DOM tubing versus 4130

[rbregn]

I will be building a motorcycle frame for sreet and strip use. I have a MIG welder, but no TIG welder. I have some one who would TIG it for me if I wanted, but I prefer to do it all myself. What are the benifits and drawbacks of using one over the other? The bike will be Harley powered with 120HP.

 

[sprintcar]

I would use 4130 DOM, TIG welded, machine fit each joint as close as possible - this way you'll live to tell about it if you have to corner it hard.
You can get away with 'plain DOM' and MIG weld it as long as there aren't any high loads, like braking, that aren't accounted for in the frame design. I did design work at HD and saw what frames really go thru - they either have to be flexible enough to absorb the loads (Softail) or strong enough not to flex (Dyna series) - and resist the twist generated by cornering.
Most of the aftermarket frames flex - and no one cares since they rarely see 15,000 of lifetime mileage.

Keep the wheels on the ground
Bob
showshine@aol.com

 

[MaxRaceSoftware]

I would use 4130 DOM, TIG welded, machine fit each joint as close as possible - this way you'll live to tell about it if you have to corner it hard. --Bob


Like Bob posted , fit each joint as exactly close as possible , keep cone clean and tungsten clean and sharp
Clean all joint areas near welding , lightly sand and clean if you have to . Continually keep tungsten sharp .

You could also ;
drill small 1/16 hole thru tube , so gas pressure that might build up from welding heat can be released , then after joints are welded , maybe go back and spot-weld holes

i would TIG the frame instead of MIG

Larry Meaux (meauxracing@mindspring.com)
Meaux Racing Heads - MaxRace Software
ET_Analyst for DragRacers

http://www.mindspring.com/~meauxracing/

Support Israel - Genesis 12:3

 

[rbregn]

Thanks. Tig it will be

 

[butelja]

Larry's post reminded me of something that is done in aircraft construction using tube framework. Specifically, I've seen in on ultralight helicopters, where fatigue is a life and death concern.

Every place 2 tubes intersect, a small hole is drilled in the main tube where the other tube branches off. Pressure can be communicated between every tube in the structure. A schraeder valve (tire valve stem) is installed on 1 of the tubes, as well as a pressure gage and the entire structure is pressurized to a small (~15 psig) pressure. ANY cracked weld will result in a loss of pressure, and notify you to inspect the structure. The crack will be easy to find, as you can re-pressurize the structure and brush soapy water on the welds, looking for bubbles.