OS MAX H-40 RR ?? need info please

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OS MAX H-40 RR ?? need info please

Postby tomporsche » Sun Jan 13, 2008 7:41 pm

:?: Hi folks I have an old OS Max H-40 RR.
Did the RR indicate this was a Rat Race engine ??
It has a huge venturi, which is reduced with an insert.
Were these competitive racing engines in their day? Comparable to K&B,
Super Tigre, Fox ???
I'm guessing it is from the early 70s'
I have owned it for years, but never used it. It is in great shape, good compression, looks good, but has 6 mounting holes ???
I am interested in maybe using it for a class c/d nostalgia free flight ship.
I also have some old Fox combat specials I could use. which would be better ? The foxes are probably a bit lighter, but the Max is in excellent condition.
Any info would be appreciated.
Thanks, Tom :?: :?:
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os 40 RR

Postby flying dutchman » Sun Sep 14, 2008 10:02 am

Hello,I bought one five years ago and it is nib,only has the original four mounting holes. flyingdutchman
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Postby Frank Klenk » Sun Sep 14, 2008 4:00 pm

Tom

Your OS dates to 1965. I am really no expert on that one so I don't know what the RR signifies. First I thought it may be rear rotor, but your engine is front rotary according to pictures. So it may well be rat race. OS has always made good quality engines so I see no reason to believe why this one should not be a good performer, unless any users out there have information to state otherwise.

Frank :)
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OS 40 RR

Postby tomporsche » Sun Sep 14, 2008 5:53 pm

Thanks for the replyFrank.
1965 !!! I didn't realise it was that old.
Thanks again,
Tom
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Postby ffkiwi » Mon Sep 15, 2008 6:16 pm

Yes the 'RR' does signify 'Rat Race' these were quite potent for the era but didn't get much of a following probably because of limited availability and cost compared with Fox and K&B. It is closely related to the OS Max H29R 'B' team race engine which achieved more success internationally. IIRC the same crankcase did duty for about 6 different models-the H29R, the H35C, the H40RR, the H40P pylon and the H40S-some twin BB, some single rear BB supplemented by a bronze bush.

'ffkiwi'
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Postby tomporsche » Tue Sep 16, 2008 8:20 pm

Thank You for your reply, I am learning more and more about this fine engine. My original intent was to sell it, But the more I learn, I just might keep it and build that C free flight plane I always wanted.
It probably would not be a good sport engine, although it has a restricted venturi. It probably would not 4 stroke like a good stunt motor.
It is in very good condition,,, Not sure yet to keep it, or give it a better home.
Thanks again,, Tom
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Postby ffkiwi » Wed Sep 17, 2008 9:28 pm

I doubt that this engine would be suitable for stunt. IIRC there were a lot of differences between the different models and from memory the only common parts were the basic casting, the backplate and possibly the conrod. piston liners, cylinder heads and crankshafts were all different depending on the designed use for the engine. The 40RR would have been designed and set up for pressure feed and a lot of nitro-and even if sleeved down with a small venturi and decompressed, the cylinder port timing would not have lent itself to a good stunt 4-2-4 transition. Build a C-class FF for it!

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