Prop nuts for four-stroke engines - A design flaw?
11-08-2003, 03:03 AM
#1
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Prop nuts for four-stroke engines - A design flaw?
I think that when the first four-stroke manufacturer designed the two component locking nuts, for such engines, they got the design reversed. All other four-stroke (and some large two-stroke) manufacturers just copied this wrong design.
The current design has a large hex main nut, that must be quite deep to have enough thread to mesh with the crankshaft thread, despite the conical hole in its front surface, to tighten the prop down.
It does not have any means to lock onto the thread.
The second, smaller hex nut, has the threaded, conical, locking "arms", that tighten against the crankshaft thread as they are forced into the conical void, in the larger hex main nut.
As this second nut is tightened in, it wears down its "arms'" thread and the crankshaft thread.
In addition, it locks itself dynamically, which is not as strong as a static lock.
The large main nut is not at all locked onto the crankshaft thread.
I have seen such nuts let go and back-off enough allow the prop to move and break the spinner, in bad pre-ignition incidents.
The design must be reversed; the large hex main nut will have the conical locking "arms" protruding from its front surface, it would not need such a deep hex, because the "arms" also have a thread inside them.
After it is tightened down on the prop, the deep hex, lock nut, with the conical void in its rear surface, will statically force the locking "arms" of the main nut, against the crankshaft thread. This nut need not have a smaller hex than the main nut.
This static locking is much more resistant to turning, than is the dynamic locking described in the previous paragraphs.
It does not wear the threads down when tightened and it is much less prone to "let go" as a result of a pre-ignition situation.
The result; Less broken spinners, less thrown props, more safety.
This is now patented, date signed...
The current design has a large hex main nut, that must be quite deep to have enough thread to mesh with the crankshaft thread, despite the conical hole in its front surface, to tighten the prop down.
It does not have any means to lock onto the thread.
The second, smaller hex nut, has the threaded, conical, locking "arms", that tighten against the crankshaft thread as they are forced into the conical void, in the larger hex main nut.
As this second nut is tightened in, it wears down its "arms'" thread and the crankshaft thread.
In addition, it locks itself dynamically, which is not as strong as a static lock.
The large main nut is not at all locked onto the crankshaft thread.
I have seen such nuts let go and back-off enough allow the prop to move and break the spinner, in bad pre-ignition incidents.
The design must be reversed; the large hex main nut will have the conical locking "arms" protruding from its front surface, it would not need such a deep hex, because the "arms" also have a thread inside them.
After it is tightened down on the prop, the deep hex, lock nut, with the conical void in its rear surface, will statically force the locking "arms" of the main nut, against the crankshaft thread. This nut need not have a smaller hex than the main nut.
This static locking is much more resistant to turning, than is the dynamic locking described in the previous paragraphs.
It does not wear the threads down when tightened and it is much less prone to "let go" as a result of a pre-ignition situation.
The result; Less broken spinners, less thrown props, more safety.
This is now patented, date signed...
11-08-2003, 03:54 AM
#2
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RE: Prop nuts for four-stroke engines - A design flaw?
Dar:
You must have had a whale of a patent lawyer to get that one through. Saito had the main nut with locking flutes years ago, My 1.20 came with it. And a patent examiner here would say you've just inverted the Saito design, no "Intrinsic New Idea" involved.
See pictures.
Bill.
You must have had a whale of a patent lawyer to get that one through. Saito had the main nut with locking flutes years ago, My 1.20 came with it. And a patent examiner here would say you've just inverted the Saito design, no "Intrinsic New Idea" involved.
See pictures.
Bill.
11-08-2003, 07:01 AM
#3
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Thread Starter
RE: Prop nuts for four-stroke engines - A design flaw?
William,
You got what I wrote wrong.
Your photos show a single nut arrangement, in which the main nut tightens when turned into the cone shaped hole in the washer.
It is very much like the current lock nut arrangement, with the wide, cone shaped cavity washer, replacing the main nut.
Take the nut in your photos and tighten it flat side in, fluted side out, on a FLAT faced washer. My idea is a locknut with a cone shaped cavity that will now tighten on the fluted main nut, pressing the arms against the crankshaft thread.
The current design used in most engines is definitely lacking.
You got what I wrote wrong.
Your photos show a single nut arrangement, in which the main nut tightens when turned into the cone shaped hole in the washer.
It is very much like the current lock nut arrangement, with the wide, cone shaped cavity washer, replacing the main nut.
Take the nut in your photos and tighten it flat side in, fluted side out, on a FLAT faced washer. My idea is a locknut with a cone shaped cavity that will now tighten on the fluted main nut, pressing the arms against the crankshaft thread.
The current design used in most engines is definitely lacking.
11-08-2003, 07:05 AM
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RE: Prop nuts for four-stroke engines - A design flaw?
Dar:
I understood exactly what you were saying. What I said was that the patent examiner would say all you had done was turn the Saito nut over. Which is just what you said in the last post.
Bill.
I understood exactly what you were saying. What I said was that the patent examiner would say all you had done was turn the Saito nut over. Which is just what you said in the last post.
Bill.
11-08-2003, 07:12 AM
#5
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Thread Starter
RE: Prop nuts for four-stroke engines - A design flaw?
Yup,
...And used a larger size fluted nut, and reversed the roles.
And a much more effective way to prevent the main nut (that was previously the locknut) from turning.
And it is this main nut which must stay tightened, to keep the prop from turning.
And no crankshaft thread wear...
It is better than the currently accepted arrangement.
...And used a larger size fluted nut, and reversed the roles.
And a much more effective way to prevent the main nut (that was previously the locknut) from turning.
And it is this main nut which must stay tightened, to keep the prop from turning.
And no crankshaft thread wear...
It is better than the currently accepted arrangement.
11-08-2003, 11:23 AM
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RE: Prop nuts for four-stroke engines - A design flaw?
ORIGINAL: DarZeelon
Take the nut in your photos and tighten it flat side in, fluted side out, on a FLAT faced washer. My idea is a locknut with a cone shaped cavity that will now tighten on the fluted main nut, pressing the arms against the crankshaft thread.
The current design used in most engines is definitely lacking.
Take the nut in your photos and tighten it flat side in, fluted side out, on a FLAT faced washer. My idea is a locknut with a cone shaped cavity that will now tighten on the fluted main nut, pressing the arms against the crankshaft thread.
The current design used in most engines is definitely lacking.
And you are right, the locking systems currently used are made the wrong way around. My 1.50 originally has the system like in the pics William posted, and I found that you cannot tighten the prop AT ALL with this system... So I just turned the nut the other way around, tightened the prop, made a nut with a conical cavity and used that to lock the main nut onto the shaft...
11-08-2003, 03:47 PM
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RE: Prop nuts for four-stroke engines - A design flaw?
Gentlemen : My thoughts on the corrective means of holding the propeller, fly-wheel or clutch that you have described is just that you are just going to pass the problem to the next step down stream . My experience with working with mechanical objects is you are going to find the next weak link sooner or later , crankshaft , crank pin , rod or wrist pin . As you keep increasing strength in these items eventually you will have increased weight where it will no longer be a practical engine . The reason these engines throw propellers I feel is one of two things , manufacturing defects through design errors and operator error . If one make engine is more troublesome than others , just quit buying them . The manufacturer will get the word that they must do something. The operator can change to different plugs, fuel or his starting methods. Just comes down to that for every action there is a reaction. Just my thoughts , MAX H.
