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About Gymnast

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    Applications for gymnastics. Repair of tarpaulin covers and with webbing. Rubber rope and terminations.

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    Sewing machines and ways to use them
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  1. When I you see max speed in the video, is it with the pedal pressed to max speed? Is the max speed limited by a setting? It seems to me, that the lowest speed is about 1 stitch per second and max speed is about 3 stitch per second.
  2. I have tried to look in more servo motor specifications, and I think it is hard to find what the lowest constant speed is. Normally you cannot find it or it is hidden very well. I guess it is because leatherworkers and other users seldom ask for this specification. Sometimes the machine got a ramp up function from start, but it do not help much. Perhaps most servo motors are designed for garment high speed machines, that do not need a bigger variation in speed. Normally the display shows the speed as Costabulary write. But I should think that 41 should mean 4100 RPM and 16 should mean 1600 RPM. But in general you do not know how these numbers translate to RPM. If the lowest speed is 1600 RPM, it is a very high low speed, and I newer heard of that before. Something could be wrong as reported in this video from 2012: https://youtu.be/X6CCxv3i4No This problem was discussed in more threads of this forum back 2012. This is one of them: I use my domestic sewing machine for many different jobs, and it have got a DIY speed control with a factor of about 68 between highest and lowest speed. Furthermore the construction of the pedal make a fast and easy control of speed: https://youtu.be/uTB8DnyYAlA I think it would be no problem for a servo motor manufacturer to make a similar speed control with very limited extra costs, if they got the demand for it.
  3. In another forum, a guy using this black bonded nylon thread ended at a similar solution to have the thread roll off the spool and for more sewing machines. But according to him, he got problems with hook catching the tread, if he let the thread come off the end of the spool. I have never heard thread twisting should be able to cause such problems. Another guy reported kinks on needle thread in the shuttle area. Up to now I mainly have read about problems with kinks in the thread pass before main tensioner. What kind of problems have you seen, that should be due to thread twisting?
  4. When you search google on the subject of UV-light and Corona, at lot is going on right now. Disinfection by UV-light is not new. I know UV-light has been used for disinfection of packing materials for milk and juice in the machines just before the liquids are filled in and the cartoon is packed. It has been like that for at least 20 years. This technology is already in use many other places, but of cause now with Covid-19 at lot more places are relevant for this technology. Yes, ventilation of rooms are also a matter of consern as well as how people may come and exit the room.
  5. Thank you very much for all the response. Just for the record. The problem in Denmark is quite low at the moment with 18 in hospital out of 5.8 mill citicens. Occationally we do have local areas with problems. Most surfaces we need to disinfect is covers of mats made of vinyl (PVC). Then we got some leather. I think most gymnastics clubs in Denmark will be using ordinary soap or general purpose cleaning products. This is one solution proposed by video(speaker in danish): https://www.facebook.com/PEredskaber/videos/3572701646131449/?__tn__=%2Cd%2CP-R&eid=ARC1T5L9r0qLl8aHqRsStBkEFrX2YncBTMW1itonleKpWKIpO7dGHoihAs_l_zUkGN9jktUaDZC7D586 We have some soft mats with a stretch knitted fabric (jersey) with viscose in it on the top of the mat. No solution has been found here and I think most will accept that we cannot clean them. Then we have to remove all common yoga mats. People need to have their own mat. The virus can go into the mats in ways, that we cannot clean or kill in an efficient way. Soap is effective on virus, but is is hard to use on hands without a sink. Therefore alcohol gel is used for hand disinfection only and it is used quite often with many dispensers around. We got no requirements on masks. This is not a political issue here. Scientists in Denmark do not find sufficient evidence for the use of masks, but some debate is going on among them. But it is demanded in some areas like public transport. Coaches may deside to use it, because they will touch and get close to many gymnasts. We also need to record who is there. UV-light could be a very interesting way to solve the problem. However we do know, that UV-light do affect life time of materials like PVC. We know, that we should not use these mats too much in the sun. But we need to know what the limits are, because it may not be any high dosis we need. This is a robot with UV-light moving around at its own (but of cause controlled) in a danish hospital (just for the picture): https://www.tv2fyn.dk/assens/frimaerkesamler-kan-jeg-bruge-uv-lys-til-desinficere-overflader . I saw a company selling UV-lamps saying, that everything was sold out now, so their might be delivery problems.
  6. In Denmark sports associations got demands for the comming season to disinfect common surfaces between each class of training. We have got some gymnastic equipment with some leather covers. I have been informed, that substances such as alcohol should be bad for leather. What do you suggest to use? Edit: This is one equipment:
  7. A normal sewing machine have a hard point in the sewing cycle, when the needle is on its way up and the eye is in the middle of the fabric. Then the friction to the thread is high from needle and fabric. At the same time the hook pulls down the thread, and the local thread tension to do this can be very high. With a needle too small it can cause the machine to stop or the thread to be damaged. I think this is taken into account, when you use tables from internet, that suggest needle sizes for threads. But this patcher is different, because the needle bar movement is controlled by a cam. The needle remains down with the needle eye below the fabric while the hook pulls down the thread. Therefore this machine might be able to handle a thicker thread for the same needle size that you normally will see for other machines. I link to this youtube video from a guy, that expects to use a V207 thread with a size 22 needle. https://youtu.be/Vv9eZbRR2z8
  8. I made a collection of nine videos from youtube on the topic of speed control. You may find it insteresting. https://www.youtube.com/playlist?list=PLhBGyDo4tov8XSL24b3eiAsGBhlPJA2SF You may just skip a video if you do not find it interesting. I have got a Bernina 910 domestic sewing machine, that I occationaly use for some garment. But I do not like the speed control, because when I press slowly down the pedal, I do not know when it will start sew, and suddently it starts. Some of my other machines makes some hum noise before it starts, and it is actually nice, because then you are prepared for when the sewing starts.
  9. A Singer 201 is compareable to a Singer 15 in performance. This is a video of a modified Singer 201 sewing leather: https://youtu.be/HIDuHjMRFWg As the video points out and show, the feed dogs leave marks on the surface of the leather. A combined feed machine will leave no or mush less visible marks on the leather surfaces. Furthermore this shown 201 have quite a few modifications, and may not take this kind of work for much time before being worn out. But it is possible for some limited projects and with limited finish quality. The modifications here include speed reducer, tension spring, presser foot with thread notch and advanced timing of feed. I do not think, that an unmodified Singer 15-91 will get you sufficient punching power and low speed performance, because the motor is quite weak and gearing is for high speed. For upholstery you can find workers that like the drop feed machines. But most upholstery workers use walking foot machines too. This is an example of this:
  10. Well when nobody else responded I just like to guess a little based on your information. I think in some way the stitch lever position was changed by the impact your machine had on to the road. The correct range was 0 mm to 6 mm width, before. Now it have in some way changed to -2 to 4 mm. I guess the dial with lever outside got some lock screw on to the shaft into the machine. Inside the machine I guess there might be some other kind of lever attached to this shaft with one or two lock screws. So I guess that one of these levers have got turned a bit on this shaft by the impact. You have got another lever or dial to fix the needle position from left to right. How much are you able to move the needle using this lever?
  11. Some sewers do light leatherwork on domestic machines or industrial machines for garment with dropfeed. I found this information about feed timing from JUKI on more of their industrial machines for garment: So they recommend an advance in feed timing in order to reduce variations in stitch length. A reason might be that the thread tension is applied and stitch is formed after the stroke of the feed dog finished. Therefore thread tension do not work against the feed.What is new to me is, that JUKI propose a delay in feed timing to increase stitch tightness. In this link it is reported, that you can reduce seam pucker by retarding feed timing:Link to book, Joining textilesI think it can be so, that with delayed feed timing, the feed is part of forming the stitch and makes some of the local thread tension to do so. Therefore less thread tension is needed from the tensioners. The result is that you can reduce seam pucker. But with heavier fabrics or more firm fabrics seam pucker will never be a problem and therefore it can be better to advance timing to improve feed dog traction with such fabrics.
  12. I just noticed this video from 2016 with a presser food designed with this thread notch. So I am lucky to not be the first one with this idea. This food seems to be on a high shank straight stitch drop foot machine: I just noticed, that this is a needle feed machines, so therefor the presser foot design is different. But the presser foot do have a remarkable long thread slid to the back near the hinge of the foot.
  13. I agree, that this is the main problem for a bottom feed machine compared to a walking foot machine. But I think, that it is not only the presser foot, that make the drag on top. Another reason for the drag on the top is the needle thread tension combined with the presser foot. A modified presser foot can reduce this part of the problem significantly as explained in the video: https://youtu.be/rBIulDuhDDs
  14. Yes, I agree with you, but it may be because I am an engineer too. Perhaps it just work for some of us. I did start this other thread about the subject in July: And made this little video about it: https://youtu.be/PAUJ1cVJEmA
  15. I noticed that the patcher sewing machines got a special movement of the needle bar compared to most other sewing machines. This is a video of the Chinese patcher sewing in some transparent fabric. Make note of the screw that fasten the needle in top of the picture: https://youtu.be/LOliY3NHg_A The needle height is controlled by a cam in the flywheel of the machine, and the hook position is controlled by another cam in the flywheel. The needle penetrates the fabric and goes to minimum height and a bit up again to form the loop of the upper thread for the hook to catch. Then the needle is hold down at same position a long time, while the hook moves forward and pulls down the thread. Then after this hook movement have finished the needle is lifted up. For normal sewing machines, the needle position is controlled by an eccentric on the main shaft and a connecting rod to the needle bar. Then the needle eye is lifted through the fabric and further up, while the hook pulls down the upper thread. This way causes a peak in thread tension near the hook, because the friction on the needle thread is high when the needle eye passes the fabric. This video explains this problem from 0:50 to 2:20 in the video: https://youtu.be/80WASgbKIX4 It is not only the Chinese Patcher, that moves the needle this way. The Singer 29, Adler 30-1 and some older sewing machines like the Singer 28 got a similar movement of the needle. I am sure, that in this way it is easier for the hook to pull down the thread, because the friction to the thread in the grove of the needle is limited. And therefore I guess that it may be possible to sew with smaller needles than normal with these patchers. Goto 10:50 in this video to see a similar movement for a Singer 29-4: https://youtu.be/aQLre-l5RkU Perhaps more leather sewing machines are made with this special needle bar movement, but I have not noticed that. Have you? I guess that you got some other disadvantages with this kind of cam controlled needle movement, and therefore most other machines are not made this way. I think one problem can be vibration at higher sewing speeds.
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