HRO capacitor gearbox repair - UK Vintage Radio Repair and Restoration Discussion Forum

G4_Pete · 12th Mar 2022, 5:11 pm

With a spare part gear wheel extracted from a gearbox donated by Wendymott I have managed to repair an HRO cast gearbox type variable capacitor. Repair summarised on the pdf file attached.

Pete

ms660 · 12th Mar 2022, 8:18 pm

Lawrence.

Bazz4CQJ · 13th Mar 2022, 2:35 am

Interesting, useful, thanks. I may one day get around to overhauling my HRO drive and 4-gang. The latter was sprayed with the stuff used to prevent corrosion in the tropics, and ~80 years on, it looks.... very grotty? Not sure how easy/hard that stuff would be to get off; "if it ain't bust don't fix it" may apply.

B

Radio Wrangler · 13th Mar 2022, 6:08 am

I'd had a look in the attic, remembering, I thought, two HRO gearboxes.

Ha! Close but no cigar.

One was grey painted but had the Muirhead name cast into the lid. The two output shafts were just stubs, quarter inch diameter.

The second one had the National logo on the lid and was a genuine HRO gearbox casting, but inside it had double reduction with plain pinions and anti-backlash plate gears giving a single output at the rear.

Both had the right input shafts and eccentric bush for the velvet vernier knob/dial but neither was a real HRO gearbox. I'd bought them as examples of how variations got played on a theme.

I'm still wondering what each was used in.

Of course, the HRO had James Millen behind it, and he founded a mechanical parts for radio business in his own name. But it's branded National.

David

ms660 · 13th Mar 2022, 11:54 am

PW drive's were available separately, the straight through drive was the NPW-O and the one with two stub shafts was the PW-O, the National 1-10 VHF receiver used the latter type.

Lawrence.

12th Mar 2022, 8:18 pm	#2
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: HRO capacitor gearbox repair Lawrence.

13th Mar 2022, 2:35 am	#3
Bazz4CQJ Dekatron Join Date: Apr 2009 Location: Oxfordshire, UK. Posts: 4,935	Re: HRO capacitor gearbox repair Interesting, useful, thanks. I may one day get around to overhauling my HRO drive and 4-gang. The latter was sprayed with the stuff used to prevent corrosion in the tropics, and ~80 years on, it looks.... very grotty? Not sure how easy/hard that stuff would be to get off; "if it ain't bust don't fix it" may apply. B __________________ Saturn V had 6 million pounds of fuel. It would take thirty thousand strong men to lift it an inch.

13th Mar 2022, 6:08 am	#4
Radio Wrangler Moderator Join Date: Mar 2012 Location: Fife, Scotland, UK. Posts: 22,899	Re: HRO capacitor gearbox repair I'd had a look in the attic, remembering, I thought, two HRO gearboxes. Ha! Close but no cigar. One was grey painted but had the Muirhead name cast into the lid. The two output shafts were just stubs, quarter inch diameter. The second one had the National logo on the lid and was a genuine HRO gearbox casting, but inside it had double reduction with plain pinions and anti-backlash plate gears giving a single output at the rear. Both had the right input shafts and eccentric bush for the velvet vernier knob/dial but neither was a real HRO gearbox. I'd bought them as examples of how variations got played on a theme. I'm still wondering what each was used in. Of course, the HRO had James Millen behind it, and he founded a mechanical parts for radio business in his own name. But it's branded National. David __________________ Can't afford the volcanic island yet, but the plans for my monorail and the goons' uniforms are done

13th Mar 2022, 11:54 am	#5
ms660 Dekatron Join Date: Apr 2011 Location: Cornwall, UK. Posts: 13,454	Re: HRO capacitor gearbox repair PW drive's were available separately, the straight through drive was the NPW-O and the one with two stub shafts was the PW-O, the National 1-10 VHF receiver used the latter type. Lawrence.