I was fortunate to aquire an old shopsmith model 10e (A predecessor to the famous mark 5) with the adapter to use mark 5 accessories. The downside is the unit is underpowered with a 1/2 horsepower motor and limited speed selection with a 3 step pulley. Because the construction of this model lends itself to upgrading with a simple motor and belt drive configuration and because I had a variable speed treadmill motor laying around I thought why not.
Step 1: Overview
The upgrade is broken down into 3 stages.
Stage 1: motor mount and pulley modification
Stage 2: control box and wiring
Stage 3: adding digital tachometer
Step 2: Motor Assembly
The motor mount angle iron is from an old bed frame and were cut to match the size of the original motor. I started by cutting off the extended tang near the front of the motor. Next I used the holes that were left to temporarily mount the new motor base allowing me to mark out the mounting slots. I used a milling machine to cut the slots but it could also be done with a drill and jigsaw. Finally reassemble with the temporary bolts and weld the base to the tabs on the motor, also at this time I installed a brace between the front and rear base which will be used to mount the control box.
Step 3: Motor Cover
Next It's time to install the motor cover which is fabricated from a large tin can. Using a metal nibbler to notch the can to fit around the rear motor mount. The back of the motor is fitted with 2 threaded rod couplers allowing the can to be mounted. Make sure to install a rubber grommet to protect the wiring passing thru the can.
Step 4: Motor Pulley
The original pulley is a multi v type integrated into the flywheel/fan assembly and is installed on the motor shaft with a left hand thread so it self tightens when running. In it's new configuration it will be reversible so there is a potential for the flywheel to unthread from the motor shaft. I was hoping to remove the flywheel and cut a v groove in it in the lathe but it wouldn't budge so I had to go with plan b. Plan b is to bore a v pulley out to fit over the original multi v and install with setscrews. If it ever comes loose in reverse I will drill the original pulley for a setscrew and reinstall with locktight.
Step 5: Control Box
The control box is a 6 x 8 x 4 budd box which is mounted on 2 pieces of 3/8 threaded rod. 3 holes for romex fittings and 1 hole near the threaded rod for the reverse switch and the box is ready to assemble. The circuit board mounts on the bottom of the box leaving just enough room at one end of the box to install the motor filter choke (looks like a transformer). I mounted the reverse switch through the side of the box instead of the top so it can't be switched accidently instead of off/on.
Step 6: Top Cover
The cutout for the tachometer display was done postage stamp style and finished with a file. A new 10k rotary control to replace the long slider style that came with the motor and an on/off switch and the panel is complete.
Step 7: Tachometer
The tachometer is an ebay special and runs about $20 with sensor and free shipping. The 12 volt power supply is something I had kicking around my junk box and there is just enough room to install it to the left of the circuit board. I installed heat shrink tubing over the plug prongs after attaching wiring to them and glued the assembly to the side of the box. I epoxied the sensor magnet to the back edge of the headstock pulley and built a bracket for the sensor from some strap iron. The bracket is attached to the headstock by replacing the motor mount set screw with a bolt and nut. Thread the nut all the way to the bolt head and install in place of set screw. After tightening the bolt to lock the motor mount tighten the nut to clamp the bracket to the headstock. The upper part of the bracket has a cross member that wraps around the edge of the headstock to maintain it's position in relation to the pully. The sensor has to be mounted at an angle to clear the headstock but it works fine.
Step 8: Misc Construction Notes
I wanted the modification to be reversible without leaving holes in the headstock hence fabricating a bracket for the tachometer sensor instead of just installing it in the headstock casting
I opted to use the motor choke in my project but some web plans leave it out. the motor will work wthout it.
After installing the motor the v pulley didn't quite line up with the pulley on the headstock, I could have moved the v pulley farther out on the multi v base but because the motor shaft is thin I wanted it as close to the flywheel/bearing as possible for support. Instead I changed the front slots on the motor base into a T shape allowing me to shift the whole assembly forward for alignment.
Most treadmill controllers have a safety circuit that prevents the treadmill from starting without first turning the control all the way down first. This can be corrected by adding a 1k resistor to the high end of the control for a total of 11k and then adding a 470 mfd 16 volt capacitor between the center of the control to the low end (ground) of the control. The capacitor will hold the center of the control low while charging to allow the motor to start at whatever speed you want. The 1k resistor at the high end prevents the capacitor loading down the supply voltage to the control if you have the control all the way up.
Step 9: Finished
The original step pulley's gave speeds of 850 rpm on low, 1725 rpm on medium and 3450 rpm on high. The new unit goes from 0 to just over 3600 rpm's giving far more fine tuning of speed for all operations without having to change belts and the ability to reverse the direction means all the accessories can be driven from the same end of the machine unlike the mark 5 where some had to go on the other end to run in the right direction. The early test seem very promising and I hope to use it often in other projects.