Is An OS 55AX The Right Engine?
 

I've got a Das Little Stick with a Super Tigre G-51, pipe and header (14,000 with an APC 12.25x3.75) that I love flying. 4lb plane, stupid vertical. I'm not into 3D just lots of POOWWWAAAHHH.

Well I want a bit bigger plane (and flaps) so I'm thinking about getting an Ultra Stick 40 which is a 5.5 to 6lb plane. If I put an OS 55AX on it with pipe, header and something like a 13x4 or 13x5 will I get stupid vertical like my Little Stick? Or will I have to put a 61 or so on it. If I need it bigger Imay look at a Jett 60 or 76 for it to save the weight.

RE: Is An OS 55AX The Right Engine?
 

In that case forget about the 61 size engines (not the Jett, they`re in a leage of their own)and go right to the 91 size. Basically the same casing and weight but like you say, stupid vertical;)</p>

Your 51 seems to be performing amazingly well and I don`t think the AX 55 will be a significant raise over thepower you already have</p>

RE: Is An OS 55AX The Right Engine?
 

If you don't think a 55 is strong enough for a 5.5 pound plane you might as well put a 120 on it. Sheesh!!! What IS this imagined need for EXCESSSSSSSSSS POWAAAAH that is soooo prevalent these days? My 5 pound Lucky Stik has very good('til it can't be seen) vertical with a ST 45.Can hover too.

Terry in LP

RE: Is An OS 55AX The Right Engine?
 

"These days"???

Sheesh!! I was like this in the 80s when I built three little sticks with an OS 40, 46 and 50 on them with pipes and headers. My need for POWAAAAHHHextended into the 90s with drag racing (full size cars). Some of us just like stupid power. I had a turbocharged mustang that had well over 700hp that I drove every where. Of course you can only put 500 or so to the ground but it was fun trying to put all of it on the ground!

If it makes you feel better, an H9 Fokker D7 is on my list as well with a Saito 82. http://www.rcuniverse.com/forum/js/f...eeth_smile.gif Very sweet flying plane to just relax with. But most of the time I like the motors on my planes to sound and run like they are snarling / spitting mad.http://www.rcuniverse.com/forum/js/f...sn/thumbup.gif

RE: Is An OS 55AX The Right Engine?
 

Tower had the Super Tigre G-90 on sale for $99 and with the discount that is closer to $80. I should have bought one! I'm just worried about the weight of the "big block" motors.

RE: Is An OS 55AX The Right Engine?
 

The OS 61 FX weighs 700 grams, muffler included, the 91 fx weighs 770 grams, muffler included, the Magnum 91 weighs 725 grams, muffler included.
So you see the difference between a 61 and a 91 is very small, but power is way bigger in the 91.

If you want a really powerful and light weight 91 then get the Magnum 91 and fit a Tower 75 muffler to it and you are down to 680 grams. Yes, that is lighter than a normal 61 but far more power. 

RE: Is An OS 55AX The Right Engine?
 

So..? You could be flying all your models with LA 40`s for all I carehttp://www.rcuniverse.com/forum/js/f...wink_smile.gifNobody said a 55 isn`t strong enough for a 5.5 pound plane, I don`t know where you think you read thathttp://www.rcuniverse.com/forum/js/f...n/confused.gif
But this guy wants stupid power/vertical so he needs a powerful yet light weightengine and that is what I have prescribed.

Besides I have used 120`s on 5.5 pound of plane and it is really fun. Had a YS 110 on a 5.8 pound plane too and it was fun also.
To each his own I guess, we can`t all fly underpowered Cub`shttp://www.rcuniverse.com/forum/js/f...sn/redface.gif

RE: Is An OS 55AX The Right Engine?
 

Even if I do put a .91 on it, I'll still put a pipe and header on it!


[golf clap] Amen brotha! [/golf clap]

RE: Is An OS 55AX The Right Engine?
 

I have an Ultra Stick 40 with an OS.55 in it using an APC 12-4. It has good climb, but not eye-watering climb.

I tested the .55 on a 12.25-3.75 APC with a Jett tuned muffler. I tached 14,500 on 10% castor blend fuel. With a tuned pipe, I'd figure another 200-300 rpm so make that 800 more than your Tiger. This still won't give you stupid climb.

I used to fly tuned pipes all the time, but finally just went to larger engines. I'd put a .91 in it.

RE: Is An OS 55AX The Right Engine?
 

Good info. Thanks for the reply!

Yea, it looks like that is what is going in it then. A SuperTigre G-91.I knew I should have bought one when Tiger had them for $99 last week!

Are there any weak points in this plane or will the 91 make all kinds of new weak points that I need to reenforce? The firewall area is a given but anything else?

My little stick will take off in 10 feet or so at half throttle, climb straight up and do an aileron roll just about as fast as if it were flying straight. Plus the sound of a screaming engine coming on a pipe (its a muffled tuned pipe) is just pure music.

RE: Is An OS 55AX The Right Engine?
 

I flew an ultrastick 40 with an OS91FX on it for 4 years with an apc 13-8 prop. It was great with the firewall reinforced with round toothpicks from the sides. Because of stress concerns a friend now flies it with a TT46.
Due to vibration keep an eye on the wing dowels for wear or place brass tubing over the dowels.

RE: Is An OS 55AX The Right Engine?
 

Real planes don't have such power...
Let's compare a high-wing aileron trainer, to a Cessna 162 (Skycatcher, the 152 replacement).
This plane powers its 1,320 lb. MTOW, with 100 HP (Continental O200D), meaning 13.2 lbs per HP...

A .40-.46 engine realistically puts out about 0.9-1.1 HP.
Realistic power is flying a 5 lb., .40-.46 sized trainer, off a paved runway, with a standard .12-.15 engine in the nose.

Anything more than this would be overpowering it... Even a standard .40 has a 170% overpower!

That Cessna climbs-out at a 10-15° up trajectory. Vertical??? What the hell is that?


Flying right is power management; not overpowering.

RE: Is An OS 55AX The Right Engine?
 

Flying "right" is subjective and can vary from one end of the spectrum to the other. There is no one "right".

Remember when most of our R/C models had to be flown at wide open throttle? You may not, because of our age difference. No, this is not a put-down. I have no put-downs for my RCU friends. I enjoy flying models in about every way imaginable. I like slow models, fast models and in between speed models. Why limit oneself to just one style?

One of the most enjoyable models I ever flew was a Cox RTF Sportavia guided by a two channel Sanwa radio with an .049 Cox engine in the nose. I wish I could find another one to buy and fly. The last one that I flew belonged to a friend. A beautiful handling model for only having rudder and elevator control.


Ed Cregger

RE: Is An OS 55AX The Right Engine?
 

[quote]ORIGINAL: DarZeelon

Real planes don't have such power...

[/quote}

Really???? Ever heard of Wayne Handley and his Turbo Raven? The plane was lost several years ago due to engine failure but his signature move was to fly straight up, stop, tail slide some and then continue flying up.

I'll agree with that. I did try some pylon racing in my younger days but it wasn't for me. I rarely fly my planes these days flat out all the time.

RE: Is An OS 55AX The Right Engine?
 

Thanks for the engine lesson! So you do or don't think an OS 55AX is the right engine? Don't think I read that any where in your pst.

Ever heard of Wayne Handley and his Turbo Raven? That was a real plane that had such power.

"Flying right"? I guess all of the 3D pilots all over the world are doing it wrong?

RE: Is An OS 55AX The Right Engine?
 

The G-90 ISbased ona 61 size engine. The "big block" you speak of would be like the old OS .90f sr. They are much larger in physical size and weigh more.

RE: Is An OS 55AX The Right Engine?
 

Yea, but I still may get the ST-75 instead. The pipe for it is quite a bit cheaper and easier to get. The 90 requires a step up to a 15cc pipe which is quite a bit bigger and more expensive.

Don't know. Still in the planning stages. I was really hoping the 55AX was going to do it for me but I guess not. The Jett stuff is really cool but he is very proud of his work. Still may consider a 60 or 65 from him.

RE: Is An OS 55AX The Right Engine?
 

That would be awesome, I really want a Jett too. I go to his site every now and then and dribble all over the Q500 racing engine:)

RE: Is An OS 55AX The Right Engine?
 

If you want the most power in that size range, you should consider a Sanye (Magnum, ASP, SC, etc.) .91 two-stroke engine, or even the Tower Hobbies .75 two-stroke engine. The latter is reputed to be very hot and well behaved. When I was looking for an engine in this size range, the TH .75 was out of stock, so I opted for an ASP .91 two-stroke and haven't been sorry once. The stock TH 61/75 muffler has a reputation for being a hop-up item for other engines which fit the mounting bolt pattern, such as OS.

I am a Super Tigre fan. However, I do not feel that it is the power leader in available two-stroke engines in this engine size/price range. I own several G90's, so I do speak with some hands-on experience.


Ed Cregger

RE: Is An OS 55AX The Right Engine?
 

I totally agree. I have owned the hyped up Tower .75 and I owned the ASP XLS .91. One example: Tower .75 and APC 13-6 turned 11700 rpm, ASP XLS .91 turned the same prop 12900 rpm. Difference in weight was 1 oz.. I sold the Tower and kept the ASP (which is now sold too, but only because I had no need for it anymore)

I found that there was nothing magical about the Tower .75, it is a little less displacement than a .91 and develops less power as is to be expected. When the difference in weight is so small I`d opt for a .91 every time

RE: Is An OS 55AX The Right Engine?
 

I agree that the .90 or .91 has more power in the same size/weight as the .61 or .75s but the pipe required is quite a bit bigger for a 90 sized motor. The 60-75 sized motors call for a 10cc pipe and the 90 has to jump up to a 15cc pipe. But hey, I still may opt for the 90 just for the "double engine requirement factor" that I had on my .25 size Little Stick. LOL! What happens when you put a 10CC pipe on a 15cc motor? One thing I found very interesting when I was tuning the G-51 on my little stick was just bolting a header and pipe on the motor increased the RPMs by 1000. Tuning the pipe got me even more of course.

I've had such good luck with SuperTigre's that I'm probably going to stick with them for this project but that ASP has my interest as well as the TH 75. And with the Tower super saver discounts the Tower and SuperTigre engines can be had for a really good price. So keep the suggestions coming, all good info!

One other thing to consider is prop size on a .40 sized model. I think it is a given that I'll have to get some taller gear for the Ultra Stick (I had to make my own for the little stick) but I was wondering if a 75 or 90 size motor with a header and pipe will swing a 14x4W or 15x4W? I've had .40 sized engines all my R/C "career" so I'm venturing into new territory here. The 12.25x3.75 is a really sweet combo on the G-51, what would the sweet spot be fore a G-90?

RE: Is An OS 55AX The Right Engine?
 

<font size="2" color="#00265e">SpinnerRow</font>

You can use a longer header to use a 60 size pipe (especially one that isn't 'peaky') on a 90. Or make a moussecan type pipe for similar results, less weight and expense. You might try something like a 12~12 APC on a piped ST90 for around 11,000rpm if you want some speed.

Terry in LP

RE: Is An OS 55AX The Right Engine?
 

If you go for a 91 then you really don`t need to use a big pipe because you already have more than enough power, just bolt the engine on and go.
 You can use a 12x10 and will not have ground clearance problems.

The Tower 75 I had turned the APC 12.25x3.75 at 15000 rpm even (I did mod it a little) But an APC 13-6 turning almost 13000 rpm on a 91 is even better and gives better vertical and also more speed.

RE: Is An OS 55AX The Right Engine?
 

Oh I know. I just love the sound a motor makes on a pipe. Besides, this thread is about gluttonous excess! In my limiited experience with the SuperTigre quiet muffler, there is significant power to be had just bolting on an untuned pipe and "stupid" power with a little tuning. Plus the pipe and header are just a itty bit lighter than the stock exhaust.

I plan to buy the plane in a week or two and the motor a couple of weeks after that and then I'll start a build thread in the ARFsection and solicit advice on reenforcing the airframe for the "Gluttonous Excess" I'll be subjecting it to - which is what I will probably title the thread! So all you "underpowered cub" fliers can follow me to that forum and continue the lambastation there! http://www.rcuniverse.com/forum/js/f...eeth_smile.gif

I'd like to put some Hitech HS225-MG servos in the wings if they would work (flaps/ailerons) without killing them. Otherwise, I'll put some HS-5485HB in it. The 225s would save me a couple of ounces that Ineed to recover with an 8 ounce heavier motor. I may even put an A123 battery in it to save more weight.

RE: Is An OS 55AX The Right Engine?
 

OK, OK, we are way off subject here.

We can conclude that most folks here are sure that the Rolls-Royce AE 2100D, spinning a Dowty R391 prop, will provide just enough power for a .40 size 3D plane...[:'(]

Seriously; there is absolutely no need and no advantage, in installing a heavy .91 engine in a .40 model. You are all wrong!
It will not fly as intended, or as gracefully, as it would with a .40-.55 engine.

It will also land like an anchor; not like an eagle...


Why don't all of you guys opt to install a 16,000 HP marine Diesel, in your next family car? Good idea, no!?


The question was regarding the replacement of the ST .51 with an OS.55AX, for a little extra power (POOWWWAAAHHH)... Not getting unlimited vertical performance, with the engine idling...