View Full Version : Motor Has No Torque, What is Up?
geopicker
11-27-2008, 09:33 AM
All,
I just bought a very used Shopsmith Marv VII. I think it is about a 1963. All the mechanical parts work freely but the motor is a bit fishy. I have verified that all bearings in the mechanical part of the Shopsmith work freely. But when the motor is all connected to the unit it turns but does not seem to have any torque. It turns slowly for a bit if you give it a turn then stops in a minute and clicks until you turn it off. At this point the motor is hot. When the motor is out of the unit it turns really fast. I have taken the motor apart and do not see any obvious problems.
So, What could be the problem? Is it the motor? Should I have it looked at or just replaced?
Many Questions,
Mike
8iowa
11-27-2008, 09:55 AM
I don't have a MK VII, but I understand that the motor is reversable, probably having two starting windings. It would seem that one or both of the start windings are not being energized, giving the motor very little torque with which to come up to speed.
There may also be a starting capacitor, which could be bad. Fortunately, this is an induction motor and almost any capable electric motor shop can fix your problem.
dusty
11-27-2008, 10:12 AM
No, don't replace the motor yet unless you have money to burn.
Low torgue at startup is often the result of a defective start capacitor. I know nothing about this particular motor but if it has a start capacitor I would begin by checking that.
If you have no electrical skills take it to a motor shop and have it tested.
The startup capacitor operates, typically, only as the motor comes up to a predetermined speed. Once that rate of rotation has been achieved, a centifical switch opens to disconnect the startup capacitor.
Don't keep trying to get it started without a fix having been employed. To do so could result in heat damage (open winding).
Have you cleaned and lubed the mk7?
mikemarkvii
11-27-2008, 02:55 PM
hi mike;
welcome to the forum and congrats on buying a m7, which is imho a step up from the m5 500.
the first thing i would do is disconnect all belts and test the motor only. if in fact the motor is at fault, take it to a good motor shop. have it checked out, new cap if needed, new bearings [likely needed], install a 12 gauge elec cord[buy an extension cord and cut the end off]
next check all connections to the switch, as i had one that was a bit loose and would at times arc.
and of course, lube and wax everything, even to the point of disassemblying, and cleaning everything you are comfortable with. if you are ok with bicycle maintance, a shopsmith is not much harder.
goodluck, i think you will be happy with your machine, i know i am with mine. :) feel free to send to pm if you need to.
mike
geopicker
11-28-2008, 09:50 AM
Guys, Thanks for the tips. I think I will take it into a shop and have it looked at. Maybe it is the capacitor. I have taken the motor all apart and do not see anything else odd or burnt.
Just so I know, what is the cost of a replacement motor?
Mike
Just so I know, what is the cost of a replacement motor?
Mike
ABOUT $300.00. Last time the shop told them to buy the OEM.
billmayo
11-28-2008, 05:00 PM
All the Mark VIIs I have serviced had bad switches. The start windings are connected through the switch (not to the input power) and was not making contact. I replaced the Mark VII switches with an ON/OFF switch and a FORWARD/REVERSE switch which took care of each problem. One of the forum guys named Gary furnished me with the wiring hookup which helped me solved my Mark VII problems. I have the wiring hookup that Gary gave me if anyone needs it.