No that's correct horsepower does not affect speed unless you look at it from the aspect that a high horsepower unit does not stall, or jam as frequently (which can slow you down, hehe). But, yes horsepower does make a difference in overheating and thermal cutout. Especially, as you say, with something like watermelon rinds. I have occasinally had a half horsepower unit cutout and need to let it cool for a few minutes when putting in a sink full of rinds.
I learned that just being patient solves the problem with the GE series. For example you put in once corn cob, then wait about twenty seconds, then put in another, etc. Straight feed in of bos or watermelon rinds, with no break, will cause overheating. It's grinding speed is so fast it will keep up with you, but the poor motor gets hot from working so hard.
I don't recall ever having one of my 1 horsepower units do this on rinds. All of my 1 hp units can grind watermelon rinds as fast as they are inserted (one at a time, yet continuously).
In the nineties, when GE was contracting Annaheim to make their series wound disposers, in their brief comeback period, they had a 3/4 hp model. This one never overheated under corn cob load, but there were minor differences between it and the original GE's which I didn't like.
Yes, noise is the only true disadvantage of a series wound disposer. In a larger horsepower version it overcomes the heating problem, you mentioned, but you still have that vacuum cleaner sound problem, if one does not like that. It is less noticeable when you have a heavy cast iron sink.
Yes, I have encountered some of GE series wound motor disposals oveheating, ( I have had eight of them) They pull more amps as they do under load so if you keep a load for a long time, like a sink full. But this rarely happens. You actually WANT a GE series motor to slow down, because that is when torque increases. The peak of the torque curve occurs near stall.
It's suppposed to do that. As it grinds the load it speeds back up. Overall, I have found my series GE's to be the fastest dispoers I have ever had. Especially on pork chop bones and corn cobs. Now corn cobs, if put in too quickly, will oveheat a GE Series. Once again its, because of it being a small 1/2 motor.
The unit your friend had may have been defective. My parents second disposer, after the 1967 Westinghouse bit the dust, was a GE series wound.
When it met its glory, dad bought a Sears Lady Kenmore (ISE) and kept it about a week and pulled it out. My mom didn't like it and my dad hated it because of the slow 1725 rpm motor. He didn't even try totake it back to Sears, we gave it to our church to use in the church kitchen.
He bought another GE Series wound. He wouldn't have anything else (and my dad wan't necessary a GE fan) as nothing could compare with the grinding speed. Since my mom canned all the time, the sink was always full of tomato peels, vegetable peels, you name it. Nothing took care of a sink full of vegetable wastes like a GE series. The Westinghouse and the Sears were only minor contenders, ha. My mom loved the GE Series and she sure put it through some torture with her canning. Mom rarely used prepackaged food, so there was always potato peels, onion skins, carrot ends, cantalop rinds,fruit pits or something like this going into it every night. The GE Series models are real troopers.
Speaking of pits. Most disposers bounce fruit pits (like peach pits) around the hopper for a while before the grind up. The GE series disposers are the ONLY ones I have ever had, out of inumerable brands I have performance tested, that take carae of pits nearly instantly. The Carbaloy cutter, coupled with the high speed motors, takes them down to nothing very quickly.
I have ISE KitchenAid 1hp in my kitchen now, and a GE "Pirahanna" series in my kitchenette in the lower level. If I have a lot of peach or plum pits, I take them downstairs and the GE series takes care of them in a hurry.
The ISE/KitchenAid will eventually take care of them, but somewhat more slowly and I guess I am impatient. So overall, if I had to to choose a favorite out of all of the disposers (probably 30+) I have performance tested over the years, the GE series wound is the best, overall. Not that evey single feature it has is the best.
Best virtues. Unbeatable grinding speed and can handle things most disposers only dream of. Stainless hopper, stainless turntable, stainless impellers, stainless cutter. Even in GE's bottom of the line line models. And of course, #1 in speed for pork chops bones and fruits pits over any machine I have ever had...period. (but even wild man Barry didn't put beef bones it it

).
With that being said, no it's not perfect because of only two things:
1.) very noisy motor -- which can't be helped in series (universal)motors. You can try to sound insulate, but you still have an 8000 rpm motor.
2.) GE only made them in a one third, and a half-horsepower version. But back the sixties and seventies, I don't think you get get higher in a home unit. So yes, a continuous load of very heavy materials would cause the cutoff breaker to kick in. The cooled quickly though and you were back about your business shortly.
Whether ISE's winding are copper or copper clad, I don't know. The gigantic spool they were showing, at the factory, did not say. As long as it provides it's rated horsepower, it's fine by me either way.
You made a mis-statement, John. Disposers do not have cutters on the turntable. The turntable's job is to drive the food, onto the cutter ring, at the periphery of the turntable.
The cutter is usually a circular ring at the base of the hopper, where the turntable's impellers come closest to meeting the hopper walls.
The number of "teeth" vary. The Hobart KitchenAids had the most "teeth" (or cutter bars, or "blades") I have seen.
None are razor sharp, but if you put your and in there and rub your finger along it there is a very mild sharpness, or dege, you can feel.
Now the GE Series wound are quite unique in that they had only one cutter, welded
about halfway up the stainless steel hopper. In their upper line sries wound models, there was a small square Carbaloy cutter. Once again, not sharp like a knife but you could feel the mild edge on it. One cutter is all you need, however, when you combine it with 8000 rpm.
KitchenAid (Hobart) advertised its undercutter too (beneath the turntable), to cut stingy waste like corn husk and silk, into even finer particles before the wastes exited the unit.
Remember the good old "Wham Jam Breaker" on the Original Hobart Kitchen Aid. Those were the days! Never was fortunate to own one of these, almost bought one but was waiting for Hobart to come out with a 3/4 unit, and about this time, they decided to get out of the household disposer business.
I did have the Hobart "National" branded disposer. It had the fixed impeller turntable, like the KitchenAid, but did not have the Wham Jam feature, as well as no sound insulation.
I did buy a Viking clone of the Hobart KitchenAid, before Viking contracted ISE to build them. The Wham Jam Breaker did work. On the rare occasions it did jam, you reached down and pushed the "Wham Jam" button and the turntable vibrated very rapidly, usually breaking the jam loose.
The other neat thing abaout the Viking/Hobart is it had the best auto-reversing system I had encountered. Jams occur a little more freguently with a fixed impeller system, as the impellers cannot swing away from the item lodged in the cutter blade. The Hobart design sensed the speed decrease and reversed, so normally there was no reason to even use the Wham Jam Breaker, only once in a great while. Too bad, because it was fun.
It was really cool. Sometimes it occurred so fast you rarely even realized it went to stall, reversed, and got back up to speed in about a second or fraction over. Bravo to the Hobart engineers!