Adler 104 stitch length - adjustment manual

[Pterytus]

So I DID go a bit further and collected some data ;-)

The first graph shows F and R stitch lengths in blue and red (x-Axis is number of revs of knurled SLL-nut) - measured data and approximated quadratic equasions to ease calculation.

So if you reduce lever travel below the intersection at 5.2mm stitch length (F) accordingly you'd end up with equal stitch lenths F and R by just flicking the SLL up and down.

The second graph shows pivot point of SLL (0|0) and flat SLL-frame surface at x=59mm in blue. Changing lower SLL-frame geometry from blue to red would result in the required lever travel reduction. True: You'd lose approx. 1.5mm F stitch length, because R only goes up to 8.1mm - which should still be ok. Maybe it's just a matter of opening up upper SLL-frame. This should be possible because the rest of the machine is capable of 9.7mm.

The red line in the second graph is roughly a straight line so it would not even be necessary to machine some complex contour but just add some kind of wedge etc. to make the modification possible.

I'm not sure if it really is necessary/worth to realize that in hardware (see above) but it seems realistic and not too challanging.

Anyway I wanted to share my findings with you guys :-)

 

[Constabulary]

a mad scientist you are Reminds me of curve sketching and things - didn´t like it as well as stochastic (I get goose pimples )

Edited December 14, 2019 by Constabulary

[Pterytus]

Ah, I've been called much worse! ...and with reason ;-)

And sorry, did not intend to give anyone geometric nightmares, they're THE WORST! Next time I'll just show you the (completely non-stochastic) formulae, btw., they're y_F=-0.021x²-0.433x+9.654 and y_R=-0.018x²-0.264x+8.082, that better? :-D

Anyway, NOW would be a good time for a 3D-printer. Just to verify (or falsify) my madness. So it's metal-or-nothing for me now...

[Bert51]

Some of us think we are quiet sane, but there again I have also been told I am as mad as a hatter, I think you maybe in good company.

Sit down put up your feet and stay awhile, you will enjoy yourself.

Bert.

[Constabulary]

11 hours ago, Pterytus said:

y_F=-0.021x²-0.433x+9.654 and y_R=-0.018x²-0.264x+8.082, that better? :-D

Definitely better - now I get it. So what you need is a curved center piece from the flux capacitor,  I think. Flux capacitor parts are universal fit and solve everything.

Sorry can´t really help much more here. My way would be the angle bracket with 2 limiters like they have used on the later 104´s. Thtas probably something even a later buyer will understand (one day you will / have to sell it)  instead of riddling what this "odd shaped / non standard" piece is. And when it is worn (if printed out of plastic materials it will be worn sooner or later) he will be screwed. Keep things simple!   My 2 cents.

[Pterytus]

The main thing to find out was the "adjustable vs. built-in" problem.

And because it seems to be built-in mainly (not that you could not make it even worse by bad adjustment) and cannot be cured with a screwdriver, the matter is kind of "solved" for me anyway. The work-around is independent from that. So thank you for your helpful input!

Sure, I'd keep the original frame anyway and the plastic would only be to test if it works, maybe optimize it and finally build a copy from metal which lasts. I'm pretty happy with all-metal machines and would not add something plastic for real usage.

----

If I actually HAD a flux capacitor (and maybe a Delorean), I'd travel back in time and tell the Adler guys to place the damn pivot point in a better place to solve that problem once and for all - unless, that is, they'd put me in a loony bin, which is a far more likeley scenario... :-)

[Pterytus]

Okay, I just HAD to test it ;-)
No 3D-Printer, no plastic. Metal it is - so it took some time but it came out ok, I think.

Before, with the flat frame it was:
short: F1.4mm/R2.1mm (50% off!)
middle: F4.8mm/R5mm (that was the only SL-area which was ok)
long: F9.7mm/R8.1mm

I tried three different stitch lengths with the new SLL-frame F and R and they came out fairly equal:
short: F1.9mm/R2.1mm
middle: F4.6mm/R4.8mm
long: F8.1mm/R7.9mm

Which is enough for the 2-3 backwards stitches I usually need. So now I can rest!

[Constabulary]

Very nice! Still wondering what the "original issue" was - or is. Anyway - as long as it works for you this way its a good solution. Well done!

[Pterytus]

Well, with me sometimes it's "personalizing" my machines - I just can't leave the things the way they are. And if I can improve things in the process (or at least don't make 'em WORSE ;-) then I'm likely to go for it.

Now I do not have to adjust backwards stitch length once I change forwards stitch length. I know me: I'd just forget it and create "false" stitches while trying to lock a seam. Especially on leather I'd rather avoid that.

Oh, glue is dried - so back to sewing X-max presents ;-D