txgreenhorn Report post Posted August 3, 2018 Suddenly my Cobra 4 dont stop when I let of the foot pedal. Just keep going for anywhere a few stitches to 1 inch. I checked the obvious chain etc. all look normal. Any other ideas before I start digging and take things apart. Thanks Anna. Quote Share this post Link to post Share on other sites
DrmCa Report post Posted August 3, 2018 Clutch of servo? Quote Share this post Link to post Share on other sites
Wizcrafts Report post Posted August 3, 2018 See if the motor's speed pedal is letting the the motor control arm return all the way up against its stop. If you motor's arm has a stop screw adjuster, back it off to gain more upward movement. Quote Share this post Link to post Share on other sites
brmax Report post Posted August 3, 2018 If yours has the chain connecting the pedal, you can temporarily remove it at the motor linkage. This may help in seperating the areas of concern. Good day Floyd Quote Share this post Link to post Share on other sites
txgreenhorn Report post Posted August 3, 2018 It looks like arm is returning all the way and its not the chain have tried remove that. Clutch I have no idea I guess I get covers off tomorrow and see if I can figure out whats the clutch. I will also try the screw adjuster on the arm it does have one. Quote Share this post Link to post Share on other sites
Uwe Report post Posted August 4, 2018 Post some picture before you start taking things apart. If you're unsure whether you have a clutch motor or a servo motor, I'd recommend taking a step back and evaluate before you start digging in. General rule: don't turn a screw unless you know what it does (unless you can afford the machine to be down for a week or two while you figure out what went wrong.) Quote Share this post Link to post Share on other sites
JLSleather Report post Posted August 4, 2018 Yeah, first thing I'd check is if teh return spring gittin soft .. not bumpin the bumper, as they say. Or at least verify that the chain isn't hangin up on sumthin'. Quote Share this post Link to post Share on other sites
brmax Report post Posted August 4, 2018 I bet the servo looks similar to this one below. If it does theres no need looking for a clutch, you just have one gear Floyd https://www.leathermachineco.com/product/brushless-digital-d-c-servo-motor/ Quote Share this post Link to post Share on other sites
Wizcrafts Report post Posted August 4, 2018 5 hours ago, txgreenhorn said: It looks like arm is returning all the way and its not the chain have tried remove that. Clutch I have no idea I guess I get covers off tomorrow and see if I can figure out whats the clutch. I will also try the screw adjuster on the arm it does have one. I have a buddy in Saginaw, Mi who owns a Cobra Class 4. The original motor was a brushless servo that started spinning with a jerk at 200 RPM (divided by the speed reducer pulleys). It had an adjuster screw that set the upward control arm travel limit. Raising it to the top gave the slowest startup speed and longest travel downward (increasing speed) the motor was capable of. The motor uses reverse EMF to brake as you release or slightly apply the pedal. When the pedal is not engaged the motor should be freewheeling. There are graduated transparencies available to taper the speed change more gradually. Contact Leather Machine Company to obtain one in the mail. If your motor no longer brakes at all, it is failing. Consider replacing it with a newer type of servo that starts at zero RPM and increases very gradually without any modifications and has a physical cork brake when the pedal is backed off. Quote Share this post Link to post Share on other sites
chrisash Report post Posted August 4, 2018 A good rule for fault finding a engineering problem is to scribe a mark on both the fixed part and moving part before you turn anything, that way you can always go back to the same original position, rather than start building up lots of small differences that completely crap up your item Quote Share this post Link to post Share on other sites
txgreenhorn Report post Posted August 4, 2018 Thanks guys I will take some pictures later today and a video. It is a brushless servo so I guess I can stop looking for the clutch:) Quote Share this post Link to post Share on other sites
DonInReno Report post Posted August 5, 2018 On 8/4/2018 at 1:13 AM, chrisash said: A good rule for fault finding a engineering problem is to scribe a mark on both the fixed part and moving part before you turn anything, that way you can always go back to the same original position,... This is a super technique! A utility knife makes a tiny mark that’s little more than a small scratch. A more permanent mark can be made with center punch, carbide scribe, or even a small carbide burr in a dremel. Even something as simple as a Sharpie mark (if it won’t me smudged off), or fingernail polish, or a paint pen will provide a reference without permanent mark. Degreasing helps these marks stay in place. Quote Share this post Link to post Share on other sites
Squilchuck Report post Posted August 6, 2018 I had a similar problem. I talked with a Leather Machine tech at the Pendleton show and he showed me how to adjust a little piece inside the servo motor case. Fixed it easily. Give them a call or send a message to Cobra Steve. -- John Quote Share this post Link to post Share on other sites
