Burroughs BU4400 tape drive. What is it?

[mike at fenz.net]

Quoting Chuck Guzis via cctalk <cctalk at classiccmp.org>:
> If you're going to use this thing, do check the carbide (sometimes
> ceramic) cleaning blade.  You want the edge to be sharp and smooth; if
> it's nicked or chipped, it will end up doing more harm than good.

In this case, it's really just for show - I don't have a real 9-track  
drive, or any tapes. That was why I'd prefer an unusable tape, rather  
than destroying a good tape by passing it through a cleaner  
repeatedly. However, tapes do seem really quite cheap and easy to find.

> I suspect that a carbide insert for machine tools might be cobbled up as
> a replacement, if required.

I suspect the blade is actually missing. There's am empty spot that  
looks like it might have taken a cartridge at once point in the tape  
path. Maybe nothing actually goes there, but on the tape path diagram,  
it seems to show something with a narrow gap the tape passes through.  
If I wanted to make it functional, I could fairly easily make a  
cartridge that fits in the spot as above, and passes the tape across a  
blade of that sort without a great deal of pressure.

I would really like a working drive sometime, so I am actually  
considering doing this...

Cheers,
Mike