Welcome to

My Clark-mast

 

Introduction

 

Everybody knows what a Clark-mast is. It is a telescopic, metal mast. Usually 2m when collapsed and about 10m when entirely extracted. You can find them at HAM-markets, dump, surplus and second-hand pages. Anyway, I got mine from a very good friend who was interested in something I didn’t use anymore so we had a fair trade.

The only problem with the mast was that is was not entirely as I wanted. These are the things I had to change or fix and I think it is useful for other owners to check these points:

 

  1. Greasing the elements
  2. Adjusting the alignment of the elements
  3. Replace fixation-screws
  4. Making an antennamount
  5. Fix air leak in bottom
  6. Remove crap
  7. Make durable air-inlet

 

These points are easy to handle and when you have a good store nearby (www.frissen.nl) you will be able to do all the things.

Every section is well described and where necessary I made a drawing since I forgot to make pictures. No, I am not going to disassemble the whole thing!

 

1.       Greasing the elements

 

The former owner was so nice to clean everything but since it must be air-tight and without friction, you will need to grease every moving part.

Careful: not every grease is good. I had original Clark grease, but it is far too expensive. When I have time, I’ll find a replacement!

 

First you have to do the most annoying part: disassemble the mast. This is quite easy when you have the right equipment. You’ll need the following tools:

-          screwdriver flat

-          screwdriver cross

-          imbus or torx key

-          hammer

 

Ofcourse I forgot some, but you’ll find out.

When you unscrew the rings, take care not to loose any screws and other parts. The plastic things in the rings must be adjusted afterwards; take them out of the ring. You can put them back in from the outsied.

Be careful with the alignment-thing. It is a brown part that prevents the mast from rotating. There is a little feather in it!

 

Let’s assume you have al the parts removed. You can now reassemble it while greasing the inside of the rings. Also the elements must be greased. Take a plastic glove and rub it in. Hmmmmm…..! I advise you to do this in the very end because you have to handle the mast a few times…

 

2.       Adjusting the alignment of the elements

 

When assembling the mast, let’s take the first ring to learn how to assemble.

The ring must be fixed with the normal screws; the plastic things should be pressed into the ring and then the torx screw has to be inserted. Now do the following:

 

  1. When the mast is horizontally, screw the bottom screw inside so the mast will rise a bit until it is in the centre.
  2. Screw the upper screw inside until the mast is locked.
  3. Repeat for the horizontal screws by rotating the mast 90 degrees.
  4. Make sure every screw is locked.
  5. Unscrew every screw 90 degrees and check if the mast will come out. Repeat until it does.

 

Now you have perfectly aligned the mast. When it is greasy in the end, it will slide in and out very easily.

Always make sure the mast doesn’t move up and down; when it does, the screws are too loose! It must be like it is locked.

 

3.       Replace fixation screws

 

Some models have fixationrings (which hold the elements up when pressure is gone) that can be fixed with strange screws. Other have screws with a knob on it and they are great. I replaced the screws by imbus or torx screws. However, the screws have a strange thread of 6mm by 1mm. Normally this is 6mm by 1,25mm but no…

You can replace the original by normal m6 screws. I took imbus for it’s stability and good tools. Don’t puch the screws with too much force. The thread of the ring might break!

Buy screws of 40mm length; they will do.

 

4.       Making an antennamount

 

The top of the mast has a 24mm end that is about 5cm long. Far too short for an antenna and Clark sells something that should make this work out. Will cost a lot.

No, if you take a screw-nut of about m10 that is 30mm long (or any other size that can be fitted within) you can take the edges off until it fits exactly into the mast. Now you have a good thread in the mast.

When you have a piece of 40mm pipe of about 20cm long and a screw of about this length with the above mentioned diameter, you can fix this pipe over the mast against the upper ring by screwing the screw into the nut.

 

Now you can attach a normal antenna.

 

5.       Fix airleak in the bottom

 

When you receive a secondhand mast, I bet it leaks air through the bottom. This is caused by a rubber O-ring in the bottom that tends to be rotten away. This is caused by water, penetrating into the bottom section. It should be removed by the air flowing out, but when stored improperly the water stays in.

Leaking air can be detected by inflating the mast with the sections locked so there will be some pressure inside. If you hear the air leaking away or when the pressure drops within a few hours, this might be happening.

Now let’s change this ring.

  1. Unscrew the bottom screws
  2. Take a hammer and gently tick against the bottom away from the mast. The bottom should come out revealing the problem.
  3. Remove the ring and grease
  4. Grease the new ring, put it into the bottom and (very important) make sure the space between the bottom and the ring is filled with grease so it will slide
  5. Remove any pumpholder or other rings (see point 6)
  6. Re-insert the bottom with gentle ticks with the hammer.
  7. Screw the screws inside
  8. Ready.

 

Important is that the rubber O-ring fits exactly over the bottom and into the space. When disassembled, take the bottom to the store and ask for the best fit. The ring should be thicker than the bottom so it will be pressed together when inserting. Don’t take a ring too thick; 0,5mm thicker is good enough.

 

 

 

6.       Remove crap

 

Yes, the mast is full of crap. I left it on so it wouldn’t roll over the table, but the pump-holder is not used anymore and maybe the bearing-ring on the top for the four legs can be left away. I kept it on, despite of it’s weight. It may be useful for fieldday.

 

When you unscrew the pumpholder, you’ll notice it won’t slide. Take a flat screwdriver and jam it between the two halfs until it becomes wide enough to slide it. Grease may help although you have to clean the mess afterwards…

When you are going to take the bottom off, it is recommended to do this at that time…

 

7.       Make durable air-inlet

 

The pump stinks and so does the hose. The inlet on the mast has a standard ¼” screwthread. Go and buy a fast-coupling airplug to fit into the mast. This is the same as a compressor has and there are a lot of hoses for low prices to get.

 

I bought a 12V compressor and put the same coupling on it. Now I can raise the mast with one toutch of a button!

Using this sort of couplings makes it possible to raise the mast, unplug the compressor or pump (same thread) and the air stays in the mast so it won’t come down.

 

In the end…

 

Now these were my problems. Alltogether it takes about a day to do all this and the result is a great machine. Don’t forget to use guyinglines when using it entirely because it is not very stabel.

Also remember that humidity is bad, although the mast is made of some kind of aluminium. Move the mast up and down every two weeks or so to keep it in shape. I have a quite long hose attached to it and I only raise the mast when needed. If not, I let it down entirely so I can still receive the local repeaters.

 

Hopefully you got enough information to do this work and I wish you a lot of fun!