I posted this message at the end of another thread, but did not get any response, so I thought I would try it again. I have a prop question. I have an OS 46 AX engine on my H-9 Pulse XT. The engine manual recommends a 11 x 6 for break-in. After that, the manual says I can run a 10.5 x 6, 11 x 6-8, or 12 x 6-7. I don't need to have the fastest plane, but curious if anybody out there has any experinece trying different props and what seemed to work the best for this plane or engine.
Thanks

mesaflyer: My buddy has a Pulse XT with OS 46 and has good luck with 10x6. I've flew it and it has plenty of power and get up and go. Kinda depends on the kind of flying you do but good alround prop.---------Revver Bro#164

I was asking about the engine and someone said a MAS Master Air Screw 11x7. Well they said it's good for beginners (me)

11x7 will be running below the peak power point. It will be quieter though.

11x5 or 10.5 x 6 seems to be the sweet spot for this engine.

I have the OS 46 AX on my sig something extra and I run a 11-6 prop on it.

I beleive the smaller size props will make it faster once it's in the air and the larger size props will give you less speed but better pulling power.

On take offs smaller props = longer runway to get it airborne.

Larger props = shorter runway to lift off.

I beleive the more rpm's you get out of an engine = more wear on your engine.

Experiment with different props and then you will know.

If I had the pulse I'd run a 11-6 on it with the os 46 ax.

11x5 has been ok on all those engines at our field. A number of fliers have had better luck with 11x6s.

10x6 used to be the accepted standard for 35s. All the guys who've run them at our field on the 46AX have changed to larger props. Well, one guy still is running a 10x6 but he loves speed and screaming engines. I've tried to talk him into trying a 10x7 or 10x8 but he hasn't so far.

You can find a range of props for that engine. It all depends on what performance you want. Smaller pitch props (the second number in the prop size) will usually cause more RPM. So, you will have to watch that so you do not exceed the max RPM for your engine. It is not unusual to get 12,000 RPM out of that engine when it is running correctly and correctly prop'ed.

Think of the pitch as changing gears in your car transmission. Lower gears relate to lower pitch numbers. You get more power, faster acceleration, higher RPM, but less speed. Higher pitched props will give you less power, slower acceleration, lower RPM, but higher speed. But, at limits. You cannot, for instance put a 15-10 prop on a 46 sized engine. It will run, but you will never get the thing off the ground.

I used to run my OS 46AX at 13600rpm with the 10x6... I killed the engine after a while
Note that in the catalog they specify a theoretical range up to 17000rpm with a power peak at 16000rpm (never happens in real life)

I bought another one, installed the 11x5 and 11x6 and event went up to the 11x7 then 11x8; and finally tried the 12x4 on 3D planes
They all run differently, but I feel you get the best out of this engine with the 11x5, 11x6 and 12x4. It depends on what you need.

After all, the manufacturer, for breakin, I think, should be recommending the ideal prop in its manuals

Hi!
What's an ideal prop??

The one that won't bite your fingers!

Using a 10 X 7 prop with the AX46 is the answer for performance. It puts the engine in the power range for max power without over reving.

Yeah I know you are right, the ideal prop depends on what you want to achieve but in the contest of our conversation, I meant the prop that puts the engine in its comfort zone and achieve good power output in relation to its fuel input and/or weight...

what the rc world needs is a nitro size variable pitch prop. I have the rimfire v-pitch on my flatout but haven't flown it yet.

I use the 46AX on my race T34's and I run 9.5x6 APC at upto 17200, 9.5x7 Bolly at 15000 and 10x5 APC at 16500, the fast one is the bolly, the engines in these planes have been know to last for 2 or 3 years, or 1 year and then make a great sport engine. We run them at the limit, but I know one of the guys put a 46AX on a skyraider mk2, to make sure he did not rip that plane open he used a 12x4N, he says it is real slow but great pulling power, for a beginner that would be the best way to go big low pitch prop. Also get some good after run oil, I use http://myrcsupply.net/index.php?main...ed377e446ebc17 and it is great it will look after the engine well if you take the higher RPM option.

Also in another post this engine on a small prop my plane will take off across the runway at my field with is about 65ft.

Just an FYI... I looked at my paperwork for my OS 46 AX and a 10x6 is recommended for break in.

please correct me if i am wrong, but I think 12x4, 11x5, and 10x6 all put the same load on the engine, right?
Does it matter for breakin if the diameter/pitch is different? Or it is just a matter of load?

I have always liked using an APC 12.25 x 3.75 on my ax's
I will break a engine in with the prop I intend to fly the plane.

I have a tower hobbies 46 which from what I understand is the same as the os 46. Broke the engine in on a 10x6 prop. This weekend switched to an 11x6 prop. Man did I notice a differenc especially on take off. Was in the air at about the 50 to 70 ft mark. It is all a grass runway. I also noticed a difference in the air as it was just a slight bit slow especially with the wind in the tail.

CGRetired
Thanks for the explanation. It makes perfect sense to me now. Went flying this morning and was intending to try 11x7 and 11x8 but didn't get a chance. Spent most of the time just enjoying the plane with the 11x6 and letting my son and cousin fly my trainer with the buddy box. Next time, I am going to try switching props. Thanks again for the info.

DocWill,
The manual that came with the engine (brand new about a month ago) lists the different "suggested proprellers" on page 15. Then on page 16 under the heading of "Before Starting" it lists the 11x6 as a suggested size. The manual does not give a suggested size under "break-in" so I just presumed 11x6 was the correct one. The engine is broke in now. So I can experiment next time. The manual tells you not to make successive "nose-up" flights for three or four flights. I just followed the directions, because I thought that would be best for the engine.

By the way, after that motor was broken in and dialed in, with the 11x6 on a dry lake bed strip, the Pulse XT lifted off after about 50' and then I could swing around it would pull straight up almost out of sight (well, until my neck hurt anyway)! I am having a blast with this plane.

I have the Thunder Tiger 46 Pro on an LT-40 (a BIG draggy trainer). I use an 11-5 prop with very good success. An 11" prop has 20% more disc area than a 10" prop and will produce more power at the same pitch and RPM as a 10" prop will. Ya can't swing a 20% larger prop at the same RPM using the same engine so you usually have to run the larger prop in a lower gear (pitch) than the smaller prop. I can turn 13k RPM on the ground using 15% fuel - definitely not over revving the motor but certainly not lugging it down.

I wanted low end thrust for my trainer so a larger, lower pitched prop works just fine. A more streamlined airplane and I'd probably want a bit more pitch and may go down to a 10" diameter.

Rule #1 - start with what the engine manufacturer recommends then experiment with slight changes in diameter/pitch. Fuel also makes a substantial difference with 10-15% nitro being the norm.

I have an OS 46 FX on a scratch built stick. Swings a 14X4. Best thrust prop I've tried, and I've tried all the sizes aforementioned.

Just an F Y I,
Went flying today. Started out with the 11 x 6 on the Pulse. After a couple flights, switched to an 11 x 7.5. All it did was slow the plane down. Made for some real slow landings. Switched back to the 11 x 6, and will stay there for now, as the plane flys just fine with it. Now I have a few extra different size props. Guess someday I will have to buy a few planes and motors to fit the props. Yea, sure, my wife will believe that one!

Hey MESA.....How do you feel about the 46AX on the Pulse? Is it enough? I have one sitting on another plane which will be transplanted once I assemble my Pulse XT. I was wondering if I should get a Super Tiger .51 for it instead. I dont want to be the fastest....but am looking for aerobatic power.

ro347,
I taught myself how to fly May of 07 with a Nexstar. Bought the Pulse for my second plane, wanting to move to warbirds. Have put about 25-30 flights on the Pulse. I can do a little more that what I guess would be called "basic" aerobatics, but teaching myself is a little scary. Trying to learn how to use the rudder as much as possible. I have tried some manuverers that I shouldn't be trying yet. Fortunately, I was high enough to recover, but sure made my heart skip a beat! Have played around with the high rates on the control throws, which is a blast. The plane changes direction so fast, or seems fast to a novice like me. So, I my not be the best one to ask questions about enough power for aerobatics. But, just to give you an idea, with the OS 46 AX, I can pull straight up for several seconds, and then it stalls and falls over. I have tried to hold it in a "hover" at about 150-200 feet high (not wanting to crash), can keep it there for a few seconds and then it falls over, but I am sure I don't know what I am doing. I would think anything bigger than the 46 would be enough. I was thinking next year, I might put the OS 55 (same mounting as the 46) just for fun and to see what would happen. Hope this helps.

Thanks Mesa!