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  • Gaslight
    replied
    Check out the chopperhandbook site, they have info on pipe vs ERW and DOM. I think at a minimum there are difference in finish, which affects the surface that is picking up the load, like a stress riser, and there is a difference in tensile strength, and the care put into the welds, in terms of minimum standards, but that's just what I am carrying in my head.

    You can find mills for as little a 10 bucks, and buy a dedicated metal lathe for 700, you end up with a good coping set-up. Another good option is a beaumont metal works belt sander with a small wheel kit tunned for the tubbing size you grind. That thing will swallow coping, and you can grind out a sword in your spare time, a lot more versatile.

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  • snow
    replied
    Hi Paul....Yeah, steels have a numerical designation......the first two digits represent the classification, 10 is for low cabron steel, the second set represents the mid-point of the carbon content.....the actual percent will vary a bit from batch to batch.....

    I only mentioned using the ERW for the front and rear clips for those who are on a tight budget.....I prefer to use the DOM throughout for all my 1 3/4 and 1 1/2 tubes......then use the ERW for the smaller tubing used as braces and brackets........

    Example, for a streetstock or modified type chassis......I would use 1 3/4 095 wall DOM......then for the front and rear clips use 1 1/2 083 wall DOM...........and use 1 1/4 ERW for diagonal braces in the clips.......

    But Again...... Most sanctioning bodies have specs on the materials and design.....One really needs to check the rules carefully before building........

    As far as coping the tubing...........Mittler Bro's Ultimate tubing notcher is the way to go......But it is pricy......over 4 grand by the time you buy some cutters and tax.......

    It is bascally just a motor with a gearbox and a chuck thaqt holds an end mill.......the tube is clamped in a vise......set the angle you want and in just a few seconds, you have a perfect cut........

    The edges need de-burred......I use a 2x48 sander to clean those up.......really is a fantastic set-up......

    There are various holesaw type notchers.......you often see those on E-bay.........these work ok for limited use.........

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  • paulrbrown
    replied
    Snow, thanks for the clarification. When you refer to 10/10 or 10/20 are you meaning 1010 and 1020 low carbon steel with .10% and .20% carbon. Good point on the ERW for non critical areas to reduce cost. How do you prefer to cope your tubing? Thanks again, Paul

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  • snow
    replied
    Thanks Paul and Mr. Seaman.......

    I build chassis for a living.....such as it is....lol For the most part, there are three materials commonly used.........(by professionals, that is.....)

    ERW, DOM, and Chrome Moly.....each have thier benefits and drawbacks.....each have thier place, and, places where they should not be used.

    There are many companys that sell roll cage kits......(a web search will turn up several).......Most of the companies are selling the kits made of ERW tube...........With thousands of these kits out there, I cannot say that they are unsafe...........However, most will up grade the material to DOM for the differance in price.....DOM is better in all aspects, but it costs more.....

    DOM is generally considered "seamless"........it that one cannot see a seam........the drawing process makes it of uniform thickness throughout......the ERW tube thickness will vary somewhat.......

    Of commonly available tube, the ERW tube will often be of 10/10 material, the DOM will be of 10/20..........a strength difference of about 20,000 psi.......
    The DOM cost more.....But it is worth it.......

    A fairly good compromise for a streetstock type car would be to use DOM for the center section and use the cheaper ERW for the front and rear clips.......

    One really needs to check the rules though......Some specify tube type and thickness, and design of the cage.....

    Wish you all a Merry Christmas

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  • paulrbrown
    replied
    Go to this site, it has tensil strengths for different alloys of DOM, makes a lot of sense....Paul

    http://www.ptcalliance.com/dom/grades.asp

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  • hankj
    replied
    Hey Paul,

    Nice job. Thanks for taking the time. I learned a LOT from the discussion.

    Merry Christmas, y'all!

    Hank

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  • paulrbrown
    replied
    [B]Hey Kids, found some more info, hope this makes since....
    The DOM Manufacturing Process

    The manufacturing process for DOM tubing begins with coils of steel, which are slit to the proper width for the desired tube size. The strip is cold formed and passed through an electric resistance welder which joins the edges together, under pressure, to complete the tubular shape. After testing the weld's integrity, the tubing is cut to length for further processing.

    The cold-drawing process creates a uniform, precision product with substantially improved tolerances, surface finish and tensile strength, increased hardness and good machinability. In this process, the tube is cleaned and annealed, and one end of each length is squeezed to a point so it can be gripped by the drawing mechanism. The tube is then drawn through one or more dies and over mandrels (see drawing). This reduces the diameter of the tube and thins its walls to the required dimensions in a controlled fashion to provide the qualities desired in the finished product. Metallurgically, drawing improves the tube's concentricity, tensile strength, hardness and machinability. Close dimensional accuracy is achieved through tight control of both outside and inside diameters.


    Drawn Over Mandrel (DOM) refers to high-strength, electrically-welded tubing that has been further processed by cold drawing through dies and over mandrels to improve its uniformity, mechanical properties and surface finish. To a great extent, DOM tubing is customized to each specific application. This provides further advantages, particularly to high-volume manufacturers. They include a wider range of sizes and tighter dimensional tolerances that allow the tubing to be used in mechanical parts with little or no metal removal or machining. Because of its many advantages, DOM is the material of choice in many of the most demanding applications for tubing, including: hydraulic cylinders, auto and truck components, recreational vehicles and others.

    Will post more upon discovery,Paul

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  • snow
    replied
    I stand corrected. Thanks. I guess I should be more careful in my choice of words.

    Yes, of course, every piece of steel that is made, is made to some spec.....and, that spec is available............Yes, pipe is used as a structural member in millions of applications.........Yes, there are many kinds and grades and sizes of pipe...............

    But what are we talking about in this thread??????? RACE CARS.

    My only reason for posting in this thread is to PERHAPS prevent someone from making a mistake that may cost somebody thier life.

    My advice is useless to ASKANDY.......He KNOWS how to build a race car. On this forum we have experts like Andy and HAWK......and there are people new to welding who need to know the meaning of T.I.G.........For every one member who posts, there are many who don't...........Many hobbiest welders out there coming here to learn something.............Thats what make the forum great..........

    I pray they don't lean to build thier car from pipe.........

    Typical situation, a hobbiest welder wants to build a race car.......needs to save all the cash he can.........goes to the local plumbing supply house or scrapyard and buys some 1 1/4 black pipe........builds a car.

    Now, the plumbing supply house or scrap yard can not give him the specs on the material other than the size...........and even if they could they are meaningless to him........He don't know the difference between 10/10 and 10/20........

    So perhaps I should have said the specs are not readily available..........whats the odds that a guy who is buying black pipe (to save money in the first place) is going to be willing to buy the specs??

    Simple fact is, many hobbiests simply do not know the differances between grades of steel......and the differances are huge.

    Again, this happens all the time...........I personally know of an instance where the pipe shattered......the drivers ribs were broken and his lung punctured.........he lived but others have been less fortunate.........

    If only one person will listen, and not make the same mistake, then I feel this is time well spent..........

    Merry Christmas to all

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  • JTMcC
    replied
    [QUOTE=snow]

    One can not find the spec for pipe listed (as you can with DOM) for a reason.......it was never intended to be used as anything other than pipe.......never intended to have any purpose other than the conveyance of liquid or gas.........

    I do not claim to know the composition of pipe.........it seems to vary alot from mill to mill......sometimes brittle, sometimes soft........ end of quote



    Pipe is used for structural applications every day. The design specs for the hundreds of different flavors and colors of pipe are readily available, at a cost. Just like they are for rolled structural shapes and just about everything made of steel.

    As for the composition of pipe, that's readily available as well, in fact most real piping jobs require mill reports. There are hundreds of pipe specs, and tube specs as well. Much tube is used in fluid/gas conveyance, just as much pipe is used structurally.

    There are probably more old wives tales circulating about pipe/tube than on most welding topics. Spread by people that don't know or understand the field.


    JTMcC.

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  • Paul Seaman
    replied
    Snow:
    Very good food for thought!Thanks

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  • paulrbrown
    replied
    snow, Very good point. Paul

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  • snow
    replied
    I hate to beat a dead horse........well, for that matter, I would not beat a live one either.........lol But opions were asked for, here is mine.........

    CircleBFab is not the first to consider pipe for roll cages, it has been done many times........sometimes with disasterous results........

    One can not find the spec for pipe listed (as you can with DOM) for a reason.......it was never intended to be used as anything other than pipe.......never intended to have any purpose other than the conveyance of liquid or gas.........

    I do not claim to know the composition of pipe.........it seems to vary alot from mill to mill......sometimes brittle, sometimes soft........

    I have seen "roll cages" made of pipe shatter and injure the driver..........Most rules specifically outlaw pipe.......

    Racing is a very dangerous sport. Crashes are not a question of "if", more like a question of when...........We minimize the danger by using time proven designs and materials............These designs and materials are usually specified by the rules...........No matter what we do, the accidents will happen..........

    What happens when someone is injured or killed and it is discovered that the chassis was built from inferior material????????? Bad things........

    Know this, the car you build today will eventually be crashed........and what you do today will determine how well the car protects the driver. Some ones life is on the line here............don't screw it up.

    It has been suggested that there is no harm in making the car stronger........ this is wrong.......perhaps DEAD wrong........All race chassis have crush zones.......areas of smaller tubing to absorb impact.......using heavy wall tubing in the areas will transmit too much force to the driver........The car won't have as much damage but the driver probably won't put in a good word for you with St. Peter as he goes through the gates..............

    Study the rules and design carefully.........Use only the best materials.......DOM is for race cars..........pipe is for water........

    There are places to save money........Roll cages is not one of them.......

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  • hankj
    replied
    Check this out.

    http://ourworld.compuserve.com/homep...s/techdata.htm

    If someone can figure out how to use the data, it's a good site. I haven't played with the charts and tables much - got to get out in the Gadget Garage and work on the new mantle lest the wife become irate!

    Hank

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  • CIRCLEBFAB
    replied
    Tubing

    I really appreciate all the replys guys. I talked with a tech guy for IHRA and he told me DOM or ERW mild steel was the only thing acceptable. I think you guys nailed it with the seams splitting on the schedule 40. Now I know. This was my first post and this sure seems like a great website. MANY THANKS JIM

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  • paulrbrown
    replied
    Just got this from Metalsdepot site

    [COLOR=DarkSlateBlue]WORKABILITY - Drawn Over Mandrel is a cold drawn electric resistance welded tube with all flash removed. Compared to structural pipe, DOM Round Tubing is produced to more exact OD and ID tolerances and better finishes without a seam. Ideally suited for a wide range of structural and bushing applications. Widely used in stressful applications requiring higher quality, uniformity, strength, and soundness.


    APPLICATIONS - Farm implements, construction equipment, racecar frames, motorcycle frames, automotive parts, off-road accessories, etc

    This is for what is called 'structural tubing' they also make structural tubing which is not DOM. Again, Hope this makes sense/helps, Paul

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