free panniers and a riding suit for list members

[Eric L. Green]

On Sat, 6 Aug 2005, Ed Chait wrote:

>> To make it go as smoothly as possible, make sure you have a shim pack >> from Fred and a 1/4" torque wrench with a long extension bar so that > > Doesn't using an extension on a torque wrench change the leverage and affect > the value you are torquing to?

Nope. Not unless it has an offset in it. Torque consists of force applied over a distance. The distance in this case is the distance between where the force is being applied (i.e. at the bolt) and a 90 degree line through the end of the torque wrench handle. As long as this distance doesn't change, the torque applied with a given input to the handle doesn't change. Thus as you can see, simply adding an extension (without putting a u-joint or some other such thing into the equation) doesn't change the torque applied with a given input to the handle... it just moves the point where the force lines intersect downwards a bit. -E

[Ed Chait]

> On Sat, 6 Aug 2005, Ed Chait wrote: >>> To make it go as smoothly as possible, make sure you have a shim pack >>> from Fred and a 1/4" torque wrench with a long extension bar so that >> >> Doesn't using an extension on a torque wrench change the leverage and >> affect >> the value you are torquing to? > > Nope. Not unless it has an offset in it. Torque consists of force applied > over a distance. The distance in this case is the distance between where > the force is being applied (i.e. at the bolt) and a 90 degree line through > the end of the torque wrench handle. As long as this distance doesn't > change, the torque applied with a given input to the handle doesn't > change. Thus as you can see, simply adding an extension (without putting a > u-joint or some other such thing into the equation) doesn't change the > torque applied with a given input to the handle... it just moves the point > where the force lines intersect downwards a bit. > > -E

Of course, that makes sense. For some reason, I had the mental image of an extension applied to the handle of the torque wrench and a 90 degree angle. D'oh!!!!! ed, just call me homer A17

[Rick McCauley]

I took mechanical training under 3 instructors. All 3 taught that an exstension will alter actual torque getting to the bolt. I could never understand it, but that's what they taught. Rick A17

> > Nope. Not unless it has an offset in it. Torque consists of force applied > over a distance. The distance in this case is the distance between where > the force is being applied (i.e. at the bolt) and a 90 degree line through > the end of the torque wrench handle. As long as this distance doesn't > change, the torque applied with a given input to the handle doesn't > change. Thus as you can see, simply adding an extension (without putting a > u-joint or some other such thing into the equation) doesn't change the > torque applied with a given input to the handle... it just moves the point > where the force lines intersect downwards a bit. > > -E

--------------------------------- Start your day with Yahoo! - make it your home page [Non-text portions of this message have been removed]

[Doug Herr]

On Sun, 7 Aug 2005, Rick McCauley wrote:

> I took mechanical training under 3 instructors. All 3 taught > that an exstension will alter actual torque getting to the > bolt. I could never understand it, but that's what they taught.

Maybe the torsional energy delivered to the extension is not fully passed on to the nut/bolt. Seems like it would be a minimal issue tho. -- Doug Herr doug@...

[Eric L. Green]

On Sun, 7 Aug 2005, Rick McCauley wrote:

> I took mechanical training under 3 instructors. All 3 taught that an > exstension will alter actual torque getting to the bolt. I could never > understand it, but that's what they taught.

I'm sorry that my description of the physics involved is so pathetically inadequate (it really worked better back when I was teaching this stuff when I could draw a picture on the chalkboard and then show some physical examples), but anyhow, physics says differently. Consider the whole notion of a "foot-pound". Let's say you're torquing a bolt to 25 foot-pounds. That means that if you have a 1-foot-long wrench from the center of the socket to the end, parallel to the ground, and hang a 25 pound weight from the other end of the wrench, you're applying 25 foot-pounds of torque to the bolt. Now, let's put an extension between the socket and the wrench. The distance from where the weight attaches to the wrench and a line drawn through the center of the socket is *still* 1 foot. So you're *still* applying 25 foot-pounds of torque to the bolt. Torque is force applied over a distance. That is how it is defined in physics. Force is the same (25 pounds), distance is the same (one foot), thus torque is the same, by definition. What may have confused your instructors is the notion of an offset extension, i.e., one which actually makes the distance from the end of the wrench to the center of the bolt longer or shorter. This will affect the amount of torque that a given force at the end of the wrench is applying to the bolt, since you just changed the distance part of the above equation. Also, if you hold the extension to stabilize it this obviously changes things since you are now applying a force other than to the end of the wrench. Other than that, the effect of an extension is minimal (since it's unlikely that the extension is *exactly* vertical it may change the distance by a tiny bit, but probably not by enough to be noticable within the precision of the torque wrench). -E

[Rick McCauley]

I just thought of something that backs up the idea that an extension makes a difference. My Uncle is a mechanic by trade, and has been for just under 40 years. He has a set of wheel lug extensions that vary in diameter and length. You choose the extension based on lug bolt diameter, rim, material etc. The same air gun is used, but no matter how much air pressure is put to the gun, the lugs get the correct amount of torque. I can't remember for sure but I think they are available through MAC or Snap-On. I wouldn't even try to figure out how they work, but if somebody knows of a MAC or Snap-On Rep, maybe it would be interesting to ask. Rick A17 Doug Herr wrote:

On Sun, 7 Aug 2005, Rick McCauley wrote: > I took mechanical training under 3 instructors. All 3 taught > that an exstension will alter actual torque getting to the > bolt. I could never understand it, but that's what they taught. Maybe the torsional energy delivered to the extension is not fully passed on to the nut/bolt. Seems like it would be a minimal issue tho. -- Doug Herr doug@... __________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com [Non-text portions of this message have been removed]

[scott quillen]

I spent 9 years of my 20 in the Air Force wrenching on Minuteman ICBMs. The Air Force is pretty picky about nuclear surety and how its Minutemen are maintained and we were trained to use sockets, crows feet and extensions with our torque wrenches. The particular things we were taught about torque wrench use: 1. Always store a torque wrench at its lowest setting. 2. Always "exercise" a torque wrench at its lowest setting before use by clicking it at least 4 times in each direction. 3. Never drop a torque wrench...if it happens, don't use it again until it's been recalibrated by the PMEL (Precision Measurement Equipment Laboratory). 4. The lowest 20% of a torque wrench's range is the least accurate - always choose a torque wrench with sufficient range to avoid using this lowest 20%. 5. Always apply torque is a slow, smooth motion until the proper torque is achieved - AVOID JERKING the torque wrench when applying torque as it is easy to over-torque the fastener when jerking. 6. The fastener should be turned at least 1/4 turn before the desired torque is achieved, to ensure the fastener is not over-torqued. In other words, if the wrench clicks as soon as it is turned, chances are good the fastener is over-torqued. 7. NEVER used a cheater bar or extend the length of a torque wrench - THIS will affect the applied torque. 8. Torque wrench accuracy can be affected by temperature extremes. Always store torque wrenches at "room temperature" prior to use. In Montana, we often worked in temps WAY below zero, so we stored our torque wrenches in a heated maintenance vehicle or in the "soft support building" or in the LER (lower equipment room)prior to use. I think that about covers it. Scott --- Rick McCauley wrote:

> I took mechanical training under 3 instructors. All > 3 taught that an exstension will alter actual torque > getting to the bolt. I could never understand it, > but that's what they taught. > > Rick A17 > > > > > > Nope. Not unless it has an offset in it. Torque > consists of force applied > > over a distance. The distance in this case is the > distance between where > > the force is being applied (i.e. at the bolt) and > a 90 degree line through > > the end of the torque wrench handle. As long as > this distance doesn't > > change, the torque applied with a given input to > the handle doesn't > > change. Thus as you can see, simply adding an > extension (without putting a > > u-joint or some other such thing into the > equation) doesn't change the > > torque applied with a given input to the handle... > it just moves the point > > where the force lines intersect downwards a bit. > > > > -E > > > > > --------------------------------- > Start your day with Yahoo! - make it your home page > > > [Non-text portions of this message have been > removed] > > > > Archive Quicksearch at: >

http://www.angelfire.com/ut/moab/klr650_data_search.html

> List sponsored by Dual Sport News at: > www.dualsportnews.com > List FAQ courtesy of Chris Krok at: > www.bigcee.com/klr650faq.html > > > Yahoo! Groups Links > > > DSN_KLR650-unsubscribe@yahoogroups.com > > > > >

__________________________________________________ Do You Yahoo!? Tired of spam? Yahoo! Mail has the best spam protection around http://mail.yahoo.com

[fasteddiecopeman]

ONLY if the force is LATERALLY applied (a longer sideways force...). Ed

> Doesn't using an extension on a torque wrench change the leverage and

affect

> the value you are torquing to? > > I really don't know, so I better ask before I do my first valve adjustment. > > ed > A17

[April Neave & Norm Keller]

Someone posted:

>I took mechanical training under 3 instructors. >All 3 taught that an

exstension will alter actual >torque getting to the bolt. I could never

>understand it, but that's what they taught.

I seldom break my rule to not pronounce directly on a point of view but in this case will do so. Your instructors were wrong. As long as the torque is axial there will be no reduction regardless of the length of extensions. If the torque is applied non-axially (that is to say, out of line) the torque will be altered. This is why it is quite acceptable to step out, down and back into line again to go around an interference and still not alter torque. Offset extensions are in common use for many applications. It is important to recognize that torque is the measure of twisting effort applied between two points. In other words, there must be an originator and receiver for the torque to be discussed. Speed needs have no effort applied and torque needs have no movement. Movement and torque taken together are power. If you search the archives much has been written with regards tightening of fasteners. One point which should be clearly understood by anyone doing service work is that the purpose of torquing a fastener is to create the specified degree of tension in the fastener. The tension will result in the desired stretch of the fastener and the desired clamping force will be applied to the parts in question. Torque tightening is a relatively inexact, and so inefficient, method of arriving at the desired tensioning of the fastener. A much more efficient method is the "torque turn" method used around large equipment for more than 60 years to my knowledge. This same technique has appeared in the automotive industry as "torque to yield" . Both names refer to a method in which the fastener is snugged up and then turned a specified number of degrees in order to reach the desired tensioning of the fastener. If a fastener is to be tightened by turning a specified number of degrees, the designer must decide how much tension and/or clamping force is needed to be provided by the fastener. The amount of tension is easy to arrive at since it is simply the amount of pull required to remove all the slack from the assembly and then to proceed to stretch the fastener by a determined amount. The determined amount can be calculated from the thread pitch and the compression of the threads under the resulting load. Turn a given bolt or screw tight, and then turn a specified number of degrees and a certain tension will be achieved. Simple! To achieve the same precision of tensioning through torque is much more difficult. The same intent is there which is to achieve the same number of degrees of turn but the method makes this much more difficult to achieve. In order for the specified number of degrees of turn to be achieved, the effort to turn the fastener must be predicted. Since this effort must both apply tension through the screw thread pitch (easy to calculate) and overcome friction (very difficult to predict) the method must be less accurate than that which addresses the problem directly by simply turning a determined number of degrees. FWIW, now back to getting over vacation and back to business in the morning.... (VBG) Norm

[April Neave & Norm Keller]

>MAC or Snap-On Rep, maybe it would be interesting to ask.

The extension in question is usually referred to as a "torque stick" or the like name. Accutorq were the first to market but several others have picked up the same principle. The idea is that the extension has a certain resistance to being twisted and so will transmit up to a certain amount of twisting force (torque) before the extension begins to twist. After the threshold torque (twisting force) has been applied the extension will wind up and so will require much more rotation of the driving end in order to continue to increase the twisting force. If one were to put a hand wrench onto one end the extension will wind up and then continue to apply torque increasingly until the extension fails. Any increase in torque much above the designed torque requires quite a lot of rotation due to the "give" and winding up of the extension. When using an impact gun (air wrench) the torque bar will "soak up" the impacts of the wrench and so tend to limit the applied torque to that specified. This works well as long as an impact gun with too much power is not used. For this reason the makers provide a procedure to ensure that one doesn't over power the extension. Torsion bars are commonly used as suspension springs in many automotive and light truck applications. The first Honda 450 motorcycle was a wonder of design due to its torsion bar valve springs. Now I really had better get to the chores (LOL) Norm