Luxuswaffe

10x6 APC 13,600
10x9 MA 12,300
11x7 APC 10,400

Sealevel (Florida)
90 degree F
60% humidity
15% Nitro/18% Oils PM
Macs Muffler, not tuned

BillS

ST .45 Italian made with torpedo muffler and exhaust deflector

10 x 7 APC
12,800
2900/3000 idle - If left idling it would drop to 2200 rpm without dropping dead.
4# 15 oz to 5# 2 oz thrust

10 x 7 MA Simitar
13,800
2900/3000 idle
5# 6 oz to 5# 9 oz thrust

10 x 7 MA old style
12,300
3200/3400 idle - seemed to need a higher idle than other props
5# 7 oz to 5# 8 oz thrust

The results were surprising and unexpected. Usually I expect APC to outperform old style MA. However in the 10 x7 size it appears that MA has a strong advantage. Similar data for an OS .46 shows the same trend, lower rpm but more thrust.

Bill

P-40 DRIVER

It will in the air. The MA turn up higher due to decreased pitch caused by flexing and design etc.

blw

My Feedback: (3)

The rpms taken on the ground are misleading. This is only applicable for conditions on the ground, and not when flying. Any means of measuring performance for props for flying conditions must include the models airspeed into things. This means that static measurements are only half of the numbers needed. If the MA is flexing (or coning) then efficiency will drop as larger diameters increase prop efficiencies.

If one has to look for tradeoffs in prop efficiency, increased diameter is more effective than prop rpm.

Zimodile

APC 12x4
500ft above sea level
5 degrees C

10% nitro, 18% synth oil

13,500rpm

Z

Lille-bror

China-model, stock muffler, Rossi 4 plug, 0% nitro, 3% castor, 15% Aerosynth2 (this mix gave the best performance, when I wanted no nitro and 3% cator). Cylinder modified (+180 rpm). Sparybar turned 90 degree to avoid rich middle range. Very good throttle response with all props.
Weather: 16 degree Celsius, showers, sea level.

11/5 APC:
Idle 2700 rpm.
Top 10680 rpm.

- Best HP of the testes props. Tried higher compression (tested by Downunder) but stopped it, due to leak in the manifold.

!0/8 APC:
Idle 3400 rpm.
Top 10300 rpm.

- 32% less HP than the 11/5.

9/8 APC:
Idle 3300 rpm.
Top 12400 rpm.

- 19% less HP than the 11/5.


The 10/8 is too big. Will try a 10/7 APC, also 12/4 and 9/7.
Look forward to test a tuned pipe, some time in the future.

Do you have the muffler as close to the engine as possible or the opposite?

Lille-bror

Downunder has modified several of his engines, to obtain more power when using 0% nitro. This has been done, by raising the compression.

I’m also not using nitro, and tried it myself:
Out of the box, the Super Tigre GS 45 has a clearance of 0,6 mm from the piston to the head – simply measured with a piece of solder, and the engine turned one time over the top dead centre. In the top of the cylinder, there is a cab of 0.25 mm from the inside to the outside. My theory is that some of the effect from the explosion therefore is going outside instead of downside and pressing down the piston. A friend of my took the “outside” ring of, and there bye lowered the cab with .25 mm. Now the total cab is 0.35 mm.

Tested on bench using 9/8 APC prop, Rossi 4 plug, 0% nitro, 3% castor, 15% Aerosynth2, stock muffler.

Before modification:
Max RPM: 12400
HP (Only on my test stand): 1,27

After modification:
Max RPM: 13200
HP (Only on my test stand): 1,67

Now, that’s something!!! An increase of 800 RPM and a HP-increase of 24%!!!

If I can get some 0,05 mm shims, I’ll try to make a more accurate modification.

When using the stock muffler I could measure a little decrease in torque, if the muffler was pushed as closed towards the engine as possible, than the opposite.