26 Feb
2022
26 Feb
'22
8:04 p.m.
Thank you for the reply.
-----Original Message-----
From: pbirkel at gmail.com <pbirkel at gmail.com>
Sent: 26 February 2022 08:48
To: rob at jarratt.me.uk; 'Rob Jarratt' <robert.jarratt at ntlworld.com>;
'General
Discussion: On-Topic and Off-Topic Posts'
<cctalk at classiccmp.org>
Subject: RE: Racking a PDP-11/24
The conventional mounting for RL02 drives in a corporate cabinet puts one
at
the top with the 6U CPU in the middle *but* that
assumes that you have a
corporate cabinet designed for that purpose -- in which case the top is
missing so that the RL02 disk-pack can be directly accessed, and there is
a 1U
divider below the top RL02 that reinforces the rack
(and in effect
replaces the
1U lip on your rack top).
I saw something somewhere that suggested the RL02 should be at the top with
the disk accessible without pulling out the drive. I don't think the cabinet
I have was intended to do that, but I will have a closer look.
AFAIK you should be able to make your rack plan work; it's just the case
that
RL02 are always "top snug" (at least in my
experience). Have you tried
raising
the 6U CPU as high as possible *before* tightening the
bolts/screws on the
mounting flanges on the slides (to the rack, not to the chassis)?
There's usually ~1/8" of play there. From your photo perhaps you have
already done that as the CPU-front looks to be snug to the rack-top. If
anything it looks as if your RL02 instead need to move down.
I did try raising the CPU as high as possible. Will have another look to see
if the RL02s can be dropped a bit lower, but I don't think they can go lower
in terms of using lower slots, not unless I want to leave a gap and possible
interfere with the space at the bottom where there will be some cables I
think. I would like to avoid filing though!
I would start by moving the bottom RL02 down as far as
possible, then
repeat
with the second RL02.
Your observation that there is "very little clearance between the CPU and
the
RL02 at the front but more at the back" suggests
to me that you need to
fiddle move with the front and /or rear mounting flange positioning on the
various slides. Don't assume that wherever "gravity drops them" is going
to
be correct.
If none of the suggested adjustments are working then I would consider
getting out a rat-tail file and enlarging the slots on the mounting
flanges on
the RL02 slides so as to let them drop a little lower
(assuming that you
have
clearance at the bottom!).
Regardless you shouldn't need to play with the slide-to-chassis attachment
points -- those are always "just so" and not really free to fiddle with
(no
"slop").
There *is* a bit of play in the big black sheet that is screwed onto CPU
enclosure.
In my experience "racking" is a fiddling-time and clearances can be
*really*
tight. But ... it can be done :->. Good Luck.
-----Original Message-----
From: cctalk <cctalk-bounces at classiccmp.org> On Behalf Of Rob Jarratt via
cctalk
Sent: Saturday, February 26, 2022 3:15 AM
To: General Discussion: On-Topic and Off-Topic Posts
<cctalk at classiccmp.org>
Subject: Racking a PDP-11/24
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.
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!
Regards
Rob