Prop shaft

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Dan Thomas

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...right, probably a little more than a pound.
Then there is the hub, spider, pitch-links .... TR ARE light!! But with the above mentioned forces at work, attaching gear has to be designed rather tough - at the end - a R44 TR has a tip speed of 614 fps while doing 2428 rpm....
I'd guess the TR weighs in about the same as the 206 blades (Robinson makes a SUBSTANTIAL TR...)
....for those of you who want to throw numbers right away!!

thjakits
The hub and pitch links are close to the center of rotation and don't impart much of a flywheel effect. Not nearly the effect of a rotating 25-pound aluminum fixed-pitch prop. That prop has way more inertia than the cast iron flywheel on a car's engine. If it wasn't for the aerodynamic drag on it, the engine would take a lot longer to stop after shutdown.
 

Turd Ferguson

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Lesher got some help from Molt Taylor on the drive train.
I think that's correct.
I have an old EAA article on E.L's Nomad and Teal. They both used a Dodge Flexidyne 9C dry fluid coupling, an 8 lb flywheel and support bearings on the driveshaft as I think the driveshaft on the Nomad was over 8 ft long.
 

Bigshu

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I think that's correct.
I have an old EAA article on E.L's Nomad and Teal. They both used a Dodge Flexidyne 9C dry fluid coupling, an 8 lb flywheel and support bearings on the driveshaft as I think the driveshaft on the Nomad was over 8 ft long.
Can you cite the issue? I tried a search of the EAA site and got nothing.
 

Turd Ferguson

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Toobuilder

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Look at the c 5-6 vette drive system.
Look at 63 Pontiac lemans.
Two very diferent approaches to a similar configuration:

My 63 Tempest had a full sized clutch weight flywheel at the engine side and a small diameter (mine was 5/8 inch) solid rod running back to the transmission, and THEN drove a torque convertor. Solid flanges on each end of the shaft - no u joints or flex couplings. So two massive flyweights on either end of a very, very springy shaft.

My C6 Vette has the flywheel and clutch on the engine as usual, then a rubber flex coupler connecting to a stiff tube style driveshaft. Then another flex coupler at the transmission (either a torque converter or direct input into the box)

The Pontiac uses the shaft itself to absorb all the disharmony between flywheels, while the Vette throws it at the clutch and couplings.
 

wsimpso1

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Any chance a hydraulic pump and motor combo would work ?
Sure, but it has 10-20% losses. Sort of like an electric powertrain, maybe lighter, but still throws away a bunch of energy we spent fuel through an engine to get.

We take off and climb at 80-100% power, cruise at 60-75%, we even descend at 35-50%. Since we have to carry that much engine anyway, straight mechanical with properly schemed out vibe management is light and about 98% efficient drivetrain. All that other stuff is folly.

Billski
 

Pale Bear

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Helicopter driveshafts .. here's a study on a Huey's tail rotor.


Someone mentioned about a 20% power consumption, for a tail rotor system, of the total .. this data seems to agree with that, .. up to 170 HP at times, for a Huey. So, if you can satisfy the flexing issues, (tubes are springy things, in the radial direction) .. these driveshafts, eh? And find the nearest Huey junkyard?

Attached, is one page of that PDF.

I was around this aircraft, some. Quite a bit of maintenance, the tail rotor system .. and the alignment of everything, had to absolutely be right on.
 

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Bigshu

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What happened to the OP? 68 posts and no response.
We didn't support his desired position? "it's not that simple" wasn't what he wanted to hear? Or he's still processing the info on the thread.
 

Bigshu

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Pilot-34

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Sure, but it has 10-20% losses. Sort of like an electric powertrain, maybe lighter, but still throws away a bunch of energy we spent fuel through an engine to get.

We take off and climb at 80-100% power, cruise at 60-75%, we even descend at 35-50%. Since we have to carry that much engine anyway, straight mechanical with properly schemed out vibe management is light and about 98% efficient drivetrain. All that other stuff is folly.

Billski
If 20% loss was the only downside I would adopt that in a heartbeat for certain configurations (like a buried engine seaplane twin)
But what about weight!?
My research found a mechanical connection buried engine twin of Russian design, unfortunately it was also incredibly heavy to do that.
Now if part of the additional weight is essentially taking power pulses out of the system and reducing engine speed to prop speed It might be worthwhile.

What counts I suppose is like what is continually pointed out here , A airplane is the end result of 10,000 compromies.
 

wsimpso1

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If 20% loss was the only downside I would adopt that in a heartbeat for certain configurations (like a buried engine seaplane twin)
But what about weight!?
My research found a mechanical connection buried engine twin of Russian design, unfortunately it was also incredibly heavy to do that.
Now if part of the additional weight is essentially taking power pulses out of the system and reducing engine speed to prop speed It might be worthwhile.

What counts I suppose is like what is continually pointed out here , A airplane is the end result of 10,000 compromies.
To do this requires hydraulic pumps and motors and control valves. To do it without big investments, you would need COTS parts. You are the one interested in doing this. You can certainly get educated and do the shopping. Define your engine torque and rpm, then your motor torque and rpm, then go find a pump, its gpm at your power, then hydraulic motor(s) to suit. Then you can tell us the efficiencies and weights.

Billski
 

Pilot-34

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To do this requires hydraulic pumps and motors and control valves. To do it without big investments, you would need COTS parts. You are the one interested in doing this. You can certainly get educated and do the shopping. Define your engine torque and rpm, then your motor torque and rpm, then go find a pump, its gpm at your power, then hydraulic motor(s) to suit. Then you can tell us the efficiencies and weights.

Billski
I try not to reinvent the wheel.
It always amazes me how much people on this forum have done.
 

Geraldc

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To do this requires hydraulic pumps and motors and control valves. To do it without big investments, you would need COTS parts. You are the one interested in doing this. You can certainly get educated and do the shopping. Define your engine torque and rpm, then your motor torque and rpm, then go find a pump, its gpm at your power, then hydraulic motor(s) to suit. Then you can tell us the efficiencies and weights.

Billski
A hydrostatic drive system from a small tractor might suit.

This system has been used in aviation before.
The Sperry Rand ball turret drive used this system.
One lever controlled speed and direction.
This unit weighs just under 10 kilograms.

1617571638165.png
 

Vigilant1

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Rotary hydraulic drives and "motors" generally find application
where RPMs are low and torque requirements are high (tractors or track drives, etc). They are heavy because forces (hydraulic pressures and mechanical reactive loads) are high. To use them with a propeller turning 2000+ RPM would require mechanical gearing and yet more weight. Or, lower the pressures and torque by using lower fluid pressures and much higher fluid speeds and pay the price with fluid friction losses. There's a reason we don't see hydraulic drivetrains in airplanes.
On the other hand, if we want a low rate flapping wing ornithopter, maybe hydraulic linear actuators would be "interesting." :)
 
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wsimpso1

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I try not to reinvent the wheel.
It always amazes me how much people on this forum have done.
Nobody's doing this in airplanes. Lawnmowers and agricultural equipment, sure. So if someone want's to figure out what the losses and weights are in any particular hp range, they have to go see what the available equipment does.
 

wsimpso1

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Ford and the EPA did some hydraulic hybrid work and wrote it all up here:
Supposedly there are still garbage trucks being sold with these. The initial idea was to save fuel. They removed the driveshaft from the transfer case to the front axle, installed H-machines on the axle and the transfer case, than put several big accumulators under the vehicle. Dynamic braking using the H-machine on the front axle would charge the accumulators, then they would take energy out of the accumulators during accels. The H-machine on the transfer case was used to make up for the inevitable losses in the cycle. While it allowed garbage trucks with their high frequency start-stop operating cycle to save some fuel, the big advantage was that a company could run a contract with less trucks because their trucks needed to be in the shop for brakes a lot less often than with conventional powertrain. Maybe you can glean some weight info from the SAE paper. The author was my best man and a great friend...
 
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