Shopsmith Forums

Hi all, new to the forum, hoping to tap into the wealth of knowledge so I can make some boards into wood chips. I’m an American living in Britain, grandpa had a mk 5, dad had a mk 5… I’m hoping to get one eventually. What I do have is a stand alone 12” pro planer and I’d like to get it back in action so I can make quicker work of things than the old Stanley no 5.

Acquired the planer from a guy in Manchester. He said it had a switch problem and it wasn’t running. After cleaning it up I looked into the on/off switch. Except for needing a new spring for the lockout tab it was all fine. Plugged it in and still no turny turny… checked the fuse in the plug (UK plugs have them) and found a dead 3A fuse… usually house mains (240v single phase) have 13A fuses so replaced that. Turned on and planed a test board. No problem but the feed roller was slipping.

Tried it again after cleaning out the rollers and next test blew the fuse. Motor acted like it was stuck so I checked the power train and everything seems fine. Motor spins well, belts and pulleys are ok, cutter head is smooth no obstructions… It’s eaten a few fuses now and best I can figure is the start capacitor is not correct and can’t get the motor out of its locked rotor resting state. Tried calculating required capacitance but not sure I’m getting it right.

Can anybody check their start capacitor or calculate what I need? It has a 110V 704mf start capacitor which seems odd on a 240V motor. Maybe it just needs longer between duty cycles… I’m at a loss. Attached motor plate and capacitor pics if that helps.

Thanks in advance!

Internally the motor has two run windings. They are connected in parallel for 115v use. For 230v use they are connected in series. The start circuitry is connected across one of the run windings termination. This creates a 115v scenario for the start circuit. It appears yours is not reconfigurable for the lower voltage, but all above still applies(the run windings are connected in series...).


Locked rotor resting state????

I have a hunch that the fuse in the power plug may be of the fast-blow variety. Induction motors have huge inrush currents at startup, until they get up to speed and the motor’s back EMF counterbalances the line voltage. So your 9 Amp full-load motor could easily have a 40A locked-rotor (startup) current, which would be plenty to blow a 9A fast-blow fuse.

If you want to keep a dedicated inline fuse, it should be of the time-delay, aka Slo-Blo, type. Here in the States, we’d normally just rely on the house branch-circuit breakers for protection in this case. The modern ones are pretty much all “inverse time” breakers, which have tripping characteristics similar to a time-delay fuse.

Thanks, I will have to digest and do some reading since the last electrical engineering course I took was about 20 years ago. Memory and terminology on the theory and application of electric motors has probably degraded quite alot since then. What I mean by "locked rotor resting state" is the tendency for a rotor to resist spinning up when first switched on. Probably not the right term so please correct as necessary.

From memory a single phase induction motor uses the reversal of the current direction in a single A/C stator winding to flip the field poles and pull the rotor through 180* before flipping again to keep it chasing the field. If there are two windings in parallel at 115V then the start capacitor being a 110V in a 240V motor may not be the problem. Just struck me as very odd that the capacitor wouldn't match to kick the motor to life. Will have to check on a capacitor test procedure using a multimeter to find out if its good or not. Also if anybody does have the specs on a 240V Euro motor I'd appreciate knowing that the one fitted is correct.

I'll look into the fast blow vs slow blow fuses. Only see the standardized ones for sale for home fuseboxes. The wiring in the house is 1980's vintage so I would have thought the design was compatible with the age of the machine... ie no GFCI or RCD tripping like will be in a modern home system. Perhaps the fuses available now are faster reacting than in the past. I do want to keep the plug fuse to keep the designed protections in place and not push the problem up the line where the home's wiring will have to deal with it.