The movie was called The Long Ships and the device was called The Mare of Steel. I haven't seen that movie since I was kid also. I remember it because I always liked Richard Widmark. The movie is set during the Viking era.
Well there you go! That’s the one. Someone even posted a photo. I wonder how I got “iron mane” out of “mare of steel” but after 40 years or so, I guess that’s not too bad.