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Old 23rd Dec 2019, 5:37 pm   #1
knobtwiddler
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Default Reproduction 'Bakelite' Parts

Hi,

As many of you will know too well, there are modern replicas of Bakelite components being sold. Some of the sellers even refer to these parts as 'Bakelite'. However, when compared with the original component from decades ago, the repro part is exponentially lighter and does not have the appearance of real Bakelite. My guess would be that these replica parts are made from something akin to ABS.

Google suggests that there are still firms about who can mould Bakelite. If people have gone to the expense of making a mould to reproduce a part in ABS, why haven't they gone the whole hog and used real Bakelite? If these firms actually can mould Bakelite (assuming the chemicals aren't banned?), why aren't we seeing repro parts that are the real thing?

I am sure that I am missing something very obvious here... But firms claim they can mould it, and there is enough demand for people to tool up for ABS - so why not the real deal?

Is there much of a difference in terms of tooling requirements for Bakelite vs ABS? Do the tools wear out faster for Bakelite?

Thank you in advance!
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Old 23rd Dec 2019, 6:09 pm   #2
David G4EBT
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Default Re: Reproduction 'Bakelite' Parts

It’s not just about moulds - the materials, chemistry and processes of the production of Bakelite (’Bakelizing’) involves high temperatures and pressures which go way beyond simply pouring plastic into a mould.

If you want to know whether something is Bakelite or plastic, heat a needle and apply it to an inconspicuous part of the item. If it’s Bakelite, it won’t melt.

This link might be of interest:

https://en.m.wikipedia.org/wiki/Bakelite

I doubt that there are any radio parts such as knobs or trims for which there would be sufficient demand for any manufacturer to be interested in making them in any material - let alone Bakelite. Requests often appear on the forum for knobs for commonplace radios such as DAC90As (probably because inept would-be restorers try to lever the knobs off as that’s can’t see a grub-screw because they don’t know where to find it), and Roberts, (which lose their ‘brights and are a very poor designs which easily fractures). Such commonplace radios are of little value and a set of knobs would cost more than most would wish to pay. (3-D printed Roberts and Hacker knobs were offered for as time at c £15.00 a set of three, but didn’t seem to attract much, if any, interest).

Suppliers such as Ben Djikman in the Netherlands and others supply excellent replacement knobs, usually for radio which are collectible, of high value, and where £30 plus wouldn’t be an obstacle to restorers. The same applies to reproduction dials and replacement backs. Many profess an interest in such things, but few will pay a realistic price. Professionally made replica DAC90A back panels offered some time ago on the forum at £12.00 each, made on a CNC router remained unsold.
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Old 23rd Dec 2019, 6:19 pm   #3
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Default Re: Reproduction 'Bakelite' Parts

I'm not really worried about cosmetics/appearance; my interest is more whether these pseudo-Bakelite components would have the same high-voltage and RF properties (dielectric-constant, effect on 'Q') as the original.

In the past I've used Araldite to cast replacement-for-Bakelite parts like 1930s valve top-caps and never noticed any deleterious effects on performance.
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Old 23rd Dec 2019, 6:39 pm   #4
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Default Re: Reproduction 'Bakelite' Parts

When, in the 1970's, we needed to encapsulate an RF assembly that had a tuned circuit using a printed circuit inductor, we used a type of Araldite that had a closely-controlled dielectric constant.

Its dielectric constant was about the same as Benzine (Benzene?), and we did our pre-encapsulation tests in the lab with the assembly in a large open beaker of Benzine until a chemist friend told me about the dangers of Benzine vapour inhalation and the need to only use it in a fume chamber!
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Old 23rd Dec 2019, 6:46 pm   #5
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Default Re: Reproduction 'Bakelite' Parts

Hmmm ....

Urea-formaldehyde thermo-setting resins [i.e. largely what Bakelite + certain additional 'fillers' actually is] cast under considerable heat and pressure, presents rather different manufacturing/technological and Health & Safety challenges vis-à-vis those associated with cold chemical set or hot [thermo] plastic casting processes.
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Old 23rd Dec 2019, 7:00 pm   #6
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Default Re: Reproduction 'Bakelite' Parts

I believe the colour of Bakelite is determined predominantly by the filler and it ought to be possible to use the same fillers in a cast epoxy resin to achieve, pretty much, the same colour. The hard part might be getting the degree of surface shininess to match that of Bakelite. If the moulds were available that should be the sort of experiment which could be carried out in a garage. Silicone moulding rubber is fairly readily available https://acc-silicones.com/applications/mould-making and colleagues of mine used to use it at work if we needed to produce a cast-resin part from an existing original. A little hand-finishing was sometimes required, but if they wanted the part badly enough then they would be prepared to do that.

Cheers,

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Old 23rd Dec 2019, 11:43 pm   #7
David G4EBT
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Default Re: Reproduction 'Bakelite' Parts

I’ve made replica knobs which are a good match for original Bakelite one as shown at posts 5 & 26 at this link:

https://www.vintage-radio.net/forum/...d.php?t=142098

The knobs were to restore a Unitra Figaro bought for £5.00, and a Portadyne Princess bought for £10.00, so there would have been no ‘headroom’ to have spent much on the sets, quite apart from negating the purpose of buying them - namely, to restore them, doing whatever needed to be done. I also had to make a wave change slider knob to replace the broken Bakelite one on the ‘Figaro’, which I fashioned from Tufnol. The result was indistinguishable from the original.

It’s one thing making them for oneself, if the time, effort, skills and inclination is there, but it’s quite another to find anyone who would replicate Bakelite items on a commercial basis in low volume at a price that most hobbyists would find acceptable.

Sadly, the promise which we once thought that 3-D printers might hold for replica knobs etc has not materialised.

(The filler in brown Bakelite was mostly wood flour I believe).
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Old 24th Dec 2019, 12:26 am   #8
knobtwiddler
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Default Re: Reproduction 'Bakelite' Parts

Thank you, all - some great insights.

The paradox for me is that there is sufficient demand for repro parts to make tooling and supply items in plastic / ABS, but not go the extra inch and make Bakelite. One replica part I'm thinking of is used in new commercial designs. The company with the tool in Japan must be making enough for it to be worth their while (like many niche items, I imagine it doesn't have great volume, but ticks along solidly).
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Old 24th Dec 2019, 11:16 am   #9
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Default Re: Reproduction 'Bakelite' Parts

The original Bakelite was derived from Phenol-Formaldehyde.

The light coloured versions were based on Urea-Formaldehyde.
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Old 24th Dec 2019, 6:58 pm   #10
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Default Re: Reproduction 'Bakelite' Parts

In the 1936-7 Bulgin catalogue, the pages illustrating their range of 2-pin and 3-pin mains connectors says that they were available in Black, Walnut, and Mahogany. On the other hand, the technical data pages says they were available in "Any colour or grain of bakelite". Apart from a white 2-pin connector of the type having a body resembling a BC adaptor plug that I once saw at an exhibition, used as a telephone plug for a white stateroom telephone of the original Queen Mary, I have only ever seen Bulgin connectors in Black.
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