3 or 4 blade propellers?

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rcristi2271
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3 or 4 blade propellers?

Post by rcristi2271 » 17 May 2004 14:44

Which are the main differences between these types of propellers? I always asked myself why Germans used almost always 3 blade propellers (just one exception: Heinkel He 177) compared with Allies who widely used 4 blade propellers.

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Chris

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Hadrian
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Post by Hadrian » 17 May 2004 20:49

It`s the surface square meters you need for the propeler to be eficient at a certain power of the engine.
You can increase the diameter or the number of blades.
Too big diameter, the propeler requests high undercarriage not to touch the ground, and the speed at the margin of the blade becomes supersonic(destroys airflow, vibrations). Americans had engines more powerful at last series of proprller fighters than germans (but germans had jet fighters :wink: ). Its the same with elicopters today, from two blades (Cobra) to seven (russianMi-26)

MadderCat
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Post by MadderCat » 18 May 2004 18:43

don't forget that the german 3-blade props on late fighters were much more
wider than in beginning of WW2

MadderCat

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bryson109
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Post by bryson109 » 18 May 2004 19:27

btw....The Bf 109 K-16 had a four blade propeller planned. the He 177 was a four engine bomber with two propellers, each propeller had to transfer the power from two engines.

Also maddercat is right the late war German propeller were wider than Allied propellers.

Tony Williams
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Post by Tony Williams » 18 May 2004 21:19

Don't forget that the German fighters had cowling-mounted guns synchronised to fire through the propeller disk. The more blades, the trickier the technical problem.

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Cantankerous
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Re: 3 or 4 blade propellers?

Post by Cantankerous » 13 Jun 2022 16:32

Even though this thread is almost 20 years old and it may therefore be tempting not to post here, I should note that the Junkers Ju 288 prototype tactical bomber had Junkers Jumo 222 engines driving four-bladed propellers, and that the one Heinkel He 177B prototype was used as a testbed for the Jumo 222 because Heinkel floated the option of using the Jumo 222 for the Heinkel He 277 long-range maritime strike aircraft. The Jumo 222, however, was a technological failure due to cooling problems.

ShindenKai
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Re: 3 or 4 blade propellers?

Post by ShindenKai » 15 Jun 2022 03:25

Its not just the efficiency of the propellers themselves but the constant-speed/prop pitch control units. There just wasn’t physically enough space to have the prop pitch controls AND a cannon firing through the prop hub.

ThatZenoGuy
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Re: 3 or 4 blade propellers?

Post by ThatZenoGuy » 19 Jun 2022 16:48

https://www.youtube.com/watch?v=EKR-Obdq8_E

Greg did a really neato video on the topic, long video, but he's a great youtuber.

ShindenKai
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Re: 3 or 4 blade propellers?

Post by ShindenKai » 27 Jun 2022 18:17

ThatZenoGuy wrote:
19 Jun 2022 16:48
https://www.youtube.com/watch?v=EKR-Obdq8_E

Greg did a really neato video on the topic, long video, but he's a great youtuber.
Yes, Greg does an excellent job!

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