My inexpensive w123 spring compressor - PeachParts Mercedes-Benz Forum

Admiral Ahani · #1 09-04-2012, 02:37 AM

I recently did a front end job and I had to r&r the springs. I'm always interested in expanding my tool collection, and I'm really into making things myself.

It's a 3/4" threaded rod with acme threads (the thick flat threads you see on tools), with one nut welded to one end, and one free nut. Two 3/4" washers. The plates are actually spring perches from a w126. I knew these would work because taking the load of a Mercedes spring is what they're made for!

I cut the edge off of the perches so they could be inserted between loops. I made sure that I retained the part of the perch that dips down, so the plate would end up as helical as possible. Then I used a dremel to cut a 3/4" hole in the middle of the perches (it was the only method available at the time and I was pressed for time).

It worked beautifully. The total cost was about $40. I scored the nuts on ebay for about $15 (these nuts are really expensive so that was a deal). I got the rod from grainger for about $17, picked it up at the store. I had the washers already. The spring perches were a few bucks each from Pick n Pull. I wish I bought w123 perches, because apparently w126 springs are wider! Even with the perches being larger than my springs, it still worked. If I had w123 perches, I wouldn't have had to cut off as much material (for clearing the frame rail).

So now you can have a cheap sturdy spring compressor. The only catch is the welded nut - if you don't have a welder (most people don't) just take it to a muffler shop and they'll do it for $5-10. I used to do that, then I just invested in a little welder.

Stretch · #2 09-04-2012, 02:39 AM

What's the strength rating on the nuts and the bolts?

Secondaries · #3 09-04-2012, 09:31 AM

Quote:

Originally Posted by Army

What's the strength rating on the nuts and the bolts?

Good question. Either way, i like the ingenuity and knight try to go this route when I'm ready to lower my wagon 8-)

charmalu · #4 09-04-2012, 10:33 AM

The spring perch is the plate that is bolted to the lower control arm?

The plate is a full round piece, cutting off one side seems like it would take away some of its strength.

Some of the force of the spring is pushing on the lower control arm, not on the total plate. How much force is excerted on the plates as the spring is being compressed? now 2 pieces of sheet metal are containing the spring.

When in it`s mounting, one end is contained in the upper cup area, and the lower end is sitting on this sheet metal perch. far less force in this state than when it is compressed.

I also wonder about the strength of the threaded rod threads and the nuts.

You were definately thinking out side the box, I commend you on making your own tools. I have the after market Klann clone spring compressor I picked up on CL, brand new, for $75.00. even that one makes me nervous when the spring compressed.

Charlie

vstech · #5 09-04-2012, 12:12 PM

... hmm

Diesel911 · #6 09-04-2012, 12:14 PM

The use of the Lower Spring plates is clever!

A longer Nut can be had by using a Rod Coupling Nut used with regular threads and size of the Threaded Rod and Nut could easily be increased if someone is worried about that.
The regular Hardwar stores do not sell them in my area but you can get Grade 5 rod coupling Nuts; that is about 8.8 metric grade.

ROLLGUY · #7 09-04-2012, 12:31 PM

I had a former job that we used Acme threaded items in the fabrication of the product we manufactured. Standard threads would not work for high load linear applications. You will find that all screw jacks, bottle jacks (the adjustable portion on top) and other types of machines use Acme threads. I have no doubt that this home made spring compressor is safe for it's intended use. If it were made with home center threaded rod, I would holding my computer at arms length for fear of getting hit by the spring!

vstech · #8 09-04-2012, 01:14 PM

I was with you right up until I read you welded the nut onto the threaded rod... now you have altered the strength of the bolt.
also, the plate to washer fitment is iffy... ANNND the plate itself gets it's strength from the metal around it, so mounting from the center is weak and prone to pull out...putting a steel plate 1/4" thick behind the entire mount would strengthen it, but it would then be too thick to fit between the coils...

gsxr · #9 09-04-2012, 02:38 PM

I'd recommend wearing a full-face motorcycle helmet while that system is in use...

auspumpen · #10 09-04-2012, 02:43 PM

...and full leathers with armor plating and the like. I love DIY ingenuity, but...this is sketch

Diesel911 · #11 09-04-2012, 03:14 PM

Homemade Spring Compressor
Homemade Spring Compressor

Below is a pic of mine that pulls the Spring upwards into the Spring Perch. You need to use a Crow Foot and a bunch of extensions to turn the Nut as there is no room under the Hood for a combination Wrench.

You can also decompress the Spring and remove it but it is a lot of cranking.

Admiral Ahani · #12 09-04-2012, 05:06 PM

The spring perches are not just flat sheet metal. The curved side profile adds a lot of strength to them versus if they were flat. And yes, these are the parts that are attached to the LCA, and hold the bottom end of the spring in the car.

The washers I'm using are very thick and broad. A larger thicker washer could be used if you're really worried about it, but what I used worked well.

I do wear face protection when using any spring compressor, especially one that's never been tested before!

The tool did not deform or bend in any place, even when fully compressed. I once used a harbor freight macpherson strut spring compressor on a small 120 lb/in coilover spring, and it started to deform when approaching full compression, so I knew to watch out. The tool I made held up well.

To really test it, when I was doing the 2nd spring, I decided to compress it as much as I could. The nut started to become too hard to turn, and the spring was more compressed than in the pic above but still not compressed all the way. I left it like that over night. The tool didn't deform or anything.

I forgot to mention - I clean and oil the threads every time I use it. Oiling the washers helps a lot too.

Diesel911 - that's a cool tool too. So the piece of stock goes at the lower end of the spring, and the larger washer at the other end jams against the body in the engine bay? That's a nice trick - just leave the spring in the car while you do the work. In my case I was cutting a little bit off my springs so I had to take them out. My only suggestion would be to add a little lip at the edges of the bar stock.

Admiral Ahani · #13 09-04-2012, 05:20 PM

The tensile strength of the rod is 60,000 lbs. My springs are the p/n 41 which has a stiffness 310 lb/in. I didn't measure how much I compressed them, but I'd guess around 5 inches from their full length (which is like 17.7"). Even if they were compressed by an absurd 10 inches, that's still only 3100 lb of force on the threaded rod.

Certainly the rod/nuts are not the weak part of the tool. The perches would probably yield first, and they worked perfectly. I mean, they're designed by MB, who (used to) over-engineer things, to hold the springs.

Peterac · #14 09-04-2012, 07:06 PM

Hello Admiral,

This is great, thankyou for sharing your creativity. Can I ask, how did you cut the plate?

Regards

Peter<><

Diesel911 · #15 09-04-2012, 08:04 PM

Quote:

Originally Posted by Admiral Ahani

The spring perches are not just flat sheet metal. The curved side profile adds a lot of strength to them versus if they were flat. And yes, these are the parts that are attached to the LCA, and hold the bottom end of the spring in the car.

The washers I'm using are very thick and broad. A larger thicker washer could be used if you're really worried about it, but what I used worked well.

I do wear face protection when using any spring compressor, especially one that's never been tested before!

The tool did not deform or bend in any place, even when fully compressed. I once used a harbor freight macpherson strut spring compressor on a small 120 lb/in coilover spring, and it started to deform when approaching full compression, so I knew to watch out. The tool I made held up well.

To really test it, when I was doing the 2nd spring, I decided to compress it as much as I could. The nut started to become too hard to turn, and the spring was more compressed than in the pic above but still not compressed all the way. I left it like that over night. The tool didn't deform or anything.

I forgot to mention - I clean and oil the threads every time I use it. Oiling the washers helps a lot too.

Diesel911 - that's a cool tool too. So the piece of stock goes at the lower end of the spring, and the larger washer at the other end jams against the body in the engine bay? That's a nice trick - just leave the spring in the car while you do the work. In my case I was cutting a little bit off my springs so I had to take them out. My only suggestion would be to add a little lip at the edges of the bar stock.

On the Bar Stock I just made it so that it is one inch longer on each side than it is needed; that way there is no way it can slip out. You cannot tell but the Bar Stock has an oval hole in the center so that it can tilt a little.

I think I got the idea from one of our Members who also did the same.
But, evidentaly Mercedes also had a Tool that did the same and it shows up in some of the Manuals.

The big dissadvantage of the Tool is that you cannot close your Hood; or of you forget it is there you could dent your Hood.
You can also only do one side at a time.
At the time I was desparate to make something that would work.

Later I made the Hooked Tool in the right picture so that it could be used on something else besides a Mercedes.