canardlover

A friend of mine has got a Rossi 1.05 tractor DF engine in good shape. The engine has been bench tested with the DF unit and runs OK. He is seeking advice on how that engine would perform with a propeller - say 11x8 or 12x8 - for use in a fast plane (similar to a Patriot but a bit larger)
Anyone out there who has experience of a similar undertaking..?...any input is much appreciated.......Thank you in advance and Cheers/Harald

der_steuermann

My Feedback: (2)

Hi Harald,

that'll be a nice project! I use the OS .91 DF engine in combination with custom made carbon fiber speed props ranging from 9.75 to 10.75" in diameter and 10 to 11.5" of pitch - depending on the airframe and target speed.

In the past I switched to CF because it is the only safe prop material recommendable for 13cc to 18cc ducted fan engines spinning in the 20 to 25K regime. Once I saw a blade of an APC 10*10 going at max rpm on a test stand - never again, simply too dangerous!

canardlover

Good point about the limits on APC props, they are heavy indeed. Have you ever considered using a wooden prop...?? And what about venturi size? we speculated about an insert into the Rossi carb to improve throttling and lower the full speed rpm a bit for propeller use....Cheers/Harald

der_steuermann

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I would not try to limit the output by any venturi size restrictions. We are happy about every rpm we can squeeze out of our engines for speed application. The 18 cc Rossi will not turn faster than the OS .91. It features improved torque good for heavier ducted fan jets. You will be happy to get an 10*10 prop near to 20K static. I would suggest to use the MACS pipe # 1190 starting with 14" between glow plug and middle of the fat pipe part.

As for wood, yes wooden props are light and also have good tensional strength. But wood is not comparable to the material properties of carbon fiber. Why not choose the safest way right from the beginning? Another drawback is the lack of suitable wooden speed props for your purpose to attain as much speed as possible.

Improve throttling for a speed plane? - Just fix that 'unimportant' throttle arm of the R/C carb at WOT and let it go [sm=tongue.gif] - or make a 13 mm ring venturi carb for ultimate performance [>:]

WMB

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der steuermann, Would you elaborate a bit on your venturi? does it use a spray bar? I assume it replaces the carb? It must be applicable to any engine?
Thanks, Mike

der_steuermann

My Feedback: (2)

Hi Mike,

the ring design is the most sophisticated one when talking about venturi speed carbs. It is mainly recommendable for ‘ultra’ high performance engines, especially for the FAI racing engines (F2A C/L speed exceeding 40.000 and F3D pylon exceeding 30.000 rpms). For the average powerful sport engine turning below 20K there’s almost no benefit.

The ring – filled by fuel – surrounds the narrowest part of the carb throat where the sucked in air experiences the highest acceleration. Right behind that narrowest position the carb diffusor part begins and the throat opens again. This is the best location for 5 to 10 small borings injecting a fine ‘ring’ of atomized fuel right into the center of the carb throat – generating a very homogenous fuel/air mixture. The fuel supply and rpm respectively is controlled by a regular free-flight needle valve assembly.

Dave03B

Wot carb have u put on my OPS 65?

der_steuermann

My Feedback: (2)

Dave, it is the original 'stock' OPS .65 slide carb used for the ducted fan engines providing instant throttle response. If you want a speed venturi carb to fly your F-16 always at max rpm, just let me know

Dave03B

rightoh, means i'll need a micro servo in line with the carb, in the back of the model i suppose? never had one of these slide carbs b4.

der_steuermann

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Yep, or utilize a 'small' 90 degrees redirection like the ones necessary when mounting one central aileron servo...

canardlover

Vielen dank der_steuermann and I´m "sorry" for the remark about venturi size although it apparently vitalised the thread. The reason was twofold: 1) to be able to tame the Rossi beast at all and 2)we fly from a rather confined grass field so an elevated idle will make it even worse to land a fast ship.
Nice carb you have there, we will certainly consider it but not until we can fly the ship in a controlled manner............Cheers/Harald

Flyer95

My Feedback: (1)

Hi Harald & der Steuermann,
I am the friend of Harald in Sweden, and the owner of the rossi fan engine. I have done some very fast initial tests with the engine mounted on the airplane before I get airborne the next time. I use a quiet pipe from Weston UK (60/90 size) to minimize the noise. Our flying field is kind of noise sensitive. Here are some data & results.
APC 11x8
Tuned pipe lenght about 400mm(16")
5% nitro, 24%oil 50/50(castor/syntetic)
McCoy 55(hot plug)
15600rpm
Most say the engine responds good with good idle, little bit rich on the midrange but that doesnt bother me on this type of airplane.
I know the rpm results are not so very good but the next time I try a cooler plug with a bigger proppellor which should give me more thrust? Or what do you think? Thanks for any responds or suggestions // Amir

der_steuermann

My Feedback: (2)

Hi Amir,

at 15800 rpms your engine does not 'jump on the pipe'.

I believe the tuned pipe length has to be re-adjusted. For that we need to know the internal design of your Weston UK pipe. Is it a double cone pipe (type A) or a pipe featuring a deflector plate (type B)? I would be interested in the actual distance between

the glow plug and the biggest part of the cone
or
the glow plug and the defector plate respectively (as shown in the drawing).

Maybe you could post a pic of your plane/engine/pipe set-up? I have the strong feeling the volume of your pipe is much too small for the 18 cc engine in order to get in resonance. Also, if the inner diameters of pipe inlet and outlet are too small the engine cannot 'breathe'.

To gain most speed for your plane the prop diameter has to be reduced while increasing the pitch. Just try a 10*10 prop (APC only up to 18K static), otherwise carbon fiber. Use a MCCOY MC-9 plug – it is heavy duty. With the above mentioned nitro and oil content you are definitely on the safe side.

Flyer95

My Feedback: (1)

Hi der Steuermann,
Det type is double cone Type A (exactly like your drawing). The distance between the glowplug and the biggest part of the pipe is 400mm(16"). The outer diameter(OD) of the inlet is 21,5mm, thickest part (OD) id 45mm, and the OD of outlet is 12,5mm. The pipe wall is thin, less than a millimeter. I have McCoy 9 and APC 10x10 so I will give it a try next time. Thanks for any suggestions /Amir

Flyer95

My Feedback: (1)

Tryed the Mccoy 9 and could squeeze out 200rpm more, not a big difference. Now I have changed the pipe to a, high volume, JMP-pipe specially made for the OS91-VRDF. I try this next time and if I still dont get better results then I start cuting the header. Also reduced the oil content to 20% for the next time.

Regards Amir Riahi

Flyer95

My Feedback: (1)

Here is some pictures of my airplane and the rossi 105.
This plane is buld up of balsa, abechi, plywood, hardwood and foam. The rossi is pulling this big (80") airplane pretty good with a APC 10x10 or 12x8 about 120mph.

Rudeboy

Flyer,

So what rpm's are you getting now on that engine and pipe? If you're still only getting 16000 rpm you need to work on your props... and from the photo's, I think your pipe is set rather short for 16000 rpm.

Also, if your plane reaches about the same speed on a 12x8 and a 10x10, maybe you should try an 11" diameter prop... perhaps an 11x8 or an 11x9...

bob27s

My Feedback: (19)

I don't know about anyone else......... but approaching 16K rpm with a 11x8 prop is pretty darn good performance I have no doubt with a little bit of pipe tweeking you can get it over 16K with that prop.

Best I've seen done with a Jett FIRE 90L (using a high timed ducted fan sleeve) with a Mac's quiet pipe was 16,400 rpm with an 11x7 (peak ground rpm). This on 15% sport fuel. Same combionation has shown to turn a 10x10 about the same rpm. Weather was particularly good that day.

Flyer95

My Feedback: (1)

Rudeboy,
The pipe in the pictures is not the same as mentioned before.
I have done some new tests ( maybe a month ago) with the pipe shown in the picture and I got 16800 rpm on a APC 11x8 but I got afraid of reaching the proplimit and put on the APC 10x10 for about 17000rpm. On a 12x8 I get only 14800rpm. Forgot to mention that plane goes faster on a APC 10x10 compared to a 12x8.

Bob27
Glad to hear from you the results are good. This engine is a real monster and I think it likes high volume pipes that probably are made for bigger engines. I used to use this pipe on a super tiger S3000(30cc) and it worked good for that engine to.