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Placement of mounting holes in narrow modules
MUFF WIGGLER Forum Index -> Music Tech DIY  

Where should the holes go on narrow modules
Central
16%
 16%  [ 1 ]
To the left or right
83%
 83%  [ 5 ]
Total Votes : 6

Author Placement of mounting holes in narrow modules
MikeDB
For wide modules it's pretty obvious that the holes are equally spaced from the centre on the correct pitch. However narrow modules tend to have just a single mounting hole top and bottom so I assumed central would be the preferred position provided the hole is slotted.

However looking at products on the market such as
http://www.ajhsynth.com/images/MiniMod/Contour_Black_Cutout_vsmall.jpg
the holes on the narrow module are offset to the left or right.

Is there a reason for this and should I do the same for my own modules ?
HZR
I think it has something to do with stability, but i‘m not shure. Maybe its just a type of ‚normalisation‘ where these holes are placed
Jason Brock
When in doubt, do as Doepfer does.
You can make the hole wider for horizontal margin of error, but it needs to be compatible with pre-drilled rails (the kind that don't use sliding nuts).

MikeDB
Jason Brock wrote:
When in doubt, do as Doepfer does.
You can make the hole wider for horizontal margin of error, but it needs to be compatible with pre-drilled rails (the kind that don't use sliding nuts).


Well I'm using elongated holes but for modules that size I've four of them. The only reason I can think they haven't is so that they can fit the module name on :-)
BananaPlug
In the case of that A-119 there's and advantage to having the screws lined up with the jacks because a snug plug/jack combination exerts some pull when the cable is unplugged. Not enough to bend the panel but it just feels flimsy.
joem
Jason Brock wrote:
When in doubt, do as Doepfer does.


Speaking of Doepfer, they have a guide on one of their DIY pages: http://www.doepfer.de/a100_man/a100m_e.htm
MikeDB
BananaPlug wrote:
In the case of that A-119 there's and advantage to having the screws lined up with the jacks because a snug plug/jack combination exerts some pull when the cable is unplugged. Not enough to bend the panel but it just feels flimsy.


Good point. My jacks are all central

joem wrote:
Jason Brock wrote:
When in doubt, do as Doepfer does.


Speaking of Doepfer, they have a guide on one of their DIY pages: http://www.doepfer.de/a100_man/a100m_e.htm


Yes that's already pinned up on my wall :-)
Graham Hinton
MikeDB wrote:
Is there a reason for this and should I do the same for my own modules ?


The panel sizes and hole positions are based on the Eurocard standard where it is usual to have a pcb on the left side running in card guides and that plugs into a backplane connector. In that scenario mounting holes 0.3" from the left edge are optimum for keeping the pcb tight in the socket and other holes have to be multiples of 0.2" from that position. Some modules have captive screws which pull the module in to the connector.

You can please yourself what you omit from the standard, Doepfer did, but doing something different without understanding will lead to incompatibilities. Like Analogue Systems.
mskala
Jason Brock wrote:
When in doubt, do as Doepfer does.


Yeah, I don't really see this as a question. The first set of mounting holes is 7.50mm from the left edge of the panel, period. Otherwise, what you're building is not Eurorack.

If the panel is wide enough that holes 7.50mm from the left edge aren't close enough to the right edge for it to be secure there, then it's time to add a second pair of holes. I use four-hole mounting on my 8HP modules, though the Doepfer documentation suggests it's only necessary starting at about 10HP.
MikeDB
mskala wrote:
Jason Brock wrote:
When in doubt, do as Doepfer does.


Yeah, I don't really see this as a question. The first set of mounting holes is 7.50mm from the left edge of the panel, period. Otherwise, what you're building is not Eurorack.

If the panel is wide enough that holes 7.50mm from the left edge aren't close enough to the right edge for it to be secure there, then it's time to add a second pair of holes. I use four-hole mounting on my 8HP modules, though the Doepfer documentation suggests it's only necessary starting at about 10HP.


Ok thanks - that's more of a definitive statement as to the reasons why.

So can I ask my lead-on question. What if you have an odd width HP module (Doppler lists a 21 HP on their table) and use the strips of nuts rather than floating ones. If the holes are always 7.5mm from the left, it seems to me there is no way of closing the gap unless the next module has a slotted hole 5mm wide.

Is that correct ?
fuzzbass
The most stable arrangement for two fasteners is to have top and bottom biased toward opposite sides.
MikeDB
Graham Hinton wrote:
MikeDB wrote:
Is there a reason for this and should I do the same for my own modules ?

You can please yourself what you omit from the standard, Doepfer did, but doing something different without understanding will lead to incompatibilities. Like Analogue Systems.


Now had time to look at Analogue Systems and can't see what they've done wrong so can you fill me in before I make the same mistake please ?
Graham Hinton
MikeDB wrote:
What if you have an odd width HP module (Doppler lists a 21 HP on their table) and use the strips of nuts rather than floating ones. If the holes are always 7.5mm from the left, it seems to me there is no way of closing the gap unless the next module has a slotted hole 5mm wide.

Is that correct ?


No. The tapped strips have a 1HP (0.2") spacing with the left hole 1.5HP (= 0.3" or 7.62mm) from the left edge.
Four 21HP panels fit an 84HP frame just fine.

Quote:
Now had time to look at Analogue Systems and can't see what they've done wrong so can you fill me in before I make the same mistake please ?


Their holes are 5.08mm from the left edge.

You would be better informed by going back to the standard this is based on rather than trying to make deductions based on corrupted secondary information. Doepfer don't have a standard, they just have a simplified description without any tolerances. e.g. The 7.5mm you keep mentioning combines the tolerances of the panel width and the hole position, but does not have a tolerance.

This document will be helpful: Schroff Standards Summary, see page 14. Other pages will help you see the big picture.

Note that the mounting holes are not defined as a slot. Pre-made blank panels have a slot to take captive mounting screws, not to allow you to cram the panels tightly against each other. The panels are supposed to be smaller than the nominal width to guarantee that they fit with manufacturing tolerances.


If you buy any standard frame parts they are going to be based on this standard and most of the manufactuers will have never heard of "Eurorack" or Doepfer. Doepfer merely based Eurorack on a widely used industrial standard that had been in common use for over 25 years before they started using it so that they could get ready made parts. Every other modular synthesizer system reinvents the wheel for their mechanical format and usually fails to make it round.
MikeDB
Well now I have two 'definitive' statements that for Eurorack synths, the left hole is 7.5 and 7.62 mm from the left hand side of the panel.

I'll read the Schroff document and do whatever that suggests since it looks the nearest thing to a standard I've seen so far.
neil.johnson
MikeDB wrote:
Well now I have two 'definitive' statements that for Eurorack synths, the left hole is 7.5 and 7.62 mm from the left hand side of the panel.

I'll read the Schroff document and do whatever that suggests since it looks the nearest thing to a standard I've seen so far.

A reasonable starting point if you don't feel up to the sums is to knock up a front panel in Front Panel Designer: https://www.schaeffer-ag.de/en/downloads/front_panel_designer/
Create a panel of the right size, then insert appropriate system holes, then remove the ones you don't need. Export the DXF and import into your CAD tool of choice.
It may not be perfect, but it's a lot closer than winging it on your own.

Neil
mskala
MikeDB wrote:
So can I ask my lead-on question. What if you have an odd width HP module (Doppler lists a 21 HP on their table) and use the strips of nuts rather than floating ones. If the holes are always 7.5mm from the left, it seems to me there is no way of closing the gap unless the next module has a slotted hole 5mm wide.

Is that correct ?


I don't really understand this question. On a 21HP module, I would put one set of mounting holes 7.50mm from the left, and the second set 98.94mm from the left. That is 18HP (=91.44mm) between the two sets of mounting holes. No problem screwing both sets into a threaded strip with standard 1HP spacing. The right edge of the 21HP panel will be a little less than 21HP (=106.68mm) from the left edge, or 7.74mm from the second set of mounting holes. The next module down the line has its first mounting holes 21HP+7.50mm from the left edge of the 21HP module; that is exactly 21HP from the first mounting holes of the 21HP module, and again, no problem meeting the spacing constraint of the threaded strip. I don't know what "gap" there is that would need to be closed in this situation.
Graham Hinton
MikeDB wrote:
Well now I have two 'definitive' statements that for Eurorack synths


A remark on a web page is not a "definitive statement"--including mine. Go to the source and that is not Doepfer. The Schroff document is not the source either, but it is closer and has the correct information for free. The real source is IEC 60297 and the documentation for that will cost hundreds.

If you examine closely the drawing on page 14 that I pointed to, you should see that the left mounting hole is 7.62 (0.3") from the edge of the pitch line. The panel is not on the pitch line because it is defined as (n x 5.08) - 0.3 [+0/-0.2)]mm width. That means that there is a minimum of 0.3mm and a maximum of 0.5mm gap between the actual panel width and the space for the panel. You could read the tolerance as -0.4 +/-0.1mm and that is tighter than most general metalwork at +/-0.25mm.

I am showing the inch measurements because the standard is based on a 0.1" grid that has then been metricised. 7.62mm is not an arbitrary number, it is 0.3", whereas rounding that to 7.5mm is arbitrary. It happens to still be within the original specification.

The simplified Doepfer drawings do not show any tolerances, but if you want to make a panel and machine it there are tolerances whether you like it or not. There will be an error in marking out the panel and another in machining it, the aggregate of those errors has to be checked against the specification and the panel rejected if it does not conform. Precision manufacturing anything is all about understanding tolerances, otherwise it's just carpentry. The companies that make panels for Doepfer work to tolerances so assuming that the description on their web site is a definition is just naive.
MikeDB
mskala wrote:
I don't really understand this question. .


Yes it's ok. I'd got confused but am fine now. Thanks
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