An ohmmeter as a tool in a wood shop?

[JPG]

I built a test setup to test DC motors and controllers many years ago. As a separate task, I put several different Shopsmith 3/4 HP and 1 1/8 HP motors in this test setup. Measuring the voltage and current amps with various loads, I found the 3/4 HP motor could use less amps some times at different loads but less than 10% difference. I have always used the 3/4 HP motors in my personal Shopsmiths. I find proper alignment and sharp saw blades are must more critical than HP for the Shopsmiths.

Gotta wonder if rpm was also 'observed'.

[joshh]

But...this guy on the internet told me we don't have to worry about motor efficiency since we work in the vacuum of space...and bearings have no friction...and...

Oh wait

[JPG]

But...this guy on the internet told me we don't have to worry about motor efficiency since we work in the vacuum of space...and bearings have no friction...and...

Oh wait

He the same guy with a bandsaw blade square to table checking procedure?:D

[robinson46176]

Back in 1975 a wholesale salesman was in my store trying to convince me to carry his line of vacuum cleaners. They were a quite good line in those days (Royal) (and we did carry them for a number of years). During the conversation I mentioned that I knew that HP numbers were really pretty much irrelevant to vacuum cleaners but since most brands were waving them about I wondered what number they claimed for theirs. Without hesitation he said 4 HP... Since most others were claiming numbers like 1 1/2 or 2 HP at the time I asked him how he arrived at that figure. His response was: "I just figured that it was substantially higher than what anybody else was claiming"...

Shrug...


.

[billmayo]

[quote="JPG40504"]Gotta wonder if rpm was also 'observed'.]

Of course, that was very important on the DC motors. I even had a few temperate prods that I attached to the motor and motor air flow. I had quite a setup to where I could even come close to stopping a motor if desired. A neighbor who did destructive motor testing for a few companies helped me set it up with some of his equipment. I remember spending hundreds of hours playing with setup over a few years. I was never satified with the results trying to install DC motors and controllers in a Mark V headstock. The inductive motor maintains its RPM quite well compared to the DC motors. I stopped loading the Shopsmith motors when the Amps went over 14 amps with very little RPM drop or the temperate rise started to look too high. I figured this was a little over 100% load on the motors. This was about 7 years ago and I have no idea what I did with this setup later. I know I quite doing any testing around the time the PowerPro was introduced. I may have given most of the equipment back to my neighbor. I know I had a lot of fun for a few years. I am still finding unsuccessful remains and parts from that time. The price of 3 phase equipment kept me from testing in that area.

[artlinux]

Back in 1975 a wholesale salesman was in my store trying to convince me to carry his line of vacuum cleaners. They were a quite good line in those days (Royal) (and we did carry them for a number of years). During the conversation I mentioned that I knew that HP numbers were really pretty much irrelevant to vacuum cleaners but since most brands were waving them about I wondered what number they claimed for theirs. Without hesitation he said 4 HP... Since most others were claiming numbers like 1 1/2 or 2 HP at the time I asked him how he arrived at that figure. His response was: "I just figured that it was substantially higher than what anybody else was claiming"...

Shrug...

.

Robinson46176, I enjoyed your salesman story and it reminded me of how little i know about lots of things. Although I am quite comfortable about electrical topics, the SS motor and drive system includes more of those things I know less about. That enough power delivered to our work sites (cutting blades, planer blades, etc.) is mostly what we care about. I suspect that the varriable speed belt drive system cosumes some of the motors output power & that more cutting power is really required. Calculating when the motor and drive system has suitable efficiency is important in the SS design and it is beyond my ability to test the whole system in my workshop.

The Power Pro design of motor and control system seems to be that winning combination for the SS power plant that I have been needing for a long time. It will probably remove most of our motor and power availability discussions from these posts.

For what it was worth, I was ready to discuss other electrical issues that affect us with the starting point as follows but I should have stopped with my previous paragraph....The maximum continuous current that can be drawn from a 15A circuit breaker is 12A and from a 20A circuit beaker is 16A regardless of it being part of a 120 or 240V circuit. Peak currents can be drawn for short periods of time without tripping a breaker in good condition during events such as the higher motor starting inrush currents that do not last for many cycles. This current limit is the primary limit on motor hp size.