nikon44

O.S. 61 SF what prop? older long stroke motor brand new dad broke it in then never used it

it's going on 6lbs yak

rainedave

My Feedback: (1)

12x8 is good. 11x10, too, for more speed. I've never thought of this engine as a 3D type. It's happiest under 12,000rpms.

David

DarZeelon

Nikon,


I agree with David; this engine has not been used in the past, for anything that even resembles 3D...

The OS.61SF was an F3A Pattern engine, designed to work with a full length tuned-pipe.


However, if you use the 4D carburettor, along with the choke tube in the barrel, to decrease the venturi size, it will probably work, with a normal muffler.

anuthabubba

My Feedback: (102)

nikon44,

My .61 SF turns an APC 13~6 at 11,000 rpm on 10% nitro with the stock muffler.

Terry in LP

nikon44

thanks, i'm just using it for sport and mid aerobatics no 3D, will start with a 12x6, 12x7, might try 13x4, and 13x6, 13x7 will put a tach on them thanks

rainedave

My Feedback: (1)

nikon44, I think the 12x6 and 13x4 are too small. For traditional short stroke, high revving sixties like the FX, Tower, Magnum or Thunder Tiger, etc., those props would be great. Just use a prop that gives you "eleven-something" on the ground and it will be happy.

Mine is turning 11,630rpm with an 11x10 on 5% Powermaster. I might even end up going with an 11x11. That's the Mac's 10cc (.60-.75) long-stroke #1062 Quiet Pipe in the photo which is perfect for the SF.

Good luck!

David

Flyboy Dave

My Feedback: (21)

....yep, the 12-8 is the correct prop.

FBD.

DarZeelon

Nikon,


The 'Hanno' version of this SF engine was claimed by some to be capable of spinning a 12x12 @12K... But despite the pump, pipe and huge bore carburettor, it could only muster up about 10.5K on that prop size.

My friend and RCU member Curt (racecity) uses an MVVS .61; that has the same bore and stroke (23x24 mm), which can spin APC 13x8 and 13x9 props, around 10,700-10,900 RPM... I am not sure if the SF can make this level of torque.

Dave?

Bax

My Feedback: (11)

The O.S. Max .61RF Hanno engine was intended to turn about 9,600 RPM when used with an APC 12 x 12 propeller and the O.S. Hanno Tuned Pipe Assembly. On Omega 10% fuel, it would run very consistently at that RPM level, give or take 100 RPM or so. We've run many of them over the years and would get that RPM level very consistently on the test bench.

NM2K

My Feedback: (14)

But which prop would you use on a 3D capable model? Assuming that is what it is.

These fellers would probably benefit from using a 14x4 into a muffler and no huge carburetor, I would think. What say ye, Bax?

If the model is a true 3D flyer, the last thing the OP wants is a prop that will pull it around at over 70 mph. It would be parts shedding time.


Ed Cregger

DarZeelon

Quote:

ORIGINAL: Ed Cregger

But which prop would you use on a 3D capable model? Assuming that is what it is.

These fellers would probably benefit from using a 14x4 into a muffler and no huge carburetor, I would think. What say ye, Bax?

If the model is a true 3D flyer, the last thing the OP wants is a prop that will pull it around at over 70 mph. It would be parts shedding time.

Part shedding; no doubt, Ed!


It is the APC 14x4W. This prop will be spun about 300 RPM faster than would a 13x8.

An APC 15x4 would be spun a little more slowly that the 13x8.

anuthabubba

My Feedback: (102)

nikon44,

My .61 SF turns an APC 14~5N at 11,200 with 10% fuel and stock muffler.

Terry in LP

Bax

My Feedback: (11)

The O.S. Max .61 SF engine should be propped so that it turns in the mid-to-high 11,000's. We usually ran a 12 x 7 or 12 x 8 APC prop on the test stand with the stock muffler. You should work with it to turn the same RPM. Since the engine was out of production by the time 3D-type of flying became popular, we don't know of a prop size that would be good for that. Ideally, you want a high-revving, low-pitch propeller for 3D, and the .61 SF is not a high-revving engine.

landeck

My Feedback: (1)

I have 3 OS 61 SF ABC engines I bought around 1990. They come with a model 7L carb and a model 744 muffler. The recommended props are 11x10 to 12x11 for pattern flying and 11x8, 12x7, 12.5x6, 11x7 (3 blade) and 12x6 (3 blade) for sport flying.

All three engines are in excellent shape. I use them for sport flying and basic pattern manuvers. One has spent the last 18 years hauling around the same GP Super Sportster 60. This past June I replaced the bearings and it runs as if new. The second one is in the process of being installed on a new BH T28 Trojan. The third is in the box waiting for a plane. All are clean with no baked on crud or discoloring. I externally clean them well and use after-run oil at the end of the day after running out the last bit of fuel. They are great engines and I expect to have them for many more years.

Bruce

planetary

Bruce,

After searching posts for OS.61 props I ran across your reply where you said you had three of these engines, one in a GP Super Sportster. I have one of these OS engines that was bought in '94 but never ran until I ran it in a bench mount this winter. I'm mounting it in a GP Super Sportster I'm finishing as we speak. I ordered some props that were recommended in the manual but have found all of these to be too thick at the hub whith a 2.75" spinner backplate (about 3/16" thick)mounted on the crank shaft. Once I slide on the prop washer there's just enough threads left to get he prop nut started. The props I ordered were Master Air Screw 11X8 GF G3 Nylon, Master Airscrew 12X7 Scimatar Nylon. Both of these props are about the same thickness(1/2") at the hub. Do you know a brand of propeller that isn't as thick at the hub that will allow a spinner backplate to be used? My crank shaftis right at 31/32" long from the drive hub so the props that are 1/2" thick take up too much room.

landeck

My Feedback: (1)

Two of the planes I have using OS .61 SF engines use spinners with aluminum back plates. The prop I am using on both is an APC 12x7 which has a half inch thick hub. There is plenty of space left for the spinner adapter nut. You say your shaft length is almost 1 inch long. with the spinner back plate being 3/16 inch thick and the prop hub being a half inch thich, that leaves you with 5/16 inch for the apapter nut/washer which sounds like it may be enough. What type of spinner are you using? I have a CB Associates spinner on the Super Sportster and a Dave Brown on the Super Skybolt.

I just checked the Skybolt. The shaft length is 1 and 1/8 inches long, an 1/8 inch longer than yours. The spinner back plate is 1/8 inch thick and with the 1/2 inch thick spinner, this leaves 1/2 inch for the spinner adapter.

Bruce

planetary

I'm not where I can see the engine, prop etc. but I believe the spinner is aGreat Planesnylon 2.75". The nose coneis fastened to the backplate by 4 allen head screws. The prop and prop washer are the originals that came with the engine. From your description of an"adapter nut/washer" your spinner must mount differently. My prop nut is probably close to 1/4" thick, the cone shaped prop washer about 1/8". I also noticed that the spinner blade openings were not big enough for the props I mentioned before. To use that spinner with those props I'd have to trim quite a bit to keep from touching. I may end up running the Sportster without a spinner.

airraptor

My Feedback: (66)

Bax is dead on the with the hanno. i had the Mark I version and it would only turn the 12x12 around 9,500-9,700. this is with the header it came with and the red Hanno tuned pipe. they did make a mark II version with a slightly bigger carb.

Just so some of you know the rear exhaust OS 61 long stroke (which was the VF 61 i think) has the same port timing, carb size and even had the same pump as the "hanno" engine.

for the SF if you put a bigger carb on or open the stock one up, widen the exhaust and raise the exhaust with an arc you will see about 500 more on the smaller props with the stock muffler.

NM2K

My Feedback: (14)

Sadly, the OS .61 VF was a screamer and not a long stroke. At least the one that I had and flew quite a bit was.


Ed Cregger

Bax

My Feedback: (11)

The O.S. Max .61 RF was the long-stroke complement to the .61 SF. You ran them the same way. The .61 RF-P was the pumped version, and was run just like the .61 SF-P. Finally, there was the .61 RF-P Hanno, and the later .61 RF-P Hanno II.

The .61 VF was the rear-exhaust version of the .61 FSR. Those were the high-revving engines.

airraptor

My Feedback: (66)

thanks i could remember which one it was. The RF 61P is the one that had the same port timing and carb size as the Hanno mark I that i had. not sure on the Mark II but i think they only used a bigger bore on the carb.

either one was a good engine.

Stoneweapon

I got a used 61SF ABC (actually ABN) with anew piston liner but no carb and exhaust a while ago and tested it with a heli carb and Genesis muffler.
It turned a 15x7 prop without any problem.
5% Nitro, 20% Castor.
7500 rpm
This engine should work well in a 3D application. No problems accelerating this large prop. Not yet tested with a 14x4.


http://youtu.be/RpO5W1Pm1JI