Agreed - I wouldn't waste a nickel a foot for DOM tubing over welded, unless required by some irrational racing organization. I would specify "electric resistant welded" (ERW) type however, as allowed by the ASME code for pressure piping, without derating relative to seamless of the same material.
When I was Racing in the 60's & 70's I made my own Role Bar everybody said I went overboard with it I used 1/4" wall tubing & the only people that Could Bend it was a Bus Garage & they did a good job. Just my 3.5 cents Live Learn and Die a Fool
I know from purchasing metal in different cities that cost varies from place to place. Usually depends how far they are from the main supplier and their output on product. I’d call a few places may save yourself a few bucks. Also cut cost will put a dent in your pocket if you can’t transport a full stick. First cuts free after that is usually $5 per cut which adds up in my opinion. Some places will let you take a grinder or portable band saw and do it yourself. Sent from my iPhone using The H.A.M.B. mobile app
I bought 1.75 .120 wall DOM for my coupe, I stuck it on the steel order that a local machine shop does monthly. Ended up cheaper gettin DOM over the EW stuff, by quite a bit. Also the metal shops in my town think tubing is square and pipe is round, with no crossover.. so this was my best option. I had to order a minimum number of feet though.
Am I reading that right you used 1-3/4" tubing? And did a50Merc use 1/4" tubing? Metal is priced by the pound so 1/4" will weigh twice as much as 1/8" (sold as .120 or 11Ga.) and you pay for shipping by the pound. The size of the tubing is not as important as the design of the product and it's purpose. Pat
Yes, 1-3/4” 1/8” wall DOM. Not sure why anyone would go 1/4”. I built my frame crossmembers and roll bar with it, also built a bumper for my old truck with it. It’s probably the most common size used.
I'm sorry Fry I had a brain fade you are correct, my own roll bar is 1-3/4" x .134" as per NHRA but 1/4" is a little thick. Pat
I am upgrading the cage in my coupe to 12 point, with funny car cage. Will be getting it made by Auto weld. They are about a hour away from me. And they make a cage for the 1930 Model A.
New Age Motorsports installs what it calls the "half cage" in it's '32 5 window coupes. Entire car from beltline down has 1-1/2" x .120 wall DOM structure welded together. The floor plates capture the frame mounting holes so it all ties to the frame. All the hinges and latches are also tied into the steel structure. Really like it. SPark
mike if you go with chromoly it will save roughly 100 lbs. for what you do with your car its the way to go.
We are on the same page with that Brian. I have to keep weight to the minimum. I am a little concerned with getting in and out of the car, but I will manage.
Well... Yes and no. 4130 is just as heavy as any other type of steel, and it has the same stiffness. The difference is its higher breaking strength under tension. It bends just as easy as regular steel, it weighs the same, but in a construction where breaking strength under tension is the important factor you can reduce dimensions to save some weight when going with 4130. In another construction it may give no benefit at all, so it's not the magic upgrade a lot of people seem to think.
Actually 4130 does not bend as easily as regular steel because it has a lot more tensile strength and that is also the reason that the sanctioning bodies allow thinner wall 4130 compared to mild. In the street car application by the OP that is irrelevant and as stated above ERW is more than sufficient for what he is trying to do. DOM and 4130 are both overkill in his case as he plans only to drive on the street. That said, if he thinks that he may run it at a sanctioned track at some time complying with the rules of the appropriate sanctioning body is a good idea (although I have yet to see tech at the common street car/test and tune events require certification on genuine street driven cars that run slower than the roll bar/cage cut off levels) Roo
..I plan to used steel plates welded to the bars as needed and have them bolted to the frame,....Thanks to all for the info ..I now have a better view of what to do...thanks again Miller
Could do like this one "clown" I met and go with 2"PVC pipe!! Covered in foam rubber. He said in street rac'in saving weight is what its all about. No kidd'in!!....PVC 6sally6
Food for thought, I installed this roll bar in a '32- 2 Dr. Used 6" square 1/8" plates with 4- 3/8 bolts at the bases Two of the bolts are secured by nuts welded in the top of the frame rail, the inner two connect to a gusseted plate welded flush with the top of the rail. The car will be drag raced, and the owner wanted a legal roll bar, with removable side bars. It is ERW- .134 wall.
If the OP doesn't have the ability to notch and bend the tubing (which I suspected he doesn't), he would be far better off buying a "roll bar kit" from someone then makes a kit for his car. The "kit" is prebent, cut to length, and notched. Its ready to weld in. If he is just after the additional safety of the extra structure, I would go with the 1/2 kit someone mentioned earlier, but it doesn't give any roll over protection. Gene
....I had no way to know how much info there is out there and the info given by the members. ....I have a large pipe bender and my buddy is a welder.....As for pvc that is out.....once again thanks to all for the replies..miller
A "pipe" bender is not going to work too well with any sort of steel tubing. Pipe benders are meant for use with Schedule 40 (and other) types of pipe which is way softer (lower tensile strength) than ERW, DOM or 4130.. Tubing needs to be bent in a tight fitting die with some sort of follow block mechanism. Without those the end result is generally severe ovaling of the tube or kinking on the inside of the radius. Roo
Bending tube requires the right equipment. Coping or notching the tubes is not that difficult. There are apps on the web for patterns that wrap the tube or pipe for the notch. We built an air frame that was all 4130. The tubes were notched with a bench grinder and the fit ups were clean and tight. There were so many tubes to cope so it was started with a zipcut to rough cut the end angles. Slowly working the notches. mark the adjustments, grind until the fit is snug to the mating tube. It is easier to do the diagonal if one there is one tube to butt against then work the other end with a stub of the same size as the permanent tube. Then the tube that butts the other end of the diagonal can be set. It is easier this way than trying to work both ends of a diagonal between two fixed tubes. (IMHO)
...It appears it may be best to get a kit that has the hoop made and work from there... thanks miller
Years ago I used a piece of re bar bent as template for the main hoop, did the same for the side and rear bars. Took it it in to our local race car fab shop, they bent it up with .134 tube and it fit pretty well.
You can do a fairly decent mock-up with PVC and get it to a bending house or racecar fab shop. For the corners, use 2-45* to simulate the larger dia radius bends, they can figure it out from there
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