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Freewheeling unit


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The Huey had a sprag clutch. The JetRanger/Kiowa has an accessory driven freewheeling unit. I don't know what the Robinson helos have, nor the 500. My question for discussion is...Which one is the all around best. Best design, operation, engineering, efficiency, simplicity, durability. Best all around, and why ?

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Your 206 has one of them sprag clutches. Accessory driven free wheeling unit? Never heard of such a thing. Neither has my mechanic, and he's worked on helicopters for 30 years. A sprag clutch is a free wheeling unit, although I'm sure there are some other incidental parts. And vice versa. You want a discussion on what is the "best all around" free wheeling unit? :blink:

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In my limited experience (MH-47, MH-60, B206, S300C, R22) all the free wheeling units are very similar except for size. Don't let the names of parts fool you. Different manufacturers have different terms and names for what is basically the same stuff on other makes.

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In my limited experience (MH-47, MH-60, B206, S300C, R22) all the free wheeling units are very similar except for size. Don't let the names of parts fool you. Different manufacturers have different terms and names for what is basically the same stuff on other makes.

 

+1 (from a former mechanic)

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Errr... a generator?? How are you associating this with a freewheel unit?

 

And I am missing the significance of the +1 and + 2

 

I think he was making a similar point in comparing the generator to an alternator-not comparing it to a freewheel.

 

+1, +2 just meant that we were in agreement to what nightsta1ker was saying.

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Doesnt matter if it's helicopter specific or not. Sprag clutch is a sprag clutch. If the driven half is turning faster than the driving half, it's allowed to rotate independently. If the driven half slows down then the driving half engages it and they rotate together. It's really quite elegantly simple.

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A generator creates dc electricity an alternator creates ac. There are other differences as well.

 

Correct... but in the Army it's called a generator even though it supplies A/C power to charge the battery. Mounts like an alternator, functions like an alternator, produces the same type of electricity as an alternator, but in the Army it's a generator. I think they take it to a barney level and since it generates electricity, it's a generator.

 

 

bluethunder was correct about my intended comparison.

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+1 on what nightsta1ker said. I've worked on the CH-53D, CH-53E, CH-46E, and 5 different models of the H-60/S-70. They all work pretty much the same. The CH-53E has a slightly more complicated design to support the 4400shp engine and be smoother/faster in operation and has more parts to it internally, and it has a higher fail rate. I'd say the simple design is the best, which is what most have.

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Bikerider said:

Correct... but in the Army it's called a generator even though it supplies A/C power to charge the battery. Mounts like an alternator, functions like an alternator, produces the same type of electricity as an alternator, but in the Army it's a generator.

 

What aircraft are you describing?B206? They have engine-driven generators, but that can then feed an inverter to get AC power for autopilots and some instruments. A battery requires DC power to charge it - an alternator needs to feed through a rectifier first.

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Bikerider said:

 

 

What aircraft are you describing?B206? They have engine-driven generators, but that can then feed an inverter to get AC power for autopilots and some instruments. A battery requires DC power to charge it - an alternator needs to feed through a rectifier first.

 

A HMMWV lol

 

Nightsta1ker: Good find. I had no idea that ALL it really is, is a one way bearing.

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  • 4 weeks later...

Bikerider said:

 

 

What aircraft are you describing?B206? They have engine-driven generators, but that can then feed an inverter to get AC power for autopilots and some instruments. A battery requires DC power to charge it - an alternator needs to feed through a rectifier first.

 

OH-58 has 2 generators, one AC and one DC.

Edited by SBuzzkill
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Guest pokey

Both generators and alternators produce AC current. Both convert it to DC, but in different ways. Any device that creates electricity by spinning motion, will produce AC current. On the other hand, devices that produce electricity w/out the use of motion ( solar power, batteries) will be DC. The generator converts AC to DC via a commutator, alternator via diodes. Another interesting note, piston engine magnetos,,,,, each time it fires, one firing is positive, next is negative-----sot THAT is why we 'rotate' our spark plugs to give longer life?

 

Sprag clutch, yes-nothing more than a 1 way bearing, there are a few different designs out there for the races tho, but? all use same principle,, lock up in one direction, freewheel in the other---automatic transmissions in cars have a few of these.

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I don't know if the term came from the army, Sikorsky, or GE but they were referred to as "AC Generators" on the T700 engines. The single engine Hueys had a generator driven off the front of the xmsn (D & H) and side (C & M), the starter generator was just standby and you'd switch it so after engine start.

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  • 3 weeks later...

In my limited experience (MH-47, MH-60, B206, S300C, R22) all the free wheeling units are very similar except for size. Don't let the names of parts fool you. Different manufacturers have different terms and names for what is basically the same stuff on other makes.

 

It's been a while since I logged all of my 10 hours in an R22, but don't they work by tightening that belt between the engine and transmission? That's a lot different than the H-60 freewheeling unit.

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