SawStop inadvertent brake activation causes

[Tpt life 2791]

Is grounding required to register difference in potential? Does this require footwear that does not isolate, or contact with the tables surface with a hand? Reading you comment Gee is what got me thinking. 

[Chestnut 5731]

On 2/27/2021 at 8:54 AM, Mark J said:

Still non-flesh triggers happen.  It would be a nice development if they could figure out a way to pull it off while preserving the blade.  Or if Felder could make their system cheap enough for people to actually buy.

Bosch figured it out sawstop served them with a lawsuit. Remember the reaxx contractor saw? I don't think sawstop has much intention of making their system better or they'd have done it by now.

[wtnhighlander 7752]

I'm not sure the Bosch system would work properly for the greater mass of a cabinet saw driveline. Portable jobsite saws are pretty low mass, so their explosive cartridge (compressed gas, wasn't it?) had enough power to drop the blade below the table, but SS would need a significant rework of their patented system to manage that without using driveline inertia as part of the motive force to drop the blade. I'd like to see how Felder does it, I'm guessing there is a massive spring involved, somehow.

[JohnG 1246]

8 hours ago, wtnhighlander said:

I'd like to see how Felder does it, I'm guessing there is a massive spring involved, somehow.

I thought theirs was electromagnets? Not sure they ever gave much detail though. 

[drzaius 2635]

2 hours ago, JohnG said:

I thought theirs was electromagnets? Not sure they ever gave much detail though. 

Nope, used a gas cartridge that was good for 2 activations.

[JohnG 1246]

5 hours ago, drzaius said:

Nope, used a gas cartridge that was good for 2 activations.

Sorry, I meant Felder’s. I meant to only quote that part.

[Mark J 2272]

As I recall resetting the Felder system after an activation does not require any replacement part or consumable.  But as I recall it's also $50k.

[Chestnut 5731]

15 hours ago, wtnhighlander said:

I'm not sure the Bosch system would work properly for the greater mass of a cabinet saw driveline. Portable jobsite saws are pretty low mass, so their explosive cartridge (compressed gas, wasn't it?) had enough power to drop the blade below the table, but SS would need a significant rework of their patented system to manage that without using driveline inertia as part of the motive force to drop the blade. I'd like to see how Felder does it, I'm guessing there is a massive spring involved, somehow.

I haven't dug through engineering drawings to see how they work. My gut instinct is that it's not that different. I could probably figure out a way to make it work. Man now i want to examine how they are both built. The sawstop contraption looks like it'd work easily with the gas cylinder as it's quite light looking. Using springs and a sear it'd be pretty easy to offset the weight of a swinging component and the spring would help keep the blade below the table....

[wtnhighlander 7752]

Drew, it may just be that the brake reduces injury a bit more. There is a slow-motion video floating around, of a SS tripping. You can clearly see that the blade stops long before it drops. And is clearly under high stress, I would not try to re-use it. Of course, at normal speed, the blade disappears in maybe one frame of video, so the added time is relatively short.

[Chestnut 5731]

Seen the video multiple times. I still stand buy the brake being unnecessary. The Felder and Bosch design were retracting the blade fast enough to only leave a scratch (very similar to the SS) but neither damage the saw blade.

I don't think that Gass intended the brake to retract the blade. The brake was the main function and the retracting was a secondary result because the energy is easier to deal with if it's redirected. Though I doubt very few people will truly know the answer to this question. The evidence is the blade comes to a complete stop before it retracts. If retracting the blade was his main goal i strongly feel the design of the saw and safety system would be dramatically different EG Felder and Bosch. Also the blade would still probably have some rotational motion as it's retracting. Again I haven't had a chance to closely examine the Bosch, Felder, nor sawstop system in person.