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 Subject: Newton's Law Category: Science Asked by: brian0575-ga List Price: \$10.00 Posted: 26 Jun 2003 01:03 PDT Expires: 26 Jul 2003 01:03 PDT Question ID: 221870
 ```When I was a young man I was taught that every action has a reaction. If I use an electric drill to bore a hole - and the drill bit becomes 'stuck' the electric drill tries to twist my arm. If I use an 'air powered' mechanics' gun I am able to undo ever the tightest nuts/bolts e.g. lorry wheel nuts, with hardly any effort - apart from a 'machine gun' noise. My query - WHERE HAS THE REACTION GONE THAT NEWTON SAID THERE WOULD BE? Regards, Brian Allanson.```
 Subject: Re: Newton's Law Answered By: krobert-ga on 29 Jun 2003 17:32 PDT
 ```What seemed to be lost in the comment/conversation in this question are three things, keeping in mind that these tools are called IMPACT wrenches (at least in the USA): 1) The wrench works by taking advantage of a large angular momentum (the impact). 2) Angular momentum is conserved (Newton's second law). 3) Torque is balanced (Newton's third law of motion... when you try to turn the lorry nut, the nut pushes back!) The energy that drives the wrench is the energy released by air that is decompressing through a small turbine like device that turns the shaft of the impact wrench. Now, despite the few moving parts in an impact wrench, it is an extremely complicated device to examine analytically. So, right here, lets take the spin-up of the wrench out of the picture (this is the small torque that you feel when you activate the wrench in mid air)... let's assume that the wrench is simply operating in a steady state. On this spinning shaft are tiny little hammers (see the following link): http://groups.google.com/groups?q=%22impact+wrench%22+hammers+turbine&hl=en&lr=&ie=UTF-8&oe=UTF-8&safe=off&selm=387dd777.1689053%40news.iconnect.net&rnum=1 As stated in the above link, these tiny little hammers are spun around this shaft and are supported on a yoke. Due to centripetal force, the hammers are pulled away from the center axis. This position farthest away from the center axis gives them a large angular momentum (dependent on the spin up of the tool). When the wrench encounters a nut (which trys to slow down the shaft), the hammers are pulled inward, smack a yoke and give the nut a very large impulse of angular momentum. This impulse takes advantage of the concept of stick/slip friction and can "break loose" a very tight nut. The "breaking loose" occurs when the impulse is able to overcome the sticking friction of the nut. Once the nut is moving, the force needed to keep it moving is relatively small. So... the answer to the original question comes down to this... the impact wrench operates in two different modes: 1) Hammering 2) Spinning When the wrench is hammering, the torque on the hammer is applied to the nut. Now, despite the large impulse that the internal hammers are imparting on the nut (and the consequent REACTION on the wrench itself), there is not enough of a torque developed (during this impulse) to move the relatively large inertial mass of the wrench (not much anyway). When the wrench is simply spinning the nut, their is a torque developed that is dependent on how much torque is needed to keep removing the nut. But, as I wrote already, there is not much torque needed once the nut is spinning freely. Another monkey wrench for you (pun definitely intended), the shaft is not directly connected to the wrench... what I mean is that the impulse that the hammers provide and the torque that is developed on the nut is actually provided by the compressed air. What this means is that the balancing force needed to keep the wrench from flying out of your hands is due only to frictional forces on the shaft (and any misalignment with the nut). The spinning turbine imparts pressure waves into the air hose feeding the impact wrench (you can notice cheaply made air hoses jumping around a little). These pressure waves combine with the hammers smacking the yoke of the device to produce the machine gun sound you wrote of. I hope this answers your question Brian, please ask for clarification on anything that you believe i did not cover in depth. krobert-ga```
 Subject: Re: Newton's Law From: andy22-ga on 26 Jun 2003 04:58 PDT
 ```I have to disagree with the GA's answer on this one. He/she states: >In the process of compressing air, much of the "reaction" created >energy is expended as heat rather than as mechanical energy. Check >the temperature of a bicycle tire after you pump it up. It is conceptually incorrect to introduce the notion of energy into Newton's 3rd Law. Newton's 3rd Law states that "every action will have an equal but opposite reaction". The action Newton is talking about is *force*, not energy. Force is a vector quantity while energy is not. The simple answer to the question is that the air tool in question has a longer lever arm, and thus the user exerts less force where he is gripping the tool to counter the torque imparted on the nut or bolt. The source of the energy, be it from a battery or electrical generating plant 500 miles away or from a compressed air reservoir, is not important at all. The answer given is conceptually incorrect. andy22```
 Subject: Re: Newton's Law From: digsalot-ga on 26 Jun 2003 05:21 PDT
 ```While both the answer and comment are conceptually right depending on interpretation, I am asking that my answer be removed. Either way, Newton's Third Law applies, the action, reaction process didn't vanish, it still exists. Force cannot be applied without the expenditure of energy. And air pressure is definitely 'force.' If the bulk of 'force' or energy is utilized or expended in a remote location, such as moving a cylinder, it is no longer available as reactive force or energy in the tool.```
 Subject: Re: Newton's Law From: googel-ga on 26 Jun 2003 06:04 PDT
 ```Hi digsalot-ga, Wait. Before asking the removal of your answer you could make it sure that no valves and compression are used to dimish that reaction. regards, g```
 Subject: Re: Newton's Law From: googel-ga on 26 Jun 2003 06:06 PDT
 `meant "diminis" instead of "dimish".`
 Subject: Re: Newton's Law From: googel-ga on 26 Jun 2003 15:23 PDT
 `Yeh. Andy22's explanation seems too ...`
 Subject: Re: Newton's Law From: racecar-ga on 26 Jun 2003 18:56 PDT
 ```The thing about pneumatic wrenches that makes it easy to loosen tight nuts is the hammering action. If you try to loosen a tight nut with an electric drill, it is likely to twist out of your hands. Each time the wrench "hammers", a very large torque is applied to the nut for a very short time. A torque of the same magnitude but opposite direction is applied to the wrench for the same amount of time (by Newton's law, as you pointed out). Though this torque is, as I said, very large, it acts for such a short time that it can't give much of an angular velocity to the wrench. In physics, the amount of momentum you give something is called the impulse. Impulse is equal to force multiplied by time. If you think of a 'rotational impulse' which is the same thing, but for rotational rather than linear forces, then rotational impulse is torque multiplied by time. The rotational impulse of each 'hammer' of the wrench is fairly small--enough angular momentum is transferred to budge the nut, but the wrench is much heavier, and so the amount of angular momentum transferred to it only moves it a little. Basically, a large amount of torque is needed to turn the nut, but the wrench supplies that torque in short bursts. The rotational inertia of the wrench allows you, the operator, to apply a much smaller torque spread out over a longer time.```
 Subject: Re: Newton's Law From: googel-ga on 26 Jun 2003 23:52 PDT
 ```"pneumatic wrenches" http://www.atlascopco.com/tools/products/website.nsf/0/2cd20ab5cce54542c1256c5c002fc555/\$FILE/Tightening%20technique.pdf pages 17- 22 pages 18-19: " The advantage of impact wrenches is that they have a very high capacity relative to the weight and size of the tool. As the reaction torque is not greater than that needed to accelerate the hammer the reaction force transferred back to the operator is very small..." http://www.spairtool.co.uk/pneumatic_tools/wrenches/ : "Applications: Excellent choice for heavy automotive and truck work such as tyre changing, shock and spring work, farm, body shop, and front end work. Ideal anywhere extra powerful tools are needed. Features: Twin dog clutch provides more power and smooth balanced blows "```
 Subject: Re: Newton's Law From: eek-ga on 27 Jun 2003 13:05 PDT
 ```I have to say that I think the answer given is patently incorrect. If the given answer were correct then a battery operated impact wrench would not work because "both the action and the reaction are contained within the same tool." The impact wrench operates in the same manner as a hammer is able to insert a nail into a board. It is the brief impulses that cause the nut (or nail) to move without accelerating the impact wrench (hammer) out of one's hand. The two devices work against the inertia of the tool. "The power with which this takes place is proportional to the diameter of the piston - the greater the diameter the more power." This statement is incorrect. The amount of energy (from which follows power) in the system is constant. It is the force which is proportional to piston diameter (for a given pressure). If you demand greater force through a larger diameter piston, then you will have reduced piston velocity as the energy must balance. Bradley```
 Subject: Re: Newton's Law From: digsalot-ga on 27 Jun 2003 13:31 PDT
 ```I have been digging through other resources. It seems the material I was using was dealing with theory only rather than the actual mechanics of the way the tool works. Therefore, my answer is wrong. A new request for removal has been made. To all who jumped in on this, my thanks. Cheers digs```
 Subject: Re: Newton's Law From: googel-ga on 27 Jun 2003 14:44 PDT
 ```Hi eek-ga, By what I have learned here from racecar-ga then my web-findings about pneumatic wrenches is that the "accelerating the impact wrench (hammer) out of one's hand" is prevented by proper limit settings, clutch/es (for decoupling) and the small accelerating torque --among others probably. googel-ga```
 Subject: Re: Newton's Law From: googel-ga on 27 Jun 2003 14:57 PDT
 ```Hi eek-ga, What I have learned here from racecar-ga then my web-findings about pneumatic wrenches is that "accelerating the impact wrench (hammer) out of one's hand" is prevented by proper limit settings, clutch/es (for decoupling) and the small hammer-accelerating torque and force --among others probably. googel-ga```
 Subject: Re: Newton's Law From: googel-ga on 28 Jun 2003 08:00 PDT
 ```To any researcher, Please answer this question and feel free to use any of my comments here. http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO2&Sect2=HITOFF&u=/netahtml/search-adv.htm&r=9&p=1&f=G&l=50&d=ptxt&S1=((wrench+AND+reaction)+AND+(force+OR+torque)).ABST.&OS=abst/(wrench+and+reaction+and+(force+or+torque))&RS=ABST/((wrench+AND+reaction)+AND+(force+OR+torque)) United States Patent 6,009,775 Inventors: Thompson; Owen R. (Louisville, KY); Weber; Edward J. (Girard, PA); Rounds; Jerry L. (Erie, PA) Assignee: Titan Tool Company (Fairview, PA) 2. Background of Related Art A wrench that transfers energy stored in a flywheel to a bolt or nut which is to be loosened is conventionally known in the automobile lugnut removal field. U.S. Pat. No. 5,158,354 to Simonin discloses a conventional wrench with a drive motor and flywheel that are rigidly connected in a housing to drive an output ferrule when a spring clutch is engaged. In operation, a user provides power to the drive motor which causes a flywheel to rotate. Once the flywheel achieves a predetermined speed, the user presses the output ferrule onto a lugnut which causes a single tooth clutch plate connected to the ferrule to collide with a mating single tooth clutch plate connected to the flywheel. The rotational energy from the flywheel is then transferred to the output ferrule to provide a removal force to a lugnut engaged by the ferrule. The conventionally known wrench is designed for the specific purpose of quickly removing a flat tire. Accordingly, the conventional wrench is designed to be economically made with little concern for accuracy or endurance. Because the motor of the conventionally known flywheel wrench is rigidly connected to the housing, a torque reaction will be transmitted directly to the user of the device. Torque reaction is a detrimental reverse torque which results from the elastic collision of the clutch mechanism when the rotational energy transmitted from the flywheel to the output ferrule is converted to a torque for removing a fastener. Transmission of torque reaction to an operator can lead to many undesirable health problems including nerve damage, muscle strain and bruising. Torque reaction is especially large when the rotational energy stored in the flywheel is not sufficient to remove the fastener to which the output ferrule is connected. Torque reaction is also compounded when any of the mechanisms that are rotated are not concentric. The nature and object of conventionally known flywheel wrenches has never demanded a strict limit to the amount of torque reaction that is acceptable because conventionally known flywheel wrenches are generally used in lightweight limited use applications, such as removing a lugnut from an automobile wheel. Accordingly, the detrimental effects of torque reaction being transmitted to an operator are negligible in conventionally known flywheel wrenches and do not outweigh the benefits of making the device economical and compact. In heavier, industrial applications, it is conventionally known to use an impact wrench to remove fasteners. The impact wrench also suffers from the problem of transmission of torque reaction to the operator. In addition, the user of an impact wrench has little control over the amount of torque that is output by the tool. Torque output from air operated power equipment, such as an impact wrench, varies greatly depending on the air pressure, amount of moisture in the air and the condition of the motor itself. Furthermore, impact wrenches require a relatively large amount of input power to achieve a given output torque. SUMMARY OF THE INVENTION The present invention has been made in view of the above problems. An object of the invention is to provide an economical and efficient wrench that transmits little torque reaction from the output drive to the wrench housing. Another object of the invention is to provide a wrench that can be easily and accurately controlled to provide a specific torque output. A further object of the invention is to provide a wrench that can be used while suspended by a cable without requiring the physical control of an operator during use. Yet another object of the invention is to provide a wrench that requires a small power input to achieve a large torque output. According to a first aspect of the invention, there is provided a power driven wrench in which a drive motor is located inside a housing. An inertial mass for example, a flywheel is connected to the drive motor such that it can be rotationally driven. An output drive mechanism is located at an output end of the inertial mass. The inertial mass and the drive motor are connected to the housing such that they can rotate with respect to the housing to substantially prevent torque reaction from being transmitted to the housing.```
 Subject: Re: Newton's Law From: googel-ga on 30 Jun 2003 06:56 PDT
 ```Hello krobert-ga, Yours is a real nice explanation given to those cracking their nuts on this question of Brian. Thank you.```
 Subject: Re: Newton's Law From: googel-ga on 01 Jul 2003 03:43 PDT
 ```from Question ID: 223701 : Subject: to resrchr krobert-ga for answering brian0575-ga's "Newton's Law"--- Asked by: googel-ga Expires: 30 Jul 2003 15:43 PDT Question ID: 223701 Thank you, krobert-ga, for answering brian0575-ga's "Newton's Law" question and thus satisfying my curiosity about the working principle of impact wrenches. Clarification of Question by googel-ga on 30 Jun 2003 15:58 PDT Thanks to brian0575-ga for the question: Subject: Newton's Law```