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got a question about motor and prop

buzzbomb

I know nothing!
#21
@skymaster. Just a thought. It wouldn't be as accurate as an electronic measurement, but you could DIY a simple rig and get a good guesstimate of what configuration delivers the most thrust.

You could mount the thrust tube to a long dowel and attach the dowel to a weight. Put it on a scale and get a static weight. Then, while holding it steady, fire up the motors while it's still on the scale. Whichever configuration creates the greatest difference between static and running weight would be the one creating the most thrust.

It's just an idea I thought might help. :)
 

Wildthing

Well-known member
#23
You could build a vertical thrust test tube like on a tripod stand of some sort, then secure it to the top of a scale. Have the motors pushing down, zero out the scale and fire it up.
 

BATTLEAXE

Well-known member
#24
If there was a way to hang it from a fishing scale you may get some kind of reading difference between the two. Amp and voltage will tell you watts with the right equation as well.
 

BATTLEAXE

Well-known member
#27
Don't have to hang it, just attach fish scale somewhere to fuselage, OR, HAVE IT nose PUSH A postage scale flat on the ground, (or if you're like me, a gram hops scale[up to 4lbs]
To have it thrust horizontal will add a drag coefficient given the surface you are testing on. If the plane was complete and on wheels would be the most ideal, but it looks like a separate bench style test.
 

Piotrsko

Well-known member
#28
Btw for best prop efficiency, you need square tip props that just clear the tibe ID. Ultimate would be bent tip, but i never see those outside of computer cooling fans
 

Piotrsko

Well-known member
#29
To have it thrust horizontal will add a drag coefficient given the surface you are testing on. If the plane was complete and on wheels would be the most ideal, but it looks like a separate bench style test.
Yeah wheels would be awesome, but I figure it's vibrating enough to kill the surface drag and we didn't want to go all that rocket surgery. Rough data is probably adequate enough.
 

Wildthing

Well-known member
#30
All good cheap ways to measure thrust, take your pick but you still need a amp/watt meter gauge and they aren't expensive. In this hobby everyone should have one just like a box cutter.
 

Wildthing

Well-known member
#31
Yeah wheels would be awesome, but I figure it's vibrating enough to kill the surface drag and we didn't want to go all that rocket surgery. Rough data is probably adequate enough.
Just like on a edf unit, the closer the fan blade is to the tube the better performance it has. It doesn't allow any of your airflow to blow back.
 

skymaster

Active member
#36
Ok so i got the power plant ready and set it on the plane not fully attached to it, just some tape to keep it in place just to test it. also i glued some landing gear set on to the frame, to see if the power plant would move the plane. well test went sort of ok. plane moves really quick. the only problem i have is that when i apply power to the esc they are not sync one has more power than the other. do i need to remove on of the red cables from one of the esc's, and how do i get them to sync. im also going to move the battery up a little bit.
 

Wildthing

Well-known member
#37
Ok so i got the power plant ready and set it on the plane not fully attached to it, just some tape to keep it in place just to test it. also i glued some landing gear set on to the frame, to see if the power plant would move the plane. well test went sort of ok. plane moves really quick. the only problem i have is that when i apply power to the esc they are not sync one has more power than the other. do i need to remove on of the red cables from one of the esc's, and how do i get them to sync. im also going to move the battery up a little bit.
Calibrate the throttle for each setup, one side at a time so unplug one and do it and then unplug it and plug in the other one and do it then see if they start up equally.
 

skymaster

Active member
#38
thanks for the info wildthing i had done that the whole weekend, but i found the problem. apparently when i bought these 2 esc's from ebay and i alsa bought some from flite test. well the one's from flite test are factory set and the one's i bought from ebay have a different firmware. so i got the 2 that i bought from ebay and connected them and they sync nicely problem solved.
 

Wildthing

Well-known member
#39
thanks for the info wildthing i had done that the whole weekend, but i found the problem. apparently when i bought these 2 esc's from ebay and i alsa bought some from flite test. well the one's from flite test are factory set and the one's i bought from ebay have a different firmware. so i got the 2 that i bought from ebay and connected them and they sync nicely problem solved.
Matching esc's are a must :)