Hi Marcus, My primary job at Cat was designing the electrical system, wiring harnesses, how they were attached and the components attached to the harnesses - switches, instruments sensors, and so on. But bolted joint principles apply just as I have stated.
What soft materials are you talking about? Soft and plastic are different. Lead, tin, antimony, copper, aluminum, while they are not steel hard, won't creep and everything I said applies to them as well. Plastic and rubber, composites possibly, are bad in a bolted joint. I don't understand why you think a Nodlock has done anything . What exactly do you see that proves it? When the joint is tight, it is simply the stretched bolt caused by applied torque that makes it tight. I am sure the Nordlock does something when the joint comes loose, but the the Norldock just sits there doing nothing until that happens, then something has gone very wrong which is the root cause of the problem and what needs to be solved. Instead of messing around with stuff that tries to help after the joint has failed, make it so the joint won't come apart to begin with. Use some thread locker if nothing else. What research would you have me look at on dielectric grease versus conductive grease? A citation would be helpful. I don't feel compelled to look this up. If you have some documentation to share that can raise my awareness I will check it out. I believe I said use a conductive grease if you are so inclined, and skip the dielectric. Dielectric means resists he passage of current but does not reduce the propagation of electromagnetic fields - http://whatis.techtarget.com/definition/dielectric-material. Why would you like that in an electrical current carrying joint? BTW NoAlOx is conductive not dielectric. The whole claim of it is that it enhances conduction. I would think you guys might like a silver bearing paste. Any grease will reduce corrosion by excluding moisture. It is dissimilar metals and H2O that causes corrosion, not dissimilar dry metals. put it together dry and smear grease on after torquing will exclude H2O, a good thing, but not better than a tight dry joint. Vaseline is not grease, though it is greasy and a lubricant. Petroleum jelly the proper name is a good hint it will burn. The main point about grease outside a joint is it is sticky. On Fri, Jan 10, 2014 at 7:08 PM, Marcus Reddish <[email protected]>wrote: > Michael, > > The joints on a Caterpillar are simple steel to steel using a steel bolt > and a steel nut with, perhaps, a steel washer or two. Make it stout and > crank it tight. Simple. > > Battery connections, in comparison, are quite complex with their use of > multiple soft metals and ridiculously low torques. > > Please also notice that the purpose of the joint is entirely different, > with conductance instead of mechanical adherence being the key goal. > > Nordlocks DO work. Given their great expense, nobody would use them if > they didn't. Lock washers they are not. > > Somebody posted a picture of a typical early OEM pack where they did almost > everything wrong. They dug through the bolt bin and came up with a zinc > plated body bolt. Joined dissimilar metals without a protective paste (NOT > Vaseline it's flammable!!). Used leaky cells with crap chemistry (IMHO). > And sometimes fail to even tighten them correctly. Other OEM packs might > be perfectly engineered. > > Please research the use of dielectric grease to protect electrical > connections in Industrial, marine, military, aerospace, automotive, and > household applications. It greatly reduces corrosion that WILL happen. > OEM battery pack is perfect example. If those had a light coat of > dielectric grease they would look perfectly brand new when it was wiped > off. Do some research and let me know if you find a single instance of it > causing a problem vs. the array of problems that can arise when electrical > grease is not used. It is cheap insurance. > > Best regards, > > Marcus > > > > > > > > > On Fri, Jan 10, 2014 at 10:58 AM, Michael Ross <[email protected] > >wrote: > > > Yes Evan, you have it exactly right. The popularity of lock washers is > > without merit. I will give you a caveat though, I am talking about > joints > > where there is all metal in the sandwich. More detail below on > > non-metallic stuff. > > > > I believe you are wrong about the Toyotas at leas with all metal joints. > > Tie rod ends are not castellated on my car, they are big and torqued > hard > > with a tapered fit that really does the work. There is no thread locker > > that I have seen, and no nylocks. If you show me I will believe, but I > do > > my own wrenching and have not seen any. I have seen some deformed nuts > > where they whack the end of the nut into an ellipse for use on exhaust > > stuff that has extreme thermal cycling). There are things like battery > > hold downs - not an all metal joint, but I am pretty sure even these are > > not nylock or deformed. > > > > You are right to press me on this - Why on earth are there all these lock > > washers used? Why do so many people think they are useful? Heck, > Nordlock > > may be quite sincere in thinking their fancy washers do something. Part > of > > this is tradition that is self sustaining - they are everywhere so the > must > > be good, right? Also, lock washers do get applied places where, > > unfortunately they help, because of design flaws (usually material > > selection). In every case they are a bandaid for a joint that could have > > been better, but maybe cost too much better, or there wasn't time to do > > better, and besides, everyone uses them, right? > > > > That does not change the fact that a split lock washer, or a Nordlock > is a > > waste of money in a joint that is tight enough not to come loose. And > you > > can design or modify joints so they don't come loose. > > > > Here is why I think I know what I am talking about: > > I worked as a mechanical engineer for Caterpillar. You will not find them > > on a Caterpillar track type tractor, front end loader, or backhoe loader > > (these three products I have done design work on). I have a copy of the > > bolted joint analysis and design specs for Caterpillar in the 1990's - no > > lock washers are to be used - ever - for metallic joints. This spec is > the > > bible for getting bolted joints to survive in the absolute worst > > conditions. I doubt if Cat has a part number for a split lock washer, > > though you never know what a green engineer might do. I have done > > mechanical work primarily on Toyotas in modern time (VW, Audi, Porche, > > Subaru, & Honda in the 1980's) and there are no lock washers used on > them. > > > > Part of what confounds common understanding about lock washers is that > they > > will paper over joints coming loose that are prone to become loose: > > There are joints where, due to unfortunate design, materials that creep > are > > necessary, or in other words they compress with time and thermal cycling > > (plastics and other composites). In these cases you really should use > very > > light clamping forces, align the parts with pins and other features, and > do > > not apply the assembly in the presence of any thermal cycling or > vibration > > of any kind. Think electronic components for use indoors only. > > > > There are a variety of washers for special purposes where clamping force > in > > not a primary concern. Star washers for instance can pierce oxides and > > plating to improve low voltage, low current connections. Metallic > inserts > > are used in plastic part design to remove a threaded interface in > plastic - > > because plastic will deform with constant force and thermal cycling. If > > you can make very deep thread engagement with plastic it can work with > > special threads (think thin sharp threads like a drywall screw). All > sorts > > of weird stuff is needed when the joint has materials that are plastic in > > behavior, not stable and elastic as are metal joints. Look in a Richco > > catalog for all manner of plastic fasteners. Penn Engineering for metal > > inserts. > > > > Bottom line you will see lock washers in use, but they may not do > anything > > or they may be covering up a bad design fault. Taking what you see on a > > plastic assembly and using it on a metal assembly is bad practice. > Happens > > all the time, and now we are all used to it. Reminds me of Phillips > heads > > which Henry Ford put into service specifically because they cam out and > > strip the cross so as not to mess up sheet metal. Or the QWERTY keyboard > > designed to exercise out littler fingers, not to promote efficient fast > > typing. This s*** just happens > > > > Returning to battery terminals on EV's: > > I haven't seen all the various battery connection means. Some may suck > and > > need something to keep them from loosening. None of my batteries are > like > > that. If you have all flat metal in your battery terminal stack, and your > > screws can be torqued well, then you don't need any lock washers. But, > > each battery type and EV needs to be taken as a separate case. > > > > I redid my pack of 38120s. These have a stamped metal cap on each end > with > > t tapped hole. These were not torqued to even half what they should have > > been, came loose with barely finger tightness. I took them all apart, > got > > rid of the lock washers (they have a tool large ID so there is an area of > > unnecessarily high stress between the screw heads and the flat washer). > > This is nit picky, but I have no reason to cut corners. Then I put them > > all back together and tightened them using an inch pound torque wrench > > because is has small enough resolution to do a good job on the M5 screws. > > I am annoyed that they are Phillips screws and might replace them with > > socket head cap screws later. I used some little SS SAE washers that are > > not the best choice. > > > > I have a pack of 40Ah Thundersky cells. these have aluminum pads with a > > tapped holes for terminal contact. I am going to get some screws that > are > > long enough to get good thread engagement all the way to the bottom of > the > > tapped holes. These did not have lock washers installed, but properly > > sized flat washers. I didn't pay attention to if they were torqued > right. > > It is hard to tell, and it was all coming apart anyway. I will torque > > them to the correct torque for aluminum threads. > > > > Another pack I have is 19650 cells (like fat AAs with flat ends) which > have > > no screw fasteners at all. These have strips of stainless laid across > the > > ends and resistance welded to the cell ends. They are series strings to > > get the voltage, of numerous parallel cells to get the capacity. I like > > this for cheapness. They may be assembling the packs with welding > robots - > > or they could anyway. The bad part is if a cell goes south, it is hard > to > > replace. > > > > As has been noted, the current does not travel the bolt and threads, but > > goes through the flats where the terminal, strap or bus bar contacts the > > battery terminal - I think a thread locker is probably fine to use if one > > is are hesitant to torque fully. But it is unnecessary if you have full > > thread engagement (>1.5 times the bolt diameter) and torque properly. > Just > > torque it. A lock washer is simply not an effective means for anything > in > > a metal joint. > > > > > > On Fri, Jan 10, 2014 at 5:05 AM, Evan Tuer <[email protected]> wrote: > > > > > On Thu, Jan 9, 2014 at 9:27 PM, Michael Ross <[email protected] > > > >wrote: > > > > > > > > > > > Please explain what I got wrong here. > > > > > > > > > > > The real world? According to you, there is no reason for ANY sort of > > > locking washer or nut to exist. > > > > > > > > > > > That's clearly not the case. Even in your > > > Toyota, there will be plenty of fasteners Loctite'd in, probably a few > > > Nylocks, perhaps even a few castlated bolts lurking somewhere. > > > > > > The battery terminals we work with are not ideal either, though I > > maintain > > > the environment is not bad enough to warrant Nord-Locks or anything > that > > > extreme. YMMV. > > > -------------- next part -------------- > > > An HTML attachment was scrubbed... > > > URL: < > > > > > > http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20140110/9b80a1c2/attachment.htm > > > > > > > _______________________________________________ > > > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > > > http://lists.evdl.org/listinfo.cgi/ev-evdl.org > > > For EV drag racing discussion, please use NEDRA ( > > > http://groups.yahoo.com/group/NEDRA) > > > > > > > > > > > > -- > > 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. Ross > > (919) 550-2430 Land > > (919) 576-0824 <https://www.google.com/voice/b/0?pli=1#phones> Google > > Phone > > (919) 631-1451 Cell > > (919) 513-0418 Desk > > > > [email protected] > > <[email protected]> > > -------------- next part -------------- > > An HTML attachment was scrubbed... > > URL: < > > > http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20140110/dcddc853/attachment.htm > > > > > _______________________________________________ > > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > > http://lists.evdl.org/listinfo.cgi/ev-evdl.org > > For EV drag racing discussion, please use NEDRA ( > > http://groups.yahoo.com/group/NEDRA) > > > > > > > -- > Marcus Reddish > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: < > http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20140110/0ea37afd/attachment.htm > > > _______________________________________________ > UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub > http://lists.evdl.org/listinfo.cgi/ev-evdl.org > For EV drag racing discussion, please use NEDRA ( > http://groups.yahoo.com/group/NEDRA) > > -- 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. Ross (919) 550-2430 Land (919) 576-0824 <https://www.google.com/voice/b/0?pli=1#phones> Google Phone (919) 631-1451 Cell (919) 513-0418 Desk [email protected] <[email protected]> -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.evdl.org/private.cgi/ev-evdl.org/attachments/20140111/cee58844/attachment.htm> _______________________________________________ UNSUBSCRIBE: http://www.evdl.org/help/index.html#usub http://lists.evdl.org/listinfo.cgi/ev-evdl.org For EV drag racing discussion, please use NEDRA (http://groups.yahoo.com/group/NEDRA)
