TR2/3/3A New Leaf springs.

There are several old threads on replacement leaf springs. My question was addressed but I did see a definitive answer.

I ordered new sleaf springs from Rimmer Brothers in the UK. The exchange rate helps with the price. When they arrived I notice that the Rebound clips are not clamped down to the top of the main leaf. Exactly as described on the Moss springs several years ago.

The question was. Leave as delivered or hammer the clips down to the leaf.

David

Those stenciled numbers sure do look familiar ...


The workshop manual is fairly emphatic about making sure the clips grip the leaves, so that is what I would do. But given all the hassle I had with the spring pictured above, I would also try to check the spring rate before doing anything else. The stock rate is supposed to be 128 lb/in; the new springs I got were almost twice that! Held the axle firmly against the frame all the time, rode like a lumber wagon and handled worse.

TR3driver said:

Those stenciled numbers sure do look familiar ...

The workshop manual is fairly emphatic about making sure the clips grip the leaves, so that is what I would do. But given all the hassle I had with the spring pictured above, I would also try to check the spring rate before doing anything else. The stock rate is supposed to be 128 lb/in; the new springs I got were almost twice that! Held the axle firmly against the frame all the time, rode like a lumber wagon and handled worse.

Click to expand...

That's certainly not good news. Hope Rimmers will make it right.
Here's a spring rate calculator.
https://www.suspensionmaxx.com/tech-support/leaf-spring-calculator/
Tom

I get a very high spring rate using the calculator. Hope I made an error somewhere.

Springs are 2" wide and 0.230" thick.
42" , 38", 32.5", 26", 18", and 11".

I come up with a figure of 2206.40 Pounds per inch.

David

Substituting 0.22" for the thickness which is what my original springs are I get 1935.95 pound per inch.

If the manual calls for 128 Lb/in my springs sound more like big truck springs.
Placing them on the floor I can get some deflection when I stand on them. I am 155lb

David

Dave in most bigger cities springs are made up for trucks and such. I got a quote of 150.00 each to fab up some tr3 springs after I showed them mnie. The big spring is the problem for them because they need to make that loop

Not sure that Macon GA makes it as a big city. I will check around though.

I notice that the old springs the leaves are tapered at the ends.

Was only going to replace them because it is such a pain to do with the body on the frame.

Did get a pair of shocks at only a little more than a rebuild job.

David

Oh good. Your .230" is thinner than my new springs were (.237"), so maybe yours are OK (or at least better).

Yeah, something pretty badly wrong with that calculator. Apparently, it is assuming that all of the leaf ends are connected rigidly together, so that the little short leaf (which in reality does very little) is the stiffest leaf. As a test, I tried entering the 6th leaf as being only 1" long (which is less than the length of the clamp), and it claimed that would produce a spring pack of over 1 million lb/in!

However, I think it is OK for calculating one leaf (except there is no way to account for the tapered leaves); it just isn't adding them properly. Note that with the original springs, only the master leaf is .22 (.219 by the book). The other 5 are supposed to only be .188" thick.

I measured 3 original springs, and got values from 110 to 145. The 145 was pretty rusty, so higher friction between the leaves likely played a role. The replacement spring came in at 222! Here's a shot of my lashup to check spring rate:

There is a second needle valve that isn't quite visible (hangs down behind one of the support bars). It and the one that is visible allow adjusting the amount of air inside the cylinder, while the gauge reads the resulting pressure. Since I know the area of the piston, I can calculate the force applied to the spring, and measure deflection with a handheld ruler (not shown). I took two sets of measurements, one with the spring rising and the other falling, and averaged them for the final calculation. Hopefully that eliminated or at least reduced the effect of friction between the leaves.

Here are the specs for the 208636 spring

sp53 said:

Dave in most bigger cities springs are made up for trucks and such. I got a quote of 150.00 each to fab up some tr3 springs after I showed them mnie. The big spring is the problem for them because they need to make that loop

Click to expand...

That's what I plan to do as well. There used to be one just a few miles from me, but they are gone now and I haven't taken time to resume the search. However, I'm going to take them the drawing from the TR3 workshop manual plus the table above.

Threads like this are why I replaced my RH broken spring with a used one. Ride height matched really well and so far (about 5 years) so good.

The guy I got the used ones from is using the Moss supplied springs - but it is an 18 year (and counting) restoration so he doesn't know what the result will look like yet.

This calculator comes up with a closer number.
I found several other calculators but some did not work and some wanted the Modulus of elasticity of the main leaf?

https://www.auto-ware.com/calcs/leaf.htm

David

Years ago I bought a bathroom scale that goes up to 400 lbs. Originally I bought it to measure the loaded height of valve springs...but since it has proven useful for inumerable checks. If you want to get the true rate, mount the spring in a press and load it with a scale under it. Measure the weight at 1" compression, then 2" if it goes high enough. You then have the exact rate.

Calculations are great....as a trained engineer I spent a lot of time calculating spring rates. As with all automotive springs, we do not know the steel used or the hardness it was treated to. The calculations will be ballpark at best. Even with the best quality springs you get pretty large variations, and direct measurement is still the only way to tell what you really have.

DavidApp said:

some wanted the Modulus of elasticity of the main leaf?

Click to expand...

Also known as "Young's modulus". Should be pretty close to 200 GPa.
https://www.matweb.com/search/datasheet_print.aspx?matguid=3a9cc570fbb24d119f08db22a53e2421

FWIW, I tried going the same route as Geo suggests above; replacing both springs with originals from someone else's restoration. But it's only been a few years, and the driver's side has sagged noticeably. I'm guessing I'll find another cracked leaf. Maybe I'm not being careful enough when torquing the U-bolts or something.

I had the same issue...did you see this thread in the Advanced Search: Leaf Spring "rebound clip" thickness...

Am update on the springs.

I made a crude test rig to do as John suggested so that I could measure the real spring rate.

After taking up the slack I zeroed the scale and applied pressure to the spring to get 1" of deflection. The scale read just over 140 lb. If I go to 2" deflection I get 260 lb.

Does that mean the spring rate is OK for the TR3.

During a Google search I came across a UK spring maker that lists this spring but it shows it for a TR4 they had a different number for the TR3 spring.

David

That is the pair of fiberglass front wings and apron that came with the car in the background.

Not sure what to do with them but they are from The Roadster Factory.

David

Found the site. It is GB Springs Heritage Springs and they list a different spring for the TR3.
Now what to do about the rebound clips. Leave them alone or attempt to re bend them?

David

https://www.gbsprings.co.uk/heritage-car-springs/

DavidApp said:

After taking up the slack I zeroed the scale and applied pressure to the spring to get 1" of deflection. The scale read just over 140 lb. If I go to 2" deflection I get 260 lb.

Does that mean the spring rate is OK for the TR3.

Click to expand...

Sounds fine to me. There is only a slight difference in specification between the TR4 and TR3 springs, seems like most vendors (including TRF) sell TR4 springs for the TR3. The difference is only in ride height, all the other specs remain the same. The TR4 installed height at the spring (called camber) is supposed to be between 3/8 and 5/8; while the book allows 5/8 to 1-1/8 for the TR3. But, it's easy enough to lower by the difference, if you want to. Just add some shims (bits of old spring leaf will do) between the springs and the axle.

Thanks for the info on GBsprings. I may turn to them if my other leads don't pan out; but I'm guessing that shipping from the UK will be kind of high. Those springs are heavy!

Returning to the leaf spring issue.

After a lot of digging I came across this company. They did not have the specs for the TR3 spring so I sent them a copy of the drawing from the hand book. Said he could make springs to that design including the tapered ends on the leaf. They are a lot more than the springs from TRF or the UK.
I am still considering what is the best plan to go with. Leave the old springs. Use the UK springs or put the UK springs on e bay and go with a pair made by Eaton.

David

https://www.youtube.com/watch?v=-3e5GZx_8jg
EATON Detroit Spring, Inc.