"Ed Huntress" wrote in message
...
On Thu, 2 Nov 2017 13:38:23 -0400, Leon Fisk

wrote:

On Thu, 2 Nov 2017 13:24:25 -0400
Tom Gardner wrote:

I have a new 3.5hp (I think) "Works" largest 14" chainsaw that I
want to
use the motor for a project. I need to know the RPM. I've had no
luck
researching this and I no longer have an RPM meter. I imagine all
chainsaws have similar rpm. I need to get the ratios on timing
belt
sprockets close to optimal. If this works, you will all be dazzled
by
my brilliance!

Affix something to the chain that sticks out a little. Now make
another
attachment or hold something close by that will hit it. Like the old
clothespin, playing card and bicycle spokes. Turn it on and record
the
sound. Use something like Audacity to measure the frequency. Viola!

A big, 16" bar, 15A corded electric Makita chainsaw has a no-load
chain speed of 2900 ft/min -- 48 fps. I'd use my digital camera in
timed multi-shot mode (10 frames/sec., I think) and take a series of
photos, and then measure the distance between a marker in two
sequential shots. You'd have to do it multiple times to be sure you
get two visible, sequential photos with the marker.

Then work backward from the sprocket and chain pitches to get the
motor rpm.

(Yes, there must be a simpler way.)

For reference, I saw specs on a Greenworks corded 14.5A saw that
said
6000 rpm. Another saw said 5500 rpm. A Remington Versa 12A 16" says
3200 rpm.

If this is a cordless saw, all bets are off. As for 3.5 hp...that
sounds like Sears or Ridgid horsepower to me -- like 22A, if they're
talking gross horsepower.

--
Ed Huntress

I've seen a rating in "electrical horsepower" calculated from how much
juice it pulls, probably without considering efficiency or power
factor.