Jump to content

24 Ft Mast (I think)


armouredfarmer

Recommended Posts

Someone very kindly gave me two radio masts at the weekend, I assumed at first that they were 5.4 mt type but further inspection shows they very definitely aren't. Each mast consists of 8 fiberglass sections, 36 ins long (not including spigots), 3 pegs, a round metal base, a selection of stay lines, a halyard, 2 stay plates and a cleat all contained in a very neat canvas carrying case . Ring any bells with anyone? Ive googled various NSNs on components and got nothing more useful back than "mast section" and "stay" so frustrated in that direction. The fact that the sections are apparently an imperial length and the carrying case is canvas as opposed to plastic may mean it predates the clansman era.

Pictures to follow when I have the opportunity.

 

PT

Link to comment
Share on other sites

Hi

 

I had a few of the sections at one time but never a complete mast kit - whatever it is goes back to the Larkspur era as I got them at a Leicester radio rally before 1990. If what you have is what I had, then they differ from the more recent RACAL ones in that the outside is fluted and the green is closer to NATO than olive, if I remember rightly. I don't think they are actually Larkspur because the 1950s Larkspur antennas were designed for the 27 foot telescopic steel mast - I think it is related to fixed link or electronic warfare / DF equipment from the late 1960s or early 1970s just before metrication - I have dim memories of seeing a picture in a manual for pre-Vampire DF kit.

 

The big cousin of the 5.4m Clansman mast is the RACAL MA675 which has 8 x 1m fibre glass sections - it differs in that each set of guys has four ropes at 90 degree rather than 3 at 120 degrees.

 

Regards

 

Iain

Link to comment
Share on other sites

Thanks Ian, the outside of mine are not fluted but otherwise they sound similar, one thing that puzzles me is that both mast kits have the same stay sets but there are a strange mix of lengths so you only have two pairs of stays the same length in each mast.

As promised, pictures

QUOTE]

 

That looks remarkably like a scaled-down MA-675 mast in terms of the poles and carrying case, and the direct ancestor of the Clansman 5.4 metre mast from the general size of the beast.

 

Trials model of the 5.4 metre mast (later simplified and lightened as a result of the trials)?

 

That would be my guess.

 

Chris.

Link to comment
Share on other sites

Yes Jarret, but that's the NSN for the bag unfortunately.

 

This is true, but the bag is custom made for the mast and if you're lucky plugging the NSN into Google will get you one of the 'parts' websites that give a cross-reference to the manufacturer and their product code. (I did this with my MA-675 9 metre mast to get most of the parts list). Once you've got that much information you can expand the search a bit.

 

The canvas case points to it being Larkspur, and stayplate with an extra hole for a halyard points to HF, so the SR A14 (aka BCC 30) is a very likely candidate. A look in the user handbook should confirm that.

 

Chris.

Link to comment
Share on other sites

This is true, but the bag is custom made for the mast and if you're lucky plugging the NSN into Google will get you one of the 'parts' websites that give a cross-reference to the manufacturer and their product code. (I did this with my MA-675 9 metre mast to get most of the parts list). Once you've got that much information you can expand the search a bit.

 

The canvas case points to it being Larkspur, and stayplate with an extra hole for a halyard points to HF, so the SR A14 (aka BCC 30) is a very likely candidate. A look in the user handbook should confirm that.

 

Chris.

 

Better get your Gnomes hat on Chris!

Link to comment
Share on other sites

Yep that's it, where did you find that? and could you get me a copy of the erection instructions please?

 

Interesting that it has asymmetric stays!

 

Working out the erection instructions should be fairly easy, you just need to find the peg spacing by trial and error.

(Guessing at about 12 feet for the 'inward facing' stays and 18 feet for the two ends as a first cut.)

 

1) pin the bases to the ground to suit your long-wire aerial (length of aerial + a few feet apart).

1a) measure around 12 feet at 60 degrees from the base either side of the aerial direction and drive a peg in

2) lay the poles out facing inwards, sockets downwards (towards base plate)

3) place halyard cleat over end of first pole, add two (or three) poles, then one stayplate.

4) clip the two short stays (24-ft) to the outer pair of the "group of three" holes in the stayplate.

5) run the stays out at 60 degrees to the line of the aerial and attach to pegs (leave slack!).

6) clip the shorter of the single stay to the single hole in the stayplate.

7) run that stay out towards the base of the mast (and beyond).

8) add the remaining poles to the mast and the stayplate to the top.

9) connect the two longer stays to the outer pair of the "group of three" holes in the stayplate and to the two pegs.

10) connect the halyard pulley block to the third hole.

11) attach the remaining (50-ft?) stay to the single hole in the stayplate and extend it past the base of the mast.

 

Now the fun part, the first go at erecting it (for which you need 4 or 5 people).

 

One person holds the long stays at the rear of the mast, a second person holds the top of the mast, two more hold the short stays (one at each peg), and the last one keeps the base of the mast in position while it is being raised.

 

12) lift the top of the mast and slowly "walk it up". tension should be applied to the back stays to assist the lift, and the two front stay people should keep it centred. (Do this carefully - it may be worth starting with "half a mast" to get the peg spacing sorted.

 

13) once vertical (-ish), decide on the rear peg position, drive that in, and attach the two long stays to that.

 

14) Adjust stays all-round to get the mast vertical, do not over-tighten the stays.

 

15) Repeat for second mast (but you now know the peg spacings required).

 

16) attach wire aerial to halyards and hoist.

 

17) Sorted! (I hope.)

 

(It may be that only one mast was intended to be used, with a sloping wire, but this will do you for a dipole.)

 

Good luck,

 

Chris.

Link to comment
Share on other sites

Right here is the guy line setup and to be honest i cant be arssed scanning again as everything is packed away,i know what happened i saw the pictures in the folder and thought i will clear that lot out not knowing it deletes them from the thread.

Mast.jpg

Link to comment
Share on other sites

Right here is the guy line setup and to be honest i cant be arssed scanning again as everything is packed away,i know what happened i saw the pictures in the folder and thought i will clear that lot out not knowing it deletes them from the thread.

 

Thanks. That is a weird arrangement and must have been difficult to set up in a hurry with two pickets at 14 feet from the base and the third at 32 feet! So much easier with the modern "piece of string" to set the picket spacing.:-D

 

(Mind you, I'm going to have fun trying out my SP48 masts in due course. I may have to make up a "cats cradle" of string with all the relevant peg positions and alignments marked for when setting it out - it doesn't help that the mast is erected at 45 degrees to the intended line of the antenna either.)

 

Chris.

Link to comment
Share on other sites

The guys do have colour coded tags on them to denote length but still an embuggerance,for a dipole i would use the mast but for the end fed as well?only reason behind it i can see is that the fibreglass does flex a bit and with a dipole the steeper angle will help to restrain it but i have had mine up a few times and never managed to get it vertical yet.

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...