technogc

I'm using a 1000kv motor with a 1000mah 3s lipo. I doesn't seem to really 'want' to get out of my hand, as I've seen on so many youtube videos where people hand launch their planes. A rough guess, I would put the total weight at around 1.2 kg.

The only prop the I'm sure of the dimensions are the ones I broke today - 7.5X4B it says. I believe the others I broke were 9x4.

Would I have more luck with a 6x4 prop and 2200kv motor?





EDIT: I just realised this might be in the wrong section.

jetmech05

Well tell us what happened

technogc

Every time I throw it, it never rises and just falls like a glide.

JollyPopper

My Feedback: (6)

Do you have he motor running full out before the launch or are you trying to run it up after being launched?

600Bob

You should have plenty of RPM and the plane doesn't weigh much. Are you sure you have the prop on the right way? You would be surprised at how many people have had a prop on backwards LOL.

technogc

Yes, full power.

I think so. The last prop I broke was a folding one, and that could really only go on in one way.

2walla

My Feedback: (10)

Ummmm. 1.2 kg is like 2.5 lbs. most of my foamies that i fly with a 1000mah three cell weigh in less than 1 lb. usually closer to 12 oz. what motor are you actually rinning? how many watts does it put out? Saying it is 1000 kv doesnt tell sqauat about its power, just the rpm. If you have the right sized prop on it at a 7x4 it isnt much power for that heavy a plane... It should fly but isnt going to be a ballistic launch out of your hand..

jester_s1

It does sound like you are underpowered. It may be fixable with the motor you currently have though. What kind of plane is it? If it's big for its weight and fairly draggy, the low speed motor turning a big prop is the way to go. But if it's supposed to be a speedy plane, you'll need more RPM.

Looking at Himax's website for a 980kv motor, an 8x4 only pulls 94 watts. The general rule of thumb for powering electric planes is that 50 watts per pound is the minimum for floaty slow flyer type planes, 75 will fly most scale planes decently, 100-125 is needed for aerobats and sport planes, and 150-200 is needed for 3D and speed planes. So given the weight you quoted, your power system probably needs a minimum of 150 watts to fly at all, probably closer to 250 to be able to perform good aerobatics and launch easily. So check the documentation for your motor to see what props will get you there, then look at the amp draw estimate to see if your motor and speed controller can actually handle that size prop. Your flight times will be down into the 4 minute range with the batteries you are using, but if your power system is up to the task of giving you 200-250 watts it will at least get you flying.

technogc

It's an AXON equivalent by Experimental Airlines. I left off the swept fuselage tubes and slightly different construction overall. Thanks for the rest of the info, but the only numbers I know are the ones on the motor (A2212/13T 1000kv) must've threw the booklet away..


Another thing that might be the problem is the motor spinning backwards. I soldered my esc to another plane with landing gear and the planes starting moving back so had to swap some connections. That's something I'll check in the next few days.

JollyPopper

My Feedback: (6)

Unfortunately, the folks who manufacture and/or market these electric motors for us have not agreed on a uniform method of identifying them. If that 2212/13T means what I suspect it means, the motor is WAY too small for a 2 1/2 lb. plane. Somebody made a ton of those gold anoydyzed 2212 motors, which, I think, means 22 mm diameter and 12 mm front to back without the bearing housings on them. The 13T means 13 turns on each segment. Maybe. And the 1,000 kv simply means the motor will turn 1,000 rpm with each volt, so your 1,000 kv motor turns 12,000 rpm on 12 volts. If you buy a motor designated by physical size only, I would suggest a motor somewhere in the 30 mm range on both dimensions, meaning 30 mm plus or minus long and 30 mm plus or minus diameter. I think. Folks with more experience with these motors can probably do better explaining than I can, but I do think a 2212 is too small. By a bunch.

JollyPopper

My Feedback: (6)

Does your motor look like the first picture? That is a 2212. You need something in the range of the second picture, which is a 2836.

2walla

My Feedback: (10)

The recommended setup on an axon is a motor with 300w of maximum power output. Using a 2200mah. 3 cell for about 10 min of casual flying. You have a motor that at best would put out 150w for a few seconds before melting down. That would be with a 10x6 prop if i pulled the right datasheet. Guys have built and flown them with similar sized motors u have but probably a bit lighter build and arent getting much performance.

donnyman

The motor is running backward ......OR ......you have a pusher prop.

JollyPopper

My Feedback: (6)

Guess the OP lost interest in the thread.

technogc

I didn't lose interest! I won't till I get up in the air. I stopped getting email notifications so I thought noone replied. I bought a RTF airplane because I did kind of give up on the scratch building. Maybe it's my building techniques I thought. Since I also had problems taking to the skies with the RTF, Ive decided to go back to the AXON equivalent. I've got some 6x4 props on the way, and plan to fix the damage.

I can only see one picture on your post. I guess my motor does look like the second one, but shorter.

If pusher prop means propeller mounted behind the motor, then I guess it is.

IMO, I've spent too much (£250 conservative estimate) for basically no results.

technogc

My plan going forward is to buy a 2200mah and 2200kv motor. Those are probably the last parts I'll buy if the damn thing doesn't fly..

The problem I face right now is mounting the motor. I can't seem to find anything suitable. Perhaps someone can suggest something diy (I don't have any scrap metal or wood lying around) or items from a shop that would work.

jester_s1

A piece of 1/4 inch aircraft plywood would work for a firewall on that plane. Most of these small motors come with a mount, so you really just need a place to bolt it to.

technogc

Best I could do.

technogc

On the way is a 2826 2200kv and 3300mah lipo, for those who want to stay updated. I fix landing gear onto the plane using the setup described in the original post, and the plane wouldn't even move on carpet at full power.

jester_s1

Isn't that plane supposed to fly on a 2200 mah? The new battery may be too heavy.

Something is binding on your landing gear. It should roll freely no matter what.

technogc

Ok, i weighed the plane without the battery, it came to 800g. With the 2826 motor that could be 900g.

I made a mistake in the other post, I ordered a 4000mah, weighing about 350g which comes to 1.2kg roughly. Ed's plane is a little lighter at around 1.1kg I believe.

The plane moves with a little tug, but there is definitely not enough thrust for it to move around easily. I'm sure it would work better on concrete etc. Also the absence of a tail wheel makes it harder.


My reasoning;

weight - 40 oz
Thrust needed for trainer flying - 90 W / lb
Motor max Amps - 34
Battery can supply 100 A ( 25C * 4 A)
Watts - 11v * 34 = 374 W
374 / 2.5 = 150 W / lb ( max)
so around 125 W / lb if take out all the rounding. prop size not taken into account

What do you think?

jester_s1

You've misunderstood how this works. Motor watts are not a constant thing. The motor will draw as many amps as it needs to turn the prop at the speed that the voltage dictates it has to. So the total watts depend on the prop you are using and the overall quality and effeciency of you electric system. You don't know your watts until you measure the actual voltage and amps of your motor in operation. Looking at the prop chart for your motor will get you close though. So find out what amps your motor is pulling with that prop before deciding that your model is appropriately powered.

technogc

I see. Like you said and also looking at tests on youtube, I think it'll be enough. Anway, thanks to all that helped and I'll let you guys know how it goes.

technogc

Sitrep; I took off the pusher motor configuration and mounted it like normal. The pusher configuration wasn't producing enough thrust. Now the plane can move with the landing gear well. Maiden tomorrow, hopefully.

technogc

Maiden report



It lasted the best 5 seconds ever. I threw it really hard because the landing gear wouldn't work (I'd need a rear wheel). So the throw was really hard and good. I was blinded by the sun, and the plane banked right and crashed after the nose sort of went down. It all happened so quick, I don't know if I reduced the throttle so I could pull up. I do remember pulling the elevator up as well. But I didn't really check if the servo was moving in the right direction (I did on the ailerons), but I don't think that was the problem otherwise I'd have expected it to dive quicker.


I have a question about the CG. It it at the centre of the wing and the wing is about a quarter of the way back on the fuselage. Is this OK?


The damage level on the plane is low with a broken prop (I have 7 more). I can fix it in 10 minutes.