Gymnast

Yes, I think you always need to test on test pieces of real fabric or leather to adjust your tensions to the result you want. However, when you have used your machine for something else, and you go back to the same kind of work again, you can limit your amount of trials by using an instrument to set your tensions. I did read your refered thread about tensions and results and i just read it fast again. I think it covers many interesting subjects, and many issues of mostly top thread tension. I believe that the bobbin tension in most cases do not vary that much. However the top tension can vary a lot due to how heavy the fabric you are sewing and your aim at getting a ballanced stitch. The weight of the filled bobbin and bobbin case of my class 15 type is about 0.18 N. So a drop test ensures a force somewhat above this value - typically 0.25 N for me. The weight of a larger bobbin case and bobbin will of cause increase this value. When you try to measure the tension by holding a boobin case by hand and pull the thread of by the dynamometer, I can get rather big variations in figures. The force is dependent of the direction of your pull from the bobbin case and if you tuch the rolling bobbin. In my expierience, you get more dependable tension figures by measuring the thread tension of the bobbin thread comming up through the needle plate. For some machines it is hard to remove the bobbin case, and then you need to use this method anyway. I have not seen any significant difference in bobbin tension from a near empty bobbin and a near filled bobbin. I do not use bonded thread, and I get your point, that the coil memory in bonded thread have issues. I do not want to make this a physics class, so I will just say that the weight of 1 Pound on the earths surface is 4.45 Newton [N].

yes, if you put a switch on the wires to the motor Windings. With zero current to the stepper motor, I think most of them will provide zero torque. But it can be somewhat problematic for the electronics, when you switch on again. So perhaps the software do have a nicer way of doing it. I got a question too. With CNC machines with stepper motors, you normally can run into problems with a skipped steps. So they will have a way to go to a end stop electrical switch to reset the software and counter of steps in the sofware to make a right position. I suppose you can get similar problems with a sewing machine, when you want a needle positioner function. I think you need some other positioner on the sewing machine main shaft to reset the position counter in the software. Perhaps the positioner function shown in the video is just a command of a known number of steps forward.

I know that most operators of sewing machines newer use instruments to measure the thread tension. They have learned some way of feeling the right tension. But perhaps a few in this forum actually do measure their bobbin thread tension. I often change thread size in my machines, and I use a spring dynamometer to adjust the bobbin tension every time. I measure it direct from bobbin case or vertical up from the needle plate hole. You can get specialized instrumentation for sewing machines, but it will normally be more expensive than a simple spring dynamometer (Price $3) designed for use in schools. I have used google to search for information. For domestic sewing machines for garment, I find a recommandations to a tension of 0.2 - 0.5N (0.04 - 0.1 lbsF). In this leatherworker forum I did find these two links with a tiny amount of information: Here one person use 11 N or 2.5 lbsF for V138 thread, which in my opinion seems a very high tension. https://leatherworker.net/forum/topic/54237-sewing-machine-set-up-problems-at-witts-end/?tab=comments#comment-347489 And in this link 4.5 N or 1 lbsF for a presumable V277 thread: https://leatherworker.net/forum/topic/31327-boss-is-here/?tab=comments#comment-229798 I normally use 0.5 N or 0.1 lbsF for a V138 thread (Serafil 20). Occationally I increase it to 1.0 N when I like the thread to lay down better and look more nice. For a Serafil 40 or V69 thread I use 0.4 N.

I am glad to know, that you got the problem solved by changing the thread cone. I am not using the right machine for the job, and it made me investigate some details regarding thread twisting and thread tension. It was discussed about a half year in this forum, and it may help you to use all your thread and avoid similar problems:

I hope for understanding by reviving this 1 year old thread. I got a few questions to the answers. @myjtp asks for a zigzag that compliments a Consew 206rb. This machine should handle a V138 and perhaps a V207 thread size. However when I look at most of the suggested zigzag machines, they seem to max at a thread size of V92? So these zigzag machines do not compliment the Consew 206rb reagarding thread size. Do you agree? Except for the Sailrite Ultrafeed types, the machines use drop feed and no walking foot. I suppose this can cause problems with tracktion, if you got some larger size fabrics to be sewn. I have used some domestic zigzag machines - Bernina 910 and Singer 237 and I observed a big difference for heavier materials. Due to traction problems the fabric can have a tendency to cause pressure on the needle forward or backwards when the feed dog is below the needle plate. At the Berlina 910, the hook goes behind the needle, and therefore this machine becomes very senitive to this needle deflection. It can cause the hook to hit the needle, hit the thread or skip a stitch. For the Singer 237, the hook pass the needle to the side, and therefore it handles these problems much better. Or this is what I think is relevant - do you think the same? Unfortunately I noticed, that for most of the industrial zigzag machines named here, that do not have walking foot, they have the hook pass the needle behind as my Bernina 910. The Sailrite Ultrafeed type machines have a similar hook as the Singer 237. Perhaps someone rememeber, that I actually succeeded in making my Singer 237 sew with a Serafil 20 thread (V138). But it may not last long for heavy work like that. I think I may have used it with this kind of work for 20 hours. @Constabulary You name the Singer 457. I noticed a domestic type machine Singer 457 and an industrial type Singer 457g. I like you to clarify.

Thread tension is an often debated issue in this forum, so I guess you might find some answers by searching. I suggest, that you get a few dynamometers, because they helped me a lot with such problems. Many details can cause variations in thread tension. You may find these two references interesting:

Just for the record, some people show some creativity and use the possibilitiy of sewing plywood for their designs: https://materialdistrict.com/article/sewing-wood/ https://icd.uni-stuttgart.de/?p=16063

I think normally a Pfaff 1245 needs pressurized air to operate. For some it is a game changer. It might be possible to dismantle this part its accessory functions using air, but It may take some time to figure it out. I agree with Constabulary, that you will need to change to a servo motor.

I have tried to measure force and displacement of an ordinary foot pedal and the force controlled pedal I got. The measurement results are in the diagram below. For the force measurements, I used a digital kitchen weight. I have tried only a couple of industrial sewing machines, so i am not so sure about the normal pedal behavior of them, so I hope you can help me with your experience. I suppose you got a industrial sewing machine with a servo motor on it. When you press down the speed pedal with your foot, then first you need to apply some force before the pedal starts to move downwords. You need to overcome a spring pulling up the pedal to a stop. In the diagram you should look at the red dashed line, and for this pedal it starts to move with a pressure of 10 N or about 1 kg. When you press down further then the pedal moves downwords. At about 15 N force the machine starts to turn. In the diagram below it is when the pedal have moved about 3 mm down. When you press further down the force needed increase and the speed increase. At some position you reach max speed of the machine. This is at about 43 N force and 28 mm displacement on pedal. However it is possible to press the pedal further down, but the max speed is maintained. At some position the pedal go against a stop, and it do not move further even if you press harder with your foot. Apart from the numbers - is this text an accurate technical description on how your pedal work? Do you think the numbers for your machine is much different?

In the comments of this video, I asked Stephen Feldmeier regarding the slow speed behavior of the Sailrite Workhorse servo motor. He did not feel a vibration or "rough" behavior: https://youtu.be/SOyQtt3eDLw . I know that this is subjective evaluation. A speed reducer in general will cause a higher speed of the motor. A higher speed causes an inchreased frequency of the ripple torque and then the speed is better smoothed by the inertia of the motor.

Just by Google I see these two German websites. But I suppose, that you need them fast, Wiz. http://euroledershop.de/de/Maschinen/Nadeln/Nadeln-332-Llg/180-7 https://schein.de/en/maschinen_ansicht/068507-110

DC motors with brushes are actually much easier to control at low speeds with electronics and software. However I am not sure, that this kind of servomotors was ever made for sewing machines with an internal encoder to provide feed back information about speed to the electronics. To do this will make the production of the "mechanical" part of the motor more expensive, but the electronics and sofware less expensive. In some way, that is what i have done on my Singer 201, if you saw my video on that.

I know a bit about VF-drives for induction motors. When you need low speeds on such motors, then you need to implement more advanced control strategies in the software, to reduce ripple in torque. The answer here gives some indications: https://www.researchgate.net/post/What_is_the_lowest_possible_speed_that_can_be_practically_achievable_in_a_3-ph_induction_motor_through_VFD And this is a very technical document on the matter: http://www.how2power.com/pdf_view.php?url=/newsletters/1702/articles/H2PToday1702_design_TeledyneLeCroy_part13.pdf The strategies for a brushless DC motor is not that much different and they are also described. So in other words you can say, that it is possible to have a smooth behavior of the motor at low speed by adding development costs to make the software. Possibly they need to change settings in software depending of exsactly what kind of motortype the software is in control of. However this can also be an error of your servo motor, so I hope other users of the same kind of servo motor can provide you with their observations.

If it is a domestic sewing machine (low shank), then I recently discovered this big roller feet on the market: https://www.sewingpartsonline.com/leather-quilting-roller-foot-brother-blso-lrf.aspx

One other important diffence in material properties are creep or relaxation. With a long time load on the thread, the nylon thread will get longer and longer until it eventually breaks. This will not happen with a polyester thread. This may not be a bad thing for the nylon thread used for high load slings, because then the forces in uneven stiched parts will better be distributed to many threads of the seams. A good source of information on these materials are from rope users and manufacturers. One source can be found here: https://www.animatedknots.com/rope-materials#ScrollPoint

So you need to find the right guy able to make a resonable cloth timing belt. That is the difficult part.

Hi Chrisash. I think this thread is about sewing plywood, and we should not make it a vintage sewing machine motor thread or speed reducer thread. I will send you a pm. If some other people are interested in information about that, then please make a new thread about that, and I shall make my comments.

No. It is a stronger motor, but not the strongest motor you can get as replacement for this kind of vintage machines. Please be aware, that nominal input electrical power and input nominal current to the motor is one part of the issue. What matters is output mechanical shaft power and output torque of the motor. The effectiveness of these kind of motors vary a lot. My original Singer 201k motor was quite weak and my replacement motor got about the double max shaft torque and double the speed. The sewing machine was build for quite high human power using threadle and hand crank and a bigger fly wheel to make the torque even higher at the hard spots.

I tried to figure out the category of the Finnish Plywood, that I used. It is made of Baltic Birch in all layers, and it is considered a Hardwood. Source of information: https://www.andersonplywood.com/hardwood-plywood/ https://www.wood-database.com/baltic-birch/

Thank you for correcting me Wiz - I am sorry that I got that wrong. I was a bit suppriced in my test, that I got almost no splinter at the bottom. I suppose, that the small hole in my needle plate helps to limit that problem. An important question for this work is what size of thread is needed. I agree with RockyAussie, that you will save a lot of time by asking for help in an upholstery shop.

You can look at some details on my channel: https://www.youtube.com/channel/UCtdxanz878434pFr2dMhwXw An overview of the quite many changes are given in this video: https://youtu.be/_7ML5U_I6DU Many skilled people have warned against using a machine like this to heavy work. But up to now I have done it for about 5 years and about 100 hours of work in all. It is still working. And this kind of machines are quite cheap second hand in my country. I got one reserve machine on stock.

I like to link to one of the previous threads on in this forum on the subject: https://leatherworker.net/forum/topic/66962-sewing-through-leather-and-plywood/?tab=comments#comment-436004 I notice that even Wiz back then wrote a comment, that he once sew plywood with a singer 15-91 with a 110/18 needle and V69 thread. Well this got me a bit provoked, and now I tried sewing plywood on my Singer 201 domestic machine for sewing shirts. And I admit, that it is modified, and this is not for general long time use. This sewing is with a 140/22 regular needle, V138 polyester thread and 4 mm Finnish Plywood. This is how it looks:

Thank you Pterytus for exploring the NPS of the Zhejiang sensor module and the reference above. I was not aware, that NPS was made that simple. If you have got a high speed machine, then I suppose that the machine will be unable to stop from high speed within a few degrees of the main shaft, because you got too much moment of inertia. So first the electronics need to slow down the motor to a low speed, and then it need to stop when the next signal from the NPS hall element arrive. I am a little suppriced by the fact, that the upper stop and lower stop of the needle are made with a distance of 180 degrees. I think I read somewhere, that you like to have the lower stop just a bit later than the hook have catched the upper thread, so the needle eye levels with the needle plate surface in upwards direction. I supposed that the upper stop was at max height of needle, but it may be that it is at max height of the take-up lever and then it may be close to 180 degrees. Anyway, I wish that you one day will get a speed control like me with a pedal force sensor. My show off is here: https://leatherworker.net/forum/topic/86489-do-you-like-this-speed-control/

If you make a search by Google, you will be able to find technical research done on the matter, with pull tests of seam strength for different cases. With leather, you will normally cut holes in it to make way for the needle and thread. Therefore a short stitch length causes the leather to get weaker at the seam. In this case the seam strength will be determined of the remaining strength of the leather. On the other hand when you have a long stitch lenght, the strength of the thread may deside how the strength of the seam will be. Woven fabric will normally not be weakened much by the needle, because the fibres in the fabric is just pushed a Little to the side and remains intact. Therefore a short stich length do not cause quite the same problems for strengt. In most cases I should think, that the stich length is desided by the looks, and how the manufacturer feels about it, and from some experience.

Perhaps you can lent one from your local auto repair shop, or they may help you. A puller is a standard Tool for them.