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Engine basics => Engine set up tips => Topic started by: brucefinley on April 09, 2007, 03:46:32 PM
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Been playing with a Frank Bowman ST V51(not G) on a Brodak Arf p-40. I'm using Powermaster 10% 22% 50/50 and thunderbolt plug. I ran it on the bench for about 20-30 minutes for 3-4 minute intervals and have flown the setup now about a dozen times. I know the thing could use more break in time but I have to say it is acting a bit strange. Sometimes it will lean out and runaway during the flight, other times it will get stuck in a low power 4 stroke. I have tried different tanks I am running a APC 11.5x4 right now as it didn't seem to want to pull anything bigger.
I did try taking off the tongue muffler today and seemed to get a better run. Is it overheating and running away? Do I need to add head gaskets?
Thanks to all,
Bruce
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I dont know about the ST, but I use that prop on my FP .40,, I would guess that you may need a larger prop? however, I am NOT an expert, just my two cents worth
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I dont know about the ST, but I use that prop on my FP .40,, I would guess that you may need a larger prop? however, I am NOT an expert, just my two cents worth
Agreed. That's not much prop for a .51. That engine should run just like the .46 or .60. Which plug are you using? If you took off the tongue muffler and the run got better, I'd say it might be getting hot.
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Been playing with a Frank Bowman ST V51(not G) on a Brodak Arf p-40. I'm using Powermaster 10% 22% 50/50 and thunderbolt plug. I ran it on the bench for about 20-30 minutes for 3-4 minute intervals and have flown the setup now about a dozen times. I know the thing could use more break in time but I have to say it is acting a bit strange. Sometimes it will lean out and runaway during the flight, other times it will get stuck in a low power 4 stroke. I have tried different tanks I am running a APC 11.5x4 right now as it didn't seem to want to pull anything bigger.
I did try taking off the tongue muffler today and seemed to get a better run. Is it overheating and running away? Do I need to add head gaskets?
Thanks to all,
Bruce
Hard to tell, but with 10% nitro, it could be experiencing some "overcompression". The engine guys tell me that more notro works in a way very similar to raising the compression. Might try 5% if you have any.. I always use a 12" on my G51, and many guys were using 12" on the .46.
Bob Lampione left a Big Jim reworked "V" 51 here and it has his "signature" hemio head.
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I ran a new R/C version of the ST51 in a Hanger 9 Twist. Prop was a 12.25X3.25 APC . Fuel was Powermaster 10/18.The runs were unbelievably smooth and consistant, and fuel economy was excellent. Now if I can just get an appropriate C/L model done for the C/L version. So many motors, so little time.
Dennis
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Been playing with a Frank Bowman ST V51(not G) on a Brodak Arf p-40. I'm using Powermaster 10% 22% 50/50 and thunderbolt plug. I ran it on the bench for about 20-30 minutes for 3-4 minute intervals and have flown the setup now about a dozen times. I know the thing could use more break in time but I have to say it is acting a bit strange. Sometimes it will lean out and runaway during the flight, other times it will get stuck in a low power 4 stroke. I have tried different tanks I am running a APC 11.5x4 right now as it didn't seem to want to pull anything bigger.
I did try taking off the tongue muffler today and seemed to get a better run. Is it overheating and running away? Do I need to add head gaskets?
Thanks to all,
Bruce
HI Bruce
The ST 51 likes to have some pitch when it runs, they run very well on a Bolly 12.5 x 5.5 , Bolly 12 x 6, Bolly 12 x 6.5n 3 blade , BYO 12 x 5, New Zinger 12 x 5, Old zinger 12 x 6, and several other props of the same range, I have found the prop you are using on it to be good for a Thunder Tiger 36.
You need to "load" an engine for a good 2-4 break, too Small a prop or no load and it will just run around in a "dumb" run without cycling
Try more prop and more pitch, and you should not need 10% until the summer heat gets here, I would start with 5%.
By the way many have used this motor with a 11 x 7 4 blade too. I have setup hundreds of the ST engines and I think you will find this helps. I ran the same Motor on a Magnum with 5% nitro 12 x 6.5 n 3 blade and it flew all 4 with just nice 2 cycle beeps across the tops of the maneuvers
Regards
Randy
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Just posted on a thread with like discussion in the Magnum thread.. Guess I don't understand.. Isn't the reason to move to a larger engine so you can swing a larger prop, hopfully for more controlled power. I swapped a ST46 out for a ST 51, if I kept the same prop I had on the 46 what did I gain other than a couple extra ounces?
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I started with a 12" prop and the motor tended to run very hot and sag, therefore I figured gee, this engine is not broke in yet or the compression is too high maybe or too much nitro in my fuel for the ambient temps. So I fit a smaller prop. The smaller prop did let it run without overheating. I installed the only 12" prop I had, a MA 12x6, I removed the tongue muff and it was able to run a bit cooler and seems to run a bit better and with more power. I'm thinking it just needs more time.
bruce
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I think you have defined the problem. As others have said reduce the nitro, and/or add some head shimm to decrease the compression. I to have an ST .51 first think I did was order up some head gaskets from Tower to drop the compression.
Andy
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I started with a 12" prop and the motor tended to run very hot and sag, therefore I figured gee, this engine is not broke in yet or the compression is too high maybe or too much nitro in my fuel for the ambient temps. So I fit a smaller prop. The smaller prop did let it run without overheating. I installed the only 12" prop I had, a MA 12x6, I removed the tongue muff and it was able to run a bit cooler and seems to run a bit better and with more power. I'm thinking it just needs more time.
bruce
Hello Bruce
With a very OLD V ST 51 I cannot believe you have a too high cpmpression problem, these were not high compression engines to start with, Do you have 1 ring or 2? It sounds like you maybe need more breakin time, or you need to up the pitch and nitro so you can run the engine richer...thus cooler
let us know how it works for you
Randy
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It is a 2-ring motor. Frank Bowman rebuild. Hope this helps.
Bruce
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It is a 2-ring motor. Frank Bowman rebuild. Hope this helps.
Bruce
HI Bruce
Yes that will make a BIG differance, the 2 ring motors do NOT like to ryn hard or be pushed hard, they are a lot happier on higher nitro high prop pitch and richer runs. The dual ring has much more drag, and thus friction, so It will heat up faster than teh single ring, and if the ring gaps are really tight this will need a lot of breakin.
I also assmume this is a chromed sleeve motor, most of them were. Keep putting more time on the engine and try the other suggestions, I think you will have a good engine soon
Regards
Randy
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I agree that that the engine needs more load. another thing is the fuel. Tigres like lots of caster to get a good engine 2-4 break.