Hi Bill, >From my own experience with non-electrical bolted joints, re-torquing is not ever necessary, given the torque is right to start with, the parts fit right, are of the proper grade, and clean.
The only reason for the forces to drop is if there is a compliant material in the joint that takes a compression set. Compression set due to thermal cycling is about the only way to lose clamping force. There might be a way if there are foreign materials present. I am not saying you are wrong, but I do want to know why it has happened. Do you have any ideas? What mechanism is allowing the components of the joint to compress enough allowing the screw to back out? The whole idea of proper joint design and selection of clamping force(the torque applied) is to ensure that under all operating and storage conditions, including thermal cycling, that sufficient clamping is always remaining and no loosening can occur. I am very skeptical. Also the torque to release a joint gives no indication of the applied torque or the remaining clamping force. You simply cannot reliably measure that. NoALOx is only useful for aluminum according to product literature, the joint I discussed has only copper and stainless in it. The theory of this stuff has an appeal - is there any evidence? I have a hard time believing in aluminum surfaces that are not oxidized (except in a vacuum). I would like hear what people know about the electrical properties of clamped joints. I don't know much about that. I do know a bit about switch contacts, but the forces are much smaller (and yet they function somehow, with no gook in between). I am from Missouri on this topic. I apologize to all, I have probably raised two religious topics. But I have not been around the block on these in this context. On Mon, Jan 6, 2014 at 10:49 AM, Bill Dube <[email protected]> wrote: > You have to sand the terminals and immediately apply NoAlOx, just like > Mark says. A thin layer is best as a thick layer will slowly ooze out and > the terminal will become loose. > > Re torquing is needed, but probably not every 10k miles. Likely just the > first 5k to 10k and then maybe at 30k or 40k. > > Bellville washers help. > http://en.wikipedia.org/wiki/Belleville_washer > > Bill D. > > On 1/6/2014 7:22 AM, Michael Ross wrote: > >> I recently took apart a nice little OEM battery pack and every terminal on >> it was barely hand tight. I reassembled with SS socket head screws >> instead >> of the Phillips screws, and torqued the 5mm bolts to spec. All you need >> to >> do is torque them right and they will not loosen. Do not use lock washers >> as they compromise the clamping force. If you look at bolted joints on >> high >> quality equipment you will find properly designed joints with no >> lubrication or thread-locker - they just torque the right. I worked for >> Caterpillar and can vouch for their practices - needed to survive the >> worst >> vibration environments imaginable. My Toyota cars over the last 30 years >> are all produced this way. I don't use conductive grease, I just go with >> clean and tight. >> >> For reference: >> >> 1 N m = 8.8in lb = 0.74bft lb >> >> I tightened the 5's to 35 in lb (4 Nm). >> >> Unfortunately, there are a lot of units for measuring torque. Inch >> pounds >> are best for the small wrenches we have in the US. >> >> My joints were the terminals of 32120 cells, SS M5 screws, with nickel >> plated copper straps, and stainless steel flat washers (lock washers >> thrown >> away). I am not sure what the terminal with the tapped threads is made >> from. It is s tamped and formed part, maybe SS, but could be a plated >> brass or copper... >> >> On Mon, Jan 6, 2014 at 7:26 AM, Mark Hanson <[email protected]> >> wrote: >> >> Hi Folk's, >>> last night a overvoltage battery balancer #22 shut down the charger at >>> 4.0V. At first I thought it was a bad OV balancer detector but after >>> replacing the circuit it still did it so I put a scope across the battery >>> cell and noticed the charging pulsed waveform going from 3.3V to 4.0V 60 >>> hz >>> when adjacent cells were fairly solid (signifying a high impedance >>> condition). I thought I had a bad cell but after sanding under the >>> copper >>> strap & adding 3M dielectric grease & torquing back down, it charged >>> perfectly with no faults, back to low impedance. I found a few other >>> battery terminal bolts not tight after 20k miles (even with sealing paint >>> on terminal bolts CALB 130). So it's best to tighten terminal bolts on >>> lithiums every 10k miles it seams. I used to tighten terminal bolts on >>> old >>> lead GC batteries every 500 miles but didn't think it was necessary with >>> lithiums but apparently they need it as well just less often. >>> Best Regards,mark >>> -------------- next part -------------- >>> An HTML attachment was scrubbed...SNIP >> >> -- Put this question to yourself: should I use everyone else to attain happiness, or should I help others gain happiness? *Dalai Lama * Tell me what it is you plan to do With your one wild and precious life? Mary Oliver, "The summer day." To invent, you need a good imagination and a pile of junk. Thomas A. Edison<http://www.brainyquote.com/quotes/quotes/t/thomasaed125362.html> A public-opinion poll is no substitute for thought. *Warren Buffet* Michael E. 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