Shopsmith Forums

I got to thinking about blade brakes and some other tool braking applications and was wondering if any one was using such a thing. I had a RAS with a mechanical blade brake and while it was not a SawStop stop it did prevent the blade from coasting along "forever"... I do often have a faceplate mounted on the SS SPT stub for both hand turning the quill and dragging it to a quicker stop but in some applications it gets in the way.
I got to thinking about putting a simple mechanical brake on the jointer stub on the idler shaft. I basically NEVER use that. In looking at ideas I ran across this go-kart disk brake. I had also thought about a small motorcycle front disk brake.
http://www.northerntool.com/shop/tools/product_200323386_200323386


.

seems like a good idea at first glance. But how would you mount the brake caliper? I suppose that you could design something that would mount it to the belt cover but I don't think that the sheet metal would stand up to the stress. I thought the same thing about the new Power Pro. Braking could be achieved by reversing the field polarity and causing the spindle to decelerate quickly but those pesky inertial forces get in the way again! It may be achieved by programming but that is only a guess.
Bill V

wa2crk wrote:seems like a good idea at first glance. But how would you mount the brake caliper? I suppose that you could design something that would mount it to the belt cover but I don't think that the sheet metal would stand up to the stress. I thought the same thing about the new Power Pro. Braking could be achieved by reversing the field polarity and causing the spindle to decelerate quickly but those pesky inertial forces get in the way again! It may be achieved by programming but that is only a guess.
Bill V

Since they can program them to 'ramp up' to speed, ramping down should also be possible. In fact, they are probably already programmed that way, but with a gradual rate of deceleration.

wa2crk wrote:seems like a good idea at first glance. But how would you mount the brake caliper? I suppose that you could design something that would mount it to the belt cover but I don't think that the sheet metal would stand up to the stress. I thought the same thing about the new Power Pro. Braking could be achieved by reversing the field polarity and causing the spindle to decelerate quickly but those pesky inertial forces get in the way again! It may be achieved by programming but that is only a guess.
Bill V

I was thinking of mounting the caliper to a bracket that mounted to the belt cover to keep it next to the headstock but so that all of the braking torque was transferred by lever down to the way tubes.
The variable speed drive on the 10's slides along the way tubes on ring mounts and just slides along with the headstock.

I have also seen homemade carts that just used a Vee belt pulley and a short length of belt that was anchored at one end and tightened for a stop from the other end. I have no idea how long those last. There are also small drum brake assemblies available that use an external contracting band.


.

JPG40504 wrote:Since they can program them to 'ramp up' to speed, ramping down should also be possible. In fact, they are probably already programmed that way, but with a gradual rate of deceleration.

Sudden hard stops can be hard on a number of things including the tightness of a saw blade. I suppose that is why my old RAS just rubbed a brake pad against the side of the saw blade. That and it was easy to do...


.

Years ago I worked at a semi trailer manufacturing plant. We had a seven and half horse DeWalt RAS. It was a monster and you didn't want to get it mad at you, but that's another story. The saw originally had a blade brake that use electro magnets to apply the brake shoes. Our problem was that we cut aluminum extrusions. Aluminum saw dust would short these coils in a short time. We solved our problem with a commercially available product. It was triggered by the control circuit being shut off. Here is the main point, the electronic brake applied a DC voltage across the windings. This voltage had to be adjusted very carefully, otherwise it would stop the blade so quickly the arbor nut would loosen. And if my memory is right that was a 20 inch carbide blade and you wouldn't want that coming off. Once adjusted it worked very well for many years. So if you are thinking of a blade brake look into these.

Many of these discussions cause me to jump up and run out to the shop to see what I can do. Not this one. I'm just going to concentrate on staying out of the "red zone" and let some one else devise a brake system.

Improving dust collection on the tilting table system with its present dust collector is enough of a nightmare.

dusty wrote:Many of these discussions cause me to jump up and run out to the shop to see what I can do. Not this one. I'm just going to concentrate on staying out of the "red zone" and let some one else devise a brake system.

Improving dust collection on the tilting table system with its present dust collector is enough of a nightmare.

This is not a high priority for me either and I am not looking for a sudden stop brake, just something like a drag down brake to reduce coasting time. Actually most of the time a smooth hand-wheel is plenty. I might try just putting a smooth hand-wheel on the jointer stub/idler shaft. Since I never use that shaft it would not get in the way like one on the upper stub does at times.
I do have a SS jointer (just because ) but don't normally use it.
When I get an idea I look at all kinds of options and try to stay as open to "outside of the box" ideas as I can.
Sometimes I get into an idea hot and heavy but after I look at a big herd of options I find that I have pretty much gone off of the whole notion...
In this case I am thinking of it as more of a safety thing (not a time saver) that might take away some of the urge to "reach in" to move a piece of scrap or small cut-off. I am always telling woodworking guys I watch on TV to "get your fingers back, that blade is still coasting". Of course they can't hear me but I still tell them.

If you look at the Sawstop you see they stop the blade instantly but between the blade and the motor arbor is a belt and pulley system.

I would think if you stopped a motor that quick you would stand a good chance of ruining it. Either twisting the motor shaft or spinning the rotor on the armature.

To prevent damage you can't allow the blade teeth to move any significant distance once it contacts flesh. Sawstop accomplishes this two ways pulling or dropping the blade away from the flesh and slamming it into block of aluminum to instantly stop it.

I don't know but I would think if you stopped a Shopsmith blade quick enough that it didn't travel any significant distant against the flesh, something in the head stock would come apart.

Maybe one of our math guys will figure how far a saw tooth moves on a 10 in diameter saw blade turning at say 3400 rpm. in an instant to give us an idea of how fast the blade would have to be stopped to prevent significant damage.

Newer mount bicycles have disc brakes. Maybe that would work.

$70 http://www.amazon.com/Avid-Mechanical-B ... B001AYOS62