Counter-rotating engines! Who does this?  
View related threads: (in this forum | in all forums)

Tower Hobbies
Enter up to 4 keywords or Tower stock numbers
Logged in as Guest



Users viewing this topic: none
  Printable Version
       

All Forums >> RC Airplanes >> Twin & Multi Engine RC Aircraft >> Counter-rotating engines! Who does this?
Page: [1]

Login
Message << Older Topic   Newer Topic >>
Counter-rotating engines! Who does this? - 5/10/2008 11:17:15 PM   
Avaiojet


 

Posts: 147
Joined: 9/25/2002
From: East Greenwich, RI, RI, USA
Status: online 		I'm not sure I need counter-rotating engines.

The project is a 66" span twin.

Any manufacturers offer this? Who?

Be nice if it can be done in 4S.

Thanks in advance.

Charles
       Post #: 1

RE: Counter-rotating engines! Who does this? - 5/11/2008 4:18:35 AM   
JohnBuckner



Posts: 3667
Joined: 12/23/2001
From: Kingman, AZ, USA
Status: online 		Possibly a more practical method in taming the twin is the use of outthrust. Simple out thrust eliminating the difficulties in obtaining courter rotation as well as the added hassle you will have with props.

I have a scale Waco PG-1 with .15's - five degrees outthrust, A Seniorita with .25"s -adjustable outthrust 0 to 10 degrees (This one for training folks to properly fly and control a twin on one engine), Two Wing Mfg. kit P-38's with .46's four degrees outthrust, A Senior Kaydet with four .25's - inboards two degrees outthrust and outboards four degrees outthrust and a Telemaster with six .25's - zero degrees outthrust all engines (loss of sveral engines is almost a non event so no need for the outthrust).

All with the exception of the Six Pack with only several flights now have been flown extensively and deliberately at times (by using the known short tanking technique) with engine(s) out and under total control. All are standard rotation. Outthrust is an excellent method without the hassle of CR.

John

< Message edited by JohnBuckner -- 5/11/2008 4:21:29 AM >

_____________________________

"Keep your controllines tight"

(in reply to Avaiojet)
       Post #: 2

RE: Counter-rotating engines! Who does this? - 5/11/2008 4:55:53 AM   
kram



Posts: 438
Joined: 7/11/2002
From: ames, IA, USA
Status: offline 		Charles:

In summary, NO, you don't need counter-rotating engines or out-thrust.

Model twins fly just fine without them.

It is a much wiser investment of your time and energy to make sure both engines will run reliably.

There is clearly a "glamor factor" to have counter-rotating props, of course. They will attract more attention at the field, from know-nothings to experts alike.

Of the dozen or more twins I've owned, only two have counter-rotating props, the CBA-38 I bought with the DA-50's already installed that way, and the Duellist I built 15 years ago, rehabbed last year. Interestingly, their counter-rotators (by kit maker advice) are on opposite sides! I can't tell any handlng difference with either of them except maybe a little more axial roll stability. I have not had an engine-out on either one of them, but I wouldn't expect the counter-rotation to help if I did.

Like I said: KEEP BOTH ENGINES RUNNING!

The late, great Bill Robison, Saito expert extraordinaire used to describe how you could get a reverse crankshaft for some Saito FS's, but I don't know of anyone who actually did it. Look up some of his old threads.

What's yer project?

Mark

Thanks, kmot!



Attachments
Click to see fullsize image.
Click for fullsize 		Click to see fullsize image.
Click for fullsize


< Message edited by kram -- 5/11/2008 5:10:33 AM >

(in reply to JohnBuckner)
       Post #: 3

RE: Counter-rotating engines! Who does this? - 5/11/2008 12:00:13 PM   
Avaiojet


 

Posts: 147
Joined: 9/25/2002
From: East Greenwich, RI, RI, USA
Status: online 		Mark and John,

Thanks for the reply.

Done!

With your advice, I no longer have to consider CR props. Wouldn't it be great if "everyone" was that easy to convince?

The project is the Bamboo Bomber at 66". I'm looking into a larger one, but not the one which is offered at 100".

70" to 80" would be ideal. I can have the "vintage" plans I have scaled with no difficulty.

I have to determine if the plans I have are drawn releativly corectly. Most important is the necelle diamiter. It appears a bit smaller. I'm thinking two good 4S for the greater prop diamiter and the more convienent muffler.

It would be nice to have retracts, but I believe retracts are an issue. I have to look into that also. The Bobcat has gear that works similar to the C47 but with only one main strut. I'm sure there's nothing available?

Thanks for your advice and please continue with it.

I'll porbably Post for information for others that have modeled the Bobcat.

Charles

(in reply to kram)
       Post #: 4

RE: Counter-rotating engines! Who does this? - 5/11/2008 2:23:53 PM   
kram



Posts: 438
Joined: 7/11/2002
From: ames, IA, USA
Status: offline 		Sounds like a unique and fascinating project!

Sorry to say I know nothing about that particular plane or the kits and gear available for it.

I forgot to mention that the reverse DA-50 engine is a factory ignition mod that DA can do for you. Props are hard to find, all wood, and limited size selection. The reverse engine on my Duellist is a 15 year-old O.S. .46 "R" which came with a reverse crankshaft and reverse prop threads. I don't know if they sell it any more. APC has a decent selection of "pusher" props in that size range that you have to fill in the grooves and install backwards for a forward-flying engine.

I'm glad we talked you out of all that.



mt

(in reply to Avaiojet)
       Post #: 5

RE: Counter-rotating engines! Who does this? - 5/11/2008 8:09:41 PM   
zipman



Posts: 53
Joined: 1/16/2002
From: East Brunswick, NJ, USA
Status: offline 		Hi Avaiojet,

I have the Cessna UC-78 Bobcat plans you mentioned (RCM 1964, twin .35 cu in engines). I am laying out the build now and plan to go electric instead of glow. The plans are not quite scale and compared to the Paul Matt 3 views there are some outline discrepancies. You have to remember that when these plans were designed they were still using R/C Reed control technology, not true proportional control, not to mention the weight of the servos, receiver and battery were over 2 pounds. So you can imagine trying to make a stable twin engine model back then. I will build it according to the plans except where I can save weight. An online friend of mine AL Sortwell built the plane using glow engines. Here is a picture of his model. I sent the plans to Dynamic Balsa www.dbalsa.com and had them make a set of foam wings as they do for a lot of the published plans. My eventual goal is to get a set of Don Smith’s 1/5th version and power it with 25cc gas engines.

I did find this short kit for a model of the size you want on E-bay but it must be over priced because no bids and it is going to end today. Also the shipping is ridiculous.
http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&ssPageName=STRK:MEWAX:IT&item=160237301630
It may get re-listed at a more realistic starting price.

As far as retracts check Robart Manuf. Here is the link.
http://www.robart.com/retracts/Custom.aspx see the 5th from the bottom of page for the Bobcat gear for Don Smith’s plans. Click on dimension drawing and the parts list for a very good scale picture of the gear. If you can do metal work you might be able to make one in your scale.

Good Luck. Let us know how you make out.

Stan


Attachments
Click to see fullsize image.
Click for fullsize 		Click to see fullsize image.
Click for fullsize



_____________________________

Stan

(in reply to kram)
       Post #: 6

RE: Counter-rotating engines! Who does this? - 5/12/2008 12:43:00 AM   
JohnBuckner



Posts: 3667
Joined: 12/23/2001
From: Kingman, AZ, USA
Status: online 		.

Attachments
Click to see fullsize image.
Click for fullsize 		Click to see fullsize image.
Click for fullsize 		Click to see fullsize image.
Click for fullsize


_____________________________

"Keep your controllines tight"

(in reply to zipman)
       Post #: 7

RE: Counter-rotating engines! Who does this? - 5/12/2008 7:52:40 PM   
jaka


 

Posts: 4348
Joined: 12/11/2001
From: Upplands Vasby, SWEDEN
Status: offline 		Hi!
I think MVVS is the only manufacturer these days who makes counter rotating engines.
But to have a left and right turning engine isn't necessary. But If the original full size had it ...It would be nice to have it in a model too.

Attachments
Click to see fullsize image.
Click for fullsize


_____________________________

Jan Karlsson Airracing products
MVVS, Motul "Micro" all synthetic oil

(in reply to Avaiojet)
       Post #: 8

RE: Counter-rotating engines! Who does this? - 5/14/2008 3:58:17 AM   
sledge_78


 

Posts: 153
Joined: 12/30/2004
From: Scottsdale, AZ, USA
Status: offline 		Aviojet,

I would say listen to the good avice from Kram regarding the counter rotating engines. On a model it appears to have no performance improvements. At least that is a consensus from all the opinions I read here on RCUniverse. My flying buddy and I had a long time debate on why it seemed more difficult to make right turns Vs left turns. The debate centered on the engine rotation and the resultant torque making left turns easier. So I found a reverse rotation crankshaft for a K&B .61 installed it on the same airplane I normally flew to test the theory. It made absolutely no difference in making turns. However, it is a conversation piece at the flying field. Overall, the advice is good spend the effort to get the engines to run properly. Tune each engine separately so it will perform the way you would like if there were only one engine on the plane. Don't worry if the RPM's are not in sync perfectly. like the counter rotaing engine, it won't make a difference in performance. Some airplanes will fly OK on one engine without any radical effect if the engine stops. A Twinstar for example will fly just fine on one engine. You will need to learn to use Rudder, and not turn into the dead engine. Most P-38's can be a handfull when one engine stops. I have heard where the use of a Piezo Gyro for rudder will save the day on a P-38 with a dead engine. Gain some experience with twins. Start with something simple like a Twinstar with a pair of .25's. Save the scale P-38 for the time when you are ready to handle it. Also, you don't have to over power a twin to get great performance. My Twinstar flies really fast with OS .25FP's and no problem on one engine either.

Good luck, keep us posted

Sledge_78

(in reply to Avaiojet)
       Post #: 9

RE: Counter-rotating engines! Who does this? - 5/16/2008 7:32:00 PM   
Hassansassd


 

Posts: 9
Joined: 1/16/2005
From: Budapest, HUNGARY
Status: offline 		Hey Avaiojet,

Since I am makin an OV-10 twin engine Bronco I found many informations about multiple engined planes. I was looking for engines that sold in pairs and one of them is counter rotating. I found this URL that tells u mostly everything:

http://www.enya-engine.com/store/index.php?main_page=product_info&cPath=23&products_id=418

http://www.enya-engine.com/store/index.php?main_page=index&cPath=23&zenid=737f9059d7921dc540c567655f5e4977

Good Luck!

Hassan

(in reply to sledge_78)
       Post #: 10

Page:   [1]
All Forums >> RC Airplanes >> Twin & Multi Engine RC Aircraft >> Counter-rotating engines! Who does this?
Page: [1]





Jump to: