| Author |
Message |
Pat Bartlett (Muddog16)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, May 21, 2005 - 6:34 am: | |
I'm working on the rear of my bus removing the engine and getting ready to water blast, prime, and paint the engine compartment! I noticed the first crack around the upper left corner of the engine compartment, then the second on the passenger side beside the engine, then the third one! I noticed that Prevost used some stainless tubing in all three of these areas, the cracking is approximately 3/8's of a inch away from the weld in all three welds. They all appear to be stress cracking from improper welding procedures, all of these areas are not major structural steel (1 1/2 box tubing). I thinking about removing these stainless sections and replacing them with carbon steel tubing! I'm not set up here at home to weld stainless and I don't want to go thru the expense for three welds. Does anyone have any suggestions? Thanks!.....Pat |
TWODOGS (Twodogs)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, May 21, 2005 - 7:15 am: | |
have a professional welder come out with a mig or a tig...sounds like 100.00 would do it...I would keep the stainless steel...look in the yellow pages...call him after you clean it up. |
Ross Carlisle (Rrc62)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, May 21, 2005 - 9:37 am: | |
If you can weld carbon steel you can weld stainless. If you have a MIG just buy some stainless wire. The same gas (75/25) will work fine with stainless. If you have a stick welder go buy some stainless rod.
Ross
PS...I'm assuming you can weld steel because you mentioned replacing the stainless with box tubing. |
Sojourner (Jjimage)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, May 21, 2005 - 10:11 am: | |
All stress cracks are flex points or it would not crack. Whenever a crack is welded with bead thicker than crack’s metal will later cause more chain reaction cracks around it.
Solution is to be sure all cracks are welded equal thickness or flush of its metal.
You might need to add small (equal thickness of tubing) (2” to 4”) over-lap gusset plate in triangle or square shape weld to linear direction of tube (not cross weld). Or “box” welds a thin plate over “trusses” or “bridge” framing.
However after all is done and later crack around it…than you have a problem of lack of or improper diagonal bracing to its frame. If your bus such as common MCI (monocoup) construction, than cracking cause from turning or leaning movement due to loose rivet or no rivet such as lower rear half end (engine compartment) in relationship between skin to frame. Very common MCI cracking problem at all four corners rear inspection framing. Engineering design problem.
All new buses are building with truss design such as MCI EL and Prevost H as well old Eagle.
Bottom-line is while welder there, have material ready to install fitted gussets and or diagonal braces to loose riveted skin or inspection cover area frame.
And look for professional welder who can weld thin gauge metal such as aircraft frame. Most are heavy metal welder which is very common. A good welder will only leave a bead no thicker then it metal.
All around filler rod for 304SS & mild steel are 308 SS. Mig (solid wire w/gas) is better & faster. Whatever your SS # is go next higher filler # to blend.
If you can weld as per above, than go for it.
Wish you well on your great project.
FWIW
Sojourn for Christ, Jerry |
Pat Bartlett (Muddog16)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, May 21, 2005 - 11:07 am: | |
Yeah i can weld, looks to me like where the cracks are....is where carbon steel and stainless are joined, whole different problem to deal with, purging is required when welding stainless, but i'm not sure what the procedure is for welding stainless to carbon steel, if any! I have a Millermatic 175 mig by the way! |
Sojourner (Jjimage)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, May 21, 2005 - 12:04 pm: | |
Mild steel is more flexible then SS and usually weld is stronger then material due to over weld (bead size) and un-anneal after weld.
By the way, mild steel weld to SS is more prone to cracking than otherwise.
Without seeing what your crack is cause from, it must harder to pin-point your problem. If you have digital photos and post it or send to me, I will be glad to share my view as to why & to avoid future problems.
My e-mail is removing X‘s from address.
Miller 175 mig would be my favorite for all round bus welder.
FWIW
Sojourn for Christ, Jerry |
Sojourner (Jjimage)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, May 21, 2005 - 12:54 pm: | |
Forgot to mention about sheild/gas;
Popular shield/gas for 304 SS is argon/co2 mixture. Ask your favorite welder supplier what shield/gas they have for austenitic SS metal on hand. Praxair have many, many difference gas available for SS alone.
FWIW
Sojourn for Christ, Jerry |
Ross Carlisle (Rrc62)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, May 21, 2005 - 1:26 pm: | |
Purging? You mean back side purging with gas? I've only done that welding titanium. I MIG and TIG stainless everyday. The only difference is the wire. I'd V the crack and repair what you have, then weld a gusset plate over the crack that extends a few inches either side of the crack. Hard to say without seeing what you're seeing. Either way, you have the equipment to make the repair. For steel you should be running Argon(75)/CO2(25) mix. That same gas will do fine on stainless.
Ross |
gusc
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, May 21, 2005 - 2:26 pm: | |
Without being able to see the actual setup I agree with all the recommendations for gussets.
The only problem with adding gussets is that the stress that caused the cracks will be transfered so problems may show up in another location, but I would still try it anyway.
Welding two different metals is always a problem. |
Ross Carlisle (Rrc62)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, May 21, 2005 - 3:02 pm: | |
Thats why you taper the gussets to spread the heat effected (welded) area over a larger area. Welding steel to stainless isn't really a big deal. If it was, they wouldn't have done it when they built the bus. The reason they tend to crack there is probably not becasue of the steel to stainless weld but more an engineering issue. That's an area that could have used a little more structural support.
Ross |
Ray D
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, May 21, 2005 - 4:02 pm: | |
If it is Prevost XL, I have a drawing of where the most common stress cracks will appear.
Ray D |
Jim Ashworth (Jimnh)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, May 21, 2005 - 4:32 pm: | |
Ray, does your info include the tag axle itself? Prevost has a service bulletin on reinforcing them on pre 1991(?) models.
I haven't seen any stress cracks on my '89 so I might be interested in what you found.
Welcome back, Ross. Jim C. & I thought you might have sold the bus.
Jim |
Ray D
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, May 21, 2005 - 5:38 pm: | |
Yes, it covers the tag axle, all suspension and framing. If you want a copy I have it in a PDF format I can email. Email me at spam_rdrum1@sbcglobal.net (remove spam_) and I will forward it.
Ray D |
Sojourner (Jjimage)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, May 21, 2005 - 9:57 pm: | |
Ray D….thanks for offering a copy
Ross Carlisle…..Naturally agree with you…thanks.
Gusc….gusset are to spread load near & around first weld joints………not to diagonal load points.
Another word to toughening the connecting weld joints but not to stiffen
And yes it will crack elsewhere, only because it not properly equip with diagonal brace in place or broken or loose (monocoup body) rivets.
So correct it where it due and you will have no problem.
SS weld to joint both mild steel is common for rust resistant.
FWIW
Sojourn for Christ, Jerry |
Ross Carlisle (Rrc62)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, May 21, 2005 - 10:08 pm: | |
Hey Jim...Long time no see. Did Jim C finish the 102? Might have to take a ride and check it out. I took a bit of a break from the bus, but back on it now. I sold some other toys so it's easier to focus on the bus now. I'm doing a kingpin this weekend...between rainstorms. After I finish the kingpin and chase down a small air leak on the rear, it'll be registered and inspected.
Ross |
LeonBrown
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, May 21, 2005 - 10:46 pm: | |
If you are welding stainless to mild steel I would just use a 7018 low hydrogen rod.Or else the stainless cracks on the carbon steel.Use a 3/32
lbrown |