From: John De Armond Subject: Re: Torqued Yer Hitch Bolts Lately? Date: Fri, 29 Oct 1999 03:41:39 EDT Newsgroups: rec.outdoors.rv-travel "E. Myers" wrote: > > On our last long trip I started noticing a "push-pull" type feeling whenever > I stopped. After parking I got to inspecting the system and found the ball > nut had come loose on the hitch even though it had a lock washer on it. > Arriving home I replaced the ball and the shaft was worn probably 20% > through. I carry a 16" crescent just to tighten that nut but had failed to > keep an eye on it. Won't miss it again! > Ed Seeing all these tales about loose fasteners, I thought I'd mention something that's like a 3rd hand to a race mechanic - Loctite. This is a specialized single component adhesive that cures in the absence of air (anaerobic) and is applied to fasteners (bolts, nuts, screws, etc) to lock the threads. Only the part actually within the threads and thus deprived of air hardens. The rest remains liquid and can be wiped away after assembly. Loctite comes in grades that are color coded. Blue is ordinary strength and provides about the same locking action as a star washer. The fastener can easily be loosened with hand tools. Red is the next step up. It is quite strong and requires considerable force to break loose but can be removed with hand tools without heat. This is the grade I use for all types of fasteners with a shank diameter equal to or smaller than 3/4". Larger fasteners are adequately locked with blue; red may be impossible to remove without heat on the larger fasteners. Green is the strongest. It normally cannot be broken loose with hand tools. An air impact wrench will break free smaller fasteners. Larger ones must be heated. I use green in high stress, high vibration areas such as suspension fasteners. Green is also known as bearing and bushing lock because it can be used to lock a loose bearing in its housing and to secure bushings. I use the brand name Loctite because I have found that brand to be far superior to competing brands. Another technique used in the racing field that was adopted from the aviation world is drilling fasteners for safety wire. I drill and safety wire any fastener whose failure would cause a hazardous condition (single point failure.) Trailer hitch bolts fall in this category. Pre-drilled aerospace-grade fasteners (AN- designation, 180,000 psi yield strength) can be had surprisingly inexpensively from companies like Alexander Aeroplane (800 831-2949) in Atlanta who cater to the experimental/home built airplane market. Racing supply companies such as JEGS and Summit Racing sell jigs that make drilling fasteners very easy. All the above companies sell safety wire pliers that make applying safety wire very simple. These pliers contain a leadscrew in the handle that, when pulled, twists the wire to the proper tightness. American-made pliers cost about $60. Chinese clones go for about $15-20. One other thing I might mention. Standard (non-metric) bolts are graded according to strength. The system ranges from Grade 2 (cheap, weak) to Grade 8 (about 90,000 psi yield strength, if my memory serves). The caps of the bolts are marked with radial slashes that designate the grade. There are 2 less slashes than the grade number. In other words, a Grade 8 bolt will have 6 slashes; a grade 5 will have 3 slashes. When I had a Class III hitch mounted to my catering Step-Van, I noticed that the (formerly) reputable hitch shop used Grade 2 bolts to attach the hitch to the chassis. This was unacceptable to me. Before using the hitch, I replaced the fasteners with Grade 8 bolts. These Loctited bolts have never required retorquing and have never loosened. I suspect that these cases where fasteners are repeatedly loosening and requiring retorquing are overloaded and are stretching. Replacing the fasteners with Grade 8 bolts should solve the problem. From: John De Armond X-Source: The Hotrod Mailing list Date: May 1994 Subject: clearance for Locktite? X-Sequence: 8538 Found this on the net. Thought it might come in handy. John ---------------------------------------------------------------- Greg Lewis (gregl@zimmer.CSUFresno.EDU) wrote: : How much clearance should one allow for a cylindrical shaft and hole : set with Loctite?... ... and how long is that piece of string anyway? :) How much you can get away with depends on which particular flavor of Loctite you're using. Optimally, the gap should be between 1 and two thou all the way around. Incapable of leaving it at that, however, I'll throw in the table from the current Loctite catalog on the end of this posting. Yes, I know it's overkill but someone else might find it useful. It's not readily available unless you call Loctite for the data sheets or go find a supplier with some spare catalogs. Tim -- Tim Kirby --------- Cray Research Inc., Eagan, MN, USA ---------- trk@cray.com Disclaimer: Cray didn't say this... I did... ------------------------------------------------------------------------------ If all else fails, Immortality may always be assured by spectacular error(JKG) ------------------------------------------------------------------------------ Loctite Retaining Compounds --------------------------- Notes: + The gap fills are all *maximum*. According to the guy at Loctite when I asked these very questions some time ago, the optimum gap is between 0.001" and 0.002" (0.002 to 0.004 diametral) for any of theses adhesives. + This table refers to the *retaining compunds*, not *threadlock compunds* + The viscosity "Low/Med./High" is from the descriptions for each product + The '660' is referred to as 'Quick Metal', considered a non-running product + If you're using another brand (is there any other ? :) you're on your own. + Cure Speed assumes no accelerator is used. Activators/accelerators may improve the gap filling capabilities slightly as well as ensuring proper/ faster curing respectively. If you need to accelerate it, talk to your dealer; I don't have any specific numbers. + Primers are useful on inactive surfaces such as aluminum, black oxide, stainless steel and thermoset plastics + Remember... *CLEAN CLEAN CLEAN* !!! ----------------------------------------------------------------------------- Compound No. 609 620 635 640 642 660 675 680 ----------------------------------------------------------------------------- Color Green Green Green Green Green Silver Green Green *Maximum* Gap Fill 0.005" 0.015" 0.010" 0.007" 0.012" 0.020" 0.005" 0.015" (Diametral) Viscosity V.Low High High Med. Med. !!!! Low Med. (cP) 125 7000 2000 600 500 1200000 125 1250 Shear (psi) 3000 3000 4000 3000 3500 3000 3000 4000 Temp Range(F) Low -65 -65 -65 -65 -65 -65 -65 -65 High 300 450 300 400 350 300 300 300 Cure Speed Fixture (Min) 10 30 60 60 5 10 20 10 Full (Hrs) 24 24 24 24 24 24 24 24 Primer T or N T T T T or N N T T ----------------------------------------------------------------------------- Uses: 609: spindle bearings, lip seals, bearing races 620: engine cylinder liners, heat exchanger tubes 635: gears, pulleys, fans, collars, rotors, sprockets, cams and flywheels to shafts. 640: bushings and sleeves, rotors to shafts 642: bushings in manual transmissions 660: worn shafts, worn housings, worn end bells, bearing spinouts, wallowed keyways, wallowed splines 675: oil impregnated bushings, drill bushings 680: gears, wheels, pulleys, cams, collars, flywheels, sprockets, and rotors to shafts, replacement bearings in worn housings or on worn shafts. |
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