I have some repairs to do on the underside of my 941 Loader & am not sure how to approach the one item. Where track frame bolts to the machine on the inside, on the RH side of the machine, the previous owner had made an attempt to repair where the bolts broke by just welding the brackets to the inside of the track frame. I am planning to repair it & not sure if I should go to the trouble of burning out the broken bolts (all are broken off deep inside well below the surface of the brackets) & re tapping the threads or just grind & properly weld what is there, seeing that it is an old machine? Any suggestions on how to approach this? Also there are about 5 belly pan bolts which are broken off that I plan to repair as well, now that I have the machine up in the air where I can work on it easier.
Yair . . . Metalman 55. Not familiar with your machine but imagine there are vertical bolts as well on that assembly. If they are intact and functional I would certainly consider a couple of good vertical up welds and a nice fillet along the bottom . . . big awkward job otherwise. However . That is an excellent job you have done on setting up the tractor and if you can hire or borrow a magnetic base drill those belly guard bolts will be (relatively) simple. You may have to tack weld a decent base to the underside of the frame . . . I used to resurrect one side and hinge the other, makes it simple for cleaning. If you can get access to a magnetic drill and there's clearance you may find drilling out the broken studs on the trackframe a viable option . . . if possible I usually go one size larger and tap a whole new thread. Just my thoughts from half a world away. All the best with it. Cheers.
It's amazing how much easier it is to work with a few more inches of shoulder room! I'd be looking around for some 3/16-1/4 steel sheets to slide under there to let you use a creeper
This is how we got it up there. BTW, I do have a mag drill.......hadn't thought of using that under there........may try that option first, as there is quite a bit of room under there now.
Yair . . . Metalman 55. If you use it horizontal or upside down don't forget the safety chain for if you have a powerout or the lead gets disconnected. (voice of been there done that speaks and face grins) Cheers.
Nice jack stands. If you mag drill those broken bolts please post some pics..
The mag drill would not fit in there, so had to blow back in the hollow with a torch to extract the old bolts which were broken off flush with the track frame, then spent a lot of time cleaning out the threads. It was a nasty job & it cost me two torch tips but got the job done. The center bolt will not tighten completely so I think I will add a weld along the bottom where the previous owner had made an attempt at welding.
grade 8 spacer washer under the middle bolt?
Actually I used a Gr 8 Lock Washer under the bolts. It is not bottoming out, just that the torch cleaning & re tapping the threads left them somewhat comprised on the center hole. I may drill & tap 3/4#10 on the center one. The originals are 5/8 #11.
Not sure what the original hardware was or what others would suggest but personally I'm not a big fan of split type lock washers in many places let alone a high stress location like that. Good heavy hardened steel flat washer would be my starting point.
Yair . . . I'm with you there kshansen . . . and after working for a shift or two and the bolt is holding tight I have even been known to weld one flat of the bolthead to the washer and a short fillet of weld between the washer and the assembly . . . particularly on a component that has been giving trouble. Well done to Metalman 55 for persevering with that. Cheers,
Nice work on the repair. I am another vote for some nice machine style washers under those bolt heads. Not the big flimsy flat washers. seams like a good thick washer helps in a high stress area like that.
I also would use a hardened flat washer instead of a lockwasher. Cat makes good hardware. Would also go up to a 3/4 in the hole that won't tighten. Better than relying on a weld
I did check on SIS for one of the 941 machines and the washers Cat uses are 5 mm thick hardened steel, that would be about 3/16+ thick. Also noticed that there are shims used at that location used to adjust the alignment of the track frames. The Cat part number for those is 4D3704. Also agree moving up to 3/4 on at least the one questionable hole would be a good step. If there is clearance problems with the larger head of the bolt then one could use a 12 point bolt or an allen headed bolt. I would lean towards the 12 point.
I was able to locate some "extra thick" flat washers this morning to put in place of the lock washers. BTW, why is the solid thick washer better in that application than a lock?
I have seen lock washers ride out(flex from under a bolt head) and loosen themselves up as they spring load/unload even when exorbitantly tight, thin cross section removes strength, as to machine washers they tend not to compress or flex, what thread stress is applied remains applied.
Actually ended up redrilling & taping 2 of the holes for 3/4" #10 & putting the larger bolts in them, along with the heavy flats.
just look at how much larger an area those washers spread the load over compared to the lock washers in the earlier picture! Did you by chance check the alignment of the track frames? The instructions I had seen called for a max of 1/8 inch tolerance. Parts book shows six shims for adjusting this measurement. I have not had direct involvement in one of these machines so not sure how critical it is maybe someone else could voice an opinion. If you could give me a S/N I could check with SIS to be sure how and what to measure.
Re the shims, the previous owner had welded the bracket in place after the bolts broke off, in essence freezing the positioning & everything seemed to work ok since I have owned it, so with that in mind the welds act as shims in a way. I cleaned up the old welds & added a few passes under the bracket once the new bolts were in place.