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[Articles Home]  [Add Article]  

Hit the Brakes

William Caton (KL7VU) on April 24, 2014
View comments about this article!

Hey Y'all

Ok,

While I've personally never been able to afford a really large array... I've heard the 'guys' talking about this stuff for years.

Let's talk brakes here...

When you depress the button that says 'Brake Release' on your control box, what you "should" hear is a 'snap' sound. This... according to the specified instructions is the -Solenoid- energizing and pulling the 'brake wedge' out of the gear train, thus allowing the gear(s) to turn freely. If you don't hear this 'snap' sound, something's wrong. Also, if the instant you take your finger OFF the brake release button, if you hear another 'snap' there is no brake delay installed on your control box.

Even with my hearing degradation, I can hear it (the snap) clearly, on mine, now (2014).

Now what the 'powers that be' are publishing is that: When an antenna system is abruptly stopped, the rotational forces involved in the thing coming to a stop and then waggling back-n-forth can cause the thing to slip within the locking mechanism(s) and become 'off-degree' according to your directional control indicator, on your control box, over time... (a fraction of a degree at a time). So "they" have decreed that a "BRAKE DELAY" mechanism is in order...(even for a light-weight system like my K4KIO hexagonal beam) to delay the actual engagement of the 'wedge-brake' until the motorized rotational adjustment has come to a complete stop.

I completely concur wholeheartedly'... "Hey I'm on the page here still, yet".

Now, to understand this one must understand that the brake mechanism is held in-place by springs, at least on our Ham series rotors. Thus, the brake is "Always-On" and the 'wedge' mechanism is only disengaged when the springs that hold the wedge in-place between the gears of the rotational motor are pulled back, and out of the gear-train by the magnetic solenoid and can only be released when the solenoid is de-energized (i.e., the BRAKE RELEASE button is not depressed). As soon as you take your finger off of the brake release button, the springs snap the "wedge" back into the gear train. That slams the rotation to an abrupt stop and the array wags back and forth. We, as hams, don't need or want this.

What this brake-delay thing that ALL the guys are talking about is, does, is allow the rotor-motor to stop turning completely before the brake wedge springs release and the wedge locks the gears. It has to bleed down enough for the solenoid to loose magnetic control over the springs and then the wedge snaps back into the gear train, thus locking the moving parts, and that shouldn’t happen until the rotational movement stops completely, hopefully.

So, by adding an air capacitor and a 3 Meg-Ohm resistor (or so), in series with the switch, they create a "bleed down" switch between the solenoid and the brake wedge. If your control unit did not come to you with this circuit, already in-place, you need one... either now or later, it's your choice (but I would recommend that if you're not really electronics savvy, don't try to build one yourself, buy the darn thing an install it, it's simple.

Norm's Rotor Service calls their version of this 'brake delay system' the BD-189 and sells the kit for about $30. You need one or one like it, either theirs or someone else’s, and I don't mean to be proprietary here, Y'all need one". It's a self-serve product, usually, and you have to install it yourself. It takes all of 10 minutes... even for me!

This is an excerpt from an e-mail I sent to one of my friends and I sincerely hope eHam puts it in their column somewhere.

KL7VU - Willy

73

Member Comments:
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Hit the Brakes  
by G3RZP on April 24, 2014 Mail this to a friend!
Delayed braking is highly desirable in a rotator. On my T2X, I use a delayed release relay to activate the wedge - because I had one. Been working well since 1987.
 
Hit the Brakes  
by W4XKE on April 24, 2014 Mail this to a friend!
I always thought that it'd be a good idea to slow down the motor too, so the entire affair isn't moving so fast. A large beam develops a lot of torque as it swings around.

I guess the high speed is to satisfy contesters who don't have any time to lose. :-)

Everybody in our neighborhood knows when my neighbor is turning his beam. The brake wedge goes KLAAANGGG! and scares kids, dogs and delivery men until they get used to it. That's one of the typical complaints about having ham towers close by.

Maybe the next thing they ought to look at would be a muffler. But then, you wouldn't be able to hear it inside the house with the radio on. Perhaps a "Ready" light on the control could replace the need for noise.
 
RE: Hit the Brakes  
by K4PIH on April 24, 2014 Mail this to a friend!
Never needed brakes with my ARS Deluxe (Armstrong Rotor System).
 
RE: Hit the Brakes  
by AA4PB on April 24, 2014 Mail this to a friend!
Brake delay circuits are nice but you can also accomplish the delay manually. Simply continue to hold the brake button down for a couple of seconds after you release the rotation button.

The HAM series brake wedge engages groves on the inside of the housing. It doesn't engage the gear train.

The brake delay circuit is not as simple as placing a resistor and capacitor in series with the switch. The brake operates from an AC voltage, the same voltage that operates the motor. The simplest brake delay I've built consists of a couple of diodes, a resistor, a capacitor, and a 24VDC relay. The contacts on the relay operate the brake.
 
RE: Hit the Brakes  
by KG4RUL on April 24, 2014 Mail this to a friend!
"So, by adding an air capacitor and a 3 Meg-Ohm resistor (or so), in series with the switch, they create a "bleed down" switch between the solenoid and the brake wedge."

Just how large is this "air capacitor" anyhow?
 
RE: Hit the Brakes  
by AA4PB on April 24, 2014 Mail this to a friend!
From the HamIV manual (their emphasis):

ALLOW A FEW SECONDS OR THE ROTOR TO COAST DOWN. Then re-engage the brake wedge by releasing the "Brake Release" (middle) lever.
 
Hit the Brakes  
by K0CBA on April 24, 2014 Mail this to a friend!
Idiom Press makes the EZ Rotor control. It is a great rotor control add on and along with 'point and shoot' it be set up to 'auto-delay' engaging the brake. Truly a slick little gadget.
 
RE: Hit the Brakes  
by AA4PB on April 24, 2014 Mail this to a friend!
I'm still using my Heathkit HD-1780 rotor controller that I built in 1992. I had to replace the LCD last year. I found the part on Ebay.
 
RE: Hit the Brakes  
by K6AER on April 24, 2014 Mail this to a friend!
This reminds me of an article about double clutching your 60's Jag XKE.

If you are going to use an old rotor design understand how it works. Wait for the directional indicator to stop moving. Then release the brake. Now in old rotor design there are a limited number of notches available on the housing. The rotor may flop around until one of the notches aligns with the brake wedge. Don’t worry no one makes a beam that sharp in beam width.

Most modern rotor designs use a worm drives and slow down automatically when they arrive at the preset. The worm drive acts as a break for it is a right angle drive.

I would argue the stopping torque is no higher than the weather vane torque in a very strong wind. There is a torque limit to a shear clutch on older rotor systems.

Antenna system such as log periodics place a lot of wind torque on rotor systems. They need an upgrade rotor design.

Most rotor failures are from insufficient specifications. Hams just keep adding antennas until the rotor fails. Then we hear about how bad the rotor design is and not the application.

I have had hams upgrade their antenna from a 204BA to a DB-42 and become disappointed when I tell them they must spend an additional $1500 for a new rotor system.
 
RE: Hit the Brakes  
by AA4PB on April 24, 2014 Mail this to a friend!
One of my biggest complaints with the Hygain rotors is the position pot. It always seems to be the first (and usually the only) thing to go causing the position indicator to jump around.

Does anyone make a rotor that uses a more modern method of position sensor?
 
Hit the Brakes  
by K3OFX on April 24, 2014 Mail this to a friend!
On both of my Hygain rotators, (CDE and HAM IV)the position pot is fixed to the rotator housing. Since the controller meter reads this pot to determine angle, I do not understand how it can ever get misaligned. The pot position tracks the antenna mast, regardless of the brake action. If the antenna wobbles, so does the pot and so will the meter indicated position.
 
RE: Hit the Brakes  
by G3RZP on April 25, 2014 Mail this to a friend!
The pot can certainly get noisy in the Hy-gain rotators. One thing that I found killed the pot was using the tower as a vertical with the beams (a 205BA and a CueDee 4 ele for 15 interlaced with a 4 ele for 10) as top loading - the RF current through the pot burnt it out. I now have .01 mFd ceramic caps bypassing it and a solid flexible connection from the stub mast to the rotator cage.
 
RE: Hit the Brakes  
by K9COX on April 25, 2014 Mail this to a friend!
Calculate how many degrees you need to turn to to go down 3 dB from optimum (half S unit). It is not a big deal.
 
Eliminate the cause and the effect ceases  
by AI2IA on April 25, 2014 Mail this to a friend!
A good old omnidirectional antenna, at least for receive, will make you aware of possible contacts in all directions and needs no rotator brake.

You can miss some very desirable stations when your directional antenna is pointing in the WRONG direction.
 
RE: Eliminate the cause and the effect ceases  
by K6AER on April 25, 2014 Mail this to a friend!
you can also miss very desirable stations with an Omni directional antenna on receive due to the 20 dB increase in noise level. This is a two way street.

The greatest advantage to a beam is the front to back and the front to side rejection. Not the gain.
 
The mind is the best accessory.  
by AI2IA on April 25, 2014 Mail this to a friend!
An omnidirectional receive antenna is a most useful tool in selecting or discovering a desirable station.

An omnidirectional general purpose antenna with a good match is quite effective in the setup of a skilled operator.

Minimizing unwanted signals is one of the skills of an operator thoroughly familiar with his rig and having the knowledge of the functions at his disposal. The goal of every ham should be to acquire these valuable skills which are the very essence of a good radio operator.

To say more in support of these principles would belabor the obvious.
 
RE: The mind is the best accessory.  
by K9MHZ on April 26, 2014 Mail this to a friend!
For anyone who's interested in HF beams and the physics of the layers, earth's mag flux lines, the geometry of the layers wrt your geographic latitude on the globe.....I'd strongly suggest catching Eric, KL7AJ's presentation at Dayton on this topic. If he's not going to be there this year, he does have a book that the League's printed, which describes this in detail.

Especially if you live in a higher latitude on the planet, definitely become informed before laying down a lot of coin for a tower and HF beam system.

As always, Eric does a fabulous job in his writing/presentation style.

Best,
Brad, K9MHZ

 
Hit the Brakes  
by JOHNZ on April 26, 2014 Mail this to a friend!
Virtually all brake delay issues can be solved or greatly reduced by applying a small quantity of commercially available all temperature relative bearing grease to the affected parts.
 
RE: Hit the Brakes  
by W4KVW on April 26, 2014 Mail this to a friend!
I have never had an issue with my Yaesu G-800SDX with (4)yagis on it & 11 foot of mast pipe sticking out the top of the tower.I run it on high speed at all times!

Clayton
W4KVW
 
RE: Hit the Brakes  
by AB4D on April 30, 2014 Mail this to a friend!
What is a brake delay? I can't find one on my Green Heron control box. Maybe it's inside or on the bottom? ;)
 
RE: Hit the Brakes  
by AA4PB on April 30, 2014 Mail this to a friend!
Brake Delay is the amount of time after the power to the motor has been removed until the wedge brake engages. It's in the setup menu rather than a physical adjustment and can be set between 0 and 6 seconds.

 
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