On Sun, Jan 12, 2025 at 07:40 AM, Mike Colyar wrote:
Those needle bearings are a very good thing. And a drop of oil or grease on the threads as well.
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I build custom machinery of all sorts and whenever possible I avoid short fasteners. The object of a screw fastener is to clamp things together. I don't really care what the torque numbers might be as long as I get the clamping forces needed. As soon as you get away from cheap junk like internal combustion engines for the masses, the idea of a torque wench goes out the window. We use either hardened and lubricated washers or, if practical from a corrosion point of view, those needle thrust bearings. Friction is your enemy. Of course you can go to far in this direction and have the nut back off. Seldom an issue but possible.
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The procedure is to take the slack out of the system and then turn the nut a specified angle based on a simple incline calculation. What we want is a certain tension on the bolt. Or to put it another way, a specified amount of stretch. This is not 'rocket science' but just understanding the relationship between stress and strain. Once you get used to the idea that everything, and I mean everything, is elastic, it's easy to to figure out how to convert an angular rotation of a nut into tension on a fastener. If the bolt is short, the desired tension comes up really fast. Use a longer bolt or a finer pitch thread. Perhaps swap out that 3/8" x 16 bolt for a 3/8" x 24.
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Before you all start tuning up, I know that this is a classic case of 'Garbage in. Garbage out.' That is to say, how do you know what tension is desired on the fastener? As the preacher said to the townspeople in the movie Blazing Saddles, "You're on your own!".
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Mike Colyar
Lopez Island, Washington State
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(Wintering in Baja where it's B1/B2 skies every moonless night. Eat your heart out.)
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Unless the mount base is drilled and new threads cut the pitch is not going to change.? There is plenty of mass and friction to hold the mount stable on the mount base with modest force.
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People here somehow always think that more force is always better which is completely incorrect.? I see it every day, for example people posting how their clutches are slipping and they need more torque on the clutch plates.? Think about it, why would the clutches slip if the clutches are clean and dry?? Because they are not clean and dry? Because the saddle payload is not properly balanced on both axis???
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I have no slippage on my 20+ year old fully updated G11G with 60 pounds in the saddle while imaging and I don't have to torque the bejeezus out of the clutches for some reason.? I occasionally take that same mount and pull off the imaging gear to go visual by simply rebalancing the payload and basically fully loosening the clutches for 2 finger PUSH-TO operation and it still tracks any object perfectly all night.
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This is the way the Losmandy mounts were designed to be used and they work perfectly this way.? If your mount doesn't work this way you have an unbalanced mount payload, contaminated clutches, incorrectly assembled mount, dirty bearings, distorted clutch surfaced damaged by over torqueing the clutches end of story.?
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Chip Louie Chief Daydreamer Imagination Hardware?
Astrospheric Forecast - South Pasadena, CA?
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Chip Louie