Allowables for saddle clamps
Allowables for saddle clamps
(OP)
I'm writing up stress notes for an electrical conduit in the fuel tank, and one item of contention is that the saddle clamps have no allowables. The prime does not have test data, and as best I can tell hand waves them as having worked in the past. (the joys of systems stress!)
Analytically, I am having trouble on how to treat them... If I look at a load parallel to the fasteners (vertical), I can treat it as a pair of tension clips, and get an allowable of ~75 lb (using FBU). Hoop capability is 7800 lbf. I don't really believe either one of these that much. Probably closer to the tension clip, but it seems low to me as well.
for ref, the saddles are t=0.02", w=0.5", tube d=1.25", material 2024-T6 sheet
any thoughts or suggestions?
Analytically, I am having trouble on how to treat them... If I look at a load parallel to the fasteners (vertical), I can treat it as a pair of tension clips, and get an allowable of ~75 lb (using FBU). Hoop capability is 7800 lbf. I don't really believe either one of these that much. Probably closer to the tension clip, but it seems low to me as well.
for ref, the saddles are t=0.02", w=0.5", tube d=1.25", material 2024-T6 sheet
any thoughts or suggestions?





RE: Allowables for saddle clamps
as an aside, I don't see an edit button for the post..?
RE: Allowables for saddle clamps
The simplest analysis is the one you don't have to do.
When using a mil-spec clamp such as this, for its intended purpose, arranged in the correct manner, having made sure that the materials are correctly selected, then there's usually not much stopping you or the approving authority from accepting the installation. Unless your case is different (you mention a fuel tank...) for some reason such as extreme vibration, chemical attack, weight or flexure of the conduit, trouble sealing... If there is a specific problem that is driving this, then the analysis can be targeted, to collect the information needed to answer the question.
Otherwise I'd just say, use the tension clip analysis, or do your own test, or find someone else's test results (good luck with that).
STF
RE: Allowables for saddle clamps
I am starting to believe the tension clip analysis. Kind of depressing. The side load is the one that hurts. I'm pretty sure one side of the clamp resists alone while the other side only reacts hoop loads.
RE: Allowables for saddle clamps
as you'd mentioned, as long as the design guide is followed, the tube will fail long before the clamps, so they can essentially be hand-waved.
now if only I had seen the error of my ways sooner...
RE: Allowables for saddle clamps