- Joined
- Oct 13, 2014
- Messages
- 7,282
Hi All,
I recently picked up a nice mid 50's vintage, Boice Crane, 14" vertical bandsaw.
It has a three phase motor so I figured I'd simply throw a VFD on it and be able to get down to metal cutting speeds, wrong!... The motor is rated at 1150 rpm and running it at 15hz only gets the blade down to 1000 FPM, any frequency below that, the torque loss is too great and the blade is easily stalled. That speed is okay for aluminum but still too fast for steel. So I came to the conclusion, I must fit a speed reducer on it to get to a slow enough speed range and have adequate power to cut ferrous metals. Being the saw is direct drive I'll need to move the motor lower in the cabinet and install a shaft and pulley arangement in its place. However, pulleys alone won't get the blade slow enough, it needs a gear reducer as well. That's fortunately been solved by a serendipitous catch of a thread here on HM about a "Pull Gear" 7:1 pulley speed reducer and the chance I was able to grab one off eBay for cheap.
So far, I had to make a custom puller to get the drive wheel off the motor shaft.
I have also purchased flange mount bearings, shaft etc. from Mcmaster Carr and started construction on a mounting bracket (pictures soon).
Right now, My dilemma is the calculating the speed ranges I have a couple of options, I threw together a spreadsheet to help.
The "pull gear"7:1 reducer has three pulleys on it (2.75" 3.75" and 4.75") and can be locked out for a 1:1 ratio, it will be mounted to the motor, the larger pulleys mounted to the drive wheel shaft.
The red line is over the saws original blade speed of 4200 FPM, so I am leaning towards the larger set as it won't over speed and I'll get some very low speeds if needed. I have checked bandsaw speed charts and some go down the 50 FPM for cutting hard steels, has anyone really cut this slow, is it really worth having the capability?
I recently picked up a nice mid 50's vintage, Boice Crane, 14" vertical bandsaw.
It has a three phase motor so I figured I'd simply throw a VFD on it and be able to get down to metal cutting speeds, wrong!... The motor is rated at 1150 rpm and running it at 15hz only gets the blade down to 1000 FPM, any frequency below that, the torque loss is too great and the blade is easily stalled. That speed is okay for aluminum but still too fast for steel. So I came to the conclusion, I must fit a speed reducer on it to get to a slow enough speed range and have adequate power to cut ferrous metals. Being the saw is direct drive I'll need to move the motor lower in the cabinet and install a shaft and pulley arangement in its place. However, pulleys alone won't get the blade slow enough, it needs a gear reducer as well. That's fortunately been solved by a serendipitous catch of a thread here on HM about a "Pull Gear" 7:1 pulley speed reducer and the chance I was able to grab one off eBay for cheap.
So far, I had to make a custom puller to get the drive wheel off the motor shaft.
I have also purchased flange mount bearings, shaft etc. from Mcmaster Carr and started construction on a mounting bracket (pictures soon).
Right now, My dilemma is the calculating the speed ranges I have a couple of options, I threw together a spreadsheet to help.
The "pull gear"7:1 reducer has three pulleys on it (2.75" 3.75" and 4.75") and can be locked out for a 1:1 ratio, it will be mounted to the motor, the larger pulleys mounted to the drive wheel shaft.
The red line is over the saws original blade speed of 4200 FPM, so I am leaning towards the larger set as it won't over speed and I'll get some very low speeds if needed. I have checked bandsaw speed charts and some go down the 50 FPM for cutting hard steels, has anyone really cut this slow, is it really worth having the capability?