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Engine basics => Engine set up tips => Topic started by: Bootlegger on August 02, 2019, 10:33:14 AM
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I have read where some of you men are running 10x3 A P C props on the OS plain bearing 25 engines, but I haven't had any success using this set up. Will the ones that have used this set up be willing to share your success? Thanks,
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I have read where some of you men are running 10x3 A P C props on the OS plain bearing 25 engines, but I haven't had any success using this set up. Will the ones that have used this set up be willing to share your success? Thanks,
It's sometimes OK on a 25FP, but usually there isn't enough poop on the 20FP or 25LA. Start with an APC 9-4 on any of these engines, alternate is a 10-4 APC.
Both are hopeless on the baffle-piston 25S, not nearly enough power to spin it the required RPM with any margin.
Brett
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hanks Brett...
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Should read Thanks Brett...OOOPS
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Should read Thanks Brett...OOOPS
Which specific engine are you talking about? I know of at least 4 markedly different plain-bearing OS25 engines - 25S (baffle piston), 25FP, 25LA (early), 25LA (late). The 25LA (late) is the best stunt engine of that group, the 25FP is the most powerful by a long shot, but much harder to deal with the 25LA (late).
Brett
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Hello
I have some OS25S baffles on stunt and combat planes and they are not powerhouses probably a lot less h.p. then a Magnum or LA15 on a combat going off airspeed.
Been using a 8x6 (big venturi, muffler pressure, yes we must use mufflers here) for combat and 9x4 (small venturi) for stunt.
How does one tell early and late LA 25 's apart. I know people use LA25's for slow combat as well as stunt and presume the early LA 25 is better suited to combat like a FP25 .
There seems to be a big demand for LA 25's and it is a pity OS has not remade them like has been rumored.
Regards Gerald
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(http://sceptreflight.com/Model%20Engine%20Tests/OS%20Max%2025-2.jpg)
These 1970s max 25s like a 8x6 or 9 x 4 . a Zinger 9 x 5 isnt bad at all , a 9 x 6 likely a bit to much load , unless its a light plane .
Theyll run pretty good on no nitro in summer . a 7 x 8 in a team racer .
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Hello
I have some OS25S baffles on stunt and combat planes and they are not powerhouses probably a lot less h.p. then a Magnum or LA15 on a combat going off airspeed.
Been using a 8x6 (big venturi, muffler pressure, yes we must use mufflers here) for combat and 9x4 (small venturi) for stunt.
I think you would probably do better with a 9-5 or even a 9-6 for stunt than a 9-4. It will go fast enough with a 9-4, but it won't have anything in the maneuvers. And beware of breaking the crankshaft, at high revs, it *will* break. That's what mine did!
Brett
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Brett, I have some of the late and a couple of "I ain't sure" ones also, thanks for the help/advice..
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Brett, I have some of the late and a couple of "I ain't sure" ones also, thanks for the help/advice..
You mean, they are 25LAs? You have never actually said what engine you are talking about here...
The test for the 25LA "late" and "early" versions is to run them on the ground, put on an APC 9-4, and peak them out lean. The "late" engines will spin up pretty easily to the upper 13,000 to 14000 range, the "early" will be in the upper 12,000s at most.
All the "early" engines we have had were blue, all the "late" versions were bare metal. That doesn't necessarily mean that there aren't good blue ones, or weak silver ones, just that this is what we have found so far.
Brett