Shop Vac and RPM - Router Forums
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post #1 of 9 (permalink) Old 02-19-2018, 03:21 PM Thread Starter
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Default Shop Vac and RPM

Hi there,
I'm trying to get my new lock miter bits figured out. When I turn on my shop vac, it seems to me like it sounds like the router loses a bit of power. Should I factor that drop in power as a drop in RPM?
many thanks
stuart
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post #2 of 9 (permalink) Old 02-19-2018, 03:40 PM
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What's the power draw on each? Do you have extension cords in place? Are the router and shop vac plugged into the same outlet, same circuit?

Yes, in answer to your question. If you're setting it at 18k rpm, for instance, and it slows to 16k rpm then you may need to set it at 20k rpm to compensate. But I would be more interested in figuring out why it's slowing down first.

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post #3 of 9 (permalink) Old 02-19-2018, 04:19 PM
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What David said! In spades.
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post #4 of 9 (permalink) Old 02-19-2018, 04:57 PM
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what David said...
and the drop in voltage generates more heat in both units.. not a good plan...

This would have been the week that I'd have finished chewing thru the restraints...
If only new layers hadn't been added....

Stick....
Forget the primal scream, just ROAR!!!
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post #5 of 9 (permalink) Old 02-19-2018, 05:04 PM
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scientific method:
Use a voltmeter , measure voltage on line when nothing runs,
measure with router on, measure with both on.
If it goes down more than about 10 percent, you got a too long,
or too thin power line.
say 100% voltage is 100 % power on router
then 90 % voltage will give 81 % power at router.

You can see it changes fast.

Approximative explanation:

P (power)= U x U ( U= voltage) So it is U at power of 2 divided by resistor value.
--------
R

It is right for pure resistors like a calorific heater, but It' s an aproximation, because with an universal motor, the power reduction is worse than that.

so if U= 1 (100%) then U to a power of 2 is U x U = 1 x 1 = 1 (100 %)
If U= 0.9 ( 90%) then U to a power of 2 is U x U = 0.9 x 0.9 = 0.81 ( 81%)

That shows how fast a 10 % voltage drop gives a 20 % power loss.
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post #6 of 9 (permalink) Old 02-19-2018, 08:54 PM
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One other question. Where is the vac sucking from? Near the bit or out of the bottom of a box?

Someone I consider a master woodworker once told me that a master woodworker is not someone who never makes mistakes. He is someone who is able to cover them up so that no one can tell.
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post #7 of 9 (permalink) Old 02-19-2018, 09:06 PM
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Quote:
Originally Posted by Stuart Wallace View Post
Hi there,
I'm trying to get my new lock miter bits figured out. When I turn on my shop vac, it seems to me like it sounds like the router loses a bit of power. Should I factor that drop in power as a drop in RPM?
many thanks
stuart

Stuart, I had a similar problem and added two more circuits. I started blowing breakers. I knew from the start at this house I was going to have to add circuits and kept putting it off until a couple of months ago. You might as well fix your problem now.
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Measure once cut twice and it's still to short.
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post #8 of 9 (permalink) Old 02-19-2018, 09:06 PM
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Plug them into different outlets, aee if there is any change.
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post #9 of 9 (permalink) Old 02-19-2018, 10:05 PM
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Quote:
Originally Posted by Herb Stoops View Post
Plug them into different outlets, aee if there is any change.
Herb
but on different circuts
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This would have been the week that I'd have finished chewing thru the restraints...
If only new layers hadn't been added....

Stick....
Forget the primal scream, just ROAR!!!
"SNORK Mountain Congressional Library and Taxidermy”
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