When Jerry was faced with a problem of not having drivers with enough current to drive the x-axis of his blackFoot. Jerry had the HobbyCNC 3/4 axis driver board, but the drivers are underpowered for this machine, so Jerry think of an alternative to purchasing new drivers, he solves the problem mechanically.

With lower power comes less torque when you need it. We all know, well if you read this website, that it is possible to use mechanical advantage in many scenarios, and this is one of them. Jerry didn't need fast speeds when cutting, and with the changes that he made, the rapids (where the machine moves from one cutting are to another) are as fast as he needs them to be. The solution he selected is to add a large drive pulley to the main shaft of the x-axis and offset the motor with a smaller drive pulley and use a timing belt between them. He also implements a tensioner on the belt to help keep backlash to a minimum.

Here is a description from Jerry:

Ratio is 4:1 limited by the space inside the gantry for the large gear. I had to put the 1/2" to 1/4" shaft couplers on the lathe and increase the 1/4" end to 3/8" because my pulley was bored for 3/8". The 3/8" mid-shaft shaft is from a piece of rod that was laying around. Bearing behind pulley and tensioner wheels are made of skate bearings (luckily 3/8" hole too). The holes that attach the motor mount to the blackFoot's center support are slotted and allow for coarse belt tension...I think I could just rely on that adjustment and do away with the idler but thought of using a spring to pull the idler in to make it "self-adjusting".

I'm getting a scary amount of torque at 1/8 microstepping with the 300 oz motor and rapids are plenty fast enough. Torque drops a bit at 1/16 microstep but was still very substantial and surely enough to push a router through a deep cut.