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1500 questions
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2 answers

Designing non-self-locking worm gear

I see that most worm gears are self-locking but I'm looking to make my own non-self-locking POM worm gear. It'll only be of module 1. Does anyone know what needs to be changed in order to make a self-locking worm gear non-locking? Is it just the…
John M.
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How to increase the air flow rate through a dust-separating cyclone?

I'm making a dust extractor for a desktop CNC milling machine. My design process was very crude: I looked at some DIY dust-separating cyclones, and it seemed like they just work without any advanced calculations, so I visually copied some of those…
bobtato
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Determining mass flow rate and exit velocity of compressible flow

This one's a bit of a doozy, so please feel free to comment on any one single part or parts to this problem. The setup is simple--I have a container (an empty bottle) which I fill with a certain pressure of compressed air through a car tire valve…
Avant Guard
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Why does tensile testing in thin films (ASTM D882) require a non-dogboned sample?

The ASTM dicates a plain rectangular shape. I understand that the material necks pretty quickly but I frequently get breaks in the grips, particularly with films of thickness less than 0.002." Dog bone samples seem as though they would help, so why…
Sully45
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How to specify and tolerance a "sharp" point?

I need to have an electrical probe machined; but I am unsure how to specify my requirements. I am an electrical engineer with only moderate mechanical knowledge. The probe will be machined from 0.125" diameter stainless steel round stock. The last…
PaulB
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Statics and Structural Analysis: Determinacy in beams/frames

I have a question about the methods to decide whether a beam/frame is determinate or indeterminate. Typically you can count the number of reaction forces and compare them to the number of elements to determine this. The typical equation for a…
Grady F. Mathews Iv
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What is a flexure bearing?

I have been reading a lot on flexure bearings, but it's still not really clear what they are. From everything I've seen, it seems like a flexure bearing is just a spring. Can someone give me a simple explanation of what they are and their use?
Capybara feet
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Maximum transmissibility of sky hook damper

I have been studying the sky hook damping system. On page 14 of paper linked above, I found that the maximum transmissibility of sky hook system can be calculated by: $$T_{max} = \dfrac{1}{2\xi}$$ where $\xi$ is the damping ratio and $T_{max}$ is…
KKS
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Why use bushings of different material than what they contact?

I've heard that materials that need to slide against each other should be of different materials. Why is that?
uncaged
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Can the strength of a strut be determined by deflections?

I am interesting in replacing a solid strut with tubing, but I do not want to destructively test the strut to determine its yield point. I do not want to make assumptions about the yield point based on material, because heat treatment and other…
Wallace Park
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Is it possible to remove Staedtler ink from a paper?

I am practicing engineering drafting and sometimes I am near on finishing my work but suddenly I make a mistake. Is it possible to remove the ink? If yes, how? Where can I buy such tools? I am using a Staedtler's Mars Matic 0.5mm.
Cary Bondoc
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Relating internal stress of an o-ring due to thermal expansion to amount of free volume in a gland

I am trying to come up with an analytical way to determine the optimal gland size that an elastomer o-ring will sit in. The amount of free space in the gland is determined by the thickness of two backup rings that surround it. Thus, the thicker the…
LSUEngineer
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Strand layout in prestressed concrete girders: is a partially filled bottom row acceptable/advisable?

My state (USA - Nebraska) uses "NU" type prestressed girders (though the question should equally apply to all geometric variants of prestressed concrete "I" girders). There are 6 "rows" available for the prestressing strand. Moving from the bottom…
CableStay
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How do I determine the thermal resistance of a metal box?

Suppose I have a sealed enclosure, say this one from Hoffman: The box is 16"x12"x6", made of galvanized steel with a wall thickness of .0635" or .0785" (gauge 16 or 14). I'm planning to put some electronics in this box, which will generate an…
Stephen Collings
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Appropriate finish type for a new lathe crossfeed?

I have a metal lathe with a broken part. The part is not available, so I have to machine one up from scratch. As this part is the lower half of the crossfeed assembly on the turret cutter, it has to be accurate, which is no problem for…
personal privacy advocate
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