Joining perpendicular tubing

[NWChen]

Stupid question, how this construction method works eludes me. How do you attach a bolt into a piece of hollow tubing, with no gussets/welds? What is there for the bolt to hold on to? Is there some block within the tube that includes a threaded hole for bolts to pass through?

Pic of 610's 2013 chassis for reference. I'm looking at the transverse tubes and where they join with each side of the drivetrain.

[Mark McLeod]

The rods are threaded (tapped).
Sorry I misunderstood.
Certainly blocks filling the ends are easy, and could be spot welded internally.

[notmattlythgoe]

Originally Posted by Mark McLeod

The rods are threaded internally.

I think he's talking about the ladder rails going across the frame, not the standoffs on the sides.

[Joe G.]

If I recall correctly, 610 uses a kind of unusual method of doing this. They use three pressed roll pins in the plate to capture the tube geometrically in the corners, and in the fourth corner, run a length of allthread to pull the whole thing together while making it removable.

[NWChen]

Originally Posted by notmattlythgoe

I think he's talking about the ladder rails going across the frame, not the standoffs on the sides.

Yup, thanks though Mark.

Originally Posted by Joe G.

If I recall correctly, 610 uses a kind of unusual method of doing this. They use three pressed roll pins in the plate to capture the tube geometrically in the corners, and in the fourth corner, run a length of allthread to pull the whole thing together while making it removable.

Oh, I see that in their design tutorials. Is there another way of doing this kind of attachment?

[Mike Marandola]

Originally Posted by NWChen

Yup, thanks though Mark.


Oh, I see that in their design tutorials. Is there another way of doing this kind of attachment?

Here is a close up of the joint.

[Mr. Lim]

Originally Posted by NWChen

Yup, thanks though Mark.


Oh, I see that in their design tutorials. Is there another way of doing this kind of attachment?

Yes, McMaster-Carr sells tube insert nuts:
http://www.mcmaster.com/#steel-tube-...-nuts/=107gcqp

While they technically work, we had enough problems with them to move to the 3 roll pin + threaded rod solution instead.

I think they're okay for prototyping, but on a competition FRC robot they come loose too often.

Stupid question, how this construction method works eludes me. How do you attach a bolt into a piece of hollow tubing, with no gussets/welds? What is there for the bolt to hold on to? Is there some block within the tube that includes a threaded hole for bolts to pass through?

Not a stupid question at all. It took us a long time to figure out how to do this, and we still don't stop trying to improve on things like this.

Others have already posted info about how we did this above, and you mention you read our Design Tutorial which has the best description of this process available, but to answer your questions directly here:

How do you attach a bolt into a piece of hollow tubing, with no gussets/welds?
We drill 4 holes at the inside corners of the square tube. 3 of the holes have roll pins pressed in, and they help position the square tubing. The 4th hole is for a threaded rod that runs the entire length of the square tube. One of the bottom holes is usually used for the threaded rod so that gravity helps you position and line it up. Access pockets along the length of the square tube are helpful in case you need to manipulate the threaded rod. Often we put a Nylock nut on one end of the threaded rod, and a Keps nut on the other so that tightening and loosening doesn't spin the rod - you only turn the Keps nut. The 3 roll pins take the shear load, and the threaded rod holds the plate against the tube.

What is there for the bolt to hold on to?
Nothing but the plates. The threaded rod runs the entire length of the tube, so the only thing keeping it in place are the nuts on the ends of the rod.

Is there some block within the tube that includes a threaded hole for bolts to pass through?
No. Nothing is needed inside the tubes.