Cracked cross-members

[bapos]

I have welded worse cracks on more important things on automobiles. Not sure what kind of wire your using on your mig but I would just weld it up. If your using shielding gas I would say its the prefered choice. I use flux core so I am going to change over for this very thing. I would really look over all your cracks and get ready to fill them up.

[chev49]

i am not wise but..
can you post a diagram of your chassis with the engine trans and rear axles locations as well as the crack locations? that would help for diagnosis for welding/reinforcing help. I don't know where the cracks are, but looks like a overstress issue related to the component loads. Proper repair might dictate removal of some things for plating, etc...

Most likely, just welding up the cracks won't solve the initial problem, which must be addressed.

[bus-bro]

Does the bus have/had a trailer hitch? As for was it beer Friday when they built it, when and where this bus was built ('69, Hayward, CA) everyday was a beer/drug Frieday.

[ol trunt]

All of those cracks are classic symptoms of stress fatigue--in particular the large crack adjacent to the frame gusset. This sort of failure is always related to under engineering or over loading or both. In my experience simply re- welding the cracks just passes the stress to the area immediately adjacent to the new weld and a new failure occurs there. I would suggest that fish plating in addition to welding the crack (using .030 or better wire with argon not flux wire) would provide a safer and longer lasting repair. The trick to this is determining what constitutes an adequate fish plate and determing where the new load points will be after the repair. It is possible to over repair which simply adds stress to the next weakest point causing another failure. I know the bus went some 40 years without a problem but don't expect to get another 40 years out of such a repair. You probably will continue to get good service after the repair but I would recommend a scheduled inspection of the entire frame on a closely scheduled basis (1000 miles?) just to keep us all safe--just my 2 cents worth.

While I was writing this another post occurred which shows the storage area. It looks like there is a stress crack developing in the lower left corner of the box. If so you will want to get that repaired as well.

[chev49]

i assume that the sides of the bus have not warped any yet. this is kinda common on the old coach busses that old. the common place for problems is in exactly the same area you are adressing.
to me, its under engineering, like o.t. suggested, and my guess is using the same material thickness as the shorter single axle skoolies, worked for the normal life time of the bus.
i would think part of this might be caused by not enough body support on the truck frame, or possibly the frame rails are not exactly level.. if you havent checked that stuff it would be a good idea, since the entire body rests on the frame.
if i had this problem with one, i would properly block the body and remove sections where they were cracked and where there is u shaped channel, i would get much longer pieces, sandblast the undersides of the end pieces and with a heavy wall tubing inside plug weld the piece back in with as much more length as i could on each side of the crack, or just change out the piece with one much heaver i made up myself. as suggested, this will change the loading of the cross member, and possibly you need to do this to more than one of them. the other thinner material could be cleaned and plated as well, but could over time have problems, but i doubt it would happen very soon.
i might also consider rebuilding the entire floor supports like 3 feet on each side of the crack area with heavier materials. the compartment i would just add the largest size piece i could, punch and plug weld the whole thing in.

and repairs should consider what kind of load you plan on carrying in the back..
just things i would check and do.

[ol trunt]

Hi, I've been thinking about this thing off and on all day. Do the rails with the cracks run parallel to the length of the bus or do they run perpendicular to it--knowing this will help us understand what the specific causes might be. Also, do a through inspection if the entire frame looking for rust and cracks particularly behind the tag axle and at the very end (rear corners). Are any of the side windows hard to open/close, if so specifically where are they located? As '49 suggested look down the sides of the bus for even small ripples in the skin and note where they are.

There were recalls for cracked spring hangers on this model so they should be checked (around bolt holes).

BTW, I didn't mean to suggest pure argon gas as a welding gas but a commercial blend of argon and carbon dioxide suitable for welding steel---your gas jobber will know the ratio.

While I'm blathering, I should mention that there several sites on the net that discuss frame repair and modification. Read as many as you can find before you commit to a particular repair method. I guess thats 4 cents worth so I'll shut up

[browncrown]

I'm not a welder, so I can't suggest how to do the repair, but in those models with trunks in the rear and no constant weight of an engine, it is very likely caused by tail strikes over the life of the vehicle and the stress each of those strikes put on the cross members...just my thoughts

[chev49]

answer... mostly cause it is faster.
actually when i want something to never come apart, i plug weld and seam weld it both.. makes it almost impossible to take the pieces apart again, but it is strong.
sheet metal is normally what may warp, and if welded correctly that effect will be minimalized. You are working with stamped material. it shouldn't pull too much, if tacked up.

[chev49]

the body has to be supported by the frame... maybe whilst working on it you need to add additional body mounts.. one would not think that the frame was flexing cause the school dist was going over huge pot holes at 60 mph...
if your place has sandy soil like the place n ocean shores that i bought 2 collector cars from, then you might need extra blocking... just saying...