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Chainsaws in games and films are an epitome of gruesome dismemberment. In Zombie attacks they are used to cut through cloth and flesh while in games they can dismember if not cut from skull to groin without problems.

I am ignoring the exact material the chainsaw and powersource are made off. That is another question for another time and I'm assuming the chainsaw is up to the task of cutting through cloth, flesh and bone without wearing out.

The question: how powerful does the powersource need to be to allow a chainsaw to cut through all these materials without stalling?

I am not asking about the size, shape or material of the powersource or it's engine, just how much power it would need to keep operating.

The size and shape is a "standard" Hollywood grade chainsaw. Something like this: https://images.app.goo.gl/p6hDXA2TvqtP5uLT6. Again dont worry about the engine or powersource, just about the amount of power that needs to be in the chain to cut through everything.

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  • $\begingroup$ Comments are not for extended discussion; this conversation has been moved to chat. $\endgroup$ – Monty Wild Oct 23 '19 at 0:03
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Wood from a tree is tough stuff. Ever try to break a stick more than a couple centimeters thick with your bare hands? It was probably pretty hard if not impossible (depending on the type of wood). Because of the toughness of wood, even a very small chainsaw is a powerful piece of equipment.

Flesh is no match for a chainsaw, it could probably cut through it pretty much forever without wearing out. Bones may be slightly tougher, but they are rigid and a chainsaw will likely be able to cut through them without much problem - though it will probably dull the blade more than wood.

The smallest chainsaw in production is the Bosch Nanoblade: 12V electric with a blade under ten centimeters long. Probably the most wimpy chainsaw you can find (and probably not one that needs to exist), but here's a video of a guy cutting meat with it: https://youtu.be/QVAR4A73lGk?t=369

At 7:30 he cuts through a chicken drumstick, and it seems to go through the bone OK. A bit slowly, but it goes through it. The Bosch Nanoblade runs on 12V, and probably draws less than 5A at peak, putting it's maximum power output at less than 100W. A tiny makita pruning chainsaw is rated at 700W of power (about one horsepower) which is almost an order of magnitude more powerful. This chainsaw will probably chew through meat/bone an order of magnitude more than the nanoblade. By the time you're at a large chainsaw, you may be getting a 80cc engine capable of 5-10 horsepower.

So let's put it this way:
There's a reason chainsaws have kick-back stops, chain-catchers, hand-guards, throttle locks and a whole bunch of other safety items. A chainsaw is a powerful piece of equipment that, if used improperly, can seriously injure, maim or kill a human.

Or this way:
If I saw a person waving around a chainsaw, even a small one, I would run the other way.


For what it's worth, a chainsaw won't be a "lop off zombie limbs with ease". It takes time for a chainsaw to cut through something, and it has a tendency to pull the zombies towards you while it's cutting. So it's probably not an ideal weapon, but a chainsaw will almost certainly make a mess of whatever is attacked with it.

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    $\begingroup$ The problem is that chainsaws have a habit to stall as cloth quickly disrupts the mechanism. I assumed that the meat and bone (bone which is one of the toughest materials in nature) would have similar problems. So while meat doesnt seem to be a problem, how much power is needed to cut bone and cloth in one long cut? $\endgroup$ – Demigan Oct 20 '19 at 18:14
  • $\begingroup$ Another problem is that a chainsaw (or any saw) doesn't just slice through things. A saw of about the size shown in the OP's link might take 30 seconds or so to cut through a 1 ft/30 cm diameter pine log, which is probably comparable to a muscular human torso. (NB: I have not tried this myself!) Also, chainsaw cuts are very painful (personal experience!), so a normal person will quickly move away at the first touch of the chain. $\endgroup$ – jamesqf Oct 21 '19 at 4:06
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    $\begingroup$ As further proof that chainsaws can cut flesh, standard protective gear for chainsaw user is kevlar pants, kevlar gauntlets, steel-toe boots, helmet with visor and a sturdy jacket. $\endgroup$ – Bald Bear Oct 21 '19 at 15:13
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The main problem with using a chainsaw on a zombie is not the flesh or bone, since they are bulk materials that a chainsaw will cut with relative ease.

The main problem is cloth. There is a class of industrial accident where a person gets their clothing caught in powered machinery, and if the machinery in which the clothing gets caught is not razor-sharp, the cloth gets drawn in or wrapped around the moving object.

From there, there are a number of different outcomes. One is that the cloth is drawn tight enough to tear skin and break bones and cause injuries that if they are not an outright amputation, are severe enough to necessitate a surgical amputation. This tends to occur with large, powerful industrial machinery.

The other potential outcome is that sufficient cloth is drawn into the machinery to jam it. When successive layers of cloth are drawn into a small gap by a moving tool, the cloth acts like a brake. This is more likely with a power tool such as a chainsaw

From this it can be seen that the strongest material that a chainsaw must cut when attacking a clothed person - or zombie - is not the person/zombie, but potentially their clothing.

So, the liklihood of a chainsaw to successfully cut through a human, be they alive, dead, or undead, would depend heavily on the maintenance that the tool receives. If it is kept clean and razor sharp, the blade will cut through cloth with ease, but should the blade get blunt, using it against a clothed human is to risk it jamming, binding it to it's intended victim by their clothing.

A chainsaw is not the best possible tool to use against clothed humans. The blade is designed to cut hard, fibrous materials such as wood, and not soft, flexible and strong substances such as flesh and cloth. To cut wood, a channel of sufficient width for the blade to fit within must be cut, else the blade will jam.

To cut flesh, ideally a narrow, sharp blade would be employed this would also make cutting cloth easier. However, a chainsaw blade modified in such a manner would be difficult to achieve, especially in the midst of a zombie outbreak.

Most realistically, a successful wielder of a chainsaw against zombies would keep his weapon meticulously clean and spent a great deal of time keeping it sharp.

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The motor is not really the issue.

First bone in a non-issue cutting bone is very similar to cutting wood. Chainsaws are already regularly used to cut flesh and bone.

The big problem with cutting cloth is not power, it is the design of the chainsaw, chainsaws work, well like saws, not shears so they don't cut fiber well. A motor strong enough to pull the fibers through it is more than strong enough to wrench the saw out of your hands, or drag you off your feet. There are a few ways to deal with this.

Redesign the saw so you have two chains moving in opposite directions so fibers are sheared, the downside is this is a much more complex and precise design, it will not be forgiving with rough handling and will break a lot so probably not a good idea.

Install a static blade on either side of where the chain enters the housing designed to act a shear to cut any fiber that enters the housing. of course not having a housing around the chain will work almost as well.

Ideally you combine this with a redesign of the chain teeth, so they are less hook shaped and fibers will not get caught as easily. Demolition teeth would be a good fit, something like the two below. The sharper you can make the the teeth the better.

enter image description here

enter image description here

The other thing you do is make a chainsaw without a clutch, this means as long as the motor is running the chain is moving, this also means if you get a kickback there is no safety to keep it from cutting the user however.

If you really want a saw that will keep moving no matter what, use a hydraulic chainsaw. With no gas motor to stall they will will keep running right up until the chain fails.

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  • $\begingroup$ From personal expience, bone and wood are VERY different. The way they chip, break apart, the way they handle stresses etc is different. I know the first answer has a video of someone cutting a drumstick but a dead and partially fillet drumstick with hollow bones is a bit different from cutting a limb, especially a struggling one. Your answer is interesting but does not deal with the off-the-shelf chainsaws usually used by hollywood and games. I would be very much interested in that power needed to cut fiber with a "normal" design chainsaw. $\endgroup$ – Demigan Oct 21 '19 at 17:54
  • $\begingroup$ As someone who has cut a lot of bone sawing bone and sawing wood are very similar If I had to pick an individual wood I would say teak is pretty close. And the issue is just powering up the engine won't let it cut fibers, or too put it a different way, existing engines in larger saws are more than enough to cut fiber it is the rest of the saw that is not designed to cut fiber. $\endgroup$ – John Oct 22 '19 at 11:08
  • $\begingroup$ I've seen your edit, but I am specifically interested in the force needed to cut cloth and bone with a "basic" chainsaw meant for wood cutting rather than a specific saw in a butchery. I dont care about the wear and tear nor about how it would rip out of your hands if you had that much power. You allude to the possibility that the chainsaw could cut cloth despite its design if it had enough power, and that amount of power is all I want to know. $\endgroup$ – Demigan Oct 24 '19 at 12:14
  • $\begingroup$ @Demigan No I said a chainsaw can already easily cut cloth with the motor it has, no amount of power gives you an answer, it is like asing how hard you have to swing a hammer to cut a rope, by the point it can you are not talking about cutting anymore but ballistic rupture. At that speed/power a normal chainsaw will disintegrate before it even touches the cloth. $\endgroup$ – John Oct 24 '19 at 20:17
  • $\begingroup$ and why does it take all this time for someone to say just that? Everyone talks about either just the bone excluding cloth or about wrapping and stalling the motor. If he motor stalls it would have too little force to rip the treads and continue so it would require more force. I do think you are ignoring that option and go for "it has to break upon touching" suddenly. And once again I am NOT INTERESTED in what would happen to the chainsaw or the wielder, all I want is the force required. Why do I have to repeat that so often? $\endgroup$ – Demigan Oct 24 '19 at 20:25

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