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Oct 07, 2016, 10:27 AM
Its not IF... Its WHEN.
The.Timinator's Avatar
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Discussion

Anyone know anything about OS 61s?


Hi Guys

Looking to return to flying these beauties so been trawling through my garage.

I have an old OS 61 SF, with the matching blue OS pipe, but I damaged the manifold and the carb is missing.

The manifold is a non-issue but I can't seem to find a replacement carb.

I have also been given - over the years, an OS61P in bits - seems to have a main bearing issue but carb and pump look perfect.

Also have an OS61 RF, ex helicopter and seized, but again, carb looks OK, and an OS61 SX in a similar condition.

My question is - can I simply fit the pump and the carb from the SFP to my SF, or, failing that, would the RF or SX carbs work on my SF?

Cheers im anticipation

Tim
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Oct 07, 2016, 11:07 AM
DavidsPlanes
doxilia's Avatar
Tim,

The short answer is yes.

The only difference between an SF and an SF-P is the different (pump) carb and backplate pump unit. Note that the pump is designed to be used with a "return feed" from the carb so using the pump with another carb will likely not work (though I have never tried it). If memory serves the SF-P and RF-P pumped engines use the 102 pump and #86 carb. There is a simpler pump/carb combination that doesn't require a return feed (two line pump instead of four) used on the RF-P Hanno but no need to discuss that.

If you want to use the engine unpumped then many OS carbs will fit and work on the engine however note that they have a smaller bore carb to provide enough suction to draw fuel into the engine. The large bore #86 carb is only possible because the engine is fed by the pump. Note that as a result the pumped version of the engine(s) is a little more powerful than the unpumped.

One other minor comment is that these engines came in "ABC" as well as "ring" versions not that this affects whether you use a pump or not. In principle it should be doable to use the pump/carb combo on other OS engines with the same carb inlet and backplate size/mount pattern so, for example, you could use these on an older 61 VF (RE) or FSR (SE) - the short stroke predecessors to the RF/SF long strokes.

A suitable prop is an APC 12x10 on the SF/RF.

David

PS never heard of a 61 SX although I do know the 32 SX and 50 SX. They were predecessors to the FX line which was then followed by the current AX line.

PS2 DO NOT disassemble the pump unit or tamper with the factory setting. It should be lock tite fixed by OS.
Oct 07, 2016, 11:09 AM
Registered User
Jet_Flyer's Avatar
Quote:
Originally Posted by The.Timinator View Post

My question is - can I simply fit the pump and the carb from the SFP to my SF, or, failing that, would the RF or SX carbs work on my SF?

Cheers im anticipation

Tim
Yes, you should be able to switch the back plate and pump from the P to the standard SF and use the P carb. I prefer the pumped engines.

Mike
Oct 07, 2016, 11:11 AM
Registered User
Jet_Flyer's Avatar
Posting at the same time! doxilia gave a better answer.

Mike
Oct 07, 2016, 12:06 PM
Its not IF... Its WHEN.
The.Timinator's Avatar
Thread OP
Thanks a lot guys, that's pretty much what I thought.

Just one other question, re the return to the tank.

So far as I can see, there is an inlet and an outlet on the backplate, and a single nipple into the carb.

There also seems to be another fitting in the box - maybe an NRV?
I gues what I am looking for is a plumbing diagram.....
Oct 07, 2016, 12:25 PM
Registered User
Jet_Flyer's Avatar
Quote:
Originally Posted by The.Timinator View Post
Thanks a lot guys, that's pretty much what I thought.

Just one other question, re the return to the tank.

So far as I can see, there is an inlet and an outlet on the backplate, and a single nipple into the carb.

There also seems to be another fitting in the box - maybe an NRV?
I gues what I am looking for is a plumbing diagram.....
If there is not a return on the carb it sounds like a Hano pump system.

Mike
Oct 07, 2016, 12:40 PM
DavidsPlanes
doxilia's Avatar
Quote:
Originally Posted by The.Timinator View Post
I have an old OS 61 SF, with the matching blue OS pipe, but I damaged the manifold and the carb is missing.
Maybe the Hanno does need to be discussed after all... The blue pipe is probably a Hatori anodized version of the Hanno red pipe. I think for a while, they made a pipe like this.

If you post some snaps of the engine, pump and carbs in question, we'll probably be of more help. I suspect the blue pipe was actually meant to go with the engine below which may well be a Hanno.

Quote:
I have also been given - over the years, an OS61P in bits - seems to have a main bearing issue but carb and pump look perfect.

Tim
Pictures of this engine, pump and carb as well please. I don't think the blue pipe is a "matching" pipe for the SF. Not that it wouldn't work but it might not be optimal. Hanno's had more lugging power at 9.5K rpm and turned larger props than the standard RF/SF, hence the longer blue/red pipe needed.

David
Oct 07, 2016, 02:31 PM
Its not IF... Its WHEN.
The.Timinator's Avatar
Thread OP
Quote:
Originally Posted by doxilia View Post
Maybe the Hanno does need to be discussed after all... The blue pipe is probably a Hatori anodized version of the Hanno red pipe. I think for a while, they made a pipe like this.

If you post some snaps of the engine, pump and carbs in question, we'll probably be of more help. I suspect the blue pipe was actually meant to go with the engine below which may well be a Hanno.


Pictures of this engine, pump and carb as well please. I don't think the blue pipe is a "matching" pipe for the SF. Not that it wouldn't work but it might not be optimal. Hanno's had more lugging power at 9.5K rpm and turned larger props than the standard RF/SF, hence the longer blue/red pipe needed.

David
Never had much success posting pics but I'll give it a serious go tomorrow.

I doubt its a Hanno pipe - I still have the box it came in, clearly marked OS...

Oh, and this engine predates the Hanno specials by a couple of years or so, IIRC.

I had it in a Panic, seriously crashed due to battery failure....
Oct 07, 2016, 05:21 PM
DavidsPlanes
doxilia's Avatar
Quote:
Originally Posted by The.Timinator View Post
Never had much success posting pics but I'll give it a serious go tomorrow.
Pics on RCG is a piece of cake. Just drag and drop into the "uploads" box below the text window.

Quote:
I doubt its a Hanno pipe - I still have the box it came in, clearly marked OS...
Tim, marked OS what? The Hanno is simply a special version of the OS RF-P. It's a RE engine only.

Quote:
Oh, and this engine predates the Hanno specials by a couple of years or so, IIRC.
The engines perhaps but the pipe? Maybe not. But yes, it could be a pipe made for the SF/RF like you mention. If it's blue anodized and sold by OS, it's made by Hatori just like the Hanno pipe.

David
Oct 08, 2016, 07:44 AM
Its not IF... Its WHEN.
The.Timinator's Avatar
Thread OP
Hi Guys.

Attempts with pics then...

First, the pipe.

Then my 61 SF, minus carb and muffler
Oct 08, 2016, 07:47 AM
Its not IF... Its WHEN.
The.Timinator's Avatar
Thread OP
And now, the relevant bits of the broken 61 SFP I was given
Oct 08, 2016, 07:50 AM
Its not IF... Its WHEN.
The.Timinator's Avatar
Thread OP
And finally, the two seized helicopter 61 FE and SX61 engines, which both have intact, if rather bulky carbs on them. Particularly note the twin needles on the SX
Oct 08, 2016, 09:57 AM
KC4JAJ
Jim Johns's Avatar
The carb on the FE appears to be a 7L, which was the stock carb on the non-pumped 61SFs. Either that one or the pump & carb should just drop into your SF. I'd probably go with the 7L for simplicity.

Jim
Oct 08, 2016, 10:18 AM
Registered User
Jet_Flyer's Avatar
Quote:
Originally Posted by The.Timinator View Post
And now, the relevant bits of the broken 61 SFP I was given
For sure that is a 102 pump, but it does not look like a #86 carb. The carb in the picture looks machined and the #86 is cast. Are there two connections on the carb for the pump supply line and return?

Mike
Oct 08, 2016, 11:12 AM
Registered User
aviationf4u's Avatar
I believe the early 86 carbs were machined. That is the first one I have seen though. Pretty rare carb if it is indeed an 86.
Last edited by aviationf4u; Oct 08, 2016 at 11:22 AM.


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