What is the logic of banging DOWN on a crankshaft to remove a flywheel?

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Seriously, he said he SAW the flywheel bend! If he could have actually seen it bend, it's most likely cracked. My guess is he didn't really see it bend.
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In my misspent youth, I tried big gear pullers on mower flywheels & as described they will flex and still not release. I have seen one bend, & put it right back into service. It never showed any sign of the abuse and served until the piston ring seal was so poor you had to mow with a screw driver in your pocket to adjust the mixture as it warmed up, at which point the entire rig was retired. I think the fragility of the flywheel is badly overstated.
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On Thu, 15 Jul 2010 06:06:36 -0700 (PDT), Eric in North TX

One lone example is statistically of absolutely no consequence. I know a guy who chain smoked unfiltered camel cigarettes for over 60 years and didn't get lung cancer, too.
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On Jul 15, 8:34 am, snipped-for-privacy@nowheremonfrere.com wrote:

True but it does prove that it isn't an absolute death sentence.
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On Thu, 15 Jul 2010 06:46:29 -0700 (PDT), Eric in North TX

Well, I suppose the Darwin Awards can always use some fodder.
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wrote:

Using a gear puller alone (by cranking it hard rather than using a hammer) will warp the flywheel and perhaps cause stress fractures.
When you use a proper prybar and hammer, the prybatr is lifting at the center, not an inch away from the center. The tip of the prybar should be against the crankshaft.
The OP now has a flywheel of very questionable safety.
Darwin was a pretty smart guy.
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Asking the same question here, and getting the same answers, isn't going to change anything.
To add something that hasn't been mentioned (or I didn't see it). The inertia delivered by the hammer affects the crankshaft, not the flywheel (you are preventing it from moving).
At the end of the day you will just have to accept the fact that it does work when done properly and won't cause damage to anything.
Harry K
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Why were you anywhere near the intake manifold, you should have been leveraging against the main chassis of the engine!!!
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On Mon, 12 Jul 2010 06:22:19 -0700 (PDT), hr(bob) snipped-for-privacy@att.net wrote:

I understand your concern!
At first, I leveraged UP with the prybar on the aluminum engine, then moved about 60 degrees and leveraged again (all the while uselessly banging DOWN on the flywheel puller contraption from ACE on the flywheel).
When I moved the third 60 degrees, I didn't realize it but now I was at the front of the mower where the carberator and air filter are, which has a plastic pipe (painted the same color as the aluminum engine) which is the intake manifold.
In just a split second, the plastic pipe collapsed, along with a bolt which snapped in half holding it to the opening for the intake valve.
It was exactly at that point where I realized the advice to bang DOWN on the crankshaft while lifting UP on the flywheel (thereby leveraging DOWN on the soft engine parts) was sheer folly.
It was only then I started wondering about the logic of it all. Of course, prying UP makes sense to remove a flywheel ... but what does banging on an immovable crankshaft going to do?
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Try it.... has worked for me, for years. Yes, the crank shaft goes down.
The fit between the flywheel and the crankshaft is a slow taper. You only have to bump the crankshaft down 1/8 inch or less, and then the friction fit between the two shears. And the flywheel lifts off.
I rather doubt that anyone has advised to bang down on the flywheel.
--
Christopher A. Young
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On Mon, 12 Jul 2010 09:55:16 -0400, Stormin Mormon wrote:

One end of the crankshaft is sticking up in the air with the nut loosly put back on (to protect the threads) while the other end is firmly attached to the lawn mower blade. The piston is in the middle.
Where "down" can it go?

That's a LOT of distance for an immovable flywheel. Do you bump it back UP 1/8th of an inch when you reassemble?

I agree. What everyone said (and what utterly failed for me) was to pry UP on the flywheel and bang DOWN on the crankshaft.
What worked (for me) was to tap the pre-existing holes and lift up on the flywheel leveraging on the center of the crankshaft with a harmonic balancer puller with two 1/4 x 20 bolts and washers (that bent like potato chips from the force). :)
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The 1/8" was a gross exageration. It is only a few thousandths but that is all that is needed. There is _no_ mechanical assemblage that does not have a bit of "play" in it.
Harry K
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On Jul 12, 6:55 am, "Stormin Mormon"

Why don't you just accept the _fact_ that it has worked when done properly since B&S engines were first built? That it is also done by almost every small engine mechanic that has ever worked on them? You have been given clear explanations on why it works, You are just being obstinate in refusing to believe them.
Harry K
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On Sun, 11 Jul 2010 21:19:22 -0700, James H. wrote:

They make a tool you can screw on the end of the crank to bang on so you don't mess up the thread at the top. The physic is shock as in an impact wrench will drive the screw tighter or looser with less effort and less chance of breaking things. In the plumbing business there is the term "warming up a pipe joint" when using steel pipe and fittings to loosen the joint by banging on it when you can't wrench it apart. Same thing with a lid on a glass jar that you can't loosen. Smacking it down on a hard surface loosens it enough that you can then unscrew it. They are all interrelated.
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re: "Same thing with a lid on a glass jar that you can't loosen. Smacking it down on a hard surface loosens it enough that you can then unscrew it. They are all interrelated."
I dunno...
I always smack the bottom of the jar with the heel of my hand and listen for the "crack".
It's my understanding that that releases the vacuum that keeps the jar sealed tight.
I'm guessing that there is no vacuum involved in the removal of a fly- wheel.
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On Mon, 12 Jul 2010 12:06:31 -0700 (PDT), DerbyDad03

You can also remove the cork from a wine bottle by banging the bottom of the bottle sharply, several times. The cork will pop out. Be careful not to break the bottle!
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On Mon, 12 Jul 2010 14:57:21 +0000 (UTC), Jeff The Drunk wrote:

I bought that tool; it was useless.

While this shock and awe effect didn't work for me, I do understand what you're implying.
Basically, from Physics 101 back in college, dynamic friction is less than static friction.
So, what you're saying, I think, is by banging on the flywheel (actually banging on anything would work as well), you set up vibrations, which allow things to move with just a little bit less friction.
Well, at least that explanation makes sense. It didn't work. But it makes sense! :)
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On Sun, 11 Jul 2010 21:19:22 -0700, "James H."

Tradition.
Passed down by generations.
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And misquoted by some. Mower repairmen don't bang down on the flywheel.
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On Mon, 12 Jul 2010 18:09:52 -0400, "Stormin Mormon"

The OP's subject is bangin' his crank. He mis-spoke about the flywheel.
No one suggested he bang the flywheel
Like I said before, it's tradition to bang on the crank.
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