Electric chainsaw motor

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!
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On Thu, 2 Nov 2017 13:24:25 -0400

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!
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wrote:

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.
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On Thu, 02 Nov 2017 14:29:51 -0400, Ed Huntress

Remove the chain and take the thing to an RC hobby shop. They will for sure have optical tachs for sale. They will probably check the RPM for free if you ask nicely. Make a constrasting mark on the sprocket before you bring it in. Maybe color half the sproket with a black Sharpie. Eric
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wrote:

I've seen a rating in "electrical horsepower" calculated from how much juice it pulls, probably without considering efficiency or power factor.
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On Thu, 2 Nov 2017 16:18:31 -0400, "Jim Wilkins"

I think that some of them, including Ridgid, don't even go that far. They stall it and measure the current; multiply by the voltage; divide by 750; and claim that as "horsepower." My Ridgid shop vac draws, I think, 10A when it's running. But they claim it has "4.25 [peak] horsepower."
HA-Ha-ha-ho!
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wrote:

We should call that "puke" horsepower since the motor is about to toss its magic smoke..
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On Thu, 2 Nov 2017 18:30:47 -0400, "Jim Wilkins"

Yeah, that would be a better term for it. This is what Popular Mechanics said about it in a shop-vac comparison. To me, this is unbelievable:
"In addition to being designated by capacity, most wet/dry vacs carry
think that means a vac motor is as powerful as a garden-tiller engine, think again. Like many other consumer-grade tools, the horsepower rating is modified by the word "peak." This indicates the electrical draw at the point where the motor is overloaded and stalls. The upshot? Horsepower ratings aren't the most accurate way to compare wet/dry vacs. Looking at amperage makes more sense."
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wrote:

Well, the motor is physically able to do it, just not for long. Kettering made the automotive electric starter practical by designing for brief peak power, 5 HP from a motor smaller than a 1/2 HP continuous-duty motor.
-jsw
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On Thu, 2 Nov 2017 20:26:14 -0400, "Jim Wilkins"

OK, but this isn't real horsepower they're talking about -- even for a minute. They're defining "horsepower" as current times voltage (/747).
But if that's "horsepower, then you could have a really big power resistor that developed 10 horsepower. <g>
That electrical value is "power," but it's just *potential* horsepower. If you measured actual, kinetic horsepower, in terms of torque times rpm, it would be a minute fraction of that. If the motor is stalled, there's no real horsepower at all.
I wonder if Sears started that practice? That was the first place I remember seeing it.
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wrote:

I thought they measured the peak power at the motor's breakdown torque, just before speed drops. http://industrialelectricalco.com/wp-content/uploads/2014/01/nema-abcde-torque-curves.pdf
I have a 5.5HP, 3750W generator that struggles to start a 1/2 HP motor on an air compressor, as long as the tank pressure is low. I can't measure the compressor motor's torque vs RPM curve but it clearly is drawing that much electrical power at startup.
-jsw
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On Thu, 2 Nov 2017 22:15:02 -0400, "Jim Wilkins"

That's a 10x start-load! I've read that motor startup uses 4-10x the current, but most I've seen were closer to 4x. That's a biggie.
Have you tried an idler pulley setup to remove the flywheel load from the motor on startup?
Is it time to plumb in an unloader/pressure switch, or does it already have one? http://tinyurl.com/yb6f8hgu
Any way to wire in a start cap to help with the current onrush?
Have you verified the genset specs under load?
Are you trying to fix this, or is it posted here only as info, since the genset does start the compressor?
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wrote:

The compressor motor has a starting cap.
I replaced the 1970's Load Genie unloader and swapped the copper tube that may have been stressing it for rubber power steering hose rated 175PSI, 302F but still don't hear the hiss of it unloading, however the compressor works fine on grid power. I only noticed the no-start during a long power outage.
If I have to inflate another tire on someone's neglected generator during an outage I can loosen the head outlet fitting or use the 12V compressor from the car.
-jsw
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On Fri, 3 Nov 2017 12:40:20 -0400, "Jim Wilkins"

So do you hear the hiss when on grid power? Could the resiliency of the rubber hose bypass the function of the unloader? I haven't seen a crossection of the valve, or had one apart, so I'm not certain how it works. It sounds like there may be a spool in there which opens the check valve to allow filling, and it then releases the valve and covers the orifice/uncovers the vent orifice when the pressure switch turns off the compressor motor.
If it's only affected after a power outage, could the start cap on the motor be leaking down?

I finally bought one of those 12v jobs. Haven't had a flat for 30 years, but the time-before-last when I did, the spare was down. After that, I regularly thumped the spare to verify air. Now, my Tundra spare and the 4 on the ground have pressure sensors. Handy!
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wrote:

No, Larry, during an outage I have only the 30A or so max from the genny to start the motor and that isn't enough to start it under load. When the power is on this house can pull 200A from the grid all day, the neighborhood was originally wired for electric heat.
The washing machine also won't start on 30A unless I push the spring-tensioned motor inward to let the belt slip.
-jsw
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On Sat, 4 Nov 2017 19:00:46 -0400, "Jim Wilkins"

The way you said it was...curious. "long outage"

Mine was wired that way, too, and I absolutely hated the baseboard crap. The first thing I did was spend $9,000 to toss the 240v radiant heat, put in a 96% efficient gas heater with A/C, pull out the single glazed aluminum windows and put in dual-glazed PVC windows, and get all-new, -efficient- kitchen and washroom appliances. That gave me 2 new dual circuits for 3 new 240v outlets in the shop (seldom used concurrently), one dual circuit for the new A/C condenser, a circuit for the furnace, and 3 spare slots.

Cheater! Get a new washer. I hear they're only 1/4hp now, and won't blow a 15a breaker.
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wrote:

This is what that curious-to-you phrase means: http://www.nh1.com/news/new-hampshire/storm-update-at-its-height-more-than-450k-lost-power-in-4th-largest-power-outage-in-nh-history The storm hit on Sunday night and the crews are only now completing the final restorations.
I ran the fridge on the UPS overnight, then since we hadn't lost power I checked the run time on the 6 year old batteries, which was still adequate. The solar panels I have now aren't enough to keep up with daily demand so I took advantage of Home Depot's sale on "100W" panels for $99 with free home delivery.
They are Grape Solar polycrystallines which get good enough reviews that lack technical details. I have the equipment to measure and record their output and will give them a good checkout, and perhaps buy an MPPT controller if it makes economic sense. Right now MPPTs cost about as much as another 100W panel without adding as much output from a small system. My DPS5015 switching regulator can be used to find and charge at the maximum power point but it won't track changes automatically.

I left the electric heat intact as an automatic backup for the wood heat, with new thermostats that can be set below 50F. Heat in the bathroom is very nice when I've let the house cool below 55F.

My old Dependable Care Maytags are easily modified to wash with water heated on the wood stove and poured in. I bypassed the water level control which allows these top loaders to wash with as little water as a front loader. Water isn't short here but heating it is expensive. The one I'm using now simply has an added Wash/Spin switch that reverses the start winding. All I had to do to change the wiring was rearrange the Fastons.
-jsw
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On Sun, 5 Nov 2017 08:09:56 -0500, "Jim Wilkins"

It's that Globular Swarming, uh, I meant Crimate Change, uh, I mean Tipping Point again. Leftist scientists say it'll be happening every 5 years from now on.

Not a bad price.

A PWM controller was included with the $1119 kit I got. 1080w of poly solar (6x 180w panels @ $170 ea.) I found a backup "MPPT" controller for $26, ($99 now http://tinyurl.com/yajajczf ) so I'll be testing the two against each other to see if the pseudo-MPPT gives any better output. These Taiwanese jobs were the next step up at <$300. http://tinyurl.com/ybvt6mme An Outback Flexmax 80 would be a nice one to grow into (with datalogger) but they cost $509. They're good for 150v solar arrays, so I could triple-up panels in series/parallel for less loss. Some day.

Interesting, but sort of a moot point without automation. Or is it? Finding the MPP of the system might be good for a boost, even without the tracking, but I haven't seen any studies on that. I'll look for some more articles on MPP to see.

Grok that. I disabled my shiny chrome heater, but put a $20 milkhouse heater in there to warm things up before showers. Heavenly.

Yeah, the older Kenmore and Maytags were bulletproof. My Magic Chef (? yeah, me, too) is a cheaped-out Maytag with plastic bucket. They had to replace the washer motor within 6 weeks. And the dryer thumped for the first 5 minutes due to soft rollers. I had them replace 'em although the tech said it wouldn't matter. Once he showed me the soft rubber rollers he removed, I understood. The type of rubber makes for thumps for the first few minutes, but a quieter dryer for the next 45.
I switched to a warm wash/cold rinse, which showed on my electric bill years ago to be the best way. With solar hot water and LED lighting, I may have $20/mo electric bills. The furnace has a variable speed DC fan motor for more savings. Carrier Infinity = no wood smoke = Love it.

One of my water heater elements will be solar soon, so that should effectively drop my electric bill by half. We'll see what 900w will do in a 20gal tank. I'll run solar all day. The other element is 3800w and I installed a timer (limited to 3hr/day) to bump it to 120F in the evening when necessary. Now to find sensors to collect data on it...
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On Sun, 05 Nov 2017 07:37:28 -0800, Larry Jaques

Nope. Conditions vary so much that a single snapshot of an MPP in time wouldn't be of much use. It appears that the MPPT controller changes the resistance of the circuit so it continues to output max power at all times, from 1 to 1000 times per second. (one of 84 million 400 thousand snapshots a day. ;)
https://www.teachengineering.org/lessons/view/cub_pveff_lesson03 (I know, k12 site, but it had the info I sought.)
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wrote:

I made that measurement on my HF 45W panels with a large rheostat and a DC Volt/Amp/Watt meter and found a range of several volts where the efficiency was at least 95% of the peak.
Batteries charge with Amps, not Watts. Any charging voltage above the 12.6V that the battery gives back is only a lost entry fee. The graph shows that the current continues to increase as the load (battery) pulls the panel voltage further below the Maximum Power Point.
The DPS5015 displays output Volts, Amps and Watts and with another wattmeter like the blue Aode in the input, the output can be adjusted for the maximum charging current reading, then you can compare Watts in and out to see efficiency.
-jsw
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