Another Example of "White Metal" Failure

[camtechman]

Those who know about the Akai 4000 "Cam" failure and those into vintage cine projectors and the problem with the "Flywheel" on Pathe 9.5mm projectors may like to see another example of the same problem with an early Philips EL3300 cassette recorder flywheel.

As a keen collector of this genre of machine and my involvement with collecting an example of every model of each machine & each mod version they produced during their production life, this is the first example of this problem I've ever come across.

The pics clearly show the failure of the 'white metal' and it's identical to the above Akai & Pathe problems and, in addition - due to the expansion of the metal, the drive spindle falls out too!

I have several versions of the earliest EL3300 machines, including an EL3300/00 (part prototype version), an 3300/15 & the 3300A/15.

This flywheel came from another 3300A/15 I acquired recently.

Replacement presents a problem as the flywheel on these early models is heavier (120gms) than the later models (95-75gms) and has an effect on the speed & wow, as the motor speed & stabilisation is controlled by the motor's basic internal, mechanical centrifugal govenor.

At present, I'm working on making a mould that accepts molten lead to make a shaped weight and turn it down to the correct weight and then to fit & secure it into a modern version flywheel. I'll report back once I've achieved success.

P.S. Dont forget that the 30th August this year is the 50th anniversary of the first EL3300 which was launched at the Berlin Radio Show.

Further more & hopefully, my book on the History Of The Philips "Compact Cassette" Recorder will be soon finished.

Ohhh nasty, I have a lathe if you need to use it.

[ricard]

I've seen the same problem with the speed change cam on early (early 60's and earlier) Tandberg recorders (later ones were made of plastic and fail in other ways), but only on certain ones. Either the quality of the metal varied, or it depends on the environment in which it was stored.

[Nickthedentist]

Incredible, thanks for sharing.

Sad to see something that I always felt must be almost indestructible literally spontaneously falling apart.

[Radio Wrangler]

It's a zinc based alloy with all sorts of additives to make it flow well into restricted places in casting dies. They obviously make it do other things as well.

I'd turn up an aluminium piece to which I could add lead weights on the inside. Aluminium would have much less moment of inertia than the original zinc.

David

[emeritus]

There is a discussion of the causes of white metal failure, which affects some, but not all, prewar Hornby die cast products, in the book "Hornby Dublo Trains" by Michael Foster. The "Mazac 5" generally used for Zinc-based castings was 4% Al, 0.04% Mg, 1.0% Cu and 94.86% Zn. The Zn needed to have a purity of at least 99.9%, and the inclusion of only 0.1% Lead would lead to cracking and powdering. Small traces of Tin or Cadmium were just as bad.

No doubt quality control was not all it should have been in the manufacture of the defective castings: the book's author mentions having been told by retired Hornby workmen that, in pre-war days, stuff like binding wire and cigarette papers were sometimes thrown into the molten metal, which would not exactly have been beneficial.

[Studio263]

I had the same problem with one of the flywheels in a Sony TC-177SD (the first three-head cassette deck). The other flywheel, although constructed identically, was perfect. It just goes to show that the process is random.

In the case of the Sony I made a new flywheel from brass, which turns really nicely. The part is quite large so it was made in several pieces which were then pressed together, boring the centre hole "true" was the hardest part since small diameter drills tend to wander. In the end I first drilled the hole in a small sleeve of brass, then mounted it on a mandrel and turned the outside true to the centre hole. This was then pressed into the centre of the flywheel, the hole in which was now large enough to have been made with an end mill (e.g. too rigid to wander). This was all done on a Hardinge HLV-H toolroom lathe, so it was a pleasure to make.

[mark_in_manc]

Thanks for that explanation, Emeritus.

I have several acoustic gramophone soundboxes which seem to be made of a plated (peeling!) version on something similar, and one or two are unfortunately showing signs of similar distress.

I'm quite a way through building a small furnace for having a go at home sand casting. I'd not thought of making a soundbox until now, but it might be an interesting project - though perhaps a bit ambitious (rather '3D') in the early stages of getting patterns out of the sand! I'd paticularly like to save/recreate my 'semi-automatic' 'box which takes a magazine of needles for rapid-fire 78rpm action

[IanNVJ35]

Originally Posted by Studio263

I had the same problem with one of the flywheels in a Sony TC-177SD (the first three-head cassette deck). The other flywheel, although constructed identically, was perfect. It just goes to show that the process is random.

I have the same trouble with mine. May I ask was the machining difficult or do you think it would be within the scope of a normal workshop. Mine has an insert which adds to the apparent complexity.

[Radio Wrangler]

A Hardinge HLV is one of the most precise normal sized lathes made and is priced a bit out of reach of a normal home workshop (one's been on my christmas list for decades, though I'd accept a Monarch 10EE)

For accurate work with a small centre bore you really do have to drill the awkward hole first and then use it to centre everything else, and doing it in two steps as a sleeve and then a flywheel main part as Studio 263 describes is definitely the way to do it.

David

[Refugee]

I have seen this problem on a 2001 angle poise magnifier lamp from the early 1980s.