2007-11-17 02:40:02 · 4 answers · asked by Anonymous in Science & Mathematics ➔ Engineering
Usually a fan's directly driven by the motor using a common shaft. Very little resistance - and as the fan starts to slow down, the resistance drops as well. So it can spin for a little while.
Most hand held grinders have at least one or two gears driving the head. The gear drive gives a lot of resistance, which causes the head to slow down quickly. But not immediately.
If you have a grinder that stops right away, it's probably a higher end model with an internal brake. The brake engages as soon as power is lost and (obviously) forces the unit to stop spinning, since a spinning grinder is a safety hazard. Many rotating saws do the same thing.
2007-11-17 07:35:45 · answer #1 · answered by Doug B 3 · 0⤊ 0⤋
Are you comparing two different products or talking about a grinder with a fan as part of its equipment?
If you are talking grinder (like meat grinder or sewage grinder) it runs heavily loaded with tis grinding activity. If it is stopped while not empty the resistance from the substance it is grinding will be enough to stop it. An air fan on the other hand moves the low dentisty substance of air and will continue to spin because that is not much resistance.
A fan (more properly a blower) attached to a tool grinder could continue to be powered to aid in cooldown.
Most of the smaller grinders however use a fan blade on the shaft of the motor that stops turning when the grinder motor stops.
2007-11-17 03:10:53 · answer #2 · answered by Rich Z 7 · 0⤊ 0⤋
Fans tend to be higher-inertia loads, that can coast slowly to a stop, while grinders may have lower inertia.
I know of some benchtop grinders that take a fairly long time to coast to a stop.
The fundamental answer is that the device which stops faster has its mechanical energy removed more quickly via continued output work (i.e. blown air) or friction than the slower-to-stop device.
2007-11-17 03:36:40 · answer #3 · answered by Steve W 5 · 0⤊ 0⤋
The fan cools down the motor so that the insulation does not burn out.
The motor gets hot while working (grinding) and needs airflow for some time after that so that hot spots do not develop, which would damage the insulation on the wiring --> short circuit --> ruined motor.
2007-11-17 02:49:42 · answer #4 · answered by Nigel M 6 · 0⤊ 0⤋