Practice English Speaking&Listening with: Repair a Cracked Caterpillar 789 Dump Truck Suspension Part | Machining & Welding

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how you going guys Kurtis from cutting edge engineering

tonight's job is a 789d front strut cap so this part is actually off a 789 d cat

dump truck this is the top cap of the front strut

of the machine the strut is bolted onto the shafts of the truck and it allows

allows for suspension movement and steering of the truck

this is just one of many components that go along with it it's coming from the

customer with a crack in it

we've also got a lot of excess wear on the top of the pin from the bearing

that is also caused from incorrect fitment this has been repaired once

before by someone else we do come across these quite a lot

where someone's repaired them they generally always fail in the same

place generally comes down from improper fitment to the machine after

they've been been repaired people don't understand there's a few

other steps that need to be taken when fitting these back back to the machine

when they are a completed strut so we're going to chuck this in the

lathe we're going to set it up we're going to see if there's any run out on

this pin that will then tell us whether the pin was

installed correctly and then welded in situ or it was

machined after it was welded if there's any sort of run out there it's it's

going to impact the life of this component

so once we get it set up in the machine we'll see how true it's running

if it's running pretty good we might be able to salvage the pin we do have a

piece of material in stock that we're going to use if we need to replace it

as it goes for repairing we're just going to get in the machine and see what

this thing's doing

righto so we've got this set up in the machine we're going to throw a dial

indicator on it now to see how much run out this pin actually has in it

if there's any run out in that pin that's going to give us a pretty good

indicator that that was the reason the weld actually failed

i need to be a little bit wary where we put the dial indicator as there is a bit

of wear on the pin from the spherical bearing that

that works up top here i'll get a dial indicator and i will set it up and see

what it's doing

so now that we've discovered there's run out on this pin first step is we're

going to we're going to put a center up it

we're then going to machine this weld out and try and get this pin out

we'll then see what they've done inside here as we didn't do do this repair

so after we machine this pin out we'll be able to see how they repaired it

previously and make a plan of attack on how we're

going to fix it properly

right oh so we've uh we've machined out the crack uh

found the base of the weld where the two pieces of material meet

uh there's not a great deal of weld in there

that would probably be some of the reason why the weld did actually fail

so next step now is get it out of the machine and

we'll try and remove this pin with a bit of heat failing that we'll just machine

it out

all right guys so we've removed the pin and found out exactly how they

installed the new one a little bit different to how everyone else does it

um it didn't work they'd actually threaded the pin

and threaded the housing and then screwed it in and then welded it in

uh we did find a lot of dirt and [ __ ] like that floating around in there

which you know that's not usually a good thing it means there was dirt getting in

from somewhere could have been going in through that

crack the repair was only about 20 mil down inside this hole

wouldn't have been enough strength or enough enough structure down inside the

housing to actually make it all work so what we usually do is we'll bore it

out we'll go about 60 mil deep open it up to

whatever diameter we need to and then we'll machine our new pin so it

goes all the way down inside and it's actually down inside this plate here a

little bit as well so that that extra little support seems

to help it really well so uh we're just going to finish this to

size now and then we'll take it out of the machine and throw the

piece of material in and start making the new pin

so now that we know the pin is going to be replaced we're going to cut the new

stock for the replacement pin so we've got our piece

of material set up in the Everising saw uh it's a 360 horizontal bandsaw piece

of material we've had in the container for a while so we dug that out this

morning we've got to cut it to length it's a piece of 150 mil 4140 we need to

cut it to 220 millimeters long

right so we've machined everything everything's finished now we've got the

plate machine to size we've got our new pin machine to size

well only the bottom half of that pin we're going to finish that off once it's

been welded just in case anything moves does

anything weird like that so first step we're going to do now is

we're going to preheat this plate and then we're going to try and fit this

pin it is an interference fit of about 0.15 of a mil

so that's about 6 thou in bananas if all else fails and it stops halfway down

we've got the press sitting here ready to go so we'll just throw it straight in

the press and push it home i've also drilled a eight mil hole all

the way through this pin as a vent to allow any um any pressure

that's built up inside to escape so we don't have any dramas with that so

yeah let's let's get this thing hot

that's already locked

all right so that went pretty well as perfect as it could be

got it preheated drop the pin in there and it instantly locked when it hit the

bottom so that is a very tight neat fit we're

going to let this cool off just a little bit

oh the heat's already coming up into that pin we're going to let this cool

down a little bit while that's happening i'm going to set

up all the welding gear and we're going to set up a little rotator and weld this

thing out

righto guys so we finished the welding on this it's been cooling down for about

seven hours now we've got it back in the machine uh

we're going to start by turning off this weld

uh we're going to machine a bit of this shoulder down put a radius in that

corner we're then going to machine the pin to

size it's going to be finished out at four inch

exactly uh we'll then put a 22.25 mil hole in the end of it we're going to

thread that with a one inch unc tap that's just for an eyebolt or

lifting whatever the customer needs to do

do with it after we do all that the job's finished

a little bit of stuff once once we get that pin out we can see

see what people are doing just a um rough [ __ ] which will tell us

it might tell us strut connects to oh

boy you where the bearing has been uh rubbing into the pin [ __ ]

i'll get a dial going and um

so i'll get a dial indicator we didn't do do this repair we're going to fix it

again uh properly and start to put the the

features back back onto this um this hat top hat

cap strut cap strut cap try and get it running true to find out


is that

hang up not tonight i bet they're watching they'll know it's


probably is that it oh

that sounds right why is there

hello well do you want to be by the saw in front of the saw

i don't want to be by it here's good is here alright

yep right here we go you going yep

[ __ ] getting uncomfortable stop leaning i've got to do stuff

just so we've got that set up in our new saw

new to us saw here's our new well old right guys so we've got the bit of

material set up in our new saw

[ __ ]

um so yeah let's let's get this thing


pretty good

oh let him have it he's getting annoyed drop it


drop it homeless

drop it

The Description of Repair a Cracked Caterpillar 789 Dump Truck Suspension Part | Machining & Welding