Help with first build, motors too weak/battery too big?

L

Lance W

Member
Hey all,
I am having some troubles getting my first quadcopter off the ground. I am using these parts from hobby king:
MultiWii NanoWii ATmega32U4 Micro Flight Controller
TURNIGY Plush 6A /.8bec/6g Speed Controller
hexTronik 5gram Brushless Outrunner 2000kv
GWS Style Propeller 4x2.5
Turnigy 1500mAh 2S 25C Lipoly Battery

The problem is I can't get the quad to lift up even when I have the throttle at max. I am not sure if the motors are not strong enough or if there is something in the code that is keeping the motor speeds low. I noticed when I arm the motors (by bring the throttle stick to minimum and tilting it to the right) they automatically start spinning despite the throttle being at 0.

On the hobbyking page for the motors it says the thrust can be 90+ grams. The battery weights 79 grams and everything else weights a little less. Could I get my quad to fly if I get a smaller battery?

Since this is my first build I figured something like this would happen. Should I bother trying to make this one fly or would it be better to invest my money in another quad and use this as a learning experience?

Thanks
 
I don't have a scale so I don't have an accurate weight. I will post once I get a chance to weigh it. I would estimate it to be around 150 grams.
 

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Lance W said:
I don't have a scale so I don't have an accurate weight. I will post once I get a chance to weigh it. I would estimate it to be around 150 grams.
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I think your motors might be too small, but not sure yet.

Here is a thrust test someone did in the reviews on HK. You want a 2:1 thrust to weight ratio. Looks like that is possible, but I think it might be a little over 150g with the battery. You might need a bigger prop, just don't over-prop it.

First the 10g Brushless and now the 5g, great job UH!!!
I Use 4 of these in my C130 www.link with the 6A Turnigy controllers.
Here are some measured data with various props.
with 2S Lipo:
GWS 3020 prop. 1 amp. ~38g thrust
GWS 3030 prop 1.2 amps, ~44g thrust
GWS 4025 prop 11,000 rpm, 1.4 amps, ~53gr thrust
GWS 4530 prop 9,000 rpm, 1.6 amps, ~62 gr thrust
GWS 4540 prop 1,9 amps, ~65g thrust
GWS 5030 prop 8,950 rpm, 1,83 amps, ~76g thrust
 
Wow! That is one tiny motor! At first glance I thought it was under propped but then I saw it was designed for RC planes which use wings to provide lift. Quads get all their lift from the props. I also noticed that it appears to be a 3 pole motor. It would likely overheat if you put a higher pitch prop on it. I think the 90g+ thrust they claim is extremely optimistic but more telling is the 0 watts of output. With no real "torque" it can't generate the lift necessary to get your quad to fly. On the bright side, you could always take the power pkg. and put it in a 4 engine plane......:)
 
HDtallrider said:
Wow! That is one tiny motor! At first glance I thought it was under propped but then I saw it was designed for RC planes which use wings to provide lift. Quads get all their lift from the props. I also noticed that it appears to be a 3 pole motor. It would likely overheat if you put a higher pitch prop on it. I think the 90g+ thrust they claim is extremely optimistic but more telling is the 0 watts of output. With no real "torque" it can't generate the lift necessary to get your quad to fly. On the bright side, you could always take the power pkg. and put it in a 4 engine plane......:)
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I figure that is the case, but if there is a chance to get it in the air we can try hahha.

Looks like you'll need new motors, and possibly new speed controllers.
 
HDtallrider said:
Wow! That is one tiny motor! At first glance I thought it was under propped but then I saw it was designed for RC planes which use wings to provide lift. Quads get all their lift from the props. I also noticed that it appears to be a 3 pole motor. It would likely overheat if you put a higher pitch prop on it. I think the 90g+ thrust they claim is extremely optimistic but more telling is the 0 watts of output. With no real "torque" it can't generate the lift necessary to get your quad to fly. On the bright side, you could always take the power pkg. and put it in a 4 engine plane......:)
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Hahaha, yeah, some foam, and 4 small servos you can have yourself a nice little park flyer.
 
GJH105775 said:
I figure that is the case, but if there is a chance to get it in the air we can try hahha.

Looks like you'll need new motors, and possibly new speed controllers.
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Ya know......... Using 1/4" dowells and 3/32" basswood sheet to make a small, lighter H copter might work! The dowel's will allow better air flow. Trimming all the power leads, re-soldering them all and mounted close together on the body will trim even more weight. A sub 1000mah battery, experiment with some different props and it just might fly. You can make the frame in a couple hours for just a few dollars. What the heck. I say go for it.
 
HDtallrider said:
Ya know......... Using 1/4" dowells and 3/32" basswood sheet to make a small, lighter H copter might work! The dowel's will allow better air flow. Trimming all the power leads, re-soldering them all and mounted close together on the body will trim even more weight. A sub 1000mah battery, experiment with some different props and it just might fly. You can make the frame in a couple hours for just a few dollars. What the heck. I say go for it.
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I definatly agree haha, DIY frames are teh best, as you can make field repairs and don't have to wait a decade for your parts to take the slow boat from Hong-Kong.
 
Sooooo you guys think it could work if I get a smaller battery, try some props and change the frame around a bit? I used flat wood rather than dowels because I am making this in my apartment with my dremal tool and didn't think I could drill the holes on a curved surface straight down leading to the motors being tilted.
 
Lance W said:
Sooooo you guys think it could work if I get a smaller battery, try some props and change the frame around a bit? I used flat wood rather than dowels because I am making this in my apartment with my dremal tool and didn't think I could drill the holes on a curved surface straight down leading to the motors being tilted.
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Try for the lightest you can do, also what props are you using?

Edit: try a 5''x 3''pitch

Can you post a video of it trying to fly?
 
Lance W said:
Sooooo you guys think it could work if I get a smaller battery, try some props and change the frame around a bit? I used flat wood rather than dowels because I am making this in my apartment with my dremal tool and didn't think I could drill the holes on a curved surface straight down leading to the motors being tilted.
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Here is a video that shows the arm structure I think would work best for you. You can make it either an X or H. My vote is for H. You will have more room for electronics and they fly a bit better. Make sure the wheelbase is square. In other words if your arms are 8" long motor to motor then the body needs to be long enough to give you 8" motor spacing front to back.


Each battery is just over 1 ounce;

http://www.amazon.com/Teenitor-850m...aCanmRL&dpSrc=sims&preST=_AC_UL160_SR160,160_
 
Forgot to mention. Use a square of the basswood to be both a motor mount and bridge between the dowels. You could CA all this together and eliminate the weight of the screws.
 
One more thing. Use nylon bolts and nuts where you can't use glue. Use only 2 to mount your motor. They don't generate enough oomph to need all 4. Use a minimum of everything. Even the battery strap can be trimmed.
 
Im going with not enough thrust for the weight as well...An 8.5mm brushed motor with GWS 5443 sized props can give over 60g of thrust...lol...Im not sure you could lighten that quad enough to lift it and provide enough power to actually fly it with any sort of authority.
 
Also consider you may have enormous prop wash as wide as those arms are..Alot of the thrust you may have is being taken away having to hit so much surface of those arms...It may actually be pushing down on the quad more than its trying to lift...I could be wrong but, i dont usually see arms as wide as those on builds.
 
Lance W said:
Here is a video I recorded today. The quad kind of moves when I try to control the yaw, pitch, or roll.
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I'm going to go with the first thought that the current build is more than the motors can handle. As Mike H. states the very wide arms are a problem as well. The fix is cheap. Small battery, basswood sheet, 1/4" dowel, nylon fasteners, a couple different 4" and 5 " props to try and trim the excess wire. It actually makes for a fun project since you are going to be making a quad using motors not designed for it and making it work. Pretty cool.
 
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