Repairing WORN OUT Planetary Carrier for Cat 740 Truck | Making Custom Boring Bar

How are you guys, Kurtis from Cutting Edge Engineering? Today's work we have a

planetary

carrier

from a final drive from a 740 articulated dump

truck

, so it houses the final drive

planetary

gears in the differential which is used to transfer power from the engine to shift through the transmission in all three differentials there are actually six of these on the 740 dump

truck

which is two for each differential as you can see on the housing there are three pockets each of those pockets contains a planetary gear and then there is a pin that goes down through of the housing to hold the gears in place, the center hole has the main shaft running through it and runs from the center of the differential to the final drive.

There is also a cover plate that bolts to this to keep everything inside and then it is bolted back to the final drive assembly, these triangular holes, they don't actually do anything, they are just part of the structural trim and it adds a little bit of strength and it also reduces the weight a bit and the reason why is For repair, three of the thrust faces of the planetary gears were damaged so I don't know the exact cause of this failure, it is more than likely just general wear may have contributed to something like this happening due to oil or things not being assembled correctly if they were ever rebuilt so what we are going to do is machine the pressure planes once they are machined our

custom

er can add an additional shim to the pile of shims and you can put them back to work because just replacing this planetary

carrier

costs $7,800 so another repair method would be metal arc spraying or flame spraying the

worn

area but this has been known to cause cracking and warping because when things get hot and cold, they do. out of shape and could lead to a failed repair, so the

custom

er and I decided we were just going to machine it so we could put a new shim in there, which meant less downtime and they could get it running again, but the problem was machining that one. pressure.

The levels is their location, so not only are they at the bottom of a casing, but we only have a very small hole to work with, so I'm going to have to make a special drill rod to look at our heads. go. To make our

boring

bar, I'm going to use a piece of 38mm 4140 chrome bar. Now that I have that setup, I'm going to finish machining the outside diameter down to half a thousandth of its final size. With that I'm going to Machine this end all the way into the drill and insert the pointed head, so now with that roughing I'm going to switch to my finishing insert which is a TNGG, I'm also going to increase the RPM and decrease the feed rate, which gives us a good surface finish on the end that goes towards the

boring

bar, we are aiming for a diameter of 18 mm, so I have that point.

I'm going to move half a mile away from the rest of the bar and that will bring it. up to 30 mm and I machine it to that diameter so that it fits inside these holes. that hole is 47mm in diameter and we need to machine about 15mm from the thrust faces to give us some clearance and maximum rigidity in the boring bar. Now I'm done with that, I'm just going to chamfer the The edges and the length were split, so it was pretty quick and easy, let's see if it fits, so it fits really well. Now we just have to do a little polishing and drilling.

Come on, see you around, so the first thing I'm going to do is drill the hole for where the tool will fit. I just go to the angle and location of where that tool will be. The eyeball isn't very critical as long as I have clearance under the bar when I'm cutting, so I'm pretty happy with that angle, now I'm just going to center, so I'm going to use a 10mm carbide end mill to create a flat surface, so I have a place to start my drill, so it's already drilled. I'm just going to check to make sure our tools fit, so now I'm going to change the settings.

I need the flat part on the top of the boring bar so that the tapping screw that is in the boring head sits while it is in that position. I can then drill the hole and thread the threaded screw that will lock the tool in place, guys this is the drill rod done. I'm just going to install the tool and test fit it into the case to make sure we have enough clearance. So this is going to work great now we need to install the housing on the mill, so now I'm going to set up the boring and facing head.

It is a brand of gin. It's exactly the same as many other boring, confrontational heads. the market, except this one was now a little cheaper with my drill rod installed. I'm going to back up so I can get my starting position on the edge of the hole so we're ready to start searching. We took it very easy on the first pass just to make sure the setup worked and the boring bar didn't have any vibration, which is why our first pass didn't clear. I'm going to take another 2 out of a thousand point and hope we can get everything nice and clean so the area is clean enough to be able to take a measurement.

Unfortunately we couldn't get to the outside of the hole, but it doesn't go. It may be a problem because the shim doesn't go directly to the edge of that face, but I'll eventually get the tool out to cut it flush once all the precision machining is done, so now let's take our measurement. Take it and to measure it I'm going to use my internal micrometer so that it measures 90.96. We still have a little bit to take out to make room for our additional shim, so the measurement we're looking for is 91.25, which is the height of the gear. plus the four shims plus an additional steel shim plus a 3 mil point for an oil gap so to get it down to size we still have 0.25 mil to take out so we have that custom gauge.

I'm just going to extend the tool. Then I can remove that outer ridge, so now with that face done, I'm just going to go to the part that will give me the best access and visibility and then we can set everything up and do it all again. Homely Homely, what is your pig? you look for sucker he he look at it go get it go get it look what you got so the way this boring head and face the head works to make it work there's a collar and that collar grabs a gear inside they give you a little handle that goes into the collar that stops it from rotating and starts the feed, so there are three feed speeds, it starts at 0.04 mil per rotation and goes up to 0.12 mil per rotation.

There is also a dial on the front of the drill head that you can use to insert or remove the tool, so that's it, this repair is complete. This one didn't take long for those wondering if my client will charge for that boring bar I had to make. Yes, I will charge. it, but not the full amount, will be prorated on the next jobs we do that way, so this one will be done, we'll tie it to a pallet and return it to our client. because look what I say and right, and I'm and I'm Heh and I work it up to that diameter wait, we said what diameter is still yeah, that's why you say And right then it's very uhmmm so now I'm going to the configuration change I'm going to turn the ughhhmmMMM so it snaps into place pretty well, so I'm going to look, oh my God, so I'm going to turn the corner, so there are three speeds around, oh wait, what happened? you say I'm just going to take out the tool and just cut it off the ridge uhmm what do I need here now? abrupt I'm going to change the insert which is a TN what am I?

Oh my god, my hands are too big, wait, I can't get under them, oh my god, that's on the spot, how do you do it, you looked at him. From that angle, yeah, okay, I see how you did it pretty well, I got uhmmm, hey, it's going to be loud, ahhhhh, how does that one sound? I thought I had killed him. He is alive, he will lie in your bed.