I was given an OS Max .15, the one that followed the Max .15 MK III.  It is an iron/steel, baffle piston engine.  To further identify the motor, it is the one in this review by Peter Chinn: http://sceptreflight.com/Model%20Engine%20Tests/OS%20Max%2015%20RC.html.

The review doesn't say what percentage of oil OS Max recommended.   I've run it on Sig 10% nitro, 25% all castor.  No doubt this is safe, but  Enya owner's manual recommends 20% all castor for their Mk III .15's. 

Does anyone know for sure what OS recommended for this engine?

Thanks,
Joe Ed Pederson

One more.

Akihiro,

I really appreciate you posting this for me.

    So, basically,  you are good to go with 25% oil.

    Brett

Hello
The OS 15 Mk4 was popular when I was young in the early 80's on our stunt trainers and combat models, ran them on 20% castor oil and 5 nitro back then. Still have 4 of them on my sons models and they run them on 25 oil and 10 nitro now. Did find the original instructions but the scanner would not talk to the computer so shot some pics with my cell phone. Anyway the factory recommended 23 oil once run in (less then the 25% for the earlier OS20 I note). Best prop 7x5 or 8x4 depending on the model.

Regards Gerald

How much juice do you carry , to fly ' the Schedule ' , with one , or four. As the case may be . The Halifax has one or two , each side . 

According to the engine tests , theyll still be happy on 9 x 4s .

Motorman,

What is atf?

Joe Ed

    Automatic Transmission Fluid. Comes in lots of varieties, some even specific to a particular manufacturer, such as Type F intended for Ford products back in the day. All sort of variesties these days such as Dextron, Mercon and such.  The difference is in the types of additives it has such as friction modifiers, lubricants, detergents and such. If your hands ever get really greasy and dirty with sludge and such, wash them with a little ATF first! Then hit the soap and water. For modeling activities, just get the cheapest stuff you can find. ATF has great properties for clinging to surfaces of parts and can take great surface pressure. There are very few bearings in an automatic transmission, and most surfaces are flat with babbitt type bearings or washers, or some kinds of special plastics. It also has additives to help all the clutches and bands grip properly and not slip, kind of counter to lubrication of bearings! It also acts as a hydraulic fluid and the pump in a transmission can generate great pressure, and it's this pressure that makes the transmission change gears at the proper time. I use it in vintage dirt bikes also for gear box lubricant and also for front fork suspension fluid. Pretty versatile stuff.
  Type at you later,
  Dan McEntee

Joe,

You may have a couple of things going on with regard to your launch setting vs. the flight rpm. Yes, the engine may unload some, but it is also likely that your tank setup is changing the feed pressure. Just as a for-instance, if your tank is wide and set outboard because you are using some kind of adjustable base plate you can see the same kind of rpm increase. Ideally, you'd like the tank to laterally center up on the needle valve to minimize these changes. If you use a very wide tank on a small engine (to try to get some tank volume on a short-nosed profile) the farther into the tank you run the leaner it's going to go. Muffler pressure can help reduce this effect, but the two are additive--one does not cancel out the other. Uniflow definitely can help, since it does cancel the effect until you uncover the line.

It is also typical to get an rpm burst on initial takeoff acceleration as the fuel load "tries to catch up with the airplane." That would settle out in the first half lap. But if you are not at a stable rpm due to other setup issues, then the takeoff would be the first influence that might cause the engine to try to find a higher (stable) rpm.

An ideal tank setup is one that has the same ground rpm as the level flight rpm. Tuning the tank is the way to get that.

Dave

Joe,

You may have a couple of things going on with regard to your launch setting vs. the flight rpm. Yes, the engine may unload some, but it is also likely that your tank setup is changing the feed pressure. Just as a for-instance, if your tank is wide and set outboard because you are using some kind of adjustable base plate you can see the same kind of rpm increase. Ideally, you'd like the tank to laterally center up on the needle valve to minimize these changes. If you use a very wide tank on a small engine (to try to get some tank volume on a short-nosed profile) the farther into the tank you run the leaner it's going to go. Muffler pressure can help reduce this effect, but the two are additive--one does not cancel out the other. Uniflow definitely can help, since it does cancel the effect until you uncover the line.

It is also typical to get an rpm burst on initial takeoff acceleration as the fuel load "tries to catch up with the airplane." That would settle out in the first half lap. But if you are not at a stable rpm due to other setup issues, then the takeoff would be the first influence that might cause the engine to try to find a higher (stable) rpm.

An ideal tank setup is one that has the same ground rpm as the level flight rpm. Tuning the tank is the way to get that.

Dave

Dave,

My tank is a 1.5 ounce metal tank. 

It is a Brodak catalog number BH-473, 1" H x 1 3/4" W x 2 1/4" L regular vent (not uniflow) Medium wedge.   It gives about a 5 minute run.  But I have run into the short nose problem.  To get any capacity I end up with a minimum of 1 3/4" wide tank that puts the the pick up tube right at the top of the cylinder.  The tank is mounted on a 3/32" ply base with ears with slots for adjusting the height of the tank. The engine is mounted to 1/8" aluminum bars, which helps a little with the width of the tank.    I did get her running the same speed right side up and inverted by moving the pickup tube about 1/8" above the center of the glow plug.

I would have to make my own metal tank to get at least 1.5 ounce capacity, and a small enough width in the tank to improve the situation.  Especially if I wanted a uniflow tank.  I've never made a metal tank, but maybe it's a skill worth gaining.  I have some experience soldering and I could look up a fairly recent thread on soldering metal fuel tanks.

Thanks for the input.

Joe Ed