Looking for materials/crash course on certain compression clamps. 1

[Corey_]

I'm working on a project that would benefit from cheap tubing as a frame. However, I'm not too familiar with some of the methods of fixing them together.
I attached a basic view of the structure. Yes, made in paint, but it gets the point across I think.

Some examples of how I imagine it fitting together would use something like a clamp that fits around the tube and tightens with a couple bolts:

https://shop.flexpipeinc.com/us_en/hj-1-tee-joint-set

https://www.mcmaster.com/5723T83/

https://www.mcmaster.com/structural-tube-connectors/heavy-duty-clamp-on-framing-and-fittings/

My problem is that I'm not too familiar with this market/engineering.
Are there any standards that I should know/would be helpful to know?
And most importantly, are there equations for these fittings for how much they can hold.
As you (might) be able to see, a lot of the force is down, and runs along the length of one of the pipes. I'm concerned that this wouldn't support much weight.
I would like to see if they can hold up about 10 lbs and a bit of occasional vibration.
I might be dumb and am going in the wrong direction. Maybe there is some better material for this.

Edit: here is a better example

https://mlsvc01-prod.s3.amazonaws.c...-4ec3-b743-2f998deb6aeb.jpg?ver=1500980159000

 

[CWB1]

The info you're looking for should be in the manufacturer's (not McMaster or other dealer's) catalog. If you can't quickly/easily locate the appropriate catalog on their website then call or email and ask.

 

[Jboggs]

The options you've listed are very common, and work well for many BUT NOT ALL applications. In my opinion they are over-used and often fail for many reasons. The most common design mistake is in the assumption that those connectors provide any kind of torsional stiffness. They don't! It's an effect I call "parallelogram-ing". If your structure will carry any kind of significant load I would recommend a different approach. You might consider a system something like that offered by 8020.net.

 

[MJCronin]

I have never seen such a superb and high quality sketch in my lifetime ... Congratulations, sir !!

If I didn't know better, I would say that it was developed by someone with Delirium tremens, (also called DTs) or heavily Medicated ..

++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

Go to WalMart, buy some graph paper and draw your space frame TO SCALE with DIMENSIONS ...!!!

SCAN THE SKETCH AND RESUBMIT IT ...

INCLUDE PLAN AND ELEVATION VIEWS !!!

If you don't know what this all means, you should not be in the job that you seem to have...

I am 73 now and have been making these kind of scaled, dimensioned sketches since I was 15 ...

I am sure you can do it !!!

MJCronin
Sr. Process Engineer

 

[SWComposites]

MJC, LOL but I have seen worse. Sigh.

 

[EdStainless]

These clamps are very weak in the off directions.
Your frame will require cross bracing and redundant load paths.
And they do not tolerate vibration well at all.

= = = = = = = = = = = = = = = = = = = =
P.E. Metallurgy, consulting work welcomed

 

[Corey_]

The options you've listed are very common, and work well for many BUT NOT ALL applications. In my opinion they are over-used and often fail for many reasons. The most common design mistake is in the assumption that those connectors provide any kind of torsional stiffness. They don't! It's an effect I call "parallelogram-ing". If your structure will carry any kind of significant load I would recommend a different approach. You might consider a system something like that offered by 8020.net.

Do you happen to know the equations to equate bolt torque to joint holding strength?
Under normal circumstances it should just sit there. A very rare shock load is estimated at 800 lb-in in torque. I noticed structures like these, they seemed to hold up nicely:

@MJCronin, that image is all I can give, and is frankly even unnecessary. I'm just looking for conceptual stuff; I'll take it from there.

 

[TugboatEng]

And this is a safety issue. Drop one of those fixtures on a moving car and you can easily kill someone. I believe there are standards associated with these, anything you build must comply with the standards. What country are you building this in?

 

[3DDave]

Flexpipe is really inexpensive - you do need to use their pipe with their connectors. They appear to have no strength data but the cost risk is so low, just buy it and build it and see if it's sturdy enough.

I think the standard is - if it doesn't work right then call a welder to make a sturdy replacement.

Ordinarily one would have dimensions and how the structure is attached to the world and some idea of how the load would be applied to the structure in order to determine the required strength of the connections.

 

[TugboatEng]

Wind loads on these structures can be very high and will dominate any structural calculations.

 

[3DDave]

Only if that's what he's designing.

 

[Jboggs]

Here's the rest of your picture. With my comments.