Fabrication questions

[RussMcB]

Two (or three) questions regarding how to make certain tube frame joints:

1. What do you call those joints often seen on formula cars that are like short tubes with a washer welded on one end?

1b. Are they available for purchase from anywhere?

2. What are the steps to create a bolt hole in a square tube that will not crush when tightened. I think it involves inserting tubing, but I'm not sure how it becomes a flush surface. Maybe it's as simple as grinding the weld flat after the tube is inserted and welded in place?

Thanks. I'll elaborate if the questions don't make sense.

[Mike Devins]

Russ,

To make the parts that you are taking about I turn them on the lathe and drill and couter-bore to depth. I would advise that you make sure that the counter-bore has a small radius in the corner do reduce the possibility of a crack starting. I also have seen some of these made by simply welding a waser / plate to the bottom but I would not do this any where you have high loads.

I do not know of any place to buy these commecially, but any local machine shop can make them for you. Call me if you can not find a source.

As for adding bulk heads into square tubing I have done exactly as you described. Works fine as long as you get good penetration during your welding.

Mike Devins
Hurley Racing Products
586.623.3055

[superbikestore]

Not sure about the first item but in a square tube weld in the round bolt tube needs to be slightly longer then the size of the square tube tube (so it sticks out a bit each side) - weld all around, grind carefully flat (need to be very flat as this is the clamping surface of the joint) then drill out the tube you welded in as it will either distort slightly or have some weld inside it. Use a washer each side of the joint bigger than the tube diameter and it will be a good solid mount.

David

[Dennis McCarthy]

try http://chassisshop.com/

[R. Pare]

Buckets are always best if machined from solid stock, as Mike stated. Welding a washer to the end of an open tube is not really all that good if it is expecting much stress. With the machined bucket, you will get a totally homogeneous piece ( no voids from suspect welds), plus you can thicken the end to whatever you need to get the strength required.

For bolting bosses in square tube, you will want to flange one side to catch the other 2 walls if the boss is going to experience much axial loading. The flange will spread the load to all 4 walls and prevent diaphraming of the 2 walls that the boss goes through.