I’ve really been wondering this for quite some time, but given the recent thread that Runs With Scissors posted, it seems like a good time to ask.
So, how in the hell does a juggler know that he has practiced enough to toss those things around? I can imagine that one must practice on inactive chainsaws at first, but seriously, how do they know when it is ok to start those things running?
I’d say when they can perform very, very consistently on one that doesn’t have a chain on it; that’s when things get really scary.
Chainsaws used for juggling don’t have teeth on the chain and the motor, while running, isn’t actually driving the chain (or just remove the chain altogether). Very loud and smokey but not really dangerous.
So what you’re juggling is a set of very heavy clubs. I used to juggle bowling balls and odd-shaped/heavy objects (toilet plungers were the worst, all the weight is at the head so the handle tends to bop you in the face until you adjust to the balance). It takes a lot of strength and practice but when you’re strong enough to handle the weight, you’re ready to do them with the motors running.
Similarly, machetes and other blades don’t have a sharp edge on them (so you don’t accidentally cut something off). Flaming torches aren’t that bad even if you do accidentally hit yourself with the lit end - practice a few times to get used to the feel (they are intentionally balanced the same as regular juggling clubs) and then light 'em up.
I think he wants to quantify the ‘very, very’ in that sentence. If you’ve done one thousand exchanges in a row without a mistake, is that enough? Or, given the horrific consequences of an error, would five thousand be a wiser target?
(As an amateur juggler, my answer would be ‘eleventy trillion’. But I’m pretty addicted to referring to my hands in the plural, so I’m probably the wrong person to ask.)
Shhh! You’ll ruin the magic! 
When he has trained himself out of the habit to try to make saving grabs. Once your instinct is to step back, you can start using chainsaws.
IANAJ, but one of the hardest things to juggle has to be what Penn and Teller do in one of their shows - they take a number of different size and shape bottles, and then break them, and juggle what remains on the neck. They are all balanced differently, and they have jagged edges - not something I would want to play with.
Penn does this, Teller doesn’t. It’s a solo Penn bit.
I think I was watching “America’s Got Talent” or one of the 10 other talent shows running now and they had a juggler that showed he was using a genuine bowling ball by cutting a carrot with it. 
Forget juggling. Using a bowling ball as a cutting utensil is way more talented.
No, the most impressive was when the Flying Karamozov Brothers juggled 1) a pair of shoes tied together, 2) a cardboad tube with a freely moving weight inside, and 3) a half gallon of vanilla ice cream (without the carton).
They deserved their standing ovation for that one.
That had to have been part of their challenge round. Some audiences come up with amazingly difficult challenge objects.
One day, before I die, I will see the Flying Karamozov Brothers live.
Remember, Penn and Teller are (and I mean no offense by this) professional liars. Just because that’s what it looks like they’re doing, doesn’t mean it is. If I had to guess, I’d say that the bottles are probably pre-scored to break in a particular way, such that even though they all started off different, they all end up with the same balance qualities (center of mass and moment of inertia) as each other, and that Penn has already practiced with similarly-balanced objects.
Note that I am not a magician, and have no inside knowledge of how they actually do it, and so am under no ethical obligation not to tell.
While it’s not exactly the same thing, I do and teach beginner poi, or fire chain spinning. My rule of thumb for my students is this: when you can spin for 15 minutes without bonking yourself or getting your chains tangled, you can try lighting up.
This is because a burn only lasts 5-7 minutes, but it feels much, much longer. Also because fire moves oddly, and while lit chains are not technically measureably heavier than unlit, they feel as if they are far heavier (convection currents, maybe? I started a thread on it once, but no one had a definitive answer) and they tire you out more quickly on fire.
So my general rule of thumb for dangerous stuff: when you can do a very similar, less dangerous version for twice as long without making a mistake.
But it sounds like chainsaw juggling isn’t as dangerous as it looks; still, that’s a heavy weight to come down on a head or shoulder should you miss-throw.
My admiration for you seems to grow every time you post…good grief.
Let’s not forget kitten juggling. That would be much harder than anything else, except maybe the tube with the freely moving weight inside, because kittens will try to get away. Also, no one cares about the chainsaw if you drop it, but give a little kitten an owie and the booing starts right away.
Emphasis on beginner. I couldn’t begin to do something like this! But I have about 6 moves I can work into a 7 minute routine, and I can teach you the basics of keeping the chains moving and looking cool…er, hot…at it.
You should come teach our local group. At the last event I went to, one of the gals lost her hula hoop into the crowd. It was quite entertaining. (Note that the whole show was entertaining, and I’m not saying I thought any less of them for a small, yet entertaining, mistake)
I’m pretty sure the answer would be increased drag due to a larger boundary layer (the layer of air that “sticks” to the object as it moves through the air). Do they feel heavier when you’re holding them, or just feel like they have more inertia when you’re swinging them?
Do those juggling chainsaws ever tie the throttle down? It seems like the extra angular momentum from a saw running at high RPMs would be very tough to control.
I watched the Flying Karamazov Brothers juggle live cats once. The cats were obviously quite sedated - no cat is that mellow. They weren’t exactly being flung through the air (it was closer to watching someone do a 3 Card Monte on a table) but the deed got done.
They feel “heavier” when you swing them, but not if you just hold them still. If you swing wild when lit, it takes an extra second or two and some more muscle exertion to move them back into the proper path than when unlit, so yeah, I guess inertia is the right word.
Would a spinning chain (sharp or not) affect how the chainsaw flips in the air? (I’m not sure if “gyroscopic force” is the term that I’m looking for.)
