Chainsaw/flashlight Overkill

[Robbtoberfest] has earned our admiration with this crazy chainsaw powered spot light. It looks horribly dangerous, extremely inefficient, and woefully under engineered. We absolutely love it.

This could be plucked from a video game or a movie and seems to be one UV bulb away from being the ultimate post apocalyptic zombie vampire Armageddon weapon. He has taken apart a chainsaw and attached it to a DC treadmill motor using a couple of bike sprockets and a chain. That DC motor then feeds a car headlight directly. As you can see in the video, when he cranks the gas, it shines pretty brightly. The unfinished nature of this is due to a deadline for a contest on instructables, so he plans on adding a protective cowl, some fancy paint work, and a voltage regulator down the road.

While this may be inefficient, it is certainly a step up from a steam powered spud gun.

45 thoughts on “Chainsaw/flashlight Overkill

    1. I dont’ know about the green zone. But I’am sure it will charge a 12V battery as this headlight draws probably about 5A@12V. So after a max. of 20min you should be able to start the car/hummer.

  1. When I read the topic I thought kind of stupid. Then I seen what he did, then I thought that sweet. But then I noticed it was just made into a generator, not bad but he could of used something other than a chainsaw that stalls all the time.

    Good thinking though.

  2. Holy balls!

    This is why I only buy STIHL and husqvarna chainsaws! No starting problems!

    Pretty rad. I think it would be better to mount the motor closer to the engine, maybe even couple them together and use no chain at all. He mentions the need for a voltage regulator- IMO, the best way to get 12V from this thing and keep the weight down would be to bolt a motorcycle/snowmobile/ATV stator right to the engine, and then use the accompanying voltage regulator. Better yet, use the headlight from the donor machine as well, if it uses a halogen bulb. That would cut the weight and size almost in half!

  3. hehe, nice mod.
    wonder if you could charge a phosphate lithium pack from this, would make a great emergency inverter for keeping your freezer/etc going in the event of a prolonged power failure (koff 2012solarArmageddon /koff) ;-)
    And the light makes a great addon for warding off the armies of the undead reanimated by said solar flare… sort of like Macgyver meets Dawn of the Dead. Film at 11.

  4. That’s the reason I use only electric chainsaws. They start at the push of a button. Much more reliable in case of a zombie attack. Well, as long as they don’t chew the wires and come in range of the wire. But aside from that, you’re set! :)

  5. @bothersaidpooh
    It’s a generator, so yes, you obviously could charge batteries with it. The problem is that this is a rather inefficient setup, you would most certainly get a much higher efficiency from an actual generator. This unit retains the original clutch, and loses efficiency to the friction introduced by the chain and sprocket setup, among other things. This not to mention the fact that simply turning a motor shaft to create electricity is not very efficient (relatively speaking) to begin with.

    @steaky, barry
    He says that he doesn’t have a voltage regulator on it, that’s why he was trying to keep the RPM so low.

    1. A chain drive is quite efficient, that’s the reason bicycles use it – you don’t want to waste too much of your precious muscle power. The centrifugal clutch will have no friction, if the rpms are high enough and the torque is not to high. I would also keep it, it facilitates starting. Why should the motr be an inefficient generator? it looks like a permanent-magnet DC motor. The only problem is voltage regulation with this setup. You have to do it like a motorcycle regulator: Doing some PWM with thyristors or MOSFET.

  6. i find this completely impracticable and virtually useless as/is.not only is it very dangerous(a bike chain and no guard,and did you see that chain flapping)but i doubt you would be able to hold it up for more then a minute or two with all that crap hanging off the front of it.

    maybe it would have some sort of use as a generator you plug into,assuming he could get it to idle but even then you would have no way to increase the rpm to deal with the load put on it,so actually it’s a useless waste of a nice old homelite saw that probably would cut real nice with a tune up and new bar and chain.

  7. What is it with all the HAD commenters lately bringing up the practicality of this
    stuff? I’m pretty sure that if you were looking for practicality, “Chainsaw Flashlight” was a pretty poor choice of article to click on.

    1. Newer also :-) Only the very old ones (pre electronic days) had an external regulator box. In it basically a relay, hanging on the output voltage, vibrating at 100 or 200Hz and giving PWM to the exciter coil. But normally a car alternator is bigger and much heavier.

  8. makes me want to get an old chainsaw, car altenator and some expensive hi output white leds to have a mix of hi efficiency and low efficiency with a long bulb life and constant output.

    It probably would work well, though i hear xenon car lights are better than leds.

  9. To the guys thinking that you can use a car alternator, you CAN’T without initial current to start the generation process (you’d need a battery)

    You need what’s called a self-exciting alternator, they can be had but are rather uncommon as compared to a regular car alternator.

    It’s been a while since I’ve looked at the torque requirements for your average car alternator, but I suspect that your average chainsaw engine won’t *cut* it (heheheahahaha) unless you keep the power draw pretty low. A small stator is a much lighter, more compact solution and will still provide a decent amount of current.

  10. @jake
    i most certainly have…but why are you asking ME this?what relevance does it have to my comment other then it might run the light he has mounted without blowing it.i see no use for it as i see no use for this “device”.

    anywhere this monstrosity could be used i bet there would be atleast 100 or more other/better/smarter/MORE PRACTICAL and useful tools that could be used.

    like i said this is a horrible waste of a real nice old saw that would do it’s prescribed job 100 times better then to be used as a clunky loud unbalanced flashlight.

  11. @todd

    You said “but even then you would have no way to increase the rpm to deal with the load put on it”

    This led me to believe that you don’t realize how such a device works.

  12. And you’re calling a homelite saw NICE? I’d call that a $5 garage-sale-worthy piece of crap!!!

    If it isn’t a stihl or husqvarna, I really don’t think it’s worth using unless you are one of those people that cuts up about 1 tree per year xD

  13. yes the homelites were good saws,in all honisty i would rather have an old homelite xl then a stihl but that’s not my main point,my main point is that this is a useless waist of equipment and time.

    it’s not even close to being ergonomic in any way and a lantern would be more practical in just about any situation then this not to mention the millions of other battery and other fueled lamps.

    unless you actually strap this thing to your back and hike a few miles with it i just don’t see you being in a situation where this would be your only source of light

  14. @todd
    It’s pretty rare to see a post on this site that could be described as ‘practical’, and that is the point – People make these things just to prove that they can. Yes, there is always a better way, and quite often these people are aware of that better way.

    If you’ve ever made some random gadget like this, you know that it *never* goes together the way you had it in mind (well, not unless you own a lathe, end mill, and about 1000 other shop/electrical tools and machines).

    Also, dude, hooked on phonics – Check it out :P :P :P

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