O.S. MAX 90 info
09-24-2008, 08:18 PM
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O.S. MAX 90 info
HI,
I have a old OS MAX 90 , that is like new. I want to get it going and put it on a plane I picked up. Its a Zero with flaps and weights 5.5 lbs built, with two sevros and two retracts. This weight is with out motor, radio gear. If I could get the HP and what prop it takes, that would help. The guys at the field where I bought it said a 90 would be underpowered, but at that weight I wonder?
thanks
sticks
I have a old OS MAX 90 , that is like new. I want to get it going and put it on a plane I picked up. Its a Zero with flaps and weights 5.5 lbs built, with two sevros and two retracts. This weight is with out motor, radio gear. If I could get the HP and what prop it takes, that would help. The guys at the field where I bought it said a 90 would be underpowered, but at that weight I wonder?
thanks
sticks
09-25-2008, 09:58 AM
#3
Senior Member
RE: O.S. MAX 90 info
5.5 lbs built … weight is with out motor, radio gear
OS MAX 90 – about 26 oz.
Battery – no more than 4 oz.
Other gear estimated at max 6 oz.
Total 7 lbs. 12 oz.
I fly a King Kobra at 7.5 lbs with an OS 61 and consider 11 lbs to be approaching the limit of a 90 engine.
Bill
OS MAX 90 – about 26 oz.
Battery – no more than 4 oz.
Other gear estimated at max 6 oz.
Total 7 lbs. 12 oz.
I fly a King Kobra at 7.5 lbs with an OS 61 and consider 11 lbs to be approaching the limit of a 90 engine.
Bill
09-25-2008, 11:51 AM
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RE: O.S. MAX 90 info
Ya,
its a old 2 cycle, sorry forgot to bring that up. I just weighted the motor and yours right on with the weight. To me it seems like that 90 should fly it, though it may not be a screemer. I just want to try the plane , before I put money into another motor and a lot of work this winter.
Any ideas on props?????
thanks
sticks
its a old 2 cycle, sorry forgot to bring that up. I just weighted the motor and yours right on with the weight. To me it seems like that 90 should fly it, though it may not be a screemer. I just want to try the plane , before I put money into another motor and a lot of work this winter.
Any ideas on props?????
thanks
sticks
09-25-2008, 08:42 PM
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RE: O.S. MAX 90 info
thanks aerowoof,
that helps, I amd ordering a perry carb for it. Can't find the high speed needle for it, plus I may get more power with the perry carb. I have had great luck with perry carbs.
I have it in my head to get this flying this fall.
[img][/img]
that helps, I amd ordering a perry carb for it. Can't find the high speed needle for it, plus I may get more power with the perry carb. I have had great luck with perry carbs.
I have it in my head to get this flying this fall.
[img][/img]
09-26-2008, 03:27 PM
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RE: O.S. MAX 90 info
I ran the OS .90 today, with a master airscrew 13x6 and got 11k rpm's. I used a caster blend , 10% fuel.
Seems like someone sugested a 12x8 can't remember who or when , but they thought it should turn about 12 to 13 K with the 12x8. I may get a couple of APC's and try them, it would be nice to get into the 12 to 13 K range.
sticks
Seems like someone sugested a 12x8 can't remember who or when , but they thought it should turn about 12 to 13 K with the 12x8. I may get a couple of APC's and try them, it would be nice to get into the 12 to 13 K range.
sticks
09-27-2008, 08:18 AM
#9
Senior Member
RE: O.S. MAX 90 info
My OS91FXs all perform better at less rpms than what you're seeing. I have no idea if older versions are any different than the 91 sold today, but you really don't need rpms as much in the larger sized engines.
My P47, Corsair, and Sukhoi's all have OS91s in them and all seem to run strongest with a range of props that turn in the 10Ks on the ground.
I've tested 12", 13", 14", and 15"s and a couple of 3-bladers. The 12"s really did not perform. They did what props do that have too little "fan area" for the engine's horsepower.
The 13x6 was a loser. It didn't seem to have any purchase on the air. Like tires with no grip. The 13x8 had better grip but not compared to the larger diameters.
The 14x6 and 14x8 had grip and tested out the best. The 6pitch was better. The 8pitch would not idle down enough more than the 6 to let the airplane slow enough on idle on approach. I got 10,900 on the ground from the 14x6 that seemed the best of the 14x6s I tested. The best of that group was an Evolution. The worst in the air was an APC that didn't fly like any of the other 14x6s. I'm guessing it really had more like a 5" pitch. I didn't have a 14x7 or 14x8 APC to test, but it's not always a given that when one pitch spec is wrong, the others will be wrong in the same way too. I only had one brand of 14x8 to test. And with my engines, since 14 seemed to be the sweet spot diameter, I'm always looking for a 14x7 or a different 14x8 to try.
The 15x6 I had turned the same ground rpm as the 13x8 and only 500 less than the 14x6 had, but in the air it wouldn't unload to any degree. I'm guessing there was just too much fan for the horsepower to pull my 7-8 lb planes.
My P47, Corsair, and Sukhoi's all have OS91s in them and all seem to run strongest with a range of props that turn in the 10Ks on the ground.
I've tested 12", 13", 14", and 15"s and a couple of 3-bladers. The 12"s really did not perform. They did what props do that have too little "fan area" for the engine's horsepower.
The 13x6 was a loser. It didn't seem to have any purchase on the air. Like tires with no grip. The 13x8 had better grip but not compared to the larger diameters.
The 14x6 and 14x8 had grip and tested out the best. The 6pitch was better. The 8pitch would not idle down enough more than the 6 to let the airplane slow enough on idle on approach. I got 10,900 on the ground from the 14x6 that seemed the best of the 14x6s I tested. The best of that group was an Evolution. The worst in the air was an APC that didn't fly like any of the other 14x6s. I'm guessing it really had more like a 5" pitch. I didn't have a 14x7 or 14x8 APC to test, but it's not always a given that when one pitch spec is wrong, the others will be wrong in the same way too. I only had one brand of 14x8 to test. And with my engines, since 14 seemed to be the sweet spot diameter, I'm always looking for a 14x7 or a different 14x8 to try.
The 15x6 I had turned the same ground rpm as the 13x8 and only 500 less than the 14x6 had, but in the air it wouldn't unload to any degree. I'm guessing there was just too much fan for the horsepower to pull my 7-8 lb planes.
09-27-2008, 08:33 AM
#10
Senior Member
RE: O.S. MAX 90 info
Keep in mind that the A6M flew behind a 3-blade most of it's life.
And there is a 3-blade that works excellently with my 91s and the 7-8lb models they pull around. But don't let the DxP numbers on it keep you from trying it. I've found that the Master Airscrew 14x7x3 works excellently well in spite of the fact that it's specs fly in the face of all our modelers conventional wisdom. I have no idea (yet) why the sucker works like it does because the rule of thumb for selecting a 3 blade would definitely NOT point this prop out for a 91 that likes to turn 14x6 2-bladers.
See the pictures............
That's how I fly those two day in and day out. Both have OS91FXs and both fly great with the MA 14x7x3s you see in the pictures. They perform great with Evolution 14x6 2-blades but they actually fly a touch better on real hot days with the MA 3-blader. Since the 3-blader looks better, there is no contest which prop stays on the airplanes.
And there is a 3-blade that works excellently with my 91s and the 7-8lb models they pull around. But don't let the DxP numbers on it keep you from trying it. I've found that the Master Airscrew 14x7x3 works excellently well in spite of the fact that it's specs fly in the face of all our modelers conventional wisdom. I have no idea (yet) why the sucker works like it does because the rule of thumb for selecting a 3 blade would definitely NOT point this prop out for a 91 that likes to turn 14x6 2-bladers.
See the pictures............
That's how I fly those two day in and day out. Both have OS91FXs and both fly great with the MA 14x7x3s you see in the pictures. They perform great with Evolution 14x6 2-blades but they actually fly a touch better on real hot days with the MA 3-blader. Since the 3-blader looks better, there is no contest which prop stays on the airplanes.
09-28-2008, 06:42 PM
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RE: O.S. MAX 90 info
Hi,
I found a ziner 12x8 and it did not do much, I got 11.5k RPM's but did not seem to pull. The 13x6 pulled really well, it would pull a 8 lb. plane around with no problem. I have flaps set up and plan to use them.
but I will get the ones you sugested and try them. I got time, its taking more time to get the plane air worthy than I thought it would.
sticks
I found a ziner 12x8 and it did not do much, I got 11.5k RPM's but did not seem to pull. The 13x6 pulled really well, it would pull a 8 lb. plane around with no problem. I have flaps set up and plan to use them.
but I will get the ones you sugested and try them. I got time, its taking more time to get the plane air worthy than I thought it would.
sticks
10-03-2008, 07:45 PM
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RE: O.S. MAX 90 info
ORIGINAL: da Rock
My OS91FXs all perform better at less rpms than what you're seeing. I have no idea if older versions are any different than the 91 sold today, but you really don't need rpms as much in the larger sized engines.
My P47, Corsair, and Sukhoi's all have OS91s in them and all seem to run strongest with a range of props that turn in the 10Ks on the ground.
I've tested 12", 13", 14", and 15"s and a couple of 3-bladers. The 12"s really did not perform. They did what props do that have too little "fan area" for the engine's horsepower.
The 13x6 was a loser. It didn't seem to have any purchase on the air. Like tires with no grip. The 13x8 had better grip but not compared to the larger diameters.
The 14x6 and 14x8 had grip and tested out the best. The 6pitch was better. The 8pitch would not idle down enough more than the 6 to let the airplane slow enough on idle on approach. I got 10,900 on the ground from the 14x6 that seemed the best of the 14x6s I tested. The best of that group was an Evolution. The worst in the air was an APC that didn't fly like any of the other 14x6s. I'm guessing it really had more like a 5" pitch. I didn't have a 14x7 or 14x8 APC to test, but it's not always a given that when one pitch spec is wrong, the others will be wrong in the same way too. I only had one brand of 14x8 to test. And with my engines, since 14 seemed to be the sweet spot diameter, I'm always looking for a 14x7 or a different 14x8 to try.
The 15x6 I had turned the same ground rpm as the 13x8 and only 500 less than the 14x6 had, but in the air it wouldn't unload to any degree. I'm guessing there was just too much fan for the horsepower to pull my 7-8 lb planes.
My OS91FXs all perform better at less rpms than what you're seeing. I have no idea if older versions are any different than the 91 sold today, but you really don't need rpms as much in the larger sized engines.
My P47, Corsair, and Sukhoi's all have OS91s in them and all seem to run strongest with a range of props that turn in the 10Ks on the ground.
I've tested 12", 13", 14", and 15"s and a couple of 3-bladers. The 12"s really did not perform. They did what props do that have too little "fan area" for the engine's horsepower.
The 13x6 was a loser. It didn't seem to have any purchase on the air. Like tires with no grip. The 13x8 had better grip but not compared to the larger diameters.
The 14x6 and 14x8 had grip and tested out the best. The 6pitch was better. The 8pitch would not idle down enough more than the 6 to let the airplane slow enough on idle on approach. I got 10,900 on the ground from the 14x6 that seemed the best of the 14x6s I tested. The best of that group was an Evolution. The worst in the air was an APC that didn't fly like any of the other 14x6s. I'm guessing it really had more like a 5" pitch. I didn't have a 14x7 or 14x8 APC to test, but it's not always a given that when one pitch spec is wrong, the others will be wrong in the same way too. I only had one brand of 14x8 to test. And with my engines, since 14 seemed to be the sweet spot diameter, I'm always looking for a 14x7 or a different 14x8 to try.
The 15x6 I had turned the same ground rpm as the 13x8 and only 500 less than the 14x6 had, but in the air it wouldn't unload to any degree. I'm guessing there was just too much fan for the horsepower to pull my 7-8 lb planes.
I finaly got some new props and you were right about the 14x7, three blade. I was surprised the 14x7 turned 9,200 RPM, the 13x6 three blade only turned 10.7K rpm's. Thats not much of a drop for the increase in blade and pitch.
I took a fish scale and tied it to the tail. I would take a reading with the motor at 200 rpm's below peak . I tried each prop with 10% and 15% nitro and the 14x7 pulled 9 lbs on the scale. The 13x8 three blade came in second with 7.5 lbs force.
Now before anyone jumps in and tells me this isn't the best way , or my readings don't mean anything. I was just checking to see how one prop pulled against another, and I think I have done that.
I know the 14x7 pulls harder than any of the others, and thats all I was looking for. The plane came in a little heaver than I thought , its around 8.5 lbs but should fly with this much pulling power.
Thanks again, I am now ready to try the Zero!!!! Should do it monday if I get a chance.
sticks
10-08-2008, 04:45 PM
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RE: O.S. MAX 90 info
I'm back, I flew the zero and it did allright. Did not spend a lot of time in the air. It was windy and I did not have much time, but the 14x7 three blade prop at 9K did a nice job. I think it got off the ground in about 50 feet.
thanks for all the help.
sticks
thanks for all the help.
sticks
