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        Discussion 3s motor on 4s?

#1 diekmann Apr 11, 2011 01:42 PM

3s motor on 4s?
 
so here i have a graysonhobby 2217-06. http://www.graysonhobby.com/catalog/...ies-p-337.html it spins a 8x4 prop at 225w according to the specs. i like it on 3s but i think i'm going to upgrade. a bit more speed and trust is in mind, but without getting a new motor. so the product page says it can handle 4s but what prop will i have to use for best performance and how big of an esc will i need? thanks for the help peeps :)
-Diekmann-

#2 Dr Kiwi Apr 11, 2011 02:08 PM

a bit more speed and thrust is in mind, but without getting a new motor.

The Holy Grail.... something for nothing!

The 2217/6 is an excellent motor, but getting more speed AND more thrust means pushing a LOT more power into it.

To keep the amp/watts within sensible limits on 4s, you will need to drop down to a 6" prop (a 7x5 APC E draws almost exactly the same as an 8x4 GWS HD... so on 4s either will be too much for it).

It might cope with 250W-275W (20A on 4s?)... but I wouldn't like to see it pushed much more.

#3 diekmann Apr 11, 2011 02:12 PM

so the 6x4 apc i have for my microjet would do it on a 4s? only 20 amps too? hmmmm how about same speed but more thrust?

#4 Dr Kiwi Apr 11, 2011 04:24 PM

Quote:

Originally Posted by diekmann (Post 17941448)
so the 6x4 apc i have for my microjet would do it on a 4s? only 20 amps too? hmmmm how about same speed but more thrust?

For that you'd need larger diameter but less pitch (?7x3).

But I can't be sure that would get you any more thrust than an 8x4 on 3s.

#5 Lardog Apr 11, 2011 06:41 PM

I'd recommend keeping it on 3s and just changing the prop. Not sure what you are running that motor on, but I use it on Alfas with an 8x6 at around 450W and they flat out haul. It also will take a World Models Mini Midget Mustang beyond 100 mph.

#6 Dr Kiwi Apr 11, 2011 08:36 PM

What sort of 8x6 is that? I ran my A2217K-6T test motor with an amp hungry 8x8 APC E and at 11.2v still only drew 36.7A/397W.....I cannot see how, with just an 8x6, you are getting over 40A/450W?????

#7 Lardog Apr 11, 2011 09:36 PM

1 Attachment(s)
Just a normal APC E. I have the BP hobbies 2217-6 1500Kv, which is the same Suppo motor Grayson is selling. My #s are mostly consistent with what others at my field are getting as well.

http://www.rcgroups.com/forums/showp...71&postcount=3

My recorded numbers are attatched...

#8 diekmann Apr 12, 2011 10:53 PM

so would i get similar numbers with the thin electric 8x6? i can get a normal 9x6 and trim it down to 8x6 normal i spose but it'd be easier to just get the 8x6 thin. just gotta be sure i'd get the same performance
thanks
-Diekmann-

#9 Lardog Apr 12, 2011 11:16 PM

Definitely be easier to just buy an 8x6. Way too much hassle to cut and balance another prop. I'm guessing your LHS has them in stock.

And yes, I expect you would get similar results. Of course, your choice in battery will have an affect. As you can see, mine aren't the best.

#10 diekmann Apr 12, 2011 11:26 PM

i don't have a LHS, i live in the middle of absolute nowhere, my LHS is a almost 2 hr drive :( only complaint about where i live, plenty of space to fly tho :) i mostly order online,

lardog does your motor get hot with the 8x6? cause i wonder if i could thrown in a 8x7 in there and see if i be conservative maybe pull off even speedier? when i run it with the 8x4 it's almost colder than when it started :p so no probs with that prop

#11 Lardog Apr 13, 2011 03:39 AM

I'm sure mine doesn't get hot, but it's also hanging out in the wind. I don't think I'd want to go beyond the 8x6 though. You are already pushing a 250W motor beyond 400W.

#12 Dr Kiwi Apr 13, 2011 11:15 AM

3 Attachment(s)
That BP version must be a bit higher Kv than the one I tested:

#13 Dr Kiwi Apr 13, 2011 11:21 AM

Quote:

Originally Posted by diekmann (Post 17955352)
so would i get similar numbers with the thin electric 8x6? i can get a normal 9x6 and trim it down to 8x6 normal i spose but it'd be easier to just get the 8x6 thin. just gotta be sure i'd get the same performance
thanks
-Diekmann-

The only 8x6 APC E prop is a thin electric.

There are 8x6 APC SF, 8x6 APC Sport... and maybe 8x6 APC Pylon... but there's only the one E -type.

#14 diekmann Apr 13, 2011 11:47 PM

ahh i see, and i understand the part about not pushing it that much, do you seriously get 100mph on your midget mustang though? i have a scratchbuilt wing that i'm putting it on so the motor is right out in the wind and it's a low drag airframe, i wonder if i could get some decent speed :) oh and what is the C discharge rating on your batteries?
thanks
-Diekmann-

#15 Lardog Apr 13, 2011 11:49 PM

Quote:

Originally Posted by diekmann (Post 17964785)
do you seriously get 100mph on your midget mustang though?

Oh yeah! :D

Check em out...

http://www.planeadrenalinrc.com/Speed_Shop.php


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