When using my Kobalt CMS, I notice a large spark from the motor compartment when I turn off the saw. Sometimes it looks like it fills the whole compartment. Is this a sign the brushes need replaced?
Puckdropper
Good place to start.
Might not be seated properly.
Lew
Sounds like a normal condition when an electronic brake in engaged.
Read your owner's manual. Is this a saw with electric brake?
"DanG" wrote in news:5opvm.443888$Ta5.188839 @newsfe15.iad:
The saw indeed has an electronic brake. If that's normal behavior, I'll let it be.
Puckdropper
"Lew Hodgett" wrote in news:001c03e2$0$24199 $ snipped-for-privacy@news.astraweb.com:
I took the brushes out, blew out the sawdust in the brush chambers and put them back. The big spark is gone, and I think I picked up a little missing speed.
I'll have to add that to the occasional maintenance list. It only takes about 2 minutes.
Puckdropper
Electric brake shorts out the motor winding and it generates current in the winding in reverse - generating voltage - and sparks if the brushes are not smooth on. The short isn't hard, but soft through a low resistance value.
Good f>> When using my Kobalt CMS, I notice a large spark from the motor >> compartment
I suspect that the fix will be short lived. I think you are trying to fix a normal condition.
Sometimes my old Skil looks like one of those 4th of July sparklers inside the case. I don't know if it's normal or healthy... I just know I won't use it around open cans lacquer or paint thinner. :-)
You would probably do well to not use any thing that sparks around flamable vapors. I am still in wonderment having retired from the automotive industry how GM prevented gas tank explosions. They used submerged electric fuel pumps and the gasoline literally went through the motor and brushes. No, gas tanks do not always have gasoline in them so being constantly submerged is not the answer.
I'm guessing the pump was low enough as to always be submerged, even when the tank was "empty?"
Reminds me of the Mythbusters episode in which they *could not* get a gasoline trail to ignite with a burning cigarette, like you see in the movies. Apparently, smoldering tobacco embers are not hot enough to ignite gasoline vapors.
Another interesting fact from my electrical engineer friend who works for a huge electric producer... Those giant electric turbine generators are cooled with direct water immersion. Turns out pure H2O doesn't conduct electricity. It's all the minerals and other stuff in water that does.
Even when the tank is "empty" it's not empty. It's full of gasoline fumes, which without air (oxygen) aren't dangerous at all. ...and there isn't any air in there either.
Liquid-fueled rocket and jet engines commonly use the fuel and oxidizer as a coolant.
The water going through turbines is hardly pure. I doubt water touches the generator windings themselves.
No, gas tanks do
Nope, mentioned that above, of millions each year built this way there had to be a few thousand that went with out caps and the gas evaporated.
I'm not talking about the water running through the tubes from a dam, that spin the turbines. He was specifically referring to steam powered generators, btw.
And yes, he said they use pure H2O.
"Had to be?" Sounds pretty speculative. :-)
Yeah, there is oxygen/air in there, every time you open the tank some gets in. Besides, the tank would collapse if it were totally sealed, Air has to displace the disappearing gasoline.
But gasolinr does on a Gm electric fuel pump. My fuel pump in on my 1975 Olds failed. I dropped the tank and replaced the pump, it is attached to the tank unit/gas gauge float assembly. I cut it open and the thing was spottless inside but the brushes were totally worn out. Gasoline went in one end of the motor and exited on the other. On one end of the motor was the plastic pump.
Nope. Not any more. The engine controls recycle fumes back to the tank. Tanks have been sealed for decades.
Sure. No one was arguing that point. It's hardly dangerous.
I was thinking more about hydro-electric turbines, which are also water cooled.
Nothing is pure. ;-) In this case it has to be as close as possible because of the process. If there were any impurities they would be deposited in the "boiler". Not a good thing in a nuke, either. ;-)
Yes the engine compartment does recycle fumes back to the tank but there is a lot of AIR that goes with it. Additionally there are lots of peole driving around with lost gas caps, check engine lights and all. And again, the tank is not sealed when you open it up to fill it with gas. There is just way too much of a chance of the perfect combination for the electric motor to set off an explosion if there was not a fool proof way to arrest the spark. How that is accomplished even the Olds factory rep could not explain when I was the service sales manager back in the 80's.
Obviousely but the simple explanation has not yet been explained to me.
I was in the automotive service business from 1972 to 1995. I saw it all.
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