Author Topic: Re: "Torque to me" can E-power help fix assymetric propellor effects? (Read 1237 times)

Dean Pappas · « **on:** November 18, 2007, 09:10:01 PM »

Hey Rudy,
There is no question, getting rid of the spiral slipstream, or at least having a pair that add up to zero, is a boon to trimming. Let me up the ante.

Short of someone building a wing with a visible warp ... have you ever seen a Stunter with a tab or wart that wasn't set to produce a roll inboard, when upright? i'll bet not. They are all bent down on the outboard end, or placved on the bottom of the outboard panel, aren't they?

It's there to counter the spiral slipstream from the prop. What's more, a tab on the tipo is all wrong! Instead, the leading edges behind the prop should be tweaked, like a STOL cuff, inboard side down and outboard side up.

Twins solve this problem, as would a contra-rotating prop on a single. So many things to try! HB~>I could spend a whole nuther lifetime doing experiments.

later,
Dean

Rudy Taube · « **Reply #1 on:** November 19, 2007, 02:32:57 AM »

Hi Dean,

I agree, it helps, that is why we are using the CR props on Will's twin. :-)

Great points all. Your right, I have never seen a trim tab pointing up on a CL plane. Mine is down too. Your ideas do up the ante, Your LE tabs are an interesting idea, but I like your contra-rotating props the best for single motor planes.

We need you to win the Lottery so that you can have a 100 person R&D team to get all your ideas worked out for us in "this" lifetime! I would much rather be flying the perfect Bob&Dean ECL plane every day than messing about with testing power systems!

At least you are making major bucks being the moderator of this forum. This should allow you to retire early so you can get started on your R&D mission!

Dean Pappas · « **Reply #2 on:** November 19, 2007, 10:11:54 AM »

Ah yes, the big moderator bucks!

I like the idea of contra-rotating props for single motor planes too.
The gearbox mechanism is straightforward: the fixed ring gear of a planetary gearbox becomes the opposite direction output shaft.
The two props torque-share, providing no spiral airflow at a variety of airspeeds and without needing specially pitched props.

later,
Dean

Igor Burger · « **Reply #3 on:** November 19, 2007, 12:25:34 PM »

I think gear boxes are too complicated for contra props, here you can buy ready to use motor:

http://www.pjs.cz/product_info.php?products_id=52&language=en

Alan Hahn · « **Reply #4 on:** November 19, 2007, 03:53:52 PM »

So I am not sure that it matters, but I guess you can run the two motors at different rpms (or they do not necessarily turn at the same rpm).

Igor Burger · « **Reply #5 on:** November 19, 2007, 04:01:21 PM »

they do not, but why you thing the optimum is at equal RPM? ... you have two independent governors, so you can make them to do whatever you want

Dean Pappas · « **Reply #6 on:** November 19, 2007, 09:14:01 PM »

Hi Alan, Hi Igor,
It turns out to be a can of worms! Fortunately we have both mechanical and electrical means to find a bigger can, because once you take worms out of the original can, they never fit back in!

1) If and only if you ran two motors at equal RPM, then the pitches must be different, and the difference will only work best at one airspeed. Fortunately we fly at a remarkably constant airspeed but this is still not the ideal.

2) If and only if you run equal pitches and different RPM, the same is true as above.

3) If you run a load or torque sharing differential between a single motor and two props of almost arbitrary pitch, then both props will impart the same torque to the airstream at all speeds and power settings, though it may take a fraction of a second for things to settle every time a drastic load change occurs.

4) On the other hand, if the sum of both motor RPMs is governed and the current of each is sensed, and the difference in the two controlled RPMs is controlled so as to produce the same drive current (torque) in each motor, then the same benefit as #3 can be had. There is a settling time issue, but for control loop reasons.

I vote for #3, but I like gears levers and belts because I design circuits for a living ... go figure!
For sure, all 4 approaches will work. I wonder what is lightest? It's probably a tie.
I know that the German Michael Ramel makes a differential gearbox for 3KW motors that weighs under 80 grams.
his website is something like www.f3a-e-factor.de, but site comes up saying it is overloaded. I think that's what uberarbiteit means.

I can't wait to see who solves this design task,
Dean

Igor Burger · « **Reply #7 on:** November 20, 2007, 01:26:33 AM »

>>>uberarbiteit<<<
it means the site is in reconstruction

... may be one photo from F3A WC Argentina

http://image2-3.rcuniverse.com/e1/forum/upfiles/158551/Sx61863.jpg

Rudy Taube · « **Reply #8 on:** November 20, 2007, 02:23:14 AM »

Quote from: Igor Burger on November 20, 2007, 01:26:33 AM

>>>uberarbiteit<<<
it means the site is in reconstruction

... may be one photo from F3A WC Argentina

http://image2-3.rcuniverse.com/e1/forum/upfiles/158551/Sx61863.jpg

Igor,

Now you have done it. Dean is going to have to change his shorts after seeing that beautiful photo!

It looks like it is Not only doable but "DONE"!!!!

Thank you,

Dean Pappas · « **Reply #9 on:** November 20, 2007, 09:03:17 AM »

Hi,
We toy airplane nerds get excited over the darndest stuff!

That is Sebastiono Silvestri's plane, and it has a Hacker motor with a clone of the Ramel designed E-Factor gearbox that many of us saw about a year ago. It sure does work. Michael R. told me that he couldn't believe how much subtle trim had to come out of the first airplane he retro-fitted the contra-gearbox into. Now, the loop trim really works without compromise, and the plane goes dead straight when slowing to near stall speeds for the spin entry. In the past, it seemed that there was always a tiny, tiny bit of right rudder trim needed, no matter how much right-thrust you put into the engine, and some guys are even using transmitter electronics to remove that tiny right rudder trim at dead idle so the stall does not favor one direction.

And you thought I was speculating!

Dean

Dennis Adamisin · « **Reply #10 on:** November 20, 2007, 09:14:18 AM »

Another variation: recently Keith Shaw wrote up (in MA?) his experiences setting up a Bugatti-100 racer in which he used 2 motors to drive the contra-props. He monitored individual current draw then adjusted gearbox ratios to equalize the loadings on the two motors. In the process his airspeed climbed from something like 65MPH to 90MPH...

Rudy Taube · « **Reply #11 on:** November 20, 2007, 10:16:21 PM »

OK Dennis, Now you have gone too far! .... You, Dean and Igor are starting to give me a headache.

Just when I thought my ECL setup was PERFECT, you guys go and show me how my system is "so yesterdays news"! Just when I thought I could stop all this silly experimenting, and finally get to go out and FLY, I realize that there is something even better out there. This progress thing has gone way to far and it must stop!
I'm going to join the "Only wimpy Fox .35s ( .2 HP?) are allowed in CL, and ALL CL planes have to be carved from a balsa log grown by the BOM" crowd and put a stop to all this "HI ZOOT" progressive electric stuff!!!!

On a more serious note, as Dean originally said, contra-rotating props will solve some important trimming problems. As a side benefit they will also solve a ground clearance problem as we move toward more powerful motors for our future 900+ sq in 90+ oz super planes in 2008 and beyond. These larger planes will require some SERIOUS prop sizes. Two contra-rotating 14 x 7 props will be AWESOME in flight. .... Weight lifting may become an important part of a CL pilots training program?

Here is a link to the AXI Contr-rotating prop motor:

http://www.hobby-lobby.com/brushless-axi5330.htm#Double

Thanks Dennis for the speed info. This idea may become more common in ERC and ECL as the motor mfg. develop these two motor combos with a shaft inside a shaft to drive the two props.

IMHO: E-power will take over RC in the next few years but it will be MUCH slower to take over CL because of the very entrenched "Fox and balsa log only crowd". .....But my guess is; that the next few years are going to be very exciting for ECL!

Warm Regards,

Dennis Adamisin · « **Reply #12 on:** November 21, 2007, 12:36:38 AM »

Rudy-me-boy, I'm afraid we are at that stage where as soon as we BUILDs an e-power set-up it is OBSOLETE! Things are moving so far and so fffast! If I may paraphrase, our technology has the shelf life of a bannana!

Back in the mid 1980's when my Dad built his Astro 15G/10 cell Yo-Yo OTS it flew pretty well but was just a curiousity.

Still got that motor/gearbox by the way...

Last summer I converted the Oriental to e-power and probably progressed to about 2004. Gave the bird to my Nephew and he has it advanced to about mid 2007 - which means we are halfway to where we will be for 2008!

Contra-props have their payoff, but I am not sure the pain is worth the gain using 10"-11" props. However if you are ready to use 14"... Maybe you got something there feller!

So, you ready to replace that P-40 with a Westland Wyvern???

Just like the dark arts boyz, we will continue to use IC engines in a lot of CL. But I gotta believe that within 5 years e-power will be the standard. You can still carve your 2012 model fuselage out of a log - but fit it with E-power, and then fit it with a dummy engine cylinder to carry the ESC!

Rudy Taube · « **Reply #13 on:** November 23, 2007, 11:15:32 PM »

Hi Dennis,

I'm sure you knew I was just kidding in my last post. I may not be as big a "techno freak" as Dean, but I am very close behind!

I agree with you that ECL progress is moving fast, maybe not as fast as a banana, but still fast. It has not been a situation where the technology has improved rapidly as much as it has been a factor of DISCOVERING what is really out there already and experimenting with different mfg. offerings. There are still wonderful E-power products from Japan, and Europe that we have not discovered and/or used yet.

Thanks to the world of the Dark Arts we have many items to choose from. These items will continue to be improved, even if only by small advancements in performance and quality. Most of the things we discuss here, CR props, a real ECL 4/2 break, etc. are in our ECL future, but not anytime soon. But by talking about them and sharing our ideas we will hasten their arrival.

I hope anyone reading our posts understands that the original "turnkey" setup of an: AXI 2826, Castle Creations 40 ESC, JMP Timer, 4,200 mAh 4 cell 14.8V battery, is equal to, or better than, most of the IC setups out there in the mid size A/C (500 to 600 sq in, 45 to 55 oz range). And that the items on Mike Palko's "ECL Equipment" post at the top of our ECL section of this forum are still valid and will give any ECL pilot a power system that is as powerful, and more reliable and repeatable than any IC power system out there. Since 2S and 4S systems are close to being at their MAX development for CLPA, I feel that the ECL system someone buys today will stay ahead of the IC systems for years to come.

Anyone buying an ECL system now will be happy with it for the next few years. IMHO: There will be improvements, but I don't think anything will make a system "obsolete" every year, unless you are competing at the very top levels of our affliction!

Items like the Jeti-Spin ESCs may be an improvement, but only a small one. The CC ESCs are still excellent for ECL and people will continue to be happy using them. We will see new Timers soon, but the JMP and new Ztron are still very good for our ECL planes and will continue to work just fine.

Soooo, just because Dean, Mike, Will, me, you, Igor, Alan, Ron, Kim, and many others, continue to stretch the hi tech "Hi Zoot" envelope, it does not mean that someone buying todays system will find it obsolete anytime soon. Even the best IC Engine on a pipe did not fly any better than my ECL setup (above) did this contest season. ...... MANY of the PILOTS did, but NOT his plane!

Your right, progress will come. And it will be a FUN ride for all of us. 2008 is going to be a BIG year for ECL. Howard Rush, Brett Buck, and other top pilots were VERY interested in my ECL setup at this years CA champs. I think Paul will have some serious ECL competition very soon.

Warm Regads,

Author Topic: Re: "Torque to me" can E-power help fix assymetric propellor effects? (Read 1237 times)

Alan Hahn