Used chassis market - so confused

[rosco]

So I thought that all of the manufacturers were going to Docol R8. However after calling quite a few the only one who told me they were making Docol cars was Rocket XR1

Longhorn said there cars are chromoly. I know I’ve seen longhorns for sale that claimed to be Docol but maybe they are mistaken or outdated.

One manufacturer told me they started making Docol cars but they are not anymore. They even went on to say that sometimes when the Docol is hit at a weird angle it splits open like a pop can.

So to Docol or not to Docol? Rocket who has been almost dominate seems to be sticking with it while I’m told other manufacturers are changing back to moly/dom.

Any industry insider info is appreciated lol

Thanks!!!

[billetbirdcage]

First thing is docol is only available from one place, AED as they bought the rights to North America so you have to buy it from them. So it isn't like moly or Dom where there are several domestic manufacturers and even imported brands available all over the USA from different vendors.

Next is Docol is a seamed tubing not Drawn over Mandrel (DOM - moly is DOM also but just moly material vs Mild steel). So Docol looks very similar to cheap HREW tubing (muffler tubing) from a quick look.

Docol is made in sweden, IIRC

[billetbirdcage]

DOCOL MOLY 1020 DOM HREW 1010
TENSILE (min.) 116,000 psi 95,000 psi 80,000 psi 45,000 psi
YIELD (min.) 100,000 psi 75,000 psi 70,000 psi 32,000 psi
ELONGATION (min. % in 2”) 13% 12% 15% 15%
DIAMETER TOL. +/- 0.006” +/- 0.005” (up to 1.500” OD) ---
WALL THK. TOL. +/- .005” +/- 10% (for ID’s over 0.500”) ---

[billetbirdcage]

As far as manufacturers going back to moly over the Docol:

Longhorn build a hand full of Docol cars and it's said guys did not like them so they switched back to the moly. No idea if that is the real reason or not but that is the story you will get told. As far as the other chassis reasons, I have no idea.

[MasterSbilt_Racer]

A properly designed chassis can be fine with any of the available tubing, with maybe the exception of HREW. Even that can be fine, but the car is going to be heavier.

Don't get caught up in the tubing. It's not that important. The chassis has three jobs. Keep the pickup points in the right place, locate the major components, and keep the driver alive in an accident.

Most racers are really only concerned with the first one. That is simply a function of stiffness. All steels have pretty much the same stiffness, up to their yield points. Those yield points can vary widely, as Billet showed above. However, if your given car is seeing stresses anywhere near yield, it will break in no time.

[Drake Racing]

Just to be clear, DOM tubing also has a seam, the only difference between it and HREW is the finishing process,
when the tube is drawn over mandrel, the seam almost disappears into the metal...basically just a higher quality
tube...moly is the same, just made of different material...much stronger for a given thickness, but much less elasticity.
(will not return to shape after light contact, and will break after too much flexing)...DOCOL is supposed to have the strength of moly with the elasticity of mild steel, but chassis manufacturers are still learning the pros and cons of using it.

Curt Drake
#55sr

[Jking24]

Everything said here is accurate but i don't think any of this information is relevant to purchasing a new or used car. The bottom line is information/ support is the biggest thing in today's racing. Imo you should base your car purchasing decision off of that and your budget not tube material their made off. Who ever your gonna get help from buy what they know and run. If you don't know anyone. Try and buy a car that was successful from a person that is willing to give you a little help. That is far more important than anything else

[fastford]

Just to be clear, DOM tubing also has a seam, the only difference between it and HREW is the finishing process,
when the tube is drawn over mandrel, the seam almost disappears into the metal...basically just a higher quality
tube...moly is the same, just made of different material...much stronger for a given thickness, but much less elasticity.
(will not return to shape after light contact, and will break after too much flexing)...DOCOL is supposed to have the strength of moly with the elasticity of mild steel, but chassis manufacturers are still learning the pros and cons of using it.

Curt Drake
#55sr

i have to disagree with your elasticity statement , moly has a greater memory than mild steel , i saw a demonstration several years ago where they took a piece of each and pulled it to equal loads and the moly went back and the mild steel did not ,

[Drake Racing]

You are correct, what I should have said is repeatedly, mild steel will bend and return (or you can bend it back) several
times and not break, whereas moly will only do it a couple times, and then becomes brittle and will break.

Curt Drake
#55sr

[Lizardracing]

For consideration, I make my own repairs and stuff so I prefer the DOM because it's easier and faster for me with less tendencies for embrittlement if care isn't taken. I've seen them all win though so I don't feel like it makes a lot of difference to new guy learning the basics OR even me, just a weekend warrior type enjoying my full sized toys when ever possible. Maybe Bloomer or Davenport or the like might notice DOM, Moly Etc, but I suspect they are doing their own things anyway.

[billetbirdcage]

The biggest thing in my book on tubing is consistency, now with that being said let me say a few things first

1. Different brands of tubing all react slightly different as well as the tolerances they keep

2. While there may be recommended tolerances or material make up/content for a tubing to be certified, that doesn't mean each manufacturer keeps those in the same range. Some may be on the high side of tolerances and another may be in a very small variance range.

3. Have you ever tested tubing from difference manufactures? I have in a limited manner, but just in rockwell testing the hardness of the tubing I can say that moly varies way less in the limited test I did by a pretty fair amount. Now to be fair, I borrowed scraps from several places and people I knew that used a lot of tubing so I got several brands and pieces over different lots or time frame they where manufactured. Dom varied a bunch between brands and lots of the same brand, meaning say webco tubing made recently vs some a year ago.

4. Ever tried to get only one brand of tube and use it exclusively? it's much harder then a guy would think, as manufacturers run tubing in lots and may not have certain sizes at certain times. So you or a chassis manufacturer are normally getting tubing from billy bobs tubing and when he needs tubing he calls Webco, Wheatland, Plymouth, or etc and orders tubing and if he normally gets webco but they are out and aren't going to run 1.5 x .083 for another month billy bob orders another brand. Then this doesn't account for pricing and we all know that matters to the vendors when your buying 10, 000 ft of tubing for resell.

5. Go over to the metal rack at a medium sized chassis shop, I will bet money you will find at least 3 or 4 brands of tubing and very likely imported tubing. It's hard to build a consistent chassis when the material is different on every chassis.

6. Also how much of the car is what they say it is? so they say it's a DOM car, does that mean the main cage and frame rails are DOM but all the smaller bracing tubing is HREW? You might be surprised.

I know I got off an on tangent from OP's original question but these are some things that need to be considered or understood. Now many of these things are out of your control and you have to have faith in the builder that it's consistent and what you think it is.

All that being said, any of the tubing will work when done in the proper manner. Dom is just going to be a heavier chassis to get the same strength as a Moly or Docol car and have different characteristics. I will say from years of doing this that as a general statement a Moly or Docol car will get faster as it ran and willl stay faster/more consistent way longer then a DOM car which is generally as fast as it will be the first night and will fall off from there (IMO). Obviously this can vary if the moly car is not welded right and cracks repeatedly or a various of things for other reasons, just a generalization.

All have their advantages and disadvantages, I would not rule out a car I like just because of the tubing they used


Side note* As Drake said on the DOM, it's a finishing process and makes more accurate sizing. People get caught up in the DOM vs HREW deal and think about the visible seam, but the major difference is in the material. HREW is a different material then typical DOM used for chassis and that is where most of the strength difference is not the visible seam.

Disclaimer, I'm not a tubing engineer so take this info for what it cost you. . . nothing SHRUGS

[billetbirdcage]

I should edit one part of my above post: All have their advantages and disadvantages, I would not rule out a car I like just because of the tubing they used

This excludes one tubing: HREW if the car is entirely made of this, run if you value your life or want a car that last more then 10 races. For the car to have any safety or life it would need to be made out of .120 wall or heavier everywhere. Some HREW is ok but not major components like frame rails or main cage and etc.

Again only my opinion

[ZERO25]

What was the tubing being used in Cup many years ago that appeared to have been machined inside and out? I think it was said that it was machined to make the wall thickness more consistent.

[Krooser]

What was the tubing being used in Cup many years ago that appeared to have been machined inside and out? I think it was said that it was machined to make the wall thickness more consistent.

Back them DOM was the hot set-up.

[grt74]

dom is still winning today, they are all for the most part building a stiffer chassis, the big thing is now they know how to tune them
there is nothing wrong with a dom piece, and if you were worried just weld a few small bars in the right places
the hot wrench (welder) wins alot of races

[racer2e]

Zero 25, you are talking about ground tubing. I saw a mod built by Beakbuilt. It was beautiful.

[fastford]

we ran DOM for years , main reason we went to moly was weight percentages , with an all steel 351 ford , we had to add a ton of weight to get rear % we wanted and was always way over the min weight , with the moly , we could get the same % at min weight also one thing we did find was the quality of DOM varied , some would have a thinner wall on one side , this would be the only advantage to HREW tubing , consistent wall thickness , but either way , considering it all , docol included , moly is still the best IMO......

[Krooser]

Steel tubing production video...
https://www.youtube.com/watch?v=4UVTZ4MRgpI