Succesful "Bit" plane - RC Groups
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Jan 27, 2003, 01:53 PM
Only nerd in the village

Succesful "Bit" plane


Hi Gang

I finally got a chance to fly my bit conversion model this weekend.

The model is a 40cm span Jiglet made from 4mm styrofoam with 1mm carbon fibre wing spars. AUW is 19 grams. Motor is a N-20 (49 cents from BG Micro) and it is direct drive with a 2.5X0.8 GWS prop.

Receiver is fitted with a longer aerial (app. 60cm) and has a mosfet on the motor output. I use the original forw/rev to power a coil actuator. RX is powered by 4 nicads and has the aerial extended by 50cm.

Model climbs nicely under power and I use the turns to maintain altitude. It is VERY easy to fly and will do lazy climbing left hand turns if left on its own. Nice tight figure-8s can be flown and after a bit of practise it is easy to land in my hand. Flying in a 5 badminton courts sized hall I had no range problems at all. Since current draw is app. 0.5amps I get very good duration on a 145mah LiPo cell. Total cost less than USD 25 - pretty good for a fun indoor model. I still need to add a U/C so I can do touch and goes. If I need a bit more punch I can use a U-80 or 2.5x1.0 GWS prop.

Best part is that it is soooo quiet with its direct drive - you can barely hear it.

I have certainly proved to myself that the bit conversion have a place in indoor flight and is a cheap place to start.

Michael
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Jan 27, 2003, 09:05 PM
Foam rules
Thatovalguy's Avatar
Great job, I know that this has got to catch on, it so cheap and not had to do, like the old days when I was a kid, but way better.
Jan 27, 2003, 09:05 PM
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Steve McBride's Avatar
Michael,

Looks and sounds great! I gave up on the bitcharger thread some time ago when it seemed like there was plenty of doubt, but it looks like you have done it well!

I have been pulling my hair out over the proper gear ratio for a 6mm icro car motor, building two stage gearboxes and such - why I never thought about an N-20 HV direct is beyond me, but you have inspired me to give it a try and by golly I seem to have plenty of thrust now! I am using one of the Wal-Mart snow globe cars and it seems to hold up fine without any mods to the circuit. I suppose we will see. Trying it in a Cox electri free flight 'mini sky cruiser' as soon as I get the actuator figured out.

Did you make your own actuator or did you purchase one? I would love to get a detail look at how your actuator works.

Anyway, great job!

Steve M
Jan 27, 2003, 09:12 PM
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Jgardner's Avatar

Geat job


The model is attractive and performs well. What more can we ask for for under $30? I think Graham is right, the mosfet is the key. There are a lot of options using the N20-LV.

I much prefer direct drive, myself. How about a twin whith the car motors and the 2.5X08?

I still have to get out to test mine. I can only hope they do as well.
Jan 27, 2003, 09:16 PM
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Jgardner's Avatar

No mosfet


Steve,

That would be great if the N20 would work directly. Were you using the same GWS prop?

Hey, at $14 for a try, I'll just go down now and try it now.
Jan 27, 2003, 09:18 PM
Foam rules
Thatovalguy's Avatar
I can't wait for my li-poly's to come. Next month at the club meeting I want to sit in the back of the room and when they bring the meeting to order pull the thing out of a box and fly it around to hall we meet in. Of course my plane is smaller than yours, but where we meet is still big enough for a circuit or two. Maybe than I can spark some small electric interest.
Jan 27, 2003, 09:30 PM
Foam rules
Thatovalguy's Avatar
My first flier is using a n20 direct now with a prop I carved of 3" dia. No mod to the rx except add of antenna on 3 - n50 cells. So it will work, you loose a little but do you really need it all? We're not making pylon racers you know, but that could be neat too.
Jan 28, 2003, 03:20 AM
Thats NOT indestructible
j8m8l's Avatar
Cool stuff Michael

That is really great, and i LOVE the tx !!

I have 2 sitting on my desk waiting for my holiday in 2ish weeks

Josh
Jan 28, 2003, 04:29 AM
Sticky Shepherd
Graham Stabler's Avatar
With removable wings this would be a must of lunch time flying.

That's settled it, I gonna built mi self a cheaplet.

All hail the 'pilot.

Graham
Jan 28, 2003, 04:32 AM
Sticky Shepherd
Graham Stabler's Avatar
jgardener,

he meant direct drive as in without a gearbox, I think.
Jan 28, 2003, 09:37 AM
Registered User
Can I get more details on this? I have several Bit cloans laying around and would love to do this. Is the plain scratch built or did you find a toy some where?

Can you give any instructions or input on the rudder mechamism? I am assuming you are using only rudder and it just always climbs a little under full power. Are you using the a bit PCB also? Please describe how you are powering it. Is the motor always on or do you have that on throttle as well?

Very interested in full details.

Thanks!
Kenny
Jan 28, 2003, 09:46 AM
Registered User
Dave Wulff's Avatar
Michales post prompted me to run a few tests this morning.

N20 BK 2.5 OHM, (not shure if this is a HV or LV) GWS 2501 prop DD. Weight w/prop 5.7G, current on 1 Lipoly 450 mah, thrust 9.5G

ToyTronics M20 (HV) GWS 2501 prop DD. Weight w/prop 4.1G, current 625 mah, thrust 12G.

Echarger M20 (LV) GWS 2501 prop DD. Weight w/prop 4.1G, current 1 amp, thrust 14G.

For the current/weight/thrust combination I like the HV M20, but it is an $8 motor. 1 amp is a bit much. I also tried a GWS 2508 prop but currents were barely less.

Also, direct drive, the U80 is alot more prop than the GWS 2501, no numbers yet, but watch the currents.

Dave Wulff
Last edited by Dave Wulff; Feb 08, 2003 at 09:13 AM.
Jan 28, 2003, 10:28 AM
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Jgardner's Avatar

Graham


I was unclear. I have been hoping to both avoid the Mosfet mod and avoid the gearbox. Using the car motor DD would seem to require a very light, very clean design, as the thrust is minimal. Moving to the N20 gets the DD thrust up to a reasonable level.

Dow's first setup could be a good combo. A 19g plane would only be 2X thrust. An alternative might be two of the car motors DD. They would weigh in at about 4g. The blue capped ones from RS for the Zip Zaps do not draw much.
Jan 28, 2003, 11:44 AM
Only nerd in the village
I will answer some of the questions in due time. For now I just want to say that I consider the mosfet mod to be absolutely necessary. Without it the RX will not be able to supply enough juice to a direct drive N-20. Since the fet I used has the same footprint as the transistor it replaced it is a very simple mod. It does require a steady hand and a good soldering iron though.

Michael
Jan 28, 2003, 12:00 PM
Registered User
Steve McBride's Avatar
Oops - I had assumed the MOSFET mod was a requirement for the Bit board due to increases in current draw. I do know that with the 'snow-globe' clone, the motor is powered 'nicely' stock. Enough to drag itself along the workbench on it's belly. This with 3 N-50 nicads. Hope to have my 145 Kokams in soon.

If it's a simple SOT-23 package (current FET package), could you share the part number perhaps? Not a problem doing the removal and replacement here.

Thanks again!

Steve M


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