Repairing plastic radio dials? - UK Vintage Radio Repair and Restoration Discussion Forum

allan · 15th Dec 2019, 11:48 am

I have an off-white plastic dial 130mm x 345mm (5 x 13 inches) dating from 1946 which is about 0.75mm thick (about 1/32 inch) and has buckled in a few places by 3 or 4mm.
Is there any way of flattening it? The material is quite flexible and hasn't gone brittle.
Allan

Station X · 15th Dec 2019, 12:41 pm

I've had success dipping flexible plastic in boiling water then flattening it under a weight. Trouble is this can dissolve off any lettering, so a hot air gun gently applied to the non-lettering side can also be used. It's possible to get the plastic too hot to touch without damaging it.

Boulevardier · 15th Dec 2019, 4:56 pm

This thread I started when having a similar question might be interesting -

https://www.vintage-radio.net/forum/...d.php?t=157016

Mind you, my radio was a 1980s model, and the plastic used might be nothing like what's in yours. And the scale was much
smaller.

Mike

crackle · 15th Dec 2019, 5:25 pm

Are you sure it is not a celluloid sheet?

Mike

15th Dec 2019, 7:00 pm

Most plastics will flatten (or indeed stay bent) if held in position for a while (days) so clamp twixt two flat plates for a week or so. To reduce the possibility of the letters coming off cover with a silicone release sheet.

allan · 16th Dec 2019, 10:41 am

Thanks for all the suggestions.
I think the dial is made from celluloid and I'll try gluing it to a piece of metal and clamping it between two pieces of wood in a vise.
I've already scanned it and have a high definition bitmap of it (140M) which I photoshopped (not quite finished yet).
Editing the plastic dial will be a bit more difficult.
I may just print a picture and stick this to the receiver's aluminium backplate.
Allan

Mr 1936 · 16th Dec 2019, 9:00 pm

I'm interested to see that on Longwave, in addition to the Aircraft comms allocation at 900 metres (333 kHz) there is also a marking for Air Met Report at about 1200 metres.

From what I have found out, there were Airmet weather reports transmitted from Dunstable on 1224.5 metres (245 kHz). These closed down in about 1950

I also found a reference to Airmet on 1260 metres (238 kHz) from Croydon Airport in the 1920's and 1930's. The transmitters were a few miles away from the airport itself, presumably this was partly to avoid upsetting the MF D/F receiving station which graced the new-fangled control tower.

John (Mr 1936)

MotorBikeLes · 16th Dec 2019, 11:04 pm

If the dial is celluloid, it will surely be VERY yellow by now.
Les.

allan · 17th Dec 2019, 9:52 am

One of the first signals I heard once the long wave local oscillator started was BIA on 339KHz and of course there are dozens of similar signals over the high end of the long wave band.

The dial colour was probably white and is now a bit yellowed but not bad. I should say "off-white" and quite flexible. The overall length has shortened but probably because of the distortions which have occurred across the shorter dimension. The narrow white plastic curved section used in the R1155 dial looks similar material but thinner.
Allan

15th Dec 2019, 11:48 am	#1
allan Pentode Join Date: Oct 2005 Location: South coast near Ringwood/Christchurch, Dorset, UK. Posts: 230	Repairing plastic radio dials? I have an off-white plastic dial 130mm x 345mm (5 x 13 inches) dating from 1946 which is about 0.75mm thick (about 1/32 inch) and has buckled in a few places by 3 or 4mm. Is there any way of flattening it? The material is quite flexible and hasn't gone brittle. Allan

15th Dec 2019, 12:41 pm	#2
Station X Moderator Join Date: Jan 2003 Location: Ipswich, Suffolk, IP4, UK. Posts: 21,289	Re: Repairing plastic radio dials? I've had success dipping flexible plastic in boiling water then flattening it under a weight. Trouble is this can dissolve off any lettering, so a hot air gun gently applied to the non-lettering side can also be used. It's possible to get the plastic too hot to touch without damaging it. __________________ Graham. Forum Moderator Reach for your meter before you reach for your soldering iron.

15th Dec 2019, 4:56 pm	#3
Boulevardier Octode Join Date: Sep 2017 Location: Bristol, UK. Posts: 1,657	Re: Repairing plastic radio dials? This thread I started when having a similar question might be interesting - https://www.vintage-radio.net/forum/...d.php?t=157016 Mind you, my radio was a 1980s model, and the plastic used might be nothing like what's in yours. And the scale was much smaller. Mike

15th Dec 2019, 5:25 pm	#4
crackle Rest in Peace Join Date: Mar 2011 Location: Basildon, Essex, UK. Posts: 4,100	Re: Repairing plastic radio dials? Are you sure it is not a celluloid sheet? Mike

15th Dec 2019, 7:00 pm	#5
Guest Guest Posts: n/a	Re: Repairing plastic radio dials? Most plastics will flatten (or indeed stay bent) if held in position for a while (days) so clamp twixt two flat plates for a week or so. To reduce the possibility of the letters coming off cover with a silicone release sheet.

16th Dec 2019, 10:41 am	#6
allan Pentode Join Date: Oct 2005 Location: South coast near Ringwood/Christchurch, Dorset, UK. Posts: 230	Re: Repairing plastic radio dials? Thanks for all the suggestions. I think the dial is made from celluloid and I'll try gluing it to a piece of metal and clamping it between two pieces of wood in a vise. I've already scanned it and have a high definition bitmap of it (140M) which I photoshopped (not quite finished yet). Editing the plastic dial will be a bit more difficult. I may just print a picture and stick this to the receiver's aluminium backplate. Allan Attached Thumbnails

16th Dec 2019, 9:00 pm	#7
Mr 1936 Heptode Join Date: Mar 2017 Location: Romsey, Hampshire, UK. Posts: 524	Re: Repairing plastic radio dials? I'm interested to see that on Longwave, in addition to the Aircraft comms allocation at 900 metres (333 kHz) there is also a marking for Air Met Report at about 1200 metres. From what I have found out, there were Airmet weather reports transmitted from Dunstable on 1224.5 metres (245 kHz). These closed down in about 1950 I also found a reference to Airmet on 1260 metres (238 kHz) from Croydon Airport in the 1920's and 1930's. The transmitters were a few miles away from the airport itself, presumably this was partly to avoid upsetting the MF D/F receiving station which graced the new-fangled control tower. John (Mr 1936)

16th Dec 2019, 11:04 pm	#8
MotorBikeLes Nonode Join Date: Dec 2012 Location: Kirk Michael, Isle of Man Posts: 2,350	Re: Repairing plastic radio dials? If the dial is celluloid, it will surely be VERY yellow by now. Les.

17th Dec 2019, 9:52 am	#9
allan Pentode Join Date: Oct 2005 Location: South coast near Ringwood/Christchurch, Dorset, UK. Posts: 230	Re: Repairing plastic radio dials? One of the first signals I heard once the long wave local oscillator started was BIA on 339KHz and of course there are dozens of similar signals over the high end of the long wave band. The dial colour was probably white and is now a bit yellowed but not bad. I should say "off-white" and quite flexible. The overall length has shortened but probably because of the distortions which have occurred across the shorter dimension. The narrow white plastic curved section used in the R1155 dial looks similar material but thinner. Allan