Does this 1967 rear spring / leaf-spring look salvageable? (pictures)

[Duke W.]

Re: Does this 1967 rear spring / leaf-spring look salvageable? (pictures)

Scott,
Test each leaf separately using a bathroom scale as shown in the picture.

Deflect spring 1 through 5 a distance of 2 inches measured at the center and spring 6, 1 inch (spring #1 being the longest).

The numbers for a repro spring are around 30 lbs for spring #1; 50 lbs for springs 2,3 and 4; 60 lbs for #5 and 70 lbs(@1inch deflection for #6)

Spring 7,8 and 9 are difficult to test at home.

These numbers for repro spring are stiffer, yours are going to be a lot less.

You can do this test before any cleaning.

The picture shows a wheel dolly for the support but anything that is low and rolls should work i.e. skate board. It only takes about 15 minutes to do this.

Any unseen cracks will show very low numbers.

Post your numbers and a picture of your set-up so we can have a look.

That's a good test. Another would be to weigh a spring known to have no corrosion to get a baseline. A severely corroded spring will weigh less due to loss of material, but I don't know what weight would indicate the spring should be replaced.

Most old springs look a lot worse than they really are due to the ugly surface rust. Getting all the leaves cleaned up and doing a thorough visual inspection is still a necessary test. Minor pitting is not big deal, but if there are areas with major material loss, it gets iffy.

Due to the fact that replacement springs do not have the same engineering characteristic as originals, owners should make every attempt to restore the original spring.

Duke

[Scott S.]

Re: Does this 1967 rear spring / leaf-spring look salvageable? (pictures)

Scott,
Test each leaf separately using a bathroom scale as shown in the picture.

Deflect spring 1 through 5 a distance of 2 inches measured at the center and spring 6, 1 inch (spring #1 being the longest).

The numbers for a repro spring are around 30 lbs for spring #1; 50 lbs for springs 2,3 and 4; 60 lbs for #5 and 70 lbs(@1inch deflection for #6)

Spring 7,8 and 9 are difficult to test at home.

These numbers for repro spring are stiffer, yours are going to be a lot less.

This was easier said than done (naturally). I couldn't get leaf # 6 (shortest of leaves 1 - 6) or spring 5 to deflect the required amount (1" and 2", respectively) without putting most of my body weight (about 170lbs.) on it by standing with my feet on either side of the center bolt-hole, leaning on a table to vary my weight on the leaf to the correct mark on the tape measure. When I had the leaf deflected the correct amount, it was difficult to turn and look at the scale while maintaining a constant deflection height.

I measured a couple times with each leaf to make sure I was getting consistent measurements for each leaf. It doesn't seem right, but this is what I came up with:

Leaf 6 (shortest) at 1" deflection = 70 lbs.
Leaf 5 at 2" deflection = 80 lbs.
Leaf 4 at 2" deflection = 70 lbs.
Leaf 3 at 2" deflection = 41 lbs.
Leaf 2 at 2" deflection = 30 lbs.
Leaf 1 (longest) at 2" deflection = 35 lbs.

The square "dolly" is on wheels, the scale is a standard bathroom scale zeroed to compensate for the weight of the leaf-spring before beginning deflection. I tried to make the height of the scale equal to the height of the dolly, so that the leaf-spring was approximately level.

[Steve L.]

Re: Does this 1967 rear spring / leaf-spring look salvageable? (pictures)

NIce job Scott,

Scott Steve Repro
6 70 70 70
5 80 45 61
4 70 33* 50
3 41 32* 51
2 30 26 46
1 35 -- 31

I've compared your numbers, my numbers(original spring) and Repro numbers.
My #1 was broken through the bolt hole so I don't have numbers.
Also my springs looked comparable to yours.

#1: Yours looks comparable to a repro. The repro's have a substantially shallower arch, probably in an effort to compensate for the thicker material. That's probably why your getting the same numbers.
#2: Yours looks comparable to mine, both are, as expect, lower than repro
#3: Yours looks better than mine, The * means I chose to replace it with a repro leaf since I thought it looked low.
#4: Yours is actually more than a repro. Probably a measurement error since it gets harder to measure when the spring gets shorter. In any case it looks like a decent number. I chose to replace mine since it looked low.
#5: Same as 4 above. Mine looked a bit low, but in the end I decided to keep the original.
#6: All three match.


Looks like you have some decent numbers. Once you clean them up, go over them once again and check for any nicks are large pits that could be stress risers.

It's a bit easier to do with 2 people, one stomps on the spring and reads the scale, the other, reads the tape measure. The weight you need to put on the middle of the spring is actually double what the scale reads. This is why you need to put a lot of your weight on the shorter springs. It is also the reason I opted for only a 1 inch deflection on #6.

I wish I could get a hold of a pristen spring. I might be able to get access to an Instron which would give me a graph of the entire deflection range of each leaf so we could all get more precise number for our home brew test.

[Gary B.]

Re: Does this 1967 rear spring / leaf-spring look salvageable? (pictures)

Steve,

I wish I could get a hold of a pristen spring. I might be able to get access to an Instron which would give me a graph of the entire deflection range of each leaf so we could all get more precise number for our home brew test.

Why not simply calculate the deflection for a single leaf using beam theory? For elementary beam bending, the only difference in terms of what enters the equation should be the leaf thickness. For a single leaf I'd trust that calculation more than I would a balancing act of leaf and person on a typical bathroom scale.

Gary

[Steve L.]

Re: Does this 1967 rear spring / leaf-spring look salvageable? (pictures)

Gary,
You right, and I've got the equations for a curved beam. For these homebrew test we are in the curved beam portion of the deflection. We are no where near the flat portion that the spring actually is stressed at. I had actually measured the curves for each of these springs in anticipation of doing this.

Curved beam calcs are more involved than flat beams. I need to set the equations up on a computer. I've intended to do this for quite some time but haven't had the time. I'm passed this point on my resto and I'd rather be wrenching on my chassis rather than computering since I stare at a computer all day at work.

The ultimate purpose of this homebrew test is to determine if the particular spring leaf is still useable during restoration. As I was doing my chassis resto, and when I got to the spring, it took me a while to try and figure out an engineering approach for testing an individual leaf that could be done at home with a mininum set-up and with readily available apparatus. This way a restorer could mix and match leaves with original and repros(if required) using some logical decisions. The goal is to use the originals as much as possible because of the ride height problem.

Given the problems with ride height, and the simplicity of this test, I'm surpised that no one has come up with this test long ago.

[Tracy C.]

Re: Does this 1967 rear spring / leaf-spring look salvageable? (pictures)

.........

It's a bit easier to do with 2 people, one stomps on the spring and reads the scale, the other, reads the tape measure. The weight you need to put on the middle of the spring is actually double what the scale reads. This is why you need to put a lot of your weight on the shorter springs. It is also the reason I opted for only a 1 inch deflection on #6.

Why don't you just limit the deflection of the sprng by inserting a stop underneath the middle of the spring? If you want 2 inches of deflection, cut a piece of pvc pipe (or board stackup, etc) to a height that will limit the deflection of the spring to 2 inches. Just insert the stop under the middle of the spring. Then put your full body weight on the middle of the spring and read the scale.

No quesswork, no fumbling a tape measure or trying to read it in a awkward position.

I'm getting ready to rebuild my 63 spring and may do this just to add another data point.

tc

[Mike G.]

Re: Does this 1967 rear spring / leaf-spring look salvageable? (pictures)

i have seen worse clean up nice. that steel on the springs is pretty hard so the rust does not pit as bad as regular steel. other than the bottom spring all you see are the edges. i cleaned my edges up with a file.

[Steve L.]

Re: Does this 1967 rear spring / leaf-spring look salvageable? (pictures)

Why don't you just limit the deflection of the sprng by inserting a stop underneath the middle of the spring? If you want 2 inches of deflection, cut a piece of pvc pipe (or board stackup, etc)
tc

Tracy,
That would work, but you we need 6 different lengths of pvc and you cannot put any weight on this stop or you will just add to the measurement uncertainty. The only places you want contact point is the scale, the roll thing and your foot.

The tape is just the least amount of set-up.

However, thinking more on your lines, maybe putting something standing up along side the spring(cardboard box?), marking the top of the particular spring on the box with a sharpy, then measuring down 2 inches with another mark. This would probably be easier than a tape measure.

This is a great example of engineering collaboration and developement at its best. You and I should get together and put a spring measurement kit together and sell it for $9.99 and retire in 2040.

[Tracy C.]

Re: Does this 1967 rear spring / leaf-spring look salvageable? (pictures)

Tracy,
That would work, but you we need 6 different lengths of pvc and you cannot put any weight on this stop or you will just add to the measurement uncertainty. The only places you want contact point is the scale, the roll thing and your foot.

.....

I understand the different length requirement for the stops, but there will be no addtional force applied to the spring once it bottoms on the stop regardless of the amount of weight standing on it.. The spring will deflect 2" (or whatever) and the scale will read only the force of spring deflection at the scale. No more, no less. The stop just takes the variation out. I'd wager that if you did the same test on the same leaf 10 times using only a tape measure, you will get at least a 10% variation in the reading. Repeat this test 10 times using a stop and you will reduce the varation to around 1%.

Another improvement here would be to put a piece of thick metal plate or plywood (.25 inch or so) between the spring tip and the scale. A person would need to zero the scale to accomodate for the weight of the plate, but this would distribute the load across the scale's service rather than allow the spring tip to bend and deflect the scale causing an inaccurate reading.

When a person steps on a bath scale, the weight is distributed across the scale's surface through the total area of the bottom of your feet. The plate would do the same thing.

tc

[Steve L.]

Re: Does this 1967 rear spring / leaf-spring look salvageable? (pictures)

Tracey,
I stand to be corrected. Your right, a stop under the spring at the deflection wouldn't affect the results and would be more precise as you say. By the time you hit the stop the roller would stop moving.

Perhaps a floor jack or bottle jack would be easier to set up rather than pvc pipes cut to length.

Also, I tried to center the spring on the floor scale to accomodate the design of the floor scale for just the reason you stated. But a flat plate or plywood would be better.

Oh ya and I would avoid the glass style floor scales.

[Tracy C.]

Re: Does this 1967 rear spring / leaf-spring look salvageable? (pictures)

I like the floor jack idea! A low profile portible like the one I carry in my trunk might work OK. Either that or come up with a lead screw type adjustable stop. How about a C2 jack?

Something tells me we need to raise the price point on the kit however. We will go bankrupt at $9.99

tc

[Steve L.]

Re: Does this 1967 rear spring / leaf-spring look salvageable? (pictures)

Tracey,
When do you plan on doing your spring?

[Tracy C.]

Re: Does this 1967 rear spring / leaf-spring look salvageable? (pictures)

I'm about 3 weeks out on the spring. It will be that long before I get my work bench clear of the other rear suspension items.

I'll post results when I'm there.

tc

[Tracy C.]

Re: Does this 1967 rear spring / leaf-spring look salvageable? (pictures)

Tracey,
When do you plan on doing your spring?

Steve,

Finally got some measurements from my 63 spring. I also had a nice spring from a 65 so I decided to restore it while I'm at it. I found some interesting differences in configuration, but I'll start a new thread to cover those items.

........ 63 spring...... 65 spring
leaf 1...30 lbs........... 30 lbs
leaf 2...40 lbs........... 40 lbs
leaf 3...47 lbs........... 50 lbs
leaf 4...60 lbs........... 62 lbs
leaf 5...80 lbs........... 86 lbs
leaf 6...65 lbs........... 70 lbs

All measured at 2" deflection except leaf 6 at 1" deflection. My test setup is pictured below. I used my jack as a deflection stop. It work perfect and was easy to adjust for each leaf. My work bench is covered with formica and slippery so I didn't see a need for the roller dolly on the end opposite of the scale.