Blue Seas 125A t-fuse....stud torque really 3/8" pounds? Finger tight only?

[Tomthumb62]

Inspecting Electrical Connections for Proper Torque

iaeimagazine.org

I only perused the article. But all these loose connections, did they at all tighten them good and tight? Or just a bit snug?

And “properly torqued” or just by proper feel, how often do such connections vibrate loose anyways and need to be re-tightened? Especially in mobile or marine cases?

How many people put too much faith into their torque wrench, even if properly calibrated and fail to ever recheck the connections occasionally?

What I’m getting at here is real torque wrenches are very expensive. And for a solar system you’re going to need both foot pounds and inch pounds wrenches. There are too many cheap torque wrenches out there. That few ever bother to calibrate. So in these cases, such torque wrenches are a liability. IMO. They’re better off doing it by feel and tightening it down as much as possible without damaging threads or connectors. And using good tools with handles long enough to apply decent torque without going overboard. You don’t need a two foot handle on a wrench for a connector with an inch pound spec.

The only place I can see a good use of a genuine calibrated torque wrench is when building a battery to make the cells as balanced as possible.

 

[Quattrohead]

Any torque wrench has to be better than none at all, have you seen Bubba leaning on a half inch bolt with 3 feet of pipe stuffed onto the end of his wrench LOL. Don't even baffle him with torque to yield.

 

[Hedges]

Can you tell I don’t trust most torque wrenches? Most people only think their torque wrench is calibrated but have never done so nor even know how to.

I'm still using the 3/8" Craftsman Microtorque my father gave me 45 years ago, with no worries. I'm fat, dumb, and happy.

I've got a few (Harbor Freight?) torque wrenches inherited from him. I've watched my step son strip a valve cover bolt using one because they are so far off. When we needed 105 foot-lbs. or so, above the 75 foot-pound max of the Craftsman, I used one against the other to "calibrate" or determine error at 75 foot pounds of the bigger cheap 1/2" one.

I've contemplated setting up a bearing, arm, weights for calibration but haven't done so.

Even with a torque wrench, friction, whether lubed or dry, results in nearly 2:1 range of clamping force.
Torque to yield makes sense (calibrated bolts) and I used that for Sable (Vulcan) heads. Although, Manual says torque for Vulcan OHV, TTY for DOHC model. The bolts from Felpro says TTY. I used the >click< torque wrench while doing TTY to observe similarities. Torque, back off, Torque, +90 degrees, +90 degrees. Second 90 degree turn went well beyond foot-lbs. spec.

When I first studied torque, I thought what I knew about Archimedes would determine clamping force, but that was off order(s) of magnitude. It is dominated by friction.

 

[Hedges]

I only perused the article. But all these loose connections, did they at all tighten them good and tight? Or just a bit snug?

And “properly torqued” or just by proper feel, how often do such connections vibrate loose anyways and need to be re-tightened? Especially in mobile or marine cases?

The biggest issue I run into is settling of stranded wires. Unlike a crimp connection, there isn't near enough force to crush the strands into a "gas tight seal".
Some settling occurs, but mostly my experience is that wiggling of a wire promotes settling, and it ends up quite loose, after having initially been tight.

What I do now is bend the wire in an "L" and wiggle to make rotating motion in the terminal. Re-tighten screw and repeat until it stops settling.

Flat things like terminals on batteries or busbars don't give nearly as much trouble.
I used torque wrench on AGM batteries, but for an old set didn't bother and heard a "crack" from the plastic.

The only place I can see a good use of a genuine calibrated torque wrench is when building a battery to make the cells as balanced as possible.

The cells have such a narrow band between loose and broken that it seems very advisable.

Other problem I see is a wire and terminal with one screw hole has leverage to loosen the nut. I think the design has to prevent that (busbars between two won't rotate, for end connection ideally have a limber fine stranded wire and secure it.)

 

[Tomthumb62]

Flat things like terminals on batteries or busbars don't give nearly as much trouble.
I used torque wrench on AGM batteries, but for an old set didn't bother and heard a "crack" from the plastic.

Yeah I kinda wish I had a torque wrench when tightening down my 1/0awg cables to my lifepo4 battery. I got them right by feel but it would be easy to over do it. Then again I don’t trust any of my torque wrenches. So I’ll edit to say, I wish I had a good torque wrench.

My first lesson in torque was with my first car. I rebuilt the carburetor. When it came time to tighten it down to the intake manifold, I just kept tightening until I could go no more. I bent all four corners of the carburetor! Gas mileage went down to 1-2mpg after that…

I don’t work in car stuff anymore that requires that level of precision torque.

 

[wheelman55]

I use Polaris Grey replacement sleeves to terminate fine stranded wire in screw down connections. NSI Industries make these sleeves to fit a range from 14 gauge to 2/0, 3/0. I also use their connectors.

The sleeves are tinned copper and come in 10 packs, available from most electrical supply companies. Sometimes on Amazon.

Click on one of the part numbers here to get to the information page. Then scroll down to the Polaris Grey section.

You can thank me later.

NSI Polaris Grey replacement sleeves

 

[incognito253]

Yeah, the fuse holder has a higher torque but I wasn't sure if I was supposed to use that torque for the fuse holder studs that mount the fuse, or use the torque specified by the fuse itself. The 3/8" pound number for the fuse is on the fuse spec sheet:

Fuse A3T / Class T 125 Amp - Blue Sea Systems View attachment 167145

Clearly, this fuse system works by physically detaching itself from the circuit and dropping to the floor if there is an overload. Or, also, if there is not an overload.