Attaching Tube Bumper

[thebearded1]

Alright looking to see what ideas you all have. It's always nice when people from the outside take a look with fresh eyes. I have an aluminum round tube i'm using as a rear bumper and I notched the frame ends for it to set into. What would be the best way to mount it you think? The bottoms will be welded up when I'm done. It's a pretty hefty piece that is 34" long and weighs 7 lbs


One thought was to cut a piece of flat stock to fit in the frame, drill hole for bolt and weld on the back side. Then insert the head end with the flat stock into the frame while bolted through the bumper and then plug weld that piece of flat stock to the frame. Highly accurate CAD drawing below. This would probably be the most secure but I feel like it's going to be tough getting the flat stock to line up and if those bolts ever get messed up that's going to be a PITA to replace them.


Other option was to use a small bolt down through the top of the frame and either tap the aluminum to thread the bolt into or try and get a nut inside the tube onto that bolt since the bolt would only be about 3" in from the end.

Thanks
Gene

 

[LongJohn]

Can you weld aluminum? I would weld two 1/4" thick straps with two threaded holes that could be bolted to the inside frame rails with button head bolts and cap the tube ends. That way the " bumper" would look like it was floating unless you really look hard.

 

[thebearded1]

Can you weld aluminum? I would weld two 1/4" thick straps with two threaded holes that could be bolted to the inside frame rails with button head bolts and cap the tube ends. That way the " bumper" would look like it was floating unless you really look hard.

I can not but my friend can. I will have to see if either of us have any aluminum stock that would work.

 

[thebearded1]

Only issue about welding is the tube is a wire splice and could be made of aluminum and copper or just aluminum and you can't tell visually.

 

[LongJohn]

When you get a weld puddle if it's not weldable you will know! If you want a bumper make it steel. More than likely unless the bucket looks like an off road vehicle the bumper will go under another car and the radiator or water pump will be your bumper.

 

[Spanky]

More than likely unless the bucket looks like an off road vehicle the bumper will go under another car and the radiator or water pump will be your bumper.

One thing in his favor: he's racing with other roadsters that will have similar ride height to his.

 

[thebearded1]

When you get a weld puddle if it's not weldable you will know! If you want a bumper make it steel. More than likely unless the bucket looks like an off road vehicle the bumper will go under another car and the radiator or water pump will be your bumper.

I figured it would be obvious if it wasn't weldable. I'm going to try coming up with a bolt on steel welding only solution as my friend has already done a lot for me lately and doesn't live really close.

This will be a rear bumper and mostly used for pushing if I need it on the dirt track. It will afford some protection on the street though as before there wasn't anything behind the rear axle. I will post some more photos in my build thread when I get a chance.

Hoping to run the new brake lines today then next week i'm mounting new rear shocks and a panhard bar. Lots of constant left hand turns and quarter elliptical rear springs don't go well together without one haha

 

[RodStRace]

What is the design of the bumper? To simply cap off the rail and look good, or to actually absorb some force?

EDIT: you answered as I was composing. You want it to actually work as a bumper.

I assume the rail is steel, so not a weld the two together.

If it is going to see bumping, I'd find a rectangular aluminum tube that slides into the rail, and cross bolt it thru the rail and the tube.
For additional strength, a steel tubing saddle extending off each side of the rail to cup the bumper. Just realize that a hard bump is going to impart force into the rail, shocking and deforming things.
Even 100 years ago, they understood that a bit of spring and deformation was good for mounting bumpers.
I would not use the aluminum as a rail cap, but instead use steel like the rails and mount the bumper using a spring design at least like the 20s chevy shown. Yes, more weight and more parts. But having some impact absorbing for a push bar is going to save the rest of the car from nasty shocks.

 

[thebearded1]

What is the design of the bumper? To simply cap off the rail and look good, or to actually absorb some force?
I assume the rail is steel, so not a weld the two together.
If just to look good, a tab at the bottom that has a bolt thru to a nutsert in the tubing.
If it is going to see bumping, I'd find a rectangular aluminum tube that slides into the rail, and cross bolt it thru the rail and the tube.
For additional strength, a steel tubing saddle extending off each side of the rail to cup the bumper. Just realize that a hard bump is going to impart force into the rail, shocking and deforming things.
Even 100 years ago, they understood that a bit of spring and deformation was good for mounting bumpers.

This is mostly to use as a push bar on the dirt track if needed and light protection. It's just exhibition track time so it's not going to see a lot of contact on the track. I may make one out of steel later and weld it on but this was a freebie and thought it would look good and serve its purpose. I know aluminum isn't as strong as steel but this thing is pretty thick, in the middle it's over 1/4" thick. Plus that can be the deformation or crumple zone leaving the two frame sections to destroy the offending vehicle.