Replies

1. 
   Hokuto | Feb 18, 2011 11:09pm | #1

   I don't know about now, but Makita used to be said to have excellent motors. My only suggestions would be:

   1. Are you running it on a dedicated circuit with the shortest extension cord possible (and that has fully adequate rating)?

   2. Are you pushing the saw too hard?

2. 
   Piffin | Feb 19, 2011 04:50am | #2

   Quickest way I know of to burn out a motor is to use a cord too small or too long, and to push it too hard.

   Keep a sharp blade on it, learn to listen to it, and use a #10 cord

3. 
   toolpouchguy | Feb 19, 2011 08:04am | #3

   you are unlucky or not using right ,I have 3 makita saws and they are daily drivers , still have the 2708 and works perfect still 

   sharp thin blade will make these saws last forever ,and a good quality blade 

4. 
   junkhound | Feb 19, 2011 10:12am | #4

   I have burned up two 10"

   I have burned up two 10" table saws in 8 months

   Old German: "Too soon old, too late schmart !"

   Frenchman:   "Fool me once, shame on you, fool me twice, shame on me."

   Old Italian saying: "Took me 3 times to know where that knot on my forehead was from".

   Polish:  "Dang, on my 3rd saw, must be unlucky"

   I burned out my Sears RAS ripping 2" maple years ago, rewound the motor myself to get twice the real HP output, never had a problem since. 

   Yep, it is a whole 'nuther subject on how to rewind your own motor to get twice the real HP, twice is about the limit without adding an external fan.

1. 
   DanH | Feb 19, 2011 01:55pm | #5

   Yeah, and while you're cutting wood you can roast weenies for your lunch at the same time.  You do need to throw on a little more sunblock in the morning, though.

1. 
   MarkH | Feb 19, 2011 02:55pm | #6

   Yeah, but you don't need a shop heater in the winter anymore.

1. 
   junkhound | Feb 19, 2011 07:15pm | #8

   Seriously, before you guffaw, have you guys ever rewound a motor ? - the commercial stuff leaves the fill factor under 50% for ease of mfg, so a good rewind using 7 smaller wires in-hand can get twice the copper cross section into the same slots, and often a few more turns also - stator actually can run cooler at near twice the HP.   Motor winding costs are a much greater than the steel, so why not have great big punchings and just slop a little bit of wire into the slots?  99.9% of consumers never even look at motor windings. 

   I run a redesigned old Sears  5HP rated 184 frame motor (26A/240V) to run at a full 8 HP (42A) continuously for a 4GPM, 4kpsi+ pressure washer, have not burned it out yet, but have only run it continuously for about 6 hours <G> .

   One of the newer generation aircraft fan motors (non-superconducting) is smaller than a 2# coffee can and has a true shaft HP output of 110 HP. 

   I actually do NOT have a whole spool of HTS. The breakpoint for going to HTS for motors is still around 15,000 HP due to economics of LN2 losses and cost. 

1. 
   DanH | Feb 19, 2011 07:49pm | #10

   When I was a kid I rewound a few.  Very tedious work, and not terribly satisfying results.

   When I took motors in college I learned about (and later largely forgot) all the formulae that go into a good design.  If you just stuff in more wire you're not guaranteed to get a better-performing motor.  In particular you have to size the rotor and stator windings to a correct ratio to get the power curve you desire.  Heavy on the stator and you get lots of torque, only it peaks at 5rpm.  Heavy on the rotor and you get plenty of rpm but you can't spin a child's pinwheel.  (Or maybe the other way around -- it's been 40 years.)

2. 
   MarkH | Feb 19, 2011 08:35pm | #11

   No, I have never rewound a motor, but then, I never burned one out.  It does look a little difficult though.

3. 
   Piffin | Feb 23, 2011 09:40pm | #14

   "No, I have never rewound a

   "No, I have never rewound a motor, but then, I never burned one out.  It does look a little difficult though."

   Oh take my word for it - it can be very easy to burn one out. Not difficult at all!

   LOL

2. 
   MarkH | Feb 19, 2011 02:58pm | #7

   And Junkhound probably bought a whole spool of surplus superconducting motor wire for 12 cents.

1. 
   Earl Smith | Feb 19, 2011 07:37pm | #9

   Wire Motor instructions?

   Does anyone have instructions of how to properly rewind a motor. I'd love to try this..

   Earl

1. 
   junkhound | Feb 19, 2011 09:10pm | #12

   instructions of how to properly rewind a motor

   I will not try to go into different winding techniques, but it would be best to simply learn at first by rewinding the same as the existing burnt out motor. 

   A 3600 RPM or 2 pole single phase shaded pole motor is very easy way to start (no start winding, start torque from a 'short' around part of the magnetics);  however, a cap start or split phase motor is not too hard either.  For a first try, a 4 pole 1725 rpm motor is more than twice the work.

   Cut off the existing burnt out winding being careful to count the turns for each set of wire bundles and try to be able to re-assemble the shape in the plywood step below.  Measure the wire gauge. You will only need to wind 2 coils for the main winding (and 2 more for the start winding if not a shaded pole motor) .

   My method is exceedingly simple for a 'just replacement' winding. 

   Layout the cutoff bad winding on a piece of plywood, and put a nail at the corner of each loop you removed.  Wind new wire around those nails.  I like to use Class H or better magnet wire. 

   Make sure the paper or nomex slot insulation is in place, take your new winding off the piece of plywood and with a popsicle stick or similar push the wires into the appropriate slots (for newbies, best to take a few pix of the burntout motor winding so you know what goes where). Put the top slot paper/nomex strips (have even seen wood used) back in place or make new and install.

   You may have to buy some insulation varnish - look at Mouser or where ever you buy magnet wire.  If you want to keep your first try low cost, simple polyurethane will work as varnish but is not a high temperature varnish.  

   For simple DIY, simply drip the varnish (you could dip or vacuum impregnate also, but that entails more equipment) onto the coil until is looks like it has penetrated into all the coils.  Then bake in an oven (I have an old kitchen range in the shop for just this type thing)

   Wire it up and away you go.  Thing can get lots more complicated from this point, let me know if your first effort is a success.

   BTW, rewinding a dc armature is not even worth my while as relaxation......<G>

   Good luck.

2. 
   Earl Smith | Feb 20, 2011 12:09pm | #13

   How to

   Thanks for taking the time to put up that info. This is great.

   Earl