Electric Belite!

Discussion in 'The light stuff area' started by Farfle, Jul 14, 2017.

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  1. Sep 17, 2018 #81

    pictsidhe

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    That spring failure looks like a heat treatment issue. You might want to to consider a top plate on that bolted attachment. That first bolt is going to be a big stress raiser with a small washer.
     
  2. Sep 18, 2018 #82

    proppastie

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    Beautiful welds...but welding on a spring?
     
  3. Sep 20, 2018 #83

    Farfle

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    Yup. Welding on a spring is a no go without some pretty special heat treatment.
     
  4. Sep 21, 2018 #84

    pictsidhe

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    It's not that involved to hear treat a spring. Many, many springs have been heat treated by eye.
     
  5. Sep 21, 2018 #85

    proppastie

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    save weight, get rid of the wheel and put 1" thk. HDPE skid. One of those plastic drums should give you a lifetime supply.
     
  6. Sep 21, 2018 #86

    pictsidhe

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    Kitchen chop boards are a good source of HDPE and they come in other colours. There's also some plumbing pipe. The black underground supply stuff is PE but rather thin in the US. The crimp fitting PEX stuff may be worth trying. it's crosslinked so you can't heat form it, though.
    I'm considering one of those scooter wheels for my 103. The 8x2 ones are a bit heavy for my liking, so I'll likely go for the 6x2, unless I need tail ballast...
     
  7. Sep 21, 2018 #87

    Farfle

    Farfle

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    This guy is a 6x1 scooter wheel, but I left the thing open for a bit more tire if i needed. with the wings folded, the tailwheel weight is actually pretty high, so I may go to a 6x2 wheel back there
     
  8. Oct 1, 2018 #88

    Farfle

    Farfle

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    Wings painted, lights and folded-wing tie-down clips are in. Did a runup in the driveway for the first time in 8 months, and it started and ran beautifully! Go figure ;) .

    Will be more than casually following FAA AC 90-89B for the first hours of flight. The phrase "Just fast enough to kill you" comes to mind.

    [video=youtube_share;Ku6MPPVSSu0]https://youtu.be/Ku6MPPVSSu0[/video]
     
  9. Oct 22, 2018 #89

    Farfle

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    Angusnofangus and Tiger Tim like this.
  10. Oct 22, 2018 #90

    lr27

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    As pictsidhe suggested, sink rate is a good way to figure out how much power the plane uses, though the prop will add some drag if it's not spinning, or not spinning fast enough. In case you don't feel like taking the prop off and getting a tow, there's a trick where you spin the prop at just the right speed for zero thrust and then measure. Obviously it's not going to be exactly right, but it ought to be closer. I don't know exactly how they do it. I suppose that, if there's significant axial play in the motor, you could use a couple of micro switches on the back of the shaft hitched to LED's, and then adjust power until it's bouncing back and forth between the front and rear limits.

    For small differences, power required should be roughly proportional to the weight, so that shouldn't be a big problem.

    At least it's a starting point, when evaluating the different choices.

    Another way:

    Let's say the aircraft weighs 600 lbs with pilot and everything. Belite is very coy about the specs. I think an L/D of 10:1 at 35 mph is probably a bit pessimistic for minimum sink, so I'll use that. The requires 5.6 hp. So 8 or 10 hp for level flight, accounting for prop efficiency. Anything else would go toward climb or going faster. So, if you don't mind pointing up at a ridiculous angle, another 20 hp (say 13 thrust horsepower) gives you 715 fpm and a 23 percent grade. Lots depends on the prop, of course. And, in this case, the redrive. All very approximate, too. But I think we can be reasonably sure that 30hp is more than enough unless you live at a significant altitude. My guess is 20 or 25 would be enough, with a good choice of prop, but I could be wrong.
     
  11. Oct 22, 2018 #91

    pictsidhe

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    I came across a flight test of a Belite a few weeks. I think it was powered by a 35hp polini. Climb and minimum sink rate at idle were similar, suggesting level flight on about 1/2 power.
     
  12. Oct 22, 2018 #92

    lr27

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    Hmm.. either the prop was acting as an air brake, or the Belite is even draggier than it looks.
     
  13. Oct 22, 2018 #93

    pictsidhe

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    Hopefully, farfle will give us some good numbers soon.
     
  14. Oct 22, 2018 #94

    Victor Bravo

    Victor Bravo

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    Farfle, when is the first test flight scheduled?

    Trust me, for right now FORGET about all the minimum sink, electrical and mechanical efficiency, how many amperes it takes to accelerate a propeller to any given RPM, what the gravitational force does to mouse turds as they fall from the mouse, etc. All that crap is getting in the way of what you NEED to be thinking about.

    If you hook up your aircraft to a spring scale, run up the motor to full power, and it pulls 150 pounds or more on the fish scale, you are DONE with the scientific testing for the moment, because the airplane should have enough thrust to fly, and then you can take off the nerd hat and put on the test pilot hat.

    The test pilot hat is the ONLY one that will be worn for the first two hours of flight test. No nerd hats allowed once the door closes and you move the throttle forward. If the motor is making enough thrust to get the airplane off the ground and climb, without overheating the components (battery, controller, motor) then that is all you need to know about the power system for the first couple of hours.

    You need to be thinking about stability and control of the airframe, control response, handling qualities, stall recovery, takeoff and landing characteristics, groundloop tendency. You need to be listening for where the gremlins are playing around in your airframe. With an electric motor you will be able to hear the little bastards much better too. What makes clunking or banging noises? What feels like it's vibrating or stretching. Do the controls get more friction when the airplane is in flight, and can you feel the control pushrods scraping on something when there are air loads on them?

    That is the stuff you really need to be concerned about once you know you have enough thrust to fly.
     
    Last edited: Oct 22, 2018
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  15. Oct 22, 2018 #95

    BBerson

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    The thrust tested 280 pounds. (Post 17)
     
  16. Oct 23, 2018 #96

    Farfle

    Farfle

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    I agree. I know it will fly, no question there. The factory polini motor is 38hp claimed (usually meaning cold day sea level downhill with tailwind) this is a legit 45hp at any altitude, any temperature and any battery SOC over 10%. Time to overheat power reduction is just at 3 mins on an 80 degree day, where it drops to 80% power where temperature stabilizes.

    I have done full pack burns at temp-limited power with no appreciable heating of any components other than the motor and controller which are both temperature auto-derating, and the controller, motor and both batteries are on a 4ch EGT gauge that lights up its ID10T light when things get too hot.


    My biggest concerns are in order:

    Severe out-of-rig when the airframe comes under flight loads.

    Taildragger fast taxi handling and potential ground loop.

    Motor reduction drive failure (propeller shaft failing at flange weld, or belt tension loss)

    Other than that, I am pretty confidant in the overall construction, and there appears to be quite a few belites flying without issue.
     
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  17. Oct 30, 2018 #97

    Farfle

    Farfle

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    Making more progress! Fast taxi was a success, and first flight will be today! Headed out to the airfield now!


    [video=youtube_share;wNtRn3qVxCw]https://youtu.be/wNtRn3qVxCw[/video]
     
  18. Oct 31, 2018 #98

    Victor Bravo

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    Farfle, I would like to suggest that doing extended high speed taxi is the wrong thing to do. It puts you in the most dangerous and accident-prone situation for the longest period of time, creating overwhelming odds that you will have a groundloop.

    Just taking off and getting airborne takes five or ten seconds with that aircraft, and landing takes ten or twenty. So by getting air under the tires and just flying, you REDUCE the percentage of time spent in the groundloop-prone phase. Reduce your odds of groundlooping at this stage as much as you can IMHO.

    I'm not saying you need to blast off to 10K MSL on the first test. I'm saying that you cannot groundloop with air under the tires, so make your high speed taxi runs at 5 feet AGL.

    By the way your buddy Aram K has become a part of our EAA chapter in LA, great guy, we're happy to have him. Myself and a couple of others are steering him in the right direction for hangar space, etc. at our airport. When I told him about my HBA posting that warned you to watch battery and component temperatures etc. , Aram told me a little about your knowledge of battery systems... I'm embarrassed now :emb:
     
  19. Oct 31, 2018 #99

    Farfle

    Farfle

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    Woot woot! Still downloading and an official flight review to come, but it did the flying thing, and it did it really well.


    [video=youtube_share;pyBbXtBnoIQ]https://youtu.be/pyBbXtBnoIQ[/video]
     
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  20. Oct 31, 2018 #100

    Farfle

    Farfle

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    And VB, I agree. The fast taxi is risky, but I wanted to get the ground handling solidly under control so that when I came in on first landing (maybe a little crossed up) that I can get it wrestled back to centerline and keep from ground looping at speed rather than just at barely tail-up speed.

    However it was maybe a little un-needed as both landings were really clean, and the winds for the most part behaved for the day. Got a bit turbulent up at pattern altitude but overall it was an amazing day.

    I did have what I can only describe as a dust-devil interaction while taxi-ing to the active, was minding my own business and then a big gust of wind blew thru the cabin from the opposite direction and lifted the downwind wing and spun me around. Was glad I was going slow!
     

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