Shopsmith Forums

Posting a fresh thread because this is spread over several older ones. I have a ShopSmith 1-1/8 HP 230 V / 50 Hz motor (factory sticker over the nameplate, serial SS-115073), running in Australia. Headstock is currently open (changing all bearings, cleaning, plus a failed switch), so I can measure or photograph anything that helps.

Mostly I just want to understand my own machine properly before I put it back together, and know what I'd be up against if I ever need to import US parts. I've been reading the old threads on this, the 50 cycle vs 60 cycle thread with rayjack and JPG's comments in 220 VAC motor questions, and honestly I've come away unsure what I actually have.

I read JPG's posts about the poly-V pulley ribs and the idler/main ratio. The OD across the rib tips of my main-shaft poly-V pulley is 48.56 mm (~1.91") (pictured). JPG eyeballed about 1-3/4" for the US version, so I expected mine to be smaller, but it's the opposite. Now I'm more confused than ever.

Could someone help me understand:

1. What's actually difference in the drivetrain between a 50 Hz and a US machine? Is it the drive sleeve / poly-V pulley, and is it the ratio that matters rather than absolute diameters?
2. From the photo, am I measuring the right part, and what would you expect the correct figures to be on a 50 Hz drive sleeve?
3. The motor is also stamped 1/2-hour duty rather than continuous. Is that a real thermal limit of the 50 Hz winding, or just a conservative export rating? My use will be light (drill press, bandsaw resawing, occasional table saw, never used a lathe, no planer or jointer).
4. I'm also likely to do the 4" Bill Mayo louvered rear motor-pan mod (the covers are sold cheaply as boat vents), as he said it helped a lot with heat.

Thanks, any guidance appreciated.

I can only make "educated" guesses.

First guess is that the "1/2" hr duty rating is the result of the motor being designed as 60 Hz continuous duty but being used at 50 Hz.

As for the pully od, the meaningful (non-measurable) dimension is the pitch diameter of the poly-v pulley. The od may indicate a difference. Since you actually measured yours, I presume it is more accurate than my 'estimation'. I will measure one of mine when I get a chance to do so.

Thank You for bringing this question back to the top. It has always been a question in my 'mind' regarding the pulley(s) used in 50 Hz models.

FWIW the control sheave pulley pitch diameter is relevant as well. So I will measure both a drive sleeve pulley od and a control sheave pulley od.

A tach reading of yours actually running would be the quickest method of answering the resultant speed dial vs actual rpm question.

My working theory is that Shopsmith made no mechanical changes to the headstock to accommodate the slower 50 Hz motor and instead published a 50 Hz Speed Chart remapping the letters on the speed dial to different RPM. For example I have a late 80's manual with a Speed Chart on page 52A for "115 and 230 v., 60 hz Domestic and Canadian motors" and another on page 52B for "230 v., 50/60 hz. Motor." Under General Sawing (TS) the Hardwood speed is "R (3500 RPM)" for the 60 Hz page and "U (3500 RPM)" on the 50 Hz page.

I measured 48.6 mm on a sample where you measured 48.56 mm. I would call that the same as it pertains to this discussion. It is, IIUC, the ratio of the Poly V pulleys that is critical. It allows for the machine to simultaneously be set up for sawing and jointing at the correct speed for each.

FWIW I took my Greenie with me to Germany and used it for several years on 50 Hz power without problems. I was aware of the risks, but also had access to a replacement motor if I needed it. (IIRC it was listed as 230 V 50/60 Hz and offered 1-1/8 HPO versus the 3/4 HP Greenie motor.) So essentially I ignored the risk. If I was using it in your circumstances where it is somewhat less clear where I'd get a motor if I burned mine up, I think I would put a thermocouple on the top of the motor case and monitor temperature any time I was concerned. It would be impractical to adhere to a 1/2 hour duty cycle that is based on the motor seeing maximum load all the time.

- David

That makes a LOT of sense. I think it sums it all up. Critical is the manual charts for 50 Hz use.

The idler/main shaft ratio is 1.6.

I am gonna stop stressing over this!

This is all terribly interesting, thankyou all! Pulling some threads together...

- JPG you noted back in Sept 2009 that the US 60Hz drive sleeve was part 518145 and you'd spotted a different part number for the 240V 50Hz one in the catalogue (though you didn't quote it).
- Rayjack in the same thread measured his UK 50Hz upper poly-V at 1.5" OD with a 1.29:1 ratio, vs the US 1.75" and 1.6:1.
- And DLB you've now measured 48.6mm on a US sample, which is dead-on with mine.

So it really does look like Shopsmith ran two different solutions for 50Hz markets over time: a custom smaller pulley for some (Rayjack's UK machine), and "same drivetrain + standard chart, just runs slower" for others (mine seems to fit this category).

My unit came with an operations chart showing R for General Sawing, matching the 60Hz convention rather than 50Hz like my motor. I don't know if it's original to the machine since I didn't buy it new, but if it is, it suggests AU 50Hz units shipped with the standard US chart and drive sleeve, and owners were just expected to wear the speed reduction.

A couple of things I'd love to track down if anyone has them:

- The 50Hz drive sleeve part number JPG saw in the catalogue
- A scan of an actual 50Hz-specific speed chart so I can see what each letter maps to

My machine is in pieces, and I'm waiting on a lot of stuff from the US (4 week turnaround), but I do plan to get a photo tachometer and post measured RPM at each dial letter once she's back together, which should at least settle it for my specific machine.

Also worth mentioning: I noticed Mrehder's motor over in the "Motor clicks under load" thread had the same 1/2 HR DUTY stamp as mine, so it does seem to be a real export rating - consistent with JPG's earlier guess that it's a 60Hz design derated for 50Hz thermal headroom.

As far as I know it's worked fine for 43 years, so I'm hoping I can get it running again and maybe it can last a few more decades. If not, my options aren't great. Shopsmith discontinued the 513968 dual-rated 50/60Hz motor years ago per Stephen Draper, so it'd be a used motor on eBay, a Bill Mayo rebuild, or going all in on a PowerPro (I imagine the bill would make my eyes water).

One thing that need to be mentioned here is that none of this is precise. A lot of variation is possible with the normal hardware variations likely.

Oh how quickly we forget!

2009! Wish I had revealed that 50 Hz part # also!