I have an option to buy a roll cage made out of 1.75" mild steel. Or
for about 30% more, I could get the same cage out of 2" DOM.

To be honest, I'm not sure what the letters DOM even stand for.
What's the difference? Is this worth the extra price?

I'm sure thicker tubes are better, and I suspect there is something
special about DOM metal that makes it stronger than non-DOM... but if
the 1.75" mild steel will do the job, there's no need for overkill...
is there?

 

"Joshua Nelson" <spam_box@ev1.net> wrote in message
news:b102b6e4.0307291151.1320a6f0@posting.google.c om...
> I have an option to buy a roll cage made out of 1.75" mild steel. Or
> for about 30% more, I could get the same cage out of 2" DOM.
>
> To be honest, I'm not sure what the letters DOM even stand for.
> What's the difference? Is this worth the extra price?
>
DOM = drawn over mandrel.

I don't think the mild steel will provide much of benefit should you
actually need to use it. That is, in a roll over, you want the roll cage to
still be there when the dust settles, mild steel will not hold up.



> I'm sure thicker tubes are better, and I suspect there is something
> special about DOM metal that makes it stronger than non-DOM... but if
> the 1.75" mild steel will do the job, there's no need for overkill...
> is there?

There is no need to not overkill. This is a place where overkill might save
your life. Spend the money.

 

Drawn Over Mandrel

http://www.metal-matic.com/dom.htm

--
Carlo F. Serusa, Jr. RPh
carlo.jr@comcast.net
'98 Sahara TJ - '89 YJ - '79 Scout II
O|||||||O
'92 Explorer '65 Mustang


"Joshua Nelson" <spam_box@ev1.net> wrote in message
news:b102b6e4.0307291151.1320a6f0@posting.google.c om...
> I have an option to buy a roll cage made out of 1.75" mild steel. Or
> for about 30% more, I could get the same cage out of 2" DOM.
>
> To be honest, I'm not sure what the letters DOM even stand for.
> What's the difference? Is this worth the extra price?
>
> I'm sure thicker tubes are better, and I suspect there is something
> special about DOM metal that makes it stronger than non-DOM... but if
> the 1.75" mild steel will do the job, there's no need for overkill...
> is there?

 

DOM stands for "Drawn over Mandrel". I think the stuff starts out as bar
stock, gets welded into a tube, hardened and then pulled over the mandrel
( a rod ). I can't remember if the last bit happens when hot or cold - I
think cold.


Dave Milne, Scotland
'99 TJ 4.0 Sahara

"Joshua Nelson" <spam_box@ev1.net> wrote in message
news:b102b6e4.0307291151.1320a6f0@posting.google.c om...
: I have an option to buy a roll cage made out of 1.75" mild steel. Or
: for about 30% more, I could get the same cage out of 2" DOM.
:
: To be honest, I'm not sure what the letters DOM even stand for.
: What's the difference? Is this worth the extra price?
:
: I'm sure thicker tubes are better, and I suspect there is something
: special about DOM metal that makes it stronger than non-DOM... but if
: the 1.75" mild steel will do the job, there's no need for overkill...
: is there?

 

Hi Joshua,
I'm curious as whom actually calls their bars a Roll Cage for
litigious reasons.
Drawn Over Mandrel: http://www.ioportracing.com/faq/rollbar.htm
God Bless America, ßill O|||||||O
mailto:-------------------- http://www.----------.com/

Joshua Nelson wrote:
>
> I have an option to buy a roll cage made out of 1.75" mild steel. Or
> for about 30% more, I could get the same cage out of 2" DOM.
>
> To be honest, I'm not sure what the letters DOM even stand for.
> What's the difference? Is this worth the extra price?
>
> I'm sure thicker tubes are better, and I suspect there is something
> special about DOM metal that makes it stronger than non-DOM... but if
> the 1.75" mild steel will do the job, there's no need for overkill...
> is there?

 

"Joshua Nelson" <spam_box@ev1.net> wrote in message
news:b102b6e4.0307291151.1320a6f0@posting.google.c om...
> but if
> the 1.75" mild steel will do the job, there's no need for overkill...
> is there?


Depends who is in the Jeep when it rolls...
td

 

L.W.(ßill) ------ III <----------@***.net> wrote in message news:<3F26EEC8.E04013FD@***.net>...
> Hi Joshua,
> I'm curious as whom actually calls their bars a Roll Cage for
> litigious reasons.


The 2" DOM cage is offered by Essentially Off Road.

http://www.essentiallyoffroad.com/cages/jeepcjcages.htm

It is plainly advertised as a roll cage.

The 1 3/4" cage is offered by a local guy working out of his garage,
but he has a good reputation locally.

 

substitute "overkill" with "rolloverkill"....bigger is better..

Joshua Nelson wrote:

> I have an option to buy a roll cage made out of 1.75" mild steel. Or
> for about 30% more, I could get the same cage out of 2" DOM.
>
> To be honest, I'm not sure what the letters DOM even stand for.
> What's the difference? Is this worth the extra price?
>
> I'm sure thicker tubes are better, and I suspect there is something
> special about DOM metal that makes it stronger than non-DOM... but if
> the 1.75" mild steel will do the job, there's no need for overkill...
> is there?

 

The most important consideration you should consider is HISTORY of
successful resistance to collapse in any design you choose. Ultimate
tensile and yield value numbers are of SECONDARY or lower importance per
se.
The most probable failure mode of a roll cage will be by what an
engineer would term "buckling failure". Buckling failure is prevented by
using components of the "largest" cross section, using 'lots of
triangle' & lots of gussets, etc. A high strength material that is not
adequately supported (by triangles/gussets,etc.) will collapse just as
fast if not well designed geometrically.

Without getting into the complex mathematics of buckling failure....
simply choose the design that has the HISTORY of proven service, has the
largest diameter/cross section of components, has the most triangular
supports/shape, socket welds for the tubing connections, support
gussets, etc. Mild steel is totally OK if the design is well done, 2" is
better than 1.75; 3 inch is better than 2", etc. Stay away from designs
that have long unsupported spans of tubing. The more triangles and
gussets, the better. Long radius curves are better than tight curves.
The most important consideration vs. buckling failure is: shape and
geometry.... not tensile/yield strength.

Get the HISTORY of the design!!!!



Joshua Nelson wrote:
> I have an option to buy a roll cage made out of 1.75" mild steel. Or
> for about 30% more, I could get the same cage out of 2" DOM.
>
> To be honest, I'm not sure what the letters DOM even stand for.
> What's the difference? Is this worth the extra price?
>
> I'm sure thicker tubes are better, and I suspect there is something
> special about DOM metal that makes it stronger than non-DOM... but if
> the 1.75" mild steel will do the job, there's no need for overkill...
> is there?

 

> For an unproven/undocumented design: choose thick/beefy, with lots of
> 'included' triangles, etc. .... OR choose a design that closely imitates
> one that is definitely known to "work well".

Turns out the wall thickness on the 1.75" pipes is .134, while it's
only .120 for the 2" pipes, so I may be better off with the smaller
ones anyway.

Of course, this says nothing about design... if I knew enough about
metalworking to design my own, I wouldn't need to hire out the job in
the first place. But I don't, and I have neither the cash nor the
desire to personally crash test a number of designs... so I guess
I'll just go with what looks and feels solid to my eye.