Hi All,
I have a Delta DL 40 lathe that stopped turning. As this doesn't do me a lot of good and I would like to fix it. I have found that the motor controller is not working and have not been able to find replacement parts for this old of a lathe. I remember there were some posts about replacing motors and controllers. Does anyone out there have suggestions for a source for motors and controllers that I can use as replacement parts? I have much more mechanical skill than electronic, so I should be able mount a different motor in to my system and I would probably like to put a "slightly" larger motor in if it will fit. Right now the lathe has a 1.5 hp motor and I think 2 hp would probably be OK. The lathe head construction is pretty solid.
Thanks
Ron
I did some searching and found that the lathe is really old, built by Invicta, uses a DC motor that develops about 1.25 HP peak HP (but the actual HP can be considerably less depending on speed and load conditions), and had a horrible reputation for breaking down. There were no AC variable frequency drives back then in 1987 (except for industrial), but this particular lathe utilized tachometer feedback which is rather impressive since DC speed controllers used on woodturning lathes today are a far sight less sophisticated (and less expenisve -- a replacement controller for this puppy went for around $1400).
The only useful information that I found was from the January 2004 Vancouver Woodturners newsletter, page 6. Rather than repeating things, just
Click here for the link to the article. It has some really useful troubleshooting information from a knowledgeable guy. Who knows, your problem might even be the same as his.
Another thing that the author did not mention is that one of the motor brushes might have failed. After all, the motor is really old and brushes do wear out. They are easy to remove and replace and sometimes you can find them at a well stocked hardware store. They come in standard sizes so a dealer that handles motor brushes could help you. Also, if you did not check the internal fuses, that is the obvious first thing to do.
If worst comes to worst, I would go with an AC drive system rather than another DC system. AC systems use three-phase 4-pole induction motors. At the very least, get one that is rated as "Inverter Ready". The cost is tolerable and the only downside is that they can't be operated over base RPM (nominally around 1750 RPM). They also shouldn't be operated at very low RPM for extended periods since the external cooling fan will also be running at the same slow speed.
There are three basic types of variable frequency drives:
- The cheapest is V/Hz (Volts per Hertz). It is essentially open-loop which means the speed regulation is very dependent upon on the load. Also, their sped control is somewhat erratic at the slowest speeds.
- The next step up is the type most commonly known as "sensorless vector" (or variations on that designation). It does not utilize a direct motor speed feedback device, but instead makes a best-guess estimate of speed by the motor parameters that are stored in its memory and sensing the load current and knowing the controller's output voltage and driving frequency. How well they work depends on the vintage and brand. Avoid Yaskawa and Magnatek. I can vouch for the Toshiba "Tosvert" line as being excellent and performing almost as well as the top of the line vector controllers described next. This is the option that I would recommend for best performance for not a great deal over the cheap route.
- The ultimate in variable frequency drives are the true vector drives. These are industrial grade devices (with a matching industrial grade price tag) and use a motor speed feedback device -- most frequently is a 4096-line optical encoder, but they can also use tachometer feedback (now ancient technology). Their strong suit is that when matched with an appropriate motor designed for vector duty, they can operate from zero speed up to as much s 6,000 RPM. They can deliver full torque at zero speed (not particularly useful in woodturning) and full horsepower at maximum RPM (too fast for woodturning). Also, their speed regulation is phenomenal and can be better than ±0.1 RPM across the full load range. The motors that operate with these controllers are specially designed for this service and may operate with no external cooling blower or may have an external blower that is powered by a separate 120v shaded pole fan motor. I mention this option just in case money is no object -- the controllers run around $3000 and the motors also go for about the same price for motors in the 2 - 3 HP range.
