• This site uses cookies. By continuing to use this site, you are agreeing to our use of cookies. Learn more.

Ugh I'm building another mini-arrow

Brett_N

Well-known member
#1
Not that I don't like the mini-arrow, but why did I start to build another wing?

Oh - cause I had a 40A ESC paired to the new emax 2306 2750KV motor laying on my workbench, a pair of crusty old MG90 servo's, and 2 sheet's of DTFB handy

:ROFLMAO::ROFLMAO::ROFLMAO::ROFLMAO:

Just over 1.1Kg - yes 1100g of thrust for the poor little rocket arrow.

Target AUW will be around 300g. I build really light using carpenters glue instead of HG.

I better find some carbon fiber.
 

Attachments

#3
I know you said you like to build light but since you can probably fly this at ludicrous speed, you could fill the empty wing space with polyurethane insulating spray foam which would add a tremendous amount of strength. I heard about that at Flite Fest a few weeks back for someone who was trying to reinforce his combat wing. I'm curious to try that on my next one...
 

Brett_N

Well-known member
#4
4S if I can get it to fit in the fuze. It's 40A @ 12V, so a 4S will give me just over 1300g of thrust if I'm doing the math right.

I may re-wire it for 6S if I can find a different ESC in the junk bin but the current goes to something crazy like 60A. I'll have to run 2x 3S 1000mah packs for a 6S though, none of my big 6S will fit.

I have tried poly foam filling before. On the mini-arrow, there's very little gap in the wing anyway and the spars take up a good chunk of that. I have some curved, flat CF that I'm going to try and use. I've never had a mini-arrow come apart at the wings, they always shear right down the middle so strenghtening the middle of the fuse is going to be the goal.

I did use poly foam on one of my SeaDuck builds in the fuze, but then the hot glue on the wings came undone, so it was a lost cause anyway. And now you know why I don't use HG anymore :LOL:
 

mrjdstewart

Well-known member
#5
emax reports the little 2306-2750kv with a 5x5 and a 4S battery will crank out 1750g of thrust @ almost 60amps and 880w.

i just put one on my high speed goblin after toasting the previous motor.

i am going to trust their numbers and hope that the motor can handle the 880 watts of power without getting fried. pretty sure that is what happened to my last motor.

good luck,

me :cool:
 

Attachments

Brett_N

Well-known member
#6
LOL - I didn't realize there was a page 2 on that PDF :ROFLMAO::ROFLMAO:

I don't have a spare 60A controller so 3S is all it's gonna be. My ESC is 4S capable, but I don't think it will last too long
 

Brett_N

Well-known member
#7
MRJ - just a heads up, mine just smoked with no load testing on a 4S and hard limited to 30A after burping the throttle. Wasn't on it for more than 3 seconds. No Bueno...:unsure: and motor is REALLY hot. (even smells)

ESC is cool to the touch, pulled everything apart and it's definitely the motor.

Think EMAX is blowing smoke.

Still works on 3S....but damnit I just cut the fuze for a 4S battery.
 

mrjdstewart

Well-known member
#8
interesting. :unsure:

i also got my motor installed on the Gremlin yesterday and did a spin test. i did not put it on my amp/watt meter but did spin it up pretty good.

i am using a 2306-2750kv w/ 5x5 prop, 60A esc, and a 4S-2200 and it did just fine. no motor heat, no esc issues, so hopefully it will fly. i guess we will find out saturday?

not sure why you got so much heat? maybe a bad motor from the start? what do the copper coils look like? are the brown and burnt looking?

i will report back once i either fly or die. :LOL:

laters,

me :cool:
 

mrjdstewart

Well-known member
#12
my old Goblin was using a BrotherHobby 2507-2450kv with same ESC and battery but was swinging a 6x45 BN prop. I think it was the prop that killed it, just a touch too much...

but, it was very fast for many flights before it died.


if you can get an Arrow to fly this fast you will have a very fun little wing!

laters,

me :cool:
 

mrjdstewart

Well-known member
#13
ok, so maybe you were right....

launched the goblin today and it took about 5 secs before the motor went pop, and i was gliding my way back to the field. on inspection the motor was smoked, wires melted, and smelled like an electrical fire.

so, i guess Emax is full of .... with their numbers. was expecting a little more from a company like them. save yourself the pain and do not use this on the goblin.

laters,

me :cool:
 

Brett_N

Well-known member
#15
Yikes

I tested mine on a 3S and it still runs. But we just got hit with noise restrictions so no more rear mounted motors. Guess mine will go int he parts pile for a while. Maybe a mini-mustang or somthing.
 

mrjdstewart

Well-known member
#16
... we just got hit with noise restrictions so no more rear mounted motors.
what? who did that? maybe time to find a new field. i have a huge amount of pushers and prop in slots, i would be pissed if i was told i could not fly them anymore.

sorry to hear that,

me :cool:
 

Brett_N

Well-known member
#19
what? who did that? maybe time to find a new field. i have a huge amount of pushers and prop in slots, i would be pissed if i was told i could not fly them anymore.

sorry to hear that,

me :cool:
no kidding. But, the neighbors don't like us flying weed-whackers at 6am for some reason. OUr park is directly in the middle of a neighborhood and maintained by the city (so, it's free, and no AMA restrictions...) gotta play nice and keep the field.