Fixing to a Thru Hole - No Access

[PLo1984]

Hi Guys

I've got a good one for you. Have wracked my brains for a good solution, but can't find anything I'm happy with:

I've got a bank of 4 fans arranged in a square. Each fan has a flanged face with 4 through holes to attach it, one in each corner. When they are arranged in a square there is no access to fasten bolts to the 4 through holes left in the middle of the 4 fans (please see picture attached).

All the other(external) bolts are all screwed into a frame. The four thru holes in question are floating in mid air. Originally there was a small plate with PEM nuts in it that accepted long studs coming from the other side of the assembly. This secured the four fans together at the centre of the assembly, but is no longer an option.

I'm after a small plate that holds all four fans together, but i don't know how to attach it. I want to be able to dissasemble it, so push fits and glue are out. I don't want to modify the fan, so I can't drill or tap it, and the thru hole is 4.3±0.5mm, and not appropriate for threaded inserts, intererence fit dowels or self tappers.

Any help here would be great!!!

PS sorry if its unclear. Its hard to describe without pictures. Many thanks!

 

[PLo1984]

view file as a JPEG here:

 

[SnTMan]

Well, nice looking picture, but it doesn't give much of a clue as to the physical situation, constraints, etc. Maybe a sketch of some sort?

Regards,

Mike

 

[PLo1984]

Yeah, fair point, was tring to keep it light.

Think I've cracked it now anyway Thanks for your time..

 

[SnTMan]

Of course, glad to help

 

[kingnero]

So, how did you solve it? rivnuts?

 

[PLo1984]

Small plate with PEM studs in, and the dowels on the mating component on the far end. ALthough I can't actually use this solution now.

Dunno what Riv nuts are? Will google them when I revisit the problem..

 

[Muatam]

you could have used a small clip nut to attach it to the plate. then, you could just use a longer bolt to hook into it. The advantage with those is that you have some wiggle room to take up for any tolerance issue and you can replace them if the threads get boogered up any.

 

[MikeHalloran]

To install a bolt within a blind hole:

Grind the plating/dirt off the bolt's point, down to bare metal.
Tin the point.
Solder a few inches of solid copper wire to the point, with the axis parallel to the bolt axis at the solder joint.
Leave a nice ball of solder around the wire, but don't let it foul the threads.
Use the wire to manipulate the bolt into the blind cavity, then assemble the retained hardware and the nut.
In this particular case, insert the bolts from inside the flanges before joining the quad of fans, and tie off the wire until you've got the fans positioned, then thread the joiner plate over the four wires, then the nuts.
Pull on the wire to position and hold the bolt while wrenching the nut.





Mike Halloran
Pembroke Pines, FL, USA