Constabulary

I don´t think you can get the OEM wheels anymore (well maybe... you never know). If I were you I would probably take a wheel from a different bobbin winder then wrap a piece of leather or PU flat belt around it and adapt it to the spindle. Spindle is present I guess? Other than that I would buy a table mount bobbin winder https://www.ebay.com/itm/143422223667 But it may need some modification as well.

30-10 is the newer version of the 30-1. Technically there is no big difference. Both are small bobbin patcher machines with the same stitch length and foot lift. Spare parts are expensive.

not all new machines are necessarily clones of "old / big name" manufacturers.

Or the needle size is too small so the needle hole is not big enough for the bottom an top thread and the thread knot cannot be pulled into the material. Try a bigger needle or smaller size the bottom thread.

Thats right. The original question was for a 111w.

PE means Polyester I`d say and 35 could be thread size TEX 35

Maybe the discs with the stitch length numbers has slipped. I´m not in front of your machine so I only can guess. I would try this. Open the cover plate on the top. Loosen the set screw of the stitch length dial. Push the button in the flatbed and turn the hand wheel towards you until you feel resistance. Then the longest stitch length dialed in. Then rotate the stitch length dial until you see the 5 in the window in the casting and tighten the set screw again.

@kidbeey I just recalled this thread here. Maybe this is interesting for you. Contact him by sending a PM cause he only made 2 post here.

check what diameter the bobbins have that come with the machine, small ones are approx 16.5mm the large ones are approx 20mm in diameter.

Your stitch length adjuster is installed upside down. The arrow has to point upward. Also make sure the gib is instilled correctly.

BTW - hope you are aware that is is not a heavy duty leather sewing machine. It was used for sewing garments and maybe some lightweight leather. What leather thickness (all layers together) do you want to sew and with what thread size? Those who think it is a heavy duty machine usually come form domestic sewing machines and think because of size and weight it has to be a "Hevay Duty" machine.

There were pre wound bobbins for barrel hook machines? Can you post some pictures please? Did the machine come without bobbin winder? That surprises me. This one should work: https://www.ebay.com/itm/143422221569

If the needle for your machine is 16x231 then you need a round shank needle. The needle system 16 (as from the Singer 16) is also called System 34 or 287 or 1738. Here you can find different leather needles for the mentioned needle system: https://www.thethreadexchange.com/miva/merchant.mvc?Screen=CTGY&Category_Code=NDL-34

I agree with nylonRigging. Pfaffs are excellent machines - no doubt. But finding gauge sets for different needle distances is a pain. When you are looking for a double needle machine I would look for machines based on Singer, like JUKI, SEIKO, Mitsubishi, Brother (they often share the same gauge sets) or the Singer 212 or 112 it self. On the other hand if the machine has the needle distance you need and you are sure you will need no other then go for it. My double needle choice was the Singer 212G141. To give you an idea of which machines share the same "Singer Type" needle feed gauge set check the description here: https://www.ebay.com/itm/153439679127

True. As Kafka said: Better to have, and not need, than to need, and not have. But this one actually goes on to a new setup.

I finally used the above shown pats for making a box type speed reducer. I have used 15mm coated plywood. It still needs some work.

Patcher machines can become quite handy for repair work or certain sewing operations. if it is cheap and it works and you have enough space for it - why not. My 29K71 does not see much work but I love it and I´ll keep it.

It basically is a shoe and boot repair machine and not designed for really heavy work / heavy thread. 138 pretty much is the max. is can handle. The 29-4 is probably 100 years old and has some (a few) parts in common with the later 29K models. Some parts remained the same bust most of the important wear parts are obsolete. You may find some but they are hard to find nowadays. Its a different story for the later 29K models like 29K71 - the later models are still made in China / far east so parts are usually not a big problem. Servo motor is possible but you have to figure how and where to install it. You may also need a counter spring cause the 29K´s have a heavy cast iron foot pedal. The Adler 30 machines (a similar patcher model but made by Adler in Germany) had optional motor brackets for the treadle stand. I can post picture of one later. Lots of information on the 29 / 29K Singers when you do a google forum search: https://www.google.com/search?client=firefox-b-d&q=singer+29+site%3Aleatherworker.net%2Fforum

I barely need one but I´m using the one fredk shows as well. They are cheap on ebay like 6 bucks or so. Well they all come from China anyway. I have polished / sharpened the blades with jewelers rouge on some scrap leather and I´m actually very pleased with it. F.i. https://www.ebay.de/itm/364005525549

Not sure what the subclass 11 includes but the major difference usually is with what accessories the machine once left the plant. What I can tell form this single picture is that it is a drop feed machine w/o reverse, it has an outdated clutch motor (you will not like it cause it is very fast and most likely not easy to control). This is the 2nd model of the Singer 51w. It has a plain presser foot instead of a roller foot. Some parts are still available but not too many. IMO the 2 plats on the machine bed look kinda odd and I don´t think they belong to this machine. Price wise i think it is too expensive for what it can do but on the other hand post bed machines are harder to find than others. If you buy it make sure the stitch length adjuster is working and nothing it broken on it. Also make sure the timing belt is in very good condition cause AFAIK they are no longer available. The 51w when it came from the factory was set up for a nowadays rather odd needle system 128x3 / 128x4 (or similar) but you can convert the needle bar for using a more common needle like 135x16 or similar. See this link: https://leatherworker.net/forum/topic/96574-singer-51w56-needle-bar-conversion/ I have the 1st model of the 51w and I like it very much but to be honest I´m barely using it. I did a needle bar conversion and a presser foot bar conversion as well but that was cause it still was the 1st model based on a Wheeler & Wilson machine. If you are interested: https://leatherworker.net/forum/topic/86292-singer-51w-sv-2-post-bed-machine-restoration/ Maybe you can give us an idea of what you want to sew so we can try to suggest some other machines. If you need more machine details of the 51w class you can download some 51w manual here:

That is what I was thinking too when I was new to sewing machines. Not that does not work! But you can turn around the product you sew and make the back stitch that way.

looks like 992 00 680 0 - ROLLE (roller) Check with you local dealer or this dealer in Germany. He has a good reputation. https://liersch.com/online-shop/ersatzteile/duerkopp-adler/10222486-rolle-5-49x9-82x7-1-0992-006800 Seems not to be super expensive. If DIY is an option the measures are in the above listing.

Take of the V-Belt and try turning it by hand. Or push down the foot pedal cause the clutch motor has a brake .... just guessing w/o having seen the machine setup.

Just from the picture... Machine has no reverse, not necessary but reverse is a bit more comfortable. Good thing is it already has a speed reducer installed which slows down the sewing speed and adds torque. The oil drip pan underneath the table is missing. It has an "old school" clutch motor. Though it has a speed reducer already the clutch motor may be a little hard to control. So a new servo motor is probably what you want Just test it maybe the clutch motor setup works for you.... See attached file it will gives you some more information 211G165_166_265_266.pdf

I´m still not sure what you mean. There is no need to remove more parts from the arm and I´m sure it is not possible and not even necessary for timing. When you have the hook installed (guessing you have one incl. the parts that hold the hook in place) and the needle plate is not installed (guessing you have one) you have a clear view on the hook and hook tip and the needle sooo....