Torque Roll

[J D 8]

7 minutes ago, Martin Harris - Moderator said:

One factor that comes to mind (although the effect may be debatable) is that there is a significant rotating mass at a larger diameter than in IC rotating components, in a typical outrunner.  Maybe where the idea of EP producing more torque effects came from?

  Like the gyroscopic effect of the rotary engine of a Sopwith Camel then.

[Martin Harris - Moderator]

Great minds John?  See the edit I was doing while you were composing your reply!

[PatMc]

20 minutes ago, Martin Harris - Moderator said:

One factor that comes to mind (although the effect may be debatable) is that in a typical outrunner there is a significant rotating mass at a larger diameter than an IC engine’s rotating components. Maybe where the idea of EP producing more torque effects came from?

 

At model sizes I would agree that helix effects probably outweigh torque effects but ask a Sopwith Camel or high powered WW2 piston engined aircraft’s pilot whether they are significant!

I would have thought that the difference in mass between an IC & EP prop acting at a far greater mean diameter would pretty much negate any difference in gyroscopic effect. 

 

 

 

 

 

 

[leccyflyer]

As it happens I found an ancient video the other day of my Cambrian Bf109E in it's early noughties early electric flight configuration - pre - Lipo days - so she's carrying  a hefty chunk of 10 SCR1250s up front, an Axi 2820/10 and a 10x7@ APC-E. Kev Mullarkey with one of his signature high power launches.

 

Not a trace of any wild roll or yaw to port, in fact a bit of a roll to starboard. These days, with lighter weight and more power from lipos the funfighters have relatively drama free handlaunches and certainly don't need Kev's javelin technique. Just as well, we're all a bit old for that kind of thing now. Bear in mind  that this was in the day when electric flight was far from mainstream and no small number of folks said it wasn't possible to successfully fly a funfighter with electric power. Video clip shot by Tim Hooper on a memorable visit to Warrington Model Club in 2003.

cambrian bf109 launch.avi

 

 

Edited June 28, 2023 by leccyflyer

[Martin Harris - Moderator]

 

40 minutes ago, PatMc said:

I would have thought that the difference in mass between an IC & EP prop acting at a far greater mean diameter would pretty much negate any difference in gyroscopic effect. 

 

 

 

 

 

 

I’m not making any particular argument for or against the hypothesis - just a little brainstorming- but Isn’t most of the extra mass concentrated at the hub area?  

[Nigel Heather]

5 hours ago, leccyflyer said:

Aaah, you didn't say it was the manufacturer's recommendation. Might be worth asking them for clarification.

 

As Pat has pointed out the term torque roll is something of a misnomer, one of long discussion in online fora for years, what is being described is due to the rotational slipstream from a large prop acting on the fin which is a yaw to the left in conventional airframes. It's conceivable, even likely, that an electric powered funfighter will have at least a 10x7" prop, or even an 11x7" prop, if fitted with a "typical" outrunner. In it's IOC guise it will probably have had something like a 9x6" prop if fitted with a .25 cu in glow engine.  Coupled with the smaller fin on the Bf109, compared to the Spitfire, that might provide some explanation. However, like I said, I didn't notice any difference of adverse effects when moving up from IC to a brushless motor onb my Cambrian Bf109e.

 

 

 

Thanks for the information.  Out of interest when you electrified your Cambrian Bf109 did you go 3S or 4S?

[leccyflyer]

My Cambrian Bf109e conversion went from Enya .25SS to Axi 2820/10, 10xCP1700 sub-C NiCds and a 10x7" APC-E prop. I don't think I ever flew the model with lipos, but with similar models I've used 3s1p 3300mah -4200mah 20C -30C lipos. 

[Nigel Heather]

1 hour ago, leccyflyer said:

As it happens I found an ancient video the other day of my Cambrian Bf109E in it's early noughties early electric flight configuration - pre - Lipo days - so she's carrying  a hefty chunk of 10 SCR1250s up front, an Axi 2820/10 and a 10x7@ APC-E. Kev Mullarkey with one of his signature high power launches.

 

Not a trace of any wild roll or yaw to port, in fact a bit of a roll to starboard. These days, with lighter weight and more power from lipos the funfighters have relatively drama free handlaunches and certainly don't need Kev's javelin technique. Just as well, we're all a bit old for that kind of thing now. Bear in mind  that this was in the day when electric flight was far from mainstream and no small number of folks said it wasn't possible to successfully fly a funfighter with electric power. Video clip shot by Tim Hooper on a memorable visit to Warrington Model Club in 2003.

cambrian bf109 launch.avi 28.44 MB · 0 downloads

 

 

 

Hi, I couldn't view that video - get a message saying that it couldn't be located.

 

Incidentally, Warrington was the very first club I tried - would have been in the late 80s.  I didn't last long there though, I joined because I had a friend who lived in Birchwood and we both worked nearby.  But I lived in Cheadle and then Macclesfield and moved jobs so it became too much of a trek to make only to find there was no one that could buddy with me (I was still trying to learn to fly a Yamamoto at the time).

[Nigel Heather]

1 minute ago, leccyflyer said:

My Cambrian Bf109e conversion went from Enya .25SS to Axi 2820/10, 10xCP1700 sub-C NiCds and a 10x7" APC-E prop. I don't think I ever flew the model with lipos, but with similar models I've used 3s1p 3300mah -4200mah 20C -30C lipos. 

Quite high capacity - was that needed for flight time or get useful weight up front.

[leccyflyer]

Not really high capacity, my other electric models at that time were using SCRC 2400mah sub-C cells, it was more a case of the pack size that could fit where the fuel tank had been and provide enough urge - 1o cells - for the Axi 2820/10. That was my first AXI motor IIRC.

 

Aaah - just realised you meant the lipo size. Yes, there's no point in carrying dead weight if you can carry useful weight a 3s1p 3300mah pack will balance a Ripmax Spitfire perfectly and sits beautifully in the battery tray. Likewise a 3s1p 4200mah pack fits nicely in a Balsacraft FW190 or Bearcat and, with their very short nose, is a good sunstitute for an 8 cell 2400mah Sub-C nicd pack.

 

I've uploaded the short video clip to You Tube, so you should be able to see it at this link.

 

 

Edited June 28, 2023 by leccyflyer

[Martin Harris - Moderator]

I’m yet to be convinced that a stumbling run holding a model at arm’s length above the head followed by an unbalanced lunge is better than a carefully controlled hard push from a balanced stance.  
 

The typical javelin thrower holds his projectile well behind him before launch and uses back muscles, shoulder rotation, pectoral and arm muscles to release his javelin while maintaining speed and balance - not qualities often observed at the model flying field!

[PatMc]

22 minutes ago, Martin Harris - Moderator said:

I’m yet to be convinced that a stumbling run holding a model at arm’s length above the head followed by an unbalanced lunge is better than a carefully controlled hard push from a balanced stance.  
 

The typical javelin thrower holds his projectile well behind him before launch and uses back muscles, shoulder rotation, pectoral and arm muscles to release his javelin while maintaining speed and balance - not qualities often observed at the model flying field!

Most people who hand launch for someone else run hard up to the point of launch then stop before chucking. 😉

[leccyflyer]

Messages all received and understood. Personally I consider hand launching to be the least favoured option for putting an aeroplane into the sky, however -

 

1. I never had a model fail to get away from one of Kev's energetic launches. In fact, twice, I've had a model that was switched off during the chuck, which completed a circuit of the field, left entirely to it's one devices, deadstick, and landed back at the launch point. 😎

2. I'm extremely lucky and grateful - because I can't hand launch my own models for toffee - to be able to draw on the assistance of two superb hand launchers, who have very different techniques, but are both essentially static stable throws.

3. I've seen more models destroyed through bad hand launches than any other cause. That includes the club chairman throwing a wee Piper Cub vertically into the ground three feet in front of us.

[MattyB]

38 minutes ago, PatMc said:

Most people who hand launch for someone else run hard up to the point of launch then stop before chucking. 😉

 

So so true. We've all seen it!

[MattyB]

4 hours ago, leccyflyer said:

That's a superb video Matty - love it. 😎 Interesting how the glider completely disappeared when it entered that rear 3/4 end view going away, then reappeared as it turned.

 

Yeah, that is a 3m+ model too, though the effect is exagerated somewhat by the (state of the art then, rubbish now) digital compact camera it was taken on. This is exactly why I never like white all over models!

[Martin Harris - Moderator]

22 minutes ago, MattyB said:

 

So so true. We've all seen it!

The video posted shows a rare example of someone carrying forward motion into the launch so I decided not to add this observation although I agree enthusiastically.  I’m sure that unless you’re a skilled athlete you can impart far more energy/speed into the throw from a balanced standing position - not to speak of accuracy in giving a wings level launch.  

[john davidson 1]

A quite heavy model I have often hand launched for a clubmate is so powerful it pulls out of your hand , you have little say in the matter.

[J D 8]

 I have an older friend whom I fly control line with. Lately getting some in the air is very much  a hit and miss job. Lack of speed at launch is no doubt the problem. He thinks he is as fast over the ground as he was forty years ago however watching him go reminds me of that 70's TV show " Six Million Dollar Man " Where the hero's ability to run very fast was represented by him moving in slow motion accompanied by strange back ground sounds.😁

Working on a catapult launcher.

[Peter Jenkins]

20 hours ago, PatMc said:

The main problem isn't actually "torque roll", in fact its a yaw caused by it the rotating slipstream striking one side of the fin.    

Yes, there is the rotating slipstream but the effect of motor torque applied at too low an airspeed is also a major factor.  The yaw is corrected by rudder but the roll has to be countered by aileron.  The combination of the two can be disastrous. 

 

All high performance piston engine fighters, apart from those fitted with contra rotating props, had to be handled carefully when at low airspeed. Application of power smoothly was very necessary.  I heard that the Fleet Air Arm used to teach this problem graphically by getting the pilot converting to the Sea Fury to set up the landing configuration and speed at 10,000 ft and then slam the throttle open.  The aircraft performed a roll in the opposite direction to the prop rotation!  I have also seen a grisly sequence of photos that showed what happened to a P51 that did a long straight approach and so never saw the other P 51 taxy onto the runway and start his take off.  It was only when the P51 on the runway grew bigger than the nose of his P51 that he panicked and slammed open the throttle.  His P51 took a few chunks out of the P51 taking off narrowly missing that pilot and then ploughed into the grass on the runway side inverted and disappeared in a fire ball! 

 

Like I say, the combination of rotating slip stream and engine/motor torque at low airspeed is a problem.

[J D 8]

   One extra thing done with the 109 to counter the effect when powering up for take off was to pump up the left oleo leg good and hard.

[PatMc]

1 hour ago, Peter Jenkins said:

Yes, there is the rotating slipstream but the effect of motor torque applied at too low an airspeed is also a major factor.  The yaw is corrected by rudder but the roll has to be countered by aileron.  The combination of the two can be disastrous. 

 

All high performance piston engine fighters, apart from those fitted with contra rotating props, had to be handled carefully when at low airspeed. Application of power smoothly was very necessary.  I heard that the Fleet Air Arm used to teach this problem graphically by getting the pilot converting to the Sea Fury to set up the landing configuration and speed at 10,000 ft and then slam the throttle open.  The aircraft performed a roll in the opposite direction to the prop rotation!  I have also seen a grisly sequence of photos that showed what happened to a P51 that did a long straight approach and so never saw the other P 51 taxy onto the runway and start his take off.  It was only when the P51 on the runway grew bigger than the nose of his P51 that he panicked and slammed open the throttle.  His P51 took a few chunks out of the P51 taking off narrowly missing that pilot and then ploughed into the grass on the runway side inverted and disappeared in a fire ball! 

 

Like I say, the combination of rotating slip stream and engine/motor torque at low airspeed is a problem.

You're quoting my post out of context.

[Peter Jenkins]

1 hour ago, PatMc said:

You're quoting my post out of context.

In what way PatMc?

[Chris Walby]

Peter, I heard a similar story regarding Republic P-47 Thunderbolt's and a number of pilots that were killed as they applied excessive throttle on missed landing approaches. Inexperienced pilots were instructed to climb to a safe altitude and sequence through a missed landing approach (flaps, gear, landing speed) then apply full throttle. Shortly after this the aircraft would roll inverted hence teaching a valuable lesson that full power was not required for a go around and to be positively avoided.

 

In one of the interviews with Eric "Winkle" Brown IIRC it was landing a Mosquito on a carrier. Eric demonstrated with one of the "boffins" onboard a high altitude landing approach with a single engine failure. This resulted in the aircraft rapidity rolling to inverted and the conclusion that hanging a mosquito on the props when landing on a carried was a high risk task with little room for things going wrong. There appears to be no comment from the "boffin" regarding the high altitude inverted flying with a mosquito in its landing configuration, but I bet it was rather exciting!

[PatMc]

10 hours ago, Peter Jenkins said:

In what way PatMc?

The post that my comment quoted as reference, also the general discussion that prompted the quoted post.