New Metal Tech Cage

[LT]

Well this past weekend Mark and I started on my new cage. It's the standard family cage kit, I used to have his first ever profile cage! It had the profile cage with the stock roll bar and the front A pillars were made out of e.r.w.

So after all those weekends of me going up and helping bend, cut, grind, and package tube we finally came out with this. I personally bent up the B and C pillars, the A to B brace, the B to C brace, the center over head bars and the over head bars on the B to C.

Stock cruiser tube on the left and d.o.m. on the right. Mark measured out the stock cruiser tube thickness and it came out to something like .072

New trick way of using the stock roll bar seat belt mounts with the new cage

New rear mounting system, all laser cut and using 4 stock roll cage mounts with an additional rib to make the mount extra stout

New A pillar mounts with 6x6 holes and the exact same plate for underneath for the front frame tie.

 

[LT]

And now to the cage Yes it has two different colors military brown and black. I'm going to do a camo theme but due to time restrictions we just spray painted the cage as fast as we could.

This picture turned out funky, the handle are not this squished.

This show how the A pillar wraps around the dash board.

 

[Mace]

Why is ERW (sp?? hrew??) a big deal???

Nice cage/mounts BTW

 

[LT]

The difference between E.R.W. and H.R.E.W. is how they are made. There is a huge seam on the e.r.w. making it structurally worse and the h.r.e.w. is electronically welded and has a very small seam. Mark can chime in about it, that's about all that I remember from what he was telling me.

 

[Mace]

Electric Resistance Welded (ERW) Tube
ERW is the most economical and readily available type of mechanical tuning. It is produced by taking a flat bar of steel and rolling it into a tube shape (picture rolling up a newspaper - but without any overlap) and then welding the seam - by, you guessed it - electric resistance - hence the name. Electric resistance welding is somewhat like a long, continuous spot weld. It's often computer controlled and extremely consistent. ERW is normally SAE 1010 (for wall thickness < 16 ga) or SAE 1020. ERW tube comes in 2 flavours:

Hot Rolled ERW (HREW)
HREW is rolled into a tube at elevated temperatures, usually way above room temperature. This produces a tubing that is more malleable and therefore easier to form but that is also not as strong, is supplied covered with scale, and not as uniform in dimension as cold rolled. It is also quite a bit cheaper than cold rolled.

Cold Rolled ERW (CREW)
CREW is manufactured by a process in which a steel bar is rolled into a tube and the seam welded, usually at room temperature. Compared to hot rolled, CREW is stronger - (greater yield strength) - because of the improvement in the crystal lattice structure from improved grain size, shape, and orientation imparted by being worked at cold (room) temperatures), straighter, has a much smoother and more uniform surface finish, and is made to much tighter, more consistent dimensions. It is the best economical choice for tube work, and because of the better surface finish and tighter dimensional tolerances it is much nicer to work with than HREW.

Drawn Over Mandrel (DOM)
Strong and well-finished DOM is an electric resistance welded tube tested for soundness of weld and drawn through a die and over a mandrel. This process imparts significantly improved mechanical properties to the tube, due to the cold working process. It is considered a high quality tube, and is normally constructed from SAE 1020 or 1026 steel. Note that, technically DOM refers to the process by which the tube is finished after having started as an ERW tube. Technically, DOM is not a type of steel tube, but rather a process. As so often happen though - in common use the term has become accepted to mean a specific type of tubing rather than a process. In this case, when people say "DOM" they normally mean an ERW tube drawn over a mandrel at (close to) room temperature and made from SAE 1020 steel. It is normally drawn to O.D. and I.D. dimensions. Here is what the Steel Tube Institute of North America has to say about DOM:

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. 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.[10]




ERW is for the most part fine for cages.. Dom is slightly stronger.. so it is a better material but not by much.. dom is ERW before it has been rolled over a mandrel for consistancy..

 

[SizzleChest]

can you still use a soft top with a cage like that?

 

[LT]

can you still use a soft top with a cage like that?

Yes, the B to C brace along the side is just inside the fast track railing for my Kayline soft top.

 

[SizzleChest]

Yes, the B to C brace along the side is just inside the fast track railing for my Kayline soft top.

cool, what about keeping the original rear seats?

 

[LT]

cool, what about keeping the original rear seats?

Don't think so... you might be able to drill through the mount to gain access to the stock holes. The rib might be in the way also...

 

[honk]

From the Metal Tech website:

Metal Tech is currently offering four choices of cage kits for the FJ40. All tubing is made in the USA, size 2" .120 wall HERW and 2” .125 wall DOM. These are kits, grinding and welding is required for final fit. All tube is cut to length with a small amount of extra material to allow for a custom fit

. http://metaltech4x4.com/products_cageframeset.htm

Hmm, the MetalTech website says that cages are constructed of both 2" .120 wall HERW and 2" .125" wall DOM. ERW tube is not mentioned.

You describe HERW as the least desireable of the three yet it is what we can expect to get, at least in part? Which part I wonder?

Something else: though you say that ERW tubing is just slightly weaker than DOM wouldn't the difference in wall thickness, with the thinner tube the weaker, add to the difference between the two making the .120 wall ERW tubing, if maybe that type is used and not HERW, more significantly weaker? Or...why discuss ERW tubing at all if it is not to be part of the Metal Tech cage which we might buy?

The fact that the site does not mention ERW at all but instead does mention HERW which you now tell us is the weakest lowest quality tubing of the three gives me pause to ponder. Is it that you are changing what tubing is to be used and haven't yet updated the site? Or has a misspeak occurred here? Or what?

I was just looking at the site a minute before coming here and finding this thread. I was there because I'm at a point where I'm ready to put in a cage and prior to finding thiese discrepancies there was no question in my mind as to whose cage it would be. Is it necessary to say that my interest is piqued?

I was going to ask these things privately but then decided that if there is misinformation here in the forum it's best to clear it up here in the forum.

 

[theo]

I have basically the same questions. I know Mark's products continue to evolve and I'm guessing it's just a matter of the website falling behind some. I also know MetalTech has a long-standing good reputation here, so I'm not worried that the kit I buy will provide enough strength to withstand a rollover. I plan to order a cage very soon and look forward to hearing more specifics.

 

[honk]

I have basically the same questions. I know Mark's products continue to evolve and I'm guessing it's just a matter of the website falling behind some. I also know MetalTech has a long-standing good reputation here, so I'm not worried that the kit I buy will provide enough strength to withstand a rollover. I plan to order a cage very soon and look forward to hearing more specifics.

Yeah, me too. I've been looking/watching for some time and it isn't hard to see that Mark is providing a quality piece of work which he'll back personally through any issue. My feeling is that this is a case of misunderstanding of the technical truths on the part of the help (just kidding, Weeny).

Nevertheless it IS important to anyone buying a safety related product that he or she trust that it has certain capabilities, and that that buyer know the limitations of the product if it also has those. When something like this happens it's hard to know what to think and there may well be people reading here who could go away with a very negative conclusion about the product under discussion.

So we need the horse's mouth here.

 

[helocat]

Greenweeny (AKA: Little Travis or LT for short) His first post here is mainly showing the (blurry as it is) the diference in wall thickness between what Toyota used for a stock roll bar and what Metal-tech uses for A pillars. The photo shows the sample chucks of tube I sent home with LT. The one on the left is OEM Toyota, thin stuff also ERW. The one on the right is from a Metal-tech A pillar DOM tube.

LT, HAD the very first Metal-tech cage ever made in his truck. My tube bending/welding overall fabrication skills have improved exponentially since this first cage was made almost 5 years ago. I wanted to chop it up and make him the most state of the art Metal-tech cage. (This guy has a reputation for rolling his truck anyway.) LT has also been helping me in the shop as I have gotten busier over the last year. So he earned it anyway!

New post on tube next…

Mark

 

[helocat]

LETS TALK TUBE! Coming from owning and operating an Aerospace Machine shop where we made parts for satellites and proto type military aircraft, I have learned the value of material properties/quality. This goes beyond just calling up the local metal supplier and saying “gim’e some 2” tube”, receiving it and tossing it on the shelf mixing it in with what’s left of the last order.

First off not all tube is created equal, yet it may have the same formal designation! American Society for Testing and Materials (ASTM), is where the designations for materials comes from in the US. ASTM A513 is the category ALL welded wall tube falls into, hot, cold, DOM all of it. In fact there are a total of five classes just under this category alone.

All tube hot or cold start out as hot rolled. Cold rolled is just ran through another operation cold, this gives it a nicer surface finish. Tolerances between the two? Yes anytime you heat metal it’s going to move around a bit. There is where the manufacturing tolerances come in, if it moves too much its scrap. Stays in tolerance its still ASTM A513 tubing.

Mace’s description of HREW is a good one for a wide generalization for ANY hot rolled made steel product. (Look at the mill scale on your average angle iron!) You can find this in the tubing world when you are talking structural tube like 4” 3/8” wall and so, basically big stuff typically used in construction. For the stuff we use in roll cages, we dont want this kind of stuff! So we call out tighter manufacturing tolerances and finish quality. In the case of Metal-tech you are getting ASTM A513 1018 (1020) PO. The PO stands for pickled in oil to give it the smooth clean surface finish.

WHY NOT CREW SOUNDS LIKE GOOD STUFF? First off most steel mills will not make tube out of cold rolled with a wall thickness above .083”! Sure it can be made and sometimes it is for a special order. You might find 2” .120” wall CREW as left over from a large run for a large customer, but no one will stock it. BUT WHY!? Because the overall properties are so close to HREW. So close in fact most CREW is made with on the very same equipment and dies HREW is made.

[size=+2]It really boils down to just how quality the tube was made and the tolerances it was ordered with. [/size] ERW and HREW is quite the same stuff. Typically ERW is the bottom of the bottom of the barrel stuff with terrible tolerances. (Wall thickness, quality of steel used, huge flash inside on the seam, some with flat seams! Some seams with porosity in the weld!) But it is not always the case.

Metal-tech’s tube:

100% of Metal-tech’s tube is made in the USA. I will not touch the stuff of the boats. Yes I pay more, yes its harder to get, but the consistent quality is far superior. The concentricity, steel quality, weld, and surface finish the list goes on. But on top of it all it has the ASTM data to back it up and a paper trail back to how it was made. By buying steel from a few select mills/distributors exclusively there is little deviation batch to batch.

If you have any questions please let me know.

Mark

 

[haystax]

When are you gonna build some sliders? I'm getting bored and need to weld some more steel to my junk

 

[71-CRUISER]

Mark,

I think some people are confused by the fact that your site states that you use DOM as well as HREW in youe cage kits. When mine arived the 2 A-pillar pieces looked significantly diferent that the rest of the tube (color wise, a little more oxidation, could have been bent and stocked and the rest of the stuff could have been newer). I assumed that the A-pillars were DOM and the rest was HREW. Please correct me if I am wrong. Either way the kit was exactly what I expected even with the modifications that I asked for. For a DIY kit I dont think you caould ask for more.

Thanks for making such a good product available for us.

 

[LT]

The front A pillars are DOM and the rest (B pillar, C pillar, B to A brace, B to C brace, over heard bars, etc) are HREW unless someone requests that they want DOM bent for the other pieces.

 

[helocat]

Mark,

I think some people are confused by the fact that your site states that you use DOM as well as HREW in youe cage kits. When mine arived the 2 A-pillar pieces looked significantly diferent that the rest of the tube (color wise, a little more oxidation, could have been bent and stocked and the rest of the stuff could have been newer). I assumed that the A-pillars were DOM and the rest was HREW. Please correct me if I am wrong. Either way the kit was exactly what I expected even with the modifications that I asked for. For a DIY kit I dont think you caould ask for more.

Thanks for making such a good product available for us.

Yes. The A pillars are made out of US made 1020 2" .120" wall DOM tubing with a 15-20% elongation requirement on my material standards. The elongation gives the tube yield should it take a hard hit. Basically it is more likely to deform vrs. Crack and catastrophically fail.

The front A pillars are DOM and the rest (B pillar, C pillar, B to A brace, B to C brace, over heard bars, etc) are HREW unless someone requests that they want DOM bent for the other pieces.

All A pillars are DOM at the advertised prices already right now. DOM can be used for the rest of the kit for the additional cost of the material. Typically $100-150 more depending on the configuration.

Why use the two types of tube? Same reason all fighter jets are not made exclusively out of titanium. Use the big $ material where it’s needed the most and use the best strength to cost material for the other areas.


Mark

 

[Mace]

This is why I did not like the "e.r.w." comment..

Mark builds awesome stuff. AND most cages for recreational use are made out of HREW...

 

[honk]

Yes. The A pillars are made out of US made 1020 2" .120" wall DOM tubing with a 15-20% elongation requirement on my material standards. The elongation gives the tube yield should it take a hard hit. Basically it is more likely to deform vrs. Crack and catastrophically fail.


All A pillars are DOM at the advertised prices already right now. DOM can be used for the rest of the kit for the additional cost of the material. Typically $100-150 more depending on the configuration.

Why use the two types of tube? Same reason all fighter jets are not made exclusively out of titanium. Use the big $ material where it’s needed the most and use the best strength to cost material for the other areas.

Mark

So there's an assumption that the A pillar would take a harder hit or heavier loading in case of a rollover? Or is it made of DOM because it's less heavily supported than the B (and possible C) pillars because of the need to allow occupant ingress/egress?