OS .52 Four Stroke

15% Nitro.
20% Oil (18% Syn. 2% Cas.)
OS F-Plug.
8 deg C./46 deg F. 71% Hum.
100' Alt.
11.5 x 6 Bolly Clubman.
OEM Muffler.
10800 RPM

Engine was running quite rich, but here is the kicker.... I made up a Pitts style single exit muffler. Without any needle adjustments I picked up an additional 700 RPM to 11500. Got to like that!

I know a lot of fella's use an APC 12x6. I tried one once, but it tended to load up the engine and found the Bolly to work much better. With the additional RPM gain I feel I can go back to the APC. The engine is now also in an aircraft which is a pound lighter in which the weight may have contributed to the overloading.


Happy Fly'n....

OS .52 Four Stroke.

15% Nitro.
20% Oil (18% Syn. 2% Cas.)
OS F-Plug.
11 deg C./ 52 deg F. 71% Hum.
100' Alt.
12 x 6 APC.
Modified Muffler.
10200 RPM.


Happy Fly'n....

Hi,
Thanks for the info. I have the O.S. 52 for the Giles 3D. I have not ran it as of yet . (it is new). If I may ask a few questions?! What plane do you have it in and what is the weight? Which prop do you like better? Is one better for hover etc.. How did you make the mufff? Is it added back pressure that increased the R.P.M's? Any info is greatly appreciated.

Thank's

Danny

Hey Dan,

The engine is now in a 30 size Yellow Aircraft Sukhoi, weight is 73 oz with 21.4 oz wing loading. I made the muffler out 1" dia. aluminum bar stock and has an internal diameter (I.D.) of 7/8". Length is 2" with a 6-32 pressure fitting. The 90 deg. outlet on the can is .350" O.D. x 17/64" I.D. x 1/2" long to fit a Dubro silicone exhaust deflector.
I made a 90 deg. header pipe out of steel with an I.D. of 19/64" (.298") from the stock 6.5MM (.256"). One end was threaded to match the M10 x .75 thread of the engine head and the other end was 3/8-24 to match the muffler. The weight is less than an ounce more than the original. I would conclude that the larger volume and pipe I.D.'s was the gain to the RPM increase. Sorry, I can't attach a pic.
As for Props, I just ran the APC 12 x 6 on the ground for now. I have yet to fly the plane (hopefully this weekend). The 11.5 x 6 Bolly works very well and have used them in the past. It feels like it has more pull than the APC, but a test fly is in order there. I have also used Zinger 12 x 5's in the past which worked alright.
If you want a prop for hovering, use the largest diameter, smallest pitch possible. I do have 12 x4's (probably not enough), I don't have a 12.25 x 3.75 (probably O.K.) or a 13 x 4 (???) to try.
The problem with swinging to large of a diameter prop on a 4 stroke is that it tends to load up the engine and you get detination.

I'm certain this engine is now turning RPM's very close too, if not more than a .46 2c swinging the same sticks! I'll have to bolt the two on my FX and compare?


Happy Fly'n....

Thanks for the great info! I will try different props to see what works best with this set up. I probably won't go with the "best" prop for hovering as I dont want to get into the other problems associated with that. I have the Y.A. Cap -30 size and have the O.S. 61 FS on it. It flies great! I can even do great waterfalls with it.

Thanks again for the info!


Danny