Consew 226 Strange Resistance

[Pintodeluxe]

I'm having an issue with a Consew 226.  When turning the handwheel there are two sticking points in the rotation.  I wanted to determine weather it was friction in the upper shaft or lower shaft, so I slid the timing belt off and found the two sticking points were related to the lower shaft.  So I reinstalled the timing belt, making sure to align the arrows under the machine (they were aligned before as well).  

I had to replace the hook anyway, so I went ahead and swapped that out.  I chased the old hook out with a 3/8" dowel to prevent the gear from moving.  Machine now sews well, but still has two points where there's more friction somewhere in the lower shaft.  

- Adjusted for symmetrical foot lift

- Adjusted feed dog fore/aft position

-Adjusted feed dog height

- Made sure rocker bar spacing was 8.5mm @ zero stitch length 

All of these settings were very close to correct, and didn't seem to improve the friction issue I was having.  I can remove the drive belt, thread, needle, and throat plates and feet and still have the two sticking points.  Decreasing the foot pressure springs to zero makes a very subtle improvement.   

I have obviously oiled each point tenaciously, but still have two "sticking points" that occur when the take up lever is approaching top position, and approaching bottom position. 

Any thoughts?     

Edited September 18, 2020 by Pintodeluxe

[SARK9]

One other thing to check, if you haven't already,  is the bobbin case opener adjustment...if too tight they bind a bit.

-DC

 

[Pintodeluxe]

That's a good point.  I could see that binding some machines.

Mine was binding with or without the bobbin opener installed.  

[Constabulary]

is the hand wheel too tight? Try loosening the hand wheel set screws a bit and the screw on the top shaft end. Or is it probably when the machine is working against the foot pressure spring?

Edited September 19, 2020 by Constabulary

[Uwe]

The twice-per-handwheel-turn tightness/friction points to something that moves or rotates twice for every full hand wheel rotation. The hook area is a key suspect since parts move twice for handwheel rotation.

I’ve worked on machines where the large hook driving gear was not centered very well with the smaller gear on the hook’s shaft. It’s possible to adjust hook timing correctly even with the large gear being off-center with the small hook gear. Since you slide the large gear sideways to adjust hook timing it will end up being slightly off-center most of the time. A problem may arise if the large gear is far off center relative to the small gear. If that’s the case you can separate the gears and adjust the tooth meshing by one tooth to get the large gear to run better aligned with the hook axis. Running the large hook driving gear near the gear’s edge may cause tightness because of imperfection of the gear teeth near the edge.

It also takes just a little bit of dirt or grit stuck between the teeth of the hook axis gear to cause tightness or friction on every hook rotation, or twice per hook driving shaft rotation. Some oil and a (dedicated) old toothbrush do a nice job of cleaning gear teeth.

Dirt stuck in the mechanism that drives the bobbin case opener is also a suspect.

[Pintodeluxe]

Uwe,

That makes sense to clean the gears and try rotating the gear one tooth.

I was careful to keep the small gear from rotating when I changed out the hook.  However, I suspect the former owner might have messed with it.  

Thanks to all who commented!

Very helpful suggestions.  

[Pintodeluxe]

So I followed Uwe's advise, and cleaned and lubricated the bobbin opener mechanism.  That helped some.  

Next I rotated the large gear one tooth on the small hook gear.  That seemed to make it worse.  Then I tried one tooth in the other direction, and that helped to smooth out the lower shaft rotation.  

I think that fixed it.  Sews nice.  

Seems funny that the hole in the gear wouldn't be centered.