F1A hook reed switch and other hook related items

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    From an email from Dave Edmonson.

    He has a model equiped with reed switches on the tow hook. Many flyers have had this problem– the model is flying well, the rudder adjustment is made to open (widen) the glide circle and behold on the next flight the timer does not start. This same failure mode happens with the mechanical timer starts as well. Good thing for the “fly away logic” on our e-timers if we launched in good air.

    Reducing the glide rudder decreases the amount the hook body swings back and so the critical point is reached that the separation between the magnite and the switch is not great enough for the switch to open. Here are some of the ways I’ve used to solve this problem.
    1. Relocate the magnet; On the standard M&K (and similar designs) the kevlar tread / epoxy can be cut with a razor and carefuly peeled away. Rotate the magnet and use thick CA to refasten. Movement is small- can be frustrating when it is not right. Pierre Brun designed and makes a niffty machined piece that allows the magnet to be moved via a set screw.

    2. Biase the hook body backward by adjusting the forward stop screw and re-adjusting the straight tow rudder (at the rudder control arm turn buckle). It does not take much, .015-.025 inch but it does change the hook position. Make sure the switch works in the forward (straight tow) position.

    3. Drill a new hole to reposition the rudder line to the zoom lever- move the new hole closer to the pivot point. Requires the hook to swing back more to get the same rudder deflection. It also decrease the zoom rudder during launch but a bit more zoom rudder adjust can be made.

    4. Similar to shorter zoom rudder lever attach point, lengthen the rudder control arm.

    5. Replace the reed switches with the small cherry micro-switch. I orginally used these mechanical switches and had no problems, I switched to the reeds when Stamov and M&K showed thier use. The advantage I thought was they were water proof. I “shorted” a switch on a test flight that landed in a shallow puddle just before the first round at Palm Bay years ago. Other than landing in water, the micro switched seem a tolerate to water as the rest of the timer system. Perhaps I fly in mostly dry Lost Hills– . I also could not figure out a clever away to use the reed switch on the re-latching hook development program. Rene Limberger did use reed switches on his Stamof hook based reltaching hook, Victor, I now offers a similar reed switched relatching hook (ie removed the strain gage)- dumbed the “Stupid hook”.

    It tooked me some time to resolve that the shock from the hook relatch would cause a premature bunt start and the following exciting sky writing. This is what “swtich bounce” is all about and once under stood is not a problem. This was dicussed in SEN several years ago.

    The limited range of the reed switch is its biggest draw back. I have slowly replaced the reeds with the micro switches. It is especial difficult for me to get a set up on F1H with its small hook swing. It is also nice to put your ear to the fuselage and hear the switch “clicking”. I do note that M&K on the the new impluse hook design used 2 reed switches and one push pad switch. It does not look easly to replace these so I’ll continue to be using them.

    The black magic is equiped to use Hall effect switches. I have never used them but they seem to be as positional sensitive to use as the reed switches and required an addition power wire to be used.

    Vasily designed and produce a mechanism that swings the magnet away at unlatch but I have seen several people have problems with it– seems like un-needed complexity to me.

    General info, both the the M&K and Stamof hook forward switches are wired the same, however the latch switched are wired opposite opposite. Roger M on the Black Magic has “check” box in the “More” screen to toggle between these two wiring configurations.

    One last note, be sure to keep iron particles cleaned from the magnets. Lee Hines after returning from a New Zealand- Austrilia trip was having the ocasional “no-start” problem. After I pointed out the particles that had accumulated, Lee cleaned them off, the problem went away.

    Thermals, JIM


    Hello Jim

    I meant to say that I am using Hall effect switches. I consider that to be a magnetic switch, not a reed.

    But like you say, the problem is the same.

    I have not had problems with the small micro switches, and don’t like the added complexity of the Hall effect switches.

    Roger Morrell

    The reason I provide the Hall effect switch options is because they have the advantage of no moving parts and are less susecptible to environment – physical damage, dust and water. The disadvantage is that the have an extra wire. They share with reed switches that they are harder to set up than mechanical switches.

    I believe that both M&K and Stamov chose reed switches because they felt they are more reliable than mechanical switches. This may be due to the quality of the mechanical switches that were available to them 15 years ago.

    Roger Morrell


    I’ve used micro switch from the time of the first Bauer timer (1981 ?), through Koster’s Van Wallene, Muticlass, BMT and probably others and never had a problem. You can get them sealed, unsealed, and in various colours to meet your need.

    Roger Morrell

    One thing that I forgot to say was that it is very important that the micro switches be of good quality and designed for low current operation. This means that the should have gold contacts. On the Magic Timers and any other electronic timer the current flowing through the switch is only a few milli amps. For some other applications, including the reset button on Black Magic I use a simple push button switch. Some people have tried using these or some thing like them as hook switches. They are not appropriate. The will not make a good enough contact. The lever on the typical micro switch ensure that a good mechanical connection is make between the timer and hook.

    Roger Morrell

    Lee Hines

    A recent problem had a solution I think may be cogent to this discussion.
    On a new F1A setup with a new Black Magic timer and Hall effect switches,
    I could not get any bunt functions to occur during initial test glides. 😮
    I showed it to Roger Morrell yesterday, who reset the front magnet back
    ever so slightly away from the Hall switch…and it worked properly. 😀
    I had looked at the setup and compared to my other identical bunt timer installations, but I could not visually tell that was the problem area.
    When I asked him, he stated that some magnets have different values
    that require gap adjusting ❗
    [Who knew? ❓ ]
    Apparently the magnet was too close to allow the switch to recognise when
    the hook was back, hence, would not know to start bunt function steps.
    Maybe some of you learned ones knew this, but I hope this finds those with the ‘need to know’. 8)



    General Lee,

    I read you said “I could not get any bunt functions to occur during initial test glides.” Wow, you get your models to bunt when test gliding ! Doesn’t this hurt the pup ?


    Even more dramatic than bunt test glides, is to be flying in the wind, and have the model in a down wind dive that unlatches the hook, and bunts straight in with maximum velocity! This is not a switch problem.

    But on the model that I have had switch problems, found that I was adjusting the wrong hall effect switch. The switch that starts the program upon release was passing by the sensor, it would start the program most of the time, but would screw up ALWAYS on my first big contest flight.

    So after setting the switch to remain in contact with the hall sensor after launch, that seemed to take care of the problem.

    Now if I could keep these batteries in these stupid Palm Pilots from going dead prior to losing the program.

    I have about 8 of these Black Magic timers, and 4 Palm Pilots, and 3 programming cables. Some of the cables work on some of the models, and not others. Some of the Palmpilots throw out error messages after having the program beamed. Some just don’t work under any circumstance. Most recently a 2 servo unit will delete part of the launch parameters, and I can’t even get at these functions. Boy you can really waste a lot of time trying to get these units running. Then I think some of the parameters to set don’t even work, like the launch release settings. I program these out almost instantaneously just to make sure that they don’t have an effect. My next foray into the program is going to set up a program with 10 second steps so that I can see what each step is doing, and whether it is really doing it? There needs to be a better programming connector that actually works, like on some of the new digital cameras.

    When you finally get a model flying decent with one of the electronic timers, and only need to change the DT time, then they are great.

    Peter Brocks


    I do not understand why some electronic gliders use Hall effect switches that have to be powered with an extra line and are also susceptible to malfunction by magnetic dirt. Is a subminiature Cherry switch not much simpler and accurate?

    From my F1E experience I know that magnets of different composition have different magnetc values (Gauss). I built me a Gaussmeter which shows that a Neodymium magnet is stronger than an AlNiCo magnet. Also, an AlNiCo magnet will lose its remanence (magnetization) over time while a Neodymium magnet does not unless you heat it up.




    I simpathise with your problems. I use BlackMagic timers in some models but find the Multiclass timers more reliable. These were originally produced in Denmark and the development sponsored by F1C flyers (Koster and Nyhegn) and so tend to be ultra reliable. The main difference with ALL other timers is that the programs (ie servo times and angles) are held in the timer and the interface just interogates the parameters. This way you are not using any software in the interface unit to send data to the timer and even just dissconnecting the cable will ensure any changes are loaded. I have never had any data errors using this timer. The big downsides are the timer’s size, weight and cost.

    The timer is now made by Christophe Bachman in Swizerland but it seems harder to influence the development than before. In comparison, the nice thing about the BalckMagic timer is that the development is continuing to follow the idea of the flyers wherever practical.

    I’ve never used Hall effect switches mainly because of the concerns over battery life. With Li-Poly batteries this problem diminishes but I now read about the adjustments problems. Instead I’ve used some very high quality switches (sealed, waterproof) and some less so including the Cherry types and all have worked OK. Lord Magic’s comments about gold contacts are important however.

    Lee Hines

    @CHE wrote:

    General Lee,

    I read you said “I could not get any bunt functions to occur during initial test glides.” Wow, you get your models to bunt when test gliding ! Doesn’t this hurt the pup ?

    Well CHE, I did NOT handglide the ‘pup’ UNTIL I ran the functions thru
    to the glide step.
    But you knew that, oh Literal one. 😛

    Roger Morrell


    the choice of switches is the made by the individual flyer. There are 3 kinds in common use and all have thier plusses and minuses.

    Setting up a reed or hall effect has the problems Llee mentioned. You have to get the magmet in the right place. It turned out in his case it was just on the borderline of working or not.

    A halle effect does require power but this is not really a concern with modern batteries. It has the advantage of having no physical contacts in the switch to get damaged.

    Mechanical aka Micro switches must be the kind for low voltage low current with gold contacts.

    On the connector and versions of Pilot

    the Palm IIIex is clearly the best .

    To work with a M series palm the timer must have a restitor. there are some timers without that resistor and I will fir it to any 2004 or later timer that does not have it. Check with me first.

    the Little magic timers as used by a number of people including Stephanchuk and Burdov have a more robust connector. The is a proto type of the 2008 model Black magic undergoing field testing that has this connector. This connector is also used for charging.

    I have considered a number of different devices for programming the timer, including Pocket PC, Lap tops, Nintendo, and of all of these the palm is still the most cost effective and the most robust for field use. We are looking at using an IR connection to ‘solve’ the cable problem.

    Many of the cable problems are caused by people making thier own cabklee with bad solder joints. If required Pierr Brun will make customer cable for people that do not have the DB9 connectors in the middle. Typically Pierre does very good work.

    I have considered making a programmer box similar to that used by the multiclass timer, but a device with a more modern intrface would be rougly equivalent to baking my own PDA – clearly more expensive that using a off the self or off e-bay product.

    The multiclass has avery simpler user interafce whjen compared witht he Palm and that is always a possibility.

    Reading about the issues that people have is very important to me. People have been using Black magic timers for about 15 years now and most of the features are as the result of user feed back. We use the timers in a vary harsh environment, often with wiring that is not up to the standards of construction observed in the restof of the airplane and sometimes with people not really undertsanding how to get the best out of them. But they still work pretty well. The magic timer program is aimed at resolving these issues.

    Roger Morrell

    The Magic Timer person magictimer@yahoo.com


    I read from the timer magician that :-

    “I have considered a number of different devices for programming the timer, including Pocket PC, Lap tops, Nintendo”

    Wow ! What a great idea ! Can we have a Wii interface that allows you bunt perfectly each time and to stear your model to the thermal and, and, and ………………..

    Nurse arrives to sedate CHE.

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