Toronto Electric Model Aviation Club Forum

Toronto Electric Model Aviation Club (TEMAC) => Building / Construction => Topic started by: Gregor77 on April 07, 2018, 09:24:56 am

Title: 300 KV 60 size motor issues
Post by: Gregor77 on April 07, 2018, 09:24:56 am
So I have a bit of an issue....

300 KV motor pushing a 15x7 prop is not going to pull my 60 size spitfire off the ground (18 amps draw on a 6S around 300 watts +/-).  I can go 16 max diameter, but it leaves me not much room for error taking off.   So if I jump to a 16x10, 6S, I assume the draw will increase, it should give me more watts per lbs.  Correct?  I think someone said that it should be 100 watts per change of pitch and diameter? The esc is 100 amp capable.

I really dont want to pull the motor out again and find a sub as its perfectly lined up.
Title: Re: 300 KV 60 size motor issues
Post by: Frank v B on April 07, 2018, 05:44:32 pm
Greg,

There is something wrong if you are drawing only 18 amps.  EdEdge would call that a "nice idle".  My Nooner draws that!!!  Most 60's are between 400 and 500 KV.  Yours is 300 and that is really low.  It will need a fair amount of lumber to bring up the amps.
 
My (your old) .46 Mustang has a 14x 8.5 APC but it has not flown yet.

I have a 14 x 12 APC (new in package) which equates to a 15x10 versus your 15x7.  Also wooden Zinger 15x10 which you can try.  These props may get you up to about 700-800 watts, nowhere near what you need.  Suggest 3 bladed 15" diameter with as high a pitch as you can get.  Good place to look for these is at the upcoming 905 Squadron Swap meet April 22.

Frank
Title: Re: 300 KV 60 size motor issues
Post by: Ededge2002 on April 09, 2018, 12:25:46 pm
For comparison I run a Hacker A50-16S (365kv) on 6s with a 16x10 in that white Sukohi that you might remember. 

I would suggest 15x10 (largest pitch apc makes) if this is the biggest prop that will provide ground clearance.  If anyone makes a 15x12 that would be what I would try.

That is unless you go 8S!  8S would be the best solution (insert evil grin here)
Ed
Title: Re: 300 KV 60 size motor issues
Post by: Ededge2002 on April 09, 2018, 06:39:59 pm
I’ve been thinking. 
Going on the kv alone my setup runs:
6s x 3.8v x 365kv so 8322rpm unloaded. 
With just 300kv to get that same rpm it’s going to take 7.3s:
8322rpm / 300kv / 3.8v is 7.3s

I really think this is an 8S setup and would likely give great performance on a 15 x 10 in a warbird that your going to want some pitch speed available.
Title: Re: 300 KV 60 size motor issues
Post by: Andy Hoffer on April 09, 2018, 08:48:36 pm
I’ve been thinking. 
Going on the kv alone my setup runs:
6s x 3.8v x 365kv so 8322rpm unloaded. 
With just 300kv to get that same rpm it’s going to take 7.3s:
8322rpm / 300kv / 3.8v is 7.3s

I really think this is an 8S setup and would likely give great performance on a 15 x 10 in a warbird that your going to want some pitch speed available.

@Gregor77 ,

For a lot less fuss, we could go for a ride in a full-scale Cessna 172S at 2400 rpm with a 76-inch Hartzell prop! And the FPV experience is amazing, and includes peripheral vision!!!   8)

Andy
Title: Re: 300 KV 60 size motor issues
Post by: Ededge2002 on April 10, 2018, 12:01:31 am


For a lot less fuss, we could go for a ride in a full-scale Cessna 172S at 2400 rpm with a 76-inch Hartzell prop! And the FPV experience is amazing, and includes peripheral vision!!!   8)

Andy


And you dont have to wear those ridiculous looking goggles!!
Title: Re: 300 KV 60 size motor issues
Post by: Andy Hoffer on April 10, 2018, 12:54:23 am


For a lot less fuss, we could go for a ride in a full-scale Cessna 172S at 2400 rpm with a 76-inch Hartzell prop! And the FPV experience is amazing, and includes peripheral vision!!!   8)

Andy


And you dont have to wear those ridiculous looking goggles!!

@Ededge2002 ,

You are way too kind!!!   8)

Andy