I hope this was not discussed in the "M1 Abrams questions and answers" thread - I admit I was not following it closely and it is too long now to find anything there quickly. If it was discussed, just let me know - I'll find the answer there.

My question is: What is this detail:



Sometimes it is covered, like on this Sabot's photo:



And sometimes it looks like it was never present there at all:



What is this part? Which tanks had it? In Verlinden book this detail is visible and there it looks like a small square (not round like on Rob's photo above) metal plate with a round hole in the middle welded flat to the armor. In the book it does not have the mushroom shaped cover visible on the first photo above.

Cheers,
Pawel

It is the heater intake port. It was not present on the M1 or M1IP and was added to the initial M1A1s. It was deleted with the Heavy Common since that variant was designed with the capabilities of amphibious operations (sea water coming in the air intake port would not be good for the heater). Heavy Commons had the opening welded over and eventually it was deleted altogether from the tank design.

Many current tanks are remanufactured so you will see a mix of no opening or welded over opening. There are still tanks with the intake port in place. Of course, I'm not an expert or anything.

Thanks Rob!

I will need to add this detail to the Dragon kit, which I plan to convert to early M1A1. I also have to mention it in my Abrams article, as it should be present in Academy kit and earlier Tamiya M1A1 kits, but is missing from their hulls.

I think however that early HC tanks still had this intake - the tank on the first photo, photographed in 1991 is US Army HC, at least from what I can tell. I cropped the picture, but on the original photo it is visible that it has T-158 tracks, new style doghouse and new smoke grenade boxes. The tank in Verlinden book, the one with flat intake without cover, is early M1A1. First Heavy Commons probably had the mushroom shaped cover added over the intake, as on the first photo above - I think it was designed to prevent sea water from getting into the heater. It obviously didn't work well, so intake was later deleted completely. That's only my guess of course, based on photos.

Cheers,
Pawel