There is no reason at all for this to exist.

[LMNO]

BEAR TREBUCHET.



Accept no substitutes.

[Richter]

More of an academic question,WH40K fan so thoughts of building a decrative one using a petrol driven R/C car engine and a blunted chain.

Again only an idea which popped into my head as something class to do but the cost is of course prohibitive and Irish law on swords is going to be tight, Hence the "agricultural implament excuse" (But officer,What if I have to parry when that tree comes crashing down)

OK, chainsaw sword  .  (BTW: check out the manga "Zombie Powder" by Kubo Tite for maore chainsword fun)
I've thoght this through before, here's what I came up with.
There are practical problems with weight of the implement, and mechanics of hitting anything with it. 

A sword, operating by hitting / cutting with force on an edge or tip, acts differntly than a chainsaw.  The Teutonic Ideal of western swordplay (analysis of angles invovled), demonstrates that the directions of the force is idealy perpendicular to the surface to be struck.  (As an oblique or acute angle will be more prone to defelction as the anlges deviate form 90 degrees.)  A chainsaw works by dragging cutting teeth paralell to the surface to be cut.  On a small scale, the phsycis are the same (Thing hits target with such force that it breaks rather than bends).  Practically, imaging fighting with a chain saw sword like running up to someone, putting a hacksaw to their body, and sawing vigourously  , the initial force on swinging the weapon will not necessarily aid the cut.  Also, commonly used chainsaws 2 handled design is used to keep the edge of the saw on the surface being cut.  Doing so one handed, or with any part of the saw other than the egde is dangerous, as it makes it more likely for the chain, (driven by the engine), to make the saw bounce off the target (usually towards you.  Hence the 2 handles, deadman switch on the motor, and chain break integrated into a chainsaw.)

If I remember my WH40K, the chain blades are very heavy, 1 edged devices.  They would be good for dropping a moving chainsaw on a target, but harder to use and less effective with every degree you deviate from a top-down cut.  Without gravity doing the work, it's only your muscles behind the blade, which gets hard in a HURRY with heavy weapons. 
IRL expamples of actual, useable war swords top the scales at 7-8 lbs.  Anything more is a ceremonial piece.  Given a chain blade may need LOTS more metal than just 1 blade, this gets heavier than is practical in a hurry. 
(Practical Experiment: hold a 5 lb. weight at your hip, in an arms extended straight from the shoulder, and tied to teh end or a 2 ft. dowel.  Which could you do the longest?)

IMHO:  It's a lot of work to design, scale down, and power, and the result would be unweildy.  Not practical for a melee weapon. 
If you're worried about falling trees, practice dodging The footwork and mobility will do more for you than the brute force to swing 1 honking big weapon.

   

[Jasper]

The point of the chainsword is that you have a genetically enhanced maniac with power armor weilding it. 

[Richter]

The military IS working on the power armor...

[Jasper]

And gene therapy is on the horizon.  Soldiers comparable to Space marines are within the realm of possibility, IMO.

[Richter]

That will be fun...

Even for a genetic super soldier though, you could do better.  A scaled up version of a regular sword, or a heavy circular saw would be a more effective tool / weapon. 
(IMHO: I'm considering power consumption, weight, practical effect, and learning curve.)

[Golden Applesauce]

Or, um, a gun?

Stronger soldiers => can carry more stuff => heavier machine guns

[P3nT4gR4m]

Richter you bastard! You've just gone and destroyed every chainsaw fantasy I evar had.   Why do you hate me so?

[Jasper]

That will be fun...

Even for a genetic super soldier though, you could do better.  A scaled up version of a regular sword, or a heavy circular saw would be a more effective tool / weapon. 
(IMHO: I'm considering power consumption, weight, practical effect, and learning curve.)

Okay, I'll suppose that a proper chainsword would weigh about 80-100 lbs. 

Assuming we can pack enough grunt into a human body with mechanically assisted movement to swing this thing as you might were it a normal sword, think of the physics behind that kind of impact, without taking the chainsaw into account.

A chain axe would be more effective, though.

[Richter]

Applesauce:  Good point! 100 lb. melee weapon is inferior to 40lb. gun and 60 lbs. of ammo. Though there's a point where you can do all your ranged work with cruise missiles, but you still need someone to get close and personal.  Swords may be outmoded, but no ranged weapon has been able to make hand to hand skills obsolete yet. 

Felix: It's an idea, or a lance maybe (suspended from an underarm or hip rig).  Just keep in mind that with a saw you gain NO advantage from intitial impact.  It's the RPM / abrasiveness / time in contact with target combination that does the damage.

[LMNO]

Chainsaw pike, then?

[Jasper]

No, pneumatic drill pike.

Richter: The weight would be an asset to the weapon, but I think if you had a powerful enough chain, it would aid combat severely by, at the very least, opening huge wounds that aren't easy to close.

[Richter]

Weight in a weapons (after a point) is a tradeoff, though.  The more of an asset it is, the more cumbersome your weapon is to manuver.  (Comparing a bowie knife to a SAS style dagger, or a ball pean hammer to a 15 lb. sledge, for example.)
(I may be biased to favor manoverability though.)

If you're hitting flesh, I totally agree, it would be isntant ICU type wounds.  Big, nasty saw teeth and low RPM all the way 
For hitting armor (assuming our genetically modified, power suited Marines), I'd favor a high RPM, fine toothed saw, a power-hacksaw equivalent. (assuming both 2 big Marines, slugging it out attrition style, or a lighter foot soldier trying to play can - opener)  If it can cut armor, it can likely cut flesh too 

I like the pneumatic pike idea.  Especially for mecha vs. mecha fighting, or anti- amor applications though, I'd pair the pike with a pneumatic shear (jaws of life - esque)