Pusher Prop for electric power questions!

[Tommyp]

Hello!, and please go easy on me .. but .. I wasn't able to find anything that would answer my question/questions on this subject. So ...

... I see that Pusher Propellers are/get recommended for electric powered C/L models as it can increase line tension... but, how does one mount that propeller? Do you have to have the motor running the opposite way? Do you mount the prop backwards? I know there will be some chuckling and eye rolling here! .. 😂 .. but I honestly don't have a clue HOW this works. Any input would be most welcome!, and THANK YOU in advance!

Tommyp/Tommy Piorek

[Dwayne Donnelly]

Welcome aboard. 

Yup just mount as normal and run motor clockwise.

[Dan McEntee]

Hello!, and please go easy on me .. but .. I wasn't able to find anything that would answer my question/questions on this subject. So ...

... I see that Pusher Propellers are/get recommended for electric powered C/L models as it can increase line tension... but, how does one mount that propeller? Do you have to have the motor running the opposite way? Do you mount the prop backwards? I know there will be some chuckling and eye rolling here! .. 😂 .. but I honestly don't have a clue HOW this works. Any input would be most welcome!, and THANK YOU in advance!

Tommyp/Tommy Piorek

   Hi Tom and Welcome!;
     Well first off, start to refer to them as left hand props. The "pusher" moniker just really doesn't fit and is confusing. P-38 Lightnings had props that turned both ways and they didn't use "pusher props!! One was right hand rotation and the other was left hand. Think of yourself looking at the prop as you sit in the airplane. If the prop tips rotate towards your right, ( like normal) it's a right handed prop or what was called a tractor prop. If it rotates to your left, it is a left handed prop. There is still a front and back to the prop and the correct side must face forward. It will mount to the shaft in the same way and you reverse the rotation of the motor to accommodate it. That is usually done by swapping any two motor wires. If you are completely new to control line, I would save that bit of technology until later, and learn to fly and trim models for flight first. If you  are an experienced C/L pilot and just getting started in electric, I would still wait until later to try the left hand stuff until you are more familiar with the technology, and everything else and trimming the airplane will be a bit more like what you already know. I hope this helps a bit.
    Type at you later,
     Dan McEntee

[Frank Imbriaco]

Research the "Gettin' All AMP 'ed Up " section.

 It's all there- plus almost any other question you seek answers for related to electric flight.

[Tommyp]

In order:

Dwayne! THANK YOU for the reply!, and I did mount the "PP" normally ... absolutely nothing happened. There wasn't even a modicum of thrust, hence my confusion. I didn't change the direction of the motor either, so there's that! But, perhaps as the 2nd reply suggests, I may also have the wrong type of prop! THANKS again!

Dan!  THANK YOU for the reply! Hmmmm... left hand props! That could indeed be the issue here, and I think it is! I have what is actually called a "Pusher Propeller" .. in this case a APC 10X5 EP Thin Electric Pusher .. and nowhere does it say left hand propeller. So! ... perhaps mystery solved? REVERSING the direction makes sense too, and I will have to try that. Also, LONG TIME C/L flyer here, and switched my RC flying to electric 12 years ago, so know and understand the tech very well. What I have done is electric conversions on three of my C/L models, and with excellent success, but was intrigued with the "line tension increase" possibility with a left hand propeller. THANKS again!

Frank!  THANK YOU for rhe reply!, and indeed. I actually did look in that category, but apparently not hard enough!  🙄  THANKS for the lead, and I will go have another look. BEST!!!

Tommyp

[Howard Rush]

I have what is actually called a "Pusher Propeller" .. in this case a APC 10X5 EP Thin Electric Pusher .. and nowhere does it say left hand propeller.

Same thing, although neither definition is what I’d choose.

... but was intrigued with the "line tension increase" possibility with a left hand propeller.

Don’t count on it. It will be different, but not necessarily better. 

[Tommyp]

Same thing, although neither definition is what I’d choose.

Don’t count on it. It will be different, but not necessarily better.

THANK YOU for the reply Howard! Definitely up to speed now on the definition and what's what. To quote from the movie "Animal House" ... "Knowledge is good!" 😁 And ya ... I had a feeling that it might not be all that better, but was intrigued none the less. I guess I'll have to satisfy that itch and try it! I have to also mention that back around 1975 I built/flew a NEMESIS with a Super Tigre .35 on it, and what a combination that was! Not in competition mind you, but locally with my buds. I am a fan! Don't know that I could handle that HOT an airplane with that engine today! Back then though? Ah ... youth! THANKS again for the reply! 😎

Tommyp

[Brett Buck]

Same thing, although neither definition is what I’d choose.

Don’t count on it. It will be different, but not necessarily better.

  Increased some places, reduced in others. It does some pretty unusual stuff at times - I was out flying with your JCT buddy and his reverse-rotation prop, and everything looked pretty normal until the hourglass. Top of the hourglass, it did something so unusual in yaw that I almost lost sight of the airplane for a second. It wasn't malformed shape, it just looked like it was going to do a right turn into the Napa River.

    Brett

[Dennis Toth]

Tom,
The APC 10x5EP is indeed a "pusher" (left hand props same same, also know as clockwise props) on conventional motor in front setups mount the prop as normal and set the motor for clockwise rotation (easy to just switch any two leads on the motor/ESP connectors. The benefit of the pusher is on outside maneuvers, here the clockwise rotation yaws the nose out as the model turns through the maneuver giving a little extra feel of security. However, on inside maneuvers it is the opposite but most fliers handle that without noticing it. On conventional tractor props the opposite reactions happen. That is why some use the reverse bellcrank to have the back line as down to give a touch of outboard yaw on outside turns.

Two issues with the Lefties, one if the plane is trimmed for tractor (counter clockwise) motor rotation you will find that switching to pusher cause the ship to have a little down trim. I converted my Still Stuka and on the first take-off found it just got up on the mains and waited for me to give it up to get airborne, flies great but was a surprise.

Second, there is no cheap pitch gauge for them (I think Jim Lee has one) so heat re-pitching is more difficult as you need to make a gauge stick with a prop bolt at one end and a triangle screwed on the end that can be set to the back side of the prop. The stick is set at around the 70% length of the blade. You then guess at the amount of pitch change you want to move to and tighten down the triangle at the new pitch and heat pitch as normal. Windy showed this in several of his prop videos. This works but takes a while till you get a feel for how much to move the pitch (very small movement is a lot of pitch, go slow). For electric you can simple adjust the rpm if you are within the control limits of the ESP governor rpm.

You didn't mention what ship or rpm you were set up for but I would guess somewhere around 10K would be a stating point. Remember electric's don't unload to a higher rpm in the air like IC, they govern down to hold the same rpm as load is reduced.

Best,     DennisT

[John Rist]

LH props help the most on takeoff.  Steers the plane out instead in. 

[Dennis Toth]

One thing to remember is if you use the back line as down for a conventional IC or tractor prop it will be the opposite on the pusher. The pusher setup allows using the simple bellcrank mount (control arm to the outboard side). This makes clearing the leadouts easy without the need for standoff or crazy bends in the pushrod.

Best,    DennisT

[Frank Imbriaco]

 Actually when using a pusher prop, line tension will be increased when you most need it .
 
I've experienced aircraft heading" back out" when hit by a significant gust. Some pilots will undoubtedly benefit.

Yes, there  trade offs. I fly both tractor and pusher e-powered aircraft.

[Avaiojet]

Someone correct me if I'm wrong. 

Having owned a Lake aircraft, the seaplane was a "pusher" configuration because the propeller was behind "pushing" the aircraft through the air.

A "tractor" configuration, the propeller is in front of the aircraft pulling the aircraft. It really makes no difference which way the prop turns. If it's "in the front" it's a "tractor" type prop.

So, referring to a "pusher" type prop used in the front of an aircraft or model sounds incorrect, even in layman's terms.

Why is this never corrected?

1)  Tractor type prop turning clockwise.
2)  Tractor type prop turning counter-clockwise.

[Tommyp]

One thing to remember is if you use the back line as down for a conventional IC or tractor prop it will be the opposite on the pusher. The pusher setup allows using the simple bellcrank mount (control arm to the outboard side). This makes clearing the leadouts easy without the need for standoff or crazy bends in the pushrod.

Best,    DennisT

Dennis!
THANK YOU for the very concise reply!, .. and .. THANKS to ALL of you for your replies! A wealth of info it is! I will say that the plane I wanted to try this on is my old "Ukie35". I converted it to electric back in November as I thought it would be a nice platform to try out electric power/flight. It's a SOLID flyer with no bad tendencies .. and .. it actually does have better than good line tension as is in the normal tractor configuration. With that said I'm flying a 5.2 lap time. Here's the electric set up I have in it:

650KV motor
4S 2200/lipo
11X7 wood Zinger prop ... I have a crap load of these from the "old days"... and I DO balance 'em!
40amp ESC

I did not know about the back line being your down elevator with a PP/LH prop .. and .. as luck would have it, that is the way the plane is set up by default as the control horn is on top of the elevator on this model. So, I guess I'm good to go there, yes? A reverse bell crank? Never even knew that existed! Very interesting! I'll attach a pic of the "Ukie35" .. do I hear some chuckles? .. 😂😂😂 .. as it is in it's converted state. I've had this model for years actually, so I thought it would be a good candidate with low risk. 😎

Tommyp

[Tommyp]

To add to the confusion left and right is as viewed from the pilots seat but in models you have left hand props because they go left to right at the 12 oclock position as viewed from the front looking back.

One thing I don't get, how can you be a CL flier for years and not know how to put a prop on or which way it should turn?


Motorman

Motorman!
Well, I do know how to mount props of course!, but if you read my very 1st post, I mounted the PP/LH prop in the normal way, but did NOT KNOW that the motor needed to be run in reverse. THAT .. as it turns out .. was the issue! The whole trouble started with the left hand/pusher prop experiment, and ya ... common sense would dictate that the motor would NEED to run in reverse with this type prop .. but .. for whatever reason, I just wasn't sure. So ... I thought I would ask here, and the replies/help have been great! But there's always that one! .. 😀 .. but I guess I deserved it. THANKS for your comment!

Tommyp

[Dennis Toth]

Tom,
Ship looks cool!! Since you are using Zinger tractor props the setup you will work fine. If you change to pusher prop just move the tail horn to the bottom and it would be good. Interestingly, one of the top Old Time Stunt ships the "Barnstormer" was set up with the tail horn on the top of the elevator, I suspect that Lou Andrews knew of the advantage with the back line down gave, although it wasn't really talked about much back then. Lots of secrets back then.

Your lap time of 5.2 is a bit slow for 60' lines most would fly around 4.85 ish. If on 65' or so its in the range.

Best,  DennisT

[Bill Calkins]

To sum it all up:
1. Take the normal (Tractor) prop. and  remove it.
2. Put the abnormal (Pusher) prop. on.
3. The only difference should be in side view.
4. Go fly it.

[Dennis Toth]

Bill,
Need to add:

Reverse motor rotation.
Adjust rpm based on prop pitch (he was flying originally with an 11x7)

Best,    DennisT

[Dwayne Donnelly]

BTW what size motor is it?  I could be wrong but 650 KV sounds kinda low for a 10X5

[Howard Rush]

To sum it all up:
1. Take the normal (Tractor) prop. and  remove it.
2. Put the abnormal (Pusher) prop. on.
3. The only difference should be in side view.
4. Go fly it.

You might want to move the CG if you’re going to operate it as a canard.

[Tommyp]

You know, when one posts on ANY open forum .. subject doesn't really matter, could be C/L, R/C, vintage cars, etc. .. it can be akin to walking into a lions den wearing a coat of roast beef! 😂😂😂 The information shared and gleaned is worth that risk though!, and such was the case here. ALL that spent some time to help here were greatly appreciated! The best part is, I DID find what I was looking for, and that was ... MOTOR REVERSING .. that was the key I was missing. Everything else was fine. That said though, I want to reply to a few posts here now. So in order:

Dennis T!
Truth be told, I am flying this Canard ..🤣🤣🤣.. on 52' lines with a lap time of 5.2 seconds. I have plenty of power left as I'm only at 1/2 power on 4S .. so .. I can easily shave off a few seconds. But, do you think I should be on 60'? No issues with 52', but thought I would inquire!

Dwayne D!
The motor, actually the entire "power package" came out of a retired RC PA18 Super Cub that was my winter flyer for years. I put 600 some odd flights on that model, but retired it and saved the power package as I had something like this in mind. So ... the motor is a DETRUM BM 3720A3 - 650KV and the usable prop range on 4S/2200 is 9X8 to 12X7. I was flying that model with a 13X6 as I fly in a very scale manner .. contingent on the model of course .. and there was never even a warm ESC, motor, or battery in all those flights. Flight time was 6 minutes BTW. The plane weighed approx. 5.5lbs. So ... in the "Ukie35", this package isn't even breaking a sweat! I went to an 11X7 prop after that pic was taken, and it made a MAJOR difference in performance while still just hardly breaking a sweat. I land after a 5 minute flight with almost 40% left in the pack. Again, that's turning a 5.2 lap time on 52' lines.

Howard Rush!
A Canard???!!!  🤣🤣🤣🤣🤣  Now THAT was freaking funny! CG change duly noted IF I end up operating it as a Canard! 😎🤪😎

I also did a conversion on my old Akromaster which I was flying on an OS Max .15 III for like, ever! This one fly's GREAT with excellent lap speed and very good line tension .. so .. no need to experiment with the LH/PP thang here. I'll attach a pic of the conversion. THANKS again for ALL the comments and help!

Tommyp

[Dwayne Donnelly]

Thanks Tommy, you may want to get a APC 11X5.5 EP as well I think that 10X5 may be a bit small.

[Tommyp]

Thanks Tommy, you may want to get a APC 11X5.5 EP as well I think that 10X5 may be a bit small.

Dwayne!
I jettisoned the 10X5 and went to a Zinger 11X7, which was a major improvement! I will try an APC 11X5.5 as I believe I have one! Truly appreciate the input. THANKS!!! 😎

Tommyp

[John Rist]

APC has an F2B series of props.  Earlier discussions (if I remember correctly) talk about lower amp usage for the F2B series.  I have had some good results with a cut down 12x6EP.  I do use a setup that controls RPMs.  I am running around 9K.

https://www.apcprop.com/product/12x6epf2b/

[Howard Rush]

As Howard said, don't let all the new tension fool you, keep the speed up, like 5.2 second laps give or take.

I didn't intend to say that, but I looked at what I said and saw that the antecedent for a pronoun was unclear, a crime of which I continually accuse my wife.  Rather than "It will be different...", I shoulda said "The airplane will operate differently with a forwards prop than with a backwards prop..." or some such.  Thereby hangs a tale.  I built my first electric stunter for a backwards APC prop and made the back line up, as lore would have one do.  It worked OK.  When I built my second electric stunter, I installed the bellcrank the same way, but forgot that the Igor flap mechanism reverses the sign, thus the front line was up.  The airplane did the same maneuver at the top of the hourglass that Brett describes above.  I switched to a normal prop, and all was well. The leadouts may not have been the difference, but they make a good story.

The only way I found to make nonscary takeoffs with either prop species is to take off with reduced power. 

[Tommyp]

One thing I learned the hard way. all that line tension can be misleading.  The model must be flying at it's proper speed for maneuvers. I had mine at 6 second laps, tons of tension, tried a few maneuvers.  Nope, too slow and almost lost it.  As Howard said, don't let all the new tension fool you, keep the speed up, like 5.2 second laps give or take.

PS, the plane was a light pig, long gone. LL~Pigs don't fly.

Ty!
Sorry I missed this post somehow ... probably because I was on my mobile device where everything is pretty tiny and easy to miss. Anyway, THANK YOU!!! Your description of what happened to your plane with good line tension, but TOO SLOW lap time was EXACTLY what I was experiencing. I'm going to UP the speed/lap time next time out. I'm getting a lot closer to where I want/need to be here. THANKS!!! 😎

Tommyp

[Tommyp]

APC has an F2B series of props.  Earlier discussions (if I remember correctly) talk about lower amp usage for the F2B series.  I have had some good results with a cut down 12x6EP.  I do use a setup that controls RPMs.  I am running around 9K.

https://www.apcprop.com/product/12x6epf2b/

THANKS John! ... going to check it out. 😎

Tommyp

[Ken Culbertson]

My 2 cents worth comes from switching from IC to Electric.  I went to the left hand rotation at first and was pleased with the ease of takeoff's and being to have the leadouts more forward.  I didn't pay as much attention to the squirrely hourglass as I blamed the pilot.  I adapted and went on.  It wasn't till a year later that I broke my last left hand prop on a flying session and had to reverse the motor and "fly right" that I found that there was very little difference, in fact the return of the smooth hourglass far outweighed the easier takeoff.  I have stayed right hand and don't plan to switch again.

Ken