I have a late 70s 225. I am at a point where I really need the machine for maybe 10-20hrs of use but there are several cracks in the under carriage frame. None that support the tracks, but the I beam members that connect the track carriages to the house have a few cracks in the webs. Being in the structural design field, I fully understand the fatigue issues here but I might not have the time to devote to this right now and I don't want to do a half ass repair. Regarding repair, that also gets a bit dicey to do right so I am curious of those that have experienced this, how was your repaired? My thoughts in mind are to chamfer out the cracks to get full penetration welds but I don't want to go nuts if some decent prep and hot welding will take care of it. I am not sure if guys are going to stick weld only on this or if MIG is common? I am most concerned with all that mass sucking the heat out so fast and making very fragile welds.
If you need so little in the way of hours before the machine can be downed for repairs have you considered marking the current extent of the cracks and monitor them as you work..? Sometimes cracks develop very slowly and this might just give you the time you need to complete the work. even if you only just spotted the cracks they could have been there for a while already. Also some good photos of the cracks would help to give advice on the most effective repair procedures.
Cure is a new radiator cap Minimum fix is 100% 7018 full penetration,preheat.,.... Prolly no permanent solution but some pictures should lead to some reinforcement ideas. By the way when do you plan on paying me for the service manual and parts manual?
A common thing my friend the weldor does with cracks is use a bit of heat to clearly delineate the end and then drill at exactly that spot with a small (1/16"?) bit. The hole allows for some flex and stops the crack from expanding, usually. This is done before welding also for the same reason.
I know things re not looking good here! Pretty serious situation as the previous owner obviously did some half ass attempts and just made more work for me. I planned to drill stop what I can but some of these will be impossible to drill correctly and there is one area that has even got into the flange which is is much worse. I am thinking some patch work might be needed there. Any thoughts on MIG for this? We have a 400A Esab that gets serious but not sure it can touch the penetration of stick. I too was thinking I will simply have to preheat to cherry before attempting this or I will have no ductility in that weld at all.
It's been welded before by the looks of it. If there is nothing worse than what's in those photos then I would say if you want to run the machine for 10-12 hours before downing for repairs it shouldn't be a problem. Obviously mark the extent of each crack and see if they are extending as you work. Edit: I think this is what you might be looking for ........ a Service Magazine article from 1979 entitled "Reinforcement Plates And Gussets Can Be Added To Carbody Legs". The reinforcement appears to be pretty much right over the top of where your cracks are. So your repair procedure is going to be 2-fold; 1) repair the cracks and, 2) add the additional reinforcement. Drop me a PM with an email address if you want a copy of the article.
Looks to me like time to scarf out the whole angled section of plate and replace, maybe with a doubler over the vertical seam? Seems like the better way than trying to glue up that old fatigued metal.
Don, Are you reading my mind..? I've just sent a copy of the Service Mag to the OP and replacing the vertical skin of the carbody legs with new plate in the areas that were cracked was exactly what I recommended having seen the photos above.....
Nige, if I'm thinking the same thing you are I take it as a compliment, I know you are on the right page! :drinkup