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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. Gymnast

    PFAFF 1245 synchronizer bracket.

    Congratulations with your machine. Did you buy the machine for sale in Hvidovre? I just read some forum treads regading needle positioner. Most servo motors have problems in using a needle positioner, if you also use a speed reducer on the machine. It is not quite clear where the limits are. One reported, that with a gearing below 5 from servo motor shaft to handwheel shaft, it was possible to use a needle positioner.
  2. Gymnast

    Do you like this Speed Control?

    Thank you mikesc for helping to find what I search for. I searched for "servo motor" but got so many threads, that it became meaningless, and therefore I started a new thread. Now I found this 9 month old thread, that I might have continued. But I will look more into the matter. It seems to me, that most leatherworkers are satisfied with the servo motors they got, but a few like to see a wider speed range and the positioner to Work with the step Down gear. I have tried to make a case about using a better food pedal, but I do not think, I had any luck there
  3. Thank you Wiz, for explaining this to me and the historic background. I suppose you mean, that you still need a pretensioner with disks in order for the roller main tensioner to operate.
  4. Gymnast

    Do you like this Speed Control?

    I have seen the Enduro servo motor still using a slotted optical switch to provide input signal like all the references from 2012. It was also an Enduro servo motor, that was used for the the very popular "how to" video SWFLholsters made: Depending of what kind og sensor is used, and how the interface is made, it might be possible to make a retrofit solution by using an air pressure sensor instead. In this way it may be possible to use a pedal like me. When you look 10:30 into this video, you see the slotted optical switch, and 3 wires are leaving it for the motor control. If this is a standard component with a type number on it, I should like to know this type number.
  5. Thank you very much for explaining this to me. The video you found from Solar Leather do also have provide high quality instructions about the check spring.
  6. Gymnast

    Thread tension issues

    I think a Photo would help me to help you. You can get problems like this if the pressure on your presser foot is too low, so the fabric is lifted in parts of the sewing cycle. Did you check needle size or swap needle?
  7. Yes, it is some kind of illusion to me :). I think I watched 5 other videos on youtube regarding this subject now, and they all looks equal and as on your machine. They all seems to me like the thread do not go between the discs on the main top thread tensioner. So I hope I can learn something too. With the pretensioner Ryan in the video clearly indicates, that the thread must be pulled in between the discs. But he do not show the same regarding the main tensioner. Are the tension discs different on the main tensioner? Do the thread go around the discs near the outer perimeter of these discs? I normally see the thread commes in around the post, that may be only about 1/4" diameter, and I do not see this happen here.
  8. When I look at your Picture AND the video I refered to above, it seems to me that the thread is not put between the tension discs of the tensioner. I take that from the direction of the thread from the pretensioner. The thread rides on the top. It should be pulled in between these discs.
  9. I did also look at the youtube video I think the upper tension should be high enough to move the check spring at any time. So to me it means the upper thread tension is too low. Perhaps the lower thread tension is too low as well. Do you have any Means of measuring the thread tension? The Picture you have above, is that from before or after the stop on the check spring was changed? I would like the stop be lower than on the Picture to make Space for more movement of the check spring.
  10. I am not that expierienced here. But I like you to check the operation of your check spring. For my machine - if the check spring is not operating, the top thread may not be tight when the needle hit the fabric.
  11. Gymnast

    Do you like this Speed Control?

    I agree with dikman, that appart from the shown modifications back in 2012, changes to an existing servo motor are hard to do. There is a lot of complicated software inside a modern servo motor, which are involved in its performance and function. However there is industrial grade motor drives for short Circuit motors (short circuit motors are used for clutch motors on sewing machines). Perhaps some of these drives can be adapted. They are sold in big numbers for general use in industry. But I think this way is not that easy either. I think the best way is to look for the better performance when you search for a servo motor for sewing machines. From this video it seems, that some of the older type servo motors (with brushings) for sewing machines do not have any internal speed sensor. It may be a DC motor with a controlable DC voltage supply:
  12. Gymnast

    Do you like this Speed Control?

    Hi Kgg Thanks for your attention kgg. I did quite a lot of changes to my Singer 201k. It may not have been worth it, but I like its performance now. On my channal I made a small overview of the changes, and the changes relevant for speed are given from 3 min into this video: A video about the electronics is not made yet. It is like an electronic foot pedal for a domestic machines that includes feed back loop from a tacho generator and a pressure activated pedal. A very small DC motor is used as a tacho generator (speed sensor), and you can see it Pictures. Servo motors will normally have a similar feed back loop internally, but better posibilities to make fast changes in torque and have got more precise rotary encoders. However servo motors shall adapt to more kinds of machines than my setup. Furthermore the control pedal was previously discussed in this forum here:
  13. I have made a demonstration video on my simple machine. It do have got a simple universal motor, a speed reducer, and I made some electronics for it that make the system act as a servo motor. The speeds demonstrated in the video are from 8 stitches/min to 540 stitches/min - a factor 68. The response to load changes and small moves are shown as well: What is your controlable speed range of your sewing machine with servo motor? Can you do better or worse? I have seen some recent demonstrations on youtube of industrial sewing machines with servo motors. And I am not that impressed of the speed control I see. For most of them, I see them jump start to a quite high low speed, and I do not like that. I did see this video from 2012 showing a resonable good low speed control, but I am not sure about the max speed and speed range: Back in year 2012, several servo motor types had an issue, that they were hard to control. These issues were discussed in this forum, and I shall like to link to the four threads I just read about it: At that time a simple modification to some servo motors was introduced. More US suppliers of servo motors tried to make improvements and contacted their suppliers and manufacturers. I am however not sure, how much change to the designs that were later introduced. Electronic designers of servo motors may have limited knowledge of the needs of a sewing machine operator. Of cause an electronics designer can be incompetent aswell. The discussions here back then indicated, that many leatherworkers like to be able to sew very slow and also fast with the same set up. I think a factor 100 between lowest speed and highest controlable speed should be easy to make for servo motors. It could be from 45 RPM to 4500 RPM. However It seems to me, that most of the servo motors for sewing machines have a range with a factor about 30 only. The pedal construction can also be a limitation. However many leatherworkers were also happy with the motors they had. Others wrote, that they were not aware before the change, that they should like the better control they were able to get.
  14. Thanks for your reply It seems like the old findings from 2012 is not referenced any more. The funny thing is about the case in 2012 was, that it was a new man in the busines that started sewing and was unhappy with the disign. Most others would just accept the servo motor and "that you just need to pratice" to get better - its is not the machine that has a problem. I can confirm one called Yuma 550 watt, with another design shown here: It uses a magnet and a hall element magnetic field strength sensor. So the movement of the magnet changes the field at the hall sensor. However it cannot be a perfect system either. The earth magnetic field is about 50 micro Tesla, and it may somewhat disturb with the speed depending of the position in the World and direction of the table. However I do not know its performance regarding low speed. What I see is, that the lowest possible speed of the machines seems to be quite high (in my opinion). I would not be satisfied unless you could reach below 30 stitches/min. But it seems to me, that the speed jumps up from zero speed to a quite high low level speed. I know something about Electronics and Electric motors, and a well designed servo motor should have no problem in operating with a factor 100 in speed from lowest speed to maximum speed. And you should be able to control that with a good pedal as well. So I cannot figure out why this is not done with servo motors for sewing machines. This video from 2012 show this good low speed control with a modified servo motor: I noticed these two recent videos from 2018 with quite high low speed of about 120 stitches/min. It is a Ho Hsing G60 servo motor on Pfaff 1245: This other kind have the low speed limit of about 60 stitches/min with Sewpro 1100 NPFL: You have many more videos out there, they all seems to have this "to me strange" low speed limit. And many of them do only have a span of about a factor 5 from their controlable lowest speed to their max speed. Perhaps I should make a new thread here asking about this.
  15. I just noticed this topic, and I hope it is in order to revive this thread about slow speed control. I have noticed some recent youtube videos showing the speed control of servo motors. And I was not impressed by the slow speed control. Then I found these two 7 years old threads here dealing with the same problem and making a simple modification to some of the motors. Did the servo motors on market improve regarding slow speed control the past 7 years?