We had the cream colored DAM Powerdrive when i was a kid,,,i remember that vac being very heavy, and clumsy to carry up and down stairs,,,and i remember the suction being poor, especially from the hose, even on the highest dial setting,, and especially if the bag was getting full.
I also remember having to take apart the hose from the brush roll to the bag compartment several times,,it was always getting clogged with cat hair. (we only had one cat that was short haired)
The vac was easy to push in the power drive mode,, and did an OK job of grooming the carpet,,but i do remember the bag being a hassle to change, and the little red filter under the bag was always needing washed.
There was no way you could push that beast on heavy shag carpet with the power drive off.
Of course, the paper bags back in the 70s werent like today,,,there was no "Hepa" filtration, or several ply bags, at least not for a DAM.
The handle constantly needed tightening too,,it was always loose.
I wish i had better memories of that vac,,,but it seemed to me that it was poor preforming,,i remember having to dust the furniture after vacuuming, because the thing would spew dust something awful out of the upper front cover air vents.
Maybe we got ahold of a lemon? All DAM powerdrives couldnt have been this way.
It finally died in around 1978 when it burned up a belt and almost burned a hole in the carpet from the black hot smoke and suet.
One aunt had the blue regular DAM,,and i know used it for at least 20 years. It finally went to the garbage heap after the back wheels had been ground down to stumps! She had a very small house, with minimal carpet,,so maybe thats why it lasted so long.