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Debate: Cromoly vs. mild steel cage?
Topic Started: Nov 25 2011, 10:58 AM (4,651 Views)
black83zee
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>Cromoly is so much more expensive than mild steel...is it worth it? I know it's lighter...but I think mild steel is stronger. Also, it's not that much lighter, right? I think a mild steel 8 point cage is about 100 lbs.? Am I right?
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charged355
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Moly is lighter n stronger. But quite expensive. Worth it if your chasing every tenth
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Custom Forged 355 / Solid roller cam/valvetrain / Victor Jr heads / Hurricane Intake/ Accufab 1250cfm Throttle body / MegaSquirt 3 Engine Managment/ 1000cc SouthBay Injectors/ 7.6:1 CR / 4" Custom Single Exhaust / 4000 Circle D Stall/ CK Performance Billet 4L80 FMVB Trans Brake / 3" Chromoly Driveshaft / Full UMI Tubular Rear Suspension / Moser/Strange 9" / 4:11 gears Detroit Locker / Sumped LS1 gas tank / A1000 Fuel pump / A1000 FPR / Paxton Fuel filter / -10 Fuel line -8 return / Borg Warner S475 Turbo @10psi/ JGS 50mm WG & 56mm BOV / PA Racing Complete Tubular Front End Kit With Coilovers / Full Autometer Dash / Custom Black Suade Guts / Built by yours truly/ Tuned by George the EFI whiz

http://www.youtube.com/channel/UCnxlPhzRElZYM5YE-n2NRUw
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MCMLXXXIIIZ28
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NHRA rules say to use a mild steel cage .120 thick for all cars going 11.99 and faster. If mild steel is cheeper and you are not chasing every tenth like doc said, I would use mild steel.
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black83zee
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Yea....also $$$!

Anybody know the actual weight differences?

>Ok..found my own answer: They weigh the same...except because of CM's strength they can use thinner walled tubing..so the same structure weighs less....the weight savings is about 30%.

>Found this cool write-up...could be a stickie?
________________________________________

Default Mild Steel vs. DOM vs. Chromoly Cages
Well, I did some research for those who want to know the difference and here ya go...

Mild Steel
Carbon steel is sometimes referred to as 'mild steel' or 'plain carbon steel'. The American Iron and Steel Institute defines a carbon steel as having no more than 2 % carbon and no other appreciable alloying element. Carbon steel makes up the largest part of steel production and is used in a vast range of applications.

Typically carbon steels are stiff and strong. They also exhibit ferromagnetism (i.e. they are magnetic). This means they are extensively used in motors and electrical appliances. Welding carbon steels with a carbon content greater than 0.3 % requires that special precautions be taken. However, welding carbon steel presents far fewer problems than welding stainless steels. The corrosion resistance of carbon steels is poor (i.e. they rust) and so they should not be used in a corrosive environment unless some form of protective coating is used.

Advantages


Cheap
Wide variety available with different properties
High stiffness
Magnetic
Most carbon steels are easy machine and weld

Disadvantages


Poor corrosion resistance (i.e. rusts)
Possible failure at seam under severe impact

DOM
"DOM
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.



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."


Chromoloy
Chromoly is like steel on steroids. It contains Chromium and molybdenum a splash of carbon and mostly iron.

The most popular grade of chromoly tubing is 4130. Here is what 4130 means: The American Iron and Steel Institute (AISI) has a numbering system that uses 4 numbers to categorize steels.

The first number indicates the major alloying element.

Take 1010 plain carbon steel, for example. The 1 denotes plain carbon steel. The second number indicates the approximate percentage of the major alloying element. In the case of plain carbon steel the number is a zero because there is no major alloying element. The third and fourth numbers indicate the carbon content of the steel.

In the case of 1010 steel They indicate that the steel contains approximately 0.1% carbon, that's 0.1% or point one percent carbon.

OK lets look at 4130 chromoly.

The 41 in 4130 indicate the main alloying elements are chromium and molybdenum and that the steel contains about 1% chromium and molybdenum combined. The last 2 digits indicate 0.3% carbon.

The reason 4130 chromoly is so freakin strong and the reason it performs so well when used in airplanes, bicycles, dragsters, etc. is because the combination of chromium, molybdenum, and carbon, along with proper normalized heat treatment , give 4130 chromoly tubing a combination of strength, toughness, and ductility.

4130 chromoly tubing has great properties and great strength to weight ratio. The trick is not to screw that up when you weld it.

There are some purists out there who insist that gas welding is the only way to go for welding chromoly tubing for small airplanes. The idea is that the slow heating and slow cooling that is part of the gig with gas welding, is necessary and when 4130 tubing is gas welded, it kind of gets stress relieved at the same time.

But with all the data available on TIG welding 4130 chromoly tubing without the need for stress relief in enough for me to feel good about TIG welding it. Even for small aircraft

I just make sure to only weld within established guidelines and I don't use 4130 filler rod.

Read more: Mild Steel vs. DOM vs. Chromoly Cages - SXS411.COM - #1 SXS/UTV Informational Forum
Edited by black83zee, Nov 25 2011, 01:44 PM.
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charged355
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Good find Stan, planing on a cage, I think I'm gonna bite the bullet in the spring before I hit it with my transbrake
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Custom Forged 355 / Solid roller cam/valvetrain / Victor Jr heads / Hurricane Intake/ Accufab 1250cfm Throttle body / MegaSquirt 3 Engine Managment/ 1000cc SouthBay Injectors/ 7.6:1 CR / 4" Custom Single Exhaust / 4000 Circle D Stall/ CK Performance Billet 4L80 FMVB Trans Brake / 3" Chromoly Driveshaft / Full UMI Tubular Rear Suspension / Moser/Strange 9" / 4:11 gears Detroit Locker / Sumped LS1 gas tank / A1000 Fuel pump / A1000 FPR / Paxton Fuel filter / -10 Fuel line -8 return / Borg Warner S475 Turbo @10psi/ JGS 50mm WG & 56mm BOV / PA Racing Complete Tubular Front End Kit With Coilovers / Full Autometer Dash / Custom Black Suade Guts / Built by yours truly/ Tuned by George the EFI whiz

http://www.youtube.com/channel/UCnxlPhzRElZYM5YE-n2NRUw
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klowny
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Da Klownfather
When In doubt .. Chrome molly
I have a chrome moly drive shaft and all my suspension is chrome molly tubing..luv it!



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black83zee
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'bout time Alex...with those ponies under there I'm surprised that unibody hasn't twisted up into a pretzel by now! ....Not only unibody, but T-Tops too???
Edited by black83zee, Nov 25 2011, 04:21 PM.
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350, carb, headers, side exhaust, T-5, aluminum ds, Baer discs, Bilsteins, tubular a-arms,
tubular torque arm, adjustable track bar and control arms.



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klowny
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Da Klownfather
Wait till he hooks..KaBOOOM babeeee



Check out my thirdgen videos and technical how to vids...from basic car maintenance to Performance mods..
subscribe (its free to subscribe) and you will be updated on future projects:

https://www.youtube.com/watch?v=6HO-D0aIgx8

https://www.youtube.com/watch?v=mIx1TqfXt6A

Thanks!
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charged355
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Yeah what saves it is that it spins when the boost comes on even with my 12.5 wide slicks, at the track and with a tbrake things might get tricky, that's why I put lexan tops on to the glass ones don't shatter under twisting
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Custom Forged 355 / Solid roller cam/valvetrain / Victor Jr heads / Hurricane Intake/ Accufab 1250cfm Throttle body / MegaSquirt 3 Engine Managment/ 1000cc SouthBay Injectors/ 7.6:1 CR / 4" Custom Single Exhaust / 4000 Circle D Stall/ CK Performance Billet 4L80 FMVB Trans Brake / 3" Chromoly Driveshaft / Full UMI Tubular Rear Suspension / Moser/Strange 9" / 4:11 gears Detroit Locker / Sumped LS1 gas tank / A1000 Fuel pump / A1000 FPR / Paxton Fuel filter / -10 Fuel line -8 return / Borg Warner S475 Turbo @10psi/ JGS 50mm WG & 56mm BOV / PA Racing Complete Tubular Front End Kit With Coilovers / Full Autometer Dash / Custom Black Suade Guts / Built by yours truly/ Tuned by George the EFI whiz

http://www.youtube.com/channel/UCnxlPhzRElZYM5YE-n2NRUw
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BlackMagic
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I don't really see the need for a moly cage unless you just like spending money or like Alex said straight up finished and chasing every last oz. of weight or every last unit of power. I have a 5pt of Mild steel .120 sitting in the shed, I wanted to put it in this year but I don't need it yet. I will probably hold off for now.

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notagain
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still leaking =-)
my 90's gt freestyle pro performer is 4130 c.m. held its shine and integrity for over 10 years while the steel forks are not only slightly warped but there rusting at the welds...while the frame still shines..... "chrome dont get you home but atleast it shines" saw that on a sticker
ok just figured id share all that
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black83zee
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notagain
Nov 26 2011, 12:20 AM
my 90's gt freestyle pro performer is 4130 c.m. held its shine and integrity for over 10 years while the steel forks are not only slightly warped but there rusting at the welds...while the frame still shines..... "chrome dont get you home but atleast it shines" saw that on a sticker
ok just figured id share all that
So Dave...you were doin' 9's on 2 wheels? lol
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350, carb, headers, side exhaust, T-5, aluminum ds, Baer discs, Bilsteins, tubular a-arms,
tubular torque arm, adjustable track bar and control arms.



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gp90gta
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The Professor
One other thing to remember is that cromoly has to be tig welded.
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notagain
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still leaking =-)
black83zee
Nov 26 2011, 06:57 AM
notagain
Nov 26 2011, 12:20 AM
my 90's gt freestyle pro performer is 4130 c.m. held its shine and integrity for over 10 years while the steel forks are not only slightly warped but there rusting at the welds...while the frame still shines..... "chrome dont get you home but atleast it shines" saw that on a sticker
ok just figured id share all that
So Dave...you were doin' 9's on 2 wheels? lol
:lmao:
i was running 11's
hey thats 10 years of city stair gaps and bethpage dirt jumps.. :rock:
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MCMLXXXIIIZ28
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notagain
Nov 26 2011, 12:20 AM
my 90's gt freestyle pro performer is 4130 c.m. held its shine and integrity for over 10 years while the steel forks are not only slightly warped but there rusting at the welds...while the frame still shines..... "chrome dont get you home but atleast it shines" saw that on a sticker
ok just figured id share all that
I had the same type of bike. My freestyle bike never broke on me, but I have snapped a few chrome moly frames racing frames in my days.
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