OS Max 35 FP Stunt Capability?

Gee Whiz, I got so excited about finding the Magnum (post 261121) I forgot about my original question. This is an OS 35 FP, which I have not run, but bought used a few years ago.

. . . . . . . DESCRIPTION . . . . . . .
Bypass side of case:
OS
M
A
X
FP

Exhaust side of case:
35 (in a circle)

Backplate:
3107

2

Underside right mounting lug:
G T

Two aluminum venturi inserts, roughly 5/32 and 1/4 “eyeballed” venturi ID (mike not unpacked yet), with spray bar through venturi

Muffler is stock OS 762 with tap
. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .

I sometimes ran OS 35s back in the early 60s in combat. Crankcase pressure, 9/8 cut to 8/8, maybe 15% nitro, about 90 + or - mph (don’t remember) on Voodoo style planes. So, I am somewhat familiar with its older brothers.

With this engine, and even with the smaller venturi, I assume a stunt style run isn’t too likely. How would you set this up? Just use it as a fast sport engine on something like 450 in^2 profile? Or would it work on a larger plane, and if so, just use a lower pitch prop at a rich two cycle? Or???? In short, what are the limitations on the applications for this engine as is?

Larry Fulwider

>With this engine, and even with the smaller venturi, I assume
>a stunt style run isn’t too likely. How would you set this up?
>Just use it as a fast sport engine on something like 450 in^2
>profile? Or would it work on a larger plane, and if so, just
>use a lower pitch prop at a rich two cycle? Or???? In short,
>what are the limitations on the applications for this engine
>as is?

Mine ran pretty well straight out of the box. It flew my ~48 oz full-fuse Imitation about as well as the average ST46. It did an OK 4-2 break, too, with something like an 11-5 Rev-Up, as I recall. I had it on a Banshee, as well, with a 10-6 Taipan, and it also ran well that way. I would guess it has far more chance or working well, stock, than a 40FP.

Brett

>
> Mine ran pretty well straight out of the box. It flew my
>~48 oz full-fuse Imitation about as well as the average ST46.
>It did an OK 4-2 break, too, with something like an 11-5
>Rev-Up, as I recall. I had it on a Banshee, as well, with a
>10-6 Taipan, and it also ran well that way. I would guess it
>has far more chance or working well, stock, than a 40FP.
>
> Brett

I think I made a mistake when checking the archives before I posted -- I was getting all the glorious posts praising the 25 and very little on the 35. I think maybe I mis-typed 25 instead of 35 in the archive search?

Yes, the consensus, (with no typos in the query) seemed to generally agree with your experience.

Thanks!

Larry Fulwider

They run pretty well with the boost port blocked. I ran a 12x5 modified RevUp and an 11 1/4"x 5 wood three blade on mine and it had plenty of power.

My stock 35FP-S runs nice, and has done so right out of the box. I run it at 5000 feet above sea level, stock venturi and NVA, uniflow tank, 10x6 prop, Powermaster GMA 10/22 fuel, on a 48" 40 size profile ship. It does a nice 4-2-4 break, and gives me consistent runs all year round. My experience with the stock 40FP has not been so positive...

Pete

Click on the STUKA STUNT WORKS at the top of the page. Go to Stuka Stunt Engines and read how Leonard describes the engine.

Phantom --

>Click on the STUKA STUNT WORKS at the top of the page. Go to
>Stuka Stunt Engines and read how Leonard describes the
>engine.

Actually I have one of Leonard's reworked 35 FPs. It runs great!

"So," a reasonable person might ask, "If you got one, and it runs great, why the heck are you bothering us?" Well, I wrote all that out when I started the post, and when I got done, it was so convoluted, EVEN I WASN'T SURE what the question was! And, it was L-O-O-O N G!

Here is the deal. First, I wasn't sure of the age of my engine, vs. the one from Leonard. I don't know what timing or other changes OS has made over the years, hence the long description. I thought that might trigger something in someone's memory, like, "All the ones before . . . were unsuitable, and . . .you got one."

Second, I wanted to leave it stock if possible, and without a comparison, I have no idea how much is due to the rework, that is, how much of an improvement the rework made. Leonard claims it makes a LOT of difference, and he is an honest man, I'm sure. If it takes the rework to get steady runs, I'd likely get a rework. If it just higher performance, I probably don't need a rework for this one.

Third, the picture in my mind of the older OS 35s is that they are basically combat engines, so the rework is a near necessity for our application, not a nicety. The answers above seem to agree that that is strictly prejudice on my part, not fact. Which is what I wanted to know!

See, I told you it got messy trying to explain it all!

Larry Fulwider

HI Larry,

I got confused with the last part about the "OS 35s" being mostly combat engines. If you mean the ones that have "III" (or earlier versions) on the case with separate "jugs" as the sleeve, then you are right, they were honkers.

But, the OS 35"S" (has "MAX-S" on the bypass) then those were the top "out of the box" 4-2-4 engines in many people's eyes in the early '70s.

I still use the "MAX-S" in my Classic planes at times, great stunt engines.

The 35FP does seem to be more controllable out of the box than the 40FP.

Big Bear <><
Character: It's what you do when no one else is watching.

Thanks, Bill --

>I got confused with the last part about the "OS 35s"
>being mostly combat engines. If you mean the ones that have
>"III" (or earlier versions) on the case with
>separate "jugs" as the sleeve, then you are right,
>they were honkers.

Thanks, you filled my knowledge gap. I didn't know how to ID the "honkers", or if they were all still "honkers" without a rework. My combat engines must have been the "III" style. As I said, that is still in my mind, and I didn't want end up with a 90 MPH Ringmaster! My fear was that the redesign, if any, took place after the engine I have was built.

>But, the OS 35"S" (has "MAX-S" on the
>bypass) then those were the top "out of the box"
>4-2-4 engines in many people's eyes in the early '70s.

Yeah, I was racing bicycles in the 70s (Hey, don't laugh, fourth in the State in 1974! Uhh, fourth in my age class, that is), and missed probably 30 years or more of design changes in engines, airplanes, and the whole model world.

I never heard of the "MAX-S" until just now. It was after my era, and before my current efforts.

>The 35FP does seem to be more controllable out of the box than
>the 40FP.

In my wandering through the archives (and other sources) the 40 seems not to be a top choice.

Larry Fulwider

>I never heard of the "MAX-S" until just now. It was
>after my era, and before my current efforts.

I love the OS MAX-S series and have two each of the MAX-S .35 and MAX-S .30. A new MAX-S .35 was my first "big" glow engine, a Christmas present from my late grandfather back in about 1982 toward the end of their production life. The MAX-S .35 must have had a near record production run for an OS engine, from 1963 to some time in the early '80s.

The thing about the MAX-S was that it was so easy to set up and run that even as a brain-dead teenager without any experienced flyers to teach me, I was able to accidentally stumble on to the 4-2-4 break. Of course I didn't know it was called a 4-2-4 break. I chanced upon this setting when one flight of my Aeroflyte Aurora (old Aussie made flapless stunt kit) I set it a bit rich. I was rewarded with a lovely flight where it burbled along in four stroke and then snapped into a beautiful clean two stroke as soon as the nose went up. Lap time increased to the point where I could actually do something with the plane other than hang on for dear life and fly screaming wingovers with white knuckle pull-outs! I always set it that way from then on. That was on 5% nitro, 25% castor fuel, and an OS #3 plug. I didn't find out that was called a 4-2-4 break until returning to the hobby and seeing people talk about it on this site, then I realised that was what I set my MAX-S .35 to do back then.

I still have that engine - it will be going in my 40th birthday present Thunderbird mk1. IMHO it is one of the easiest to use engines I have ever owned.

cheers,
Colin