[Glitch]

It is well known that the original belts in Beocords turn into goo when they get old.

Will the replacement belts from beoparts-shop.com have the same issue or are they made of an improved rubber formulation?

Glitch

 

[yachadm]

I have been buying belts (and other parts) from Martin Olsen (Dillen) for over 20 years.

One BeoCord which I still have, had its belts replaced in 2003. The machine still functions perfectly.

I can’t forecast what the belts would be like in another 20 years, but so far, I’m satisfied with almost 20 years belt-life confirmed on this machine.

I do know that as long as the machine is used every now and then, causing the belts to expand and contract, that reduces the chances of “gooing”.

The other bonus is that Martin’s belts have the correct tension, which does not cause destruction of the fragile sintered brass motor bearings in all these vintage B&O machines. Other belts sold on “e-ay” have a nasty reputation for destroying motors – very expensive repair, if at all possible.

[sonavor]

All rubber belts will eventually wear out. How quickly is determined by their use and operating environment. The most important thing is to have faithful reproductions of the original belts which is what Martin produces.

-sonavor

[Glitch]

I’m certainly not questioning the suitability or performance of the beoparts-shop belts. My assumption is that they are the highest quality part that is available.

My question was related to a design choice. Material science has made great progress in the decades between when the belts were originally designed and now. The new belts could have been specified using the original rubber formulation or something newer. I wouldn’t consider either choice to be “wrong”. I’m just curious about which choice was made.

Glitch

 

[Glitch]

yachadm wrote:

I do know that as long as the machine is used every now and then, causing the belts to expand and contract, that reduces the chances of “gooing”.

I’d like to learn more about this. Can you provide any further details about why this would be the case?

I’ve always assumed that the belts degrade due to a process (like oxidation) that either causes the polymers to break down (into “goo”) or form a “new/modified” substance that is less elastic (cracked, brittle belts).

My motivation for having a better understanding of this is to help with a long term preservation plan for the equipment. For example, if it is inevitable that belts will turn to “goo”, it might be prudent to remove them before placing the equipment into storage. An analogy would be removing the alkaline batteries from a vintage toy, draining the gas from an antique car that won’t be driven for a while (or the swapping out the foam inside certain active speakers). I recently pulled apart a vintage computer where the CMOS battery leaked and corroded the nearby circuit board traces into green dust. Had I foreseen this, I’d still have a working computer.

Glitch

 

[sonavor]

The transformation into the black goo is an interesting one. I believe that happens due to the way the Beocord unit was stored. I think a belt will wear to the point of requiring replacement during regular use inside a normal, home environment.

I also believe the belts that deteriorated into goo happened because so many owners stopped using cassette decks (I know I did for quite a while) and put them into storage like attics, basements and storage sheds. Those environments resulted in the deterioration of the rubber. That is just my guess of course but I don’t think a belt will deteriorate to that extent if the Beocord remains in use and is maintained (service checks).

-sonavor

[chartz]

Not so sure John. I’ve recently done a VCR that had always sat under the TV set, until one day it didn’t work. The four belts had turned into goo, unbelievable. After hours of cleaning and belt replacement the VCR worked perfectly again.

[Glitch]

Poor storage conditions might accelerate the degradation of the belts, but I don’t think that it is the primary cause of goo-ification. I bought my Beocord new and it has spent its entire life in a climate controlled, living space. Regardless, I ended up with goo.

This issue is not unique to B&O. I’ve read similar stories for many other brands of equipment. The common cause has to be in the base material or in the manufacturing process of the belt. Who knows, maybe all of the goo-belts come from the same plant.

I’m hoping that they have made progress on the longevity of the belts. I believe that they have improved the formulation for other issue prone parts like foam speaker surrounds. It would be a real shame if the plastics industry reserved the “forever materials” strictly for disposable items like water bottles and soda straws. (yes, I know that they are different classes of plastics)

Glitch

 

[Glitch]

I did a bit more research and found that the correct term for the phenomena is “rubber reversion”. However, I think the term “goo-ification” is more fun ;-).

There seem to be many theories about what is going on. Many of them are based on the supposition that the polymer stabilizing additives migrate out of the rubber. I’m having a hard time conceptualizing how a working the rubber would slow the process versus keeping it in a state of stasis. There is a group of vintage camera enthusiasts that swear by the “use it or lose it” theory when it comes to rubber parts on cameras. Perhaps the rubber should be considered a viscous mixture and working it keeps everything mixed-up appropriately?

Regardless, I’ve already gone deeper down this rabbit hole than I intended. I’m still hoping that someone can shed some light on the original question.

Glitch

[sonavor]

I think the use it or lose theory fits here.

Thanks for digging into the problem more.

-sonavor

[Glitch]

The camera guys seemed to be concerned about stickiness versus degrading into goo. I’m not sure that any of them are able draw a meaningful conclusion without an actual comparison test. For example, they would have to have two lenses that were manufactured at the same time, then use one and store the other. This would be the only way that they could “know” that the difference in stickiness was due to handling. However, they still could come the wrong conclusion. Maybe the any difference in stickiness is due to incrementally removing the sticky substance on the handled lens versus it building up on the stored lens. Both items could have actually degraded the same amount, but “stickiness” is simply a poor metric to use for judging degradation.

Similarly, to make any real judgements about belt life, one would need to have two decks with the same parts installed. One deck would need to be used and the other not. A meaningful conclusion could be made if the belts on one of the decks held up better than the ones on the other. Otherwise, I don’t see how any definitive statements can be made.

The closest I can come to a meaningful experiment is with the rubberized coating on a computer mouse. Many years ago, I set up two office workstations, one for me and another for my wife. They both had the same keyboard, mouse and monitor (all purchased at the same time). I use my workstation daily, my wife uses hers very occasionally. The rubber coating on my mouse turned into a sticky mess, the coating on my wife’s mouse turned into a hard substance. Neither is anything like when they were new. I think I can make a meaningful statement about the coating on this particular model of mouse. I don’t think extrapolating this experience to anything else is necessarily meaningful.

One commonly believed theory (backed by science) is that every rubber part degrades somehow. The degradation clock starts when it is removed from the mold. The nominal speed of degradation is based on the composition and process used to manufacture the part. One can speed up or slow down the clock based on the environment or usage, but the degradation is inevitable.

The more I think about this the more questions that I have… For example, how important is it to buy a freshly manufactured belt? Buying from old stock would be problematic if the belts degrade mostly from not being used. Conversely, it wouldn’t be so much of a problem if the belts degrade mostly from usage.

Glitch

 

[sonavor]

My suggestion for anyone collecting these vintage Beocord units is to begin the restoration with new belts from Beoparts, use the restored Beocord decks, then do a service check from time to time. That will catch any belt deterioration before a real problem.
As mentioned earlier in this thread, it would be an excellent idea to remove the belts whenever the Beocord was put into storage.

On interesting thing is on the rubber wheels in the Beocord units. I don’t believe I have ever encountered any of those turning into goo. I do always replace the rubber wheels during a Beocord restoration but I haven’t ever had to clean off sticky residue left by any of those.

-sonavor

[Glitch]

sonavor wrote:

My suggestion for anyone collecting these vintage Beocord units is <snip>

I can’t argue with that suggestion. The only thing left to think about is spare parts. I would like to keep a spare set of belts and rubber wheels on hand. I am hesitant to buy them if there is a good chance that they will degrade before I have a chance to use them. I am weighing this against the possibility of the supply of replacement parts drying up.

I am thankful that there are quality parts available right now. I am also realistic about that at some point in time this will not be the case.

chartz wrote:

And yet some belts seem to last forever: I have a Thorens turntable that has a 20 year-old belt that is still perfectly operational.

Yep. That is what makes this such a difficult topic.

Glitch

 

[chartz]

And yet some belts seem to last forever: I have a Thorens turntable that has a 20 year-old belt that is still perfectly operational.

I’m pretty certain that all the belts that turned into goo came from the same Japanese factory.

Beocord open reel machines have hardened or cracked rubber.

[Ninni]

I think different models of belts are made with different kind of rubber and therefore degrade differently. The round belts for the old Beograms seem to last forever, for instance.

[Author]

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