Chute Release

Discussion in 'Recovery' started by Greg Furtman, Aug 17, 2019.

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  1. Feb 2, 2020 #181

    Kelly

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    Igniting blackpowder is easy. A piece of nichrome wire, of the appropriate gauge, will do. You can also solder leads to a small SMT resistor. There are 'bridgeless' igniters made by dipping the ends of a wire pair into a somewhat conductive formula, but these tend to be a bit fussier. Lots of info out there on this topic.
     
  2. Feb 3, 2020 #182

    Greg Furtman

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    I started this thread a while back & one of the intents was to cobble up a system that doesn't use BP. Just like the JLCR.
     
  3. Feb 3, 2020 #183

    ThreeJsDad

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    My apologies for taking a detour. While I am playing with these ideas I am also working on a system that would use a small RC servo. I have a couple I can use for testing. The JLCR does indeed use a servo type system. I am more comfortable working with a servo system as I know those quite well. It is the altimeter side that is giving me pause. Ideally a servo should never be driven by the servo arm so setting the unit is problematic. The trick will be to open the gate or catch to set the unit. The Eggtimer units are ideal since we can control the duration of the pulse.

    This whole thing would be stupid simple to set up with a RC unit !!!!!

    I guess I need to get the altimeter and see how it moves the servo as it is powered up.
     
  4. Feb 3, 2020 #184

    Greg Furtman

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    No problem on the detour. I meander myself. :rolleyes: One thing about not using BP is that young rocketeers could build & use this. See post #37 in this thread.
     
  5. Feb 3, 2020 #185

    ThreeJsDad

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    I just sent you a PM and I am completely on board. This may sound crazy but I really trust the micro servos that are currently available. I have seen a RC glider go into the ground at ballistic speeds to where the airframe was a total loss but the servos were all functional. (The pilot launched without turning the plane one.....OUCH)
     
  6. Feb 3, 2020 #186

    Greg Furtman

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    So you are going to have an altimeter like the Eggtimer Quantum (I built two of them, accessing it via wi-fi on my phone is cool) somehow trip the servo?
     
  7. Feb 3, 2020 #187

    ebruce1361

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    @ThreeJsDad That is indeed a simple and proven system. If I may suggest, don't rely on the quality of the cutting edge from grinding a hole because when the charge goes off, there will be a shockwave that could momentarily change the dimensions of your tubes and you could end up with the cutting edges misaligned (like a pair of scissors with a loose joint in the middle so the blades are separated a short distance and whatever you're cutting just flops between the blades). Honestly, if you run the cord through the tubes right alongside the Christmas bulb, the blast alone should be able to sever the cord just from the heat and pressure. If testing proves otherwise, you could also try incorporating an X-Acto knife blade to act like a guillotine to cut the cord as the tubes separate.

    Also, if you use this method of cord cutting, be sure to consider potential damage to your parachute. If the tubes with the Christmas bulb are alongside the parachute bundle, you run the risk of burning the canopy. If you want to go with that arrangement, maybe having a nomex blanket wrapped around the parachute or a deployment bag would be ideal.
     
  8. Feb 3, 2020 #188

    ThreeJsDad

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    Yup, the mechanical portion is not really difficult to sort out. The key to the release side is to keep the tension off the servo. Using something like a sear or a notched cam is what I am kicking around right now. Systems like this have been used for many years in RC Aerotowing. Very little of the load is actually on the servo so it can move easily to activate the release.

    In theory, if we turn a micro servo in a tiny motor and gear box but removing the board and the stop on the collar we could activate it with any altimeter that can fire an e-match. As long as the altimeter will energize the servo long enough to rotate far enough to trigger the release. Instead of the output voltage firing an e-match it will turn our tiny motor.

    I will work on a unit and when I have one I will forward it to someone who wants to do some ground testing. It would be cool if they have different altimeters to test it on.
     
  9. Feb 3, 2020 #189

    Greg Furtman

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    I just checked my Quantum User Guide and it says this.

    "Deployment channels’ on-time can be set from 1-9 secs… great for hot-wire non-pyro deployments "
    Also, the Quantum uses a 2S.7.4v LiPo battery.
     
  10. Feb 3, 2020 #190

    ThreeJsDad

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    Thanks, I have developed my idea even further based on something Wallace posted early on in this thread. It is even simpler to set up and should be even more reliable. Wallace posted a system he uses where he drilled out a nylon bushing. I made a tube that will hold a simple ignition source with the burn chord running 90deg to the ignition source. The difference is I will be using a braided fishing line for my burn chord and attach the elastic band to either side. Braided fishing line is made from Spectra and Spectra is just HDPE. HDPE has a very low melting point with out every catching fire. Unlike nylon (regular fishing line) it dos not ball up when melted. Even 20lb test in a braided line is very thin and will melt quite easily.

    I may even cut a slit in the tube so I can bundle the chute and then simply slip the unit into the bundle. I plan to make a small nomex cover that can velcro over the unit after it is in the bundle. I will try to have a prototype to play with this evening and shoot some pics.
     
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  11. Feb 3, 2020 #191

    ThreeJsDad

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    So I will send you one to test and I will test one on a Quark when I get it built. There is no doubt the Quantum would work. Do you know what the output voltage is?
     
  12. Feb 3, 2020 #192

    Greg Furtman

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    No clue. This would ne a Cris Erving question.
     
  13. Feb 3, 2020 #193

    ThreeJsDad

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    I am presuming it is servo safe since they mention using servos with the Quantum. I have servos in my box that will give 11oz of torque at 3.7vt,that should be plenty for what I have in mind.
     
  14. Feb 3, 2020 #194

    Greg Furtman

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    The LiPo battery is 7.4v. Will that work with the servo?
     
  15. Feb 3, 2020 #195

    ThreeJsDad

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    That should not be an issue, there are also HV servos for running on higher voltages. My goal is to have ti run on a 1S so 3.7V. They are just so easy to charge because there is no need for balance charger. I really need to shoot some pics of my Lipo charging system. I even rewired my head lamp for 1S, it was designed for 2 AAA batteries.
     
  16. Feb 4, 2020 #196

    Kelly

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    \
    I'm not familiar with this mode of operation of a servo. I thought these these required a PWM signal to operate. You seem to be describing a mode where just a constant voltage will do something useful. Can you elaborate on this?
     
  17. Feb 4, 2020 #197

    Kelly

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    Instead of a servo or pyro activation, I've thought about using a micro solenoid, maybe something like this: https://www.adafruit.com/product/2776
    It draws an amp (more or less, depending on voltage), so should be drivable directly from the altimeter output. There's no gearing so you don't get the same force you would from a servo, but it still might be useable. Any thoughts? Maybe I'll pick one up and play with it a bit.
     
  18. Feb 4, 2020 #198

    ThreeJsDad

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    It is a hack that is not for the faint of heart. You need to open up the servo and remove some stuff. First thing to do is remove the tiny stop at the top of the gear train. It will be on the gear that is right below the output shaft. It will be a small projection on the gear. This is what stops the servo travel at it's max throws. The next step is to remove the control board. You will now run two wires directly to the motor. Close up the servo and you now have a tiny high torque low speed motor system. This is really not useful in the RC community but can be handy in other applications.....
     
  19. Feb 4, 2020 #199

    ThreeJsDad

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    That is perfect !!!! It solves one of the things I have been concerned about. I was concerned about the initial "hook up" of the release. Not wiring it to the alt but when the containment unit is snapped shut. That little bugger solves my concerns. I think I could get one of those to work with a Quark. I will be ordering a couple of those !!!
     
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  20. Feb 4, 2020 #200

    Charles_McG

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    Sparkfun has a servo trigger that could work, too.
     
  21. Feb 5, 2020 #201

    curtisheisey

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    You have to be careful about solenoids - they cannot tolerate much lateral force. You could be trying to pull a latch, but it could bind from the side s-l1600.jpg .

    There are some nice solenoid drivers out there based on TI DRV101, 103, 110 chips. http://www.ti.com/general/docs/supp...d=26&gotoUrl=http://www.ti.com/lit/gpn/drv101

    https://www.ebay.com/itm/DRV103-PWM-Low-Side-Solenoid-Valve-Driver/113708693784
     
  22. Feb 5, 2020 #202

    ThreeJsDad

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    I have handled and worked with more servos than I care to remember and you are so right. Many of the newer once are running a bearing on the output shaft but I would never try to do what you described !!! Basically I have looking at a secondary latch that takes the primary load and servo or solenoid simply releases that mechanism.

    I miss read sorry..... I can't imagine a solenoid being even as tolerant as a servo.
     
    Last edited: Feb 5, 2020
  23. Feb 5, 2020 #203

    Kelly

    Kelly

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    I understand about the lateral load. You would need a well-designed mechanical system to manage this.
    What would be the benefit of using a driver, as opposed to just using an altimeter output designed to fire an initiator (and capable of putting out battery voltage at several amps)?
     
  24. Feb 5, 2020 #204

    ThreeJsDad

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    I have been looking at stuff like the releases for RC Aerotowing, Old school crossbow trigger systems and other sear type triggers.
     
  25. Feb 8, 2020 #205

    billdz

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    It's a 2S LiPo. I've been testing with 12 lb. Trilene fishing line, so far the line breaks every time. I may try it at a launch tomorrow.

    Still a mystery why the 2mm elastic cord is no longer reliably breaking. It's been stored in an air conditioned room. But for some reason it has become more heat resistant.
     
  26. Feb 10, 2020 #206

    billdz

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    Worked perfectly with the fishing line. Only problem is that the fishing line is very thin and harder to work with than the 2mm elastic cord.
     
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