Electronic speed control vs gearing/belting

[serriadh]

I've been looking at the reasonably nice looking range of lathes that Weiss Machinery make. They're available in the UK as the Warco WM-series variable speed lathes, or the DB-xV lathes from Chester.

Geared or changeable-belt driven lathes can have a big mechanical advantage at low speeds so they'll have lots of torque when cutting threads or turning big objects or bits of steel or whatever. These lathes have no such mechanisms and make do with purely electronic speed control. They do have noticably heftier motors (30-90% more horsepower compared to similar sized belted/geared machines), but is it enough when running at these low speeds?

I think the Sieg C4 and one of the 10x22 models also have variable speed BLDC motors. If anyone has any experience with these I'd be interested to hear about it!

[TroyO]

I'm not familiar with those particular implimentations, but I did do a variable speed mod to my 8x14 and love it!

The slowest speed I had with belt-changes was like 650 though, so it made threading even in low gear a hairy experience.

I did notice on my last project (In the thread "What the chuck?") that I was having some torque problems on mine. I'm not sure I wouldn't have had that problem with the stock motor as well, so it may not be an issue overall.

Really, the best of both worlds would be a couple of belt ranges (to get the mechanical advantage) and a variable speed motor.

I'm considering re-doing my setup to work that way. In general, the variable speed is very nice. Having a really low "threading" range with lot of torque and a "normal" range for turning would be just about perfect.

Generally, I'd think it would be easier/cheaper to upgrade an electronic speed control setup to have a handfull of mechanical ranges than vice-versa.

[serriadh]

Generally, I'd think it would be easier/cheaper to upgrade an electronic speed control setup to have a handfull of mechanical ranges than vice-versa.

Really? I'd have thought that nailing a brushless or three-phase motor onto an existing lathe with mechanical speed control would be relatively straightforward, as it avoids having to obtain and install your own belt drives for other speeds. You've then got some measure of 'back gearing' to allow for low speed, high torque operations for hard or large workpieces or threading.

Having a low end of 600rpm seems a bit swift and unforgiving!

[TroyO]

"Having a low end of 600rpm seems a bit swift and unforgiving!"

Especially if you are a newb like me and had never done it before...ever. LOL

Doing a VS upgrade is pretty straight forward, BUT... to upgrade an existing VS setup seems dead easy too... machine a couple of pulleys and bolt them on. You already have a lathe at that point, so pulleys should be no problem. :-) (And dirt cheap.)

To me, knocking up or modifying a couple of pulleys (And maybe a belt tensioner) seems easier than mounting a new motor, wiring the whole thing up, finding places for the speed control, etc. And did I mention cheap? LOL.

[TroyO]

Oppss... just looked at the specs on my machine and realied it was 125 RPM, not 650 as the low end. LOL... either way, it's faster than I want.

Anyway, in my case I think I am going to reconfigure some things to give me some more speed options... I think I can do it without many actual changes, just a couple of parts swaps.

I'll let you know what I think of the "feel" of it when I get done.

[kawazuki]

I have a Chester Comet / C4 and although I haven't really tested its low down performance its lowest rpm is about 90 and if taking a particularly heavy cut that starts to bog the motor down, the electronics instantly up's the power to keep the rpm's stable. I'm sure it'd shred the drive belt before stalling!
I'd actually like to gear it down to a 40-50rpm minimum and sacrifice a bit of the 2500 rpm top end which I find scary fast but the belt runs are a bit tight so will require some thought!