Need advice about RC options for ultralight paper airframe project

Discussion in 'RC Aircraft & Watercraft' started by liftline, Sep 29, 2010.

  1. schorhr

    schorhr Member

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    haha, true :)

    Try r2hobbies.com
    giantcod.co.uk
    ebay (a little further down on the result page here)

    :)
  2. liftline

    liftline Member

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    Not a lot of surface available for gluing on those little HKing servos and the bottom of the circuit board isn't flat. There is also a gear protruding over one edge, which needs to be kept free from obstructions.There are 4 holes, roughly 1mm dia. at the 4 corners of the servo circuit board. Intended for mounting screws I reckon. Don't have any small screws, and nothing to screw them into on my airframe.

    So, I decided some mounting feet would be nice. I trimmed off the ends of "cocktail toothpicks" to make micro wooden spikes which are wider than the holes at the blunt end. I cut small squares from 3mm cellfoam 88 (basically the stuff disposable coffee cups are made from), put some white glue on the points of the spikes and inserted them into the foam. Model railroading meets model aviation. Instant feet. Seem sturdy enough. The feet can be glued to a mounting board of some kind, maybe sturdy board foam, maybe just a sheet of paper to give a bit more rigidity. The mounting board can in turn be secured to the airframe. Nice and light. The feet can easily be removed if need be. For 6$ worth of foam and toothpicks I figure I can make feet for about another 100 servos. Not that I plan to do that.

    A perfectly awful web cam photo follows of the rig on top of a cigarette lighter sized tape measure. You can sort of make out the spikes, the feet and that gear I mentioned. Sorry about the image quality, but it's too late to dig out the Nikon, the tripod and to corral the pets.:oops: The crash case for the receiver promises to be equally funky.

    I'll see how this works on a mock-up of the rudder over the next few days.

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  3. liftline

    liftline Member

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    Not a lot of surface available for gluing on those little HKing servos and the bottom isn't flat. There is also a gear protruding over one edge, which needs to be kept free from obstructions.There are 4 holes, roughly 1mm dia. at the 4 corners of the servo circuit board. Intended for mounting screws I reckon. Don't have any small screws, and nothing to screw them into on my airframe.

    So, I decided some feet would be nice. I trimmed off the ends of "cocktail toothpicks" to make micro wooden spikes which are wider than the holes at the blunt end. I cut small squares from 3mm cellfoam 88 (basially the stuff disposable coffee cups are made from), put some white glue on the point of the spikes and inserted them into the foam. Instant feet. Seem sturdy enough. The feet can be glued to a mounting board of some kind, maybe sturdy board foam, maybe just a sheet of paper to give a bit more rigidity. The servo can be removed if need be. A perfectly awful photo follows. You can kind of make out the feet, the gear and the spikes. Sorry 'bout the poor image quality - too late to dig out the Nikon, tripod and corral the pets.

    Attached Files:

  4. schorhr

    schorhr Member

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    Yey for webcams! :)

    Well, sounds like a plan. Hopefully you will not have to buy THAT many servos- then I would really consider a diferent hobby :mrgreen:
  5. liftline

    liftline Member

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    It's becoming clear that all the electrical components must be shoved as far forward as possible to meet the center of gravity requirements. The lightest takeoff wt estimate is currently 35.3g and a few grams of additional weight are inevitable. I had hoped 2 servos might located near the cockpit to make push rod connections fairly short. Not going to happen unless I put a bit of lead in the nose. It might come to that.

    Here is the current component placement scheme (subject to change without notice or even rational thought). The desired CG is at the quarter cord of the lower wing (where the first strut connects). Scale is cm. Components in order nose to tail are motor, RX, battery ESC(not shown) and the 3 servos.

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  6. schorhr

    schorhr Member

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    Yes, CG can be tricky, especially ever since the batteries got lighter and old NiCd are obsolete ;-)
    Before adding lead, consider adding a different battery or re-ad the rx encasing, so at least it is for something usefull ;-)
  7. liftline

    liftline Member

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    Serious distractions. Holiday related. A bit of "designers block" too. Sometimes a hobby gets a bit too much like work. The nose section requires a good bit of redesign. The receiver pins intersect with a structural element - and the the pins win. I also need to put an access hatch into the top of the nose for access to the lipo battery. Would be nice to make the RX pins accessible too (things do come loose) but probably not on the prototype. The rudder & elevators push rods are going to be rather long- roughly 20 cm. They will need some guides in the aft fuselage.

    Yes, the RX case will probably be included as ballast in the prototype. It might be a bit lighter to put a bit of lead in the extreme nose, but I'll worry about that at a late date.
  8. schorhr

    schorhr Member

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    Or get rid of the rX pins and solder everything to the board :mrgreen:

    pushrods: Pieces of straws (perhaps those small diameter doubles)?

    Good luck :)
  9. liftline

    liftline Member

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    I've been stalled for a few days with computer problems. :curse: Can't connect to the internet (well, not from home), can't print...so I can't build. Not sure if it's hardware to blame or the OS is corrupt. I'll try repairing or reinstalling the OS (still using XP) but I will need to call in a professional if that doesn't help. At least everything is completely backed-up on DVD! Would hate to have to redesign anything.

    Before things went down I started putting components into fuselage mock-ups. It's tight, but looks like things will work out without resorting to anything drastic. The RX plastic case is back, just to get a bit more weight up front. The motor, RX and battery can all be stacked right on top of each other-right up against the nose "radiator". That keeps the CG where it should be. There's a small hatch built into the faux radiator to access the battery.No need to charge batteries in place! I may enlarge the hatch to allow the RX to slide in and out - sounds good in theory but I'm not sure it's worth the trouble. Had to cut openings in a few structural elements to allow for the connection pins and "wire bundles", but this caused no major issues.

    Those tiny glass beads I bought for use as bearings make excellent music wire guides. If you wrap them in a bit of glue soaked tissue paper they can be glued directly to existing paper elements. The weight added is negligible.

    Update-it's a burst capacitor on the motherboard. Too old (10 yrs!) to be worth fixing,....at least there are a lot of good sales this time of year.
  10. schorhr

    schorhr Member

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    Whoops, did not notice my forum reply notification mail :p

    Computer problems suck. But even more, if you're the one knowing how to solve them... Spent the whole morning doing computer related stuff from fixing a wifi network setting to buying new hardware. Where did my day go?

    Good you can remove the battery :)
    As for the rx- at that price, just get a spare one ^_^ No clue which version it is and if the cheap ones off ebay will be compatible. Hard to tell- but they are not expensive either way.

    Good that you found a nice way for the wire guide!


    Motherboard + Dualcore CPU + Ram -> under $100 <--- new nice system :) (and probably a atx that fits)
  11. liftline

    liftline Member

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    Able to check back in at last. With a new "bare bones" computer that is nonetheless insanely fast compared to my old one. Running Windows 7. First time I've been using an up-to-date operating system in a decade. It works pretty well and handles most of my legacy software well, with just some minor tweaking here and there. Unfortunately, MS has decided to abandon 16 bit applications in W7, so some installers no longer work for me. Looking into software emulation, I would prefer not to have two operating systems on a partitioned drive.

    On the RC front I've built a workable "rack" to house the RX and battery in the nose of the Se5a. Maybe that sturdy plastic RX case is a good idea - not a lot of airframe crush protection that far up front. A motor mount is next on my agenda. Still waiting on that .7 g ESC.
  12. schorhr

    schorhr Member

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    Good news :)

    As for the 16 bit applications, will the Compatibility Mode perhaps solve the issues?
  13. liftline

    liftline Member

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    It appears not. If only the installation programs use 16 bit I may be able to install using an emulator and then run the installed program in 7.

    Now that the good people and logitech have sent me new drivers, I've attached 2 low res logitech photos of the transmitter and battery in the forward fuselage. What you are looking at is the forward section of the fuselage back to cockpit. The battery and most of the RX are housed within a beam that makes up the lower fuselage. The pins of the RX protrude through the beam leaving just enough room for the connectors and wires when the top section of the forward fuselage is bent and glued to the opposite side (forming rough a semi ellipse in cross section). The transmitter is actually held in place by paper spacer (with a few folds to make it springy enough to conform to the space with the beam) that contains a small box for the lipo. The antenna wire comes out the front, which is annoying, but unavoidable, since the motor and it's mounting will occupy the space just forward of the pins. On the lower edge starting just forward of the cockpit you can see the tabs that will be folded over to hold the lower wing in place. You'll notice the fuselage is pretty floppy in torsion - the bulkheads that keep the beam squared up have not been installed in the mock up.

    The servos will probably be mounted just behind the pins, which is pretty close to the center of lift and gives a clear shot back to the rudder and elevators. I'll probably leave the ailerons uncontrolled in the first prototype.

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  14. schorhr

    schorhr Member

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    Looks well planned, I wish my builds would look as tidy :)

    What kind of camera is it btw?
  15. gary101

    gary101 New Member

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    Hello,
    I live in Toronto and the best solution for me would be plans of good flying 3d balsa aircraft. If You have some or know names of models I would be happy if anyone would tell me please.
  16. liftline

    liftline Member

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    Hi, back after a much longer than planned absence!! Real life intrudes so unfairly on hobbies! Big news is that my back ordered speed controller has finally arrived. Along with some extra servos and a few other odds & ends. Not a whole lot of progress while I was waiting for the post.

    Getting everything crammed into the fuselage has proved a lot harder in practice than on paper. The first set of servo mounts were just a bit too bulky - 1 mm really matters! Especially when the plan now calls for 4 servos - 2 for the ailerons seems lighter and more compact than trying to devise a mechanical linkage. Also easier to trim. The new mounts are folded paper sleeves. It's now possible to duplex 2 servos back to back and make the best possible use of what space I have. I really think I have devised a universal mount for the little 1.7 g servos HobbyKing servos. I like the idea the servos aren't actually glued to anything - makes it easy to reuse them.

    The outrunner engine mount competition was won by the team of popsicle stick and epoxy resin glue.
  17. liftline

    liftline Member

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    Just a logitech hang-on-top-of-your-monitor-with-the-bendy-clip. Wish I had a real digital camera handy.
  18. liftline

    liftline Member

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    The Paul Guillows 400-500 series kits are traditional balsa and tissue construction. Amazing to see they are still in production since I built one myself as a kid and it flew pretty well. For a kid built airplane. Labor intensive, but less so than designing from scratch. Check out Hobby King or order direct
    http://www.guillow.com/
  19. schorhr

    schorhr Member

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    Happy new year!
    Sounds like you're back on track... I know real life has some detours once in a while :)

    Yes, the micro stuff allways looks simple on paper. Weight adds up so easily though.

    I'm still waiting for my 3d printer, I am sure I can use it for some neat custom parts... The future is now!
  20. liftline

    liftline Member

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    Next best thing to a Star Trek replicator.


    The new hobby king ESC adds a third pin connector standard to my collection. Comes with nice little connectors I can solder to. If it works it is great value for money.

    The ESC comes with a wiring diagram. Not so the little 2g Hextronik outrunner. Trial and error or is there a better approach?

    Couple of "beer cam" photos...so named because the logitech camera mount gives reasonable closeups when you sling it over the neck of a beer bottle. Is there anything that beer can't improve?

    1 The high tech mounting lug for the motor. The lug fits into the slot of the mount proper (not shown). Is there anything a popsicle stick can't do? Should probably drill some holes to cut weight.

    2 Two servos in their new "shoes." The shoes are light, compact, stable and don't cause the gears to bind. All the above have been issues.

    3 Things are pretty tight in the forward fuselage Just enough room for the two aileron servos mounted inverted right behind the RX box. The offset is needed to get pushrod clearance. The pic shows an old style servo mount but the configuration hasn't changed. The engine mount goes right on top of the RX. The rudder and elevator servos are duplexed right side up on top of the aileron servos. Thank God everything is programmable!

    4 The curved upper part of the forward fuselage covers everything up, cockpit cutout at right.

    5 Forward view, you can make out the battery box slot.

    Happy New Year right back at ya, and may we both live long enough to see my bird take flight!

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