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Impact Torque Towing

Impact Gun Hammer Mechanism Generates Higher Torque for Towing
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An impact gun uses a rapidly oscillating hammer mechanism to generate high rotational torque, which can be useful for driving in screws or removing lugnuts or bolts, without generating any reaction torque. [see link below]

A similar mechanism would be used to rotate the axle(s) of a vehicle, to generate higher torque for towing.

sanman, Nov 04 2020

Impact Wrench https://en.wikipedi.../wiki/Impact_wrench
explanation of how Impact Wrench works [sanman, Nov 04 2020]

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       No. For many, many reasons no. Here are the top 3.   

       1. Rotary hammer mechanisms don't increase total torque, they just concentrate it in a spike. 2. Those torque spikes will break things. 3. Using a lower gear will achieve the same effect in a manner less offensive to man, beast and machine.
bs0u0155, Nov 04 2020

       It's a tire axle -- how are you seriously going to break it? You can't break things unless you're over-tightening something, like a screw -- and a tire axle is not tightening like a screw does.   

       Nextly, the torque spikes can at least help lurch forward a tow-load that is stuck.
sanman, Nov 04 2020

       Well, an axle will be built to handle a certain amount of torque + a safety factor. A rotary hammer will display no torque for most of the rotation then a sudden spike of ~10x the input torque. So, since you're building a 300bhp V8 rotary hammer, you're input torque will be ~300lb/ft. In 1st gear we have a ~5:1 torque multiplier effect of gear ratio, you'll need a differential/hub capable of handling 15,000 lb/ft (10x) plus the safety factor and probably plus some more for shock loading. You have to handle peak torque, not average.   

       There's no way you get away with this without a 10x overbuilding of the whole transmission after the hammer.   

       What advantage is this over a standard low range gearbox?
bs0u0155, Nov 04 2020

       This impact hammer torque mechanism would be attached directly to the axle(s), and not to the transmission. The impact rate (BPM - Blows Per Minute) would be electronically controlled, therefore there wouldn't be any need to involve the transmission or its fragile gearing.
sanman, Nov 04 2020

       //It's a tire axle -- how are you seriously going to break it?// well, speaking for Murphy, and from experience, you'll break it on a steep pitch of a hill about 30 miles from town. In the dark.   

       //help lurch forward a tow-load that is stuck// somebody shouldn't have sent it to me in the first place.
lurch, Nov 04 2020

       So, if a normal gearbox transmission is equally good at delivering different torques at different speeds, the logical conclusion is that we can dispense with the gearbox entirely and have a pure hammer-torque transmission. It should be continuously variable from standing start to full speed at constant engine revs. Could be noisy though.
pocmloc, Nov 04 2020

       Yeah, because of noise and wear, I would only use this impact hammer method for towing, rather than normal driving. As for whether it's continuously variable or not -- this is more the opposite of CVT, in the sense that it's electronically-pulsed. You could dial up the pulse rate according to whatever way you want, since there's no gearing or belts.
sanman, Nov 04 2020

       I for one have always wanted my car's wheels to be doing a "burnout" no matter how gently I push the pedal.
sninctown, Nov 04 2020

       As per [sninctown], the sudden impact will break the traction of your tyres, so this will be both loud and wear out your tyres faster, while getting you nowhere.
neutrinos_shadow, Nov 04 2020

       Maybe the impact hammer method could asymmetrically hammer in a somewhat more downward direction while applying its torque-spike effect. That might increase the traction of the tires, due to the asymmetric downward force on them, thus reducing the chances for burnouts/slippage.
sanman, Nov 04 2020

       Powertrain engineer here. Presuming this was somehow coming out of your engine crank, you would break your accessory drive, your timing drive, your motor mounts, and probably many ancillary items hanging on the engine.   

       Your clutch damping springs would absorb some of the impact load before bouncing off of their stops, but wouldn't last long, either.   

       If somehow you designed a clutch that would take this punishment, your transmission would experience a lot of unpleasant gear chatter shortly before beeaking gear teeth.
RayfordSteele, Nov 05 2020

       [RayfordSteele] That would be your job as a //Powertrain engineer// to sort out those minor niggles. Now lets get back to the sensible business of designing this thing.
pocmloc, Nov 05 2020

       Afraid that sorting out those minor niggles would be the job of a physicist, or better-than average magician.
RayfordSteele, Nov 05 2020

       The point of the impact in an impact wrench is to apply a very high torque for a shot time to overcome static friction. As everyone else pointed out, if you put that in the driveline, as described, if by some chance you have the system designed well enough that it doesn't break, it will simply cause the tires to slip.   

       Now for general on road towing, I don't think there is any shortcoming in a standard transmission, but sometime you need additional towing force, with less peak force on the tires (limited by traction). This might be useful for tasks such as stump pulling, but most of all for truck tug of war competitions. You could employ a concept similar to an impact wrench, but rather than a rotary system, the hammer action needs to be linear front to back. A first pass design for this might be to have the (heavily reinforced) trailer hitch mounted such that it could slide forward/back slightly, and have it held forward by a stiff spring. As the truck pulls against a stubborn load, the spring compresses. When the tires start to slip, a signal is sent from the traction control system to the "jackhammer system", that repeated accelerates a large weight forward until it bounces off a stop rigidly connected to the moveable trailer hitch. With this, the force on the majority of the truck and the friction on the tires would be set by how fast the weight is accelerated forward, but the peak force on the trailer hitch is based on it being hammered forward by this weight.   

       I can think of a lot of situations where this wouldn't be that useful. For example pulling a car out of the ditch generally requires a force for a long enough period of time to get the car up the steep incline. Pulling a stump could be improved, but only if the stump couldn't flex enough to absorb the individual impacts. The place I can see this being highly effective would be in a truck tug of war. As long as you use a strong enough chain (not a stretchy rope), it will either jerk the opponent backwards breaking their traction on each impact, or more likely, since the truck has so much inertia and the acceleration is so sudden, it will simply rip the trailer hitch from the opposing truck. While dragging the opponent backwards is considered the normal mode of winning, I think tearing their bumper off also counts. :)
scad mientist, Nov 06 2020


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