Horizontal Band Saw Restoration - Zapins

While you've doubled the torque figure with the gearbox, you've also halved the RPM so the HP formula gives the same 1HP.

 

I'm trying to figure out if it would make sense for upgrading motors on my machinery. The goal would be to have a 2 hp 1725 rpm motor on all the machines but they are rare and expensive motors. I see 1 hp 3450 rpm frequently for cheap. Is there any utility in adding a 2:1 gear reducer box onto the 1 hp to make it act like a 2 hp in that situation? I think it makes sense you lose half the speed but gain twice the torque.

I'm not sure about the horse power part but I think it makes sense?

 

FWIW, I’ve run a 1hp motor on mine for 20 yrs. I never felt a need for more power.

Denis

 

My vertical band saw sometimes catches and stalls with a 1.5 hp motor. But I'd like to upgrade other machines around my shop in the future like my sander and finding an economical way to do it would be good. I see 1 hp 3450 rpm motors all the time at my scrap yard but rarely higher hp motors.

 

Your limiting factor is the saw blade itself, too high a feed and it just rips off teeth from the blade. I use a Pehaka saw to cut two aluminium ingots at once and it still stalls if the feed is too fast, so I back off the feed and use it like that. The reason the slower motors are more expensive is they need a physically bigger motor frame to have the same horsepower as a smaller motor that runs faster due to magnetic saturation and other physics constraints. That's why a 2Hp motor becomes a 1Hp motor when you halve the RPM with an inverter drive. You could also get your 2Hp from a 230 Volt, 4 or 5Hp three phase 3450 RPM motor with a cheap single phase inverter drive set to 1725 RPM.

 

I always wonder why that was... Thanks, good stuff!

 

Here's a photo of the data plate for a four speed Wadkin woodworking machine of some description made well before inverter drives existed, it's about 2 feet long and 18 inches diameter. You can see with each speed reduction the horsepower drops accordingly so even though it happily puts out 7.5 Horsepower at 1420 RPM (4 poles) by 720 RPM, it's down to 3.75Hp (8 poles) and by 470 RPM it's 2.5HP (12 poles). This is due to the magnetic steel limits before saturating at a given RPM.

 

The single pole pair motor turns twice as fast with half the torque as the equivelent 4 pole pair motor. So the 2:1 reducer by halving RPM and doubling torque just makes them roughly equal at the output shaft.

Edit. Oops, sorry, already answered.

 

When you lower the frequency in a inverter drive for a motor that normally runs at 50Hz the voltage has to drop otherwise it will overheat and when a motor runs at a lower voltage it gives less power. Running a 50Hz motor at 100Hz it will not overheat but will not give name plate power.

 

If you could run a motor at half frequency without the windings going into magnetic saturation and needing to throttle back, the horsepower halves because the RPM has halved and you have halved the rate at which the work in being done. Even with an internal combustion motor if you increase the RPM you increase the horsepower, i.e. the rate of doing work. That was one of the reasons the Napier Sabre aero engine was able to exceed one horsepower per cubic inch, by revving higher with it's sleeve valves.

 

Worked on making a replacement blade guard. Took quite a while to cut out all the bits and pieces and salvage the hinges from old guard. I think it turned out well. The new guard is 16 gauge. The old floppy one is probably 20-22 gauge. In the process of spray painting it now.

 

Metal cover is done and painted (pics tomorrow). I pulled a spare 3/4 hp motor apart and tubed it up and repainted it (pics tomorrow). I also bought some 75-140 wt royal purple gear oil. Apparently it is safe for brass gears so I can top up the gear box.

I'm finishing up fabbing a new pulley cover and then will finalize the stand. Then its done.

 

Oooh shiny motor!
Nice work Zapins. Looking forward to the reveal.

 

Hehe. I redid the motor colors

I made a new pulley cover but the hinges are a bit wonky. Will have to have a think about it.

 

Even better!

 

Looks nice, Zap.

Earlier there was some chatter about the adequacy of a 3/4hp motor for a metal-cutting bandsaw. I thought it might be useful to point out the a brand new Ellis 1200 band saw has a 3/4hp motor. Given that Ellis is a respected maker of quality saws, that should provide some reassurance about the adequacy of this shiny copper-colored motor.




Looks good.

Denis

 

Finished up most of the things on the bandsaw. Its fairly well calibrated already. It cuts 90.1 degree angle when set to 90 in the direction the blade travels but as the cut gets deeper it is cutting a 90.7 degree angle so I'll have to fiddle with it and see if I can get it aligned better.

I still need to make a few extras for it to make it more usable (i.e. new handles and knobs for the vice, and a quick stop for repeat cuts of the same length, and vice upgrades).

Particularly happy about how the pulley cover came out since I had to completely fab it from scratch as the original was missing.

 

I was just thinking some adjustable height stands with rollers on top would come in handy for the bandsaw and the planer once it's finished so you can easily feed in full lengths of steel or wood into the machines.

 

A buddy just moved out of his house and left one of those roller stands for me. I'm excited to try it.

I also built the band saw so it is exactly the same height as my work bench. So I can use the table to rest long pieces on as well if the roller doesn't work out.

 

Finished one of the replacement hand bolt things for the vice. Nearly done with a second one for the angle selector jaw. Will need to make a little T shaped piece to act as the nut to slide inside the channel on the table. That way I don't have to hold my hand under the band saw and try hold onto the nut while tightening the top piece.

Working on another bit too for the vice jaw.