O.S. 40 LA Performance
08-25-2003, 05:33 PM
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O.S. 40 LA Performance
I was very impressed by the response to my question regarding the O.S. 40 LA bypass porting. Of all the suggestions and info, I feel that Jim's gave me the best advice to run the engine as is.
Now I would like to raise another issue. That is of prop selection to get the maximum power transfer into usable thrust with ten percent nitro fuel.
I am referring to a O.S. 40 LA in a 4 pound Great Planes "Uproar".
So far, I have flown the model with a Master Airscrew 10-6 and APC 10-5 props. (Better results with the Master Airscrew 10-6). I live and fly in Albuquerque NM where the altitude is around 5000 feet above sea level.
Rather than trying every other possible combinations, I would welcome any suggestions on other prop diameter/pitch that could result in a little better high-end performance.
Dave K
Now I would like to raise another issue. That is of prop selection to get the maximum power transfer into usable thrust with ten percent nitro fuel.
I am referring to a O.S. 40 LA in a 4 pound Great Planes "Uproar".
So far, I have flown the model with a Master Airscrew 10-6 and APC 10-5 props. (Better results with the Master Airscrew 10-6). I live and fly in Albuquerque NM where the altitude is around 5000 feet above sea level.
Rather than trying every other possible combinations, I would welcome any suggestions on other prop diameter/pitch that could result in a little better high-end performance.
Dave K
08-25-2003, 06:38 PM
#4
O.S. 40 LA Performance
Dave,
The which prop issue is variable and often to one's feelings when flying the model because individuals have different flying habits even with the same kind of plane.
You might try the 11-5, 11-4. The 12" props are just too much even using the 12.25 - 3.75 APC. You will drop a 100 rpm with the 11-4 so it might be your best bet? Stay with the same brand of prop as much as possible. I didn't mention the 10's because it looks like you've already been there.
Generally, the higher diameter - lower pitch props give the best vertical performance.
The prop will have to take the most advantage of the engine's power charateristics.
It's hard to beat the 10-6 for sport flying though.
Enjoy,
Jim
The which prop issue is variable and often to one's feelings when flying the model because individuals have different flying habits even with the same kind of plane.
You might try the 11-5, 11-4. The 12" props are just too much even using the 12.25 - 3.75 APC. You will drop a 100 rpm with the 11-4 so it might be your best bet? Stay with the same brand of prop as much as possible. I didn't mention the 10's because it looks like you've already been there.
Generally, the higher diameter - lower pitch props give the best vertical performance.
The prop will have to take the most advantage of the engine's power charateristics.
It's hard to beat the 10-6 for sport flying though.
Enjoy,
Jim
08-26-2003, 08:42 PM
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O.S. 40 LA Performance
You wanna get serious, here ya go
http://www.rcfaq.com/rpmstats/rpmbycc1.htm
High pitch, smaller diameter =more speed.
Lower pitch, larger diameter= more pulling power.
The only way to find out is to buy a bunch of props and experiment!
Max
http://www.rcfaq.com/rpmstats/rpmbycc1.htm
High pitch, smaller diameter =more speed.
Lower pitch, larger diameter= more pulling power.
The only way to find out is to buy a bunch of props and experiment!
Max
08-29-2003, 01:07 AM
#9
O.S. 40 LA Performance
[QUOTE]Originally posted by Maxtenet
[B]I find it absurd and a contradiction in terms to use the words "O.S. LA .40" and "performance" in the same breath!
I have to agree with Maxtenet on this one but there is light in the tunnel. I also fly here in Albuquerque for several years. The altitude here is not kind to any engine but the .40 la seems to cath alot of heat.
*It will not pull a normal size .40 plane well at all. Because of this fact, does not mean it is not a good running engine because it is.
We have about a 17% loss in power here from engine performance to speed. 3% per 1000ft and this has been verfied.
*This is why most of us here to include me overpower our planes here to achieve decent performance. If your plane weighs in a 4lbs, then the LA should be pulling it okay with the 10/6. Going to an 11inch is not going to help at all. This is the best your going to get with what you have to work with.
*I'm not sure what your next plane will be but consider this. if your going to hang around in the .40-60size for a while, get a good engine that you can switch over to save you some money. You can install a nice .60 in most .40 size planes. OS 61fx and TT61pro are identical in performance but the TT is a bit cheaper. *Also some people like myself will do this. If i am going to use a .60, then I buy a .90 since they are the same size anyways.
Come on out to the airshow this weekend
[B]I find it absurd and a contradiction in terms to use the words "O.S. LA .40" and "performance" in the same breath!
I have to agree with Maxtenet on this one but there is light in the tunnel. I also fly here in Albuquerque for several years. The altitude here is not kind to any engine but the .40 la seems to cath alot of heat.
*It will not pull a normal size .40 plane well at all. Because of this fact, does not mean it is not a good running engine because it is.
We have about a 17% loss in power here from engine performance to speed. 3% per 1000ft and this has been verfied.
*This is why most of us here to include me overpower our planes here to achieve decent performance. If your plane weighs in a 4lbs, then the LA should be pulling it okay with the 10/6. Going to an 11inch is not going to help at all. This is the best your going to get with what you have to work with.
*I'm not sure what your next plane will be but consider this. if your going to hang around in the .40-60size for a while, get a good engine that you can switch over to save you some money. You can install a nice .60 in most .40 size planes. OS 61fx and TT61pro are identical in performance but the TT is a bit cheaper. *Also some people like myself will do this. If i am going to use a .60, then I buy a .90 since they are the same size anyways.
Come on out to the airshow this weekend
08-29-2003, 10:46 PM
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O.S. 40 LA Performance
Good advice Cyclic.
The .40 LA is good for use in trainers, thats about it.
If your flying at altitude, put a .50 sized 2 stroke in 40 sized models and .90's in .60 sized models.
Try a Super Tigre G51 in the .50 sized class and either an OS or Thunder Tiger. 90 or a Super Tigre.91 in the .90 class.
As for props on the LA40, a 10 x 6 is about it. The performance band of this engine is small and its not really worth spending the $$ on different props, to try and get power out of an engine that doesn't really have any.
The .40 LA is good for use in trainers, thats about it.
If your flying at altitude, put a .50 sized 2 stroke in 40 sized models and .90's in .60 sized models.
Try a Super Tigre G51 in the .50 sized class and either an OS or Thunder Tiger. 90 or a Super Tigre.91 in the .90 class.
As for props on the LA40, a 10 x 6 is about it. The performance band of this engine is small and its not really worth spending the $$ on different props, to try and get power out of an engine that doesn't really have any.
08-30-2003, 02:18 AM
#11
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O.S. 40 LA Performance
The 40 and 46 La are Schnurle motors without the boost ports cut into them. As such they are really not highly tuned motors. Add to that the carbs are really on the small size and air bleed to boot and you have a recipe for mild performance which is what the motor was designed for.
Yes you can play with props but the easiest is to change the carb and go to a slightly larger one. Next put another head gasket in and up the nitro content to about 30%. Will that trun it into a world beater,NO, but the performance will be enhanced at a cost that is not worth the effort.
Not knocking the LA it is a minimum motor designed for mild performance, however. if you want more then best get a bigger gun
Yes you can play with props but the easiest is to change the carb and go to a slightly larger one. Next put another head gasket in and up the nitro content to about 30%. Will that trun it into a world beater,NO, but the performance will be enhanced at a cost that is not worth the effort.
Not knocking the LA it is a minimum motor designed for mild performance, however. if you want more then best get a bigger gun
