CAT D5K undercarriage

wee_gus · Oct 10, 2020

Good day my friends,

I have just replaced the undercarriage on a customers 2011 CAT D5K.
We have removed all systemone components and installed Salt components.
The existing sprocket segment bolts had no washers.
We were supplied washers for the new segments and have installed these behind the nuts facing outwards, now the customer suspects the nuts are protruding out past the segment and may get caught in the track chain.
I checked this but couldn’t see it it.

Machine is a YYY prefix

Nige · Oct 10, 2020

Not sure if I can shed any light but here goes. All info is for YYY prefix D5K machine
The one-piece sprocket calls out only bolts (2.1" long) & nuts - no washers. The parts manual illustration appears to show the nuts on the outside but no sign of the washers. See below. Are the washers supposed to be on the inside under the bolt heads I wonder.?

The 6-piece segmented sprocket calls out the same bolts (2.1" long) and the same nuts, but also a 3.5mm (1/8" approx.) thick washer. I may be interpreting it wrong but the illustration appears to show the bolts installed from outside to inside and with the washers under the bolt head. For a bolted joint that does not make sense to me, but that's what the illustration appears to show.

All the above comment apply to Cat undercarriage, not aftermarket which you installed.

Are the nuts thicker than the bolt heads..?
Also from your photo I would ask if those bolts are long enough. The end of the bolt should be flush with the nut IMO, not about 1 thread inside as your photo shows.

One-piece sprocket

Segmented sprocket

Dave Neubert · Oct 10, 2020

It looks like the nuts are out to far they should be flush with

Welder Dave · Oct 10, 2020

Looks like the nuts and bolts would be the correct length without the washers.

Nige · Oct 11, 2020

Welder Dave said:
Looks like the nuts and bolts would be the correct length without the washers.

Or that the aftermarket sprocket segment flange is 1/8" or so thicker than an OEM one.

John C. · Oct 11, 2020

I would put the question to the supplier of the parts and make them commit to any future problems that might show up.

Welder Dave · Oct 11, 2020

Yeah, supplier should be able to clarify unless they just ship all the hardware with washers whether you need them or not. Do sprocket segments on dozers generally use washers or just nuts? I know the torque is very important so they don't come loose and maybe Loctite is a good/better idea?

When I replaced bottom rollers an experienced shop recommended Loctite so they wouldn't come loose. I found some blue medium strength Loctite that was surface insensitive and not affected by a little oil on the threads from re-tapping all the holes. High strength Loctite might be better for sprocket segments though. Sprocket bolts coming loose can be a problem on MX race bikes too and a lot of guys use high strength Loctite so they don't ruin the hub from the bolts coming loose. It's cheap insurance.

John C. · Oct 11, 2020

The jury has been out for years on washers for sprocket bolts. Some people think that since the bolts are a one time use, they don't need washers. Others believe that flat hard washers are imperative. My preference is to go without them as I don't like to pay for extras unless they can be justified. If the manufacturer specifies them, then I use them.
The bolts usually are not a problem on the rings but many times are on the segments. In my experience, if a segment comes loose once, it will always come loose again. The normal attempt at a fix is to weld the bottom corners of the segment to the wheel. The bolts in this application don't come loose by unscrewing, they come loose by stretching. It happens because the holes in the wheel lose the tight fit and the flat mating area becomes not so flat.

Loctite might make you feel better, but in this application is does little else.

Nige · Oct 11, 2020

What we used to do on our fleet of D6's to tackle bolt loosening was to weld all the sprocket segments together once the bolts were installed and tightened, effectively transforming the six individual segments into one ring gear. Bolt stretch/loosening issues disappeared overnight.

Welder Dave · Oct 11, 2020

Did the welding affect the segments (life) at all?

Nige · Oct 11, 2020

Welder Dave said:
Did the welding affect the segments (life) at all?

Nope.

Mobiltech · Oct 11, 2020

We weld our segment ends together too. Eliminates any loosening problems. We use never seize on bolts so they torque down properly.

Nige · Oct 11, 2020

I'm always cautious about using anti-seize on a bolted joint if the D&A procedure doesn't specifically call for it. I well remember a close shave installing a 789 spindle/brake/wheel unit where the ring of (new) bolts securing the spindle to the taper on the front suspension came apart like a zipper. The mechanics had used anti-seize on the threads when it wasn't called for and the bolts had stretched past the yield point as a result of the reduced friction when pulled up with the torque wrench. In tests afterwards we found that the bolts went an extra half-turn with anti-seize over and above what they went without it when the same torque was applied. My 2c.

wee_gus · Oct 11, 2020

Afternoon gents,

sprocket segments are genuine cat, cat couldn’t supply the bolts or nuts so part number was sent to our supplier who also supply cat, they supplied the bolts and nuts.
I’m off the opinion after what nige had posted in that the bolts are on the incorrect way and nuts need to face the inside of the machine. I’ve never had this issue before but nobady we know has converted a D5K from system one to salt. Tomorrow we are converting a D6K from system one to SALT

Nige · Oct 11, 2020

What I posted is based on what I see from the Parts Manual illustrations. It's the best I can do but if I was you I wouldn't place absolute faith in those illustrations because it won't be the first time something shown in a parts manual page has been subsequently proved to be incorrect.

Also bear in mind if you reverse the orientation of the bolts that it appears from the illustration that the washers go under the bolth heads.
Have you compared the thickness of the bolt head versus that of the nut..?
A thinner head on the bolt would suggest that the washer goes under the bolt head - although I can't for a moment think of a good reason why it should be done that way.

Also I suggest to check that the bolts are the correct ones if they are non-Cat. They should be 2.1" long according to the parts list.

Nige · Oct 12, 2020

Nige said:
A thinner head on the bolt would suggest that the washer goes under the bolt head - although I can't for a moment think of a good reason why it should be done that way.

Having slept on it, unless the washer was classified in the design as a "spacer" that was necessary to get the correct amount of bolt stretch when torquing..?
Usually spacers are a little thicker than a washer, but there must be something different between the iron of the single ring sprocket and the segment-type for the bolts to require a washer in one assembly and not in the other.

I can only reiterate what I said above that in view of the bolts being aftermarket IMHO you should measure the length and ensure that it is correct according to spec - i.e. 2.1". It wouldn't surprise me at all if they were 2" TBH, because 2.1" is somewhat of a weird size. If that is the case then the 0.1" difference in length would explain why the bolts do not come flush with the outside of the nut when tightened as they should do.

Welder Dave · Oct 13, 2020

I've always seen the nuts facing out. The nuts are generally what are turned not the bolts.

Nige · Oct 13, 2020

Even if the bolts were installed from the outside it would still be perfectly possible to access the inside and turn the nuts if required.

Welder Dave · Oct 13, 2020

Depending on if the segments (or bolts) were being replaced (or switched around) with the tracks still on might be a little more difficult to turn the nuts from the inside.

nicky 68a · Oct 18, 2020

Interesting thread.
On my D8R and D8T,they both have bolts,spacer/washer and nuts.
That’s how they came to me from previous owners.
I keep them that way.The spacer/washer shows up in the parts books of both tractors and is fitted on the inside of the rim on the bolt head,not the nut.
I note Nige’s comments on the anti seize thing.I use only new engine oil on the threads of segment bolts and the torque turn method.
I’ll confess to using anti sieze compound on much bigger idler and roller bolts for the D8 and D9 tractors.
I may have been doing it wrong??

CAT D5K undercarriage

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