|
RE: 3 blade prop...help!
ORIGINAL: Sport_Pilot Dar, Everything is correct till the fifth paragraph. After that everything is confused. [:o] Beginning with the maximized VE. The VE goes down in all engines from 0 RPM and up. At 0 RPM (I guessed you meant very low...), the VE is very low. A two-stroke engine actually captures and compresses about 60-70% of its swept cylinder displacement, from the exhaust port and above. For a hot, racing engine, with 180% exhaust timing it is 50% - a VE of just 50%. With the engine running and the exhaust and intake charges flowing with some inertia, VE becomes higher. With a tuned exhaust system on boost, it becomes still higher; over 100% in many cases. VE higher than 100%, means that every cycle, the engine 'gulps up' air greater in volume than its swept cylinder displacement. In the MAN 05/03 Dave Gierke engine shootout, each engine achieved its peak torque somewhere between 9,250 and 10,800 RPM. Peak torque is achieve at about the same RPM as peak VE, with minute only minute differences, which may result from differing combustion efficiency. |
RE: 3 blade prop...help!
...Double post...
---Removed--- |
RE: 3 blade prop...help!
ORIGINAL: britbrat ORIGINAL: Flyboy Dave The reason is I have experience with similar type plane, with similar power. I have BB Magnum 40's, that are about the same power wise as the LA 46's. I had two twins, and have accomplished all the experimentation. If you are propping them with 11-7's, they will be turning ~ 11,000 RPM and will in fact have outputs similar to the LA 46, making just under 0.7 HP at that RPM -- just about right where the 46 LA is as well. However the LA falls off after 13,500 & ~1HP (with a 10-6 APC prop) those props. You cannot take a false assumption and use it in a debate, and expect to have a reasonably correct result. " If " the La 46 will turn 10-6 APC at 13.5 the performance would be right on par with the Magnum 40's, if you put the MAS 10-7's on them.... ....just like I said: I have experience with similar type plane, with similar power. I have BB Magnum 40's, that are about the same power wise as the LA 46's. BTW, an 11-7 is a 60 size prop. Guess what prop a Jett 90L runs? ....an 11-8 APC. Your comparison, and argument, using 11-7's is very funny. :D FBD. :D |
RE: 3 blade prop...help!
ORIGINAL: Flyboy Dave ORIGINAL: britbrat ORIGINAL: Flyboy Dave The reason is I have experience with similar type plane, with similar power. I have BB Magnum 40's, that are about the same power wise as the LA 46's. I had two twins, and have accomplished all the experimentation. If you are propping them with 11-7's, they will be turning ~ 11,000 RPM and will in fact have outputs similar to the LA 46, making just under 0.7 HP at that RPM -- just about right where the 46 LA is as well. However the LA falls off after 13,500 & ~1HP (with a 10-6 APC prop) those props. You cannot take a false assumption and use it in a debate, and expect to have a reasonably correct result. " If " the La 46 will turn 10-6 APC at 13.5 the performance would be right on par with the Magnum 40's, if you put the MAS 10-7's on them.... ....just like I said: I have experience with similar type plane, with similar power. I have BB Magnum 40's, that are about the same power wise as the LA 46's. BTW, an 11-7 is a 60 size prop. Guess what prop a Jett 90L runs? ....an 11-8 APC. Your comparison, and argument, using 11-7's is very funny. :D FBD. :D I selected the 11-7 size because that is the prop size where the the 46 LA and the Magnum XL 40 are equal (more or less) in HP, with either one turning an 11-7 APC @ just under 11,000 RPM. Your Magnums are apparently quite outstanding @ 14,000 RPM with a 10-7. My testing has the Magnum at 12,200 RPM & Dave Geirke shows it at 12,100 RPM with an APC 10-7. Some of the difference is attributable to the MAS vs APC prop-fit, but 1,800 RPM is a long way away. Even with a 10-7, the Magnum comfortably out-powers the 46 LA -- ~ 800 RPM & 0.1 HP (0.7HP vs 0.8 HP), more than 14% with my test data & 2,400 RPM & 0.3 HP, (nearly 43%) using your 14,000 RPM Magnum data. As I said in my post, a 46 LA with a 10-6, is similar in power to a Magnum 40 with a 10-7. That is using my own test data -- with your data they aren't even close. In either case, that is NOT "about the same powerwise as the 46 LA". |
RE: 3 blade prop...help!
Britbrat As I said in my post, a 46 LA with a 10-6, is similar in power to a Magnum 40 with a 10-7. That is using my own test data -- with your data they aren't even close. In either case, that is NOT "about the same powerwise as the 46 LA". |
RE: 3 blade prop...help!
Some things is more equal than others [sm=bananahead.gif]
At low revs the Magnum & LA are about equal, but if both are permitted to develop max power, they ain't even in the same world. [X(] |
RE: 3 blade prop...help!
BOYS BOYS stop it!!! I always wanted to say that. Some of you slide rule boys think 50 RPM is a big thing. Britbrat your in CANADA your tach is froze and sluggish. I'm with FLYBOY The Mag 40 and OS 46 LA are almost even. By the way somewhere in OS specs on the net is a misprint on prop sizes.
|
RE: 3 blade prop...help!
Hey -- boyz is boyz :) My tach is biggerr than his'n [>:]
What the hell were we discussing? [&:] What ever it was, he was wrong[:'(] How would you know about slide-rules? I thought that I was the only one left -- but I probably can't remember how to use one very well anymore. I think I know where my ivory-laminated 20" KE slide rule is packed away. Lemme see -- C-scale & D-scale ---- |
RE: 3 blade prop...help!
ORIGINAL: Flyboy Dave . . . . Another point you and others are missing is the fact that two cycle engines will continue to make increased horsepower as the rpm increases....there is no cut off point. . . . . Any two cycle engine will produce it's maximum HP at the Maximum RPM you can get it to turn. In other words, the engine is producing more HP at 16,000 rpm, than it is at 13, 500. . . . . There is no "set point" for horsepower production on a two cycle engine, that's why they are so successfull in racing applications.... ....the more RPM's you can "get it to turn", the more horsepower it will produce. Plain and simple. ;) FBD. :D Britbrat, Dar and others, With a unique physics model like this, reasoned arguments based on conventional learning and practical experience are not valid. It's just not worth the battle. Logical debate does not live at this address. |
RE: 3 blade prop...help!
Just when ya though it was safe ta git back in the water -- the universe changes. [:@] You mean that thermodynamics doesn't work any more? Damn -- I hate it when it does that. [:'(]
|
RE: 3 blade prop...help!
This thread has stalled out.
Everyone interested has presented their point. There's too much finger pointing going on. I'm LOCKING UP the thread. My apologies to those of you who didn't get the LAST WORD. Jim |
| All times are GMT -8. The time now is 08:47 PM. |
Copyright © 2026 MH Sub I, LLC dba Internet Brands. All rights reserved. Use of this site indicates your consent to the Terms of Use.