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Old 12-13-2012, 04:28 AM   #1
susho

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Default Pressure using bolts

anyone got numbers? I'm using a bolt clamped mould, and seem to get good resin out while I'm laminating as Dry as possible.
I need a part with a good finish both sides and clamped moulds seem a good solution. clamping with a vacbag is possible, but bolts are faster and cheaper
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Old 12-13-2012, 10:48 AM   #2
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numbers of what?
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Old 12-13-2012, 06:34 PM   #3
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I assume he's looking for clamp load for a given torque, but I could be wrong.

Does this help: http://www.spaenaur.com/pdf/sectionD/D48.pdf
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Old 12-13-2012, 06:36 PM   #4
Kevin Doe

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This may help also:

http://www.engineersedge.com/calcula...orque_calc.htm
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Old 12-14-2012, 07:18 AM   #5
riff42

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That depends on your mold shape, how many bolts,etc. If it's a closed mold, it depends on the volume of the mold cavity vs. how much fiber/resin fill.
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Old 12-14-2012, 08:58 PM   #6
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The axial tension in a bolt can be approximated by:

Axial tension (lbs.) = torque (in/lbs) / bolt diameter (inches) / K-factor
Use a K-factor of .2 for non-lubricated steel to steel and .28 for non-lubricated zinc plated to zinc plated.

The total force would be the sum of the axial tension of each bolt. The pressure, in terms of psi, would be the total force (lbs) divided by the mold surface area (square inches).
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Old 12-16-2012, 04:23 PM   #7
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your calculation is very simple if you vacuum bag it i.e. the vacuum pressure

the bolting calculation is more involved - the bolt loads are easy to calculate but their load distribution is non uniform - FEA or hand calcs
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Old 01-02-2013, 02:30 AM   #8
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Thanks everyone, some good stuff in here!
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