Cobra Class 4

[particle]

Hello all - regarding the original post, he's referring to my machine. He came over last night to watch me form a couple holsters, and I showed him my Cobra Class 4 and my Tippmann Boss. I'll go ahead and address and clarify the things he mentioned, as well as provide photos and a video example.

First off, some of you that have had your machines for more than a few months - do you even have the same servo motor that I have (TN-411)? (for the record, I have NO idea how long this particular motor and its related internal speed switch have been supplied with these machines, but I think it's a fairly recent addition)

http://www.youtube.com/watch?v=QReQK-ipQjA

The tension of the chain has nothing to do with the sensitivity of the actuation lever. A looser chain just means the foot pedal is going to sag/hang closer to the table. Loosening the chain will not magically make the servo motor's switch work better and give you a broader range of motion on the lever.

Regarding the puckering on the back of the stitch - I'm not sure the OP was aware that was pretty typical for a sewing machine when sewing leather, as you rarely see it in final photos of holsters because they get smoothed out by various methods. That being said, there is a notable difference in puckering depending on the bottom plate in use on the machine. For example, with the standard bottom plate that allows the use of the lower feed dog, you get almost no puckering. But wait - is that really true? Yes and no. I've thought about it for maybe 30 seconds - what I assume is happening is you immediately get the puckering as soon as the needle is punched through the leather, but as you progress forward with your next stitch, the lower feed dog actually presses against the bottom of the leather to help feed the leather forward, while at the same time pressing the puckering back nearly flat. Also, you don't get the same constant elevated ridge due to the shape/design of the lower feed dog and its plate like you get with the holster and stirrup plate.

The puckering has almost nothing to do with presser foot pressure settings - I'll provide a photo example for those that don't agree.

Here is a photo showing the way the machine was sewing when I pulled it from the box. No adjustments had been made to the machine at this point. This was using the standard lower feed dog and its plate and the left to on the presser foot.

As you can see, there is minimal puckering.

Here you will see stitches with the machine in 3 different configurations.

A= My modified stirrup plate with an adequate amount of pressure from the presser foot.

B= My modified stirrup plate with NO pressure from the presser foot (the leather was lifting off the stirrup plate as the needle was retracted, resulting in skipped stitches - NOTE that I started pressing down on the leather with my thumbs to keep the leather from lifting and to stop the skipped stitches)

C= The holster plate with just enough presser foot pressure to keep the leather from lifting off the surface of the holster plate

As you can see, all three stitch lines exhibit the same puckering and elevated section, regardless of presser foot pressure, and this is directly related to the lack of the lower feed dog pressing up on the bottom surface of the leather to flatten everything back out. It's not a flaw in this machine or any other machine, but this demonstrates why the much more expensive needle and awl machines are so desirable.

This photo shows what the stitching looks like with my modified stirrup plate after being dampened and hammered flat with a smooth face hammer.

What's all this talk of my modified stirrup plate? Why don't I just use the holster plate since I'm making holsters? Why am I using the stirrup plate if I'm not making stirrups?

This photo shows the wrap on the back of my Avenger style holster using my modified stirrup plate. I'm sure some of you will think/say I'm building my holster wrong. yes, I could modify the belt loop to be narrower and stay further away from the bottom of the slide. Or, I could just use a custom "Holster" plate by modifying my stirrup plate that I would likely never use otherwise. The holster plate that ships with the machine is very long and wide, and snags on the edge of the reinforcement on the back side. The stirrup plate is the perfect size (very similar in size to the stirrup plate I was using on my Boss which my patterns were initially built to work around). If I use the standard holster plate, I would have to angle the holster to lift the reinforcement up and onto the top of the holster plate at various points along my stitch line. I could sew the opposite direction to put the narrow side of the holster plate towards the reinforcement, but I still have the problem of the leading edge of the holster plate snagging on the reinforcement.

I'm still able to use the double-toe presser foot because it makes contact on both sides, even if just barely. This may not be the case with all machines, as my presser foot doesn't quite seem centered with the needle bar.

Here is the stirrup plate as it came from Cobra.

Here is my modified stirrup plate that works PERFECTLY for my intended use. I've also included a comparison photo alongside my Tippmann Boss stirrup plate.

And here is a photo of a reinforcement sewn with it.

All in all, I am very happy with the machine. Like anything, there is a serious learning curve to using these machines. It took me a while to learn and 'perfect' the Boss, and it will undoubtedly take a while to master a powered machine. I just wish the servo motor was easier to control - it's simply not as "user friendly" as I imagined it would be.

Yes, I have contacted Steve but honestly felt like the conversation wasn't going anywhere because he simply didn't understand what I was talking about. Hopefully these photos clear things up for everyone.

Edited May 26, 2012 by particle

[dirtclod]

Have you tried changing where the spring hooks on the arm and tried moving the hook on the chain to another hole ? I don't know if that would change anything just wondering.

One machine i have has a servo motor and i have all kinds of control with it. Not sure what brand of motor it is. To tell the truth i never really have looked to see how it works.

[particle]

Yes - the spring just adjusts the resistance, while having the chain on the furthest hole provides the most control by giving you more travel to vary the speed. But when you're talking about such a small amount of effect travel range, it's practically no change at all.

[tnawrot2]

If you were to extend the lever that the "S" hook is attached to, by attaching a flat steel piece to the existing lever with two bolts and then attaching the "S" hook to the other end, you will increase the travel of the foot pedal that engages the motor.

[particle]

Yep - did that too. I didn't take any pictures of it, but I have a 1/8" x 1/2" x 12" aluminum bar that I mounted to the lever, and drilled holes in the aluminum every 1". With the hook at 12", the motor ran continuously (slowly) because the weight of the bar and the chain that far out was enough to actuate the motor. With the hook at 6", the motor stopped running on its own, but there was barely any increase in effective range of motion - not worth risking my 2 year old child grabbing onto the bar and giving it a good tug and bending it or breaking the motor's actuation lever.

[K-Man]

Yep, Particle, I have the same servo motor model you do. Though I have the holster plate, I've never used it to make our holsters, and we've made ones very similar to yours. The "bumps" have been a common occurence on whatever I sew with the machine and are very mild/slight. It happened with the Artisan Toro 3000; it's happened with every machine (441 style) that I've owned/operated.

Edited May 26, 2012 by K-Man

[Big G]

i have had my cobra for 1 yr this month , has the same model motor as yours , also the speed controller works just like yours . the display on my motor displays rpm, i usually sew at 600 rpm. i noticed yours displays 1-?. probably some way to change display.

i have had my cobra for 1 yr this month , has the same model motor as yours , also the speed controller works just like yours . the display on my motor displays rpm, i usually sew at 600 rpm. i noticed yours displays 1-?. probably some way to change display.

[dirtclod]

Particle i just came in from sewing some things and i checked my machine's pedal travel. It was around a 1/4 from stopped to full speed. It has a clutch motor and the pedal has rods instead of a chain. I can sew 1 stitch if i want to no problem. Personally i never had noticed it on my machine till it was brought up here. Now a guy i used to work for has his pedal set to where you have to really push the pedal before it will start sewing and it drives me crazy every time i have sewed on it. I guess it's just what ever you get used to.

[Cobra Steve]

Hello everyone. Regarding the motor issue. We are limited to 3 major motor factories. We have tested motors from all 3 of these factories. We chose this style because after testing them, they performed better than the other 2. Not only myself, but Bob from Toledo, Ronnie from Tech-sew, and most everyone else uses the same motor. Perhaps the circuit board is defective. If so, we will replace at no charge. This was a very interesting thread and I learned a couple of things so thank you all for participating. Please call me with questions if you have any. Thanks, Steve

[Wizcrafts]

I suspect that the problem with these motors lies in the quality of the movable light baffle, or maybe even in the light sensor module itself. If I can get my hands on one of these motors I will play with it and see what I can learn about any possible mechanical adjustments that can be made to spread out the speed over a wider range of motion.

Edited May 30, 2012 by Wizcrafts