FILENAMES: motdrv1.jpg motdrv2.jpg motdrv3.jpg motdrv4.jpg motdrv5.jpg DESCRIPTION: These are pictures of a home built, independent power feed for a lathe as posted by Terry Nelson . Terry provided the following description: ==================================================================== Here is a power feed drive I added to my lathe. It consists of a DC motor attached to the end of the feed rod. The motor is a 90V, 83 RPM, 47 lb in, 0.9 amp, 1/12 hp gear motor. The motor speed is controlled by a SCR based speed controller. The picture files of it are motdrv1.jpg to motdrv5.jpg motdrv1.jpg shows the complete unit on the lathe. The speed controller sits in front in an outlet box. The knob on front is of course the speed, and the switch is a three position toggle switch. Swithed to the left feed towards the headstock, or towards the spindle center. The center is off. Towards the right feeds toward the tailstock or away from the spindle center. motdrv2.jpg is just another view of the completed unit. motdrv3.jpg has the speed controller removed for a better view of the motor mounting and coupling system. motdrv4.jpg shows the motor removed and clamped near the feed rod to show the coupler. The feed rod was modified by drilling a hole in the end of the shaft. (3/8 I think) and glueing an extention plug into it with Loctite 680. The extention has a cross drilled hold through it which mates with the female portion of the coupler. The coupler has the locking pin hanging out of it in this picture. It is bent to alow it to spin without hitting the top motor mount bracket. For those of you worried about gluing things like this together, Loctite 680 is specialy made for cylindrical part bonding. It's NOT coming out, trust me. :) motdrv5.jpg is the motor controller schematic. AT THIS POINT ALL THE USUAL DISCLAIMERS APPLY. I IN KNOW WAY CLAIM THIS CIRCUIT IS SAFE OR WILL WORK. USE IT AT YOUR OWN RISK. I AM NOT RESPONSIBLE IN ANY WAY FOR ANY ELECTROSHOCK TREATMENT YOU GIVE YOURSELF BASED ON THIS CIRCUIT. IF YOU DON'T KNOW WHAT YOU ARE DOING, THEN YOU SHOULDN'T BE DOING IT. YOU MUST GROUND THE MOTOR CASE FOR SAFETEY. YOU ALSO MUST USE A FUSE. OK, back to more fun stuff. This is a fairly typical textbook speed controller. The SCR MUST BE A SENSITIVE GATE STYLE TO WORK PROPERLY IN THIS CIRCUIT. A regular SCR will need different value components based on its driver characteristics. Diodes D1 and D2 are 1N4000x series parts. I don't recall the number for the 400 V parts. The 0.1 uF capacitor should be good for 200 volts. The 8.2K resistor helps with low speed control for varying load conditions. You may need to set it for your motor. The range will probably be from 0 to 10K ohms. The 5K sets the maximum motor speed and should not be any lower than 2K. The 560K sets the lower speed limit. The 100 pot does not give a linear speed control. You have to get MUCH fancier in terms of controllers to do that. This is a quick, cheap controller. It should work OK for 90 to 120 V DC motors. You can even put in a higher current SCR for bigger motors as long as the voltage range is OK. For those of you with 60V servo motors, this isn't the answer, sorry. I fused mine with a 1.1 A slow blow fuse. If I stall the motor at any of the higher speeds it will blow the fuse. Probably a good test to do. Either a worm gear drive motor, planetary gear head, external gear, or pully system should be suitable for this type of drive. The speeds an torque requirements will vary depending on the gearing in your carriage. I personally would prefer a little higher speed for mine than my current motor gives. Also, while my current motor is a 90V motor, the speed controller used actually runs it at a higher top voltage. (Mine is 128 V measured at the motor) This isn't as evil as it sounds. It means it will run faster (good for me anyway), and possibly hotter. However the motor I have is ratedat 100% duty cycle for full load at an ambient temperature far greater than I'll ever be working in. Thus its not a problem. Another thing I have done with mine is set up a 240 to 24 volt transformer in the switchbox of my lathe. Whenever the lathe is running the transformer is powered. The 24 vac goes into an outlet box mounted on the lathe. In the box is a contactor used to switch two 120 VAC outlets in the box. The motor controller is plugged into this, thus it only runs when the lathe is on. The other outlet is ready for a coolant pump if I ever get that carried away. There are several advantages to a variable speed motor drive on a lathe. One obvious one is you can change the feed during a cut. Its simple to change the feed direction. Some lathes have a know to do this during a cut anyway, but many do not. Generally there is some type of lever controlling the drive from the spindle to the quick change gear box. This of course is set to the neutral position. This is one of the biggest features of this mod. Getting rid of the end gear noise at high spindle speeds. You also must have a disconect lever between the feed rod and the quick change gear box. SOME lathes do not have this. If not you must find a way to do this. This system isnt going to have enough oomphf to drive the gear box in reverse. My system also can quickly be converted back to normal operation by simply pulling the drive pin, and engaging a few levers. For low speed heavy cuts I actually prefer the gear box. Since the coupling is lost between the spindle with the DC drive, if the spindle slows, and the feed rate doesn't, the feed effectively increases. This of course slows the spindle more, which increases the feed more, .... well, you get the picture by now I hope. :) The next thing I would like to add to mine is an interlock system so the gear box and DC drive cannot both be hooked up at the same time. Its not problem if the DC tries to drive the gear box, it stall and blows the fuse. However if the spindle drives the gear box and the feed rod is stuck trying to drive the DC motor through its gearbox things get ugly. The 1.5 hp main motor is NOT going to stall. That means the gearbox is going to move or break. I actually did this once, the quick change gear box sprung away from the lathe bed as the end gear rolled over a tooth. Didn't end up hurting anything but my neurons sure went berzerk as I saw it happen. If you have any questions feel free to email me at tmnelson@micron.net Terry