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Kitcarlson

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Most sewing machines make one stitch per hand wheel revolution. Observing needle bar movement with hand wheel rotation, verifies stitches per revolution.

Measuring RPM, provides a means of evaluating machine performance. Listening to a machine, feeling vibrations may be misleading in estimating speed. Measuring power in operation, with maximum controller speed, provides motor output estimation.

The ability to measure RPM of hand wheel and motor provides a method for determination of belt slip.

Pulley sizes of hand wheel and motor, determine drive ratio. RPM ratio follows drive ratio, and should stay nearly constant under load conditions. Ratio can be found by measuring circumferences and dividing hand wheel by motor pulley. An alternative method is mark each and rotate hand, counting turns plus fraction of turns of motor pulley. A Singer 99 has a ratio of slightly more than 3-1. Correct belt adjustment, is just tight enough not to slip. Too tight of belt, stresses motor bearings, and may create enough friction to activate main shaft when hand wheel stop is set for bobbin winding.

Hand wheel speed is easily measured with a DT-2234C digital tachometer.
20191215_084100.jpg 
They are available for about $10 shipped. A reflective adhesive target, marks a spot to trigger tachometer measurements.
20191215_083836.jpg 
Target strips are provided, along with a zipper carry pouch. Since most motor pulleys are shiny, pasting black paper disk with reflective target should work as target. On open spoke hand wheels, blue painters tape with target should work as target. Test button is pressed while pointing tachometer at target, a red LED provides visual feedback indication of aim. LCD display indicates RPM, and updates at a rate of 0.8s per reading. RPM measurement is accurate, viewed on 5 digit display, (+/- 0.05% +1 digit).

 

A Meterk MK34 power meter was also purchased for about $20.
20191215_084035.jpg 
It measures real power consumption of sewing machine plugged into outlet. The power meter also measures current, line voltage, and power factor. Power in a DC circuit is the product of voltage times current. In AC circuit, the voltage and current “wave forms”, are multiplied to determine real power. Sewing machine motors are inductive devices. When an inductor is energized, current is 90 degrees out of phase with voltage, there is current and voltage, but real power is near zero. A loaded motor draws real power, yet has reactive component for charging magnetic circuit. Measuring only current, results in somewhat meaningless information. A power meter makes measurements, not possible with typical multi-meter.

 Power is a measurement of work, and power includes losses. Small motors are inefficient, perhaps around 30-50%, but relative measurements are still useful. Power measurement can indicate if motor achieves desired output. An estimate of motor output is rated current, times voltage. For a 0.6A motor at 120V about 72W.

 Motor controls are typically series resistors, serving to reduce voltage and current seen by motor. There is power loss in resistance controller. The power loss is current squared times resistance, or voltage at resistor times current. To eliminate controller loss, an electronic controller was used in tests below. An electronic controller energizes motor for portions of AC wave form, when not energized the loss is near zero, and when fully energized, controller loss is low too.

 Singer 201 potted motor and LED light:

Machine mounted in Singer 48 cabinet, smooth operation over complete operating range. Quilt piecing of 2 cotton layers. Machine quickly accelerated is max speed runs. Light on during tests. Potted motor cover waas removed to count motor rotation, Singer 201 has a 5-1 ratio.

 LED lamp with 104 elements 2W, in comparison a standard incandescent ~15W. LED has significantly greater lumens.

 Measurements w/electronic control:

70 RPM, 20W as slow as controller would allow

300 RPM 34W

600 RPM 57W

1100 RPM 80W, full speed

 Measurements w/Singer carbon pile control:

note: controller losses in values below

Slow speed not possible

288 RPM 58W

580 RPM 69W

1100 RPM 80W, full speed

 Future Study:

I would like to try several machines to see if results vary, with same model, suggesting need for improvement on lagging machines. My wife tells me when 201’s have a problem. The most common issue is stiff grease in gears. It seems that fibered automotive type bearing is the culprit. Removing old grease and replacing with Vaseline or Tri-Flow grease works wonders. I have heard just SM oil works too.

 I hope to do more tests, add to post, as time and location permits. The plan is to use one motor with electronic controller and move it to many machines. The single motor will let me test things like machine mechanical resistances for belted machines. I will compare to Singer 115,127, 99, 201K.

I will also check Singer 101, 15-91, 201 with potted motors.

 



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Dave in middle TN
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ke6cvh

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Reply with quote  #2 
Hello group,

  What about taking a thick piece of paper and running it through the machine.  Have a marked "starting line" and a marked "finished line then time it, count the number of holes in the paper, and use calculations for the number of revolutions per needle stroke?  Not as accurate but a possible alternative if one doesn't have the test equipment.

Best regards,
Mike
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Kitcarlson

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Reply with quote  #3 
Mike,

That works too.  I had tach, when developing my automotive engine ECUs, and distributor reference sensors.  Decided to try on machines.  Decades ago I developed electronic industrial 3 phase power metering devices. Trying to apply past interests to new hobby, perhaps in excess.

Dave

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Dave in middle TN
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ke6cvh

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Reply with quote  #4 
Hi Dave,

  Was just trying to point out a simple but less accurate test for those who might want to try it at home and not having the equipment for high accuracy.  I have loads of test equipment here also...no tach anymore [frown]  Actually,  I almost googled and looked at how much one of those cost and might do it later.  If I had one it'd be the choice for me also.  Different subject but paper is a way to test any machine that has a puller.  According to manuals one runs a paper through it and if the hole is elongated the puller is out of adjustment.  Paper can also be a really low cost way to test machines.  Sometimes I like to brag and show a piece of TP/toilet paper being sewn on a domestic.  For example our White 77MG does a really fine job of it and with no more adjustments goes straight to denim without a hitch.  The data you documented is a big help.  Many don't realize how inefficient the universal motors are but of course the advantage being low cost and high RPM for the size.  

Best regards,
Mike
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Kitcarlson

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Reply with quote  #5 
Mike,

Is "puller" a feed dog, walking foot?

I have been thinking about brushless dc motors. Have hand drill with one. Get at least 2 times run time compared to brush motor. Looked to find one that might work, and hide in Singer Bakelite case, for portable use with tool battery pack.
No luck finding one yet,

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Dave in middle TN
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ke6cvh

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Reply with quote  #6 
Hi Dave,

  A puller is a set of wheels, some with teeth and some just nylon cylinders, found on some industrials.  Two of our three waist band machines have them.  Our specialized hemmer has one, we have a gartering machine with one, and our feed off the arm felled seam machines have them.  Not seen on domestics but I had to throw the comment into the mix.  I've been looking for a solution for quite some time for replacing the universal motors.  What seems interesting to me is the brushless electric skate board motors with the urethane wheel.  I bet it'd work as a friction drive.  Our solar is a 24v system here as I already had one shipped and just added on so never had the chance to go with a 48v system.  These are small and take 24-36v input.  Best regards, Mike
https://www.ebay.com/itm/DIY-electric-skateboard-wheel-W-brushless-Sensored-5065-motor-Parts-24V-36V-80KV/362809028171?_trkparms=ispr%3D1&hash=item54791a6e4b:g:Vs0AAOSwvmRa4t6V&enc=AQAEAAACYBPxNw%2BVj6nta7CKEs3N0qW9ntAJIc%2BZcY1I6E%2FldoMNSRHu7N6UHbAd5o125JBCSGhixIVQTUr5q4BfZO8JUoWwA6PpGtwss%2FCHQiwpSu4O0RCetSptRmKOLsZWUUTQnvE3PLqIbL%2BGgRNG7UZ8pBWl8Z%2FG96I7IT9wSPNz6zXORligJvO%2BdgOGWNJSyk8Z9Wf2%2Fr8QJctAGKEj%2FZJgyJ4jCDTLio9Ox9EF29jB0QBNnIS5m9CI1PwRuz%2FK3Ia%2FhZO%2BJ7DpeP1%2BPUwsqwqoMnGAI%2FNkY%2Fjn5zoGun%2BtEKOglcz5zqu2M9UHICcIzDptTaoS9tqxazrZLN%2F2gtqXFwyyZKR4HfyqCgwM1g7m8boDTJOMEFbE5Ohcb8eOx9oQCk19Iu8Dh7MA5QhGtz9%2FjPfpFjo5pDIO8xuAoMFsATGl%2Bl%2BtPV0BWOKSNksJvugOAQUJwllGnakHcT0IU5Zcfth1sne%2B9PTF4Yu1O%2BolhCZt0FTxyM22iQf48O7iHaminzpv3d2C77Bd6AC7w05YvY0B5FUiIXXqB1pUYFeQRyopfSajyp%2Fl%2FALEHITjKPhHGNinWSY3h5s2WuHFAyIX2J%2BO8z3vKPFlwrSVjbLL0XckPqZwsbR88%2Fo%2BnpcvLBToCB8aWc%2Fl7GaiATC15G86tqeOFMEm1fvqxTjynpxOWpwMMki1wQ3taDE8muN2uY0PRAOiygtCUv1te9ZrpWVN54fjYk8p%2FUbGVQY48qJChMD5YPrva0uI51ACgGWv37mhD4ouo7QkBggRJj28pIueyI2UrD2McpxJhv0BFgfuVr3V&checksum=3628090281715c2c91b2eaf04b108d217f73dcdccd18&enc=AQAEAAACYBPxNw%2BVj6nta7CKEs3N0qW9ntAJIc%2BZcY1I6E%2FldoMNSRHu7N6UHbAd5o125JBCSGhixIVQTUr5q4BfZO8JUoWwA6PpGtwss%2FCHQiwpSu4O0RCetSptRmKOLsZWUUTQnvE3PLqIbL%2BGgRNG7UZ8pBWl8Z%2FG96I7IT9wSPNz6zXORligJvO%2BdgOGWNJSyk8Z9Wf2%2Fr8QJctAGKEj%2FZJgyJ4jCDTLio9Ox9EF29jB0QBNnIS5m9CI1PwRuz%2FK3Ia%2FhZO%2BJ7DpeP1%2BPUwsqwqoMnGAI%2FNkY%2Fjn5zoGun%2BtEKOglcz5zqu2M9UHICcIzDptTaoS9tqxazrZLN%2F2gtqXFwyyZKR4HfyqCgwM1g7m8boDTJOMEFbE5Ohcb8eOx9oQCk19Iu8Dh7MA5QhGtz9%2FjPfpFjo5pDIO8xuAoMFsATGl%2Bl%2BtPV0BWOKSNksJvugOAQUJwllGnakHcT0IU5Zcfth1sne%2B9PTF4Yu1O%2BolhCZt0FTxyM22iQf48O7iHaminzpv3d2C77Bd6AC7w05YvY0B5FUiIXXqB1pUYFeQRyopfSajyp%2Fl%2FALEHITjKPhHGNinWSY3h5s2WuHFAyIX2J%2BO8z3vKPFlwrSVjbLL0XckPqZwsbR88%2Fo%2BnpcvLBToCB8aWc%2Fl7GaiATC15G86tqeOFMEm1fvqxTjynpxOWpwMMki1wQ3taDE8muN2uY0PRAOiygtCUv1te9ZrpWVN54fjYk8p%2FUbGVQY48qJChMD5YPrva0uI51ACgGWv37mhD4ouo7QkBggRJj28pIueyI2UrD2McpxJhv0BFgfuVr3V&checksum=3628090281715c2c91b2eaf04b108d217f73dcdccd18
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JonesHand52

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Reply with quote  #7 
Mike, et al -

In reference to using paper to test stitching quality, I always use a piece of folded paper towel when test running a machine, especially a new arrival that has not been tension adjusted. It's a heck of a lot easier to tear apart a paper towel to get to the thread jam and unblock it than it is to try to remove woven cloth. 

- Bruce
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