Rocker Stands

[Pascal Giai]

There is Magnesium and Aluminum rocker stands for late engines. Aluminum is bright silver, magnesium is darker.
Do they have different numbers embossed ? If yes, witch numbers for witch stand ?
Do we have to avoid magnesium stands at all cost ???

Thank you !

Pascal Giai

[Ron LaDow]

Look at the engine case; that's aluminum. If they are darker than that, and notably light in weight, they are mag and are not to be used.
Bruce Anderson gave talk at one of Bob Campbell's Ventura events years ago; he said Mag belongs back in the ground from whence it came or on race cars; NOWHERE else. I have to agree.

[Craig Richter]

Me too.

[Jim Breazeale]

Look at the engine case; that's aluminum. If they are darker than that, and notably light in weight, they are mag and are not to be used.
Bruce Anderson gave talk at one of Bob Campbell's Ventura events years ago; he said Mag belongs back in the ground from whence it came or on race cars; NOWHERE else. I have to agree.

Here is a comparison. I don't think I have to say which is which.

Regards

Jim

[Pascal Giai]

Jim,
could you tell us the part number for each stand.

Thank you !

[Dennis ODonnell]

Ron, Mg is used extensively in aircraft for its light weight as you know. It functions well if it's protected from corrosion and torque specs for studs and bolts are strictly observed. What are the consequences of using it as a rocker stand that condemn it, lack of strength in tension & shear?

[Ron LaDow]

Ron, Mg is used extensively in aircraft for its light weight as you know. It functions well if it's protected from corrosion and torque specs for studs and bolts are strictly observed. What are the consequences of using it as a rocker stand that condemn it, lack of strength in tension & shear?

AFAIK, the studs (and the female threads) are identical for the Mg and Al stands; the Al stands are subject to thread failure from over-torquing the rocker shafts, so its not surprising the Mg units were even more susceptible.
But it's also kind of a reverse question: WIH did the factory spec Mg? Was a 5oz. weight saving seen as so valuable as to use the stuff? (it ain't easy or cheap to cast).
Is it used genrally in GA aircraft?

[Vic Skirmants]

The magnesium stands have the studs screwed in, as one would expect. The aluminum ones seem to have them cast in place; don't try to unscrew them! It is possible the earliest aluminum stands had screw-in studs, but I haven't seen any. Of course the only way I can see them is when the stand gets broken. I'm under the impression that the magnesium stands were a S-90 item; please correct me if I'm wrong.

[Dick Weiss]

I agree for the S90, Vic,

However, I never tried or had to replace any studs in the stands, but studs being 'cast in'?
That would really take some tooling to do that!

Dick

[Dennis ODonnell]

Were the 356 studs in the Al stand an interference fit rather than cast in; stand heated, studs chilled for insertion? It's the kind of small-shop specialty work the German economy's founded on.

Mg kept weight to a minimum in piston a/c engines and other large castings like gear legs. This old Continental's 470cu in vs. a 356's ~100 yet only weighs 1/3 more. The accessory case (rt of the red line) is cast Mg, mounting surfaces for starter, generator, mags, vacuum pump etc are machined. It was chromated to prevent corrosion. Al replaced most uses so weight has increased requiring more power for the same speed.

[Jim Breazeale]

Here are the 3 casting numbers I found. I couldn't for the life of my find a "02". I looked through about 50 of them. The "01" is a mag one the the "03" and "OR" are aluminum. I can only assume the the "OR" are from 912s.

Ciao

Jim

[Pascal Giai]

This is what I was looking for, thank you so much !

Pascal Giai

[Craig Richter]

I never kept any records on this kind of stuff, but as I remember (a questionable thing these days according to my wife), the first '60 S90's came with the .01 magnesium rocker stands. '60-on N, S, SC and 912 all came with alu stands. The last S90's (63?) even changed to the alu stands, presumably because P saw too many mag stand failures . My b-in-law's '60 S90 has over the years broken both sides, leaving the driver stranded waiting for the flatbed (twice), the only stranding failures in her whole life. That's why I have often cautioned against using the mag stands.

[Vic Skirmants]

Normals still used the old steel stands.

[Dick Weiss]

I rebuild steel stands, too--have several available + good shafts and rockers.

Dick