| Age old problem...loose pylons #87615 11/01/06 09:15 AM 11/01/06 09:15 AM |
Joined: Sep 2005 Posts: 1,187 38.912, -95.37 _flatlander_ OP
old hand
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OP
old hand
Joined: Sep 2005
Posts: 1,187 38.912, -95.37 | So help me understand something here guys. How long have the 14/16 been around? Going on 40 years? And over a period of time, and depending on use, the pylon to casting loosens up? And the best fix we have to date is "fill it with epoxy" or shim with beer cans? I know the epoxy method will only last two or three seasons before it loosens up again. What a bugger to pull that apart only to do it again? Can we do better than that?
This AL on AL wear can be expected. What is the root cause? Does the bolt have any effect on the wear? I think to a certain extent it does. This, over time, becomes a pivot point, assuming originally you have a close to snug clearance fit between the pylon and the corner casting. There is initially a small clearance that progressively becomes enlarged due to fore/aft and side to side flextion. Theoretically this "enlargement" will occur above and below the pivot point (the bolt)?
Why not drill and tap a set of holes in the corner castings say in four places as far above and as far below the pivot point as possible and install a set screw to "lock" the pylon within the casting? Over a period of time, they would become loose and need tightening. I suppose after a long period of time they may cause some serious wear on the pylon, but do epoxied, beer canned or new boats stay tight forever?
What do you engineering gurus think?
John H16, H14
| | | Re: Age old problem...loose pylons
[Re: Banzilla]
#87617 11/01/06 12:54 PM 11/01/06 12:54 PM |
Joined: Jul 2005 Posts: 306 St. Louis, MO hobienick
enthusiast
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enthusiast
Joined: Jul 2005
Posts: 306 St. Louis, MO | Tapping holes in the lightweight aluminum castings is a really bad plan. There is currently not enough material in the wall of the casting to create an effective thread. All you will do is strip out the threads the first or second time you crank down on the set screws.
Think of what you mentioned about the age of the boats... 40 years. That's 40 years of high stress repetative motion. Even steel will wear out over that time.
Shimming (in my opinion) is the best solution. It allows you to make a custom fit, is easily removed for repair or adjustment, and is easy and quick to do.
We also have to keep in mind the tolerances of the aluminu extrusions and the castings. The tolerance stack up has to allow for assembly of the components when they are at the worst case possible.
Using multiple bolts will only delay the issue. Then you will have more than one elongated hole.
Just to support my statments, I design and build high volume custom automated equipment for a living.
Nick
Current Boat Looking for one
Previous Boats '84 H16 '82 H18 Magnum '74 Pearson 30 St. Louis, MO
| | | Re: Age old problem...loose pylons
[Re: hobienick]
#87618 11/03/06 03:20 PM 11/03/06 03:20 PM |
Joined: Dec 2005 Posts: 321 Albuquerque NM Banzilla
enthusiast
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enthusiast
Joined: Dec 2005
Posts: 321 Albuquerque NM | I was just thinking that if you had more points holding the casting you would have less movement between the parts, but the tolerances might just be a problem after all. I would not suggest trying to thread the Al either.
Sam
[b] Sail Like you have a Pair
| | | Re: Age old problem...loose pylons
[Re: Sunvista]
#87621 01/11/07 05:54 PM 01/11/07 05:54 PM |
Joined: Feb 2005 Posts: 4,118 Northfield Mn Karl_Brogger
Carpal Tunnel
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Carpal Tunnel
Joined: Feb 2005
Posts: 4,118 Northfield Mn | And welding it will make it a little difficult to disassemble if you ever need to replace a hull.
I'm boatless.
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