Clarke Masts


Chris Bartram G4DGU <chris@...>
 

I suspect that a few people reading this will have some experience of using the Clarke pump-up masts. I have none, and I'd be grateful for any comments regarding their suitability for microwave operation.

TIA

Chris G4DGU


Dave (G1OGY)
 

Hello Chris
I used to use a trailer mounted SCAM 30 for 1296 (just microwave).
Guyed at the top ring is was stable enough.
I also had a SCAM 12 with a Tenamast cage on the end of the shack (brick), unguyed; and I nearly did when the wind got up unexpectedly when it had a box of 21 ele Tonnae at 40-odd feet.
They require guys, IMO, when at height.
Once guyed they are pretty stable.
73
Dave, G1OGY


On Thu, 30 Dec 2021, 16:54 Chris Bartram G4DGU, <chris@...> wrote:
I suspect that a few people reading this will have some experience of
using the Clarke pump-up masts. I have none, and I'd be grateful for any
comments regarding their suitability for microwave operation.

TIA

Chris G4DGU







ian hope (2E0IJH)
 

Which mast? there are lots of versions, some more suitable than others depending on your head load
 
Ian
M5IJH

 
 
Sent: Thursday, December 30, 2021 at 4:54 PM
From: "Chris Bartram G4DGU" <chris@...>
To: "UKMicrowaves@groups.io" <UKMicrowaves@groups.io>
Subject: [UKMicrowaves] Clarke Masts
I suspect that a few people reading this will have some experience of
using the Clarke pump-up masts. I have none, and I'd be grateful for any
comments regarding their suitability for microwave operation.

TIA

Chris G4DGU





 


Clive Elliott GW4MBS
 

Not to be confused with pump up, I have two PU-8 that are push up, so just watch out for the PU designation!

I recently sold a Clark 12m pump up that was fine for omni antennas but anything directional it was a pain to have to lock each section in turn & calibrate the bearings which was very tedious. I have never tangled with a SCAM 12 as that seemed too monstrous for one person handling.

I have three Hilomasts NH9 (9m), which are each liftable by one person. The NH series have a keyway & to eliminate any slight sectional play each section can be locked. Because I live in a valley & fire the 1m Gibertini as it were into.the hillside it makes no difference whether the mast is extended or not! The only reason to extend is to clear nearby sheds in certain directions. I have a rotator at the base & can turn at the rate of 1 rev per 4 mins, which is handy.

For portable use I have a NH5 (5m) fitted to the Land Rover so I can see over hedges & walls. I'm quite keen on Hilomasts, 45 years ago I used to have a 60ft one with fly swatter at the top which had more gain than the 3ft dish at the base & all turned with prop pitch motor.
--
Clive GW4MBS (ex-G8ADP)
Pottering on 6m - 3cm in a valley in IO71XW where any QSO is a triumph of optimism over geography!


John Lemay
 

Hello Chris

Just to add a couple of points to those already made:-

These masts (not just Clarke) leak to a greater or lesser extent. Therefore if a mast has been extended for a long period, and then the locking mechanism is released to bring the aerial down, sections can travel downward quite quickly. You need to be careful to avoid trapped fingers (or cables) between the collars. Those same leaky seals can let water in, and I've seen one substantial mast completely ruined when water inside froze.

I think Neil G4DBN has a tale to tell about his pump-up mast .............

Regards

John G4ZTR

-----Original Message-----
From: UKMicrowaves@groups.io [mailto:UKMicrowaves@groups.io] On Behalf Of Chris Bartram G4DGU
Sent: 30 December 2021 16:55
To: UKMicrowaves@groups.io
Subject: [UKMicrowaves] Clarke Masts

I suspect that a few people reading this will have some experience of
using the Clarke pump-up masts. I have none, and I'd be grateful for any
comments regarding their suitability for microwave operation.

TIA

Chris G4DGU


ian hope (2E0IJH)
 

Scam 12's top section is known for filling with water and cracking when frozen
 
Ian
M5IJH

 
 
Sent: Thursday, December 30, 2021 at 7:20 PM
From: "John Lemay" <john@...>
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Clarke Masts
Hello Chris

Just to add a couple of points to those already made:-

These masts (not just Clarke) leak to a greater or lesser extent. Therefore if a mast has been extended for a long period, and then the locking mechanism is released to bring the aerial down, sections can travel downward quite quickly. You need to be careful to avoid trapped fingers (or cables) between the collars. Those same leaky seals can let water in, and I've seen one substantial mast completely ruined when water inside froze.

I think Neil G4DBN has a tale to tell about his pump-up mast .............

Regards

John G4ZTR


-----Original Message-----
From: UKMicrowaves@groups.io [mailto:UKMicrowaves@groups.io] On Behalf Of Chris Bartram G4DGU
Sent: 30 December 2021 16:55
To: UKMicrowaves@groups.io
Subject: [UKMicrowaves] Clarke Masts

I suspect that a few people reading this will have some experience of
using the Clarke pump-up masts. I have none, and I'd be grateful for any
comments regarding their suitability for microwave operation.

TIA

Chris G4DGU










 


Nick Garrod
 

The larger Clarke masts will take a small dish and amp, as this picture taken circa 1990, illustrates, with a 2.2GHz link.

https://flic.kr/p/9XQRfk


I can’t remember what the maximum allowed wind speed was.  The land rovers were very heavy with all the technical kit installed and also had outrigger legs when parked up.

I have a SCAM 12, which I haven’t used since I moved house and certainly that is not suitable for single person deployment. 


A midpoint on Wincobank Hill Sheffield covering the Hillsborough inquest around the same time.

 

https://flic.kr/p/9XTJ3u

 


Nick G0OQK


g4zod@btinternet.com
 

I have a 40 Foot Clarke Pneumatic mast.

I have stacked on a 12 Foot Hang Glider main spar:-

A 5 element Met Yagi for 2M

A 14 Element MET Yagi for 70 CMs

A 14 over 14 Yagi for 23 Cms

It is not guyed, but is only pumped up when conditions are calm .

I have had lots of problems with water ingress, which at one time froze, jamming the mast and wrecking the seals.

I have replaced all the seals, but now can only partially raise the mast. (I assume the military have a regular maintenance cycle and spares/ costs are no problem!)

It gave good service until it jammed up. It is also a "temporary structure" as being portable has advantages with the local Council regulations

I would defiantly get another one to replace my old one.

Julian

G4ZOD




--










Dave_G0WBX
 

From: Chris Bartram G4DGU
Date: Thu, 30 Dec 2021 08:54:49 PST

I suspect that a few people reading this will have some experience of using the Clarke pump-up masts. I have none, and I'd be grateful for any comments regarding their suitability for microwave operation.

TIA

Chris G4DGU


One critical tip.

DO NOT (sorry...)  Use a mineral oil such as WD40 etc, to clean/lube the sections.

Use a Silicone based lubricant, else the seals will deteriorate (rot) over a short time.

(Dont ask...)

73.

Dave G8KBV.



-- 
Created on and sent from a Unix like PC running and using free and open source software:


Dave_G0WBX
 

Therefore if a mast has been extended for a long period, and then the locking mechanism is released to bring the aerial down, sections can travel downward quite quickly.


You can help mitigate disasters like that, by repressurizing them before undoing the locking clamps.

You do have a pressure gauge on the mast air feed don't you?

So you record what it was when extended, and can re-pressurise it to that again before letting the clamps off...


Of course, if the ambient temp' is below freezing when you need to take it down in a hurry, take great care...


73   Dave G8KBV.



-- 
Created on and sent from a Unix like PC running and using free and open source software:


ian hope (2E0IJH)
 

Always pressurize a Clark mast before lowering, you use the air releasing to slow the descent of sections
 
Ian
M5IJH

 
 
Sent: Thursday, December 30, 2021 at 8:26 PM
From: "Dave_G0WBX via groups.io" <g8kbvdave@...>
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Clarke Masts

Therefore if a mast has been extended for a long period, and then the locking mechanism is released to bring the aerial down, sections can travel downward quite quickly.


You can help mitigate disasters like that, by repressurizing them before undoing the locking clamps.

You do have a pressure gauge on the mast air feed don't you?

So you record what it was when extended, and can re-pressurise it to that again before letting the clamps off...

 

Of course, if the ambient temp' is below freezing when you need to take it down in a hurry, take great care...

 

73   Dave G8KBV.

 

 

--
Created on and sent from a Unix like PC running and using free and open source software:


Nick Garrod
 

If your mast freezes in the up position, a carefully directed stream of urine can release it. An ex colleague demonstrated the technique to the assembled press corps when covering the eviction of the peace camp at RAF Molesworth, many years ago. He went on to great success in film and TV comedy. 


Nick G0OQK. 


Neil Smith G4DBN
 

I have three SCAM12s, I use one of them every day, leaving it up for up to 12 hours.  I never lock the sections except when it's below freezing. It's fixed to a sturdy brick barn wall and is run from a low pressure dry air source regulated to about 20 psi, but only gets enough to ensure the top section is solidly up.  It will hold pressure for at least 48 hours, unlike the others, which are a bit leaky and only stay up for maybe 6 hours unless they are locked.  If I'm takig down a locked SCAM12, I repressurise it.

Where possible, I cover the joints on the SCAMs that are not inflated, or ensure the are inflated to full height after rain so any water is cleared from the bypass drains.. My spigot is solid and had two O rings so it doesn't let water in, but I still get a little condensation in the top section, and check it periodically.  I really don't want that filling up and then freezing and pushing out the spigot.

I run a 95cm steel dish, plus a steel elevation strut and rotator and two heavy radio boxes with transverters and PAs. Head load is about 18 kg.  Below 14 mph or so, the dish stays reasonably on target, but there is enough sway to get measurable doppler. If the wind is forecast to go above 14 mph, I run guys and lock the sections.  If you guy it then the pressure drops, it isn't guyed any more.

I once left it up overnight without guys and there was a really strong wind overnight.  The side force on the mounts snapped four steel bolts and the whole thing pivoted about the upper fixing, leaving it leaning at more than 45 degrees, with all that load, plus wind and the 90+ kg of mast.  It twisted the 60 x 60 x 6 mm steel angle of the frame like it was made from nougat, but the mast was totally undamaged, and I managed to release the pressure and hauled it back to fully retracted.  The barn wall didn't do quite so well.  The fixings are 16 mm diameter steel rods and several of the bricks cracked, some mortar lines opened and part of the tiled roof was lifted up.  Total mass of the bits of barn that moved were in excess of a quarter of a ton.

The SCAM was totally unscathed apart from some paint flakes.  I mended the wall and tiling, made a new wall bracket and fixed it to a different bit of wall, added a lot of heavy internal bracing and was back on the air in two days. The bend in the SCAM when it was leaning over was pretty horrific, but it didn't put a set in any of the sections.  Tough units.

I always lock the sections when using a SCAM on the legs, and always have multiple folks to pay out and manage the guy tension, plus another body to operate the air feed and act as lookout and banksman.  With it bolted to a building, it's totally OK for single operator use UNLESS you leave it up too long in a gale and need to drop it safely with a large cross-section antenna.  That gets sketchy really rapidly unless you arrange some fancy pulley take-up arrangements on the windward guys, or drop it in stages, retensioning windward guys as you go.

One time I had a very funny but potentially serious incident, where I didn't notice that the feeders were wrapped round my leg and suddely tightened around my knee.  By the time I realised what was happening, I was too far from the air tap to turn it off., and had been pulled to the point where my free leg was off the ground and my shoulders hit the concrete.  As the mast was only part way up, there was a LOT of available force. I managed to grab the air feed pipe and tried to pull it out of the connector, but couldn't reach it.  I managed to haul myself towards the mast base using the hose and turned off the tap, but was still very stuck, with my foot still hopelessly trapped.  I hauled as hard as I could, using the cage of the SCAM base for handholds and eventually managed to grab the feeder bundle just beyond my ankle and wriggled until it let go of my ankle.  Now I was hanging on to the feeders of a pressurized SCAM that would shoot up and go into orbit if I let go, and couldn't reach the tap, so I slowly paid out the feeder until the mast had extended far enough to reduce the excess force to zero.  As the thing was now well extended, I just re-opened the tap and let it inflate the rest of the way.  I was on my own, it was before everyone worked from home and I didn't have my phone with me. Upside is that nobody recorded the incident for posterity.

The strength of the four-strand sinnet finger-trap plaits that I use to secure feed, power and control lines is remarkable for anyone who has seen my considerable mass. 

In case of freezing sections, I have a heated brew belt thingy that is a bit more gentle than the usual "squirt it with warm water" method.

I reckon I've pumped this mast with the dish, boxes, rotator and elevator up and down at least 900 times now and it's still working perfectly,  The other ones don't get so much use.  Only other scare was when I didn't realise that several section had frozen, and  was letting out the air when three sections let go and dropped very rapidly.  Two hit the collars below, but the shock made the last section grip, so the impact was absorbed by the air column.  Phew.


Neil Smith G4DBN
 

As for aiming, without locking the sections, so long as the location pins and grooves are in good shape, I get repeatable aiming to within a degree or so at 10 GHz, but usually do a swift calibration on a distant beacon of the signals reflected off Drax chimney to be certain.   I have to do that anyway if I lock the sections, so it's no great hassle. I always approach a final heading in the same direction so any slop tends to be taken out.

On 30/12/2021 20:47, Neil Smith G4DBN wrote:
I have three SCAM12s, I use one of them every day, leaving it up for up to 12 hours.  I never lock the sections except when it's below freezing.



Chris Bartram G4DGU <chris@...>
 

Many thanks to all those who replied to my note.

The response was pretty well as I'd surmised, and I don't think I'll go there! My suspicion is that I'll go for a ground-mounted tilt-over, telescopic steel mast, such as a Tennamast. Any comments anyone?

The absence of guys is a given as far as my garden manager is concerned. Also I live in a particularly windy place, due to the local topography, and as I get older, the thoughts of struggling with an antenna system which is thrashing about in a near hurricane isn't at all attractive. Been there, done that, and survived! I've carried out a fairly detailed study of the ways in which I could mount the antennas on the house, but that wouldn't be easy.

As I'm fairly remote from centres of activity on the higher microwave bands, I do need a reasonably large dish, say 1m, and I'd like to have a reasonable 432MHz antenna, so that I can return to playing MS on that band. As I live on the edge of a still very 'local' Cornish village I also want to keep the antennas hidden behind the house when not in use.

Constructive comments gratefully received!

73

Chris G4DGU


ian hope (2E0IJH)
 

The small aluminium tilt overs Gary MM0CUG does are not bad, worth a look Chris, Lightweight and should easily handle a small dish
 
ian
M5IJH

 
 
Sent: Thursday, December 30, 2021 at 9:06 PM
From: "Chris Bartram G4DGU" <chris@...>
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Clarke Masts
Many thanks to all those who replied to my note.

The response was pretty well as I'd surmised, and I don't think I'll go
there! My suspicion is that I'll go for a ground-mounted tilt-over,
telescopic steel mast, such as a Tennamast. Any comments anyone?

The absence of guys is a given as far as my garden manager is concerned.
Also I live in a particularly windy place, due to the local topography,
and as I get older, the thoughts of struggling with an antenna system
which is thrashing about in a near hurricane isn't at all attractive.
Been there, done that, and survived! I've carried out a fairly detailed
study of the ways in which I could mount the antennas on the house, but
that wouldn't be easy.

As I'm fairly remote from centres of activity on the higher microwave
bands, I do need a reasonably large dish, say 1m, and I'd like to have a
reasonable 432MHz antenna, so that I can return to playing MS on that
band. As I live on the edge of a still very 'local' Cornish village I
also want to keep the antennas hidden behind the house when not in use.

Constructive comments gratefully received!

73

Chris G4DGU






 


Dave smith
 

I Got a Tennamast  3 years agO.
It mounts up the side of the house, and I am perfectly satisfied with it. I have 2 times 8ele two mtr beams, a 2 element 4 mtr, A 70 cm beam and a 23 cm beam. The ability to raise and lower it single handed makes antenna work easy.
I will add that I have no connection with the company…..it does what it says on the tin.
Dave…G4DAX

On Thu, 30 Dec 2021 at 22:43, ian hope (2E0IJH) <ian@...> wrote:
The small aluminium tilt overs Gary MM0CUG does are not bad, worth a look Chris, Lightweight and should easily handle a small dish
 
ian
M5IJH
 
 
Sent: Thursday, December 30, 2021 at 9:06 PM
From: "Chris Bartram G4DGU" <chris@...>
To: UKMicrowaves@groups.io
Subject: Re: [UKMicrowaves] Clarke Masts
Many thanks to all those who replied to my note.

The response was pretty well as I'd surmised, and I don't think I'll go
there! My suspicion is that I'll go for a ground-mounted tilt-over,
telescopic steel mast, such as a Tennamast. Any comments anyone?

The absence of guys is a given as far as my garden manager is concerned.
Also I live in a particularly windy place, due to the local topography,
and as I get older, the thoughts of struggling with an antenna system
which is thrashing about in a near hurricane isn't at all attractive.
Been there, done that, and survived! I've carried out a fairly detailed
study of the ways in which I could mount the antennas on the house, but
that wouldn't be easy.

As I'm fairly remote from centres of activity on the higher microwave
bands, I do need a reasonably large dish, say 1m, and I'd like to have a
reasonable 432MHz antenna, so that I can return to playing MS on that
band. As I live on the edge of a still very 'local' Cornish village I
also want to keep the antennas hidden behind the house when not in use.

Constructive comments gratefully received!

73

Chris G4DGU






 


Robert G8RPI
 

Be very careful if you re-pressurise a mast that has any section locked part way up. Releasing the lock can cause sudden extension and significant, possibly hidden damage. Doing it twice can release (launch!) a section completely. I have permanent injuries due to this failure mode of a SCAM 12.

The section on the ground hit me on the way down. The mast on the front is a composite push-up. It was re-badeged so I don't know the OEM.

The SCAM had existing sheared fastners on a collar and had been locked off at part extension by a untrined person who had been specifically told not to do so.
Medical treatment was excelent, even more so when they were told I was a guest of JY1 (the trip was not related to amateur radio).
Robert G8RPI.


Graham Shirville
 

....and do I spot THRUST -SSC  in the background?

73

Graham G3VZV

On 09/01/2022 13:03, Robert G8RPI via groups.io wrote:

Be very careful if you re-pressurise a mast that has any section locked part way up. Releasing the lock can cause sudden extension and significant, possibly hidden damage. Doing it twice can release (launch!) a section completely. I have permanent injuries due to this failure mode of a SCAM 12.

The section on the ground hit me on the way down. The mast on the front is a composite push-up. It was re-badeged so I don't know the OEM.

The SCAM had existing sheared fastners on a collar and had been locked off at part extension by a untrined person who had been specifically told not to do so.
Medical treatment was excelent, even more so when they were told I was a guest of JY1 (the trip was not related to amateur radio).
Robert G8RPI.


Robert G8RPI
 

Yes 1996 Al Jafr Jordan