GerryR

@Samalan made it a math lesson, but I have a center finder.

7/8 + 24-1/2 = 25-3/8 ...you got ahead of yourself. 24-1/2 + 3/8 = 24-7/8

Definitely handier, if you have one. Alternative methods are good to know.

He got his ruler at a discount, only 11" long!

For shorter lines, you can use a compass and swing an arc on both sides of the line from both ends with the compass set at a distance greater than half the line length. Connect the intersections of the two arcs on each side of your line, and you have a line perpendicular to the original line directly thru its center. Helps if you don't have a ruler. For longer lines, make a compass from a piece of string and a pencil or marker.

Cooling, you can run a servo at very low speed (its just a motor), but you have to current limit so you don't over-heat it, and when you current limit, you lose torque. By requiring a minimum start speed, you assure that someone can't run at very low speeds for any length of time and destroy the motor. At that minimum speed, the cooling design parameters are met. (A stepper motor is designed to remain stopped with the current being sufficient to hold the designed load and not destroy itself, though many systems drop to a lower current when stopped, as you don't usually need the full current to hold the load when stopped. Many DC servo systems do the same when the load is stopped by current limiting. That is not necessary on a sewing machine and would be more expensive to implement.)

You can run the 550 watt motor from the 750 watt control unit. The other way is not advisable (750 watt motor on a 550 watt controller) unless you know you won't exceed the 550 watt load.

In the system I have (AC-VFD), the motor is spec'd at 35-459 RPM, 10-90 Hz. That is the output from the 5:1 reducer (gearmotor). I have a 1-1/2" motor pulley going to a 7" drive pulley for another 4.67 reduction giving 7.5 RPM at the machine at 10 Hz (minimun specified operating frequency for the motor), which amounts to 0.125 revs.per second or 1 revolution every 8 seconds. But that is not the point. The point is that when I hit the pedal, and the motor starts to move, I am easily in the safe operating zone of the motor, 10 Hz minimum. It would be absurd to run the machine at 1 stitch every 8 seconds for any length of time. The idea is to keep the motor happy and stll be able to do some controlled slow stitching. Just my $.02

Keep rambling, good info!!

Yes, but that would defeat the purpose of a softer start, which you are trying to achieve.

Those optical filters are nice, but they defeat the purpose of starting the motor at the so-called required minimum speed, which is probably not necessary in most instances.

Yes, I stated that both motors would generate the same amount of heat and meant power; that is where the heat management comes into play, and like you stated, the choice of materials used.

Power is power, so if it requires a certain amount of power to pierce the leather, both motors, whether 9 coil or 12 coil, will generate the same amount of heat. It all depends upon the heat management of the motor design, so "should get rid of the heat better" is up for grabs until the longevity of the motor is proven. 12 coils will distribute the heat better, but it is still within the confines of the motor housing.

Torque from a motor depends upon current in the windings and the number of poles (basically, I'm not a motor expert) so without a speed reducer of sorts, the motor has to be very robust to maintain high torque at slow rpm and cooling is paramount. The speed reducer gets the motor rpms up where cooling is better, current is lower and torque is higher because of the gearbox. As far as the OP is concerned, I don't understand why he can't just tell us his new motor/system specs; why all the mystery?

I know, I just wanted him to say it. I still prefer VFDs with 3-ph gear motors over DC systems. JMO, YMMV.

So, you have a high torque, slow start-up speed motor, which means you have a special controller for it (?). What are the power requirements for it? How big is the motor? What are the output shaft dimensions? What are the mounting requirements for the motor and controller? Is the speed controlled by a foot pedal or a dial on the control box? Do you have provisions for a position stop (needle up-dwn)? These are just some questions I have for any new system I would consider. It sounds like your system already exists, so should be easy to answer.

Links to AC Drive Components: VFD good for up to 1HP 3-phase motor: https://www.amazon.com/dp/B0DFB57721/?coliid=I8NFU0YE5UPT8&colid=17LBFSFMFWW6H&psc=1&ref_=list_c_wl_lv_ov_lig_dp_it Note: I bought mine through Ebay, but this is the same one. Motor: https://www.bodine-electric.com/products/ac-3-phase-inverter-duty-gearmotors-and-motors/42r-fx-parallel-shaft-ac-3-phase-inverter-duty-gearmotor/ Note: I was able to get model 2263, which has 58 in-lbs. of torque and 340 RPM at 60 Hz. You can choose outputs suitable to your needs and even get right angle output shaft versions. Just for comparison, the DC servomotor I was using was rated at 28.8 in-lbs. Foot Pedal Control: This is where I got a little creative. I took a TIG welder foot pedal and did a little rewiring. I got the unit off of Ebay: https://www.ebay.com/itm/176920994141?_skw=TIG+Welder+foot+pedal&itmmeta=01K01RR8XF07B0ETNHVT3SNZC6&hash=item293150215d:g:7KQAAOSwha9jZI28&itmprp=enc%3AAQAKAAAA8FkggFvd1GGDu0w3yXCmi1cdg2dYapN7bLOj7QNBNYvFBgb9nYOw6ivyhEaLfbTDARnhlFmmmIvRE5v%2BmSHS6NHzBxmYRm%2FS%2FOUguxh4QASZ6dKnq4aAfCKcCK9LWjU5OyPxxvNKcH3CjV9WGIL7ylcLvGzb6%2Bdvpe9MAB418aLD72qlvGirmqZ2XNTPpOEnSdadqe%2BJUuU70vTyKzaCPmAPE85JgmuvVu3AwzJYH9iW5vfdQNC7nCE8q1Im3b6Kp6cynjjiIrNBiNTH1T%2Fur%2B7h1JYK8hs%2Bt5hyHSlK4eaNsbSQ%2FRi%2Bmrmp2OVY%2BjRpfg%3D%3D|tkp%3ABk9SR4CP4biAZg I rewired it so the knob-controlled pot limited the top speed so the foot controlled pot had full range to that limited speed. I put everything in a case: https://www.ebay.com/itm/165626696069 These are the basics. I added circuitry for a position sensor that worked off a jog button. I don't use the position sensor, but it is available if I ever want to use it. The jog is so slow that I can stop the needle anywhere I want. This should give you a good start. Feel free to ask any other questions you might have. Happy to help!

I realize that you already have the DC servo drive, but for future projects, you should consider an AC system with a variable frequency drive (VFD) and a 3 phase inverter rated gearmotor. As an example of the control you would have, a 3 ph, 3/8 HP, 5:1 gearmotor can be operated from 10-90 Hz giving an output shaft speed of 35-459 rpm. Any speed running with less than 60 Hz is in constant torque mode, and greater than 60 hz is in constant horsepower mode. The speed is controlled by a variable pot, not a link to an optical control and is easily top-speed adjustable, giving full range of the pot for control to the selected top speed. The VFDs are relatively inexpensive, but the motors are a little pricey depending on your source, but for control, I think they are better than DC systems. JMO, YMMV. P.S. Beautiful job on that machine!!

Good advice; sanding it is not a good option as it will just ball up and clog the paper; it needs to be shaved, not sanded. Is the back side in good shape? Can you just flip it over and use that until it needs refinishing, and then have both sides redone at one time?

I'm not familiar with the pneumatic foot controls so I'll assume (ass-u-me) they actually are piped in to the actuating cylinders and are pneumatic switches. If this is the case, then yes, it can be done using electrically controlled solenoid valves and electrical foot switches and an appropriate power source, depending on the valves chosen. If you want to replace the pneumatics completely, then that is more complicated.

Well, according to the way the OP responded to my post above, he claimed he achieved all the points I mentioned, which included a 5:1 gear reducer. Must be the language barrier, as I mentioned possibly using an AC servo control, and I doubt he has done that.

My opinion, from a mechanical standpoint, is to start with a servo that has an integral 5:1 gear reducer. This automatically increases torque and allows the servo to start at a higher speed. This is easier on the motor and the drive electronics. Also, a dual pot foot pedal, one pot sets the max speed and is hand adjustable, the other is the foot-operated pot so you always have the full range of the foot pedal for whatever your max speed is set to. I have this on my system which utilizes a variable frequency drive (VFD).) You might even consider offering an AC-servo system (VFD controlled) instead of a DC system. The electronics are inexpensive, especially for 1 HP and less, however, they require a 3 ph motor to operate, but they can be had with integral gear boxes. As you are designing from scratch, you can spec your own motor. I have had two systems with AC servos and two with DC servos and personally prefer the AC units. Also, a needle position sensor can be implemented with a proximity sensor and metel "flags" put at appropriate locations and you can have multiple flags to stop at various needle positions. If this is implemented along with a jog button or heel pedal switch, you can control all your stop positions quite easily. Just some food for thought.

Many of the three phase motors produced today are "inverter" rated and are spec'd to run from 10 to 90 Hz (175-2295 rpm) and are usually attached to a gearbox. In my particular case, a 5:1 gearbox giving 35 to459 rpm final output. Further reduction from the motor pulley to the sewing machine pulley keeps you well above the 10 Hz minimum with plenty of low speed control. Couple that with the VFD setup which allows the top speed to be programmed so that the full range of the pot, in this case foot pedal, is from 0 to programmed top rpm and you have very fine speed control. (The DCservos operate the same way as far as programmed top speed is concerned.)

If you want to control the VFD with a foot pedal rather than from the control panel of the VFD, you can get an inexpensive TIG welder pedal (Ebay) that contains the potentiometer (pot) needed by the VFD for external speed control. I mentioned this in another thread. (Not all TIG pedals have the pot included, some just contain a switch, so you have to be careful when ordering.) Just lock the clutch on the 3-phase clutch-motor and use the foot pedal to regulate speed. The one I'm using on my machine is called a "HITBOX" (www.unitweld.com) and I got it off Ebay. It contains two pots, one the foot pedal operates and another that can be used to limit top speed that is mounted on the box and has a control knob. Just my $.02 @Tigweldor Very neat solution!!

Welcome aboard! Very Nice work!! Interesting wood; type?