4341 heat sink RPI4
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4341 heat sink RPI4

by mjmckenna on Mon Aug 02, 2021 4:01 pm

We use the RPi4 installed in a wireless receiver as an embedded computer. We are thinking the top half of the 4341 would allow us to heat sink the RPi4 to the receiver cover. Do you have a CAD model available for us to test the fit in solid works?

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Re: 4341 heat sink RPI4

by adafruit_support_mike on Wed Aug 04, 2021 7:59 pm

We don’t, and trying to estimate fit from models based on nominal dimensions is an exercise in pain.

The main problem is tolerance stackup: the combined uncertainty of every dimension around the loop that connects the parts on either side of the gap. In most cases there are enough non-critical dimensions with loose tolerances (0.015” or 0.5mm) that you have to expect variation of a couple millimeters or more.

Any closed loop of components is mechanically overconstrained: it only works if all dimenstions match exactly, which is impossible to do in real life. In practice, one piece that’s too short will end up carrying tension, in opposition to another piece that’s too long and carrying pressure.

There are two standard solutions, both of which start by designing the loop of rigid parts to have a gap. Then if your assembly can tolerate flex, you fill the gap with a flexible member (a spring, elastomer gasket, etc) that will deform under pressure without hurting anything. If the assembly has to be rigid, you spread the gap mechanically and will it with an additive material.. epoxy, grout, solder, etc.. let that harden, then release the loop to apply a known preload to the filled gap.

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