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Model Forum / Radio Controlled / Air Models / January 2007



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OS Max-S 35 Engine info

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Ook - 28 Jan 2007 01:25 GMT
OK, this is what it is. It's an OS Max-S 35 engine, made for r/c. The
"throttle" is simply a baffle the goes over the exhaust, and obstructs the
exhaust port to slow the engine down. It's very clean, and I have the
original box and instructions, which are a bit yellowed with age. There is
no actual model number on it other then max-s. The instructions also don't
give model or serial other then Max-s 35. The box says S35/R.C.  No idea at
all how old it is, or how much it's been run.

I searched their website, and the closest I could get to this was a Max 40
that has been discontinued. I did a bit of research and it looks like these
were in production about 35-40 years ago, people talk about using these in
the last '60s. (is this thing really that old?).

Questions:

Can I remove the throttle and use it on a control line plane?
Is there any way to tell how old or how many hours are on the engine without
taking it apart and measuring clearences?
Robert Reynolds - 28 Jan 2007 04:39 GMT
> OK, this is what it is. It's an OS Max-S 35 engine, made for r/c. The
> "throttle" is simply a baffle the goes over the exhaust, and obstructs the
[quoted text clipped - 14 lines]
> Is there any way to tell how old or how many hours are on the engine without
> taking it apart and measuring clearences?

Measuring clearances is a bit more involved than most of us get.  If you
find an old engine and you think you may want to run it, standard
procedure is to make sure it's clean and free of dirt, mount it on a
plane, and see if it runs.  If so, mission accomplished.
Frank Schwartz - 28 Jan 2007 05:55 GMT
It's an oldie all right...it was made before mufflers became
mandatory, so I would hazard a guess that it is at least thirty
years old.  Not a screamer, but you could throw away the baffle and
lock the throttle barrel open and use it for C/L...and you might find
a muffler to fit it, if required where you fly C/L.  I think OS made
one that strapped on later.
Frank
mjd - 29 Jan 2007 02:11 GMT
I have an old OS Max .35 I am cleaning up and checking out for a buddy, that
was only delivered to me today as a matter of fact, and it has a fairly
contemporary looking cast aluminum muffler but of the strap-on variety. If
the example Ook is referring to (Ook being a word I used frequently in my
teens and early twenties I find this a mild case of deja vu..) has a similar
case then there is hope for a muffler that fits somewhere out there in the
ether. If not, is Bisson still in business?

Although, form first appearances the prognosis is not good for the slop in
the con rod's small end, although the big end is fine. We'll see.. maybe
spin up an oversize wrist pin and... then again maybe not.

MJD

> It's an oldie all right...it was made before mufflers became
> mandatory, so I would hazard a guess that it is at least thirty
[quoted text clipped - 3 lines]
> one that strapped on later.
> Frank
Ed Cregger - 29 Jan 2007 02:23 GMT
>I have an old OS Max .35 I am cleaning up and checking out for a buddy,
>that
[quoted text clipped - 19 lines]
>> one that strapped on later.
>> Frank

There are quite a few sources of workable mufflers for this engine (OS Max
.35S). Mac's makes mufflers from tubing that resemble tuned mufflers
somewhat. I'm sure they would have a universal strap-on version. If not, how
hard could it be to buy an old fashioned radiator hose clamp at an auto
supply store and fit it to one of these mufflers? Piece of cake.

And yes, Bisson is still around. Good company and products.

Tatone even sells manifolds and such that are strap-on, so they would fit
also.

Ed Cregger
Robert Reynolds - 29 Jan 2007 02:32 GMT
>> I have an old OS Max .35 I am cleaning up and checking out for a buddy,
>> that
[quoted text clipped - 32 lines]
>
> Ed Cregger

I read a really nifty article in RCM a few years ago about making
mufflers from aluminum bar stock and tubing.  It wouldn't be too hard,
if you have a few power tools.
Ed Cregger - 29 Jan 2007 05:03 GMT
>> There are quite a few sources of workable mufflers for this engine (OS
>> Max .35S). Mac's makes mufflers from tubing that resemble tuned mufflers
[quoted text clipped - 12 lines]
> from aluminum bar stock and tubing.  It wouldn't be too hard, if you have
> a few power tools.

---------------

Yep, it isn't difficult at all.

I just bought one of Harbor Freight's el cheapo combination vertical mill
and lathe units ($600). I plan on making a few adapters so that we can fly
the old Fox Eagle .60 (baffle piston) engines again. Most Eagle .60s for
sale are sans muffler. Not that the stock muffler was much to begin with.

I'll use aluminum plate to make my adapters. I'll pick a cheap to purchase
muffler, like the Tower .46 muffler, and adapt it to the Fox Eagle 60. It
should be plenty big enough and it may even offer a slight boost in power.
We shall see. If not the .46 size, then the .60-.75 size.

Ed Cregger
Robert Reynolds - 29 Jan 2007 15:01 GMT
> I just bought one of Harbor Freight's el cheapo combination vertical mill
> and lathe units ($600). I plan on making a few adapters so that we can fly
[quoted text clipped - 7 lines]
>
> Ed Cregger

We have a metal retailer here in Kansas City called Metal By The Foot,
where you can buy just about anything with no minimum size.  They have a
very handy scrap bin full of little chunks of aluminum bars, plates, and
tubes for a couple dollars or less.  I always see airplane parts when I
look in those bins.  All I need is one of those milling machines.
Ed Cregger - 29 Jan 2007 16:33 GMT
> We have a metal retailer here in Kansas City called Metal By The Foot,
> where you can buy just about anything with no minimum size.  They have a
> very handy scrap bin full of little chunks of aluminum bars, plates, and
> tubes for a couple dollars or less.  I always see airplane parts when I
> look in those bins.  All I need is one of those milling machines.

----------

Hi, Bob.

I'll have to look around and see if we have anything similar in the
Chattanooga, TN area. That would really reduce the price of producing the
parts that I have in mind.

Ed Cregger
Ook - 28 Jan 2007 06:14 GMT
> Measuring clearances is a bit more involved than most of us get.  If you
> find an old engine and you think you may want to run it, standard
> procedure is to make sure it's clean and free of dirt, mount it on a
> plane, and see if it runs.  If so, mission accomplished.

I wasn't too serious about measuring clearances. I don't have the equipment
to measure the kinds of clearances you see in these engines - my micrometers
aren't accurate enough. And it wouldn't tell me much. I like to squirt some
lightweight oil in them and turn the crank until the piston is at TDC. Then
wait and see how fast the pressure bleeds past the piston. Even light
machine oil is relatively heavy for these engines, so it had better hold the
pressure real good. This one does, and the crank is nice and tight
indicating no wear in the connecting rod to crank connection. I'm not a
collector - I want to run this puppy until it dies :)
Ed Cregger - 28 Jan 2007 06:43 GMT
>> Measuring clearances is a bit more involved than most of us get.  If you
>> find an old engine and you think you may want to run it, standard
[quoted text clipped - 10 lines]
> and tight indicating no wear in the connecting rod to crank connection.
> I'm not a collector - I want to run this puppy until it dies :)

------------

Whether an engine holds compression for so many seconds/minutes is totally
irrelevant. What is necessary is that it holds compression for the
milliseconds that it is required when running. Why create standards that
have no basis in reality?

Ed Cregger
Morgans - 28 Jan 2007 07:44 GMT
> Whether an engine holds compression for so many seconds/minutes is totally
> irrelevant. What is necessary is that it holds compression for the
> milliseconds that it is required when running. Why create standards that
> have no basis in reality?

I'm glad I'm not the only one thinking that.

At 12,000 RPM, the compression is being formed and released 20 times per
second.

You could have a brick going up in a piece of pipe casing, and get
compression, that fast! <g>
Signature

Jim in NC

Robert Reynolds - 28 Jan 2007 15:59 GMT
>> Whether an engine holds compression for so many seconds/minutes is
>> totally irrelevant. What is necessary is that it holds compression for
[quoted text clipped - 8 lines]
> You could have a brick going up in a piece of pipe casing, and get
> compression, that fast! <g>

At any rate, it sounds as if he has the right idea.  Start it up and run
it.  If you're having fun, it's working right.
Morgans - 28 Jan 2007 20:36 GMT
> At any rate, it sounds as if he has the right idea.  Start it up and run
> it.  If you're having fun, it's working right.

That's the acid test!

If it won't keep running, with good fuel and good technique, then it might
be worn out. <g>
Signature

Jim in NC

Ook - 28 Jan 2007 19:55 GMT
>> Whether an engine holds compression for so many seconds/minutes is
>> totally irrelevant. What is necessary is that it holds compression for
[quoted text clipped - 8 lines]
> You could have a brick going up in a piece of pipe casing, and get
> compression, that fast! <g>

Ouch, gimme a break, guys :-)

What is the first thing you do when you pickup a second hand engine? You put
a prop on it, squirt a few drops of fuel or oil into it, and turn it over.
If it freewheels, then it might be too worn out to be usable :-P
Morgans - 28 Jan 2007 20:40 GMT
> Ouch, gimme a break, guys :-)
>
> What is the first thing you do when you pickup a second hand engine? You
> put a prop on it, squirt a few drops of fuel or oil into it, and turn it
> over. If it freewheels, then it might be too worn out to be usable :-P

Yeah, OK! <g>

I never did the oil test, but I realize that would help.  I could tell by
the resistance and the sound of the "pops" if it was any good to give it a
try, I think.

If it was questionable, I would want to run it before buying it.
Signature

Jim in NC

Ed Cregger - 28 Jan 2007 21:23 GMT
>> Ouch, gimme a break, guys :-)
>>
[quoted text clipped - 9 lines]
>
> If it was questionable, I would want to run it before buying it.

--------------

Does anyone remember when the K&B .40 came out with the Dykes ring? A bunch
of them were sent back to K&B and were claimed to be defective because they
wouldn't pass the old compression test that Ook is referring to. <G>

I'm not picking on you, Ook. Well, maybe a little, but it is all in fun.

Ed Cregger
Ook - 28 Jan 2007 22:13 GMT
> Does anyone remember when the K&B .40 came out with the Dykes ring? A
> bunch of them were sent back to K&B and were claimed to be defective
[quoted text clipped - 4 lines]
>
> Ed Cregger

It's all good :-)
Red Scholefield - 28 Jan 2007 19:19 GMT
The S35 indicates that it started production in 1963.  The picture on the
web site http://www.osengines.com/history/ostimeline03.html however shows it
with what appears to be a strap on muffler.

Red S.
> OK, this is what it is. It's an OS Max-S 35 engine, made for r/c. The
> "throttle" is simply a baffle the goes over the exhaust, and obstructs the
[quoted text clipped - 14 lines]
> Is there any way to tell how old or how many hours are on the engine
> without taking it apart and measuring clearences?
Ed Cregger - 28 Jan 2007 19:48 GMT
> The S35 indicates that it started production in 1963.  The picture on the
> web site http://www.osengines.com/history/ostimeline03.html however shows
[quoted text clipped - 19 lines]
>> Is there any way to tell how old or how many hours are on the engine
>> without taking it apart and measuring clearences?

The OS Max .35S R/C was being sold well into the late Seventies, at least.
Yes, later on it came with a strap-on muffler.

There is no need to remove the throttle. Just use a short pushrod and keep
it at open throttle with the pushrod fastened to somewhere on the
firewall/fuselage. Then, if you decide to fly R/C at a later date, or want
to sell the engine to an R/C flyer, you'll have everything in good working
order.

This engine requires 25% all castor oil lubricant in order to survive
running for any period of time. I've owned and flown half a dozen of these
sweet engines. Never came close to wearing one out. Even without the
requisite 25% all castor lube.

Ed Cregger
 
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