UK Vintage Radio Repair and Restoration Powered By Google Custom Search Vintage Radio Service Data

Go Back   UK Vintage Radio Repair and Restoration Discussion Forum > General Vintage Technology > General Vintage Technology Discussions

Notices

General Vintage Technology Discussions For general discussions about vintage radio and other vintage electronics etc.

Closed Thread
 
Thread Tools
Old 20th Nov 2017, 6:46 pm   #1
G6Tanuki
Dekatron
 
G6Tanuki's Avatar
 
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 5,853
Default Chimney antenna-mount: twist or clamp?

I've got the roofers/chimney-stack-rebuilders in at the moment, and intend to use the access their scaffolding provides to put up a Hy-Gain 12AVQ HF antenna.

A couple of 18-inch galvanised 'Mitre brackets' will be used on the chimney itself. The 'traditional' way to attach these is with a galvanised wire round the chimney - and usually the ends of the wire are simply twisted back on themselves to provide a 'loop' for the J-bolts that are then tightened.

I don't like this twisted approach: my idea is to use stainless-steel yacht-rigging wire and similarly-sourced "U-bolt clamps":

https://www.s3i.co.uk/stainless-steel-rope-grip.php

which should last well enough to see me into the time when HF DXCC is really not the sort of thing I'm interested in.

Ideas? Suggestions? Should I use 'thimbles' where the wire is attached to the J-bolts?
G6Tanuki is offline  
Old 20th Nov 2017, 7:02 pm   #2
Tractorfan
Nonode
 
Tractorfan's Avatar
 
Join Date: Mar 2008
Location: St. Frajou, l'Isle en Dodon, Haute Garonne, France.(Previously: Ellesmere Port, Cheshire, UK.)
Posts: 2,716
Smile Re: Chimney antenna-mount: twist or clamp?

Hi,
When I was a lad we used to fold the lashing cable round the thimble. Then we would untwist about a foot of said cable and wrap each strand in turn around the two 'passes' of lashing cable. When that strand ended, we'd wrap the second strand until that also ended, then the third, and so on. If you get my drift.
Hope this helps.
Cheers, Pete.
__________________
"Hello?, Yes, I'm on the train, I might lose the signal soon as we're just going into a tunn..."
Tractorfan is offline  
Old 20th Nov 2017, 7:10 pm   #3
G6Tanuki
Dekatron
 
G6Tanuki's Avatar
 
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 5,853
Default Re: Chimney antenna-mount: twist or clamp?

Yes that wrapping-style is what I'm familiar with - it's the same as used in the classic double-ended "Western Union" splice on overhead telegraph lines.

Problem is, stainless-steel strainer wire is really a lot more-springy than the galvanised-iron lashing-wire of old. Getting the individual strands of stainless to play nicely and not spring undone when I wind the J-bolts up to a decent torque could be a problem; hence my interest in using U-bolt clamps.
G6Tanuki is offline  
Old 20th Nov 2017, 8:04 pm   #4
emeritus
Nonode
 
Join Date: Jan 2012
Location: Brentwood, Essex, UK.
Posts: 2,528
Default Re: Chimney antenna-mount: twist or clamp?

No personal experience, but the accompanying extract from a text book on ropework for yachts (Modern Rope Seamanship, Colin Jarman and Bill Beavis, 2nd Edn, 1983) explains how to make reliable splices in wire ropes. It confirms the need for thimbles (as large as possible) and that the clamps (bulldogs) need to be correctly oriented to avoid damaging the wire. The alternative would be to use a swageless terminal.
Attached Files
File Type: pdf Wire rope splices .pdf (442.8 KB, 42 views)

Last edited by emeritus; 20th Nov 2017 at 8:17 pm.
emeritus is offline  
Old 20th Nov 2017, 8:07 pm   #5
mole42uk
Octode
 
mole42uk's Avatar
 
Join Date: Aug 2010
Location: Bristol, UK
Posts: 1,423
Default Re: Chimney antenna-mount: twist or clamp?

Note that some u bolt clamps have undersized threads and won’t reliably clamp the wire.
__________________
Richard

Index:
recursive loop: see recursive loop
mole42uk is offline  
Old 20th Nov 2017, 8:33 pm   #6
G6Tanuki
Dekatron
 
G6Tanuki's Avatar
 
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 5,853
Default Re: Chimney antenna-mount: twist or clamp?

Quote:
Originally Posted by emeritus View Post
No personal experience, but the accompanying extract from a text book on ropework for yachts (Modern Rope Seamanship, Colin Jarman and Bill Beavis, 2nd Edn, 1983) explains how to make reliable splices in wire ropes. It confirms the need for thimbles (as large as possible) and that the clamps (bulldogs) need to be correctly oriented to avoid damaging the wire. The alternative would be to use a swageless terminal.
Ooh thanks for that! I clearly have quite a bit to learn about this. Alas my uncle Jim [the only real seafarer in the family] is no longer around to give me guidance.
G6Tanuki is offline  
Old 20th Nov 2017, 8:35 pm   #7
G6Tanuki
Dekatron
 
G6Tanuki's Avatar
 
Join Date: Apr 2012
Location: Wiltshire, UK.
Posts: 5,853
Default Re: Chimney antenna-mount: twist or clamp?

Quote:
Originally Posted by mole42uk View Post
Note that some u bolt clamps have undersized threads and won’t reliably clamp the wire.
Good advice again: I'd kinda hope that if I'm buying stuff from the people who equip round-the-eorld yacht-racers they'll know their stuff.

"Cheap" is OK, but not when it involves paying to get scaffolders out to let me reach the failed parts.
G6Tanuki is offline  
Old 20th Nov 2017, 8:41 pm   #8
ms660
Dekatron
 
ms660's Avatar
 
Join Date: Apr 2011
Location: Cornwall, UK.
Posts: 6,012
Default Re: Chimney antenna-mount: twist or clamp?

Stainless steel duplex grips for a loop.

Lawrence.
ms660 is offline  
Old 20th Nov 2017, 9:28 pm   #9
Bazz4CQJ
Octode
 
Bazz4CQJ's Avatar
 
Join Date: Apr 2009
Location: Oxfordshire, UK.
Posts: 1,835
Default Re: Chimney antenna-mount: twist or clamp?

When using stainless steel marine fittings, how do people avoid the pick-up or galling problem on tightened threads; application of some type of a preferred grease, or PTFE tape... ? I've seen some expensive bits of kit completely blethered when people were mean with the tape on stainless pipe fittings!

B
__________________
We know there are known unknowns. But there are unknown unknowns – ones we don't know we don't know.
Bazz4CQJ is offline  
Old 21st Nov 2017, 5:03 pm   #10
Biggles
Octode
 
Join Date: Feb 2004
Location: Hexham, Northumberland, UK.
Posts: 1,783
Default Re: Chimney antenna-mount: twist or clamp?

Good choice to use stainless if you burn solid fuel. Our Rayburn range burns coke and anything mounted on the chimney is eventually compromised due to the mildly corrosive fumes coming from the stack. A lot of standard rigging items seem to be made from fairly soft iron too with a rather thin galvanised coating so they don't last very long when exposed to smoke. I just tend to coat mine with black underseal clag and inspect them fairly often. I'm a bit of a monkey for trying out new antennas so that isn't a problem, and it keeps the neighbours entertained when I'm clambering about on the roof. I find that a bit of plastic tubing pushed over exposed threads on bolts helps a lot when you need to remove the nuts later on.
Alan.
Biggles is offline  
Old 21st Nov 2017, 6:36 pm   #11
AC/HL
Moderator
 
AC/HL's Avatar
 
Join Date: Nov 2003
Location: Heckmondwike, West Yorkshire, UK.
Posts: 6,081
Default Re: Chimney antenna-mount: twist or clamp?

That sounds like the usual declining standards to meet expectations of ever lower prices. Admittedly it's quite a few years since my duties as a general workshop engineer included aerial rigging, but the steelwork was always heavy duty and well galvanised. I used the same method as Pete in post 2.
__________________
Bill, BVWS member
AC/HL is offline  
Closed Thread

Thread Tools



All times are GMT +1. The time now is 6:14 am.


All information and advice on this forum is subject to the WARNING AND DISCLAIMER located at https://www.vintage-radio.net/rules.html.
Failure to heed this warning may result in death or serious injury to yourself and/or others.


Powered by vBulletin®
Copyright ©2000 - 2018, vBulletin Solutions, Inc.
Copyright ©2002 - 2018, Paul Stenning.