One for the Mechanics

13th September 2013 by Helen

After the axle snapped in Torres del Paine national park we were not going anywhere fast.  We made various enquiries about how best to fix our snapped axle.  Paul decided he would rather source one in England where he could inspect it before buying and have various treatments done in advance.  It was swings and roundabouts on price.  Whist an average axle in the UK cost less than 10% of the price of buying one in Chile by the time shipping and customs costs had been added it wasn’t much less than if we had bought it in Chile.  Add to that the cost of the three month delay that wrapped around that and the added accommodation cost whacked the price up quite a bit more.  That’s the price of confidence in knowing you’re getting what you want though.

Waiting for it to arrive proved a little nerve wracking and on 1st August Paul posted on Facebook: The axle case has moved!  It is no longer in London, but its precise location remains a mystery.  It may be in Miami (its reported location on the tracking system) or it may not, because it is listed as being zero items!  It may be in Miami but some time distant, as it is listed as arriving on 1st January 1900!  We just called a handful of numbers here in Chile, provided by the Shippers and / or the internet, all of which no longer function.  Watch this space, we have a Chilean Sherlock on the case…

It was the 11th August before he could report: The Eagle has landed.  After a journey through two centuries, over 9200 miles, and 13 days, our axle casing has arrived at our hostel. Intact.  UK cost of used casing: £30; Sandblasting and paint £40.  Crate: £100.  Getting it here: £1350.  Getting to work Monday….hope the weather holds!!!

(the journey through two centuries referring to some strange dates that appeared on our paperwork)

The weather was of course a bit of a problem.  Patagonian winter is not unlike English winter with temperatures averaging around freezing and lots of rain.  OK if you are working indoors but not in a muddy back yard where the dog spends it’s days.

By now it was necessary for me to renew my tourist visa and to get Landy’s temporary import extended as we had both been in Chile for three months.  I took a day trip on the bus across the border into Argentina which solved my problem (cost around $5.00 instead of $100 to have renewed it at the local immigration office) whilst Landy’s took just 24 hours following an email to aduana (customs).

Mechanics are never designed to go completely smoothly and there were a few twists and turns along the way.  Some of which required me to go in to Punto Arenas with an incomprehensible car parts shopping list.   The good thing was that having made contact with various shops and with the help of our English speaking landlord we were able to take advantage of the local culture of using ‘COD’ for getting various bits and pieces delivered via the local bus company.

In the meantime Paul had decorated the hostel notice board with some unusual (for hostels) illustrations.

Not the usual messages found on a hostel notice board

Not the usual messages found on a hostel notice board

As August progressed so did the mechanics – I’ll let Paul tell the story in his words taken from Facebook:
19th August: Tired of waiting.  Bought a welding set today, and will weld my own axle brackets tomorrow.  Haven’t done this in over twenty years ….. Hope it’s like riding a bike
21st August: Well, as usual, things didn’t quite go according to plan.  The additional shock mounts I shipped with the axle from the UK were the wrong ones – they were standard replacement mounts, not supplementary ones, so I’ve had two hours of angle grinding in the snow to remove the ones from the old axle case…not a pretty job, but they are usable.  The shock mounts are welded in place, but I ran out of …light, so will have to be finished off and tidied up in the morning…although I must say I am quite happy with the welding given its been at least 20 years since I last used an arc welder.  Especially pleased since I had to fill in some rather large gaps due to the cutting process.  All in all a good day.
25th August: The axle shenanigans continue! The welding all done, I turned to the mechanical side and the rebuild of the differential – no bearing puller means a difficult job of removing the pinion bearings and carrier bearings, so armed with enthusiasm, I ventured out to find a puller.  There were none to be found locally however, so I scratched around and found some metal from the old axle, and created one by using a ball joint splitter as a base.  Even so, it took a lot of brute force to finally remove the bearings.  Next step is the first fit up to establish bearing preloads, and then the final build.  This latest difficulty has cost us two days due to the weekend now being upon us.
The next day brought a new development: Well, at first glance, a 367A/382 bearing looks the same as a 367A/382S…….but it isn’t!  Our two new diff carrier bearings have the same cone (the 367A bit), but the cup (the 382 bit – the ‘outer race’) is 2mm larger diameter and about …4mm narrower than the original.  I should have checked before now, so I’m cross with myself.  I could use the old outer races, but they are not looking perfect, so it might well be false saviour to do so.    To say I’m miffed would be a serious understatement.

As he was indicated there were lots of twists and turns and quirks to deal with along the way during the fitting of the new axle.  One of those involved needing to fit shims – used to being able to get shims of varying thicknesses in the UK he discovered that in Chile they only come in one thickness: 0.25mm – reducing the accuracy of fitting a little.

28th August: Repairs are progressing!  The bearing cups we had to exchange arrived on the bus yesterday, and I just picked up the set of pinion shaft spacers I had machined up, so we are ready to build the axle.  In the meantime I took out the old leaking steering box in the freezing cold today, so we can put the new one in tomorrow.  Its not normally more than an hour’s job, especially since I’ve had it in and out four times now!

29th August: The steering box is in, and the steering wheel and front wheels are pointing in the right direction – always a bonus!  Its been cold out, and laying under the truck in this dirt yard on the damp soil has sucked the heat right out of me.  As if that is not enough discomfort, I realised today as I petted the ten year old German Shepherd guard dog living in the yard here, that the slightly acidic smell I could detect was in fact ten years of dog shit spread across the mud.   Nice!  This overlanding repair lark opens new horizons each and every day.

31st August: I don’t mind Cha Cha days too much, but today has been no fun.  One step forward two steps back!  This morning the cast differential casing was acting as an ice cube tray, with several ice cubes nestled in the castings.   Despite being the longest day of work so far, I’ve only managed to get the diff carrier preload sorted and the pinion races fitted in the diff nose.  Nowhere near enough progre…ss. I’ve also ordered a bearing puller from Punta Arenas, which will arrive by bus either tomorrow night or Sunday morning, because I have a bad feeling about needing to remove the bearings again.  I realised today that I should have shipped a new wheel with the axle – the spare wheel is busted good and proper.

And the batteries are both knackered.  I think we must have a current drain somewhere.  They are so flat they won’t charge. Grrrr,  mumble mumble, grrrr.

Another week and progress was … progressing – 7th September:

PROGRESS – at last!!
At last, the technical part of the axle build – the differential gears set up is done! 
There are four critical elements in re-building a diff, quite apart from the need for scrupulous cleanliness and patience.  Thes…e two are hard enough to achieve in a dusty small town back yard in Patagonia with a shipping deadline, but the four technical measurements have proven an engineering challenge too, which has been frustrating but fun.  The strip down revealed some bearing damage and wear on the input flange, so new parts required a complete new set up without special tools – one of my favourite challenges
I’ve never rebuilt a differential before so this was a learning experience, especially since  lack of parts availability meant incorporating a modification too.
‘Pinion bearing preload’ stops the driven end of the differential slopping backwards and forwards under load.  I sorted this by replacing the standard crush sleeve with a machined spacer and shims (the mod).  Its a trial and error measurement that requires an intelligent guesstimate, followed by ‘fit and check’ until you get it right.
‘Carrier bearing preload’ prevents the ring gear moving side to side across the axle under load.  I managed to do this using a fabricated puller, and some jiggery pokery on the existing shims, and some fancy measurements using a vernier gauge.
‘Backlash’ is essentially the amount of free movement between the gears.  The target is 0.004″ to 0.008″ so it ain’t much!  And its normally measured perpendicular to the gear tooth using a dial test gauge. I don’t have one of those, so some math, plus feeler gauges and a nail did the trick, and I measured backlash at 0.007″.  I’d prefer it to be closer to the low end, but I couldn’t face another strip down, so this is close enough for a field repair!
The exciting (to me) critical element is the ‘mesh pattern’ given by pinion depth (how far the input gear pokes into the diff housing, basically), adjusted in combination with ‘backlash’ – its like engineering juggling.  The ideal mesh pattern is one that gives the greatest possible contact area, but equally centred on the teeth of the gears., giving greatest strength and durability under load.  This achieved through trial and error shimming.  I sorted this with some new shims delivered by bus from Punta Arenas, because the original set up hadn’t required any shims.
Yesterday at about 5pm here, as the sun was beginning to fade, I finally got the set up as close to perfect as I was going to have patience and shims for.
I didn’t have any special gear test paint, so I tried a few things until I found something that works, which is why the gears look a bit ‘decorated’ in the photos.  Spray paint doesn’t work, and nor does indelible pen, but if you use a thin smear of silicon gasket seal, and act quite quickly, you can see the mesh pattern easily.  It just means taking a while afterwards to clean the gear teeth!
So today, the axle gets built up and fitted to the truck.  Well that’s the plan – but we learned a long time ago not to out too much store by plans
8th September: I discovered today that three of the rear shocks were bent in the accident, and now wont fully compress.  I need four HD shocks for the rear of a 110 Defender – don’t have to be LR.

13th September: Well, the axle is done bar a road test, including new brake lines, A frame ball joint, wheel bearings, and axle breather.  Brakes are bled, and the new power steering pump is in and bled out.
The fuel tank leak turned out not to be a gaske…t, but a popped spot weld (its a new tank!!), so I welded that up carefully – not so easy on a paper thin tank using an arc welder.
The shocks are bent and we haven’t been able ti get replacements locally, so we will limp to Punta Arenas carefully on two old shocks, and see if we can get some there.
I discovered today that we have only one good tyre.  One has a fist size hole, two have small punctures, and one is patched over sidewall damage.  I think we need new tyres
Should finally be ready to leave sometime tomorrow.

 

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