its like saying a car that needs to go on the freeway needs to run high rpms for the whole trip, why cant they just fit a tranny in it? im fully aware also about the fixed vs variable pitch props, but i want to know about a transmission wouldnt it simply be mor efficient to run low rpms like cars and save gas by not putting such loads on an engine? i know its not done for a reason but.. could it be done?
2007-09-15 22:34:28 · 11 answers · asked by Anonymous in Cars & Transportation ➔ Other - Cars & Transportation
think of tjhe weight issue
variable pitch ptops do much the same thing
the fuel that a gearbox would save would be taken up in lifting it off the ground!
2007-09-15 22:46:20 · answer #1 · answered by andy t 6 · 1⤊ 0⤋
generally piston aircraft engines are designed to operate at much lower rpm's[with a much more narrow rpm range] than automobiles this is one reason why they have a rather large displacement for the weight of the aircraft.[using prop size and pitch as the transmission] with no gearing in between, keeps things simple and light.
however some do indeed use a transmission [the theilert diesel conversion comes to mind [uses a mercedes auto engine and a reduction box to keep the engine at a more suitable and efficient rpm range. of course the pitch and prop size are still factors in the final equation for speed and economy
2007-09-16 00:08:42 · answer #2 · answered by hobbabob 6 · 1⤊ 0⤋
I think the lower end would O.K. unless those "blips" you mentioned were into the higher RPM range. Then you may have some burned bearings. If you want to be safe, remove the spark plug and rotate the crankshaft by hand and feel/listen for any resistance on the shaft. If you hear metal on metal sounds(you will know if you hear them!) or feel a grinding, forget the tuning and rebuild the motor. If not, and the shaft turns smoothly and quietly, fill the crank case to the proper level, get the bike roadworthy, and go for a nice cold ride and listen for any odd sounds from the motor. Still nothing, go ahead and have the tuning done. Remember it is O.K. to leave the oil in the crankcase if you are going to run the engine in the winter for short amounts of time. Best of Luck to you. Ride Safe
2016-05-20 23:31:17 · answer #3 · answered by ? 3 · 0⤊ 0⤋
Despite the turbine engine being so expensive, it is a rather simple design(compared to a car engine) that can handle MASSIVE power. Using a transmission would just cause more complications, because the engine simple doesnt need it. Plus, if you ran at low RPMS, that could prevent the jet or plane from flying smoothly through the air. Also, think about jets, a tranny would just slow down their acceleration and cause a lot of problems.
2007-09-15 22:53:43 · answer #4 · answered by Anonymous · 0⤊ 0⤋
On airplanes, weight savings is a major design consideration. Anybody who worked on cars know that transmissions are heavy. So if they need to run the engine slow, it is better to just lower the throttle.
Piston engines have the highest volumetric efficiency at their max torque (not at low RPM). So airplane piston engines are design to run at these RPM or higher.
Car engines are run low so they would last longer - not for efficiency. Airplane engines are required to be rebuilt often to PREVENT failure (I think 500 hours for commercial and rentals). So efficiency is what matters, not how long they last.
Good Luck.
2007-09-15 22:38:52 · answer #5 · answered by Lover not a Fighter 7 · 1⤊ 0⤋
They don't need a transmission - the prop is mounted directly on to the engine. I think you mean a means of varying the ratio between engine speed and prop speed.
Well, they do. It's called a variable pitch propeller, and it's fitted to all but the simplest of prop-driven planes. It's controlled by the blue knob/lever next to the throttle.
2007-09-16 06:08:59 · answer #6 · answered by Anonymous · 0⤊ 0⤋
Many of them have a variable pitch propeller that acts like a transmission. Please remember that an engine needs to turn at a relatively high RPM to produce horse power for take off.
2007-09-15 22:42:11 · answer #7 · answered by austin j 4 · 1⤊ 0⤋
A good question ,most are direct drive but others use a type of reduction gear.Your idea has already been developed in use in boats,usually a two speed box,you need an engine with plenty of torque(mostly diesel).
2007-09-15 23:20:22 · answer #8 · answered by Anonymous · 0⤊ 0⤋
Most small piston powered aircraft turn surprisingly low RPM's. Most only turn about 2600 at cruising speed.
2007-09-16 12:23:15 · answer #9 · answered by Bill D 3 · 0⤊ 0⤋
On fixed wing aircraft it is a matter of weight. Not efficient to control the torque of a thing that does not need surface traction .
2007-09-15 22:44:43 · answer #10 · answered by Anonymous · 1⤊ 0⤋