Compressor motor upgrade question

admin

I'm working towards a compressor upgrade. I'm going to be using this for both my metalworking and woodworking activities, so I want it to be able to embrace the various needs I have for it - spraying finishes, sandblasting, air nailers, angle grinder, use with my plasma cutter, etc.I've purchased a bigger compressor head, which will upgrade me from the ~2 hp ~6 cfm @ 90 psi direct drive all-in-one unit to an 18.5 cfm @ 100 psi. I need to pair the new head with a 5 hp motor and have a possible prospect for that in my sights. I just need some help determining if this motor would do for this application.Here's the specs off the motor plate:Kohlbach Single Phase Induction MotorModel 4012-2824-613E FR 56H HP 5.0 V 208-230 A 22.6-20.7 Code H RPM 3460 Design L SF 1.0 Time CONT Ins F Amb 40*From this, it looks to be a fairly good quality motor. However, if I interpret this correctly it's a continuous-duty rated motor and wonder if a motor of these specs would be appropriate to the high initial torque and repetitive start cycling that occurs with compressor service.Any thoughts are appreciated!Before you criticize someone, walk a mile in their shoes. That way, when you criticize them, you're a mile away. And you have their shoes.Roland
Reply:I generally prefer a capacitor-start or for bigger motors like this, a cap-start, cap-run one. The 56 frame size also seems a bit small for a 5 hp but the current draw is correct for that rating. Are you getting a good deal on a used motor? A general home-garage unit might run a few minutes every ten or twenty, but for sandblasting, or spray painting, a compressor can run more than fifty percent of the time; starting and stopping that often would be rough on even a better motor. For this, you can use a Constant Speed Unloader which exhausts the pump outlet to the atmosphere (after isolating the tank pressure) while letting the motor and pump continue to run. In any case, you should have this motor begin with the pump unloaded (outlet not pressurized). If it's a good enough deal, use it.
Reply:Most air compressors use a 1750 rpm motor. So expect to have to have twice the amout of speed reduction between the motor and compressor. Your compressor probably came with a flywheel/pulley so you might not be able to reach that much reduction without resorting to use a jackshaft and more pulleys. Did your compressor come with a spec sheet telling what rpm it should turn?Tough as nails and damn near as smart
Reply:Good point tresi; how'd I miss that one?
Reply:Kohlbach? never heard of that one.Baldor 1750 rpm for sure.. I've bought a couple from these guys. Here's one...http://cgi.ebay.com/NEW-5-HP-BALDOR-...QQcmdZViewItem