Hard facing 17 ton excavator undercarriage rollers

[awemawson]

But that will destroy any bearings that are left in done intact. Dismantling will take a fair bit of time.

I suspect that by the time you've implemented any of these suggestions, if you put any value on your time, you'll be close to the price of a replacement roller.

Try http://www.ukconstructionparts.com/ , they've always been the best delivery time / price compromise for me.

 

[J.B. Welding]

Mild steel tube split and welded tightly onto roller, then hard faced on site with 400 or 600 grade rods. Done in stages a bit at a time to keep heat down and done rollers on machine, cooling occasionally if needed. 8 rollers per side so plenty of time in-between welding to cool. It's gonna be at least two grand to replace the rollers with new and the rest of the machine doesn't justify that-so it's a compromise situation we are looking at or scrap the lot.

 

[Rig Pig]

Think long and hard before you grind anything like that on a lathe, all of the spent abrasive & grinding dust will wreck the slides. I would send it out to go on a cylindrical grinder.

 

[J.B. Welding]

Done a bit of grinding on the lathe over the last 20 years and can honestly say it has suffered very little. A bit of grease and a cover over the bed, with a good oily wipe down after does the job. It's a 60 mile round trip x2 to a cylinder grinder shop and a weeks wait, so we do what we can here.
Now proposing to weld strips of mild c.20mm wide and hard face up after, then spin the roller by hand and give the welds a buff over with a flap disk to smooth it all out-all on the machine. Budgeting a day to a day and a half on the worst side (previous issues caused wear to one side more than the other) as a punt to keep the old girl trackin.

 

[Bill Edwards]

The trouble with adding any metal to this kind of jobs tends to be that the welds end up wearing away and the metal then peels off, or the metal wears through and then peels off - leaving a mess in the process.
If you can manage to use metal that's slightly narrower than the part you're building up so that you can get a weld down at the base of the lip, and the other weld should be out of harms way, it should last for quite a long time (i.e until the added metal is nearly worn through to the roller).

Doing it on the machine will save a vast amount of work in dismantling and reassembling them. And have you checked that they'll even unbolt from the track frame - 1995 is newer than any that I work on, but I tend to find that the bolts holding them on will shear, not turn.

 

[J.B. Welding]

Thanks Bill. The bolts I have removed from other parts of this machine have been tight but have always come out with the 6' bar. Yes, I plan to keep the welds holding the strip below the wearing face, and run a hard facing bead over the top during the facing pass. The strip idea is really to save heating the roller too much and save 7018s. It would be daft to have a hardened bit inbetween 2 critical and soft welds-pointless exercise. My only concern here-hence it's a punt-is that the soft filler is squeezed and spread out thus causing the hard face to chip off. The more I think of it I'm hoping the hardened case will trap the soft filler so it physically can't go anywhere. TBH I was always planning to do this on the machine-got jittery at the thought of oil filled sealed units and then realised these things must weigh 10kg+, they will take a bit of heating up. So long as I keep them below 100 deg.C you think they will survive?

 

[morph]

Before doing anything at it get a price off digbits for new rollers, I suspect they will be quite reasonable and will save a load of hassle. It's madness chucking good money after bad trying to bodge them!

 

[Bill Edwards]

7018 is pretty strong stuff and doesn't seem easy to break. I'm not sure how thick the strip is that you're planning to stick on, but assuming it's reasonable thick I wouldn't expect it to squish much and break the welds. And really, when you think about it all the welds are doing is holding the strip in place, rather than directly taking pressure.
I recently built up the sprockets on a tracked crawler. They were worn down to the point where they could just about spin, and due to the wear in the links and the sprocket diameter being so small the track was able to jump off with ease - which it did repeatedly.
I cut up a length of 16mm mild bar (cheap, not hardened as this was slightly experimental, and the machine doesn't do that many hours) into approx 2" pieces and welded them onto the sprocket. They're under some serious stress, particularly as the pitch is totally wrong as the links are so worn, and the tracks are as tight as can be, but a 6010 root and 2/3 runs with a 70xx rod on each side and they aren't going anywhere! Sorry, no pictures to describe it.

The rollers carrying the track shouldn't really be that hard to bodge, and the surface finish shouldn't be that important really. As to how hot you can safely get them, it's hard to say. Think of old rubber seals trying to keep in a few ml of old, thick oil in place - they were probably fine to 100 degrees when new, but by this age they'll be as hard as concrete and less flexible. I don't really know how they'll react to heat, the best I can suggest is to keep the heat input as low as possible and do short bursts, move onto the next and so on and hope it's cooled enough to gain a little more by the time you get back to it.
10kg (or quite possibly more) does take some time to heat up, but it takes some time to cool too - two sides to a coin here.

What sort of machine is it?

 

[J.B. Welding]

They are about £100 each plus fitting. Never bodged anything in my life..

 

[J.B. Welding]

Daewoo machine-I had a few quotes but will try digbits now you mention them the name rings a bell from past dealings. The customer in question is possibly the tightest man in Europe, if a temporary repair costs half new he will repair every time. I used to loth his way but after years of dealings I can see what he has saved and it all adds up to many, many thousands.
Safety wise there are some huge chunks of timber up there I can set the digger up on and some big boulders too. I don't fancy a 17 ton hat fitting at all.

 

[Bill Edwards]

I was meaning more as to the type - 360, dozer etc. 360's don't really need to do that much tracking, it's to move the machine from A to B. Dozers/loading shovels are not only moving the weight of the machine but pushing/pulling however many tons of material at the same time, and a vast amount more work with the tracks per hour.

 

[J.B. Welding]

Sorry, it's a 360. But it works a big forestry estate a A is many miles from B. Hence the wear. There were some other factor that caused excess wear that I have sorted out since I started maintaining the machine-like a sprocket put on backwards and a cracked chain link, but mostly the machine was knackered when he got it (£5000 for a 1995 17ton 360!) and it's all about keeping it going.
I think the chaps have covered all things to be aware of and thanks for the warnings/advice. I'll post how it goes after day 1.

 

[DAPPH]

Daewoo machine-I had a few quotes but will try digbits now you mention them the name rings a bell from past dealings. The customer in question is possibly the tightest man in Europe, if a temporary repair costs half new he will repair every time. I used to loth his way but after years of dealings I can see what he has saved and it all adds up to many, many thousands.
Safety wise there are some huge chunks of timber up there I can set the digger up on and some big boulders too. I don't fancy a 17 ton hat fitting at all.

Is he Scottish or a Yorkshire man or of both stock JB

Take care you don't end up getting blamed when it fails after a few weeks.

Most of the heavy gear I worked on was used on demolition sites and an 18 acre inert land fill that had a crusher and two graders plus all the other usual quarry type machinery ... those sort of work places fair eats machines and makes serious repairs on construction dinosaurs something to walk away from most of the time .... unless your skint .

Would you be so kind and take pictures of what your doing ..even if it is only for historical purposes .

 

[F.J.]

If the machine isn't worth £2000 then is it worth going to the lengths you intend to? Surely the work it does warrants spending money on it to keep it going?

If it's just to keep it going for a bit longer, I wouldn't be fussed about going to so many lengths. If he is tight then just be clear to him that what ever you do won't last and that there is not warranty implied on the work. I have a customer like him and he is an almost constant, repeat customer but the jobs don't pay that great, I also have a customer in the same game that want everything doing properly. I get much bigger, better jobs off him and I also enjoy those a lot more than the first guy.

 

[J.B. Welding]

Is he Scottish or a Yorkshire man or of both stock JB

Take care you don't end up getting blamed when it fails after a few weeks.

Most of the heavy gear I worked on was used on demolition sites and an 18 acre inert land fill that had a crusher and two graders plus all the other usual quarry type machinery ... those sort of work places fair eats machines and makes serious repairs on construction dinosaurs something to walk away from most of the time .... unless your skint .

Would you be so kind and take pictures of what your doing ..even if it is only for historical purposes .

He knows its a punt but also knows I do my best for him. No guarantee is implied or given and to be honest £60-80 quid on rods and a couple of hundred for me for welding it's probably worth a go. I like to do these types of things for a challenge, if not just to make an interesting day of it. I'm not banging my head off chunks of plant day in day out so sitting on a beautiful hillside in Galloway burning rods is a break from the normal, fiddly jobs I mostly do. If it all grinds away in a week his attitude will be 'at least we tried' and he'll probably then cough up for new rollers. (digbits £26 ea. more per roller than best quote).
As mentioned before, the labour and potential pitfalls involved in pulling the old rollers off may escalate into a huge job if the bolts do shear off or whatever-so attempting a repair whilst on the machine has to be worth it I think.
If it lasts a year or so it will be a confidence boost to my welding prowess, if it all goes wrong I'll post here it's not worth doing...for the benefit of future generations.

 

[TechnicAl]

Just a few thoughts for you
1. When 2 parts are in moving contact the softest will wear away. I know thats obvious but sometimes its ignored and you end up spending the money on a part that wears another more expensive part.
2. If its been hardfaced before its very difficult to re-surface it, unless you remove all the previous weld.
3. The 25-30% Cr + 5% Carbon types are very hard even when diluted with the parent metal so a single pass of this type can be more effective and cheaper than using 3 or more passes of a cheaper product.

 

[Kent]

Just a few thoughts for you
1. When 2 parts are in moving contact the softest will wear away. I know thats obvious but sometimes its ignored and you end up spending the money on a part that wears another more expensive part.
2. If its been hardfaced before its very difficult to re-surface it, unless you remove all the previous weld.
3. The 25-30% Cr + 5% Carbon types are very hard even when diluted with the parent metal so a single pass of this type can be more effective and cheaper than using 3 or more passes of a cheaper product.

You know I dont think I have ever heard of point 3 previous if I have its been long forgotten- thanks for that Al

 

[Bill Edwards]

2. If its been hardfaced before its very difficult to re-surface it, unless you remove all the previous weld.
3. The 25-30% Cr + 5% Carbon types are very hard even when diluted with the parent metal so a single pass of this type can be more effective and cheaper than using 3 or more passes of a cheaper product.

Regarding point #2, I doubt if it's applicable on this particular job but it makes me wonder - if welding onto something which may have been covered with some kind of hardfacing before, would a 312 dissimilar rod allow you to weld over it as normal? I've seen dissimilar rods advertised as being suitable for a buttering layer before hardfacing, so I just wonder if you weld something on with them (either as a layer then welded with something else or just with the dissimilar rods) - basically 'buttering' in reverse?
And would something welded onto hardfacing (such as a cutting edge, tooth etc) be asking for a failure as the hardfacing wouldn't have the strength to fix onto? I assume it would fail, but just wonder...?

Point #3, about using 25-30% Cr + 5%, am I to take it that if I set out to buy some hardfacing rods (which I keep thinking I need to do) I should be buying some with these specs, as they're superior to the kind I'm likely to pick up when looking to buy a box of rods that say they are hard facing?

 

[TechnicAl]

Regarding point #2, I doubt if it's applicable on this particular job but it makes me wonder - if welding onto something which may have been covered with some kind of hardfacing before, would a 312 dissimilar rod allow you to weld over it as normal? I've seen dissimilar rods advertised as being suitable for a buttering layer before hardfacing, so I just wonder if you weld something on with them (either as a layer then welded with something else or just with the dissimilar rods) - basically 'buttering' in reverse?
And would something welded onto hardfacing (such as a cutting edge, tooth etc) be asking for a failure as the hardfacing wouldn't have the strength to fix onto? I assume it would fail, but just wonder...?

Point #3, about using 25-30% Cr + 5%, am I to take it that if I set out to buy some hardfacing rods (which I keep thinking I need to do) I should be buying some with these specs, as they're superior to the kind I'm likely to pick up when looking to buy a box of rods that say they are hard facing?

Well the answer is probably. You could also weld a layer of 7018 onto the old surface. Its a bit of a guess really as it depends on whats been used. The odds are that 312 or maybe 309L would be best

as for joining 312 would be a good choice.......if it doesnt work its probably unweldable......when you dont know the composition 312 is probably the best choice.

as regards the hardfacing........thats what I would buy. Bear in mind that heat treatment wont affect it but it will be about as hard (and tough) as it gets so its likely to wear away anything it contacts.

Wear Plate is mostly surfaced with this composition.........I used to make it at Triten.

 

[J.B. Welding]

Great info as ever Al-These rollers are forged and I guess case hardened after, they are on the under side of the machine and roll on the chain as the excavator moves forward. The chain, that is the spine of the tracks, is also a very hard material and probably a similar composition. Both are worn but obviously it's easier to build up the rollers than meters and meters of chain. The rods my supplier stocks are ESAB and they have these-OK 84.52 rods,
How to order


Specifications
Classifications
EN 14700
E Fe8
Typical Mechanical Properties
Current Type CA/CD/CC (+)(-) AC, DC+ OCV 70 V
Hardness (HRC) 49-55 HRC
Weld Metal Analysis
C 0.25 %
Si 0.5 %
View full specs

A general-purpose, hardfacing electrode depositing a corrosion-resistant fully martensitic steel. The electrode is suitable for hardfacing shafts, racks and pinions, links and pins, valve seats of cast steel, mixer arms, feed gear, knives, loading buckets and track rollers. Generally, a preheat and interpass temperature of about 200°C is recommended for most applications

The 200c preheat was a worry, but a bit of bearing research and I've found the bearings will not be damaged till I hit c.300c, so still in working parameters. I'm thinking a few 7018 runs will bring it up without needing to take the gas to it?
I'm imagining that the seals will be long gone TBH, it spent a good whack of its 20 years in a sand quarry and as we all know, that stuff gets everywhere!
Replacing rollers alone may not even solve the problem as the chain is worn-it would be right to replace the chain and rollers at the same time. Now that would be a fair old cheque to write.
Getting ready to hit this job with confidence now. It won't however be putting my kids through college