Shock-absorber and spring change-over

[rfs1957]

Can any one suggest a clever way of removing-refitting the rear springs when changing dampers, or refer me to an earlier post that I might have missed ?

Have the kit to make more or less anything but if I can avoid re-inventing the wheel ............

[MarekH]

Dear Anon,

If you don't have spring compressors, then a couple of old brake discs can be fitted over the shock and wound in together to compress the spring using some long bolts.

kind regards
Marek

[rfs1957]

Thanks Marek,

No brake discs but plenty of steel sections, a MIG, and a press, so no excuses !

Rory

PS : Anon ? Hadn't realised, just added my name to the signature.

[christopher storey]

No,no,no !! This is one of the most dangerous jobs on a car . The amount of energy stored in a spring is enormous and these things can kill all too easily . Brake discs might just about be alright, although I would not bank on it, particularly since high tensile bolts of an appropriate length will cost you almost as much as a proper tool , but old steel sections etc are potentially lethal . This is why the tools tend to be steel forgings . You should be able to hire the proper tool from the JEC or they can be bought from most decent factors

PS Just looked on the JEC site - members can hire the IRS spring tool for ?10 for a week, although whether they can send it to France is perhaps more questionable

[rfs1957]

Thanks Christopher, your concern much appreciated.

Can somebody tell me what the compressor travel needs to be ?

ie free-length as against extended-length of the spring ?

[e-bygum]

Can any one suggest a clever way of removing-refitting the rear springs when changing dampers, or refer me to an earlier post that I might have missed ?

Have the kit to make more or less anything but if I can avoid re-inventing the wheel ............

Have a look at http://www.xketype.com/e107_plugins/con ... content.43 you might find it useful.

[Durango2k]

I went the brake disc route, and I can say I used ordinary M10 threaded material (1 mtre 6 Euros).

Problem is that on one of the bolts (I simply cut the 1 mtre in 2 halves) I had the nut to loose it?s thread 2 times

So, I am not sure if I should recommend this. I would do it again, as the second side hold up, and I can see no sudden "explosion", but yet, do NOT have your head above the upper disc.

And you will almost surely damage the nice shiny powder coating on the springs. I did.

It?s a cheap bodgy way yet it works...

Carsten

[abowie]

Pay the local garage 20 quid to change them over.

[PeterCrespin]

I've got the correct compressor and collets (plus collets for lots of other jobs) so have no excuse but it was not always thus.

Using old discs with four lengths of M10 stud is fine IMHO but don't sue me. Assuming springs are standard OD and fit the hole correctly (check) and you take care with gradually tightening all 4 four studs in rotation (NOT 2! ) then you aren't going to go very far wrong if you keep out of the line of fire. Use a back-up nut each end of each stud if you're nervous I suppose.

If you're ham-fisted don't try it, but if you're a fully paid-up member of Homo Sapiens then statistically you have the brain power to come out of it alive. The rest are probably due a Darwin Award in some other sphere eventually.

[Durango2k]

With 4 bolts it?ll take ages, Mr. Crespin, that is.... if you have 4 of them to change...

Carsten

[christopher storey]

With 4 bolts it?ll take ages,

Carsten

You are a long time dead !

[rfs1957]

More people probably have access to a hydraulic press than a spring compressor, and most of the latter are anyway aimed at springs of far larger diameter than the Jag's.



This method is fast, controllable, and 100% safe - the strap is just there out of habit and to show we're taking it seriously.

It does however require you to make a simple cage or frame from steel off-cuts, these here are bits of 'T' and Flats of 3 or 4mm thickness, MIGged together to form a square recess.



This fits snugly around the spring diameter and is then stuck in the 4-jaw and bored out to 69mm to leave clearance for the the collets.



Ideally you would also MIG a U-shape section to the top to take the press-yoke, but the efforts encountered are so low and so controllable that a couple of equal-length 2"x3" off-cuts keeps the whole lot squat and square.



Setting up the press height and piston travel requires a bit of juggling and I had meant to note down the fully-compressed spring length (for collet removal) and the fully extended length (for damper change-over) to make life easier for others going down the same route ........... then lost my figures.

Sure beats threaded bar and discs !

[Dave K]

I have done this a good few times on various cars. I use 2 x 12" approx lengths of 16mm threaded bar, 2 x 16mm nuts tacked together and a 6mm piece of flat bar with a bend on the top slightly offset to hook over the spring.
At one end of the threaded bar weld a 16mm nut to use for winding the hooks together to compress the spring. It doesn't have to madly compressed just enough to pop the collets out then unwind until the tension is off the spring.
You need to have 4 of the hooks welded to the nuts that then screw over the threaded bar. I made a few of these at work and keep losing them.

Of course you have to be careful like any job but it's not that difficult just use common sense.

A while back I was stripping off front axles from XJ's for use as a front suspension upgrade for the E-Types. Didn't bother with any special tools for that job, 3lb hammer, 12" cold chisel, 4 hits on the top nut to split it, bang the top with a hammer to release the spring tension and bingo. Some did go with a right bang but I did 40 pairs and still have all my limbs etc in their right place. I then had to split the bottom nut using a chisel as well.

Dave

[Mike L]

Peter
I am inclined to go your route. I did watch the U-tube video, impressive. I cannot obtain any old discs, however since I have a milling machine and a lathe I can make up a pair.
Any reccomendations would be most welcome
Mikw L

[christopher storey]

I'll repeat the recommendation I made at the start of this thread : DON'T DO IT . If ever confirmation was needed, it was given by one of the previous posters who tried one of the Heath Robinson methods shown and stripped the threads of the studs or bolts he used . These methods are a catastrophe waiting to happen . By way of example , just imagine one of those blocks of wood splintering, or just slipping out of place

[PeterCrespin]

Peter
I am inclined to go your route. I did watch the U-tube video, impressive. I cannot obtain any old discs, however since I have a milling machine and a lathe I can make up a pair.
Any reccomendations would be most welcome
Mikw L

Are you responding to me? Recommendations for what?

If you are maching parts up you can put a 'safety recess' in each plate to stop the end of the spring slipping sidewways. Take care, one turn at a time, evenly, with the spring tied to a stud or two if nervous. Every time you tighten something look to see the spring is not bulging asymmetrically.

Chris is correct, I don't ? recommend people do what I do when it's a bit naughty, but offer my experience in case it is useful. Plus of course i wouldn't do it myself if I thought the risks were excessive or unmanageable. Four solid studs is enough to spead the load and you only need to compress the spring slightly to get the collets out. Releasing evenly is just as important, if not more so, than tightening of course.

Pete

[rfs1957]

It would be discouraging if recent members with low posting numbers asking apparently naive questions on the E-Type forum were automatically assumed to be daft.

They might potentially be mechanical engineers with university qualifications and 30+ years of self-employed hands-on power-sports engineering experience, including fabrication and machine-shop work, vehicle restoration, and with electrical and civil engineering professional asides, yet possessed with a conviction that the more they know, the more they could still be helped by ? and help ? others.



Regarding the use of timber off-cuts for spring compression, at 15 tons on the end-grain (and not a squeak) of one of the bits used in my original pictures I gave up since the press started to leak, hence the picture at 10.

Do the maths.

[Woolfi]

If this method is going wrong in one of 1000 times, it is much to dangerous to do. You feel shure, but this method in NOT shure 100%. This 0,1% can hurt somebody very serious or kill him.
If a not so skilled / intelligent worker is copying this or other do-it-yourself method of spring compression, the risk to fail is much higher than 0,1%.
You can buy a pair of spring compressors in ebay for 7 (!) pound. Ebay is full if these tools.
Regards Wolfgang Gatza

[MarekH]

Dear Rory,

I think your argument is very poor and proves quite succinctly why using a press in this manner is dangerous. The person who is going to copy the Heath-Robinson arrangement for compressing springs may not have 30 years of hands-on experience, may not understand end grain, or any technical terms or even use strapping, half welded flanges and what ever is to hand to secure such a load safely.

The advice offered has to be so far within the margin of error and safety that any idiot can follow it badly and still be safe. This is far from proven with a few jpegs of blocks of wood and a ten ton press held by straps.

Even with something like the brake disc method, it is simple to fit a second set of nuts on the bolts to ensure that the extended spring length can never exceed a limit whereby a sudden release makes it become dangerous. A quick look at the proper tool for the job shows how coarse the threads are also. It thus becomes easy to design a sensible way of achieving the same goal, were a set of spring compressors not available. I see no such inbuilt safety features whatsoever in the hydaulic press method.

Such a Heath-Robinson approach has the potential to be downright dangerous. If you don't feel that's fair comment, please offer a comprehensive insurance or warranty against harm to A N Other if they are following this method.

The best approach is to use or make a proper custom tool for the job.

kind regards
Marek

[PeterCrespin]

Dear Rory,

I think your argument is very poor and proves quite succinctly why using a press in this manner is dangerous.

The best approach is to use or make a proper custom tool for the job.

Err, isn't that exactly what Rory has done? The only bit I took issue with is his initial statement about most people having access to a hydraulic press, or some such comment. The chief significant deviation from the twin disc method (at first glance) seems to be the means of compressing being hydraulic. The collars appear to be very well made and the timber dimensions more than adequate, not least given that timber is by some criteria stronger than steel- which I offer merely as a throwaway remark to balance the possible supposition that chunks of wood are somehow inherently weak.

I agree it behoves us to offer any advice with suitable caveats, but we're all grown adults and you and I are right out on a limb when it comes to risk-taking since we ride very fast motorcycles. Pots, kettles, etc. My reaction to Rory's method and photos was along the lines of 'Sheesh, that's a lot of fabricating [AKA "..making a proper custom tool.."] compared to threading four lengths of studding through old discs.' It was not one of 'OMG what a shoddy contraption'. The loose strapping looks sloppy but it's OK like that. The objective is not to hold anything firmly but to restrain any excessive sudden movement or uncontrolled trajectory.

I'm not especially advocating his device, which few here have the equipment or skill to replicate, but I wouldn't disdain it either. The twin disc technique is as close to replicating the factory special tool as you can easily get. Rory's job is looks like a lot more work but what he actually made when you look closely, seems perfectly adequate? I certainly wouldn't put my own dabbling up against his CV!

Pete