Force or Torque in Engine (1 Viewer)

[Ted griffin]

Hello all
Greetings
I have a question but didn't find a clear answer yet about engine HP for all old aircraft. As known, most of the engine are more than 1,000 hp.
My question is, do we need this high HP to get high RPM ? or force? Or torque?
If yes, what is the startup ideal RPM for the propeller ? I have heard abou 1.3 RPM which is low when we camper it with can engine.
If the the high HP is to convert the force into torque, in this case, mechanically the speed will be reduced as you know.
Please advise me and sorry if i confused you

 

[cvairwerks]

You need both the HP and the RPM's to get the prop to the desired speed to achieve the needed thrust. The actual HP and RPM's required will vary based on the prop diameter, the particular blade profile, blade pitch angle and the tip design. Ideally, the RPM's are set to keep the blade tip speed below supersonic for efficiency and noise control.
A T-6 on takeoff will have the prop tips well into the supersonic region, but the pilot reduces the blade pitch and the needed RPM's very quickly after takeoff, as not as much power is need to drive the prop at that point. It's a huge balancing game with some black art to it.

 

[Ted griffin]

You need both the HP and the RPM's to get the prop to the desired speed to achieve the needed thrust. The actual HP and RPM's required will vary based on the prop diameter, the particular blade profile, blade pitch angle and the tip design. Ideally, the RPM's are set to keep the blade tip speed below supersonic for efficiency and noise control.
A T-6 on takeoff will have the prop tips well into the supersonic region, but the pilot reduces the blade pitch and the needed RPM's very quickly after takeoff, as not as much power is need to drive the prop at that point. It's a huge balancing game with some black art to it.

Really worth and rich explaining
Additional concerned, some ww2 aircraft has transmission or gearshift and other the connected directly to the prop such as in radial engine, does that related to torque convertion or just shift the engine crankshaft motion?
From your info, what is the max RPM allowed for P-51 mustang or A6M zero aircraft or any other good example you knwo

Also, when i camper, the hp for A6M zero is 940 hp from Nakajima Sakae 14 cylinder engine with 554 k/m as speed and Cessna 172 i see with 160 hp and 4 cylinder only and 226 km as speed
I am wondering, does this high hp was required at that time due to the limited of technology in other words, can i make by today same P-51 mustang or A6M zero aircraft with same performance with lower hp engine?

 

[Michael Hope]

I do not know of any engine with a transmission to shift gears between the engine and the propeller. Yes there were reduction gear boxes to run the propeller at a lower RPM than the engine was turning.

 

[GregP]

Horsepower = (Torque x rpm) / 5252.

Torque is higher below 5,252 rpm, and horsepower is higher above 5,252 rpm. So, diesels are usually oriented toward torque and petrol engine are usually oriented toward horsepower. Going back in forth is easy. At 5,252 rpm, torque = horsepower.

Torque in pound-feet.
rpm = revolutions per minute.
hp = 550 foot-pounds / second.
1 horsepower = 745.7 Watts.

Conversions are easy in Google.

 

[MiTasol]

Also, when i camper, the hp for A6M zero is 940 hp from Nakajima Sakae 14 cylinder engine with 554 k/m as speed and Cessna 172 i see with 160 hp and 4 cylinder only and 226 km as speed
I am wondering, does this high hp was required at that time due to the limited of technology in other words, can i make by today same P-51 mustang or A6M zero aircraft with same performance with lower hp engine?

Every different shape of aircraft has different power requirements to reach the same speed and drag increases roughly on the square of the speed.

As a VERY basic rule of thumb you therefore have to square the power to increase speed so to double the speed you need 4 times the power and to triple the speed you need 9 times the power.

Naturally when you double the speed you must also increase the strength of the aircraft or it will break and that makes it heavier which makes it slower. Also your 4x more power engine weighs about 4 times as much and that also slows you down.