Mounting methods for thin wall cast aluminum

[nidershan]

Having a cast Aluminium enclosure with the 3mm wall thickness. now I need to mount this to a mounting plate which fixed in vertical walls. can I have some idea on how should I choose the appropriate fastener?

1. Cast Aluminium enclosure
2. mounting plate, for now, I have placed a 5M countersink bolt

Enclosure can't be changed. this mainly mounts on the railroads it should withstand 20g RMS shock. this is the only way I found to mount the enclosure to the plate since I have to maintain the water-resistance. and have to mount vertically.

Total enclosure weight around 800g

my worry is thread engagement and how can select the way to mount.

Thanks in advance.

 

[rb1957]

I wouldn't tap cast Al. How about a barrel nut ? ... slide down inside the "tube" ... small flange to stop it falling too far.

Or blind rivet (maybe "pop" rivet in your world) ? ... maybe need a small hole on the opposite wall (for the stem, on installation).

another day in paradise, or is paradise one day closer ?

 

[btrueblood]

You've drawn what looks like a typical Al-Zn diecast enclosure...but without any draft. Are you sure that wall does not have a taper angle relative to the sealing/lid plane?

Agree with rb1957, the die cast material is thin and would likely only engage a couple of threads on the fastener. Drill through the wall and add a nut and washer on the inside wall of the enclosure? Why are you drilling through what looks like a screw boss?

 

[tbuelna]

Barrel nut.

https://www.lisi-aerospace.com/wp-content/uploads/2019/04/Barrel-nuts-1.png

 

[TugboatEng]

A well nut should do the trick.

 

[GregLocock]

No nails.


Cheers

Greg Locock


New here? Try reading these, they might help FAQ731-376

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[CWB1]

I would find some available space inside the box then poke as many holes as necessary through the wall. A standard bolted joint analysis will dictate the number and size of fasteners, as well as the size (large) of bearing/washer area you need. Water-resistance can be maintained via any number of sealing washers or sealants. The biggest issue as mentioned will likely be casting draft.

 

[3DDave]

I was forced into using one of these in a military application - spent far more engineering money working around the weaknesses and flaws from the low-strength material, the tapered sides, and the overall fixed size, and the poor mounting options, and still had to do a bunch of machining to be useful than was ever saved being "off the shelf" rather than just milling out a block to do the task.

But the project guy was convinced this was the way to go. Sunk cost fallacy, no doubt. The decision was already made and he refused to change his mind.

 

[dik]

Can you use adhesives? or does it have to be removed at some time in the future?

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[hydtools]

Use an adhesive(I understand Gorilla Glue is tough.) or double sided adhesive tape.

Ted

 

[dik]

There are much better adhesives... Also can you drill through the web between the vertical 'holes'; there may be more material for threads even if the 'holes' expose the threads.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[TugboatEng]

I'll have to double check the numbers but 3M DP805 is an excellent mounting adhesive. It's an acrylic adhesive rubber microspheres to control the adhesive thickness and give it impact resistance. It's very similar to the adhesive used for stud mountain systems. The cure to 75% time is minutes so you can simply hold items in place as it cures.

 

[Sparweb]

For all of those who said "adhesives" above, re-read the OP. They said this was being used by a railroad.
I would not expect the field techs will adequately clean the surfaces to expect these things to stay bonded with +/-20g and environmental exposure for very long.

I would go for barrel nuts - you will have to just fabricate your own. Thankfully it is not hard to make dozens of them in a "gang" and cut off segments. Also consider a "L" bracket on the bottom (non-lid) side which you can fasten to the superstructure and the bottom face, which is flat and has no draft angle.

Please remember: we're not all rednecks!

http://www.sparweb.ca

 

[TugboatEng]

We have been using adhesive mounts with very good success in marine applications. Here is an 80lb charger we mounted using 2" studs.

 

[dik]

The installation can be pristine... I've used adhesives in mining conditions, maybe less pristine... might be that railroads still like to use rivets still. Adhesives can work.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[TugboatEng]

The manufacturer of the studs in my picture also has shock rated mounts that have a rubber damper built in for military type applications.

 

[Sparweb]

That's a click-bond. Not a bad idea, and better installed than what I had in mind from the OP's project.

Please remember: we're not all rednecks!

http://www.sparweb.ca

 

[FACS]

I wouldn't tap cast Al. How about a barrel nut ? ... slide down inside the "tube" ... small flange to stop it falling too far.

This is the best idea.
One barrel nut can even have two or three holes for the other screws.
Using adhesives just creates another set of assembly instructions and reduces ease of service.

"Don't weld it, don't paint it, don't glue it... unless you don't have a choice."

 

[mfgenggear]

in aircraft there is a reason they use rivet type of fastening, and the style Rivet is important. blind fasteners were access is restricted, there are many styles and types.
edit: consider riveted nut plates with a liberal clearance hole for the fastener.

 

[hydtools]

We routinely drilled and tapped A356 aluminum
castings. The thread depths were 1 to 2 diameters deep.
Must flathead capscews be used? Only one in a bolt pattern will fully seat unless all are match drilled at assembly.

Ted