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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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How to secure a rotating disc so that it has no wobble

For a 3D printing application, I need to have a spinning disc(that I will rotate via geared stepper motors) that will wobble as little as possible. By wobble, I mean that it will only rotate around it's axis and not shift side to side. The goal is…
James Baxter
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Are there pumps that can vary their pressure and flow rate, while maintaining the same power?

To avoid the inconvenience of buying compressed "air" cleaners and scavenging quarters for refilling tires, I'd like to get a pump that can do 72 PSI (vapor pressure of difluoroethane minus atmosphere pressure) at ~2 liters/minute for dusting, and…
Yale Zhang
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Using a 'D' shaped shaft with a set screw

Suppose a 'D' shaped shaft with a 4 mm diameter like this type is fitted inside a module 1 (plastic) gear with a round hole with the same diameter. If the gear has a set screw, will this still be a good fit? Will all the force be transferred to the…
John M.
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Sliding mode surface derivative using numerical method

In the article Controller Design using Bifurcation Map for Aircraft Spin Recovery, the sliding surface derivative is obtained using a numerical method. The steady space system is defined by the following…
lahidj
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Are typical worms and worm gears self-locking?

Does anyone know if typical/common worms and worm gears self-locking (plastic or metal)? Are the self-locking ones specially designed (with specific angles) in order to be self-locking? By self-locking, I mean that the worm gear can't turn the worm…
Kar
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Derivation of the AASHTO formula of interior girder moment

The interior girder moment formula for one lane loaded for the AASHTO LRFD method is: $$\begin{align} mg^{SI}_{moment}&=\left(1.75+\frac{S}{3.6}\right)\left(\frac{1}{L}\right)^{0.35}\left(\frac{1}{N_c}\right)^{0.45} \\ &=…
Victor
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Does a rotating platform on a space vehicle affect the vehicle's trajectory?

Recently I watched The Martian and the space vehicle Hermes in the movie had a rotating platform. I wonder if that would significantly cause the vehicle to be inclined in direction? Does a spinning platform/living space on a space vehicle, used to…
Aloysius
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How safe is this assumption for turbulence modelling in porous media?

I am studying the performance of volumetric solar receivers (specifically ceramic foams) versus the change of many parameters: solar flux, surface temperature, porosity, pore diameter, flow pressure and flow velocity. I have seen two ways in the…
Algo
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How do you apply fits and tolerances when designing hole and shaft?

I am familiar with the basic concepts of fits and tolerances, and I am aware of the various online calculators for determining them. However, I don't understand how to apply those numbers to my actual CAD design for the parts that I want to fit…
Ryan Norbauer
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Can a DC voltage booster be connected directly to a DC to AC inverter?

I am doing a project on a generator. Instead of using an alternator I am using a dynamo. I then amplify the voltage produced using a DC to DC voltage booster. However, can I get a higher AC voltage by connecting it directly to a DC to AC inverter? I…
momo
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How to 'smooth/flatten' the surface of a disturbed liquid without contacting it?

I would like to essentially flatten or smooth the surface of a viscous liquid after dropping an object into it, without actually touching the liquid. For example, if I drop a rock into a tub of oil, I need the oil to move into the void and return to…
user88720
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