Yeah, I just have a fascination with classic 10cc pattern stuff. Even a Tower Hobbies .75 w/pipe would probably leave these older sixties in the dust. But, it lacks the cool factor (in my eyes).

David

seems like it has similar rpm figures for a YS63 on 12x7 and 13x6 props..

not very many unsatisfied customers with these os engines vs what i read about supertiger.[X(]

anuthabubba has generously lent me an #86 carb and P-102 backplate pump to install on my engine for testing. It will be interesting to see how much is gained by them. All I can say is that the #86 throat is massive. I'll run tests this weekend.

David

12x7 apc 15%cool power os #8 plug 11,900 rtf ST header modified to fit OS bolt pattern, im sure ill get a couple hundred more rpm with the right header....on this header meant for a Super Tigre, doesn't quite line up to the exhaust port, restricting it a bit

what numbers can i expect on an ideally setup SF 61 and pipe wih a 12x7 APC? my figures seem very low

Quote:

ORIGINAL: MetallicaJunkie

12x7 APC, 15% Cool Power...

MJ,


Give it fuel with some castor oil...

Lest CruelPower will show you what it's really worth...[:'(]

Also, with the tuned pipe, 15% nitro can be borderline high...

MJ,

"what numbers can i expect on an ideally setup SF 61 and pipe..."

Depends on the pipe design/volume and header length/tuning. As rainedave said the SF .61 is designed to run in the mid 11,000s. Its long stroke and timing require a longer/greater internal volume pipe than a 'normal short' stroke .61 uses. What pipe are you using? It should probably run a 12~10 at nearly what you are getting now. Try adjusting/tuning the header length.

Terry in LP

I will switch to an 11x11 for the pump tests this weekend. If I get in the high 11's I'll be happy. I need to buy some more fuel so if the LHS has a 12x10 I'll pick one up.

MJ, I agree with Terry. Go up in prop size.

David

ill go up in prop size, i have an 11x10 apc to try...The pipe im using is a macs muffled pipe if im not mistaken, its close to 19 inches long... im gonna have to order a macs long header for the OS 61, ............ for those of you that have tuned them.....How much would i need to cut off from a brand new macs header,to be in the optimum range?>



Ill try an 11x10apc during my lunch break tomorrow, its getting too dark to get any good tach readings

I'm using the Mac's 10cc long stroke quiet pipe and my header is cut to 5 3/4"

I'm getting 12,337 with the APC 11x10.

That should make a fair benchmark for your tests.

David

thanks, i tooks my pipe off to make some measurements, and noticed there a was a pretty big chunk of silicone couple that stayed behind from a previous accident, that could explain why my engine tured off on me a few times for no apparent while trying to get some tach numbers


is that how you measured your header ?(see attachment)

Quote:

ORIGINAL: anuthabubba

...Its long stroke and timing require a longer/greater internal volume pipe than a 'normal short' stroke .61 uses. What pipe are you using? It should probably run a 12~10 at nearly what you are getting now. Try adjusting/tuning the header length.

Terry,


The 'long-stroke' is just a buzz word...

These engines all have a stroke of 24 mm and a bore of 23, with 'pre long-stroke' engines having a 24 (or 23.85) mm bore and a 22 mm stroke.
So, they're all virtually 'square'... And 'real world' definitions are 'over-square', for an engine that has a larger bore diameter and 'under-square', for what was termed 'long-stroke'...

And in F3D engines; 'long-stroke' engines have a slightly greater stroke than the norm, but they are still 'over-square'...

What did change for the F3A 'long, when manufacturers went to the slightly under-square design, was the port timing.

Earlier, over-square F3A engines, such as the YS .60, Rossi, Enya XF(#), ST and the OS.61FSR/V, were designed to spin an 11x7 to 11x7¾ props, at 14K and more, with a rather short tuned-pipe (NOT low-volume).

Due to noise constraints, later 'long-stroke' engines (OS.61SF, YS.61, MVVS .61...), through more conservative timing numbers and a longer tuned-pipe (NOT high-volume), targeted the 10-12K range, spinning larger props (up to 13x9), to sound a bit less 'buzzy' to the average ear...


The SF will not like to go to 15K; not because it has a 'long stroke', but because its port timing makes it breath better at 10-12K.

ok with 11x10 i got 11,860, im gonna order a macs header, i have a feeling the misaligned st header is robbing me

Dar,

I understand the 'buzz word' thing. I was trying to use language that is common in explaining the situation. When you lengthen a cylinder, you increase its volume.

Terry in LP

Terry,


No argument here, but most tuned-pipes intended for lower RPM are longer and rather slender; not bulbous like shorter pipes, so despite the added length, I believe their volume may even be smaller than that of high-RPM pipes.

In any case, the amount of exhaust gas per-cycle is dependent on engine displacement (and the magnitude of supercharging), so it is neither greater, nor smaller, for the 'long-stroke' engines.

Dar,

Comparing the Hatori line of reflector disc pipes (generally considered the standard by which others are judged and manufacturers choose as OEM) we notice that the diameters are the same (40mm) from the 10cc 'short stroke' model 601 to the 10cc 'long stroke' model 650 and even on to the 'super long' model 700 and the even longer (9500 RPM) Hanno pipe. The only major difference is the location of the first reflector disc after the diverging cone inside the hollow pipe. There is also a silencing/muffler section after the disc to help reduce the noise.

Terry in LP

OK, Terry.


But this engine really does not need the additional volume for operation.

The manufacturers just use the same tubing diameter, so they will not need extra sets of tooling...

i got new macs header in today, and to be on the safe side i cut the header to 6 inches, measurement taken based on the method Macspro.com uses and got 12300 peak, and backed down to about 12100 or so. Next i need a new set of bearing, it sounds very rough, almost like a coffee grinder. This was one of the engines i brought back to life after many years in storage.

hi  OS   61 SF-max pipe cut down 1/2 inch ( to remove the baffel )- on a 12-6 APCexhaust port on muffler ground out -always to match engine exhaust port-12,600 rpm-on my 60 size super kahos-amazing performance-15% morgan omega fuel-  this engines is a power house

Quote:

ORIGINAL: tony0707

Hi, OS.61SF - Macs pipe cut down 1/2 inch (to remove the baffle) - on a 12-6 APC exhaust port on muffler ground out - always to match engine exhaust port - 12,600 RPM-on my 60 size Super Kaos - amazing performance - 15% Morgan Omega fuel - this engines is a powerhouse.

Tony,


That is a relatively lackluster 1.58 HP...

My MVVS .49, on the mini-pipe, showed 1.67 HP, on an 11.5x6 Bolly Clubman; spinning it at 13,600 RPM, on just 5% nitro...

hi darzeelon
i am sure if i went to a smaller prop ( 11/5 )and was turning 13,600 with my 61 sf my horse power will exceed your numbers-i have no need to run 1,000 rpms more -as the speed and power of this engine in this plane is a true hand full-the kahosairframe is an extremlly efficient airframe -horse power number are not the do all -end all in an airplane set up- the best possible vertical-is my criteria for performance-and everyengine needs to bepropped differently -fora given airframe

Quote:

ORIGINAL: tony0707

I am sure if I went to a smaller prop (11/5)and was turning 13,600 with my .61SF, my horsepower will exceed your numbers - I have no need to run 1,000 RPM more - as the speed and power of this engine in this plane is a true handful. The Kaos airframe is an extremely efficient airframe. Horsepower number are not the do all - end all in an airplane set up.
The best possible vertical is my criterion for performance; and every engine needs to be propped differently, for a given airframe.

Hi, Tony.


In fact, horsepower IS everything...
Not rated, claimed, or advertised HP; but actual calculated HP.

HP, as it is calculated by the [link=http://mvvs.nl/prop-power-calculator.xls]PropPower[/link] calculator, will determine the thrust that your engine is capable of putting out, at every flight speed.

Read your high-school physics textbook again please...


With things as they are now; had you removed your piped OS.61SF with the 12x6 APC and instead installed and rebalanced the mini-piped MVVS .49 with the Bolly 11.5x6 (not 11x5...) prop, your Kaos would have flown better and faster, climbed better and accelerated faster too.


Your mistake is the setup!
The SF is OS' first long-stroke series engine and in the interest of preserving flying sites; it was designed to be at its best, at lower RPM - 10,500-11,000, with a longer tuned-pipe (to make its noise less buzzy to sensitive ears).
In this guise it would produce about 1.8-1.85 HP actual HP, spinning a 12x10, or a 13x8 in this RPM range...

'Letting it go' as you did, with the 12x6, just puts it on the over-run... More RPM - but significantly less HP; which necessarily means less performance.


I believe you 'ain't seen nothing yet', of what your Kaos is capable of...

I don't think the SF can produce 1.8hp at 11,000rpm.

I just finished bench running mine with a Mac's 1062 10cc long stroke quiet pipe. I'm doing the final adjustments before installing the engine in a plane.

Here's what I got with the header cut to 5 3/4"

79° and very humid
Powermaster GMA 5/22
new OS #8
APC 12x8
11,741
1.67hp
9.52lbs. static thrust

My engine would have to turn this prop at 12,000 to make 1.8hp. I guess it's possible with more nitro a bit more trimming of the header. But, right now the needle valve has a broad adjustment range and acceleration is very linear for a pipe (no sudden leap in rpm). In other words, I'm happy with were it is right now. It's operating the way I want it to.

Maybe I'll buy a 12x10 and see what it does. I'd be very surprised if it could hit 11,000. BTW, my pipe is adding about 1,100 rpm over the stock muffler.

David

Dave,


The OS.61SF, like the other long-strokes of its generation, is even more bottom-biassed that that.

If you prop that engine to spin between 10,500 and 11,000 RPM ground static; and adjust the pipe to an appropriately longer dimension, the engine would produce that target HP.


11,741 RPM is still a bit over the hill, although it is less so than Tony saw with the 12x6 prop.

I'll give a 12x10 a try. I don't think my LHS has them in stock since no one uses them these days. I can add 1/2" back to the header for 6 1/4" length. But, hitting 11,000 just seems like a tall order.

David