Chromoly vs DOM

patooyee · Aug 18, 2016

There are a few chromo Campbell chassis owners here on HL. SAP is one of them. They are not heat-treated post-welding.

My understanding is that, without getting re-heat-treated, the area immediately surrounding the weld (the HAZ) the chromo strength is reduced to roughly that of DOM. But since that is not normally the area that most of us see damage, it is normally not an issue. The area of tube beyond that point is still stronger / lbs than DOM and therefore weight savings can still be realistically realized without sacrificing strength. given material of similar OD.

tiny · Aug 18, 2016

I think the reason that the haz area on cromo is more critical than DOM is because the Rest of the cromo can take more load and is more rigid. So when it gets transferred to the haz, it has more of a spike than if it was DOM. DOM would have more of a cushion. Wether it held the load or bent.
Tensile strength numbers between normalized cromo and DOM don't show the real world difference. Try bending some cromo the same way you bend dom. It has twice as much spring back and the bender makes sounds like it's trying to bend 1/4" wall. Notching is a little harder as well.

blacksheep10 · Aug 19, 2016

tiny said:
I think the reason that the haz area on cromo is more critical than DOM is because the Rest of the cromo can take more load and is more rigid. So when it gets transferred to the haz, it has more of a spike than if it was DOM. DOM would have more of a cushion. Wether it held the load or bent.
Tensile strength numbers between normalized cromo and DOM don't show the real world difference. Try bending some cromo the same way you bend dom. It has twice as much spring back and the bender makes sounds like it's trying to bend 1/4" wall. Notching is a little harder as well.

Notching and cutting with bandsaw/carbide tip multicutter. I built some 4130 a arms last night and my multi cutter blade is getting dull. I was buzzing though erw, put the 4130 up and pretty much no go.

gottagofast · Aug 19, 2016

My thought is this:
If your use for the finished product is such that the weight of a cooler with ice and a case of cans in it wouldn't be a big deal then don't waste your money on 'high end' tubing.....

noracin · Aug 19, 2016

blacksheep10 said:
Notching and cutting with bandsaw/carbide tip multicutter. I built some 4130 a arms last night and my multi cutter blade is getting dull. I was buzzing though erw, put the 4130 up and pretty much no go.

you actually still build things???? :rolf:

tiny · Aug 19, 2016

I was using a hole saw notcher, and with regular hole saws with a little wear on them it took a lot more time and got to hot even with cutting fluid. But I found some heat treated hole saws, proly twice the money, but cut twice as fast and lasted 10 times longer. I believe they were Lenox brand. I think the tool has to be sharp to cut the chromoly, no matter what it is. Even if it just a little worn it, it dulls very quickly from there. All of this is coming from notching ten tubes and bending three. So take my input for what it's worth.

Elliott · Aug 19, 2016

They use to say that a drag car chassis built out of Dom and the same chassis built out of the thinner chromoly tube would have a weight difference of around 150 lbs. I bet there would be at least 200 lbs difference on a buggy frame with all the extra bars. I just don't see the sense in that for all the extra money and time Tig welding it.

patooyee · Aug 19, 2016

Elliott said:
They use to say that a drag car chassis built out of Dom and the same chassis built out of the thinner chromoly tube would have a weight difference of around 150 lbs. I bet there would be at least 200 lbs difference on a buggy frame with all the extra bars. I just don't see the sense in that for all the extra money and time Tig welding it.

It doesn't have to be TIG welded if you're not going to heat treat it. You can use regular old MIG.

1.75 x .120 DOM * 200' = 417.4 lbs
1.75 x .095 Chromo * 200' = 335.5 lbs.

Weight savings = 81.9 lbs.

RustyC · Aug 19, 2016

Dom 200 ft @ $2.28 = $456
Chro 200 ft @ $6.95 = $1,390 That's a difference of $934.

$934 Would go a long way towards aluminum wheels or lighter brakes.
Possibly saving more than 81 lbs.

blacksheep10 · Aug 20, 2016

RustyC said:
Dom 200 ft @ $2.28 = $456
Chro 200 ft @ $6.95 = $1,390 That's a difference of $934.

$934 Would go a long way towards aluminum wheels or lighter brakes.
Possibly saving more than 81 lbs.

rotating is more important once you start dieting anyway

collinmaune · Aug 20, 2016

I think putting aluminum hubs on athe buggy would be a better way to spend money and reduce weight. But it's all out of my price league. I would like to see a weight difference between a unit bearing setup vs standard hub setup and look at the price difference as well