ASP vs. OS
05-20-2008, 08:23 PM
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RE: ASP vs. OS
ORIGINAL: AMB
I got lucky last year and picked up a BX1.08 in pristine shape. It now wears a Davis diesel head . Its been a while since its run, huge prop (do not remember size, super idle it is slated
for a big telemaster (most likely this is overkill) martin
my biggest ASP is a 90 nice engine but OS qualilty it is not
I got lucky last year and picked up a BX1.08 in pristine shape. It now wears a Davis diesel head . Its been a while since its run, huge prop (do not remember size, super idle it is slated
for a big telemaster (most likely this is overkill) martin
my biggest ASP is a 90 nice engine but OS qualilty it is not
05-21-2008, 01:44 AM
#27
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RE: ASP vs. OS
ORIGINAL: mjderstine
you will be happy to know that i have just purchased TWO OS BS-1 1.08 engines.
i got bit by the 1.08 bug.
you will be happy to know that i have just purchased TWO OS BS-1 1.08 engines.
i got bit by the 1.08 bug.
When I first saw the OS 1.08, I didn't like the looks of the three bolt muffler attachment. Stupid reason to avoid an engine, but I did, just because of that. Little did I know that this engine would turn out to be one of OS' finest engines ever produced (there goes the price on the used market!).
A good friend of mine, Syd Clement of Bridgeton, NJ, was the one that converted me to an OS 1.08 lover. Syd seldom flew OS engines. He was more of a Rossi and YS kind of guy. He showed up at our field one day with another highly modified Bridi Trainer 60. He is the one that got me hooked on Bridi RCM Trainers as well, but that's another story. Anyway, Syd had fitted an inverted OS 1.08 on the nose with a tuned pipe. Tuned pipes were the rule for Syd. Not the exception, but I had never seen a tuned pipe mounted to an OS 1.08 before. To get the necessary prop clearance, Syd had eliminated the windshield of the Trainer .60 by taking a straight horizontal line from the wing mounting area of the fuselage and mounting the engine, inverted, as high as he could. It really looked a lot better than it sounds.
Syd fired up the 1.08. Let it warm up a bit, checked the high speed needle, just in case, backed away a few fit and went to high throttle. The model, which probably weight eight or so pounds, rolled about two feet and then lept off the ground going straight up in a hurry. Neat.
I asked him about the timing and he admitted that he had raised the exhaust port just a tiny bit, in order to "help" the tuned pipe breathe a bit better. Believe me, it worked.
I never viewed the OS 1.08 the same way again. <G>
Ed Cregger
05-21-2008, 02:18 AM
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RE: ASP vs. OS
I am also running my OS108 "with the famous OS7D carb" on a quiet tuned pipe and this engine just like most other modern twostrokes loves the tuned pipe and I love the way it runs
Also fitted a Perry VP-30 so I can have the fuel tank about 10" from the engine. Using OS-F glow plug the acceration from idle is instant or as fast as the throttle servo can move
In one word an very very nice running engine and carburetor!
Also fitted a Perry VP-30 so I can have the fuel tank about 10" from the engine. Using OS-F glow plug the acceration from idle is instant or as fast as the throttle servo can move In one word an very very nice running engine and carburetor!
05-21-2008, 08:10 AM
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RE: ASP vs. OS
when i was growing up my brother had one of these 108's on his SR telemaster. he decreased the dihedral a little, and my father helped him build a luan ply fuselage for it. needless to say the thing flew more like a pattern plane than a giant trainer. he flew a 15-8 prop, which was the best for that application. i am glad there are still some good ones around.
now we need to get OS to start making them again!
now we need to get OS to start making them again!
05-23-2008, 03:44 PM
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RE: ASP vs. OS
Ed,
I have a Goldberg Wild Stick 120 (10 lbs). I just installed the Maggie 108 and with a 15x4 Master Airscrew it was really weak (like a trainer). I installed then tried a 14 x8 and a 14x6 both were better but still not much vertical. Do you think a 15 x8 will be better? It seemed to me that with the 15x4 it would not wind up as fast as it should, although I did not use a tach just going on its performance.
Troy
I have a Goldberg Wild Stick 120 (10 lbs). I just installed the Maggie 108 and with a 15x4 Master Airscrew it was really weak (like a trainer). I installed then tried a 14 x8 and a 14x6 both were better but still not much vertical. Do you think a 15 x8 will be better? It seemed to me that with the 15x4 it would not wind up as fast as it should, although I did not use a tach just going on its performance.
Troy
05-23-2008, 04:28 PM
#31
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RE: ASP vs. OS
The original ASP 1.08 (Sanye, like Magnum and SC) instructions said to run the red head version at about 9k rpm and that it was not a revver, but a torquer. I wouldn't be afraid to try a 15x8. That should run it where it likes to be ran.
Ed Cregger
Ed Cregger
05-28-2008, 10:00 AM
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RE: ASP vs. OS
ORIGINAL: TROY01
Ed,
I have a Goldberg Wild Stick 120 (10 lbs). I just installed the Maggie 108 and with a 15x4 Master Airscrew it was really weak (like a trainer). I installed then tried a 14 x8 and a 14x6 both were better but still not much vertical. Do you think a 15 x8 will be better? It seemed to me that with the 15x4 it would not wind up as fast as it should, although I did not use a tach just going on its performance.
Troy
Ed,
I have a Goldberg Wild Stick 120 (10 lbs). I just installed the Maggie 108 and with a 15x4 Master Airscrew it was really weak (like a trainer). I installed then tried a 14 x8 and a 14x6 both were better but still not much vertical. Do you think a 15 x8 will be better? It seemed to me that with the 15x4 it would not wind up as fast as it should, although I did not use a tach just going on its performance.
Troy
the 15x8 will be the best prop you can find for the 1.08. i have tested coutless props and the 15x8 was the best for my application. you may try a 14x10 or 14x8 also.
06-11-2008, 03:59 PM
#35
RE: ASP vs. OS
The instructions on mine are the same as the instructions on my .91 Red Head. I don't think it said anything about an RPM limit. But it also said it was good for 15% nitro, so anything it may say is obviously of no value.
06-11-2008, 10:38 PM
#36
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RE: ASP vs. OS
ORIGINAL: Sport_Pilot
The instructions on mine are the same as the instructions on my .91 Red Head. I don't think it said anything about an RPM limit. But it also said it was good for 15% nitro, so anything it may say is obviously of no value.
The instructions on mine are the same as the instructions on my .91 Red Head. I don't think it said anything about an RPM limit. But it also said it was good for 15% nitro, so anything it may say is obviously of no value.
Jim Goad was pulling his hair out over the ASP engines and their high compression, from what I have heard and read. I spoke with him once or twice and picked his brains thoroughly. Good man.
Some of the early ASP engines lacked bushings in the upper end of the connecting rod, had soft crankshafts (bent easily), etc., but, if coddled by using lots of castor oil and low nitro (or put the headshim in place), they ran well and lasted long enough to please anyone. Being Chinese, a bad casting or something machined off spec was not uncommon. All one had to do was contact Indy R/C and the problem would be solved.
There were many different instruction sets and box colors in the early years. Over time, information sort of runs together in the memory. I could have read the 9k rpm comment in an engine review, or perhaps Jim, or one of his technicians, told me on the phone. I felt certain that my instructions said to prop for 9k rpm, for what it's worth. I do not claim to be an encyclopedia of absolutely accurate information, so you're wasting your time by continually disagreeing with me on each and every point, just to be a PITA. Are you and loughbd related?
Ed Cregger
06-11-2008, 11:23 PM
#37
RE: ASP vs. OS
There were many different instruction sets and box colors in the early years. Over time, information sort of runs together in the memory. I could have read the 9k rpm comment in an engine review, or perhaps Jim, or one of his technicians, told me on the phone. I felt certain that my instructions said to prop for 9k rpm, for what it's worth. I do not claim to be an encyclopedia of absolutely accurate information, so you're wasting your time by continually disagreeing with me on each and every point, just to be a PITA. Are you and loughbd related?
06-12-2008, 11:37 PM
#39
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RE: ASP vs. OS
ORIGINAL: TROY01
Ed,
I have a Goldberg Wild Stick 120 (10 lbs). I just installed the Maggie 108 and with a 15x4 Master Airscrew it was really weak (like a trainer). I installed then tried a 14 x8 and a 14x6 both were better but still not much vertical. Do you think a 15 x8 will be better? It seemed to me that with the 15x4 it would not wind up as fast as it should, although I did not use a tach just going on its performance.
Troy
Ed,
I have a Goldberg Wild Stick 120 (10 lbs). I just installed the Maggie 108 and with a 15x4 Master Airscrew it was really weak (like a trainer). I installed then tried a 14 x8 and a 14x6 both were better but still not much vertical. Do you think a 15 x8 will be better? It seemed to me that with the 15x4 it would not wind up as fast as it should, although I did not use a tach just going on its performance.
Troy
If you calculate the model's theoretical air speed by using the old screw through a solid medium formula, you will see that under absolutely perfect conditions, a model spinning a 4" pitch prop at 9k rpm really isn't capable of moving fast at all. Then factor in the "slippage" of the prop moving through the air, etc., and your model is really poking along. A 4" pitch prop on a large model just doesn't provide a lot of air speed. As you know, it has a lot more potential for being a hovering prop.
I'm not saying that the proposed formula is accurate at all. There are many, many variables involved, but it does provide "amazingly accurate enough" results to demonstrate about how the model will fly.
Ed Cregger
06-16-2008, 05:39 PM
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RE: ASP vs. OS
Well I tried the 15x8. Better for sure, decent for general sport flying, still not the power I am wanting.... I guess its just a bit small for this plane. What about the new Chinese 26cc gassers? I have read mixed reviews.... I am thinking they may just about hover and should be cheap to operate. My other option is a Super Tiger G2300 (although I was going to put that in my Golberg Tiger 1.20), or I just bought a used Saito 1.25 that only has about 1/2 gallon of fuel run through it. My thought is the Saito will have about the same top end power but better for slow speed stunts. Any suggestions?
Thanks,
Troy
Thanks,
Troy
06-16-2008, 06:21 PM
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RE: ASP vs. OS
ORIGINAL: Ed Cregger
If you calculate the model's theoretical air speed by using the old screw through a solid medium formula, you will see that under absolutely perfect conditions, a model spinning a 4" pitch prop at 9k rpm really isn't capable of moving fast at all. Then factor in the "slippage" of the prop moving through the air, etc., and your model is really poking along. A 4" pitch prop on a large model just doesn't provide a lot of air speed. As you know, it has a lot more potential for being a hovering prop.
If you calculate the model's theoretical air speed by using the old screw through a solid medium formula, you will see that under absolutely perfect conditions, a model spinning a 4" pitch prop at 9k rpm really isn't capable of moving fast at all. Then factor in the "slippage" of the prop moving through the air, etc., and your model is really poking along. A 4" pitch prop on a large model just doesn't provide a lot of air speed. As you know, it has a lot more potential for being a hovering prop.
I know that the *theory* says a 4" pitch prop ought to be slower than a higher-pitched prop but in practice this is often not the case.
Just this last weekend we took a SkyRaider Mk 2 (the low-wing one commonly used for sport racing) and tried several different props on it.
The difference in speed between a 9x9, 10x7 and 12x4 was not even noticeable in fact the guy flying this plane decided to stick with the 12x4 because it was just as fast as the others but gave vastly superior vertical performance.
I think what we often forget is that the airframe is the largest dictator of maximum speed.
Since the drag increases at the square of the speed, it takes a *lot* of extra power to increase a model's speed.
With a 12x4 prop, you're moving a very large column of air and using a more efficient blade (higher aspect ratio, lower effective AOA). What's more, the bulk of the prop's wash misses the fuselage and isn't therefore wasted producing extra induced and profile drag.
Switch to something like a 10x7 or 9x9 and you end up with lower prop efficiency and a smaller/faster column of air much of which is wasted by the profile drag of the fuselage and its appendages.
I noticed the same thing with my P51 Mustang.
There was *no* difference in speed between a 12.5x10 prop and a 14x6 even though they both turned at the same RPMs.
And on a conventional high-wing trainer it gets even worse.
My own infamous "flying trainer" has had a great many engines from a TTGP42 through to an MDS61 and (presently) an SK90.
The difference in speed between all these configurations was surprisingly small and the SK90 turning a 14x8 prop hauls that plane along very, very nearly as fast as the MDS did when it was spinning a 11x7 at far higher RPMs.
Many of the guys at our club have settled on the APC 12x4 as the "standard" for .46-sized models, regardless of their type.
And visiting fliers are *constantly* amazed at how fast these planes fly often refusing to believe the prop is a 12x4 until they see for themselves.
06-16-2008, 06:51 PM
#42
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RE: ASP vs. OS
ORIGINAL: XJet
Ed, I'm sure you've seen my YouTube video of a TT46Pro turning a 12x4 prop and flying a high-wing trainer at a very respectable lick, especially considering we only run 5% nitro.
I know that the *theory* says a 4" pitch prop ought to be slower than a higher-pitched prop but in practice this is often not the case.
Just this last weekend we took a SkyRaider Mk 2 (the low-wing one commonly used for sport racing) and tried several different props on it.
The difference in speed between a 9x9, 10x7 and 12x4 was not even noticeable in fact the guy flying this plane decided to stick with the 12x4 because it was just as fast as the others but gave vastly superior vertical performance.
I think what we often forget is that the airframe is the largest dictator of maximum speed.
Since the drag increases at the square of the speed, it takes a *lot* of extra power to increase a model's speed.
With a 12x4 prop, you're moving a very large column of air and using a more efficient blade (higher aspect ratio, lower effective AOA). What's more, the bulk of the prop's wash misses the fuselage and isn't therefore wasted producing extra induced and profile drag.
Switch to something like a 10x7 or 9x9 and you end up with lower prop efficiency and a smaller/faster column of air much of which is wasted by the profile drag of the fuselage and its appendages.
I noticed the same thing with my P51 Mustang.
There was *no* difference in speed between a 12.5x10 prop and a 14x6 even though they both turned at the same RPMs.
And on a conventional high-wing trainer it gets even worse.
My own infamous "flying trainer" has had a great many engines from a TTGP42 through to an MDS61 and (presently) an SK90.
The difference in speed between all these configurations was surprisingly small and the SK90 turning a 14x8 prop hauls that plane along very, very nearly as fast as the MDS did when it was spinning a 11x7 at far higher RPMs.
Many of the guys at our club have settled on the APC 12x4 as the "standard" for .46-sized models, regardless of their type.
And visiting fliers are *constantly* amazed at how fast these planes fly often refusing to believe the prop is a 12x4 until they see for themselves.
ORIGINAL: Ed Cregger
If you calculate the model's theoretical air speed by using the old screw through a solid medium formula, you will see that under absolutely perfect conditions, a model spinning a 4" pitch prop at 9k rpm really isn't capable of moving fast at all. Then factor in the "slippage" of the prop moving through the air, etc., and your model is really poking along. A 4" pitch prop on a large model just doesn't provide a lot of air speed. As you know, it has a lot more potential for being a hovering prop.
If you calculate the model's theoretical air speed by using the old screw through a solid medium formula, you will see that under absolutely perfect conditions, a model spinning a 4" pitch prop at 9k rpm really isn't capable of moving fast at all. Then factor in the "slippage" of the prop moving through the air, etc., and your model is really poking along. A 4" pitch prop on a large model just doesn't provide a lot of air speed. As you know, it has a lot more potential for being a hovering prop.
I know that the *theory* says a 4" pitch prop ought to be slower than a higher-pitched prop but in practice this is often not the case.
Just this last weekend we took a SkyRaider Mk 2 (the low-wing one commonly used for sport racing) and tried several different props on it.
The difference in speed between a 9x9, 10x7 and 12x4 was not even noticeable in fact the guy flying this plane decided to stick with the 12x4 because it was just as fast as the others but gave vastly superior vertical performance.
I think what we often forget is that the airframe is the largest dictator of maximum speed.
Since the drag increases at the square of the speed, it takes a *lot* of extra power to increase a model's speed.
With a 12x4 prop, you're moving a very large column of air and using a more efficient blade (higher aspect ratio, lower effective AOA). What's more, the bulk of the prop's wash misses the fuselage and isn't therefore wasted producing extra induced and profile drag.
Switch to something like a 10x7 or 9x9 and you end up with lower prop efficiency and a smaller/faster column of air much of which is wasted by the profile drag of the fuselage and its appendages.
I noticed the same thing with my P51 Mustang.
There was *no* difference in speed between a 12.5x10 prop and a 14x6 even though they both turned at the same RPMs.
And on a conventional high-wing trainer it gets even worse.
My own infamous "flying trainer" has had a great many engines from a TTGP42 through to an MDS61 and (presently) an SK90.
The difference in speed between all these configurations was surprisingly small and the SK90 turning a 14x8 prop hauls that plane along very, very nearly as fast as the MDS did when it was spinning a 11x7 at far higher RPMs.
Many of the guys at our club have settled on the APC 12x4 as the "standard" for .46-sized models, regardless of their type.
And visiting fliers are *constantly* amazed at how fast these planes fly often refusing to believe the prop is a 12x4 until they see for themselves.
-
I have experience with 4" pitch props. Not theoretical, but down in the dirty, hot sweaty days of flying them. My souped-up GP Trainer Forty powered by an Enya .45 CX and using a 10x6 prop used to generate questions such as, "What kind of .60 are you using in that plane?" This particular model was modified to fly in non serious club fun fly events. It flew great, and, with the 10x6 prop, was also a fair contender in pre-novice, Sportsman type of pattern contests. This was in 1992.
I then became interested in the then emerging (in my area, NJ, USA) competition fun fly events. Not having a model designed for that event, but wanting to experiment, I bought a few Rev-Up 11x4 wood props and a few 11x4 APC composite props. The top speed dropped a good thirty percent (eyeball calculation), but the takeoff run shortened to practically zero. My GP Trainer Forty would hover with the 10x6 at full throttle. With the 11x4, it would climb ever so slightly out of the hover at full throttle.
Being an old fart, I tend to think of models flying in the old sport flying and pattern ways as being normal. When using the 11x4 props for normal sport flying, I always felt as though I needed to shift out of low gear. The model just didn't have its old pizazz for sweeping pattern maneuvers. When flying the model in close to the ground low speed maneuvers, the 11x4 was perfect.
A lot really depends upon one's perspective, I suppose.
Ed Cregger
06-28-2008, 12:18 PM
#43
RE: ASP vs. OS
Just to make matters more complicated. A large 4" prop is not the same as a small 4" prop. The small 4" prop has a higher angle because of its small diameter. Many props, especially smaller ones, are overpitched and will run faster than the calculated RPM times pitch, at least with a small sleek plane.
