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moly or mildsteel cage?
Posted By: Pleaz
moly or mildsteel cage? - 12/18/08 02:49 AM
Im having my mild steel cage taken out and replaced with a moly one. Does a moly cage go brittle after 4, or 5 years? Where a mild steel cage can last up to 15 years? If this is the case, ill just save my money. The weight difference cant be that much anyway. Im not sure if i should stick with what i got, or replace it.
Posted By: MR_P_BODY
Re: moly or mildsteel cage? - 12/18/08 03:00 AM
Quote:
Im having my mild steel cage taken out and replaced with a moly one. Does a moly cage go brittle after 4, or 5 years? Where a mild steel cage can last up to 15 years? If this is the case, ill just save my money. The weight difference cant be that much anyway. Im not sure if i should stick with what i got, or replace it.
No, a moly chassis does NOT turn brittle in 4 or 5 years
that BS. The weight isnt all that much lighter but
it is lighter, I dont have the numbers in front of
me what the difference is in a foot. Its up to you
weather you replace it or not, they do cost more
because its all tig welded, but a moly chassis is
more rigid
Posted By: Pleaz
Re: moly or mildsteel cage? - 12/18/08 03:09 AM
Thanks. Im just wondering if the extra money, is worth a little weight.
Posted By: 4404dart
Re: moly or mildsteel cage? - 12/18/08 03:12 AM
I'd do a moly cage. It will last forever, it's worth more if you sold the car. You can put the weight you save somewhere else, or just save the weight.
Posted By: Cab_Burge
Re: moly or mildsteel cage? - 12/18/08 03:21 AM
Quote:
I'd do a moly cage. It will last forever, it's worth more if you sold the car. You can put the weight you save somewhere else, or just save the weight.
I also agree with MRPBODY, the moly cage is stronger, safer, lighter and better in a crash, especially on a drag car. That being said NASCAR wants mild steel, probally because a lot of the good old boys do a lot of the work themselves in the lower, slower local race cars and they don't want them trying to weld chrome moly with a OX Acetelene torch 
Posted By: MR_P_BODY
Re: moly or mildsteel cage? - 12/18/08 03:27 AM
I also agree with MRPBODY, the moly cage is stronger, safer, lighter and better in a crash, especially on a drag car. That being said NASCAR wants mild steel, probally because a lot of the good old boys do a lot of the work themselves in the lower, slower local race cars and they don't want them trying to weld chrome moly with a OX Acetelene torch
I believe they use mild due to them busting up their
cars all the time and always replacing tubing and
they have a PILE more tubing in their cars plus
they have a pretty high minimum weight
Posted By: RobX4406
Re: moly or mildsteel cage? - 12/18/08 03:44 AM
Quote:
I also agree with MRPBODY, the moly cage is stronger, safer, lighter and better in a crash, especially on a drag car. That being said NASCAR wants mild steel, probally because a lot of the good old boys do a lot of the work themselves in the lower, slower local race cars and they don't want them trying to weld chrome moly with a OX Acetelene torch
I believe they use mild due to them busting up their
cars all the time and always replacing tubing and
they have a PILE more tubing in their cars plus
they have a pretty high minimum weight
Has to do with the tube absorbing shock loads. Moly being more rigid, transfers more load to the driver than mild steel.
Posted By: Dan Brewer
Re: moly or mildsteel cage? - 12/18/08 03:53 AM
I would rather wreck a car with a MS cage than moly any day.
I sure wouldn't cut out a legal ms cage to replace, It is only lighter because it is thinner wall tubing.
Posted By: Pleaz
Re: moly or mildsteel cage? - 12/18/08 04:01 AM
I have always heard that moly is twice as light, and twice as strong. That is why i wanted to make the change.
Posted By: Al_Alguire
Re: moly or mildsteel cage? - 12/18/08 04:09 AM
Not sure I agree with that statement..Here is a question you need to ask yourself. How fast do you plan to go with this car? If it is just a rollbar I dont see the added expense of it being Moly worth the hassle. I suggest you build whatever your budget will allow for the ET you are after. You may find after pricing it out that the money spent for a moly bar will be batter spent elsewhere. FWIW my car is a Mild Steel certed to 7.50...
Posted By: dillon383
Re: moly or mildsteel cage? - 12/18/08 04:10 AM
Molly and Mild weigh the same, it's just the fact the molly is stronger so you can use a thinner wall tubing and get the same or more strength.
Posted By: 72sat
Re: moly or mildsteel cage? - 12/18/08 04:10 AM
the only reason I would go to moly,is for certification.If your car can make the weight,and cert. for the class you want to run;then why spend the extra money.
Posted By: Al_Alguire
Re: moly or mildsteel cage? - 12/18/08 04:14 AM
Well if it is only for certification then unless you plan on running faster than 7.50 mild steel is fine.
Posted By: Pleaz
Re: moly or mildsteel cage? - 12/18/08 04:25 AM
My mild steel cage is only legal for 10.0. Im hoping to be in the 9s next year. So i thought i would just go with a new legal moly cage. I could just add on to what i have, but im sure the old part wouldnt pass. And i thought moly would just be safer. Thanks for the input guys.
Posted By: 604 Hemi GTX
Re: moly or mildsteel cage? - 12/18/08 04:26 AM
moly is more brittle, so wouldn' it be more prone to cracking or is that just a myth.
Posted By: MR_P_BODY
Re: moly or mildsteel cage? - 12/18/08 04:51 AM
Quote:
moly is more brittle, so wouldn' it be more prone to cracking or is that just a myth.
Why is it more brittle Its stronger with less flex
Posted By: Rapid588
Re: moly or mildsteel cage? - 12/18/08 05:41 AM
While it is true mild steel has a little 'give' to it, these top 2 examples of 10 second 'mild steel' cages gave way too much..... the top one was coming in on the driver and had already failed......
the second pic of a buddy of mines cage also was 'giving' and was a hairs breath away of crushing him when he got into a little (very little) antifreeze of another car that had just run.
It may be hard to see in these pics unless you can zoom in, but both these mild steel cages deflected WAY too much for safety.
This next moly caged car hit and went over the wall at Orlando and disentegrated, but the moly cage did not deflect at all and integrity of chassis was still 100% intact.
Posted By: Cab_Burge
Re: moly or mildsteel cage? - 12/18/08 06:43 AM
Quote:
While it is true mild steel has a little 'give' to it, these top 2 examples of 10 second 'mild steel' cages gave way too much..... the top one was coming in on the driver and had already failed......
the second pic of a buddy of mines cage also was 'giving' and was a hairs breath away of crushing him when he got into a little (very little) antifreeze of another car that had just run.
It may be hard to see in these pics unless you can zoom in, but both these mild steel cages deflected WAY too much for safety.
This next moly caged car hit and went over the wall at Orlando and disentegrated, but the moly cage did not deflect at all and integrity of chassis was still 100% intact.
A picture is woorth a 1000 words, these three speak volume of why all the Pro cars use chrome moly tubing in there cars. Weight and speed have a lot to do on the total impact loads, I would rather be a in a car(and I am) with a chrome moly bar or cage than mild steel any day that I'm in a crash
Posted By: LA360
Re: moly or mildsteel cage? - 12/18/08 12:10 PM
Quote:
While it is true mild steel has a little 'give' to it, these top 2 examples of 10 second 'mild steel' cages gave way too much..... the top one was coming in on the driver and had already failed......
the second pic of a buddy of mines cage also was 'giving' and was a hairs breath away of crushing him when he got into a little (very little) antifreeze of another car that had just run.
It may be hard to see in these pics unless you can zoom in, but both these mild steel cages deflected WAY too much for safety.
This next moly caged car hit and went over the wall at Orlando and disentegrated, but the moly cage did not deflect at all and integrity of chassis was still 100% intact.
Looking at that cage, a gusset to the windscreen bar and Door bar could have minimised that. It certainly does look worrying though. I can also see why certain builders use a straight bar from the door bar footing to where the windscreen bar joins the door bar.
AL....
Posted By: wildcargo
Re: moly or mildsteel cage? - 12/18/08 12:45 PM
Quote:
My mild steel cage is only legal for 10.0.
Is this something new 
Posted By: Pleaz
Re: moly or mildsteel cage? - 12/18/08 01:15 PM
I have an 8 point cage. My understanding is that you cant go under 10.0 .Is that wrong
?
Posted By: Scamp408
Re: moly or mildsteel cage? - 12/18/08 01:35 PM
I seem to remember that my moly 6 pt was 60lbs and the mild was 110lbs.In my opinion if your 6 pt mild was installed nice I would leave it and spend the money elsewhere.
Posted By: polyspheric
Re: moly or mildsteel cage? - 12/18/08 01:59 PM
And still this question is raised.
No, moly is not more rigid than mild steel. The elasticity of all steel alloys is almost identical (Young's modulus: 30 × 10^6 psi).
"I have always heard that moly is twice as light, and twice as strong."
No, moly is not lighter than mild steel, the weight difference is only 1-2% depending on the exact alloy. The reason it's lighter is smaller wall thickness - that's it.
No, moly is not twice as strong, it's about 30% stronger (not stiffer), and that's if properly welded and heat-treated. If the wall thickness is reduced to save weight the strenghs are about equal. You can have more strength with the same weight, the same strength with less weight, or some intermediate.
Re: "they don't want them trying to weld chrome moly with a OX Acetelene torch"
Guess how Reynolds 531 chrome-moly chassis (including Formula 1 back in the day) are built for road racing? That's right - gas brazed with a torch. Read Carroll Smith.
"both these mild steel cages deflected WAY too much for safety"
That's not what did it.
Posted By: MR_P_BODY
Re: moly or mildsteel cage? - 12/18/08 02:35 PM
Quote:
And still this question is raised.
No, moly is not more rigid than mild steel. The elasticity of all steel alloys is almost identical (Young's modulus: 30 × 10^6 psi).
"I have always heard that moly is twice as light, and twice as strong."
No, moly is not lighter than mild steel, the weight difference is only 1-2% depending on the exact alloy. The reason it's lighter is smaller wall thickness - that's it.
No, moly is not twice as strong, it's about 30% stronger (not stiffer), and that's if properly welded and heat-treated. If the wall thickness is reduced to save weight the strenghs are about equal. You can have more strength with the same weight, the same strength with less weight, or some intermediate.
Re: "they don't want them trying to weld chrome moly with a OX Acetelene torch"
Guess how Reynolds 531 chrome-moly chassis (including Formula 1 back in the day) are built for road racing? That's right - gas brazed with a torch. Read Carroll Smith.
"both these mild steel cages deflected WAY too much for safety"
That's not what did it.
And why do you say its not stiffer, it takes a significantly
greater force to bend it on a bender over the
mild steel?
Posted By: B G Racing
Re: moly or mildsteel cage? - 12/18/08 02:43 PM
From your first picture it is a prime example of improper installation.The piller bar is layed back way too far and is attached at the side of the halow bar.It should be attached at the underside of the halow to give any support.Many times an installer will try and follow the windshield and body contours which make the angles less effective for support.NASCAR uses MS cages for impact absorption(give)CM is lighter and harder and has little impact absorption quality.CM is more prone to break rather than bend.And because of it's hardness it will fatigue from twisting and loading in time.This is why prostock,top fuel and other classes constantly update their chassis.If you have ever seen a CM Chassis wrecked you will commonly see tubing breaking not at the welds but in the tube body.And also a good oxy/ecty welder can weld CM just as good as a good tig welder.A furthur note,with all the approved and new welding techniques CM can be mig welded to perfection,NHRA just doesn't allow it.They fear that that fitment would be compromised buy the ease of application of mig welding,where as you can't very well hide gaps with the tig process.Structural design, effectivness,fitment,weld and application are all important part of how you choose material and build a cage or chassis.
Posted By: Blucuda413
Re: moly or mildsteel cage? - 12/18/08 03:07 PM
It's easy to get a MS cage certed to 8.5. Spend the $10 and get a rulebook before you spend any money needlessly. At least 40% of responses to rules on here are in error.
Posted By: B G Racing
Re: moly or mildsteel cage? - 12/18/08 04:03 PM
And 75% of the cars brought into our shop for chassis and cage certification are structually deficient.It cost less to do it right the first time than for us to cut out and redo.
Posted By: Pleaz
Re: moly or mildsteel cage? - 12/18/08 04:10 PM
Thats exactly what i dont want to do. I want to do it right the first time. Thanks for the input.
Posted By: d7cook
Re: moly or mildsteel cage? - 12/18/08 05:41 PM
Another big difference is one car has a funny car cage and one doesn't. The FC adds a lot of strength. On my car the pillar bar hits the side of the halo but another bar triangulates from the front of the halo to the pillar. I agree the car that squashed was poor design.
I don't think a CM roll bar will suffer too much from cracks but a full CM chassis car will usually require crack repair at the end of every season.
Quote:
From your first picture it is a prime example of improper installation.The piller bar is layed back way too far and is attached at the side of the halow bar.It should be attached at the underside of the halow to give any support.Many times an installer will try and follow the windshield and body contours which make the angles less effective for support.NASCAR uses MS cages for impact absorption(give)CM is lighter and harder and has little impact absorption quality.CM is more prone to break rather than bend.And because of it's hardness it will fatigue from twisting and loading in time.This is why prostock,top fuel and other classes constantly update their chassis.If you have ever seen a CM Chassis wrecked you will commonly see tubing breaking not at the welds but in the tube body.And also a good oxy/ecty welder can weld CM just as good as a good tig welder.A furthur note,with all the approved and new welding techniques CM can be mig welded to perfection,NHRA just doesn't allow it.They fear that that fitment would be compromised buy the ease of application of mig welding,where as you can't very well hide gaps with the tig process.Structural design, effectivness,fitment,weld and application are all important part of how you choose material and build a cage or chassis.
Posted By: TrxR
Re: moly or mildsteel cage? - 12/18/08 06:17 PM
Now if this vehicle was going to be a street/strip vehicle that would see a fair bit of street duty would you recommend a MS or CM cage?
Thanks
Posted By: B G Racing
Re: moly or mildsteel cage? - 12/18/08 06:21 PM
either,if cost is the issue go MS.
Posted By: PS Arrow
Re: moly or mildsteel cage? - 12/18/08 06:27 PM
Bob,
How significant is the difference in cost?
Posted By: B G Racing
Re: moly or mildsteel cage? - 12/18/08 06:31 PM
material is almost 1and 1/2 Xs more than MS and labor is 50% more.
Posted By: PS Arrow
Re: moly or mildsteel cage? - 12/18/08 06:43 PM
Thanks Bob, that's good info for the budget minded, could also sway the decision one way or the other.
Posted By: W.I.N. Racing
Re: moly or mildsteel cage? - 12/18/08 10:46 PM
BG and polyspheric
Great job in properly explaining the "CM/MS Myth's"
Posted By: Quicktree
Re: moly or mildsteel cage? - 12/18/08 10:48 PM
Quote:
BG and polyspheric
Great job in properly explaining the "CM/MS Myth's"
Posted By: dizuster
Re: moly or mildsteel cage? - 12/19/08 12:12 AM
Comparing 1 5/8" x .118" MS vs 1 5/8" x.083" CM...
In that diameter and wall thk. the CM is 29% lighter then the MS.
However in a bending moment situation the CM see's 37% more stress then the MS because of the wall thickness difference.
Yes CM is stronger then MS as a material, but concider when putting a much thinner wall thickness on the CM, it takes away all it's material strengh advantages.
So looking at bending. If you take MS and CM at the sizes listed above. A simple case putting 1000 lbs on a cantilevered 10" beam, the MS would bend .111" while the thinner CM would bend .171"
That's over 50% more bending deflection on the CM!
Remember it's not all about the material strength, the wall thickness of the tube has a lot to do with it...
Posted By: dizuster
Re: moly or mildsteel cage? - 12/19/08 12:18 AM
[quote}
And why do you say its not stiffer, it takes a significantly
greater force to bend it on a bender over the
mild steel?
Excellent question. Chassis stiffness is a lot different then impact stiffness. During chassis stiffness, the cars chassis/cage don't bend far enough to take a permanent bent shape. The metal is still in it's elastic state, and returns to it's original shape after it's loaded. But a CM car as outlined above uses thinner material, so it automatically looses stiffness. The metal itself if they were both the same thickness would bend elastically in the exact same way.
The advantage to your point of CM, in an extreame case like a crash, the bars often bend past their elastic point. This is where CM is material superior. But like I mentioned above, the wall thickness pretty much negates the material property benifits. But to your point when greatly bending CM (like bending a roll cage), you can feel that extra effort to bend the CM. Specific material has a lot to do with it though. I know my DOM mild steel was an absolute pain in the a... to bend, more so then the CM that I've done...
So with MS you get a heavy rigid chassis when compaired to a CM lighter more flimsy chassis...
Posted By: Monte_Smith
Re: moly or mildsteel cage? - 12/19/08 12:35 AM
You brought up DOM tubing, problem is, 90% of people who use MS don't use DOM, they use cheap, welded seam MS. A well built DOM cage is as strong as anything else and DOM costs nearly the same as Moly. I personally used DOM on all my MS cages, but when I got to the point that I no longer MIG welded any cage, regardless of material, it made no sense to not use Moly. Makes the car lighter and worth more for resale. I don't care what the cert is, a Moly car will always bring more. I would not put MS in a new car period, but that's just me.
Monte
Posted By: B G Racing
Re: moly or mildsteel cage? - 12/19/08 02:44 PM
Quote:
You brought up DOM tubing, problem is, 90% of people who use MS don't use DOM, they use cheap, welded seam MS. A well built DOM cage is as strong as anything else and DOM costs nearly the same as Moly. I personally used DOM on all my MS cages, but when I got to the point that I no longer MIG welded any cage, regardless of material, it made no sense to not use Moly. Makes the car lighter and worth more for resale. I don't care what the cert is, a Moly car will always bring more. I would not put MS in a new car period, but that's just me.
Monte
The cost of DOM(drawn on a mandral)MS to Aircraft quality CM is 1&1/2 times cheaper,we buy direct.Rolled and seamed MS is the cheapest tubing available.There are many different quality specs for either,varying the cost.We use DOM-MS and AC-CM for our custom chassis and cage work.We don't push our customer either way,we educate them on the pros and cons for their particular application and cost budget.We let them decide.Our 68 Cuda dbl rail/strut chassis car and our 65 Dodge a-arm car are both MS.We have 5 cars in the shop for up-grades,of the 5 three are MS and 2 are CM.4 of them are certified to 7.50.Go figure?
Posted By: Monte_Smith
Re: moly or mildsteel cage? - 12/19/08 07:31 PM
I don't push customers one way or the other either....but...as I stated, I TIG everything, MS or Moly. Here in this area, DOM is NOT that much cheaper than Moly, so, if you are only looking at a couple hundred dollars more for a Moly vs MS, what would you do Bob. You also have to consider my customer base. I do very little bracket type stuff and 25.5 is about the least spec we ever build. I also still maintain that Moly cars are worth more at resale and more desirable to potential buyers.
Monte
Posted By: CrAzYMoPaRGuY
Re: moly or mildsteel cage? - 12/19/08 07:42 PM
Quote:
RADICALLY different cage designs as far as I am concerned, and the material has less to do with these " crash effect" differences than the structural layout.
Posted By: B G Racing
Re: moly or mildsteel cage? - 12/19/08 07:51 PM
Quote:
I don't push customers one way or the other either....but...as I stated, I TIG everything, MS or Moly. Here in this area, DOM is NOT that much cheaper than Moly, so, if you are only looking at a couple hundred dollars more for a Moly vs MS, what would you do Bob. You also have to consider my customer base. I do very little bracket type stuff and 25.5 is about the least spec we ever build. I also still maintain that Moly cars are worth more at resale and more desirable to potential buyers.
Monte
I'am not dis-agreeing with you Monte.I'am just stating facts from my perspective.The majority of our work is bracket cars.You deal with a limited market like you stated,25.5 spec and up.I try to relate to the majority of people on the site.I think you agree that most adverage racers here,including me are not in your league.My comments and advice is for us regular kinda of racers.Sorry if you think I was stepping on your toes.I not worthy of that. 
Posted By: M_D
Re: moly or mildsteel cage? - 12/20/08 12:16 AM
The cage design in the above photo examples were different, and chances are the mild steel cars were heavier too. Also, even though they all went on their tops, it's hard to say exactly where and how much the forces actually were. So I don't think the photos prove much of anything regarding MS versus CM. Having said that, I have nothing agaist CM, in fact I am of about the same mind as Monte and personally TIG everything and use only CM for reasons he stated.
Posted By: jcc
Re: moly or mildsteel cage? - 12/20/08 12:53 AM
Quote:
RADICALLY different cage designs as far as I am concerned, and the material has less to do with these " crash effect" differences than the structural layout.
And most good design practices try to avoid "bending" in the first place, striving for just simple tension and compression forces thru triangulation, which negates much of the wall thickness advantages mentioned before. And most of these discussions usually result in those who are striving for crash protection, and the other camp striving for the most efficient and stiffess design, with the least material and lightest solution. Never ends.
Posted By: B G Racing
Re: moly or mildsteel cage? - 12/20/08 12:54 AM
As I said I agree with Monte also for the upper end type of cars that he builds he is absolutey correct.If we were responding soley to those type of racers.That clientale is not the norm at most race venues.They are regulate to Quick 16, and such.At any give race they are luckey to have a fast program.The super pro and pro classes number in the hundereds at most events.Monte and I are certainly not at odds here we just are preaching to different congregations.We certainly can respect what Monte does and probably wouldn't make a pimple on his butt at what he does.If asked I might be able to write a paragraph or two about what I know about N2O and I certainly won't try building any T/F,Pro-Stock or Pro Mods chassis in the near future or in my life time.But we do well at what we do and are willing to share our opinions and limited knowledge.
Posted By: Challenger
Re: moly or mildsteel cage? - 12/20/08 03:31 AM
Its all been some good reading here. A month ago my steel supplier the difference between DOM and CM was 40 cents a foot. He said he dont sell to much DOM anymore.
Posted By: Evil Spirit
Re: moly or mildsteel cage? - 12/20/08 03:51 PM
Quote:
I don't push customers one way or the other either....but...as I stated, I TIG everything, MS or Moly.
Monte
Im curious as to why M/S cages are TIG'ed. The test of a weld is that when you try to pull it apart, the material around it fails before the weld. Since a MIG weld has a larger radius than a TIG you end up with a larger surface area and (theoretically) a stronger weld. Is it for looks? A good TIG weld is usually nicer looking, but it is usually easier to get a MIG gun into the cramped areas, and you don't have to deal with trying to operate the pedal with your knee, etc. Keep in mind, I am asking this as an honest question; I know that you are a very competent builder and am not trying to insult you.
Posted By: go green
Re: moly or mildsteel cage? - 12/20/08 04:21 PM
With the MIG is a one shot deal .You start the weld and your committed to the end. Starts and stops are more noticeable . With TIG you can weld one inch.. stop..reposition yourself .. and proceed and it will look like a continuous weld.
The appearance of the MIG weld is just not as nice as a TIG weld , In the end result , everyone wants a tight and professional looking weld that you are trusting your life to.
Posted By: B G Racing
Re: moly or mildsteel cage? - 12/20/08 04:40 PM
Quote:
Quote:
I don't push customers one way or the other either....but...as I stated, I TIG everything, MS or Moly.
Monte
Im curious as to why M/S cages are TIG'ed. The test of a weld is that when you try to pull it apart, the material around it fails before the weld. Since a MIG weld has a larger radius than a TIG you end up with a larger surface area and (theoretically) a stronger weld. Is it for looks? A good TIG weld is usually nicer looking, but it is usually easier to get a MIG gun into the cramped areas, and you don't have to deal with trying to operate the pedal with your knee, etc. Keep in mind, I am asking this as an honest question; I know that you are a very competent builder and am not trying to insult you.
A few of us here at BGR can make just as nice a weld with a mig as they can with a tig.It's just a little bigger weld.MS cages are usually .135 thick so when you weld two pieces of .135 material you want at least .270+- of weld width and at least the same weld thickness of the the material .135+- at the crown.These specs are from the Steamfitters weld testing for power plants and pressure vessels. But then what in hell do I know,I was only certified in only 5 states for bridge and structural and heavy equipment modification and repair.I was a student of the late Art Livinston one of the best in the business.I didn't take the test for nucular power plants. 
Posted By: Evil Spirit
Re: moly or mildsteel cage? - 12/20/08 05:06 PM
Posted By: jcc
Re: moly or mildsteel cage? - 12/20/08 05:10 PM
Quote:
Quote:
Quote:
I don't push customers one way or the other either....but...as I stated, I TIG everything, MS or Moly.
Monte
Im curious as to why M/S cages are TIG'ed. The test of a weld is that when you try to pull it apart, the material around it fails before the weld. Since a MIG weld has a larger radius than a TIG you end up with a larger surface area and (theoretically) a stronger weld. Is it for looks? A good TIG weld is usually nicer looking, but it is usually easier to get a MIG gun into the cramped areas, and you don't have to deal with trying to operate the pedal with your knee, etc. Keep in mind, I am asking this as an honest question; I know that you are a very competent builder and am not trying to insult you.
A few of us here at BGR can make just as nice a weld with a mig as they can with a tig.It's just a little bigger weld.MS cages are usually .135 thick so when you weld two pieces of .135 material you want at least .270+- of weld width and at least the same weld thickness of the the material .135+- at the crown.These specs are from the Steamfitters weld testing for power plants and pressure vessels. But then what in hell do I know,I was only certified in only 5 states for bridge and structural and heavy equipment modification and repair.I was a student of the late Art Livinston one of the best in the business.I didn't take the test for nucular power plants.
Nice resume, but IMO you didn't answer his question.
Posted By: Evil Spirit
Re: moly or mildsteel cage? - 12/20/08 05:17 PM
The question wasn't directed at BGR - it was initially asked of Monty - he stated that he TIGs all cages, and I was politely asking why the preference of TIG over MIG. If it's for appearance, OK. If it's structural, how?
Posted By: Monte_Smith
Re: moly or mildsteel cage? - 12/20/08 05:51 PM
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The question wasn't directed at BGR - it was initially asked of Monty - he stated that he TIGs all cages, and I was politely asking why the preference of TIG over MIG. If it's for appearance, OK. If it's structural, how?
I would rather TIG a cage, mostly because of appearance. I don't care how good you are with wire, a TIG weld looks better than a MIG by far. The weld is small and clean, plus there is no splatter. TIG welding also requires very precise fits, which again, makes the weld and the overall cage look better. As I stated, if I do use MS, it is DOM .120 wall. I never use that thick .134 wall stuff, as it is heavy, plus the spec is .120, so why use thicker. DOM will pass every time.....I never said everybody needed a MOLY cage...all I said was that since I TIG everything anyway and Moly is barely higher than DOM, it made no sense for ME to use MS, even on a simple cage. If you are thinking it would cost more for me to put a cage in your car, than a lot of other people, you would be right. I never claim to be the cheapest at anything, nor do I wish to be. I am a one man show and high quality is very important to me. If someone does not want to pay the extra for me to do something, I fully understand and have no hard feelings if they take it somewhere else. That has never been a problem though, as my backlog of work is pretty large.
Monte
Posted By: Evil Spirit
Re: moly or mildsteel cage? - 12/20/08 07:23 PM
Yeah, Monty, TIGed cages usually do look better, due to the better fit necessary and the quality of the welds. I was just curious as to your earlier post. I probably get involved with about 1-2 cages a year; I'll fit and tack them together and have someone more "ergonomically friendly" (100 lbs smaller) weld them in. We TIG C/M and MIG M/S - if they want a M/S TIGed, I tell them why I don't like to, and let them deal directly with my welder, or theirs after I do the basic fit and tack weld.
Posted By: Fabman
Re: moly or mildsteel cage? - 12/20/08 09:08 PM
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Looking at that cage, a gusset to the windscreen bar and Door bar could have minimised that. It certainly does look worrying though. I can also see why certain builders use a straight bar from the door bar footing to where the windscreen bar joins the door bar.
AL....
Alan
Anyway you can post a pic of the gusset you are speaking about for this fix?
Posted By: B G Racing
Re: moly or mildsteel cage? - 12/21/08 12:16 AM
Posted By: B G Racing
Re: moly or mildsteel cage? - 12/21/08 12:31 AM
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I don't push customers one way or the other either....but...as I stated, I TIG everything, MS or Moly.
Monte
Im curious as to why M/S cages are TIG'ed. The test of a weld is that when you try to pull it apart, the material around it fails before the weld. Since a MIG weld has a larger radius than a TIG you end up with a larger surface area and (theoretically) a stronger weld. Is it for looks? A good TIG weld is usually nicer looking, but it is usually easier to get a MIG gun into the cramped areas, and you don't have to deal with trying to operate the pedal with your knee,
Nice resume, but IMO you didn't answer his question.
Thanks for the compliment on the resume.For that tight cage work set you TIG up with a small torch head and a thumb control.We hardly ever have to remove headliners on cars with full interior.Foot pedals are ok for bench work.
Posted By: Evil Spirit
Re: moly or mildsteel cage? - 12/21/08 06:48 AM
Just kidding about the facts and logic, Bob. And like I said, I don't fit into the car to do the welding so I leave it up to the welder to do his thing; I think he finally bought the small torch that you mentioned. A few years ago I did a Mustang for a friend, and I hole-sawed holes under the floor plates. We fit the floor plates, loop, back bars, halo, and front down bars, then slid the floor plates out to drop the cage to weld. After the cage was welded we slid the floor plates back in, welded the tubes and floor, and braced the bottom of the floor to the rocker boxes. Came out really sweet. It wasn't as much work as it might sound, and it really got the halo tucked up into the roof.
Posted By: B G Racing
Re: moly or mildsteel cage? *DELETED* - 12/21/08 01:42 PM
Post deleted by B G Racing
Posted By: FastmOp
Re: moly or mildsteel cage? - 12/21/08 06:59 PM
I have built both type cars so here's my
It all boils down to what the car is going to be used for
If it's a slower type car not looking for 8's or better and never will, then mild steal will pass tech.
But the books I have from SFI (you can order them direct for 30 bux) says that after so fast you MUST use chrome moly
As for the tig welding mild steal, thats so the builder can charge more as stated above.
