200g/7oz. dc head pusher - the Micromum - Page 11 - RC Groups
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Aug 15, 2007, 05:06 PM
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JochenK's Avatar
Rob,

'Why does my gyro fly so fast? The data given by Potensky for the Pot-50 disagree a bit with my own measurements. With an APC 7x4 SF prop I've measured 3.9 A at 8400 /min using a 3S-350 mAh battery. If I can trust the information I have for the Himax HC2212-1180, it draws 6.3 A with a 7x4 prop. Assuming this was measured with the same type of prop, your motor's input power is about 60% greater than mine which, at the same efficiency and drag coefficient, should result in a max. speed some 25% higher than mine. That should be noticable.

Your average current draw is about the same as mine. 12 min flight from a 480 mAh battery leads to an average current of 2.4 A. I've calculated my average current as 2.3 A. That's quite alright and indicates that you shouldn't do much of anything about the setup.

Now for the full speed tilt problem. As you told me, when you don't use some speed, the gyro will not climb, and when you use full speed, it will roll to the left. Can you set your roll trim in such a way, that it will compensate the roll tendency during the hand launch and climb phase, and then put it back to the middle position, when you throttle down to cruising speed? And yes, you can pull a bit of pitch to get her climbing, but don't overdo it.

Jochen
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Aug 15, 2007, 05:37 PM
Registered User
I havent used the mixers in my transmitter yet, and i have to check weather i can switch them on and off when it's not working using one of the switches.
And yes i will try handlaunch first with more right trim and a little less throttle (75% should do it, and wait for a little more wind.

P.s. I still have a picture of the "old" completed model.

i allready made a new airframe, and want to test it next sunday.
If the weather permits it.
Aug 16, 2007, 02:33 AM
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JochenK's Avatar
Rob,

good-looking gyro.

If you want less power, use a GWS 7x4 prop (the orange one) instead of the APC. With this prop the current draw of the Pot-50 went down from 3.9 A to 2.8 A and the rpms went up from 8400 /min to 9600 / min. This should reduce your problems.

Jochen
Last edited by JochenK; Aug 16, 2007 at 10:29 AM. Reason: Added some data.
Aug 19, 2007, 12:22 PM
Registered User
I have maidened my new micronum.

changes:
- changed prop graupner slowfly 7x4 to graupner slowfly 6.3x3
- removed the rudder
- used a little more cf and rovings
- use the new pivot-joint
- programmed in a few degrees of right tilt on full throttle

I handlaunched the micronum in the wind and it started making a right turn immediately ( i have programmed a little to much right tilt)
After flying around and a little trimming a made a few circles and landed it very softly. (it did fell over but there was no damage done)
Ofcourse i had someone using my camcorder so i have it on film except for the landing because the tape ended before landing.( i will post it asap).
After reprogramming the right tilt i made a new handlaunch and it was perfect.
No unwanted turn on launch, and easy landings.
The only thing i ad was that i have a little problem flying with head wind. I couldn't get it back because of the wind. Should i have used more downtrim when flying in moderate to strong winds ????

I will post the videos after editing it.

grtzzz,
rob.
Aug 19, 2007, 01:10 PM
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JochenK's Avatar
Rob,

the more wind you have, the more down trim you need. This gives you less lift and you can fly faster without the gyro trying to climb.

Congratulations on your second maiden,

Jochen
Aug 19, 2007, 03:00 PM
Registered User
i have converted the new video, and posted it HERE

I't's still pretty fast, but a lot better with the 6.3 x 3 prop.
I thought of down trim while flying in strong winds, but wanted to ask first before learning the hard way.
The handlaunch on the video wasn't all that good but that was beacause i mixed in way too much right trim on full throttle (4 degrees)
I reduced the right trim setting and the next handlaunch was perfect.

Next time i will try the down trim.
I almost lost the gyro because i couldnīt get it back because of the wind.
It got so far away that i almost lost orientation.
I suppose one is to remove the downtrim at the next handlaunch.

P.s. Everyone at the field loved my (YOUR) model

don't mind the strange moments in the video, this was the cameraman's first capture
Aug 19, 2007, 04:05 PM
Registered User
JochenK's Avatar
Rob,

very good.

I can well remember having one of those fights coming back from downwind, too. After that I started experimenting with down trim to achieve faster flight. And yes, set your trim to normal when you're hand lauching. May be you can slow your Micromum down a bit more by throttling down and trimming up at the same time. Wait for a calm day to try this out.

Have more fun,
Jochen
Aug 19, 2007, 05:47 PM
Closed Account
Hi Rob,
Congratulations on all your effort and hard work, it has certainly paid off. Good video and great flying now you have the Micromum trimmed as you like it. That is certainly a well proven design, one of the classics. Happy landings,
cheers,
Al(T)
Aug 19, 2007, 06:03 PM
Restricted User
StephanB's Avatar
Rob,
congratulations. Your Micromum flies very good. Enjoyed the video, except the disturbing avsmedia "unregistered version" popups. Your Micromum deserves video without that. What's the format of your video source? In case, that it is a apple MOV-file, you could check the net for free "RAD video tools" and download "Binks and Smacker". Together with an actual DivX codec this would allow you to make a much smaller file in AVI-format. This AVI-format will be accepted by Windows movie maker for final editing and the result will be a WMV-format. I could talk you through in case you have original MOV-video format.
Stephan
Aug 20, 2007, 11:24 AM
Registered User
The video was recorded on a dvd by my dvd-recorder on wich i connected my camcorder.
So the output was a VOB/IFO file.
Sep 16, 2007, 02:56 PM
Registered User
Mango's Avatar

My new Micromum


Hi
Here's som pictures of my new Micromum that I made of aluminium.
It is kind of a mix between the old and the newer versions.
I put it together with screws and bolts so it can be disassembled
without being destoyed.
I have tried it out and it flies really well.

Thanks again Jochen....
/Magnus
Sep 16, 2007, 03:55 PM
Registered User
JochenK's Avatar
Magnus,

this is really interesting, something new for me to learn. How much does your Micromum weigh?

Jochen
Sep 16, 2007, 05:23 PM
Registered User
Mango's Avatar

New Micromum


Hi Jochen.

My old Micromum weighs 253g without battery
the new one 314g.
I just got some new Hyperion 800mAh 3cell batterys 70grams
So with this battery the old one weighs 323g and the new one 384g
I tried to make my V8 fly but it crashed about 6times.
The new 2 bladed rotor worked well on my old Micromum
and the old 3 bladed worked well on my V8
but with the new rotor on the new Gyro I just could'nt get it to fly.
So after all the crashes there was not much left of the new fuselage
therefore I built this aluminium fuselage and I will soon try to make
it fly with a 2 blade rotor.
This will make it a bit lighter and also more responsive.

/Magnus
Sep 17, 2007, 11:34 AM
Registered User
JochenK's Avatar
Magnus,

quite amazing. The original Micromum was designed to stay below the 200 g barrier, and with all the bits added in the meantime my V6 and V8 now both weigh 220 g including batteries. And you are flying them with a 50% and 75% higher mass!

And while I think flying the 3-bladed rotor on the v8 airframe may be a bit weird but possible, I wouln't even dare to put the 2-bladed rotor on the v6 airframe, because I'm pretty sure it would go all awry.

What were the reasons for your v8 chrashes?

Jochen
Sep 24, 2007, 04:32 PM
Registered User
I still take me micronum to the field everytime i go there.
It's amazing how nice it flies, and landings are sooooo soft.
I changed a few settings on the transmitter, and it is so stable i don't think it can get any better....

Or can it ??????????

Who knows.


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