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

Inrunner vs outrunner

#1
Hi. Just getting back into flying. I have some old planes I want to part for FT experiments. I have 2 inrunner motors that used gearboxes. One is brushed one is bl. If I wanted to eliminate the gearboxes how would I determine what size prop to use with them?

Thanks!
 

mrjdstewart

Well-known member
#2
using in-runners on any FT design will be challenging. all are designed for brushless out-runners. not saying it cant be done but it will take some effort. for the price of the newer out-runners, i would just bite the bullet and buy one. save yourself the heartache. plus then the prop selection is easy.

without knowing th emotors, what watts they can pull, amp rating, it will be very difficult to guess on a prop. might try going to ecalc and see if they might have some brushless motor options.

good luck,

me :cool:
 

Merv

Well-known member
#3
If you know the KV & amp rating, I’d look for a motor with similar ratings & try the prop it uses. If you don’t know the ratings of your motor, you will need to sneak up on it. Start small prop, run it for 5 seconds see if it’s hot. If not run it for a minute & check temperature. If it not hot, do it again with a larger prop. Warm is ok, but if you can’t hold the motor in your hand for 30 seconds, it’s too hot. You need a smaller prop.
 
Last edited:

Headbang

Well-known member
#4
As well, depending how old they are, they may be way to heavy and under powered. The new brushless outrunners are very light and very powerful compared to motors in days gone by. Last year I converted my old Midwest Aero-electric from a 550 inrunner can motor with nicads to an outrunner Power 25 with lipo. Went from a 7lb plane to a 3lb plane with over triple the static thrust. Same size prop.
 

Headbang

Well-known member
#6
I just really want to tinker with them. I appreciate the input y’all.

One is from the foam UCanDo3d. http://www.greathobbies.com/productinfo/?prod_id=GPMG0216

The other was called a brushless 20 for the 3dBuddy. http://www.rcuniverse.com/magazine/article_display.cfm?article_id=461
Both motors are very small, might work in the mini's.

The brushed motor "might" work with a 5x4.5 or 6x3 prop without the gear drive. (280-size w/5:1 gearbox (included) ) http://www.greathobbies.com/productinfo/?prod_id=GPMA1190 (Fortunately that site is my goto for everything local, I know how to find stuff there)

As for the brushless. More info here https://www.rcgroups.com/forums/showthread.php?368907-Ultra-RC-3D-Buddy-Edge-Review
It might be a similar 6x3 prop without the gear box.
 

Bricks

Well-known member
#7
The ESC`s will be different between the 2 motors as one is brushed and only 2 wires running DC current with what ever voltage it calls for. The brushless runs AC current and has 3 wires or at least should.

Removing the gear box from the DC brushed motor I do not believe you will have enough power using the motor only
 
#8
Both motors are very small, might work in the mini's.

The brushed motor "might" work with a 5x4.5 or 6x3 prop without the gear drive. (280-size w/5:1 gearbox (included) ) http://www.greathobbies.com/productinfo/?prod_id=GPMA1190 (Fortunately that site is my goto for everything local, I know how to find stuff there)

As for the brushless. More info here https://www.rcgroups.com/forums/showthread.php?368907-Ultra-RC-3D-Buddy-Edge-Review
It might be a similar 6x3 prop without the gear box.
Great. Thank you! I think I can use these props at least as a starting point and use the process above Merv suggested
 
#9
The ESC`s will be different between the 2 motors as one is brushed and only 2 wires running DC current with what ever voltage it calls for. The brushless runs AC current and has 3 wires or at least should.

Removing the gear box from the DC brushed motor I do not believe you will have enough power using the motor only
Exactly- that was another thing I was thinking about. I do still have the esc’s and everything works. Worst case my daughter and I can try building planes to match the motors instead of vice versa. Couple of fedex boxes and glue and we have our own FliteTest channel :)))