I think Economizer is a name used by Torwell for their spreaders. Good units and the only ones I know of that allow adjustment of the spinner speed relative to the speed of the drag chain. As far as I know they all still have that feature, the Torwell I was involved with was an oldie.
In gas engine vee boxes if I could get a Torwell in stainless with a Honda engine I'd buy one in a heartbeat. Nearest dealer for me is over an hour away though.
Sorry, Alan, I have to disagree with you. I had a Torwell, it gave me nothing but trouble and was part of the reason I bought my 550.
The model you talk about is no longer in production, it used a wheel off the spinner to drive the conveyor and was adjustable for speed depending on where you placed the pick up wheel. That system has been replaced with a 90 degree gear box with set speeds.
The Torwell also uses unservicable bushings in the shafts that transfer energy from the gear box to the conveyor chain, the only way to keep them lubricated is healthy doses of WD40 or similar product.
The spinner bearing is nearly impossible to reach to grease, and when you finally get it, your covered with the de-icing material, it requires you to lay under the spinner to get grease in it.
I had a terrible time keeping all the wiring working, I would replace the plugs between the truck and sander annually, but still have to work on them throughout the season. Mine had a Briggs motor, but the motor itself didn't give me much trouble, it was the wiring.
I don't know how these problems would compare to other brands, I think any motor driven spreader would have similar wiring problems. I'd look at either hydro or electric motor units for more reliability.
The Torwell did seem to be well built structurally, but those servicing issues really bothered me.
I was just in Vermont for some snowboarding, and these spreaders were apparently the top choice for the Rutland area. I saw many of them & got to watch a couple running. They seemed like decent units from these observations, without touching them or running them myself