GrahamC

I just came into a NIB OS MAX .10S (from about 1966) but I really don't know much else about it.

It is the control line version and obviously earlier cronologically than the .10 FP but I don't recall much else of that era of OS engines. Jas a two piece muffler as well which I have never seen before - muffler body is two pieces, three actually with a little extension. Inner piece with extension bolts to engine then outer piece bolts to inner piece already bolted to engine. Sorry no picture but if anyone wants I can take one to post.

Anyone know any details? engine reviews?

It is a nice little engine now I just need to decide what nostalgia type plane to put it one, perhaps a 1/2a Texaco size Buzzard Bombshell.

cheers, Graham

rainedave

My Feedback: (1)

Is it similar to this marine version, but with the regular head and the muffler on 180° pointing backwards? I think some people call it the "Clamshell" muffler.

David

gcb

Graham,

Be sure to give it an iron/steel break-in.

George

rainedave

My Feedback: (1)

And, a great fuel to use is Powermaster GMA 5 or 10/29:

http://www.powermasterfuels.com/products/GMA.html

David

NorfolkSouthern

Sounds like an especially rare engine to me, especially in that condition. I'd check its value first before doing anything with it.

NorfolkSouthern

gcb

I would have suggested 10%-25% nitro and 20%-22% (half castor, half synthetic) lube.

I don't believe you need that much lube except for a Fox .35 and McCoy redhead stunts. If you've had good luck with that mix though, can't argue with success.


george

rainedave

My Feedback: (1)

George, I actually burn the GMA 5% nitro, 22% 50/50 oil in all my own engines, from brand new OS's to old Webras, ST's and Enyas. But, when dealing with an antique for which parts are so hard to find I suggested the oil overkill. It can't hurt to baby an engine like the old .10.

David

jeffie8696

SIG makes a 25%castor fuel that should work well . I use their 20% Castor almost exclusively in all my engines. What's it gonna hurt?

scott17

The instructions say: Break in fuel- 70% methanol, 30% casto... General-75% methanol, 25% castor ...contest-70% methanol,25% castor, 5% nitro. 7x4, 8x3, or 8x4 prop

BMatthews

It may be worth pulling the head to see if it is a loop, schnerule or other type of scavenging. The scavenging style will tell you a lot about what the power will be like.

GrahamC

Interestingly I have been unable to find much information on this engine.

It is a single bypass loop scavenged engine (piston has a baffle).

The instructions recommend for break in 70 to 75% methanol 25 to 30% castor and for C/L Stunt or Sport 65 to 70% methanol 25% Castor and 5 to 10% nitromethane. The instructions also make mention of the optional O.S. Jetstream Silencer which I am starting to think the muffler on this engine is.

The only online info I can find on the OS Jetstream Silencere is a wee bit here (with a couple of pictures) :

http://www.supercoolprops.com/articl...rsmufflers.php

Instructions also recommend 7x4 / 7x5 or 8x3 / 8x4 prop for flying.

A couple of pictures, first is one from OS's website which shows the timelines of the their engines this one from 1966, second is of my example, as is the third but with one half of the muffler removed to show it's construction.

I have an OS 10 FSR that is currently not in a plane so it is not like I really needed another engine to fly so I might just keep this one as is and put on display.

cheers, Graham

Andrew

Graham

If it's not too much trouble, you might pull the head and take a picture or two of the baffle. A lot of the younger guys that read this forum may never have seen a loop scavenged engine with a baffled piston.

andrew

dennis

My Feedback: (90)

The OS10S is an outgrowth of the old PET 09 engine The PET 09 was rather anemic and this was the evolution. If you check the OS timeline pictures you might see an engine that looks exactly as your does but labled as an 09 this was the last version of the PET and was sold concurently with the new 10 until stocks were gone.
These are delightful engines to run, have 1960's power, are long lasting provided you use the right fuel and break in procedures, they are perfect for a Sig Acrobat or any of the older 10 powered sport models.
Dennis

rainedave

My Feedback: (1)

I'll beat him to it since my scrap box is sitting next to me.

David

hkbii

Howdie gents. GrahamC. I have three of the older os ten with a carb that look like that. I ran them for years with 5% nitro and they ran fine. then one day at the fild all I had was some 15% so I ran it. now the head leaks so bad that it will not start. put some extra castro in the 5% and it should run fine. Hkbii.

gcb

I'll bet if you check your fuel you will find that the 5% was all-castor and the 15% was all or part synthetic. Iron/steel has a characteristic that castor will forma a varnish which fills the pores in the iron piston. This compensates for wear and forms a better seal. As little as 3% synthetic will remove this varnish seal. Using all-castor lube will get it back. Duke Fox used to exploit this characteristic with his Superfuel which would increase compression on a nearly worn-out engine, extending its life somewhat.

The high-silicon pistons in ABC engines does not do this...only iron.

Here is a picture of the RC version of the OS .10 along with three Pet .09's. Sorry for the camera distortion...the Pets really are all the same size.

George

hkbii

Howdi Gents . gcb now that I think on it your right. in the 70s and 80s all I ran was fox fuel.In the late 80s it got harder to find Fox fuel and I started useing synthetic. maybe thats why I had so meany engins belly up in one season. I'll keep that in mind when I whant to take one of my older engins out to play. Thank you . hkbii.

Ivanhoe

Hi Folks, the various versions of the OS 10 come up regularly on eBay, no-one seems to want them, I've picked up both the C/L & R/C versions recently in excellent condition for very little money. they are a very nice little sport engine, not great power, but boy! are they reliable!

SGC

I still have my first glow engine an OS Max .15 series3 steel fins, and its steel/steel as I suspect this engine to be, that said castor is still its best friend.
Stewart

gcb

Stewart,

If by series3 you are referring to the MAX-III, I THINK the piston/cylinder is iron/steel. Here are three of mine. One CL, two RC. The one with the butterfly exhaust restrictor is an early version and the one with the plastic throttle arm is a later version.

My first MAX was a MAX-I .15 and I've enjoyed good performance from ALL of my MAX's.

I agree whether iron/steel or steel/steel, castor oil is the best. I believe an iron/steel (or steel/steel like Cox) can benefit from part synthetic if near new. Part synthetic runs the engine clean which prevents excessive varnishing that the Cox engines are noted for. Kind of a double-edge sword.

I'm sure many of us will agree with you, the MAX-III .15 is one of the all-time greats.

George

balsaworks

Very true

The OS Max cross scavenged engines are great performers – not the most powerful, but powerful enough for sport and aerobatics, they are quiet, and they throttle beautifully.
Easy to handle & durable too. Besides the .10 there´s a .15, 20, 25, 30, and so on.
Enya has a matching line of cross scavenged engines in the same sizes, which are just as good or better. The smallest is labelled .09

Much has been written on this forum about the demise of the ½A engines; Cox, Norvel & others.
For engines in the upper end of the ½A spectrum, the early OS .10 & Enya .09, and the .15´s are terrific alternatives.

There are lots of them around and the uninformed masses seem to regard them as non-sexy, so one can find bargains, at you-know-where.
The early schneurle ported OS engines; the FSR and FP, before they got square heads, and blue colour, and whatever, are also un-sexy - terrific engines that can sometimes be found for cheap.

gcb

For you folks who have never run the older pre-ABC engines, the operating characteristics are different. The difference shows up quickly if you are inclined to tweek the last RPM out of the needle.

Where a plated brass cylinder expands more than the high-silicon aluminum piston keeping wear at a minimum, iron (or steel) pistons expand more than the iron cylinders to produce MORE heat via friction.

This increased temperature causes most synthetic lubes to "flash" and become fuel instead of lubricant. Good old castor oil in this case will thicken and get gummy. Depending on how lean, it may either slow the engine or get so thick it stops the engine. Although the castor might not completely eliminate damage, it may lessen it.

If you always needle correctly, this is not a problem.

And, of course, this is only one opinion.

George

rainedave

My Feedback: (1)

The Max .10 is one that's missing from my collection. I'll keep my eye's peeled for one.

I really like the old cross-flow, non-ringed engines. They start easily and run well. They also sound different than Schneurle ported engines. I don't think I paid more than $20 for any of these. Most I got for less than $15. It's a lot of fun cleaning them up and getting them back in running condition.

Follow George's recommendation and use castor oil fuel.

David

jeffie8696

Don't mention any of this to Probrojoe, he has been known to purchase a ten size engine , or 3.

Ivanhoe

If you want a 10S there's one on eBay.uk at the moment, (22/7/08) with original box and instructions, opening bid is 1p (About 2cents)!