Racking a PDP-11/24

[Rob Jarratt]

> -----Original Message-----
> From: Paul Koning <paulkoning at comcast.net>
> Sent: 26 February 2022 19:21
> To: rob at jarratt.me.uk; Robert Jarratt <robert.jarratt at ntlworld.com>;
> cctalk at classiccmp.org
> Subject: Re: Racking a PDP-11/24
> 
> 
> 
> > On Feb 26, 2022, at 3:14 AM, Rob Jarratt via cctalk
<cctalk at classiccmp.org>
> wrote:
> >
> > I am wondering if I have racked my 11/24 correctly.
> >
> >
> >
> > As you can see here:
> > https://robs-old-computers.com/2022/02/10/pdp-11-24-progress/ I have
> > put the CPU at the top and the two RL02 drives underneath.
> 
> That seems fine.  Others mentioned having them at the top of a low
cabinet,
> but the RL02s I used were in H960 (6 foot) racks, mid-level with stuff
above
> them.
> 
> > The problem is that the CPU enclosure catches on the RL02 underneath.
> > There is a bit of play in the mounting bracket:
> > https://rjarratt.files.wordpress.com/2022/02/cpu-mounting-bracket.jpg.
> > With a bit of manipulation I can get the CPU to slide in. However, I
> > am wondering if I have racked it correctly? I don't think there is
> > room to move the RL02s down and it would presumably leave a bit of a
> > gap below the CPU. There seems to be very little clearance between the
> > CPU and the RL02 at the front but more at the back, but I am sure that
> > the rails are mounted horizontally. Is it just a matter of tightening
> > the big screws that hold the mounting brackets to stop the play? If so
> > I am not sure I have a big enough screwdriver!
> 
> Hardware stores can fix that.  Or Brownells, where you can get really good
> screwdrivers that are less likely to damage screw heads than standard
> hardware store ones do.

I am not in the USA, but I am should be able to look for other screwdrivers
here in the UK. I already have one quite big one, but I think it is still
way too small for this purpose.

> 
> Something I observed on my H960 that wasn't all that obvious at first: the
> holes are NOT evenly spaced.  If I remember right, they come in groups of
> four where the spacing between groups is something like 1/8th of an inch
> more than the spacing within groups.  The consequence is that if you
attach
> your brackets using the wrong set of holes things may be 1/4 inch (or
> whatever the delta is) closer than they were meant to be.
> 
> 	paul