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Brettw

I want to learn

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Brettw
For as long as I can remember, every generator I have ever owned, and most I have seen, are powered by a tapered shaft engine. Why? What is the purpose of the shaft being tapered on generator engines? Enquiring minds want to know.

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ReedS
I think and most like I will be wrong, the taper makes a good and secure connection the stator, almost to the point where it is one shaft, it also reduces the size of the shaft that is needed. If one were to use a straight shaft engine the size of the stator shaft would have to have at least a 1" I.D. which in turn would be heavier in weight. Just a thought. That and a nickle still won't buy a coffee!

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steve-wis
I will add my 2 cents worth as well. A taper fit is the best way to keep something running true. Balance would be important in the generator application, I would think. Compare to the flywheel on your engines, mounted on tapers, as opposed to the pulleys on the output end, most always straight with set screws. The flywheel is heavier and must run true to eliminate vibration. Just a guess. Steve

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1Litre
Steve is right on . The weight of the rotating assembly (very heavy copper winding)has to spin tru or it will flex the shaft to a point of fracture in short order. They can be a pain to seperated. Ken

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powerking_one
Steve and Ken are right on. The copper wound rotors are very heavy and precisely rotationally balanced. So any "wooble" on the crankshaft would have serious bad effects on the engine/crank and the generator itself. Case in point, Mcculloch made a series of generators back in the 70's which was very short lived due to catastophic failure of the rotors coming loose because they decided to use a straight keyed crankshaft instead of the standard tapered design accepted in the industry. I bought one of these for $10 at an engine show a few years ago and sure enough, it (the rotor) came loose, crashed into the stator housing, destroyed the key/keyway, and bent the crank. Is this enough for you to "learn". Tom (PK)

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acfarmer
If all thats true then why can generators like the ones made for the rear of Simplicitys and PTO generators last for years? Personally I think its for ease of manufacturing and specialized replacement parts sales.

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powerking_one
Gary, I would go consult with the A.S.M.E. organization and ask why this is the time proven design method of of direct mounted/coupled generator rotors via a tapered shaft interface is the standard. Tom(PK)

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Brettw
quote:
If all thats true then why can generators like the ones made for the rear of Simplicitys and PTO generators last for years? Personally I think its for ease of manufacturing and specialized replacement parts sales.
I would think being belt driven vs a straight solid connection would be the difference. I am still not sure I fully understand how the taper prevents or eliminates wobble? But, I would think being belt driven vs a straight solid connection would make a considerable difference in regard to rear mounted PTO driven units.

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acfarmer
I have a 35 year old generator that was factory on a New Holland T220 that drives by a driveshaft directly off the front PTO of the tractor and it performs flawlessly.The cheapie low end generators are the ones mostly with the tapered shaft engines.There are numerous high quality keyed shaft generators/alternators around that will give years of service.The quality of the end bearing are key to the life of a generator.My 45KW PTO generator is straight keyed shaft with a PTO gearbox never had a problem.

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Brettw
I hope Dan does not mind, but he PM'd me with this and I thought I would share. This is the answer to my question. Thanks again, Dan.
quote:
Fitted collar and key solutions have a common machined difference of 10 mil, or about 100th of an inch. This allows for fitting and some oxidation. When the set screw is tightened the device attached to the shaft will run slightly oblong. Normally this is not an issue and is done with light radial loads like pulleys. It had no adverse effect on bearing loading. This solution also will wear more than taper solution because the contact serface is far less, usually the side of a key and a small amount of the shaft. This is seen when key ways wallow out. Tapered shafts run virtually perfectly true when fitted. When a radial load is heavy when compared to shaft/bearing size these are used. These do not perform well to jerk but a generator has very little due to its ability to slip fields momentarily. A fly wheel uses small shear key in the event of a large jerk, like hitting a rock stopping the mower. This will cause it to go out of time BTW, jerk is the change in acceleration. There are more ideal coupling solutions but they cost more and require greater space. Hope this helps some, Dan

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