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AMroo
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« on: June 21, 2008, 08:47:52 PM » |
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I was dreaming of finding a vacuum variable to use in my loop antenna to increase the maximum power I could put into it, when a good friend promptly gave me one. Oh to have such friends eh?
I got it home and announced to the MRS (wife) "Hey look at OUR new radio part".
Thats how I always get around bringing new junk home. Must try it with an old girlfriend one day.
The only problem is I am at a total loss about how to use it.
How do I connect onto it, I plan on using a coupla copper straps around each end?
The tunning control at the top wont do nuffin. In the anti clock wise direction it just unscrews from the main assembly until it comes out. In the clockwise direction it wont budge.
If I remove the blue cap and apply about 50 lbs of of force in the upward direction I can pull the shaft up about half an inch and can feel the suction from a vacuum inside.
So how are you supposed to use this thing looks like you sure need a decent motor and gearing to create enough torque to pull it out and hold it there?
How is it pulled out under so much pressure by such a small tunning shaft? I think I have to drill a hole through the tunning shaft so I can latch onto it hard enough to apply that much force to it.
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WA1GFZ
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« Reply #1 on: June 21, 2008, 09:26:47 PM » |
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I have a number of those caps. You should be able to put a knob on the shaft and turn it clockwise to pull the lead screw out. it will move about an inch or so before the plates are fully unmeshed. Go any further the break the bellows.
The stop is sometimes a set screw in the blue part. IF not there be very careful going too tight. Connections are made with end collars you can buy for big bucks or just put a copper strap either side of the ceramic center.
SS hose clamps work but not too tight.
With the lead screw finger tight grab a hold or the blue collar and pull it out.
It should move a little. IF you can move it easily suspect a poor vacuum.
Any motor drive will need positive stops / interlocks so it is never adjusted too far one way.
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AMroo
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« Reply #2 on: June 22, 2008, 12:28:38 AM » |
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Thanks for your good help.
Mine is acting like this- The vacuum seems fine when I try to pull it outwards I can feel the vacuum, as the shaft gets quickly and strongly pulled back in.
I have removed the blue cover.
If I do up the steel tunning shaft clock wise into the copper part then, when it is it is done up and there is no further movement, it's locked solid.
If I then go anticlockwise I just unscrew the steel tunning shaft out of the copper part it threads into.
So it seems I can't adjust it by turning it, only by pulling it outwards.
Guess you know what it looks like but just including a pictures for others.
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n2bc
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« Reply #3 on: June 22, 2008, 06:23:05 AM » |
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In my limited experience, the pulling resistance has nothing to do with the vacuum. I have a busted vac var that mechanically 'feels' just like a good one. The resistance is from the internal bellows structure.
The collar on the lead screw (that's 'leed' not 'led') should ride against a mating surface in the blue nose end that causes it to pull the internal bellows out.
I've not seen any vac var that had built-in stops. The rotation limits are: CCW when the lead screw begins to unscrew from the cap, and CW when the bellows is fully extended - which is when the mechanical resistance increases. If you force it past the CW limit you will damage the cap! (experience talking here)
It is important that the lead screw and the cap's mating surface be clean - the thread clearance is precision. If you look closely at the lead screw you will see that it has squared threads not at all like a standard machine screw.
Good luck! 73, Bill
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n2bc
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« Reply #4 on: June 22, 2008, 06:27:55 AM » |
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Just noticed the pix you included above.... It may be that you have simply assembled the end out of order...
Remove the lead screw, put the blue end in place, then install the lead screw. The collar on the lead screw should have some ball bearings in it that ride against a mating surface in the blue end of the cap. That's what causes the lead screw to pull out the bellows!
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WA1GFZ
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« Reply #5 on: June 22, 2008, 11:18:14 AM » |
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Sorry OM that picture looks bad. My guess the cap plates are welded in the fully open position. That sleeve in the center should be down flush with the case when you take it apart. Put an ohm meter across it I bet it is shorted.
Save the lead screw and blue collar. The rest of it might be a good target.
Another possible problem is someone dropped it with the plates fully unmeshed and one set of plates shifted so it would not mesh.
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AMroo
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« Reply #6 on: June 23, 2008, 07:51:54 AM » |
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You are dead right, and I could see what you were saying right away.
So I checked the resistance and sure enough it's short Cct.
I am not familiar with these things so this has been helpful, I was suspicious of it as it seemed stuck.
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N3DRB The Derb
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« Reply #7 on: June 23, 2008, 11:29:49 AM » |
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bleah.  I'll take the bread-slicers. vacuum variables always seem too fragile to me. I'd never know if I had a good one. I'm too dumb. |
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w4bfs
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more inpoot often yields more outpoot
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« Reply #8 on: June 23, 2008, 07:03:05 PM » |
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I've never had one jammed before ... this may totally stupid but I would want to work a couple drops of light oil into the puller mech just to see if it would losen up ...at this point , it couldn't hurt ..good luck .. John
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Beefus
O would some power the gift give us
to see ourselves as others see us.
It would from many blunders free us. Robert Burns
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WA1GFZ
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« Reply #9 on: June 23, 2008, 10:02:24 PM » |
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it is shorted internally=junk
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KB2WIG
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« Reply #10 on: June 23, 2008, 11:09:17 PM » |
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If its ta ta, maybee a car bat across it will clear the fault??? if not, maybee it a gud laugh........klc
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What? Me worry?
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WA1GFZ
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« Reply #11 on: June 24, 2008, 08:37:47 AM » |
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car batt might explode Ever see a shorted batt with the side blown off.
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The Slab Bacon
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« Reply #12 on: June 24, 2008, 09:41:26 AM » |
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car batt might explode Ever see a shorted batt with the side blown off.
Been there, done that!! I had one blow the whole top off 20 years ago. I got hit right in the face with the top. Luckily, it just left me with some nasty bruises. If I wouldnt have been wearing glasses back then, I'd prolly be blind!! The Slab Bacon |
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"No is not an answer and failure is not an option!"
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W3SLK
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« Reply #13 on: June 24, 2008, 11:50:33 AM » |
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I have two and the one needs a 'puller f or it. I don't know how I got it without the puller. Its a 10KV @ 450 mmf. I want to use it when I build a big rig. Onething I do know, Rich Measure swears by HIPOTing them to ensure proper voltage rating and vaccuum is still present.
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Mike(y)/W3SLK
Invisible airwaves crackle with life, bright antenna bristle with the energy. Emotional feedback, on timeless wavelength, bearing a gift beyond lights, almost free.... Spirit of Radio/Rush
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flintstone mop
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« Reply #14 on: June 26, 2008, 11:56:27 AM » |
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You'll have to forgive DERBS BLEAH remark. He thinks Vac variables are gay.
A connection can be made to the cap using steel hose clamps on the metal rings on each side of the ceramic center.
I hope your vac is good THEY'RE GREAT
Fred
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Fred KC4MOP
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