by "Rock Bottom" (rockbottom81)
Published 09/20/2017 at 10:45
by "Rock Bottom" (rockbottom81)
Published 09/20/2017 at 10:45
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STARS: 6
They’re stupid expensive, but they are damn cool. Years ago, I worked on a project that could have used them, but we ended up strain-gauging a different component in the assembly. It was the right decision, but it still made me sad. If I’m ever super rich, I’m going to randomly scatter these throughout my car and just collect data for no good reason. I will also host C4 Corvette demolition derbies. You’re all invited.
http://www.strainsert.com/product-categories/force-sensing-bolts-studs/
"miadaman? yes please" (wanjoe)
09/20/2017 at 11:15, STARS: 1
It’s so beautiful *shed a single enginerd tear*
How much weaker is it comparing to a regular ass bolt?
"Rock Bottom" (rockbottom81)
09/20/2017 at 12:15, STARS: 1
I’d bet that it’s similar to a comparable standard fastener. I think the weak point of a fastener is generally the threads? Any mechanical engineers here have an opinion?
"miadaman? yes please" (wanjoe)
09/20/2017 at 12:37, STARS: 1
Coincidentally I am a mechanical engineer - though I don’t work with bolts and screws anymore. I should’ve been clearer - I was wondering about the shear and bending load.
"gogmorgo - rowing gears in a Grand Cherokee" (gogmorgo)
09/20/2017 at 13:03, STARS: 0
It’s only going to reduce the strength of the bolt by a similar amount to a rod the size of the hole drilled. I imagine these holes will be pretty small if they’re putting them into 1/4" bolts. They shouldn’t need to be all that big either. I imagine if its enough of a reduction that it’ll cause issues, you would’ve wanted a bigger bolt there anyhow.
"Rock Bottom" (rockbottom81)
09/20/2017 at 13:04, STARS: 0
I did find this little nugget on the site:
In most bolts, neither the gage or the drilled hole reduce the allowable bolt load in a Strainsert fastener. The hole depth is confined to the shank of the bolt, and the hole diameter is controlled so that the bolt cross-section through the threads is smaller than the section through the shank with the gage hole. Therefore, the gage installation will withstand and accurately indicate high strength loads.
So I guess I would interpret that to mean they’re able to retain normal strength, which is neat. I’m an aerodynamicist, so fasteners are way outside of my wheelhouse, but I believe shear strength of a fastener is generally meaningless as long as the bolt clamping load is not exceeded? I think the shear load through a properly torqued joint it born by the friction of the two surfaces being clamped by the bolt? Now I’m going to have to dig up my old text books when I get home tonight!
"miadaman? yes please" (wanjoe)
09/20/2017 at 13:22, STARS: 1
Sounds like they’re saying this is a bolt you use for tensile load by the way they’re comparing cross section areas of different segments of the bolt. I don’t see how hollowed tube would have more shear strength than solid piece of metal. Neat contraption, I’ll take 50 Jerry.
"miadaman? yes please" (wanjoe)
09/20/2017 at 13:24, STARS: 0
Small holes introduces stress concentrations, but looks like it’s probably made for tensile loads where it is less significant!
"gogmorgo - rowing gears in a Grand Cherokee" (gogmorgo)
09/20/2017 at 13:33, STARS: 1
This is true.
I’d point out that generally bolts shouldn’t be loaded in shear anyhow, with the shear load being born by the friction between the two clamped segments. The only exception to this os where the bolt is also a pivot point, such as at the end of a suspension link, although in that case the strain wouldn’t be measurable very easily by this method. You can bend a bolt pretty far before there’s much change in overall length. Also the clamping force in that scenario isn’t very high, just enough a nut won’t spin itself back off.