O.S.Max H-.40 RR ???

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O.S.Max H-.40 RR ???

Postby tomporsche » Sun Jan 13, 2008 7:01 am

Hi Folks, I have a few questions about an old Max engine that I have had for years. A H.40 RR.
I bought this many years ago to use on a C free flight ship that never got built. Did the RR mean Rat Race ??
I thought it did. This thing is like new inside, has wonderful compression, turns over freely. Were they good RR motors? I know O.S. always made high quality stuff, but, was this a strong runner. say like a ST. 40. or a Fox Combat special ? I am considering building that C gas ship, and using this engine, now that I am retired and have the time. Would this be a ghood choice. Were they competitive in their day?
Or I just might sell it. Not sure. If you will give me the lowdown. It is a long time since I acquired it, and I'm guessing it was made in the 70s'
I still have the box and instructions for the R/C version in the box.
Thanks. Tom
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rr .40 OS

Postby lfinney » Wed Feb 25, 2009 2:16 am

hi

this motor was used as a freeflight, pylon, and marine contest engine,unless abuse they were very reliable, and were competitive in free flight and ratrace, pylon was owned by ST and K&B
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Postby tomporsche » Wed Feb 25, 2009 11:00 am

Thanks for the reply.
I'm happy to hear that it was a competitive engine in Rat Race.
I would think it would be OK on pressure, or a bladder for C free flight.

It is kind of heavy by todays standard, but as I remember OS engines in general were easy to start, and dead reliable.

Any idea about what fuel to use?
How much nitro/oil?

I have had a few inquiries about selling it, and I really don't have a clue what it might be worth.

If it is worth less than $100.00, I may as well keep it for my own use,
as I couldn't replace it with ANY modern .40 for less than that.
On the other hand, If an OS collector was interested in it,
I might sell it or swap.

Again thanks for your reply.
Tom Hartman

If you prefer to reply away from the forum,
my e-mail address is:
thart9146@comcast.net
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Postby chiefss » Wed Feb 25, 2009 3:17 pm

It was a Rat Race engine. It came out in 1965. The upper left backplate screw was a pressure fitting. Rat Race was big in the 60's and the max engine size was 40. I used Johnsons when I flew Rat. Usually a 36BB but I did use a 29R.

The Johnsons were always one flip starters, hot or cold, and in Rat Race that was everything.

I always ran 15% nitro and 20%castor oil in those days. Still do actually. Some guys ran higher nitro and Fox Blast was a fuel some guys used. It was 50% nitro. Made the engine needle more touchy and they wore out a lot faster. Also was harder than heck on the rod. You could make up the small lack of speed using lower content fuel by having a good pit crew and being a better flyer.
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Postby tomporsche » Wed Feb 25, 2009 6:41 pm

Thanks for the info, I appreciate it,
I think I will hang on to it,

Tom
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Postby loucrane » Mon Mar 30, 2009 9:27 pm

Tom,

Fuel usually depends on the metals in the cylinder and piston. Plain or BB shafts are quite a bit less critical...

ABC/ABC/AAC engines are usually cut so that they have ideal clearances at running temperatures, so the 10%-10% oil (castor-synthetic) fuels do well in them.

Oddly, high performance operation, like racing CL or FF, usually isn't as critical to oil or %. You run just enough rich so it doesn't blow up or weld shut, and that gives enough oil... Less load - has to be, or the RPM wouldn't be there - plays a part in this.

If yours is an iron piston in steel sleeve, it will probably run better and last longer with an all-castor oil portion, but at high RPM may not need more than a total oil % of 20%-22%. Castor doesn't burn inside the engine unless things are past the top of the hill. Synthetics burn at a critical few dozen degrees cooler. Summing that: Castor absorbs a lot of heat and carries it out the exhaust port; synthetics may burn, adding to heating, and not carry much - if any - heat out the door while it is open.

In any event, you have a pretty special engine. Parts may not be easy to find, so be as gentle as needed to keep it going for you for a good long time. It was designed to work hard, so gentle does not mean pussy-footing!
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O.S. Max .40 RR

Postby tomporsche » Tue Mar 31, 2009 4:57 am

Thanks for the valuable info on fuel for my Max 40 RR.
It is a really sweet engine. I haven't run it in years, and in fact it wasn't run much past break in [if that much].
Should I use it in a C free flight ???
Or sell it,,and give it a good home.
Your opinion.
Thanks, Tom
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Postby Jim » Tue Mar 31, 2009 6:35 am

Fly it! That's where it deserves to be !!
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Postby chiefss » Tue Mar 31, 2009 1:44 pm

Go ahead and fly it but remember if you prang it, parts are very hard, if not impossible, to find. It's probably worth more as a collectable. I'd buy it if the price was right. It would sit on a shelf in a place of honor with all it's brothers and sisters
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Postby Jim » Tue Mar 31, 2009 1:46 pm

As a freeflighter - I'd fly it !!
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Re: O.S.Max H-.40 RR ??? I sold it

Postby tomporsche » Thu Apr 23, 2009 8:58 am

I sold it to a fellow in England.
Thanks. Tom[/quote]
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bb

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