Certainly everything is in the planning stage at this time. I saw a post where somebody had converted an X3 to a 2hp motor that weighed 56 lbs. While I have sent a private mail to him, I see from the stats that he hasn't been online since June. Doing some mental exercises and web browsing I have come up with a tentative plan. In this case I am looking at using 65 tooth Timing belt that measures to have 4 teeth per inch that comes with the X3. In this case I am looking at having a three stage spindle timing pulley of 51, 34, and 28 teeth. For the motor timing pulley having 14, 34 and 39 teeth. While the target ratios were 1000:3600, 3600:3600 and 5000:3600 based on the planned top speed in each range the actual choices were made to keep the minimum belt length approximately the same and approximately 2 inches shorter than the measured belt length. So the actual ratios are 988:3600, 3600:3600 and 5014:3600. I plan on cutting these myself. Since my stepper driven rotary table gives me a resolution of .002 Degrees I think I can come up with evenly spaced teeth.
I am looking at using the Hitachi X200-015NFU as the driver and either the North American PE145TC-2-4 or NA145TC-2-4 data sheets are here
http://www.naemotors.com/premium/PE145TC-2-4.pdf and
http://www.naemotors.com/newt/na1800c/NA145TC-2-4.pdf
I would prefer the PE version as it is 6 pounds lighter and has better Inverter specs but I still don't have a price for it. The NA version has a price of $189.00 at
http://www.e-motorsonline.com/product_ACM03786.html
and as that appears to be in budget and priced in the same range as the Grizzley replacement 3/4 hp motor, I don't feel further design work will be wasted. Dimensions indicate that these motors will fit between the spindle and column with room for belt adjustment.
Thus my current plans are make the timing pulleys initially for the stock DC motor as its shaft is smaller and when upgrading to one of these it would just require re-boring and keying the motor pulley. I will build the motor mount to accommodate all three motors.
Then when either the DC motor fails or I get tired of the DC Motors performance I will upgrade to one of the 3 phase motors.
The initial results should give equal or greater performance at low speed as belts are supposed to be more efficient than gears, and give me the desired higher spindle speeds for cutting aluminum.
It also has the added benefit up being much quieter.
Hubert