Prototype "Universal" fan mounting grid

[arturbecker]

Try 11 x 9.56, and 13.

Why do we need 120 and 140?

I thought most rads use #6.

You're right! It's #6. I had the converted ~3.5 milimiters in my head, which isn't even M3 either.

120 is needed for 240 rads:
Fan 1:
first hole is 0, second is 105
Fan 2:
first hole is at 120, second is 205

Similarly for 280 rads:
Fan 1:
first hole is 0, second is 124.5
Fan 2:
first hole is at 140, second is 264.5

 

[Thehack]

You're right! It's #6. I had the converted ~3.5 milimiters in my head, which isn't even M3 either.

120 is needed for 240 rads:
Fan 1:
first hole is 0, second is 105
Fan 2:
first hole is at 120, second is 205

Similarly for 280 rads:
Fan 1:
first hole is 0, second is 124.5
Fan 2:
first hole is at 140, second is 264.5

You would use slots, so the other direction doesn't need to be exact.

 

[arturbecker]

You would use slots, so the other direction doesn't need to be exact.

Yes, slots work when you only need to slide in one direction, e.g. Sliger Cerberus from a few posts back.
However, if one would want to adjust position in two dimensions, an elongated slot works for one dimension. Then, for the other dimension you could elongate the slots in the other dimension, which would possible make them too big. Or you could adjust the gaps in the second direction with a non-uniform pattern to make them fit.

 

[Shatrod]

Isn't 124.5 close enough to 125 to neglect? I can't imagine you would need more than 2 fans side by side in an sff setup, most cases only support dual rads anyway. 105 vs 125 is easy to space, just make 5.5mm holes with a 10mm stagger in both x and y.

I say it's close enough to neglect because of the screw size. If you are using fan screws then you need a 5.5mm hole to fit it through (really 5mm works so you will have some tolerance there) but then your fan to fan spacing is irrelevant. For 240 and 280 rads, the screw size is 6-32 which is 3.5mm diameter. That gives you a 0.75mm slop in any direction which is more than the 0.25mm error in your hole spacing. So you would be able to mount everything no problem provided you only have a dual rad. I can whip up a drawing of this tonight to illustrate if someone wants.

 

[Thehack]

Isn't 124.5 close enough to 125 to neglect? I can't imagine you would need more than 2 fans side by side in an sff setup, most cases only support dual rads anyway. 105 vs 125 is easy to space, just make 5.5mm holes with a 10mm stagger in both x and y.

I say it's close enough to neglect because of the screw size. If you are using fan screws then you need a 5.5mm hole to fit it through (really 5mm works so you will have some tolerance there) but then your fan to fan spacing is irrelevant. For 240 and 280 rads, the screw size is 6-32 which is 3.5mm diameter. That gives you a 0.75mm slop in any direction which is more than the 0.25mm error in your hole spacing. So you would be able to mount everything no problem provided you only have a dual rad. I can whip up a drawing of this tonight to illustrate if someone wants.

1. It is enough to neglect. Noctua officially states the pitch is 124.5.

2. Your math doesn't check out. You should always denote it as pitch, or center to center distance. 10 mm center to center (pitch) does not fit into 105 or 125 evenly.

If you mean that there is 10 mm of material between 5.5 mm holes, then your center to distance is 15.5. Which also doesn't divide evenly.

3. The technical term is clearance. You're correct on the clearance fitting, but your math from the previous point doesn't work out

 

[arturbecker]

You would use slots, so the other direction doesn't need to be exact.

I think I failed to understand you before. Do you mean:
In one direction (let's say X) we keep a pitch that works for both 120mm and 140mm, such as your suggested 9.56;
In the other direction (let's say Y), we slot the holes as needed so that they allow for mounting two fans in a row.

That works for the requirements I had in mind initially:
1) mounting both 120/140 fans with two degrees of freedom and "some" granularity of positioning
2) mounting both 240/280 radiators with two degrees of freedom and "some" granularity of positioning
3) radiators only have to be mountable in one direction (but the direction has to be the same for both)
4) should work with regular fan screws (at least for fans) and regular radiator screws (for radiators)
4) openings have to be smaller than 12.5mm (ingress protection rating 2 for solid particles)
5) depending on the material, the minimum "wall" needed between holes varies. I'm working with 2mm for aluminum (2mm thick) and 1.5mm for "steel", but that's tentative! If you have other values please share.

A possible slotted design (slots are 5.5*12.5, pitch is 14.5):

I couldn't make it quite work yet for 280mm but it seems like with some adjusting it'd work

 

[arturbecker]

Isn't 124.5 close enough to 125 to neglect? I can't imagine you would need more than 2 fans side by side in an sff setup, most cases only support dual rads anyway. 105 vs 125 is easy to space, just make 5.5mm holes with a 10mm stagger in both x and y.

I say it's close enough to neglect because of the screw size. If you are using fan screws then you need a 5.5mm hole to fit it through (really 5mm works so you will have some tolerance there) but then your fan to fan spacing is irrelevant. For 240 and 280 rads, the screw size is 6-32 which is 3.5mm diameter. That gives you a 0.75mm slop in any direction which is more than the 0.25mm error in your hole spacing. So you would be able to mount everything no problem provided you only have a dual rad. I can whip up a drawing of this tonight to illustrate if someone wants.

Thanks! I would certainly appreciate a drawing

 

[Thehack]

I think I failed to understand you before. Do you mean:
In one direction (let's say X) we keep a pitch that works for both 120mm and 140mm, such as your suggested 9.56;
In the other direction (let's say Y), we slot the holes as needed so that they allow for mounting two fans in a row.

That works for the requirements I had in mind initially:
1) mounting both 120/140 fans with two degrees of freedom and "some" granularity of positioning
2) mounting both 240/280 radiators with two degrees of freedom and "some" granularity of positioning
3) radiators only have to be mountable in one direction (but the direction has to be the same for both)
4) should work with regular fan screws (at least for fans) and regular radiator screws (for radiators)
4) openings have to be smaller than 12.5mm (ingress protection rating 2 for solid particles)
5) depending on the material, the minimum "wall" needed between holes varies. I'm working with 2mm for aluminum (2mm thick) and 1.5mm for "steel", but that's tentative! If you have other values please share.

A possible slotted design (slots are 5.5*12.5, pitch is 14.5):

I couldn't make it quite work yet for 280mm but it seems like with some adjusting it'd work

Yes, that is exactly right. The visual is good.

 

[Shatrod]

1. It is enough to neglect. Noctua officially states the pitch is 124.5.

2. Your math doesn't check out. You should always denote it as pitch, or center to center distance. 10 mm center to center (pitch) does not fit into 105 or 125 evenly.

If you mean that there is 10 mm of material between 5.5 mm holes, then your center to distance is 15.5. Which also doesn't divide evenly.

3. The technical term is clearance. You're correct on the clearance fitting, but your math from the previous point doesn't work out

You are correct my bad I got the math wrong. But after thinking about it some more 4mm diameter holes with 5mm center to center wishing in x and y should work? At 124.5mm spacing, you would need a screw at 0.25mm off center. A 3.5mm screw in a 4mm hole would have exactly this clearance.

The only draw back is you can't use fan screws any more, but you could still use 6-32 radiator screws with nuts on the back instead of a radiator (small sacrifice in my opinion).

I feel like I'm missing something... Let me draw this out and see if it works

 

[Thehack]

You are correct my bad I got the math wrong. But after thinking about it some more 4mm diameter holes with 5mm center to center wishing in x and y should work? At 124.5mm spacing, you would need a screw at 0.25mm off center. A 3.5mm screw in a 4mm hole would have exactly this clearance.

The only draw back is you can't use fan screws any more, but you could still use 6-32 radiator screws with nuts on the back instead of a radiator (small sacrifice in my opinion).

I feel like I'm missing something... Let me draw this out and see if it works

1mm isn't a whole lot of material width between holes. This leaves the part pretty weak and prone to deforming.

 

[Shatrod]

1mm isn't a whole lot of material width between holes. This leaves the part pretty weak and prone to deforming.

I respectfully disagree. This is made up for by there being a lot "interconnects" between the holes. One 1mm thin line would be weak yes, but 50 or so of them are absolutely not. If you were to make this out of steel especially there should be no concerns. Its like having a rope, the individual strands are weak but the weave of many is not.

Edit: you can also make up for a lack of strength by having a thicker panel. like 2mm aluminum. This should alleviate strength concerns

 

[arturbecker]

Thanks Shatrod!
As been posed by Thehack, this alternative fell just out of the design space I tried to optimize upon, because I put 1.5mm ~ 2mm as a minimum space between holes. But that was somewhat arbitrary, following the guidelines of my friend who will probably manufacture this for me. Maybe I can convince him to try out 1mm spacing?

 

[arturbecker]

Also I would preferably not create the need for custom mounting hardware (#6 screws also require nuts to go with them etc.)

 

[Shatrod]

Here is a DXF of the grid with two 120mm fans and two 140mm hole sapcing drawn out. its fully symmetric in X and Y. 105mm hole spacing with 15mm sapcing for a dual 120 rad and 124.5mm hole spacing with 15.5 mm for 140 dual all align in either X or Y. You will have to sacrifice compatibility with fan screws. this will only work with 6-32 screws or smaller with nuts or a radiator on the other end. I didnt realize you had a 1.5-2 mm minimum space requirement, sorry. Well ive come this far anyway would be a shame not to share.


This is the hole design: repeat with 5mm center to center in X and Y:

 

[arturbecker]

Awesome! I'm curious about why you didn't go with round holes?

 

[Shatrod]

Awesome! I'm curious about why you didn't go with round holes?

The arc does not work out and doesn't let a 6-32 screw go off-center far enough on a 45 degree angle

Edit: a picture is worth a thousand words. Highlighted segment is the conflict with just a 4mm round hole

 

[Shatrod]

if you want perfect circles you will need a min 4.207mm diameter hole which will leave 0.793mm of material between holes, a bit not enough especially if you want any kind of tolerances. It would probably be an issue for manufacturing even with a laser cutter

 

[arturbecker]

True!
By the way, do you think assuming 3.5 for the screw is enough? Consulting a clearance chart it seems "close fit" clearance for #6 is 3.6576

 

[Shatrod]

Eh I don't know. If anything maybe a metric m3.5 screw? I know you can use those with a 6-32 thread and they hold okay. Depending on your manufacturing methods maybe expand the hole by 0.05 for some tolerance. Would leave a 0.9mm metal gap between holes. Laser cutter can probably do that with reasonable precision.

Personally, I would try a test on a small panel. The screw might go in a little tight and rub the hole down, aluminum is soft

 

[Shatrod]

Sorry for double post.

Actually look at this. this is a 6-32 screw in a 120mm fan. There is a lot of tolerance. Like almost a whole milimiter. Presumably it would be the same for a 140 fan... So yes actually I'm sure it would work out because you don't have to center the screw with the fan hole either. Might be an issue for a radiator as it's threads are fixed spacing though.



Also not all screws are made equal. This is 6-32 from Lowe's.