RE: O.S. 95 AX !!!
 

mfuess,

Which one performed the best in your opinion and what type of plane did you fly them on or was it just a bench run?

Coop

RE: O.S. 95 AX !!!
 

Thank you very much !

Let's spend money now....

RE: O.S. 95 AX !!!
 

My favorite of the props tested, is the APC 13x8. It gave me good thrust and excellent throttle-up transition. My 95AX has been in two airplanes so far. It was first put into an R3 Gee Bee, then later moved to an old Great Planes FUN-ONE.

I also installed a Performance Specialties "ULTRA THRUST" on my AX. I plan on testing the props again to see which one's do best with this tuned muffler.

RE: O.S. 95 AX !!!
 

Correct me if I'm wrong....

I've read that the 91 4 Strokes swing a 14x6 Prop at about 10k Rpms....That the magnums are capable of so...

May one get better results in your engines with a bigger prop??

RE: O.S. 95 AX !!!
 

10K RPM on a 91 spinning a 14x6 prop is pretty much correct. I'm taching 10,800 RPM on a 14x6 APC. There is so little difference between a .91 and a .95 that it's more a matter of a good tune than size. There is only .01 horsepower difference between the .91 and .95AX.


*** APC 13x8 Narrow Prop ***
Stock Muffler RPM= 11,250
UltraThrust Muffler RPM= 11,880
Tuned Pipe RPM= 12,030

RE: O.S. 95 AX !!!
 

Yes!....but I mean a 91 4 stroke!

There are also reports from the tower 75 turning 11700 RPM on an APC 13x6, so I don't see much power difference here...

APC 13x6 @ 11700= 1.78 HP (tower 75)
APC 13x6 @ 12400 = 2.09 HP(95AX)
APC 14x6 @ 10800= 1.87HP
APC 14x6 @ 10000 = 1.49HP (magnum 91 4T...from the posts around here)

With the props mentioned, the engine develops about 1.8HP.... how are the numbers of the 91FX?

Seems a little on the down side to me??

RE: O.S. 95 AX !!!
 

NO, my AX engine is turning a 13x6 at 12,400 RPM on the stock muffler.

APC 13x6 @ 12,400 RPM= 2.334 horsepower

__________________________________________________ ___________________

OS 95AX with stock muffler

PROP Size MFG. RPM SPD THR HP
13 x 6 APC 12,400 70.46 13.19 2.33
13 x 8 APC 11,250 85.23 10.85 2.32
14 x 6 APC 10,800 61.37 13.46 2.07
14 x 7 APC 10,320 68.41 12.29 2.11
14 x 7 Graupner 9,630 63.84 12.7 1.75
14 x 8 APC 9,750 73.87 10.97 2.03
15 x 6 APC 9,600 54.55 14.01 1.92
__________________________________________________ ____________________

RE: O.S. 95 AX !!!
 

Yes I know! I was putting some numbers there to compare (I edited the post a couple of times)....

I'm using the prop power calculator from Pé Reivers, I guess you have another one.

I'm just pointing that the 91 AX doesn't look to me especially strong, but I may be wrong, I don't have two stroke engines in the 90-100 range.

RE: O.S. 95 AX !!!
 

You have to fly with a 95AX to appreciate it. From idle to maximum RPM on a 95AX is about double that of other engines.

I'm cranking out 12,030 RPM on an APC 13x8 and it goes from idle to top RPM almost instantly.

RE: O.S. 95 AX !!!
 

I had trouble with my 95AX 4 stoking at 40 and 50% throttle.
When temperatures got down to 40 - 50 degree I started
having dead sticks. I finally found the cure today. The
engine was running cold even at 80 - 85 degrees F.
I wrapped the engine with Reynolds aluminum wrap
about 3/4 of an inch from the top down, but not the top.
I also boosted the nitro from 15 to 25%. This is at 3000 ft.
elevation which reduces power about 9%. I don't think
25% is excessive at 3000 ft. Anyhow the engine ran smooth
at 40 and 50% throttle and the dead sticks went away. The
next task is to figure out how to lower the nitro; probably with
some more heat shielding.
Added on 12/16: Removed the aluminum foil and then lowered
the nitro to 20% and the engine is running fine at 40% throttle.
It also does not 4 stroke at idle but does at one or two clicks up.
It also is running more consistantly at landing. The plug is an
Enya #3.

RE: O.S. 95 AX !!!
 

Have you tried different heat range plugs?

jess

RE: O.S. 95 AX !!!
 

I tried a bunch of glow plugs. I think the Enya #3 was best. But none of them
eliminated 4-stroking at 40% and 50% throttle.

RE: O.S. 95 AX !!!
 

It's quite normal for any model two-stroke engine to be rich in midrange...you won't necessarily eliminate four-stroke mode when in the midrange. That's because fuel flow is not linear throughout the throttle range, and you also need a bit of excess fuel in the mix to allow the engine to accelerate when you open the throttle.

RE: O.S. 95 AX !!!
 

Bax:
I finally got it to stop 4 stroking at 40% and 50%.
Increased nitro to 25% ( 3000 ft elevation ) and wrapped
3/4 inch wide tin foil from top down but not on top.

RE: O.S. 95 AX !!!
 

Griesel: I live in denver at over 5280ft elevation. Will I have trouble with this engine? I normally use 15% nitro fuel. I need an engine for my Big Stik 60. What is it that you're doing with tin foil?

RE: O.S. 95 AX !!!
 

You won't have a bit of trouble with any of the AX series engines. They are the best engines ever made. As Bax mentioned, any 2 stroke can run a bit fat in the midrange at times, especially if the tank is a bit high, using a Macs muffler, etc. This would be a perfect engine for any 90 size application. Sure wish I had one!

Ernie

RE: O.S. 95 AX !!!
 

Provided it does not peel...

RE: O.S. 95 AX !!!
 

I once ran an APC 14-8 on a 91FX and a 108FSR, both with stock mufflers and 10% nitro. The 91 would turn 9500 and the 108 did 10500. Too much prop for the 91s carb size.

RE: O.S. 95 AX !!!
 

I wrap tin foil around the cylinder head to increase the head temperature.
The problem is the engines run too cold and are running rich at mid range.
I saw the same thing with 91FX's, just a little bit better than a 95AX.
If you run your plane most of the time at full throttle I feel these engines
do fine without self destructing if set up properly. 3D stuff.
If you do a lot of part throttle flying like touch and goes and IMAC aerobatics
Not so good.
At 60 to 85 degrees F, at 3000 ft. the engines did OK, not great but OK.
At 40 degrees F, when full throttle and idle were properly set up I was
getting dead sticks every touch and go; actually touch and not go; even
when I ever so gently increased the throttle. The tin foil and 25% nitro
at 3000 ft made the 4 stroking at mid range and dead sticks go away.

Nitro: the maximum OS lists for Nitro percent for 95AX and 91FX is
20%. At 3000 ft the power loss is about 9% and at 5000 ft the power
loss is about 15%. Increasing nitro at higher altitudes replaces oxygen
lost, partially restores power, and the engine runs hotter. In cold
weather and higher altitude you can use more nitro. Just be careful.

Picture: This is a H9 Twist 60 with the cheeks sawed off and the engine
mounted sideways. The prop is a MAS wood scimitar 14X8. I found
noticeable better vertical with the 14X8 versus the same prop in 14X6.
RPM was 9500 max; 9250 operational max. The aluminum foil is held
on with a tie wrap. No temperatures were measured.

I am also going to try an OS FS110a; less power; less weight; may run
better over a wider range. PS I love OS 55AX engines. They are
wonderful on 40 size planes.

RE: O.S. 95 AX !!!
 

Griesel: would you say the 75AX is less hassle and runs better than the 95AX?

RE: O.S. 95 AX !!!
 

I have never had my hands on a 75AX. Sorry.
Small update I changed my propeller this morning to a 14X6 JXF and it ran too hot.
I thought I set up the hi end mixture Ok but after this morning I am not sure.

RE: O.S. 95 AX !!!
 

The O.S. Max .95AX engine cannot peel...the liner is steel, and the piston has a ring.

The only liners that had issues with plating coming off are the old nickel-plated liners. About ten years ago, there was a difficulty with liners in the .45FX non-ringed engine. While very low in percentage of engines sold, the very large number of engines out there made the difficulty seem large (a small fraction of a large number is also a large number). O.S. changed the makeup of the liner, and the difficulty pretty much went away.

Yes, even now, some liners will have difficulties with the plating, but the number affected is well below a few tenths of a percentage point. Now, though, even if only one liner out of all the ones made had a difficulty, there would be a hue and cry that O.S. has a problem.

As it has always been, though, the vast majority of problems we see are not caused by how O.S. made the engines, but by how the engines are used by the modelers. That was the same, no matter what brand of engine we've serviced over the years, which included HP, OPS, Irvine, and others.

RE: O.S. 95 AX !!!
 

Thank you Bax for getting me straight abut the piston / liner nature on the 95 AX (I thought it was yet another ABL piston/liner combo).
I agree that a small percentage of a big number gives a relatively big number also. But to make that assertion, you must have the various market shares of each brand at hand. Would you mind sharing them with us to consolidate your statement ?
Thanks !

RE: O.S. 95 AX !!!
 

Bax, I have 22 OS engines I have bought over the last 30+ years. I currently have a 61 FSR ABC in a Sig Kadet Senior, a .61 SF ABC in a Sig Super Sport which it has been flying for the last 20 years. a 61 SF ABC in a BH T-28 Trojan, 46 AX's in a GP Cherokee, H9 Piper Pawnee, and a Capitol Flyer, a 55 AX in a second GP Cherokee, a 61 FX in a Pulse XT 60, and my newest engine, a 75 AX in a GP RV-4. I have never had a single problem except for bearings with any of the engines in all the years I have been flying them. I use 10% Omega, I tend to run them slightly rich, break them in according to instructions, always run out all of the fuel in the engine at end of a flying session, and use after run oil (Ultra Oil by Performance Specialties) at the end of a session. This past year I flew 2-3 times a week for ten months, had no dead sticks, no crashes [:-], and did not even burn out a single glow plug. You are right when you say problems are caused "by how the engines are used by the modelers." It is mainly those who do not know how to tune an engine, or are trying to get the last ounce of power out of an engine, or do not know how to set up a cowling for proper cooling that have problems. But then I have to say I have had the same experience with a large number of Foxes and Enyas. They take longer to break in and are a little harder to tune than OS engines but they too are great engines.

This past spring I bought a Magnum 46 XLS (OS 46 FX Chinese clone) for $47 including shipping from Hobby People and put it in a GP Escapade. I broke it in as I would an OS and after 50+ flights I can say its performance is great. It is currently my favorite plane/engine combination. As I understand it, quality is hit or miss with China engines' quality control but the engine I bought seems perfect. I would say that OS needs to re-think their pricing strategy as the China engines' quality continues to improve.

Bruce

RE: O.S. 95 AX !!!
 

Thanks for the advice. I just ordered a 95AX for my Big Stik 60. I hope this is the perfect combination.

RE: O.S. 95 AX !!!
 

Hi Griesel, thanks for the updates. Did you mount your 95 sideways to get the carb more inline with the tank center?

Thanks,

Ernie

RE: O.S. 95 AX !!!
 

Griesel,

Will the 95AX hover your Twist 60?

RE: O.S. 95 AX !!!
 

With 14X8 props; 14X6 do not work as well; The thrust to weight ratio is in the vicinity of 2:1. I have not measured it.
Just a guess. More than enough power to hover. This is with 20% nitro which the engine requires to run smoothly at
40% throttle. The Twist 60 weighs 6.5 lbs empty. I do know that it will climb to 800 AGL, going straight up, in about
15 seconds. I am practicing the IMAC Basic 2010 sequence at 1/2 throttle max. This is about 3000 ft. altitude at
temperatures about 55 degrees F.

RE: O.S. 95 AX !!!
 

I maidened the 95ax on Friday. I had the same mid range four stroking problem with the OS#8 glow plug. It was too rich through mid throttle and would eventually stall. When I left the glow ignitor on the plug, the engine ran fine. So I switched it to a OS F 4 stroke plug and it solved all the problems. Now I can idle and transition to any throttle position without sputtering at all. I'm using 15% Omega.

This engine is easily more than needed for the Big Stik 60. Using a 14x6 prop, it was tearing up the sky even at half throttle and a generously rich high speed needle setting. I'll try a 14x8 next.

If you plan to use this engine, I'd recommend a hot, four stroke glow plug and ditch the #8 that comes with the engine.

RE: O.S. 95 AX !!!
 

Try the new OS #7 plug.

It works a treat in my Webra .91 and OS 1.20AX

RE: O.S. 95 AX !!!
 

The #7 OS plug did not do anything to solve the mid range problem on my 95AX. What did work was an Enya #3 plug,
slightly better; and 20% nitro, a lot better.

RE: O.S. 95 AX !!!
 

I have about 6 flights on the OS95AX. I've been using a 14x8 prop. I tached it before the last flight and I couldn't get much more than 9100 RPM maximum. I'm in Denver at 5280 feet using 15% Nitro. Shouldn't I be able to get more than 9k RPM on the ground with this prop and engine combination? Maybe the engine is still breaking in?

RE: O.S. 95 AX !!!
 

OK these engines run cold. On a typical warm early February day with temperatures at 50 degrees F
and 5280 ft altitude they need more nitro to stay warm like 20%. Or you could blast around the sky at full
throttle. All 14X8 props are not alike. At 50 degrees F and 3000 ft. elevation with a 14X8 APC I got 9400
rpm which was 300 rpm down on the rich side. The engine had about 10 flights on it and was not broken in.
This was with 20% nitro. Another 95AX on the same type of plane and the same conditions except the engine
had been overheated and the temper taken out of the ring the rpm was 8700 rpm. This engine was broken in
but with a bad ring. That engine has a new ring now. I have not tached either engine since then. It would be
a good project to run both 95AX's and a 91FX on the same day with a 14X8 APC pattern prop and see what
happens.

RE: O.S. 95 AX !!!
 

I fired up and adjusted all three engines today.
S10 is an Ebay Ultra Easy Stik 60 with a OS FX91. S11 is a H9 Twist 60 with an OS 95AX, and S12 is a H9 Twist 60 with an
OS 95AX Fuel was 20% nitro 18% castor synthetic mix. Altitude is 3000 ft. Temperature was 65.5F, 67.9F, 64.1 for the
three measurements. Glo plugs were OS#8, Enya #3, and Enya #3 for the three engines in the above order. Propellers
were 3 different 14X8 APC pattern type. All readings are 300 rpm below peak rpm. The engines were adjusted richer until
rpm was 300 less than peak.
S12 95AX 9300 rpm
S11 95AX 9450 rpm ( this was the engine that had the ring replaced ) Engine was hotter than the other two so I think it
needs more break in.
S10 91FX 9150 rpm

RE: O.S. 95 AX !!!
 

If you give the prop a backwards flip (clockwise), do you hear a metalic pinging sound at the top of the stroke just as it is hitting the compression?

RE: O.S. 95 AX !!!
 

Hey guys, would you use the OS 75AX or 95AX to do 3D with this? http://aero-works.net/store/detail.aspx?ID=75

RE: O.S. 95 AX !!!
 

The OS 61FX, 75AX, 91FX, and 95AX all weigh about the same.
So from a balance viewpoint it does not matter which engine.
I like 95AX in a 6-1/2 lb plane. They are pricey. The 95AX
costs the most, the 75AX is next pricey. The 91FX is no
longer manufactured by OS but they can be picked up on Ebay
or RCU or about $100-$120 used. Be sure that you get the
newer version of the 91FX with the newer remote mixture
control. The 61FX is my 4th choice among the OS engines.
Another choice is the Super Tigre G90 ring engine for good
power at low cost. I have one of these for my next 60 size
6.5 lb plane whenever I make time to put together one.
The ST weighs a little more but a MACS muffler can be purchased
to get the weight down. This of course makes it not cheap.
Are you confused. I know I was. The 75AX and all the 90+
engines will make that plane go like a rocket. I do not know
if the Aeroworks design will hold up to the bigger engines.
I just looked up Aeroworks planes and their 90 sized planes
are 1/2 lb heavier. The 91FX and the 95AX does shake my
6.5 lb planes a fair amount but I have one with about 130 flites
and so far it is holding up OK. I bet if you call Aeroworks they
will not support a 90 size engine in a 5.5 lb plane.

RE: O.S. 95 AX !!!
 

How many pounds of thrust does the 75AX put out?
I found this on the 95AX http://www.youtube.com/watch?v=k0drw1sGQ3U

RE: O.S. 95 AX !!!
 

I have a Kaos 60 with a 95AX and it pulls it though the sky like a rocket. It weighs in at 6.5 LBS. I think this is a good pulling engine but I have not tried it with a low pitch prop. I think I would make sure my plane was at least 6 LBS. I have had to tighten up all my engine mounts screws and lock nuts a few times till I put lock-tight on them. It’s a screamer. I have used a 13X8, 14X6, 14X7, 14X8 and a 15X6 and the 14X7 is the best RPMs at around 9,400 without too much vibration at full throttle. By far a much better engine than the OS 61 and the Super Tigre G90. I like the G90 but it just doesn’t pull like an OS. It’s a very reliable engine but just not the one for me. If you have the cash OS 95AX is by far the better buy.

RE: O.S. 95 AX !!!
 

Today I bought this 2 stroke engine!
1.What fuel do you recommend that would be best for him?
2.What propeller for speed and force ?
3.what plug would be best for him?

Thanks Amir.