thought I would post this here.
This weekend, I started working on restoration of the spring pack of my '38 Chief. It was all shiny nice with spiffy paint on it. But was fused together like it was forged from a single billet. No surprise there... many vintage vehicles have spring packs like that. And people accept that old cars ride like buckboards... when, in fact, the early leaf springs were generally very supple and comfortable. If maintained.
First, a couple of factoids. First, springs slide on each other. They need to have a lubrication film between them. They don't bounce... they slide. If they are not lubricated, they will gall and lock quickly. Second, paint on leaf springs... necessary, yes. But don't put the spring pack together dry as a bone then paint, hoping that all that paint will stay pretty on the outside. It won't. Because it will act like glue and stick the springs together nicely. Then crack as the leaves slide. Third, and most important, is the most basic fact of rust:
Rust is 9 times thicker than the metal it replaces. In other words, for every .001" that rust 'eats' into metal, iron oxide (rust) "grows" outwards by .009". So if you are rusting just .003" into the spring (the thickness of a sheet of typing paper) the rust that is packing between your spring leaves is .027" thick. The thickness of 9 pieces of typing paper. Consider how thick that is... in between each spring leaf. And consider that rust is a wonderful abrasive! Especially when put between sliding surfaces. The phenomena, by the way, is called "Rust Smacking" and you see it in old springs that have 'grown' apart visibly. Also on those federally-funded bridges that are falling down.
So what to do about it?
The only answer is to take the spring pack apart, degrease, clean, bead blast and linear grind the surfaces until they are smooth. Then there are some tips for painting them and lubricating them... but that will be in the next installment.
Here I'll just show some pictures from my Chief spring pack as I worked on it this weekend.
This is a typical leaf. It is rusted, completely dry and had paint holding it together... keeping moisture in and lubrication out. It had likely never been oiled. There was no trace of grease oil... I mean, that would make the paint not stick, right? Don't oil it. You can also see the remnants of the slag on the outside of the leaf from when it was made/hot rolled. This is awful stuff inside a spring. It galls and it's rough. Why it was not removed when 'new' I have no idea. If it was a repro spring pack, it was a bad one. But I don't think it was... I suspect that it was simply put together to a price and it was assumed that lubrication would cure all
This shows the galling at the end of the leaves. Note how the striations run along the spring. Also note how the nose of one leaf is digging into the other one. That will cause a ridge, eventually, that will act like a slide stop with bad effects on your spring. We'll look at how to prevent that (besides good lubrication.) Again notice that it was dry and you can see the galling that was taking place between the leaves.
Here we see the beginning of repairing the springs. From left to right...First spring is as-removed. Note galled areas, red rust, dark rust and the area where the nose of one spring dug into another
Second from left is a spring that has been bead blasted over half its length. Use glass and not heavy sand. You want to remove the rust, not work-harden the surface. Bead until the pits are clean. You can't just wire brush them. The rust is a lot harder than the 'wire' on your wire brush. All you do is plate the rust with a layer of metal wiped off your wire brush. Looks good... but not cleaned of rust. You must abrasive blast to properly clean a spring. Also, on these springs, all the slag from hot-rolling was blasted off, taking the metal to pure white blasted finish.
Third spring has been linear ground on a big belt sander. Cut ONLY along the length of the spring, never across the leaf. Cross sanding will put in scratches that can turn into breaks. You must grind only along the length of the spring. Grind the edges as well. You do not need to grind every pit out. Pits will hold oil and springs will slide on the high points. And you don't want to thin the springs too much. More than 20 percent, BTW, and you need to scrap the spring. But some pits are ok at this stage.
Last spring is after burnishing with a wire brush. This lays down the metal raised by both belt sanding and by blasting and will give you a burnished smooth finish. The leaves, at this point, will slide over each other like glass -- even without lube. You will have NO roughness or binding at this stage. This is what you are shooting for.
Here is a closer view of springs showing that some pits remain and showing the shiny/burnished finish of the leaves.
This close-up shows the finish of the spring as finished and after blasting, grinding and wire brushing. Note that all the scratches run lengthwise, that the edges are smooth and that some pits are fine. The spring will ride on its high spots.
This is how you keep springs from digging into each other. As they come from the factory, the 'tips' are sharp and show that they were simply 'cleved' off by a cutter. That sharp edge acts as a cutting tool, especially when combined with some rust and dry surfaces. By gently chamfering the edges, the spring won't 'plow' into the other spring, but will ride along its mating surfaces. And as spring does wear (you won't prevent wear entirely) the gentle chamfer will prevent the worn area from becoming so distinct or deep.
Later this week, we'll be prepping these for painting, installing the spring eye bush (and pin honing it) and then assembling the pack and I'll take some pictures and post those steps. There are some really simple tricks for painting, involving a handful of pennies and some masking tape.
FYI, these are techniques we've been using on antique cars for decades. Putting a new engine in a chassis that rides like a buckboard... is a waste of time and energy. Old cars (like old bikes) deserve the suspension the factory intended them to have.
BTW, along with this, all the front fork rocker bushes, bearings, pins, etc on the Chief are being 100 percent replaced. No point in having a nice bouncy spring pack... and rattle-trap suspension parts. So far, gotten parts from Greers and am very happy with the quality.
Cheers and feel free to ask any questions... and I'll be glad to answer or post some additional pictures.
Sirhr
This weekend, I started working on restoration of the spring pack of my '38 Chief. It was all shiny nice with spiffy paint on it. But was fused together like it was forged from a single billet. No surprise there... many vintage vehicles have spring packs like that. And people accept that old cars ride like buckboards... when, in fact, the early leaf springs were generally very supple and comfortable. If maintained.
First, a couple of factoids. First, springs slide on each other. They need to have a lubrication film between them. They don't bounce... they slide. If they are not lubricated, they will gall and lock quickly. Second, paint on leaf springs... necessary, yes. But don't put the spring pack together dry as a bone then paint, hoping that all that paint will stay pretty on the outside. It won't. Because it will act like glue and stick the springs together nicely. Then crack as the leaves slide. Third, and most important, is the most basic fact of rust:
Rust is 9 times thicker than the metal it replaces. In other words, for every .001" that rust 'eats' into metal, iron oxide (rust) "grows" outwards by .009". So if you are rusting just .003" into the spring (the thickness of a sheet of typing paper) the rust that is packing between your spring leaves is .027" thick. The thickness of 9 pieces of typing paper. Consider how thick that is... in between each spring leaf. And consider that rust is a wonderful abrasive! Especially when put between sliding surfaces. The phenomena, by the way, is called "Rust Smacking" and you see it in old springs that have 'grown' apart visibly. Also on those federally-funded bridges that are falling down.
So what to do about it?
The only answer is to take the spring pack apart, degrease, clean, bead blast and linear grind the surfaces until they are smooth. Then there are some tips for painting them and lubricating them... but that will be in the next installment.
Here I'll just show some pictures from my Chief spring pack as I worked on it this weekend.
This is a typical leaf. It is rusted, completely dry and had paint holding it together... keeping moisture in and lubrication out. It had likely never been oiled. There was no trace of grease oil... I mean, that would make the paint not stick, right? Don't oil it. You can also see the remnants of the slag on the outside of the leaf from when it was made/hot rolled. This is awful stuff inside a spring. It galls and it's rough. Why it was not removed when 'new' I have no idea. If it was a repro spring pack, it was a bad one. But I don't think it was... I suspect that it was simply put together to a price and it was assumed that lubrication would cure all
This shows the galling at the end of the leaves. Note how the striations run along the spring. Also note how the nose of one leaf is digging into the other one. That will cause a ridge, eventually, that will act like a slide stop with bad effects on your spring. We'll look at how to prevent that (besides good lubrication.) Again notice that it was dry and you can see the galling that was taking place between the leaves.
Here we see the beginning of repairing the springs. From left to right...First spring is as-removed. Note galled areas, red rust, dark rust and the area where the nose of one spring dug into another
Second from left is a spring that has been bead blasted over half its length. Use glass and not heavy sand. You want to remove the rust, not work-harden the surface. Bead until the pits are clean. You can't just wire brush them. The rust is a lot harder than the 'wire' on your wire brush. All you do is plate the rust with a layer of metal wiped off your wire brush. Looks good... but not cleaned of rust. You must abrasive blast to properly clean a spring. Also, on these springs, all the slag from hot-rolling was blasted off, taking the metal to pure white blasted finish.
Third spring has been linear ground on a big belt sander. Cut ONLY along the length of the spring, never across the leaf. Cross sanding will put in scratches that can turn into breaks. You must grind only along the length of the spring. Grind the edges as well. You do not need to grind every pit out. Pits will hold oil and springs will slide on the high points. And you don't want to thin the springs too much. More than 20 percent, BTW, and you need to scrap the spring. But some pits are ok at this stage.
Last spring is after burnishing with a wire brush. This lays down the metal raised by both belt sanding and by blasting and will give you a burnished smooth finish. The leaves, at this point, will slide over each other like glass -- even without lube. You will have NO roughness or binding at this stage. This is what you are shooting for.
Here is a closer view of springs showing that some pits remain and showing the shiny/burnished finish of the leaves.
This close-up shows the finish of the spring as finished and after blasting, grinding and wire brushing. Note that all the scratches run lengthwise, that the edges are smooth and that some pits are fine. The spring will ride on its high spots.
This is how you keep springs from digging into each other. As they come from the factory, the 'tips' are sharp and show that they were simply 'cleved' off by a cutter. That sharp edge acts as a cutting tool, especially when combined with some rust and dry surfaces. By gently chamfering the edges, the spring won't 'plow' into the other spring, but will ride along its mating surfaces. And as spring does wear (you won't prevent wear entirely) the gentle chamfer will prevent the worn area from becoming so distinct or deep.
Later this week, we'll be prepping these for painting, installing the spring eye bush (and pin honing it) and then assembling the pack and I'll take some pictures and post those steps. There are some really simple tricks for painting, involving a handful of pennies and some masking tape.
FYI, these are techniques we've been using on antique cars for decades. Putting a new engine in a chassis that rides like a buckboard... is a waste of time and energy. Old cars (like old bikes) deserve the suspension the factory intended them to have.
BTW, along with this, all the front fork rocker bushes, bearings, pins, etc on the Chief are being 100 percent replaced. No point in having a nice bouncy spring pack... and rattle-trap suspension parts. So far, gotten parts from Greers and am very happy with the quality.
Cheers and feel free to ask any questions... and I'll be glad to answer or post some additional pictures.
Sirhr
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