Thread tension and twisting

[dikman]

Rocky's idea of a thread tensioner could work, something with just enough tension applied to keep any slack from occurring as the coils come off the spool.

[Gymnast]

I have noticed, that many of the heavier sewing machines have got a wheel type tensioner as main tensioner and one or more pretensioners of disc type. I suppose the wheel type tensioner have got an advantage by not creating much twisting of the thread as the disc type do. The higher thread tension a heavy machine needs should cause more twisting problems, if a dics type tensioner was used as main tensioner.

Do you know of heavy sewing machines, that uses disc tensioners as main tensioner?

What is the correct name for this wheel tensioner type? I "borrowed" this picture from @constabulary of a Singer 45k tensioner. I hope it is OK for me to use it.

I plan to make a revision of the video in the start with the extra information I got here from you. If you have got a picture of a more modern Wheel tensioner, I would love to see it and use it.

[jimi]

Hello Gymnast, Here is a link for a Singer industrial machine that was i think the last of the industrial type leather machines Singer made. It is a modern version of the Singer 45k class machines and has a list of all the similar types of machine in its class. The Adler 4 and 5, 104, 105, 205 were also similar to the 45k, the later being the transition between the 45k and 45b. Seiko and a few others from japan also made similar machines but i cannot remember their names

http://www.industrialsewmachine.com/webdoc1/singer/45b.htm

 The tensioner in the picture is normally referred to as the lower tension assembly, in the parts book it just says "tension" complete and the parts numbers it consists of. If this is any help to you, you go around this wheel 1  1/2 times. you can get a lot of info here on these machines, here is the manual if you need to look at it. 

 

Edited January 5, 2020 by jimi

[Wizcrafts]

It is my theory that the use of roller tensioners was directly related to the common use of linen thread in heavy leather stitchers, in the days before there was any dry bonded synthetic thread. Waxed or dry thread wrapped around the roller got all the tension it needled from friction of the thread wrapping around itself. The more wraps, the more tension was applied. Linen thread isn't as slippery as modern bonded nylon or polyester. Waxed linen is even stickier.

You can see this in action if you have one of the "Speedy Stitchers" that Tandy used to sell (and maybe still sells?). These devices have a bobbin of pre-waxed linen thread in the top of the handle. The waxed linen thread gets its tension by wrapping the thread around a small post on the way to the needle.

[Gymnast]

33 minutes ago, Wizcrafts said:

You can see this in action if you have one of the "Speedy Stitchers" that Tandy used to sell (and maybe still sells?). These devices have a bobbin of pre-waxed linen thread in the top of the handle. The waxed linen thread gets its tension by wrapping the thread around a small post on the way to the needle.

Thanks Wiz. Yes I know of the Speedy Stitcher, and I have got its cousin, the "Sewing Awl", and I have used with waxed thread for several small repair jobs and from before I got sewing machines.

33 minutes ago, Wizcrafts said:

Waxed or dry thread wrapped around the roller got all the tension it needled from friction of the thread wrapping around itself. The more wraps, the more tension was applied.

Interesting. So what you write here is that the tension back then was not controlled by the brake function on the roller, but by the number of turns. And then the roller was free to turn with no friction there - Am I right?

But I guess, that these kind of waxed threads are not used that much anymore with the sewing machines. But these Wheel tensioners are still being prefered on the heavier machines. Thats why I got the theory, that it might very well have the reason due to twisting problems.

5 hours ago, jimi said:

Hello Gymnast, Here is a link for a Singer industrial machin

Thanks Jimi for the links to other information on the 45k and 45b. Yes, this way the thread go from a top dics pre tensioner to a lower main Wheel tensioner on the face plate seems to have been repeated on many machines.

Edited January 5, 2020 by Gymnast

[Wizcrafts]

23 hours ago, Gymnast said:

Interesting. So what you write here is that the tension back then was not controlled by the brake function on the roller, but by the number of turns. And then the roller was free to turn with no friction there - Am I right?

Not entirely. The brake function does affect the tension on the thread wrapped around the roller. If the roller is totally free to rotate, the only friction is the windings of the thread. If the roller is tensioned by the beehive spring it adds friction to the thread in addition to the windings themselves. I have a couple machines with this bottom roller and I use it to fine tune the top thread tension (even though I use dry bonded synthetic thread). The roller braking spring would have an even greater effect with waxed thread that is stickier.

[Gymnast]

When I look at the shape of the roller perimeter on the 45k on the Photo, then it is like a V.

I have not seen good photos of newer roller tensioners. Are they still like a V og could they be like a U as seen to the left in the picture below?

The V-shape should provide higher friction between the roller and the thread than the U-shape.

[Gymnast]

On ‎1‎/‎6‎/‎2020 at 5:54 PM, Wizcrafts said:

I have a couple machines with this bottom roller and I use it to fine tune the top thread tension

When I read this statement, I get the impresion, that you get a major part of the thread tension from the tensioner with discs on the top, and a minor part of the tension from the main roller tensioner. However when I read the manual from Solar Leather on the CB3200 page 8:

https://static1.squarespace.com/static/544bce89e4b0eb63aaac64f3/t/57d4072346c3c43b079dadfd/1473513310952/CB3200+User+Guide.pdf 

Then you are instructed to adjust the main roller tensioner for "greater amount of thread tension" and the tensioner with discs adjust "tension in small amounts". I have got the same statements from an other manual from Artisansew. So here the disc tensioner is used for "fine tune".

However I have not found instructions in manuals, that ensures, that most of the tension is provided by the roller tensioner. I know from the experiments I did (first video), that a disc tensioner create more twisting if you increase its tension. So I suppose you would prefer to have most tension from the roller tensioner avoid too much twisting.

If you increase the tension on the roller tensioner too much, the roller rotation can be blocked, and the thread slides on the roller surface. I guess this would create unstable thread tension and should be undesireable.

I think a roller tensioner use the same principles of function as the winches used on a sailboat. One rope part from the winch can have very high tension, and the other rope part have very little tension. This is a couple of video that shows how such winches are used:

https://youtu.be/HW5lB8ive-4 (go to 2:23 in video)
https://youtu.be/d1pJ_45U-xo (an electric winch on car)

 

[Bert51]

This is the same tension system that I have on my Adler 105 and I just looked through the Cowboy manual that you posted the link to and if you look on Fig. 9-3 you will see the lower tensioner shown as "Main Tension".

It is the main Tension on all these types of machine,  as it goes around the Pulley 1 1/2 turns, the top tension I think only supplies the friction to get the thread to grip the pulley.

Bert.

[Gymnast]

Thanks for you reply, Bert. Yes, I get the same impression on the intentions of the design. How do the roller on the Adler 105 look like? Do it have a V-shaped perimeter for the thread as the roller from the Singer 45k ?