Ping Leon: Design Q on SawStop

There seems to be two mechanical strategies at work in the SawStop, of translation, and of rotation, ie, retracting the blade, and stopping the rotation.
It seems to me one would be sufficient, with retraction having the advantage of being non-destructive. Not sure if the blade is direct drive or belt drive, but if it was belt drive, the retraction could all the more rapid, since you would not have to retract the mass of a relatively heavy motor. In fact, if designed properly, you could proly have only the blade and its bearing retract, along grooved guides of some sort, allowing for a very rapid acceleration from whatever force is applied -- presumably springs? But could also be pneumatic or hydraulic, or solenoidal.
Unless the deceleration of rotation is just an inherently faster process than the retraction process. But, from what I see, it seems the retraction is occurring FIRST, anyway, to initiate the destructive crash, so mebbe the rotational issue is irrelevant??
Now, if rotation is still an issue, wouldn't a caliper/rotor brake type deal be as fast as his collision process, AND be non-destructive? Mebbe multiple calipers.
Oh, oh, but then he wouldn't be able to sell new crumple ditties at $70/pop.....
Mebbe you could run this by (G)ass, ask him to send me $5 if he likes the idears. Or mebbe just invite me to one of them 'spensive luncheons, where he's twisting CONgress's arms on safety'n'shit, you know, for all the li'l children....
--
EA




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In the videos I've seen the blade is fully stopped, while the retraction is only partial, more like the retraction has only started. And I think one problem with relying only on retraction would be that it's not going to be fast enough to get all or enough of the blade out of the way. You could do the math and find the force necessary to move a given mass several inches in 1ms.
A side question is why have the retraction at all. I guess if you're flopping a whole arm down on the saw, it would prevent injury from just hitting a stopped blade.

It would have to be one hell of a caliper brake to stop that spinning saw in 1ms. With the way it's implemented now, at first contact of the jamb the saw is stopped dead.

You really think he didn't think of a simple brake, like they have on say lawn mowers, first?
 Or mebbe just invite me to one of them 'spensive luncheons, where

Or better yet that anyone involved in this is interested in answering your questions, given all the insults and names you've called them?
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On 12/8/2012 9:56 AM, snipped-for-privacy@optonline.net wrote:

Maybe if you two watched the video you'd understand. The blade is stopped, and that is actually part of the retraction mechanism. The inertia is dissipated by retracting. The retracting saves the finger as well since it is pulling away from the finger.
The design as it stands is very good, your ideas are not. BTW this is a top notch saw, so no it is not direct drive. The workmanship on all of these saws exceeds what we now currently have from the standard non-euro options.
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"tiredofspam" <nospam.nospam.com> wrote in message wrote:

Really? And you know all this..... how??
--
EA




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On Dec 8, 10:35 am, tiredofspam <nospam.nospam.com> wrote:

I did watch the video. Nothing in the video shows exactly how the blade retracts, what it's attached to beneath the saw, etc. And there isn't just one video, so how would you know what videos anyone did or did not see.

OK, using the momentum of the saw to retract the blade makes sense. Is that all that causes the retraction or is there something else, eg spring involved?

I think you're confused. You replied to my post. I did not propose changing the SawStop. I'm fine with it. It was EA that was proposing the new ideas and simply pointed out some of the obvious issues.
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"tiredofspam" <nospam.nospam.com> wrote in message wrote:

I've seen the actual patent, IIRC...
I can't remember the details about the sensing mechanism...but...
A block of aluminum acts as a brake, effectively stopping the blade dead in it's tracks by more or less directly engaging six teeth or more all at the same time (depending on blade pitch) which equates to maybe 10 degrees of rotation...
--if you do the math, what you'll find is that you'd have to be moving your finger into the blade at speeds that are simply not humanly possible in order to do anything more than to draw a very slight amount of blood.
Kind of like the bullet that you never heard...

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