A vintage Singer Featherweight Motor vs. a New Alphasew Motor

Singer Featherweight sewing machines (221 and 222) are powered by an electric motor that is unique to the model. Unfortunately, this makes replacing a bad motor more difficult than it is for most other vintage machines. Although generic sewing motors are cheap and plentiful, they can’t easily be fitted to the Featherweight.

A Chinese company called Alphasew makes a reproduction Featherweight motor, but it typically costs more than a used, vintage motor. But is it any good? I came upon one of these motors on sale for $25, so I decided to find out. (And since this infromation isn’t available anywhere else on the internet, I figure it’s my job to put it here!)

The Singer motor sits on top of the Alphsew motor. The Singer's nameplate reads: "SINGER SEWING MOTOR / CAT. 3-120 / 110-120 VOLTS / 0.4 AMP. / 25-75 CYC. & D.C. / S. S. AU 61-18-1 / THE SINGER MFG. CO. / ELIZABETHPORT, N. J. / MADE IN U. S. A. / G678-4." The label on the Alphasew motor reads, "Alphasew / SEWING MOTOR / 110-120 VOLTS / 0.4 AMP / 25-75 CYCLES / A. C. & D. C."

I began by taking both motors apart to compare the design and construction.

Both motors are fairly close in design overall, but they are not exact clones. The casing of the Alphasew is not as well made as the Singer: the nameplate band around the motor doesn’t fit quite right and the mounting bracket doesn’t mate very precisely with the sewing machine. But inside, the Alphasew reveals a decent construction and a somewhat beefier design than the Singer. Here’s the Singer:

The Singer motor with its end cap removed.

And here’s a peek inside the Alphasew: The Alphasew motor with its endcap removed.

The most noticeable difference inside is that the Alphasew has thicker rotor and stator cores. Here is the rotor from the Singer. The core to the left is about 3/4 inch thick:

The rotor of the Singer motor.

And this is the rotor from the Alphasew. The rotor core is about 1 inch thick:

The rotor of the Alphasew motor, with the shim washers resting in the foreground.

The Alphasew has 24 commutator contacts, compared to the Singer’s 11. Notice the amount of carbon on the commutator, right out of the box. The motor shaft is also not polished very well:

A closeup of the commutator of the Alphasew motor. There is considerable carbon on the contacts and the rotor shaft demonstrates an uneven surface.

The stator coils are proportional to their respective rotor cores:

A closeup of the stator core of the Singer motor. A closeup of the stator core of the Alphasew motor.

The Alphasew has a crummy plastic coating on the lead wires (the insulation underneath is okay, though). I added a strain-relief knot and some heat-shrink tubing for good measure.

A closeup of the  Alphasew motor's wire leads, which have cracks on the outer insulation.

The Singer motor has spring-loaded felt pads that run through each bushing for lubrication. Petroleum jelly (Vaseline) should be used to grease these motors—nothing fancier is required:

A closeup of the Singer motor's bronze bushing. A felt grease wick pokes into the bushing throgh a hole.

Meanwhile, the Alphasew motor bushings don’t have holes for wicks—they’re made of a porous bronze that lets oil seep in from a wick around the outside the bushing. These Alphasew motors should be lubricated with straight oil such as 30-weight motor oil or 3-in-One SAE 20 Motor Oil (not the "regular" 3-in-One oil with the red label). They shouldn't be oiled with anything containing PTFE or Teflon, such as Tri-Flow:

A closeup of the Alphasew's bronze bushing.

The Alphasew brushes and brush caps (upper) are noticeably different from the Singer’s (lower). Neither are interchangeable: The carbon brushes and brush caps for the Singer and Alphasew motors rest on a sheet of notebook paper. They are subtly different in size and shape.

The pulleys are not interchangeable, either. The Alphasew motor has a shaft diameter of 6 mm and the Singer has a shaft diameter of 1/4″. The Alphasew pulley (right) is just a hair too small to fit on Singer motors: A closeup of the Singer and Alphasew motor pulleys.

By the way, as tempting as it may be, don’t use a screwdriver when replacing the brush caps... these only need to be finger tight. If they’re any tighter, they can break. A closeup of a motor brush cap on the Singer motor.

So how does the performance compare between the two motors? To find out, I installed the Alphasew on my 1947 Featherweight and checked it against my 1955 Featherweight with a stock motor (Singer catalog 3-120).

The Alphasew beat the Singer hands-down for power and speed. Particularly when the machine is stopped at “top dead center”—that is, when the needle is at the far end of its stroke—the Singer motor will strain and buzz when trying for a slow takeoff. By contrast, the Alphasew starts more readily and without apparent regard for the needle position. The Alphasew’s top speed is also faster and the motor is slightly quieter.

To quantify the torque difference, I placed a kitchen scale under the needle bar of each machine to measure the force. With the controller all the way down and the motor stalled, the Singer drew about 3/4 of an amp of current and the scale read just over 2 kg. The Alphasew drew about 1 amp of current and the scale read 4.5 kg.

However, anyone who thinks an Alphasew motor will give them more "piercing power" and let them stitch 7 layers of denim to 4 layers of shoe leather should probably think twice about what they want from a portable domestic machine... particularly one called a “Featherweight.” The Alphasew motor is just a nice, incremental upgrade in power. It’s probably the motor that Singer engineers would have outfitted these machines with originally if they could. In fact, Singer was aware that improvements were needed to the Featherweight at low speeds and they even invented a flywheel system to address it (US patent 2,282,071).

Overall, in spite of some problems with the fit and finish of the exterior, I found the Alphasew to have decent internals and good performance. Time will tell if the motor is durable, but the AC/DC motor design should be fairly bulletproof. I think the Alphasew motor is a worthwhile replacement—in fact, I’ve decided to keep it installed permanently.

Here are the measurements I took:

  Singer 3-120 Alphasew
Nameplate voltage (AC/DC) 110–120 110–120
Nameplate current 0.4  A 0.4  A
Stall current 0.71  A 1.05 A
DC resistance (at motor leads) ∼90 Ω ∼65 Ω
Free current* 292 mA 253 mA
Sewing current, full speed 0.60 A 0.63  A
Stator core thickness 13/16" 1-3/32″
Commutator ⌀ 1-1/32" 25/32" (20 mm)
Commutator contacts 11 24
Shaft ⌀ 1/4″ 6 mm
Rotor core thickness 11/16″ 62/64″ (25 mm)
Rotor shaft length, pulley end 1-1/8″ 1-1/8″
Brush height 13/64″ 4 mm
Brush width 13/64″ 5 mm
Brush length 1/2″ 11.5 mm
Spring length 1 3/16″ 19 mm
Brush cap ⌀ 5/16″ 10 mm
Needle bar force 2100 g 4540 g
Motor weight 26.7 oz 29.5 oz

* This is the current drawn by motor running at full speed under no load.

The needle bar force was measured with a kitchen scale placed under the needle bar, with the needle and presser foot removed and the motor stalled at full power.