Nylatron Bushing problem on a Vintage Thorens Turntable 1

[heyraz]

Greetings Guys,
I'm not an engineer by trade, I'm a pharmacist.
I've been having a problem with the Nylatron Bushings on my turntable (Thorens TD124 early version) that I haven't been able to resolve using the usual DIY and Audio forums. They don't seem to have the expertise, I thought it might be better to talk with a materials engineer.

The problem is that after one hour of spinning, the nylatron bushings begin to expand, decreasing the I.D. and eventually seize the platter spindle. I'm aware H2O will swell nylatron, but I don't think that's the main issue as the spindle continues to turn for nearly two minutes after shutdown when cold. Certainly there is friction generating heat, and I'm aware of Nylatron's great coefficient of expansion when heated.
I contacted a company that specializes in repairing Turntables with this issue (those fitted with Nylatron Bushings) and their recommendation was to replace them with Sintered Bronze bushings. Before I go that route I'd like to explore other options.
The company I contacted suggested that additives in conventional or detergent motor oils have clogged the Nylatron "pores" and ruined the self lubricating properties of this material. I myself have tried Mobil One 0-30 Synthetic oil and La-Co Turbine Oil with no improvement. Currently the bushings are soaking in "Sea Foam", a product purported to dissolve and remove contaminants. After a few days of soaking, I will dry the bushings for 24 to 48 hours in a low humidity warm environment. I will then store the bushings in a sealed container filled with desiccant packets (the kind we use in pharmacy).
On the assumption that I have removed as much water as I possibly can, I will re-install the bushing assembly and use a pure Silicone lubricant (designed for firearm use) and hope for the best.

My questions to you is are these bushings shot and am I wasting time and money? Assuming they have swelled because of hydration and/or contamination, is the procedure outlined above sufficient to return them to their original I.D.?
Any other suggestions would be appreciated.

Thanks.

Rich

 

[MikeHalloran]

SeaFoam is a pretty strong solvent, really good for cleaning metal carburetor parts while they're still in the carburetor, etc. I don't think the nylon in Nylatron is going to like it much.

Speaking of nylon, desiccating it has to be a waste of time, because it's hygroscopic.
Molders dry the pellets before melting, then boil the freshly molded products in water for half an hour to drive their moisture content toward equilibrium with the atmosphere. That also tends to stabilize their dimensions.

I don't think there are intentional pores in Nylatron; it's typically filled with MoS2 particles.
Molybdenum disulphide is great stuff to bake onto a sliding surface that has to move exactly once, even years hence, even in outer space. With continuous movement, it can act as an abrasive. Your spindle may be super-polished, or it may be coated with a thin film of Nylatron that's been mechanically plated onto it.

Clean the spindle with the SeaFoam, then burnish it with a lint-free cloth.
Soak the bushings in the silicone gun oil, and try it that way for a while.


If a plurality of bushings is to be installed in a housing of some sort, normal practice is to install Oilite bushings that are slightly undersize, then line-ream them to size with a long sharp reamer to the proper size (assuming you know it), always turning in the cutting direction, in one pass.







Mike Halloran
Pembroke Pines, FL, USA

 

[heyraz]

Mike,
Thanks for your reply.
I misquoted when I suggested that detergents in motor oil clogged the Nylatron's pores. I believe I read sintered bronze can become clogged, not nylatron and confused the two. More accurately, it was suggested that acids are present in detergent motor oils which damage nylatron causing expansion. It was elsewhere I read that humidity affects Nylatron causing some expansion, albeit not as much as thermal expansion.
The Nylatron bushings have been soaking in Sea Foam for 24 hours. I suppose I should remove them now, wipe them down and allow them to dry. I will also do as you suggested and clean the spindle with Sea Foam.
If the situation does not improve upon reassembly, I will more than likely send the spindle/bushing assembly out for professional service.

One last thing..what lubricant would you prefer to use in this situation (nylatron against steel), turbine oil or Silicone Gun oil?
Thanks again.
Rich

 

[MikeHalloran]

I would probably use the Remington Gun Oil you can buy at Walmart. ;-)


Mike Halloran
Pembroke Pines, FL, USA

 

[heyraz]

Good suggestion, it contains teflon.
But I live in New Jersey, and the local Walmart doesn't stock gun oil. Kind of a touchy subject up here.
Thanks again.

 

[MikeHalloran]

I'm pretty sure the Walmart in Levittown PA stocks gun stuff.
Or try Walmart.com .


Mike Halloran
Pembroke Pines, FL, USA

 

[heyraz]

Amazon.com doesn't take sides when it comes to the second amendment. I'll have Remington Gun Oil in 2 days.