friquant

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Forgot that you have two hand wheels! Or one giant handwheel and two motor pulleys (one on the motor, one one the patcher). This is going to mess up my terminology notes for sure 🤷‍♂️ From your video, I'm not sure if that lateral motion is a problem, a feature, or neither. Is there anything along the main shaft that looks like it's intended to impede this lateral motion?

Are you saying the main shaft moves horizontally (and takes the handwheel with it)? Send a video maybe. You might try preventing the horizontal movement to see if the machine can still turn without binding up. If it binds up without the horizontal movement, then maybe the horizontal movement is by design. Also check to see if there are any screws loose near the main shaft whose job it might be to keep the shaft in place. On domestic machines I've seen C-clips used to prevent horizontal movement of the hook shaft. If a C-clip were missing, there would be a groove cut in the shaft but nothing in it.

You may be able to learn what is out of adjustment by slipping the belt off, and hand wheeling slowly. If there's enough force generated to break the thread, you'll likely feel that at the handwheel and you can see what is binding or yanking. It may be easier to feel if you are stitching somewhat thinner material. I'd also be interested to see what the hook to needle timing is. Beautiful old machine 😍

When I feel two pops it's when the thread has not cleared the latch by virtue of the latch opening but rather by the thread being yanked past it. Maybe you can find out what opens the latch. Removing the bobbin case may help you see additional mechanisms at work.

The latch is the area between these two red arrows. It's also what keeps the bobbin case from spinning as the hook spins. The latch has to open at least once during the stitch cycle to let the thread pass.

What jumps out at me is that the latch opens abruptly. Not sure if that's normal for this machine. I don't see the bobbin case opener..maybe it's internal?

I'm enjoying learning hidden qualities of the thread check spring. Which of these screws do I loosen on my 341 to effect #1 and #2?

I can see that the timing is off, as it moves too far clockwise / not far enough counterclockise to drag the thread around the bobbin. (Even if it did manage to pick up the thread in the first place) I have not been able to find a service manual for this machine. As @Cumberland Highpower said: "Just look over the mechanisms, you should be able to "see" what the problem is with a little careful analysis." I would start by removing/opening covers. See if you can trace the movement of the hook all the way back to the main shaft. That is, figure out which shafts, rods, gears, cams, and/or arms are involved in making the hook turn. At least of of those members will be adjustable in a way that allows you to change the hook timing. Feel free to post additional videos as you make progress. Once you figure out what to adjust to effect a timing change, try setting the hook so that in its clockwise swing the point of the hook only goes about 5mm past the needle before the hook turns around to go counterclockwise. I expect that will put you in the ballpark where it will actually sew.

Wow it's hard to see down in there. I'm used to having a vertical-shafted hook where you can see the thread take a round trip. Can you take one more video with the feed dogs removed, as close as you can but still in focus, and move the handwheel very slowly. (About four seconds to do a full turn ought to do it.) Then maybe we can see what's clunking around. If we can't see it from above, you may be able to get a shot from below the left side. (This may require partially disconnecting the arm that the feed dogs ride on so we can get a better view) If using an iPhone, Uwe made a demonstration of how to lock the focus on an iPhone for taking close-up videos: https://www.youtube.com/watch?v=twl_V_vlq2Q

Can you post links to the pieces one would need to buy in order to build this setup? I'm interested

Yes I mean the pulley on the servo motor. They are typically 75mm. If it has a 15mm cylindrical shaft, that pulley can be replaced with a 45mm pulley for about ten dollars, which will slow down the machine.

Yes, do post videos. Have you done timing on your RB5?

In practice, yes. What I really mean by this distinction is whether they have a minimum speed or not, and the ones with a digital display seem to have a minimum speed. They're either not moving at all, or they are moving at least at their minimum speed. And by analog, I mean you can ease into the gas pedal and start out at a crawl. What is the minimum speed of the servo motor on your consew? It's easy to find a "digital" servo motor with a minimum speed as low as 200 rpm, which with a 45mm motor pulley gave me 111 stitches per minute with an 80mm hand wheel pulley. Your setup may be slower if your handwheel is larger than 80mm. If you want slower than that, they you either need a speed reducer, or an "analog" servo, or both. I don't work with thick leather, so I will let others chime in regarding whether you will need a speed reducer in order to stitch the thick materials you are targeting.

Found a solution for the slack thread not jumping through the latch. That is, set the thread check spring to begin adding tension at that point in the stitch cycle. Still do not have a fix for the thread being off the shoulder.