i have a build coming up that I want to use chromoly for I am wondering what the strength is, compared to erw mild steel tube. example, if I used 1" 14 gauge mild steel for prototype 1, how thin could i go if i used chromoly 1" tubing? 18, or 20 gauge? even thinner?
chromoly tubing question
- Thread starter tomk
- Start date
Chromoly is stronger than dom and erw tubing so you will be able to use a thinner wall and keep the same strength. When I was making suspension parts, I would generally go 25-50% thinner wall thickness than standard cold rolled mild steel. I always used 4130 chromoly. You can go to a larger diameter tubing with a thinner wall and keep the same strength. One problem i always had with thinner wall tubing is the welded area was weakend. That being said I would always gusset between tubes to help support. Just my .02 hope it helps.
what are you building on?? was the prototype over/under built??
C
Cpt.Ron
Well-known member
tubing thickness
I have worked with 4130 tubing, ..the specs will refer to OD and wall thickness. From previous experience with similar appilcations, perhaps consider 7/8" dia. x 0.057" wall thickness. If you check with your tubing supplier, consider what is available, consider diametres with wall thickness's that will allow slip in fit, ie; 0.750" tubing will slide perfectly within 0.875" x 0.057" wall thickness. This relatioship exists on sevral tubing sizes in this range. I would suggest you consider sizes from 5/8 through 1" depending on design.
I expect that you may be on a learning curve journey, ...enjoy!! Have fun with your build.
Cheers
I have worked with 4130 tubing, ..the specs will refer to OD and wall thickness. From previous experience with similar appilcations, perhaps consider 7/8" dia. x 0.057" wall thickness. If you check with your tubing supplier, consider what is available, consider diametres with wall thickness's that will allow slip in fit, ie; 0.750" tubing will slide perfectly within 0.875" x 0.057" wall thickness. This relatioship exists on sevral tubing sizes in this range. I would suggest you consider sizes from 5/8 through 1" depending on design.
I expect that you may be on a learning curve journey, ...enjoy!! Have fun with your build.
Cheers
G
glhperformance
Member
you can purchase what ever 4130 tubing from wicks aircraft supply at a reasonable price and most sizes you could ever want and purchase the right tig rod for the job and in hi stress areas gusset the corners.
I build alot of suspension parts using 1" .035 wall and .75" .035 walls and make cross shafts out of chrome molly and use poo plastic bushings and you can really save alot of weight.
I build alot of suspension parts using 1" .035 wall and .75" .035 walls and make cross shafts out of chrome molly and use poo plastic bushings and you can really save alot of weight.
Our drag quad frames are normally 1" .057 and 3/4" .057
Check out www.aircraftspruce.com and search '4130 tubing', then go to the catalog page for all the sizes available. Note that a tube made of .058" wall thickness will have a perfect slide fit for the next size smaller OD tubing. AC Spruce also sells the welding rod for welding 4130. It welds very nicely with TIG as long as the parts are carefully fitted. When welding 4130, if you do not have heat treatment equipment to normalize the weld afterwards, get the room temperature up to 80F and turn off any fans that may cause air movement. The idea is that the weld area does not cool too quickly and cause the welded area to get brittle. The weld will be harder than the tubing, but if care is taken to slow down the cooling, it should not be a problem.
chrome Molly
when bulding chrome moly suspension parts for the cats I found that while not often as pretty as tig, mig welding had plenty of joint intergrity. When front a arms came back from the guys that couldn't leave the stumps alone, I found flattened tubes, ripped and torn tubing, never had a mig welded joint failure.
So I will tig it for you if you pay, making a show piece go tig, going to ride the crap out of it or building a race sled, mig.
when I have an a arm in the jig and finish welded, if you try and take it out of the jig, its got tension on the corners and you'll almost never get it back in the jig. So........... I let them cool in the jig, then evenly heat the the whole arm with a propane weed burner, let it cool, they lift right out, nice and straight.
when bulding chrome moly suspension parts for the cats I found that while not often as pretty as tig, mig welding had plenty of joint intergrity. When front a arms came back from the guys that couldn't leave the stumps alone, I found flattened tubes, ripped and torn tubing, never had a mig welded joint failure.
So I will tig it for you if you pay, making a show piece go tig, going to ride the crap out of it or building a race sled, mig.
when I have an a arm in the jig and finish welded, if you try and take it out of the jig, its got tension on the corners and you'll almost never get it back in the jig. So........... I let them cool in the jig, then evenly heat the the whole arm with a propane weed burner, let it cool, they lift right out, nice and straight.
L
LRD
Well-known member
I think that tip right there is worth its weight in er Chrome Moly!
First suspension I ever built out of chrome moly was the front arm on the skid
of my mtn Phazer. Looked pretty good. I have Miller 250 amp TIG and went with pretty thin tube. Things were good for about one or two seasons and then I found cracks parallel to the welds but not quite in them if I remember correct. I figured I got to much heat into the tubing and or needed a heat treating after welding. Always have wanted to get a mig and try that as I think you can run welds a lot faster with mig than with tig,at least with skill level with tig I have (self taught).
My latest piece is this rear suspension arm where I used fairly thick chrome moly tubing, and no problems in four years. Complete skid set up now with a pair of wheels between the front rails at the bend and longer extension plates for a 141"weighs 34 lbs. Credit to Dan at Alternative Impact for the Ti front arm, his stuff is WOW!
Good Luck
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