(Topic ID: 292442)

Warped bakelite/ plastic combination needs flattening...

By Robo1

5 months ago



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  • 7 posts
  • 4 Pinsiders participating
  • Latest reply 5 months ago by NC_Pin
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    #1 5 months ago

    I just had returned to me a Gottlieb Queen of Diamonds that a year ago was just perfect. I loaned it to a museum and they had left it on so long a that the spinning bakelite disc in the head warped and scraped the backglass.... Totally disappointed.

    I need to flatten it out but because its a mix of the two materials and has snow shoes on it i can't just press it between glass. I need to bake it until its warm and try to flatten it with separate pieces of glass or books.....

    What temperature should I heat it to, and for how long?

    Any help would be great........

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    #2 5 months ago

    wow, it must have been left on for a very, very long time.

    Is it true bakelite? If so, man.... that will be tough. I have never attempted it, but my best guess would be to do some sort of creep flattening (thermally activated glide). This would require constant heat probably in the 150F range and a constant load of pressure. I am a material scientist... and this is my best guess. Honestly, if you can't source a new part you are probably going to want to post the question on a material science message board. Bakelite is easy to make, shape, and polish... but it can be a nightmare after the fact.

    #3 5 months ago

    Exact same problem from a couple of years ago with some fixes you might try:
    https://pinside.com/pinball/forum/topic/how-do-i-flatten-this-bakelite-disc

    #4 5 months ago
    Quoted from NC_Pin:

    wow, it must have been left on for a very, very long time.
    Is it true bakelite? If so, man.... that will be tough. I have never attempted it, but my best guess would be to do some sort of creep flattening (thermally activated glide). This would require constant heat probably in the 150F range and a constant load of pressure. I am a material scientist... and this is my best guess. Honestly, if you can't source a new part you are probably going to want to post the question on a material science message board. Bakelite is easy to make, shape, and polish... but it can be a nightmare after the fact.

    I said constant load of pressure... that isn't quite true. You would need to slowly increase the pressure over days) until you get it flat. At that point you would need to hold it at constant pressure for an extended amount of time (weeks). BTW... I mention 150F... that is an absolute guess... that is half the melting point of Bakelite... but I would do much more research on the temp to use.

    #5 5 months ago

    Steam! it worked quite well..... I will know more when its reinstalled but it is certainly 70% flatter. I had a pot that was just a tad shy of the diameter of the disc. I put the disc with the concave side down and I placed on it a plastic ring that was tall enough to be higher than the snow shoes, on top of that ring i placed a cast iron pot........and steamed it for about 5 minutes. I could actually see the disc flatten out. I removed the water and put it back the same way as when it was steaming.....let it cool and it really worked well. It seems that it isn't a true bakelite but more a composite material.
    Great to know if future discs or score units are warped.........

    Thanks for the interest and comments. I just ordered a repro from Shay for a gazillion bucks but at least the game will be saved!

    #6 5 months ago

    Ive had success in the past flattening warped plastics by sticking them between two sheets of playfield glass and leaving them out in the sun on the backyard table for a couple hours.

    #7 5 months ago

    Glad you found something that would work!! I am curious if it really was Bakelite. I’d be surprised if just steam would work. Regardless, I am happy that you found a solution!!

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