clandestoy

My Feedback: (112)

Hello,

I am new to the forum and would like to know if anyone could help me. I have an older OS 91-FS engine that has had the first few threads of the muffler (silencer) stripped. The header pipe threads are in perfect condition, all I need to do is to restart the threads to be able to use the muffler.

My question is - does anyone know what thread tap size I need to use to re-tap the threads?

Thank you in advance for any assitance in this matter.

Regards,

Cesar

m-mtoys

I am new to this site put I am getting inf. about a 91FS I have a 50SX

w8ye

My Feedback: (16)

Cesar M11X.75

clandestoy

My Feedback: (112)

W8ye,

Thank you very much for the reply. I tried scouring the OS website for about an hour but could not find any info the muffler thread size.

Thanks again.

rainedave

My Feedback: (1)

As per RCU rules, I didn't want to start a new thread for my question, so I'll ask here. I tached my SF .61 with its Mac's #1062 long stroke quiet pipe yesterday. Using Powermaster 5% nitro and an APC 11x10 I got a steady 11,630. Does this look like a decent figure? This is the non-pumped, side exhaust model.

Thanks,
David

sodbuster 1

Hey is that one of those flying tables I've heard about??

rainedave

My Feedback: (1)

It's my new start-up business... "We bring the Picnic to you!"

David

Bax

My Feedback: (11)

That a good RPM for that engine. That engine runs best when propped to run in the high-11,000's.

rainedave

My Feedback: (1)

Thanks Bax. I also need to try a 12x8, and I'm guessing it will turn about the same, maybe a tad higher.

David

Avaiojet

My guess with the advent of the 1.2 AX, engines like the 91 or the 108 are becomming obsolete?

In other words, why purchase those engines when the 1.2 AX is available AND a better choice?

Anyone agree or disagree with this?

CK

w8ye

My Feedback: (16)

I've been around a 120AX at the flying field since they came out. It is in a UCD 60 and seems like a 60 until you open it up to pull out of a vertical and you hear the zoom of the 17-4 prop. The owner also has a couple Saito 125s with the same prop. The saito has a definite edge for low tork. The OS may have a slight edge on top end if you could let it wind up on the plane.

Ken6PPC

I can think of one very good reason to buy a .91 instead of a 1.20. Weight. The .91 is about 4 oz. lighter, and that extra weight could require weight to be added to the tail to balance the plane. When all is said and done, a plane that is designed for the weight of a 60 size engine is fitted with a 1.20 that then needs extra weight in the tail for balance, the finished plane can be too heavy to fly well. It may also break much easier during one of our (less than) graceful landings!

I don't like adding weight, if I can get around it.

Avaiojet

W8ye

The Saito you speak of, are you referring to a two stroke?

My interest with the OS 1.2 AX would be for a bi-plane. Generally, they need weight in the nose.

I don't believe a couple of onces in any direction, with the weight of an engine, is critical. After all, they are placed in many different models.

I need as much information as I can get on the OS 1.2AX or the older OS 1.08. I have to decide soon.

Charles

w8ye

My Feedback: (16)

All Saito engines that you or I are likely to see are four strokes.


The new series of OS "AX" style engines are very user friendly.

ddewey

Great thread! I picked up 2 OS 60 SR models from an estate sale. Both run great, but one is missing the needle valve from a 7B carb and it's a real pain to switch needles back and forth. Anyone have an idea where I could pick one up? Tried Tower's parts, but no go. Thanks.

Avaiojet

Who makes the largest single cylinder 4 stroke engine?

CK

N1EDM

My Feedback: (2)

Saito makes a 2.20CI version http://www.horizonhobby.com/Products...rodID=SAIE220A .

Does anyone make a 4S larger than this???

Bob

Avaiojet

The OS 2.2 is 61 oz.

The 1.8 is 31 oz.

I believe it would be a trade off. I'll go with the 180.

Cost less to run also.

CK

N1EDM

My Feedback: (2)

Thise numbers seem a bit off. I'm curious about where you got the 61 oz from? I just checked and the HH website says that the 2.20 is 40.5 oz complete, and 37 oz without muffler. This compares a bit more favorably with the 1.80 which is 31 oz without muffler. Still, 6 oz is a fair amount of weight, though it will be going on a large model...

Bob

Hobbsy

My Feedback: (102)

Bob, here are the numbers from Towers site for the OS 2.00.

Weight: 32.8oz (930g) without muffler
34.2oz (970g) with muffler

Avaiojet

I believe I was in error with the 61 ozs. Sorry. But I did see this someplace on line, that's where I got it. Maybe I'll stumble onto it?

The Saito sight has the OS 2.20 at 1096 grams and the OS 1.80 at 880 grams.

I haven't done drugs in a while and sold my scale on ebay, so I have no idea what that is in ounces?

I know little about these engines, so help is appreciated. I will have the engine mounted inverted with a Pitts style muffler.

Saito link:

http://saito-engines.info/specifications.html

And this is my project:

At 80"

N1EDM

My Feedback: (2)

I love that airplane... It looks like an Ag-Cat on steroids!!

It looks like it has a relatively long nose moment. Lighter would be better. If Hobbsy is right (and I'm sure he is), the OS would be the way to go.... if it's not too big for the overall design...

That's my opinion, but I can be made to waffle....

Bob

w8ye

My Feedback: (16)

As Bob says here are the specs on the DPM Ultimate from the site.

Specifications

Wing Span:
60.5 in.
Wing Area:
1,230 sq in.
Length:
64.5 in.
Weight:
9.5 to 10.5 lbs.
Engine:
.90 - 1.20 2 or 4 stroke
Radio:
5 channel

w8ye

My Feedback: (16)

There's a great Planes kit that uses an engine the size of the 56
http://www3.towerhobbies.com/cgi-bin...&I=LXJ581&P=ML

rainedave

My Feedback: (1)

I just added another engine to my OS fleet. This was the last cross-flow scavenged .60 that OS made: the Max-H FGR Blackhead. It was soon followed by the Schneurle ported .61F SR. I've been buying NOS OS parts over the last year or so when I can find them, and this one now has a new sleeve and ring, and new bearings, too. It weighs 17.4ozs with the muffler and some of that is castor oil. For the sake of comparison, my K&B .61 with muffler and Perry carb weighs 18ozs. The AX .55 weighs 18.5ozs with muffler. I guess I'll have to put the same prop on all three, use the same fuel and see who wins.

David