[secant0give]

I like your insights Drew and I love those those rules of thumb!! Never actually thaught of it in those terms.
I particularly like this one

Thrust = Pitch X Diameter^3 X RPM^2 X 10^-10 oz.

I wonder why it's diameter instead of the radius that's cubed?? two blades perhaps??

I wonder how close an aproximation it actually is ?

Definatly going to write those up on the workshop wall

[samste]

Thrust = Pitch X Diameter^3 X RPM^2 X 10^-10 oz.

ummm ummm , Ok i Understand now too Easy

Heres my conversion of the above

Big Motor , Big Lipo ,Fast Prop , No Problem

[smuzz]

Here's another thrust calculation I thought of this morning ...

Power = Force * velocity (http://en.wikipedia.org/wiki/Power_(physics))

so Force = Power/velocity

The "Force" is the thrust, obviously. We get a power reading from a Wattmeter in a static test and remove about 15% of the reading because most brushless motors are roughly 85% efficient. Then estimate the velocity using the propeller/fan pitch and rpm (or measure the efflux speed in a static test if you have an anemometer) and there you go, a thrust estimate.

[gbanger]

Naa... not buying it, I like Steve's formula better.

[robair]

Gday Gazz

Yeh I like the samste calculation too. The KevJ calc is even easier, if the batt/esc/motor combo rips the firewall out all is good.

Cheers
Rob B

[wingtipper]

LOL !!!! . I see i'm not the only one here who never had a girlfriend in high school . too funny .

[Skidz]

Guy's, this thread is getting too technical (yawn ).

I think the way most of us do it is:

1. Buy the wrong size motor first up (despite thinking it is the correct motor).
2. Buy and fit the wrong pitch and size prop (even though you thought it was also correct)
3. Buy a range of props and keep swapping until it [almost] works.
4. Buy another motor (refer #1)
5. Buy another ESC as the one you have is now under-rated for your new motor.
6. Buy another plane to suit the underpowered motor and ESC you have sitting around (props now on hand).
7. Dang it. Buy more servos for the new (smaller plane).
8. Buy more batteries for both planes.

Notice that every action starts with "Buy". Only following this time proven technique can you be deemed experienced. So my formula is: Experience = Number of planes and Poverty is proportional to the number of planes. Therefore, by transposition, Experience = Poverty.

If you don't believe me, check out the signature list under our experienced plane pilots .

[wingtipper]

^^^^^^ i like that one hahaha .

another question , whats the difference between EPO and EPP ?? is there anymore ?

[smuzz]

Guy's, this thread is getting too technical (yawn).

You'd best get out of the kitchen then!

[robair]

G'day All

I won't comment as to whether this page is getting too technical, however, I will say it is getting pretty funny. Dave your description of initial motor prop etc selection brings back memories.
Very recent memories.....

Cheers
Rob B

[Skidz]

Technical is good. I was even trying to work out the maths behind the formulas. Just having a smile at the extreme science behind all this. Complex little beasties these electric RC planes.

[Too Drunk to Fly]

Just curious, what plane which is fun to fly(sport type plane) would be a good GoPro platform?

I don't have a GoPro yet, so not even sure what size plane to look for. I'm actually quite broke at the moment so these are just dreams for my future plans.

No HobbyKing suggestions please.

[gbanger]

The GoPro is a little smaller than most modern digital cameras but not by a lot, so I would suggest that a good flying platform would have to be at least a 50 size aircraft anything smaller would have issues with the added weight, irrespective of how close to the C of G you get it!
Gazz

[Too Drunk to Fly]

maybe this could be a goer...

http://www.austars-model.com/dispdet.php...1431325813

[brotherblonde]

Aaron, I use this camera & I can highly recommend it. The lens area swivels about 30' but I modified it to swivel 90'. That way it can sit flat on the a/c (and heli in my case) and the lens still points forwards, creating very little drag. Also it's VERY light!

http://www.chinavasion.com/sports-action...camcorder/

[Too Drunk to Fly]

Interesting Andrew, thanks.

[kizza42]

Why no Hobbyking? If you want to do decent airborne photography, you don't want a prop up front ruining the footage.

An appropriately powered Skyfun would make an excellent/cheap platform.

[secant0give]

For a camera plane Kierans right you don't want a prop in the camera's field of view

Either a pusher or a twin is ideal or if you use a tractor you could mount the camera on the wing far enough out so it doesn't see the prop and put a weight on the other wing to balance it out. I've done this before and it works quite well.

One thing you need to do is reduce vibration as much as possible 'cause this will mess with your picture. Balancing your props very carefully and using a Low KV motor to keep the revs down will also help.

[Too Drunk to Fly]

>>An appropriately powered Skyfun would make an excellent/cheap platform.<<

Really? I thought it would have been too small and light to carry something like a GoPro....


Thanks guys, some thought for next years purchase.

[secant0give]

I think "appropriately powered" is the key word here.
You would want to use the go pro with out the heavy case that it comes with and mount it like this see pics below


These Pictures were coppied from Trappy's face book page.
He's come up with a very good solution for mounting GoPros so why reinvent the wheel I reckon.

here's a link http://www.facebook.com/teamblacksheep

His air frame is not bad either it's called a ritewing Zepher

http://fpvlab.com/forums/showthread.php?...ild-Manual



note he uses a separate lo-res camera for the video link used for FPV and simultaneously does onboard recording with the go-pro.
you can see the two camera's mounted side by side in the nose.

Or you could use something like this which is quite similar. with the addition of a trappy style mount for the go-pro
http://forum.rcflyingclub.com/showthread.php?tid=305&highlight=fpv+wing

[robair]

Gday Jason

Quickly off topic, sort of. You are familiar with the airfoil of the 2m cores that you sourced for us.
I have done some prelim calcs however would like your thoughts on my plan. I intend to sweep the wings at a 33 degree angle, is that going to aerodynamically stuff things up? By my basic calcs I say no however will need some wing fences to stop spanwise laminar flow.
What do you think?

Cheers
Rob B

[secant0give]

Gday Jason

Quickly off topic, sort of. You are familiar with the airfoil of the 2m cores that you sourced for us.
I have done some prelim calcs however would like your thoughts on my plan. I intend to sweep the wings at a 33 degree angle, is that going to aerodynamically stuff things up? By my basic calcs I say no however will need some wing fences to stop spanwise laminar flow.
What do you think?

Cheers
Rob B

I can't see it being a problem at all, firstly your not changing the angle of sweep by that much.
The foil changes from root to tip any way, that's the main thing with those foils we are aiming for a tip section with a less savage stall, (ie can opperate at a higher angle of attack) than the root and I don't think that will change 'cause what ever slight change you do to the root profile you will also be doing to the tip profile.

Also it won't change the pitching moment because any change in shape of the foil caused by sweeping more or less for that matter will be symmetrical, same change on the top as on the bottom so no problem there either i wouldn't think.

As for changing the efficiency of the foil as a whole, I don't think you'd notice unless you did some very careful wind tunnel testing. it could even get better here but probably not by much.

For what you want to do with it I think it will make a very nice choice of foil.

I'm not sure you will need fences to stop span wise flow, but they might be an improvement, again weather it would be enough to notice it's hard to say?? As long as you have enough lateral area for stability in Yaw it should be fine Id think.

[smuzz]

I think fences would look cool though

[robair]

G'day Jason/ Steve

Thanks for the input.
Jason, this is a very versatile foil from what I am discovering.
The more I think and plan the B2 is getting more achievable.
The only part I haven't really got a solid clue on is the moto turbine install.
I can't duct from the intake position on the real B2 as the fan is going to have to sit right up near the cockpit to fit the B2 shape. Might need to leave the windscreen areas open and chuck a few other cheater holes around. I have got a vague idea as to how I would flatten the efflux duct to make the exit from the "tail".
Steve, I am pretty set on needing wing fences, they will look cool and I think they will offset the extra sweep and help try to keep foil efficiency up.
However I tend to agree with Jason who, if I am reading between the lines correctly, states" Don't worry the wing will be fine".

Cheers
Rob B

[Flying fisho]

Nosed my Trojan into muddy Penrith swamp & motor need a good clean (plus epoxy to fuse lol). Has been suggested to strip motor down & rinse out, then blow dry. Have motor out of plane, cant undo grub screw out of prop adapter (smallest allen key too big). Removed grub screws from front of motor that screw onto shaft. Removed grub screw from rear collet & pulled collet off shaft. Rear of motor & magnets pull approx 4mm over shaft but stops there. Cant figure out how to further pull apart as shaft appears firmly held in motor. Guru guidance requested.

[gbanger]

If you want to drop by my place, I am happy to help you pull it apart Wayne
Once you remove the locking collect on the back of the motor it should pull apart, its probably just catching on one of the bearings. If you give it a gentle tap with a pin punch I'm sure it will come apart.
Gazz

[Flying fisho]

On my way if timing ok

[Too Drunk to Fly]

Use distilled water for cleaning motors (I use this for cleaning telescope mirrors as well, doesn't leave streaks) but it also won't rust as there are no impurities.

[Too Drunk to Fly]

HI guys,

I've got a problem setting up my stryker. I've done everything as per instructions, everything plugged into the right place, settings which should be reversed are reversed, but my elevator is still wrong way 'round. down is up, up is down..... If I reverse this my ailerons start moving. Any ideas?

[kizza42]

Reverse the ail and ele wires and then the reverse the channels on your radio