JB Weld versus Loctite for grubscrews

[Solarfun4jim]

@BiduleOhm ....et al
What i'm struggling to get my head around, is why the 300kgf needs to be divided by the number of rods or fixture points? I would have thought that each fixture would need to impart 300kgf(or Newtons equiv value), no matter how many fixtures...they are all imparting the same force evenly. If you go to kgf.cm or Nm values, then over the 'area involved', then needs to be accounted for and thus needs to be divided by number of fixtures over that area???
I have no engineering experience/understanding whatsoever, so struggling with this concept. Is my thinking totally flawed?

To my limited thinking, it shouldn't matter if there is one fixture right in the middle of a compression plate or 4 fixings around the four corners, should they not all apply the same 300kgf?
I would be grateful of any clarification on this.

 

[BiduleOhm]

The root thing you want to do is applying a certain pressure. Since the cell size is fixed you can convert this pressure (force/area) into a force which in the present case is 300 kgf (kg-force; which is an unit we shouldn't use as the proper one is the Newton, 1 kgf =~ 10 N so around 3000 N in our case).

Now to apply a force on something you can take one guy who push 3000 N, or two guys who each push 1500 N, or 3 guys who... So you can see the 3000 N is a total force you want to apply; you can take one big guy who does all of the work, or lot of smaller ones who each does a small part of the work.

But since people need things like sleep, food, etc... it's easier to use threaded rods... ?

NB: kgf.cm and N.m aren't a force over an area (that would be a pressure BTW) but a torque, which is a force at some distance from a point. A pressure wouldn't be N.m but N/m² for example, totally different.

 

[Solarfun4jim]

The root thing you want to do is applying a certain pressure. Since the cell size is fixed you can convert this pressure (force/area) into a force which in the present case is 300 kgf (kg-force; which is an unit we shouldn't use as the proper one is the Newton, 1 kgf =~ 10 N so around 3000 N in our case).

Now to apply a force on something you can take one guy who push 3000 N, or two guys who each push 1500 N, or 3 guys who... So you can see the 3000 N is a total force you want to apply; you can take one big guy who does all of the work, or lot of smaller ones who each does a small part of the work.

But since people need things like sleep, food, etc... it's easier to use threaded rods... ?

NB: kgf.cm and N.m aren't a force over an area (that would be a pressure BTW) but a torque, which is a force at some distance from a point. A pressure wouldn't be N.m but N/m² for example, totally different.

Many thanks, for explaining it in laymans terms...much appreciated.

That focusses me onto one design only.

 

[fafrd]

Distance between screws plays a part too.
My observation is that 5 - 15 inch pounds when cells are near full charge will keep the baby bump under control.
It also removes all gaps between cells after a full cycle or two.

Aren’t you confusing force with pressure?

300Kgf = 660lbs

660lbs over the 54”^2 surface of a cell equals 12.2lbs/inch^2 (12.2psi).

Another easy way to think about how to apply 300Kgf or 660lbs of force is that you want to device that amount of force equally over the number of threaded rods.

4 rods = 165lbs of force applied by the springs on that rod.

If you used 6 rods you’d only want 110lbs of force applied by the springs on each...

 

[ArthurEld]

I'm just telling you how I do it. I never checked the formula.
I don't think it's very important and snugging at full charge would produce the same result.
My fixture is a restraining fixture not a compression fixture.

 

[ArthurEld]

I ordered Loctite 263. Amazon same day for $2.99 extra.
It will be here by 10pm.
I checked into the primer/activator and I am quite sure it is just acetone.
Since I couldn't get any primer fast anyway, I decided to try acetone.

Something else I have been seeing fairly often is seized nuts. I'm not sure why stainless seizes often but it does. Electricity seems to make it more likely. Especially shorts.
Anybody dealing with that issue probably agrees that it is related to threadlocker and stripped threads as well as driving the stud through the bottom of the hole into the inside of the cell.

 

[fafrd]

I ordered Loctite 263. Amazon same day for $2.99 extra.
It will be here by 10pm.
I checked into the primer/activator and I am quite sure it is just acetone.
Since I couldn't get any primer fast anyway, I decided to try acetone.

Something else I have been seeing fairly often is seized nuts. I'm not sure why stainless seizes often but it does. Electricity seems to make it more likely. Especially shorts.
Anybody dealing with that issue probably agrees that it is related to threadlocker and stripped threads as well as driving the stud through the bottom of the hole into the inside of the cell.

Stainless galls easily.

For stainless threaded pipe, you need to use special Nickle-impregnated Teflon tape to prevent galling.

Thinking about this is starting to make me think about getting brass grubscrews and nuts...

If you get your stainless grubscrews nicely locked in and successfully tighter down your lugs to 35 inch-lbs (or whatever), and then the first time you try to remove that lug you rip everything apart, it was hardly worth the effort.

This issue is making me think about Aluminum terminal lugs again - they won’t be cheaper but they will mean that the grubscrews and nuts locking down aluminum lugs onto terminals only need to be tightened once ever (disassembly is done using the set screws).

 

[Hedges]

Stainless galls easily.
...

Thinking about this is starting to make me think about getting brass grubscrews and nuts...

If you get your stainless grubscrews nicely locked in and successfully tighter down your lugs to 35 inch-lbs (or whatever), and then the first time you try to remove that lug you rip everything apart, it was hardly worth the effort.

Turning stainless screw under load might gall, but I'm thinking if stainless grub screw is spun in with loctite and busbar is clamped with brass nut, that might avoid the problems.

 

[texskeet]

Number of cells in the row makes a difference too but about 10 inch pounds at full charge seems to work fine. The cells expand and contract and are forced to make the best use of the available space.
My rods are 3/8"
View attachment 34882

Is this your top balance setup it is neat .

 

[texskeet]

One more thought,many of these cells are convex to start. when you apply pressure only the top bottom get any .pressure looks like the cell expansion is what applies the pressure, how hard will the cells be pushing on each other??? I don't think they will push that hard. snug them up and they will not push that hard

 

[fafrd]

Turning stainless screw under load might gall, but I'm thinking if stainless grub screw is spun in with loctite and busbar is clamped with brass nut, that might avoid the problems.

So brass nuts instead of stainless may avoid the issue - thanks.

 

[ArthurEld]

Is this your top balance setup it is neat .

Yes thanks

 

[ArthurEld]

One more thought,many of these cells are convex to start. when you apply pressure only the top bottom get any .pressure looks like the cell expansion is what applies the pressure, how hard will the cells be pushing on each other??? I don't think they will push that hard. snug them up and they will not push that hard

I will only torque the fixture when the sells are fully charged from now on.
The pressure between cells isn't huge but it is enough to move the cells and damage the threads in the terminals.

Two things move the cells. One is the pressure from inflation when charging. The other is torqueing the fixture.
If the busbars are tight when the cells move it will put stress on these wimpy threads.

I stopped using serrated nuts because they hold too good. The flange diameter is bigger so it causes even more stress on the threads when the cells move.

I am also deciding what torque to use on my terminal screws. I am beginning to think less torque is better so the busbars can slide a little if they need to.

Braided busbars or special busbars that are formed to allow some side movement would have saved my threads.

 

[Fpoet]

I purchased some Permatex activator/primer and am doing some tests these days to see how Permatex threadlockers can work with SS grub screws and nuts (I do not have aluminum to play with). I already had the blue Permatex threadlocker, so that is what I am using now. I am thinking of using the orange type in the terminal holes.

If it works well with the activator, I might also use the blue Permatex in gel version on the top nuts.

 

[ArthurEld]

If you want to get a stud out that is locked in with red thread locker you have to heat it to 450 degrees.
To do that, they recommend touching the stud with a soldering iron. Then turning the stud out while hot.
I don't know how to tell when the stud is 450 degrees.

 

[Bob B]

If you want to get a stud out that is locked in with red thread locker you have to heat it to 450 degrees.
To do that, they recommend touching the stud with a soldering iron. Then turning the stud out while hot.
I don't know how to tell when the stud is 450 degrees.

One of the laser type temp sensors might work .... but that would still be tuff to isolate from reading the iron temperature. I really like those for a lot of things. I keep one in my glove box to walk around and shoot the temp of tires on on my truck when gassing up.

 

[Hedges]

If you want to get a stud out that is locked in with red thread locker you have to heat it to 450 degrees.
To do that, they recommend touching the stud with a soldering iron. Then turning the stud out while hot.
I don't know how to tell when the stud is 450 degrees.

https://www.amazon.com/Mini-Connector-Thermocouple-Temperature-Measure-50-250%C2%B0C/dp/B07MMLY3PZ/ref=sr_1_19

 

[ArthurEld]

https://www.amazon.com/Mini-Connector-Thermocouple-Temperature-Measure-50-250%C2%B0C/dp/B07MMLY3PZ/ref=sr_1_19

Hedges you always come up with something interesting. Those look similar to the temperature sensors that connect to my BMS.
I probably could use my BMS temperature probe but it might melt.

Another possibility would be to heat it pretty hot and try to get the screw out. If that doesn't work, heat it a little longer and try again.
It wouldn't surprise me if the stud came out without heat so I would try that first.

It is very easy to break the hex head of the stud so, two nuts tightened together on the stud would be a smarter way to get the stud out.

And, it would also be possible to drill the stud out with a drill the same size as the thread ID.

 

[BiduleOhm]

450 °C or °F?

 

[Fpoet]

If you want to get a stud out that is locked in with red thread locker you have to heat it to 450 degrees.
To do that, they recommend touching the stud with a soldering iron. Then turning the stud out while hot.
I don't know how to tell when the stud is 450 degrees.

The red is out of the question for me. I do have braided busbars, so my goal is only to prevent loosening from vibrations (the battery is for a van). Apparently, the Permatex orange is 3X stronger than the blue, but you can still break the bond with hand tools.