GerryR

I'm a little late to the party, but here is my $.02 If everything runs freely, the casting can be brazed, or if just a hairline crack, silver soldered; I wouldn't weld it.

I don't know much about clutch motors but have assumed they run at full speed and that you "feather" the clutch to regulate the output(??). If that is the case, then running it with a VFD is not a problem. As stated above, you need to worry about low RPM because of the cooling. Many "inverter rated" motors are spec'd at 10-90 Hz. I have run many VFD's on fractional to 100+ Hp motors (factory automation). I presently have one on an old Boyer-Shultz 3 ph. surface grinder in my shop (running full speed) that has been running for over 20 years, and I have a VFD running as my speed controller on my leather sewing machine; the sewing machine has an inverter-rated gear motor with a 5:1 reducer, so motor low-speed control is not a problem. The point is you can use some form of reducer to raise the low-end motor RPM to keep it cooler. I have recommended VFD's as optional speed controllers for sewing machines with clutch motors, lock the clutch on and use the VFD with a TIG welder footpedal to control the speed. Many Tig welder footpedals have a built-in potentiometer for regulating output power which can be used to control the VFD output frequency. Just some thoughts that might help if you run into problems. (By the way, I'm using a unit similar to what you purchased (in my case 220VAC 1ph. in to 220VAC 3ph. out) and it works perfectly!)

First Stitches! (Still doing some "tweeking," but looks promising.) These are a single layer of 8 oz. veg tan and a double layer.

Well, because I didn't have an easy way to make a new hand / cam wheel to get the added needle stroke that I needed, a machine mod was going to be needed. I had a second machine and chose to modify it to be sure the mods would work before messing with my good machine. To get the added needle stroke, I moved the pivot point of the arm by 0.75 inches toward the hand wheel. I had to machine the frame in order to relocate the pivot point, but it worked out pretty well. I have one small issue that I will address Monday and that will finish it. It is no longer a true "patcher" but after running it for awhile with different threads I will swap the parts over to my good machine which is motorized. Here's a few pictures of what I ended up with.

I use an AC variable frequency drive (VFD) with a 3-phase 5:1 speed reducer gear motor. The controller converts single-phase house current to the needed 3-phase for the motor. The VFD gives the needed speed control. This is another option that seems to be overlooked. The controllers can be bought for less than $100.00 that will handle up to a 1 HP motor. Many of the older industrial clutch motors were three phase, so it would be easy to lock the cluch on and connect to a VFD to get very good speed control. Just another option.

I've had a little more time on my hands than usual and decided to mod a Chinese Patcher to handle M-style bobbins to get the added thread capacity. One of the goals was/is "no modifications to the existing machine" so I can get back to the original patcher just by swapping parts. Well, I got everything done "except" I need to either make a different swapable hand / cam wheel or make a different needle bar connection to get the additional needle down stroke, about 0.3". The cam for the bobbin rotation works as is, as the angles of motion are proportional. I don't know if in the end I will get it all working, but at least I can easily put it back to original. I think these patchers get a bad wrap, but mine has worked flawlessly. It's definitely a educational project. Comments and suggestions are welcomed.

@CowboyBob I had built a bobbin winder machine using a Rapala digital fishing line counter (see picture) and just received some M-bobbins, and though I haven't yet wound all the above size threads, I did wind sizes 138 and 207. I got 42 feet of 138 and 32 feet of 207 on the bobbins. They are probably not wound as tight or as uniform as the "store bought" bobbins but the discrepancy of 69 ft to 42 feet seems quite a lot. When I have the time I will redo the 138 and 207 and run some 69 and 92 thread. Just thought you would like to know. I will follow uo in a few days.

Thank you Bob! It looks like there is about a 10 yd difference between sizes so maybe I can assume 13 yds. for 207 until I can verify it.

I would like to know the capacity of M-style bobbins for #69, 92, 138 and 207 thread, I looked up for prewound bobbins for #138 thread and they stated 36 yds. but said the same for 92 thread, which didn't sound right to me. (They were probably just loading a fixed amount on the bobbins, not filling to capacity.) I would like to know the full capacity, +/-, of the M bobbins for the size threads stated. Can anybody help? Thanks.

Sold!

Here is a service manual and parts list for the 29K71,72, 73. I don't know the differences compared to the 29K70. Hope it helps. Singer 29k71-2 Patcher.pdf

I have a 4:1 reducer on my machine, so "slow" is not a problem. (I also know that there is a mod to give more range on the speed control to enhance low speed operation. I would use a higher ratio speed reducer so that the motor can run at a higher speed and give you the lower speed that you require. This is better for the motor. Also, just for curiosity, I just finished checking to see how/if it would run on 120VAC, and it ran perfectly, full torque, full range of speed, etc. I assume the internal supply is universal and can handle all the way to 220VAC and that they change the label to suit the market. So, you can run it on 220 in the shop and have a small adapter cable to run it on 120 when in the field.

The Enduro drives work pretty well. The smaller unit, SM645B-2P is for sale on Ebay (https://www.ebay.com/itm/165684311695). I have used 2 0f these units, and except for the positioner control have been very satisfied. They make a larger unit, SM1050-2PF. The positioner control requires a simple modification to get it to operat properly. I don't know about th SM1050, but there are several people who have commented that the SM645 unit works just as well on 120VAC as it does on 220AC; I haven't tried it and run mine on 220 VAC. These might be other options and are very inexpensive.

The Pfaff 1200 series (1221, 1222, etc.) are domestic machines but are very rugged machines, and some of them have an upper walking foot (I believe it is called the "Matchmaker Foot") that can be engaged or disengaged. If you look on Youtube, there are videos of people using these machines for auto upholstery. I have no experience with Alcantara car upholstery so don't know if these machines are suitable for it, but it may give you another option. Brubaker's in Penn. (https://brubakerssewing.com/) would be someone to talk to as they are a Pfaff dealer.

Very nicely done. I'll have to rethink my approach to maybe simplify it somewhat. Thanks for the pictures!