16 Jun
2005
16 Jun
'05
5:42 a.m.
I brought one of these home from Bletchley last weekend - turns out
they're quite addictive little things :-) It's a Monromatic 8N-3-213
which was marked as broken - I thought I'd see if there was anything
obviously wrong inside, plus of course I was curious as to what the
innards of such a machine looked like.
Question - does anyone have service information for these machines
(yeah, right!) or useful tips on things to check over?
So far I've found an acorn jamming up the works (!!) and lots of dirt,
but the mechanism's reasonably oily still and in good condition. Some of
the keys seem to jam occasionally or not latch - I'm hoping that's down
to dirt rather than wear (it seems to be improving the more I tap away
at things to be honest).
After checking that everything was free to turn without jamming I
applied power...
There's some earth leakage which would be useful to track down -
possibly a break-down in cable insulation? I've not worked out what the
large rotating thingy on the outside end of the motor shaft does yet
though, as this seems to be connected to an insulated plate (and throws
off quite a few sparks when running)
Can't say I've ever seen such a complicated thing. Electronic circuits
don't even come close in complexity :-) I don't think I'd be up for a
complete stripdown and rebuild; I'd never get it all back together.
ps. Is there a better place to ask than here? Not sure whether
electromechanical calculators are on topic or not!
pps. Anyone care to guess a date for this machine? I'd make a wild guess
at mid-50's but really don't know.
cheers
Jules
16 Jun
16 Jun
9 a.m.
Check out Ernie Jorgensen's Office Machine Americana website. He has
service and operating manuals (reproductions) for many old mechanical
calculators. http://users.lewiston.com/ejorgens/office/index.htm
I see that he does have some materials for the 8N-series calculators.
Yes, these machines are amazingly complex. I seriously wonder if the
mechanical engineering talent exists today to design such a machine from
scratch.
Best wishes,
Rick Bensene
The Old Calculator Web Museum
Beavercreek, Oregon
http://oldcalculatormuseum.com
[mailto:cctalk-bounces at classiccmp.org] On Behalf Of
Jules Richardson
Sent: Thursday, June 16, 2005 5:43 AM
Subject: Monroe electromechanical calculators
I brought one of these home from Bletchley last weekend -
turns out they're quite addictive little things :-) It's a
Monromatic 8N-3-213 which was marked as broken - I thought
I'd see if there was anything obviously wrong inside, plus of
course I was curious as to what the innards of such a machine
looked like.
Question - does anyone have service information for these
machines (yeah, right!) or useful tips on things to check over?
Can't say I've ever seen such a complicated thing. Electronic
circuits don't even come close in complexity :-) I don't
think I'd be up for a complete stripdown and rebuild; I'd
never get it all back together.
9:25 a.m.
On Thu, 2005-06-16 at 09:00 -0700, Rick Bensene wrote:
Check out Ernie Jorgensen's Office Machine
Americana website. He has
service and operating manuals (reproductions) for many old mechanical
calculators. http://users.lewiston.com/ejorgens/office/index.htm
I see that he does have some materials for the 8N-series calculators.
Thanks - will take a look!
Yes, these machines are amazingly complex. I
seriously wonder if the
mechanical engineering talent exists today to design such a machine from
scratch.
Agreed. Although I suppose the theory of the individual mechanisms is
documented in various places - it's the squeezing it into such a compact
unit that is really stunning. Exploded to the size of a desk it'd
probably make sense (with a lot of staring!) but it's such a tight mass
of levers / cams / gears and springs that it's impossible to see how
different bits interact.
We've got a few electromechanical Monroe units - maybe as many as ten -
but this was the only one of that particular type (all the rest are
earlier).
Regarding the rotating widget on the end of the motor, I think it's a
speed governor - maybe there were problems with the motor running too
fast in certain environments and so this was added to stop the problem
(the only other image of 8N 213 insides I've seen on the 'net are a
little different, despite both being 8N 213's)
cheers
Jules
9:21 a.m.
On Thu, 16 Jun 2005, Jules Richardson wrote:
I brought one of these home from Bletchley last weekend - turns out
they're quite addictive little things :-) It's a Monromatic 8N-3-213
which was marked as broken - I thought I'd see if there was anything
obviously wrong inside, plus of course I was curious as to what the
innards of such a machine looked like.
Question - does anyone have service information for these machines
(yeah, right!) or useful tips on things to check over?
There's a guy on eBay that sells reproduction service manuals of old
mechanical and electromechanical calculators.
He's also got a terrific website here:
http://www.mortati.com/glusker/
One of the entries so far is the Monroe IQ-213:
http://www.mortati.com/glusker/elecmech/rotary/MonroeIQ213.htm
Is this the same as your 8N-3-213 perhaps?
--
Sellam Ismail Vintage Computer Festival
------------------------------------------------------------------------------
International Man of Intrigue and Danger http://www.vintage.org
[ Old computing resources for business || Buy/Sell/Trade Vintage Computers ]
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2:54 p.m.
On Thu, 2005-06-16 at 09:21 -0700, Vintage Computer Festival wrote:
On Thu, 16 Jun 2005, Jules Richardson wrote:
There's a guy on eBay that sells reproduction service manuals of old
mechanical and electromechanical calculators.
He's also got a terrific website here:
http://www.mortati.com/glusker/
Thanks - that looks like a nice site!
We've got 'user' manuals for some of our other Monroe machinces (which
thinking about it are from the days where perhaps they do give
instructions for critical oil points and other useful info).
Unfortunately I haven't found anything for this particular Monroe yet...
One of the entries so far is the Monroe IQ-213:
http://www.mortati.com/glusker/elecmech/rotary/MonroeIQ213.htm
Is this the same as your 8N-3-213 perhaps?
Externally it looks similiar - that one appears to be a slightly later
model (the one I have here has a few less buttons across the bottom). I
expect the 'core' is the same on both machines though. The carriage
certainly looks identical.
I think I'll drop the guy an email and see if he has any tips for
cleaning the mechanism (such as just leaving the whole mechanical bit in
an oil bath for a few weeks or something!). For normal mechanical things
I completely dismantle them, clean / fix individual parts, then
reassemble - but this thing's really a bit *too* complicated for that
approach (without me having experience of working on simpler versions of
such machines first anyway)
cheers
Jules
4:49 p.m.
I brought one of these home from Bletchley last weekend - turns out
they're quite addictive little things :-) It's a Monromatic 8N-3-213
which was marked as broken - I thought I'd see if there was anything
obviously wrong inside, plus of course I was curious as to what the
innards of such a machine looked like.
Question - does anyone have service information for these machines
(yeah, right!) or useful tips on things to check over?
No psecific service information, but my first comment is that 99% of
problems with mechanical calculators are due to gummy lubricants. Worn or
broken parts are uncommon.
Serondly, do not spray it with Wanton Destruction 40, or anything else
for that matter. You will do a lot more harm than good...
So far I've found an acorn jamming up the works (!!) and lots of dirt,
An Acorn... What, a System 1, or an Atom, or a Beeb or an Arch, or what...
(sorry, couldn't resist...)
but the mechanism's reasonably oily still and in
good condition. Some of
the keys seem to jam occasionally or not latch - I'm hoping that's down
to dirt rather than wear (it seems to be improving the more I tap away
at things to be honest).
After checking that everything was free to turn without jamming I
applied power...
There's some earth leakage which would be useful to track down -
possibly a break-down in cable insulation? I've not worked out what the
Most of the time, that's due to tracking across the impregnated fibre
insulators used in things like the automatic on/off swtich.
large rotating thingy on the outside end of the motor
shaft does yet
though, as this seems to be connected to an insulated plate (and throws
off quite a few sparks when running)
Almost certainly a governor. Do not be tempted to bypass it, many of
these machines used series wound motors which will get up to a ridiculous
speed if not controlled and do considerable damage.
Trakcing on the insulators in the governor is another source of earth
leakage.
You generally have to disconnsect the wiring between the power connector,
motor, automatic switch anf governor and test each bit separately with a
megger (how do you know there is a leak, BTW?). Hopefully you can repalce
the offending insulator. If not, you could run the machine off a good
isolating transformer, and make sure the chassis is properly earthed.
Can't say I've ever seen such a complicated thing. Electronic circuits
don't even come close in complexity :-) I don't think I'd be up for a
I've not seen this one, but from the mechanical calculators I have been
inside, there's typically the same mechanism repeated <n> times (digit
entry, accumulator register, etc, and some control linkages, which are
typically outside the side frames. There are a lot of parts, but the
complexity is not that high.
complete stripdown and rebuild; I'd never get it
all back together.
ps. Is there a better place to ask than here? Not sure whether
electromechanical calculators are on topic or not!
pps. Anyone care to guess a date for this machine? I'd make a wild guess
at mid-50's but really don't know.
Sounds about right. Maybe a little later (early 1960s).
-tony
17 Jun
17 Jun
4:49 a.m.
On Fri, 2005-06-17 at 00:49 +0100, Tony Duell wrote:
There certainly doesn't seem to be much sign of wear on this machine.
The plus/minus/manual carriage movement keys seem prone to jamming and I
need to figure out the source of that (possibly more foreign debris in
the mechanism somewhere)
:-)
I have no idea how it got in there; there isn't really a sufficient gap
anywhere for such a thing to fall inside. And it was *very* well buried
inside the mechanism (almost as though someone stuck it in there for
fun!)
Aha, well I can isolate and test easy enough there without any severe
dismantling of things. Can anything be done to fix the problem (short of
making new insulators)?
Yep, it's the bits outside the frames that are rather scary-looking! The
actual underside of the key bed doesn't look too bad. This machine's
fully automatic, so I suppose it's an extra stage of complexity over a
semi-automatic machine. It's got three registers, plus the multiplier
one.
Uh huh - digging around since posting that, it looks like circa 1962 is
about right.
cheers,
Jules
Question -
does anyone have service information for these machines
(yeah, right!) or useful tips on things to check over?
No psecific service information, but my first comment is that 99% of
problems with mechanical calculators are due to gummy lubricants. Worn or
broken parts are uncommon. Serondly, do not spray it with Wanton Destruction 40,
or anything else
for that matter. You will do a lot more harm than good...
I've been using sewing machine oil so far (which is the lightest stuff
I've got). I just wonder if leaving it in a (slowly circulating /
filtered?) bath of oil for a week or so would be useful for freeing
stuff up and getting all the dirt out...
So far
I've found an acorn jamming up the works (!!) and lots of dirt,
An Acorn... What, a System 1, or an Atom, or a Beeb or an Arch, or what...
(sorry, couldn't resist...) There's
some earth leakage which would be useful to track down -
possibly a break-down in cable insulation? I've not worked out what the
Most of the time, that's due to tracking across the impregnated fibre
insulators used in things like the automatic on/off swtich. Almost certainly a governor. Do not be tempted to
bypass it, many of
these machines used series wound motors which will get up to a ridiculous
speed if not controlled and do considerable damage.
Yep, I saw somewhere that 180rpm is typical for governed motor speed...
Can't say
I've ever seen such a complicated thing. Electronic circuits
don't even come close in complexity :-) I don't think I'd be up for a
I've not seen this one, but from the mechanical calculators I have been
inside, there's typically the same mechanism repeated <n> times (digit
entry, accumulator register, etc, and some control linkages, which are
typically outside the side frames. There are a lot of parts, but the
complexity is not that high. pps. Anyone
care to guess a date for this machine? I'd make a wild guess
at mid-50's but really don't know.
Sounds about right. Maybe a little later (early 1960s).
9:30 a.m.
On Fri, 2005-06-17 at 11:49 +0000, Jules Richardson wrote:
On Fri, 2005-06-17 at 00:49 +0100, Tony Duell wrote:
I just tried degreasing the ones that hold the plate supplying the 'hot'
feed to the governor, then baking them in an oven for a bit. Seems to
have done the trick - whether it's a long term repair or not is another
matter...
cheers
Jules
Most of the time, that's due to tracking
across the impregnated fibre
insulators used in things like the automatic on/off swtich.
Aha, well I can isolate and test easy enough there without any severe
dismantling of things. Can anything be done to fix the problem (short of
making new insulators)?
10:45 a.m.
On Fri, 17 Jun 2005, Jules Richardson wrote:
:-)
I have no idea how it got in there; there isn't really a sufficient gap
anywhere for such a thing to fall inside. And it was *very* well buried
inside the mechanism (almost as though someone stuck it in there for
fun!)
Well, obviously a squirrel stored it there and then forgot where he left
it! Happens all the time.
--
Sellam Ismail Vintage Computer Festival
------------------------------------------------------------------------------
International Man of Intrigue and Danger http://www.vintage.org
[ Old computing resources for business || Buy/Sell/Trade Vintage Computers ]
[ and academia at www.VintageTech.com || at http://marketplace.vintage.org ]
So far I've found an acorn jamming up the works
(!!) and lots of dirt,
An Acorn... What, a System 1, or an Atom, or a Beeb or an Arch, or what...
(sorry, couldn't resist...) 
12:41 p.m.
----- Original Message -----
From: "Jules Richardson" <julesrichardsonuk at yahoo.co.uk>
To: <cctalk at classiccmp.org>
Sent: Friday, June 17, 2005 12:49 PM
Subject: Re: Monroe electromechanical calculators
I have had some success on Tektronix 'scope switches. I soak the sitch wafer
in de-greaser (I've used the RS aerosol version), changing the solution a
couple of times, then I allow the switch to air dry, before lubricating it
SPARINGLY with contact lubricant, and a suitable grease for the mechanical
detent and bush.
The other thing to check is the filter capacitors on the motor and mains
input - the can be temporarily disconnected for a quick check (but if you
leave them off, the neighbours will complain -TV and radio wiped out for
about 200yds!)
If the governor is similar to the type used on Creed teleprinters, then make
sure that the contacts are properly cleaned and burnished - they have a
tendency to "hook" and make a permanent contact, allowing the motor to
overspeed.
Jim.
> > There's some earth leakage which would
be useful to track down -
> > possibly a break-down in cable insulation? I've not worked out what
the
Most of the time, that's due to tracking across the impregnated fibre
insulators used in things like the automatic on/off swtich.
Aha, well I can isolate and test easy enough there without any severe
dismantling of things. Can anything be done to fix the problem (short of
making new insulators)? > Almost certainly a governor. Do not be tempted to
bypass it, many of
> these machines used series wound motors which will get up to a
ridiculous
speed if not
controlled and do considerable damage.
Yep, I saw somewhere that 180rpm is typical for governed motor speed...
5:18 p.m.
Serondly, do
not spray it with Wanton Destruction 40, or anything else
for that matter. You will do a lot more harm than good...
I've been using sewing machine oil so far (which is the lightest stuff I've got). I just wonder if leaving it in a
(slowly circulating /
filtered?) bath of oil for a week or so would be useful for freeing
stuff up and getting all the dirt out...
No!. That is a sure way to get oil where you don't want it (like between
parts that are designed to slide over each other), and gum things up.
There is a bodger's trick of putting the whole machine (minus keytops,
rubber parts, and if possible the motor) in a solvent bath to clean out
the old lubricant and dirt, and then re-lubricating everything with a
suitable oiler tool. Everything meaning bearings, etc.
SOmewhaere I have a copy of a service manual for a hand-cranked
mechanical calculator (I think a friend found it on a web site). It makes
it _very_ clear that this is not the right thing to do, and that you
should take it all apart, clean each part separately and put it back
together again. Of course it's a lot easier to do that if you have the
service manual...
Most of the
time, that's due to tracking across the impregnated fibre
insulators used in things like the automatic on/off swtich.
Aha, well I can isolate and test easy enough there without any severe
dismantling of things. Can anything be done to fix the problem (short of
making new insulators)?
7130
days inactive
7132
days old
10 comments
5 participants
participants (5)
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ard＠p850ug1.demon.co.uk -
jim＠g1jbg.co.uk -
julesrichardsonuk＠yahoo.co.uk -
rickb＠bensene.com -
vcf＠siconic.com