Cobra Class 4

[Wizcrafts]

Steve;

I wish that we could produce motors right here, in the USA, for a reasonable cost. This is so frustrating. I have ideas, but no money to try them out. It sucks being me ;-(

Here is what I did to Steve's motor to improve its controllability.

First, I set the chain from the pedal so it had only a little slack. Next, I turned the adjuster screw until it was just in the off position, then backed it off another half turn. I had to remove the rubber tip to accomplish this. I also set the top speed to about 3000 rpm, to reduce the shaking of the machine. This shaking was actually causing some skipped stitches.

The next item that made a difference was loosening the nut on the speed reducer, turning the wheel by hand to set the belt in a happy place pull-wise, then tightening it again. This allows me to handwheel around turns, where the motor is too touchy. It also reduces the strain on the motor and allows me to have better control at slow speeds than was the case when it was very tight.

I really want to open up one of these motors and see what can be done to fine tune the light baffle. I play steel guitar professionally and use a light beam volume pedal. There is a mechanical adjustment inside my pedal that allows me to control the off and full on settings. It does this by repositioning the variable density light filter, which is mounted on a piece of hard wood. Yes, it's Hillbilly engineering, but it works flawlessly! That device will gracefully change my volume from zero to 100% over a wide range of easily controlled foot movement. It even has a trim pot to set the sensitivity. So, I know that these things can be done.

My SewPro 500 motors have what I think is capacitive, or proximity drive, activated by the big lever under the motor. As one's foot pedal pulls down on the lever, the crank on the inside moves one electrically charged piece of metal towards another that is on the back of the motor (stator?). As it moves closer, the unit begins to spin. At a certain point it is physically stopped and reaches maximum velocity. The two pieces are separated by a thin dielectric insulator, to prevent arcing or meltdown. The starting position of the moving element is adjustable by a long hex-head screw, There is a brake that is also adjustable internally.

Edited June 3, 2012 by Wizcrafts

[Wizcrafts]

I bow to your knowledge and experience. Apparently you are more knowledgable and a better leather craftsman than Troy West, Bill Gomer, Jessie Smith, Don Buttler, Pete Correll and Bob Klenda. If you are unfamiliar with the above gentleman, I would suggest you research their work and if you look on the Leathermachine Co website, you will see all of them own and endorse a Cobra Class 4. By the way, since you are an expert, how about posting some of your work. Ken

Ken;

Read my post #49. I talked you up as having made good points at the beginning of it. I also disclaimed being an expert. I'm not looking to get into fights here; heck, we've never even met. Everything I post is either my opinion, or from my experience; mostly the latter. The dealers and their paid mechanics are the experts.

Edited June 3, 2012 by Wizcrafts

[Dallas Cowboy]

I bow to your knowledge and experience. Apparently you are more knowledgable and a better leather craftsman than Troy West, Bill Gomer, Jessie Smith, Don Buttler, Pete Correll and Bob Klenda. If you are unfamiliar with the above gentleman, I would suggest you research their work and if you look on the Leathermachine Co website, you will see all of them own and endorse a Cobra Class 4. By the way, since you are an expert, how about posting some of your work. Ken

Ken-not once did I say I was an expert at any of this or better than you. Can you quote me saying otherwise???

[Wizcrafts]

I've added some new details to my post #51. If you read it when I first posted, please re-read it.

[busted]

I wsh I waz az smrt az u r.

The Class 4 Cobra comes with a speed reducer. As far as the content of this thread goes, I am astonished how many people here are expressing "Bright Ideas" that have no idea of what they are talking about. Seems "funny" that one or two people are having problems with a machine that the rest of us that own and use them get along great with. If you think you are having a problem with Cobra Steve's customer service, "you might bear in mind, that your are in a teeny-tiny minority!" I have been doing business with this man before he had his own company. In fact I have bought machines from him on 5 occasions totaling more than 5, some new-some used. I have had a couple of little problems with two of them and it has been taken care promptly and graciously. Once someone forgot to pack in some extra attachments I had ordered, one used machine had a motor problem, and I caused a couple of problems by letting Newby's sew on my machine. He didn't charge me for talking me through adjusting my mistakes either. As stated earlier, There is a definate learning curve on learning to sew on a sewing machine. Is it possible for the motor to be bad on the sewing machine in question, of course it is. Is it possible there is some user error here. Probably.

Is it possible that it is a combination of motor problem and operator error both? Could be. If you are using a household Singer sewing machine, you may well not know how to sew with a heavy leather sewing machine or stitcher. If you haven't sewn quite a lot on a heavy stitcher, you probably have a lot to learn.

Properly preparing your work to be sewn on a sewing machine is very important. Having your tensions set incorrectly can cause real problems. Not oiling your machine can cause problems as well as shortening the life of it. For an experienced sewing tech to say a machine is easy to sew on is different than saying doing a good job on a certain sewing machine is easy. I sew belts and skirts on saddles pretty slow. I know guys that burn through them 9-0 and theirs look as good as mine do. They started a long time ago when they were kids and do more of them than I do. Some machines are easier to sew with than others.

As far as the bumps on the bottom go, When I apprenticed under a pretty damn good saddlemaker, we dampened every stitch line in veg tan, tapped it to make it look just a little better. I still "set" the stitch line on about every project I sew. I was told," it is a matter of workmanship"

The motor set up on my Class 4 suits me just FINE! I don't need an upgrade. Just my 2 cents worth! Ken

OK, I'll shut up.

The topic is about a Cobra Class 4, which IS already equipped with a speed reducer pulley. My Cowboy CB4500 uses the same pulley (~3:1) reduction system. By the time the small output pulley feeds the large one on the flywheel, we are looking at anywhere from 8 to 9 times speed reduction and torque multiplication (depending on motor and flywheel pulley diameters).

I am hopeful that this discussion will lead to the development, or discovery of a better motor for these machines; one which won't drive the price up too much higher. There are already better motors available, but they cost a lot more than the servos included as standard equipment.

I can assure you that our dealers are discussing this matter and looking into possible alternatives. However, these new motors need to be tested under load for prolonged periods of time to ensure they can stand up to the heavy loads imposed by big machines sewing heavy leather, with big needles and thick thread.

[ChimeraKennels]

Ken,

I don't have a dog in this fight, but man...you are not helping. Being disrespectful and rude doesn't make the machines work better or the people that have the machines any happier. Sailrite also states they don't offer servo motors as they are disappointed with their performance and they only offer clutch or MC-SCR motors as a result.

Wizcraft and Busted both have done nothing but offer their time and help to me when I needed help...and I for one appreciate it. When I get ready to purchase a Cowboy machine some day, I will either get a low rpm clutch motor and put a speed reducer on it OR better yet ask if I can get an SCR motor. Yes, a clutch motor runs the entire time it is "on" even when it isn't being used...and uses energy as a result...but realistically, I don't think that is costing big buck for people that only use the machines a few hours a week.

[Samalan]

I just want to say that I also have a Cobra class 4 with EPS and I've never really looked at the travel of the actuator before you brought it up in your thread. I looked at the one on my machine and it's the same movement as the one in your YouTube video. I think it's due to the fact that I have experience using a clutch machine I find the Cobra easy to use. As a caveat, I did move a lot of stuff around under the machine, but I don't think that changed the throw of the motor actuator.

I hope the Cobra works out for you as I've seen some of your work and it looks great.

[Iron Pounder]

I found this thread trying to find a solution for my machine set up. I sure don't want to get into a disrespectful back and forth so I will say this up front. I know NOTHING about sewing machines other than just what my Grandmother has showed me and what a guy just learns as he goes I guess. having said that I think I may be able to add some possible help due to knowledge I have about dc motors themselves. I have a part time day job where I work on scooter (mobility untis). The scooters we have use brushed dc motors for the most part and some brushless. We use a simple handhelp programmer to change several things that affect the proformance of the scooter. I had a scooter have this problem this morning... Here is what it was doing. The customer would barely push the lever to move the unit and it would take off at full speed (at least as fast as the max limiter was set to. It had no ramp it was simply on or off. Of course the factory told them just turn down the limiter until you "get used to it", ha. They knew it shouldn't act that way so kept after them until they sent me out. I plugged the programer in and found the base program ramp was set @ 2 instead of a full range of 10 (10 being a full swing of the thro to reach full max speed and 1 being full at on). Our programmer can do way more such as modulation adjustments which take some bite out even further for someone looking for very smooth kind of alomost flat responce. My QUESTION is doesn't this sound like the very same problem? Without a schematic I have no way of knowing if this can be adjusted without a new chip being burnt or not. With no disrespect to Steve and his machine it sound like the motor could be an economical unit and they are typically built with non programable chips.

Just so folks don't think I'm working over Steve here I will say this he is on very short list to buy a machine from, and I have never even spoke once to him. Having said that it seems this matter needs further attention.

[Wizcrafts]

I found this thread trying to find a solution for my machine set up. I sure don't want to get into a disrespectful back and forth so I will say this up front. I know NOTHING about sewing machines other than just what my Grandmother has showed me and what a guy just learns as he goes I guess. ...

My QUESTION is doesn't this sound like the very same problem? Without a schematic I have no way of knowing if this can be adjusted without a new chip being burnt or not. With no disrespect to Steve and his machine it sound like the motor could be an economical unit and they are typically built with non programable chips.

What you don't know is that these brushless servo motors are controlled by an LDR module, using an LED as the source and a 1/2 inch wide piece of thin steel pivoting on the inside of the actuator lever shaft to break the beam. The steel light brake moves between the LED and the LDR, which has an aperture of about 1/8 inch. It doesn't take much movement to block the LDR. The LDRs being used must have a wide range of tolerance, like 25% or worse, because some motors are easily controllable at slow speeds and others have a hair trigger, from off to full on.

The inside movable baffle is set so that it is normally not blocking the LED from striking the LDR. In the case of the motor I tested a month ago, it didn't even take 50% blockage of the LDR opening to go to full speed. That means it went from 0 to 3600+ rpm within about 1/16 inch of motion inside the box, on a 2 inch long baffle. This translated to about 1/8 to 3/16 inch motion at the outside speed lever hole, which is about 4 inches from the main shaft.

For these motors to be able to be controllable by anybody with less than perfectly steady feet, the LDR should allow the baffle to affect the resistance over the entire range of its aperture, not just the first half. Also, the aperture could benefit from being a slot, rather than round; say 3/16 to 1/4 inch wide by 1/8 inch high. A matching wider LED source would help, as would a graduated gray scale light baffle, made of high-impact plastic, rather than sheet metal.

So, the slow speed controllability of your motor is dependent on the taper of the LDR module, as well as a couple of resistors, and how close they are to design specs. There are no trimpots visible on the circuit board that the LDR plugs into. It is all or nothing.

[Iron Pounder]

Wizcrafts I don't know what to say other than that is unfortunate.