I have used a Singer 15 class domestic treadle for over 40 years - it's precise, fast, slow, and strong, and it sews chiffon at least as well as canvas. I actually think a machine that sews chiffon is superior, of course. Straight stitches in the Forward Direction only. Here it is (excuse the mess)
The irons are 21 inches wide, and the top is 29 inches from the floor. It's not very clear in this photo, but mine has a "big" drive wheel, which makes it faster. I have long ago lost the table-top, and it is set under and on top of a standard kitchen worktop about 8 feet long. This is useful. I have also set it a little further back than is standard, as the extra space in front of the needle is very useful.
And here's an Industrial one - this has a Singer 31k15 in it
Now, you will note that this machine is much bigger - it's not a "heavy-duty" machine, being designed for the tailoring trades, so fast and precise.
It needs a longer treadle base, or your knees hit the left side of the irons, and this is done by adding a spacer top and bottom to a regular set of irons (this one also has a "large" wheel)
Apart from the spacers, and sometimes a set of pieces to raise the top, this is much the same as a domestic treadle. The width of the irons is 26 inches, and the height is still 29 inches. I have had electric (clutch motor) machines - they almost always seem to be taller, and I have been known to cut them down. I have a modern machine (a Juki ) but it still has (and needs) only those ever-so lovely straight stitches. Mind you, it does go backwards. And it's robust in many ways, but not like these two old ladies...
The 31k is for sale, by the way, see here for many other types and shapes of treadles from 1880 onwards
Now, back to the Plates Pages. Ho, hum...