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Stoopid IRIS P-40 questions...maybe

WarHorse47

WarHorse47

SOH-CM-2024
From the pilot's seat what direction are the props supposed to rotate for the Allison and Merlin engine models? Are they the same?

In looking at the various IRIS models the prop looks like they should all rotate counterclockwise, yet I'm seeing that only with the F & L models.

Just curious :salute:

Thanks

--WH
 
Some models are rotating backward relative to the prop pitch. You will have to look at the pitch on each model, crank it over and if it's backward reverse it in the cfg file.
 
This was a topic last month and one of our members posted this fix. I can't remember who right now, but it solved the problem. I think that this fix applies to the E, F and L models.

Go to the aircraft.cfg file and change the rotation to: -1

[propeller]
number_of_propellers = 1;
rotation = -1
propeller.0 = 4.8, 0.0, 1.0
 
Question was asked about prop rotation direction as viewed from the pilot seat, so that's how I answered this. In actuality, being a long time mechanic, Props and engines rotation directions are always refered to from standing in front of them. These are the only items on a vehicle refered to this way. Why? Because you look at a clock from in front of it! Everything else is refered to from the operater's seat.


When David first made this model, he had all the props turning CW, as most English props turn. I told him that as far as I knew, the P-40 never had a left rotating prop, but he insisted that since the models he was modeling were Aussie models at the time, he wanted them to turn CW. So he modeled the props with reverse twist. However, he did post the visible rotation direction fix in the .cfg. However, I can find nothing that suggests the P-40 ever had a CW rotating prop. The Merlins used in the F/L models were Packard built American engines, turning CCW.

However, as I mentioned, even for left hand rotation, the twist in the prop blades is wrong. Look at a stationary prop. The twist is max at the center/hub area, least at the tip. This is because as a solid object with length is rotated, the outside tips are traveling farther/faster than the center area. Therefor, the tip is moving more air. So, to move the same distance as the center, the twist /pitch must be reduced/flattened from center to tip. Otherwise, the blade will twist itself forward, or if made of wood, will actually break the prop. Also, the horsepower required to turn the prop would be exponential to that required by a proper twist.

If any of you plastic modelers out there have any of Accurate Miniature's early P-51 Mustang models, the Allison powered ones with the 3 blade props will notice that that kit also has this problem. I mentioned this to them at one of the big model shows, but they said they were not going to fix them. There was a resin fixed prop blades kit/package available a long time ago. 3 individual blades with proper twist. I got one set, but have never seen it again.
 
I simply can't stand to view the prop from outside trying to push the plane backward. If this means running the engine backward to get the prop right so be it. That's acceptable for an otherwise nice freeware model.
 
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