welding chromemoly tubing?

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Old 11-14-04, 05:33 AM
LimaBlu
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welding chromemoly tubing?

I'm looking into buying a Lincoln Electric Handy Core welder (35-88 amp. output) and I want to build a go-cart whose plans requires 1 1/8" x .083 wall aircraft spec. chromemoly tubing. Can I weld this with the mentionned welder ? In case this influences the answer, I also need to learn to weld! Thanks.
 
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Old 11-14-04, 06:47 AM
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I'm not an expert when it comes to chromoly, someone else may have a better answer. However, most bike frames are either TIG Welded or Braze Welded (Oxy Fuel setup). I'd assume you can MIG weld it to but, you'd need a machine that could do a better job.

That Lincoln Electric Handy Core welder is pretty light duty and according to Lincoln; 70 AMPs the duty cycle is 20%. Duty cycle is the length of time you can weld during a 10 minute period. Therefore 20% means you can weld for 2 min, stop welding for 8 min and then resume welding, and so on.

What type of go-kart is this going to be and does it have to be chromoly?
For example, my neighbor built his 2nd go-cart out of 1" x 1" x 1/8" mild steel using his Lincoln 225 AC Stick welder. He threw on a chainsaw motor and it hits about 30MPH.
 
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Old 11-14-04, 08:11 AM
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Wink

If you mean 4130 tube I use Oxy-acetylene all the time on a airframe.

ED
 
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Old 11-14-04, 01:25 PM
LimaBlu
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The go-cart is going to be a fun off-roader type and 30mph is about the maximum speed I expect. The autors of the plans I'm using (mxk racing) do not recommend the use of mild steel. Since I do not know better, I was planning on using the Chromemoly 4130 as suggested. I guess the issue now is, is Chomemoly really required?

I now understand the 20% duty cycle issue and how it relates to time of use(still learning every day !) and I first thought, this doesn't bother me a whole lot since I'll be using this occasionnally as a hobby. If this is too light an animal for the job than that's another issue.

I'd appreciate more advice...
 
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Old 11-15-04, 09:36 AM
LimaBlu
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Here's Lincoln Electric's official response:
"Chrome-moly requires an 80,000 psi tensile material which requires the solid wire and gas process. Your machine is not capable of running shielding gas and, therefore, would not handle this application."

I guess I'll stick to mild steel. If the frame bends or breaks, I'll repair it!
 
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Old 11-15-04, 11:17 AM
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LimaBlu ,

The reason the plans call for a particular material is that when considering the design strength, the inconvenience of repairing a broken frame is not what they are concerned about.
What they don't want is a piece of the frame to snap off in the event of an unfortunate incident, and make its way into the captain's quarters.

If you are not already familiar with working with metal then straying from the plans is not too good of an idea.

There are two aspects to welding that are completely different disciplines.
Welding and fabrication go hand in hand but you can be good at one and not the other.
An example of this is a good friend who worked in a mine as a licensed welder for 6 years.
He would be stuck in a giant ladle for days on end, pouring in literally tons of rod, or welding cracks in overhead crane mechanisms. He was highly skilled in his element. He had a welder at home but brought his small projects to me.
Problem was he never had the opportunity to figure things out on his own because the company had a team of engineers who specified every minute detail of his work.

So, what I'm saying is that there is more to this than meets the eye.
Be safe and follow the plans or buy a premade frame to work with.

I would encourage you to buy a welder, but first find a project that is less demanding.
 
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Old 11-15-04, 11:44 AM
LimaBlu
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I understand the advice and it sounds wise (I can relate your example to my line of work too). Please don't get me wrong, I'm not trying to second guess anyone (if I had all the answers I wouldn't be requesting help). That being said, within the present thread and in another set of plans I purchased, mild steel tubing was suggested.

I was ready to pay more for the chome-moly tubing and thought the strength issue was a plus. Given my light weight (150lbs), relatively slow forecasted maximum speed (30MPH), is chome-moly tubing really required ? The site suggesting this tubing indicates that the cart can accommodate a 260lbs person. Surely the cart won't undergo the same stress levels with me at the wheel. Doesn't a company selling plans necessarily choose the ultra-safe avenue it limit exposure to lawsuits or is this tubing the way to go?
 
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Old 11-15-04, 11:58 AM
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Most companies are covering their own butts. They give you the highest grades of material to work with. Sometimes this is overkill. As in your case. Most Chromemoly I have worked with (piping in a refinery) had to be preheated and Tig root pass and then 8018 stick rod the rest of the way out. Good luck with your project.
 
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Old 11-15-04, 05:22 PM
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LimaBlu,

I can see that by you comparing plans and questioning the ones that call for mild steel, you should be able to reason through the merits of each set of plans.
I would call this diy engineering.

I'm sure that by carefully studying the mild steel plans you could increase the strength of the stucture by some carefully placed gussets and braces without increasing the weight too much.

To answer your original question, I believe that for general purpose use, a mig welder that comes with the gas kit would be the most versatile.
As far as the Lincoln welder you are looking at, I would suggest you get something bigger, that would would not have you frustrated with the low duty cycle that this one has.
 
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Old 11-16-04, 05:20 AM
LimaBlu
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What do you suggest as more acceptable specs? Do you have a model to suggest?

thanks.
 
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Old 12-25-04, 11:43 PM
Mnuvsteel
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Lincoln 3200 HD

This welding machine should be more than adequate for any welding job that you'd ever face around the house and most likey any of the most common tasks in industry as well:





Lincoln Electric
Weld Pak 3200HD Wire Feed Welder
Model K2190-1



Lincoln Electric's Weld-Pak 3200HD handles a huge spectrum of flux-cored or MIG welding jobs -- from auto-body repairs to farm fixes to around the home chores. It comes ready to weld mild steel with self-shielded flux-cored wire right out of the box. Also included is virtually everything you need to MIG weld mild steel. Just add a cylinder of shielding gas. There is mild steel procedure chart inside the wire access door guides you to all the appropriate welder settings for the job at hand. It has a 25-135 amp output and welds up to 5/16 inch steel using flux-cored wire. The unit plugs into a 120V (20 amp) outlet. And they cost about $450






Now that might be a little much but if you are looking for a unit that will do flux cored or gas shielded welding and has an extremely wide range of applications then this one is a machine you'd prolly never out grow. They also make a smaller and cheaper model (about $350 ) its Lincoln's HD 100 pak. now they don't mention it being able to handle applications useing shielded gas but it will. You have to buy the guages and hoses for it seperately and in doing that, well obviously you'll spend the hundred bucks in the difference in price. I'm a big fan of Lincoln machines I've always used one and never had any problems with them so I don't mind suggesting them to someone thats asking. Good luck and have fun.
 
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Old 12-26-04, 01:04 PM
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Will it come apart with a bad result?

There are people who weld because they make money doing it and there are folks like myself who simply own some welding equipment.
Things that move (airplanes, cars, trailers, go-karts) or could fail with tragic loss of life (bridges, towers) are projects that I avoid when someone proposes them to me just because I have the equipment.

How many trailers or go-karts would I ever build? Probably just one.
Why go through a long learning curve (mistakes and all) for something that I only need one of?
It's a strong case for purchasing a used frame and assembling the other components.
 
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