Happy New Year everybody, I hope you all had as enjoyable and non-productive a time as I did over the Christmas period.
It has been a while since the last post. I have been doing plenty of smaller jobs, which were repetitive and involved lots of cleaning. So I have only really just got enough content together to fill a blog post without it being ridiculously boring, so here is just a moderately boring post.
Thus far I have cleaned: axle casings (3x); final drive housings (2x); stub axles (4x, more to go); spring platforms (4x, more to go). None of those involved anything more interesting than painting on some de-greaser and blitzing off the thick gunk with a wire wheel, it was pretty messy so I don’t have any pictures either. Moving on.
Here we have a hub assembly, contents are a very pitted brake disc, 2x wheel bearings, a hub, an oil seal and some 14mm double-hex bolts.
Here is the rear of the hub, it’s a very simple thing. You can see the rear of the brake disc is more pitted than the front, if possible. The Land Rover service manual states that 13mm is the minimum thickness the disc can be. I suspect that if I machined the pits from the disc it would be less than that, not to mention I would have to either find or build a lathe to do it. Doing so would cost more than the £35 to replace the disc, so frankly there is no point, so it’s going in the bin.
I couldn’t pull the oil seal out as the seal and the hub had corroded together, so I just moved on to knocking the wheel bearings out. If you haven’t got a bearing puller (which I haven’t) a hammer and chisel will suffice. Place the chisel squarely on the outer race and hit it with a hammer. Because the bearing is interference fit the tolerances between the bearing outer race and the hub are very tight, in fact there is almost no tolerance for distortion in either the race or the hub. The hub has a shallow taper to allow self-centring of the bearing as it is driven in (it also reduces the effort required to drive it in), damage to this could cause the bearing race to be seated incorrectly when re-fitting. This would inevitably lead to premature failure of the bearings. To minimise the risk of damage to hub, I knocked the bearing out using the uniform pattern of North, South, East, West.
I then flipped the hub over and did the same for the other bearing race.
Voila, as you can see the oil seal (on the left) also came out.
I don’t think I would like to remove the bearings after having removed the brake disc. The brake disc just gave the hub a nice wide base so no accidents occurred. So when it comes to putting the hubs back together, I will put a disc on first then…. Having just written that, in hindsight, it would have been better to just leave the old discs on until I had put new bearings in. Oh well.
Anyway, to take the disc off it was just a simple case of removing the 14mm double-hex bolts.
This is the method I used:
A wrecking bar through the wheel studs, I put my foot on the wrecking bar whilst using the breaker bar to undo the bolts.
Finally, it’s just a case of knocking the disc from the hub (hit the disc only). Again, the disc is on a taper, so hit the disc where the smallest gap between the two is.
Done, one disc and one hub.
Repeat 7 more times!!
After having blunted my chisel by removing 16 wheel bearings, I cleaned one up to to have a look at the state of play.
As you can see from the picture below, clearly the metal in the outer race is very hard as there are no indentations on the surface from where I put the chisel.
There are many types of bearing, the Discovery wheel bearings as well as most other wheel bearings are examples of tapered roller bearings. Where cylindrical roller bearings can only take radial loads or thrust bearings can only take axial loads, a tapered roller bearing can accept both. The angle of the taper gives a rough indication of the relative magnitudes of the radial and axial loads. For instance a tapered bearing that more closely resembles a cylindrical roller bearing (such as this bearing), means radial loads are larger than the axial loads. The radial loads in the case of wheel bearings are the weight of the car, road surface inputs, acceleration/deceleration, weight transfer when cornering or a combination of the above. The axial loads arise from centripetal acceleration the car experiences when cornering, which in turn is proportional to the square of the tangential velocity.
We can corroborate the above by looking at the Discovery and it’s bearing arrangement. The Discovery has two bearings per wheel**, which is an indicator that the weight of the car is high, or the bearing loads are high due to a large wheel off-set. Anyway, the Discovery is a heavy car (c. 2.2 tonnes) and isn’t sporty, so can’t go round corners particularly fast. Radial loads can therefore be expected to be quite high, while axial loads will be low, relatively speaking. Putting some rough numbers to these, the car experiences 1g vertically whilst sat still, and would probably struggle to achieve more than 0.5-0.6g laterally whilst going round a corner. However, whilst going round the corner weight is transferred to the outside wheels increasing vertical loads on those wheels and bearings. Also, since the bearings are inboard of where the wheel mounts on the hub, a moment will be generated about the outer bearing effectively loading up the inner bearing more. So it may be fair to estimate that the radial load rating on these bearings is roughly twice the axial load rating.
**Bearings are not necessarily always of bespoke design, most of the time it is cheaper to look up bearings in a catalogue to find the appropriately sized bearing for the application (after having completed the requisite calculations). It would be possible to find a single bearing that is capable of withstanding the design loads, but it would probably be quite large in size. Which means large hubs, large brake discs, increased un-sprung mass, increased moment of inertia of rotational parts, which then requires the engine to produce more torque to accelerate the car at the desired rate etc etc.
The picture below shows the mounting face of the inner race. There is scoring on the face, which indicates that it has been spinning on the stub axle (the correct term for this is smearing I believe). This is not ideal, and is probably caused by the interference fit between the stub axle and the bearing being a bit loose. This in turn possibly implicates the stub axle as potentially being faulty, so I’ll need to measure the stub axle to make sure it is within tolerance.
The picture below shows the outer race, there is definite banding on the race. In the centre of the bearing track, there is a very polished strip, which is flanked on either side by brownish bands. There are also some faint markings created by the rollers.
You can sort of see everything in the above picture, I took another photo and played with the brightness and contrast. It shows up some of the defects more clearly.
The shiny band in the centre is caused by metal on metal contact, which is caused by lack of lubrication. The brownish hue has probably been caused by the heat of friction caused by metal on metal contact, again due to lack of lubrication. The small marks on the left are pits due to dirt that has come between the rollers and the race. As the roller has run over the dirt, it has largely increased the contact stress on the race (due to the small contact area of the piece of dirt) causing an indent. The faint lines highlighted on the right have been caused by the rollers themselves. It is an example of Brinelling (the process of indenting a hardened surface). The indents are possibly a result of impact damage to the bearing, or as a result of the car not moving for a while. Either way, the bearing is starting to show signs of impending failure. I haven’t checked the other 15, but I may do now after having looked at this one. I may find something even more interesting. Just as a final point, I took this bearing from one of the spare axles I had, so it has been sat un-used for a few years.
I think that’ll do for bearings for now.
Another job I have done is to strip down the swivel pin housings and give them a bit of a clean up. The picture below shows the passenger side swivel pin housing and stub axle.
As you can see it is quite grimy. There is also a fair bit of rust on it.
There is some congealed grease inside it, but most of the grease has ended up on the outside.
I haven’t yet checked the swivel bearing housing thoroughly yet to know if that caused the seal to perish. So for now, I am going to blame it on rust in the seal seat.
Anyway, to disassemble the pin housing, start by taking the bearing off the top pin. Then remove the top pin and shims. Keep the shims, as it is useful to have a good selection for when you re-build the swivels.
Then remove the backing plate by undoing the 19mm nut which is on the lock stop bolt and the 8mm bolt at the base of the housing.
I am undecided whether or not I will put the backing plate back on. In all honesty, I probably won’t bother.
The next job is to remove the bottom pin, which is held in by two T40 Torx head bolts (don’t forget the various filler/drain plugs of which there maybe 3 or 1 depending on the age of your axles). Here is everything laid out.
After a fairly thorough degrease, we can get an idea of the level of rust on the housing. As you can see, there is a fair amount, although it looks worse than it is. The picture below shows the area around the filler plug.
This photo shows the area around the bottom pin. The best tools for the job (or the tools that I used for getting the worst off) were a drill with a wire wheel attachment and a hammer/chisel. The hammer is good for fracturing the rust away, whilst the wire wheel is good for buffing off after using the hammer.
Here is a picture after about 10 minutes work. Again the first is around the filler plug.
The second is around the bottom pin hole. Not too bad.
It isn’t finished yet, but when I am happy that I have got all the flaky stuff off, I will soak it in a rust remover for a while to remove the rest. Then it will be ready for painting. I will go for something chip resistant for definite, although I am not sure on the colour yet. I will also probably wait to paint it until I have got my tent up, so I can set up a drying area inside it.
I also conducted a little experiment with some vinegar to see how well it removed rust. I dropped the shims into some vinegar and left them to stand. The picture below is after 24hours… The vinegar did not really do a whole lot in that time frame.
Below is a picture after 36 hours and some sand papering. The vinegar clearly loosened the rust as it took no effort to remove most of it.
Finally, I took a trip to Tomcat to see some progress. Here are a few of the photos I took. The skeleton is partially welded on.
It is still awaiting it’s rear cross-member, but it is looking likely that it will be coming home very soon.
Anyway, I think I should wrap up now. Next time will be a continuation of cleaning things up and preparing for the re-build. I might even have got my frame by then as well. It is getting exciting!
