There has been a little discussion in another thread about an IRS under a 1200 coupe. This is not really a project to be taken on lightly, or by the faint of heart, bit i think that the real issue is ride quality, so here are a few observations, & your constructive input is encouraged.

Leaf spring cars came new, with interleaf rubbing blocks. These were intended to reduce the friction between the end of the spring leaves & the leaf above it.

After 30 years, these rubbing blocks have all worn away & very few people have replaced them. The end result of this is that the dry leaves, complete with a little rust between them, have a great resistance to movement between the leaves. This is called STICTION.

If your rubbing blocks have completely worn away, then give this a try. As an experiment, jack up the body your leaf sprung car so as to allow the suspension to sag. Prize the leaves apart a little & spray in some light lubricant. Perhaps some 20 weight oil.

Go for a test drive. Do NOT go racing just yet as you could find that ride quality has dramaticly changed & your shock absorbers may be much more worn than you thought.
If ride softness has improved, you have discovered one reason for harshness.

THE FIX?
You could buy a set of the rubbing blocks & replace them. I think that major suspension shops have universal types.
Another method is to remove the springs & dismantle them. Then go over the leaves with a belt sander to remove the rust & smooth out the roughness. Abrade only along the spring, don't do it across the leaves. If you want to lower the suspension, now's the time to have the springs reset.

Here's the hard part.
A popular trick at one time was to use teflon strips between the leaves, but urethane might be just as good & i think, more available. Check with some of the urethane bush manufacturers for availability. Once you have painted the spring leaves, assemble the spring with these thin, full length strips.
If you can get some suitable sized shrink down tubing, then use this over the spring, if not, then carefully wrap the spring with electrical tape. This is done to keep out the abrasive crud from the road, & to prevent the teflon/urethane from migrating out from the side of the spring leaves.

Reassemble into car using new urethane suspension bushes. If shocks are in the slightest bit suspect, replace with uprated types.

It all sounds like a lot of work, but it's a lot less work than engineering an IFS into a car that was never intended to have one. Its a job that most of us can do in a home workshop & the ride quality will be much less harsh. It may even be just what you were looking for.
It will cost a lot less too.

The full deal on the leaf springs makes them behave much more like coil springs, which have no stiction whatsoever, & this is the reason for the uprated shocks.

Try the oiled springs test & see how it feels.

OK, the forum is now open for constructive commentary

Polypropelyne might be good for this use (and less expensive than teflon).

dodgeman.. that makes a lotta sense... i woulda never thought of that with the STICTION.

I sold a set of "rebuilt" reverse eyed springs that I made up some nylon blocks for between the leaves. I made them up on the lathe from a bar of nylon.

I don't know what Mikali did with these after I sold them to him, but they were a great set of leaf springs.

Chris

There is nothing inherently wrong with the simple, well tried, & thoroughly proven, leaf spring "design." They locate the axle both longditudinally, & transversly, without any added linkages, & they provide the springing medium, all in one crudely engineered, low cost, package.
It aint rocket science, but in a car who's real selling point was it's low low price, this basic system has a lot to offer.

All we need to do with leaf springs, is make sure that we get the best from them.

Anyone have a source for the interleaf, friction reducing, material?

Thanks Chris, Once again you have shared a pearl of wisdom to further enhance our datsun experience.

Excellent post Dodgeman, the points you make are doubly important to 1000 owners, with your kooky traverse front leaves.

I agree that getting the existing suspension in the 1200 (or 1000) working at its optimum makes more sense than starting from scratch.
There are so many variables that may not be apparent until you assemble and test a system under load. Anything is possible however, and I'd love to be proven wrong.

James.

Here is a source.

Most 4wd places sell this kind of stuff.

I will try and find another link to this kind of thing, I remember someone sold a circle one for the end of each leaf which involved drilling a locating hole to keep the product located on its own.

Thanks for the link.
The text with the lining material says that this works really well with chrome springs & i can vouch for that, as the chrome is an ideal surface, but is not legal in some states as the chrome plating process induces a measure of "Hydrogen embritlement" into the surface of the plated steel. Since the main leaf locates the axle, a broken one can spoil your afternoon.

Now, it's unlikly that there would be many of us that would chrome their springs to improve ride quality, but for those that are thinking of it, check with your rego Nazi's first.

Jempson
I dunno about "kooky" but the use of a transverse spring in an independant front suspension is certainly uncommon, although i think Peugeot used this concept in a model or two. As long as the spring is nice & pliable, the ride will be good.
Datsuns use of the leaf spring in the front overcame a space limitation problem, where a short coil spring would have needed to be too stiff.

As the poster of the IRS thread this is all very interesting stuff and exactly what i was looking for as far as advice is concerned.
I just bought a can of high pressure adhesive lubricant on the weekend (a Wurths product can't remember the name) It's supposed to be used for hinges etc and i reckon that would work really well as a tester for this problem.

By the way i also have changed my mind on the IRS idea. It was simply that and the comments and advice i've recieved have convinced me to go the twin link and panhard rod route for the time being.

The bloke i work with on the stuff thats past my skills also pointed out that an IRS setup was pretty heavy which would negate one of the 1200 (and 1000!) most endearing features; it's nimbleness due to it's light weight.
They're damn go-karts! Heaps of fun nipping through the traffic!

This Web site is a gold mine of ideas and advice! Can't get enough.