Zel's Fleet Blog - BX, Jag XJ-S, Sinclair C5, Mercedes 208D & 230TE, AC Model 70.

[xantia_v6]

You should be able to remove the alternator with only needing to disturb the one belt. Probably the path of least pain.

[Zelandeth]

Now for one of our irregularly scheduled occasional distractions.

While it's very unlikely anyone remembers, a few months ago I was able to get hold of a HP12C calculator. One of the Voyager series from the early 80s thanks to a friend picking one up for me that popped up on Facebook Marketplace.

The 12C is a bit of an oddball in that it's heavily specialised for the business and financial sector. Upon its introduction back in 1981 it almost immediately became hugely popular - to the point of becoming the defacto standard...which is why you can still go out and buy a brand new HP12C today. Yes the underlying hardware has gone through a few revisions, but it still works exactly the same and save for a slight change of the colours and updating a few keypad labels it still looks exactly the same. I believe mine dates from the mid 90s based on the handbook that came with it.



The Voyager range contained five models.

10C: A basic scientific calculator. This wasn't produced for long as it wasn't that much cheaper than the next model up despite lacking a lot of the features. Produced from 1982-84.

11C: Mid range general purpose scientific calculator. Produced 1982-89.

12C: Specialised for the business and financial sector. Produced from 1981 to the present day. Being HP's longest and best selling single device to date.

15C: An advanced scientific calculator. Produced 1982-1989 with a limited re-release in 2011.

16C: Specialised for use in computer programming applications. Produced 1982-89.

These have all got quite a following among collectors. The 12C being made in such numbers means that while they *do* change hands for substantial sums of money, if you're patient one will probably pop up somewhere. The rest of the range having been out of production for 30 odd years though means they are rather more sought after and finding cheap ones is harder. It's not unusual to see buy it now prices of around £250 on eBay for most of the. (The 16C seeming to command the biggest premium), so I'd generally considered them out of my reach.

Until a slightly cosmetically challenged 11C popped up with a reasonable-ish buy it now...I made an offer, it was accepted and a few days later I had this in my grubby paws.



First photo taken on that desk since I installed the new lighting a few weeks ago too.

I've always liked these...RPN, nice form factor, really nice keypad, but the 12C isn't really great as far as being a good one to grab because of it being so financially orientated. The 11C though should be far more usable. There is *absolutely* a learning curve though if you've not used one of these before!

The display does have a bit of bleed but it doesn't seem to affect the usability. The self test function - yes, these have a self test function (hold down the multiply key when turning the power on)...



...Turns on all the display segments to indicate a successful test. Like so.



The only indicator really affected is the one to show the blue "g" function key is active. Not going to worry about that.

Definitely an interesting little calculator and one I'm really glad to have got hold of. One day it would be nice to get the whole lineup (16C at least), but barring lottery wins that ain't likely to happen! I'm surprised I found this one to be honest even if it's a little scruffy cosmetically.

Back to the cars next.

[xantia_v6]

I am fairly sure I have an HP12C in a box of junk in the storeroom. It came from a boot sale, bundled with a couple of 1980s Casio scientific calculators, one of which I wanted. I would not have paid more than £5 for the 3.

I learned to use a calculator with my brother's HP35 which he bought in 1973, soon after its launch. He was still using it 25 years later, but some of the keys were no longer tactile.

[Gibbo2286]

All too fancy for me. I've got this which I must have had on the shelf above my desk for over thirty years, still works.

[Zelandeth]

Actually had a few consecutive hours available today so flipped a coin between pulling the alternator on the Jag (which has of course started working again) and delving into the diagnosis of what's going on with the Merc.

Merc won.

Step 1 I decided was to have a proper look at the camshaft. I knew a couple of lobes were badly scored but wanted to see what state the bearings were in - I had a feeling they were likely to be shot and haemorrhaging oil, hence the less than stellar pressure at a hot idle.

Off we go again. Getting used to doing this now!



Let's have a peek at what lies under each of the rocker assemblies one at a time.

So what's behind door number 1...



Pretty much exactly what I was expecting to be honest.

An impressively scored up bearing with a lot of slack, which you can actually see looking closer. Pretty sure you shouldn't be able to slot a finger nail between the camshaft and the carrier.



Don't think I need to get a Plastigauge out to confirm there's too much free play there.

The cam followers feature some pretty epic scoring as well...the deepest of which must be about half a millimetre deep.





Number 2 was pretty similar, though with slightly more severe bearing scoring, cam followers were *slightly* less mangled.





This was the first one where I couldn't remove all of the bolts from the rocker frame itself because of how much carbon buildup there is in the bolt holes!

Number 3 however was where things got real exciting...

The cam followers are utterly wrecked, both inlet and exhaust.





That however pales into total insignificance compared to the state of the camshaft...



Wait...that doesn't look right, let me move a bit to get a better look...wait...what the? Oh hell...



Yep... pretty much the entire cam lobe of the number 3 inlet valve has been totally *obliterated.*



I'm pretty certain this is the most mangled non-broken camshaft I have ever seen... it's *definitely* the worst I've ever seen on a running engine. Never mind one that seemed to be running quite happily aside from being a bit rattly. That's easily 5mm plus change of material that has been worn away.

Number 4 also has quite a lip on the exhaust valve...which would have been impressive wear if we hadn't just seen the above photos.



Number 4 inlet actually looks normal!

The followers on this one were probably the least badly deformed of the lot, though that's not saying much.



Goes without saying that the whole camshaft assembly inboard of the timing sprocket is scrap metal. Well I don't think it is actually...this is more the sort of artefact that should be hung on the garage wall as a warning to future generations!

I did start the engine up with the rocker cover off briefly simply because I wanted to confirm we did have good oil flow up there, as there's obviously a load of damage been caused by oil starvation or *severe* contamination. We do - in fact so much oil is gushing out from around the rear two and front bearing that it totally overwhems the drains in the respective areas of the head and starts flooding over the top of the head after the engine has been running for about five seconds.

Probably why everything under the car looks like this and why so much was pouring out before the rocker cover seal was changed.



Definitely plenty of oil getting to the camshaft now...



Though sadly too late, this hardware was mortally wounded years if not decades ago.

There's like 1/8" of this gritty sludge just caked over everything.



If you remember back to when I first set the valve clearances I checked and found that the spray bar which runs above the camshaft was about 70% clogged, with the front most jet being the only one that was working properly. This ties in with where the most damage seems to be...so I'm calling on oil starvation as the main cause. The lack of zinc additives in modern oils probably hasn't helped given the cam follower design. A separate additive will definitely be going in with the oil once this mess is sorted out.

It's a bit hard to see, but in person you can make out glittery residue in the head valley around number 3 far more than anywhere else, which supports the thought that the mangled camshaft may be where a lot of the glitter I found in the oil had come from.



So if the bottom end has survived, we might just get away with a head swap.



Before going all the way down that lengthy road (being used to OHV engines a head swap on an OHC engine feels daunting!) I'd really like to take a look at the condition of the engine bottom end. Simple enough to get a quick health assessment done, drop sump, pop a couple of bearing caps off and see if we can see copper and if the crankshaft looks smoother than the surface of the moon. Simple enough.

Oh.



How the bleep do you get the sump off this thing? There's a stinking great cross member in the way. Sump appears to go back to about the red marker in this photo, a good foot or so behind the front of the aforementioned metalwork.



Even if I could figure out how to get to the half dozen or so bolts buried above it and removed the engine mount attached to it... I'm not convinced I'd have enough clearance to pull it out.

Think I need to go do some reading to figure out what really simple trick it is that I've missed...or getting the sump out will wind up with me 3/4 of the way down the road to removing the engine...by which point I may as well just take it out anyway! Feels like I must be missing something though given how serviceable most things on this car seem to be. I did wonder if the sump was split into a front and rear half, but if so I can't see the join.

Definitely an instructive day...and kinds good news in a way. The camshaft being so chewed up to this extent definitely would have an impact on oil pressure I'd think and we've definitely found a likely cause for the glitter. It's just possible the bottom end might have survived...

Either way I want to check the condition of it before going to the trouble and expense of a head swap. Plus given the amount of grime in and around the top end I fully expect the sump to be as bad or worse...and worry about the oil pickup strainer.

Now I just need to figure out how the fluff to get the sump off! Simple right?

[Hell Razor5543]

Jeez! That camshaft is right royally b******d! Mind you, the fact it is STILL running shows that that engine WANTS to live. If (or, more likely, when) you get it properly running it might be worth sending pictures to Mercedes, just to show them how strong these engines are.

[white exec]

What appalling oil and service regime (if any) was that poor engine subjected to?
Apart from the destruction of bearing surfaces, the cruddy 'varnished' deposits on the nearby surfaces suggest a pretty-much non-detergent oil, and absence or neglect of filtration.
Just incredible.
Have seen engines with 200,000+ on the clock looking clean and undamaged.

[myglaren]

Amazing that it was still running. Some epic wear and tear there.

[bobins]

You sure that camshaft wasn't just Mercedes' take on Variable Valve Timing technology ?

[Zelandeth]

What appalling oil and service regime (if any) was that poor engine subjected to?
Apart from the destruction of bearing surfaces, the cruddy 'varnished' deposits on the nearby surfaces suggest a pretty-much non-detergent oil, and absence or neglect of filtration.
Just incredible.
Have seen engines with 200,000+ on the clock looking clean and undamaged.

My guess is that it spent a huge portion of its early life run on cheap mineral oil that was never changed.

The low zinc content in modern oils probably didn't do anything to help, though once the hardened surface of things like the cam had been damaged it was just a matter of when rather than if things shredded themselves.

I think this is the first time I've seen varnish on what are meant to be bearing surfaces!

Regarding the sump, not great news it looks like after some reading. Mercedes (admittedly not unreasonably) simply didn't consider removal of the sump to be something what would be needed during normal servicing. Only time they would expect it to need to come off would be during a rebuild, which would be done out of the car. The solution to removing it in the car (and the general advice seems to be "don't") is to unbolt all the engine mounts, stick the engine on a crane and lift it as far as you can without the gearbox smacking into the bulkhead. Which requires removal of enough bits that you're about 3/4 of the way to having the engine out anyway. Even then it's a fiddly swear fest of a job to get out and several orders of magnitude worse to get back in.

Hmm. Need to have a think about the best way forward.

[RichardW]

That's picture of the year for the wear to that cam!

Pretty sure Jim's got an engine crane....

[mickthemaverick]

If he hasn't Zel, I have at the mancave in Berkhamstead! Shout if you want to borrow it!!

[white exec]

Zel,
Are you still stuck for the typeface for the speedo' drum on the BX ?

I have tried Identifont etc, but difficult to ID characters from just a very few numerals visible, so no real joy there.

FontViewer on a PC allows any text to be sampled across all the fonts on the device.

Typed in 10 20 30 ....80 into Word, and flicked through the hundreds I have here. You need a very Condensed font; ones that caught my eye were:
Asimov
Bitmap
Compstyle
Creepygirl (!)
Diamond SF
Gloucester MT
Pledge
Plover (font family)
Robotype
Spellbound
TrekkerFrontier
Westminster

My guess is that the typeface for the drum was purpose-designed, and not a stock font. May be wrong.
Could you lift off the film, scan it, and just tidy those numerals up? The other things on the drum look pretty standard faces.

Bet you've sorted this by now...!

Sometimes, a 'facelift' scores over originality. This something I did for our XM a long time ago...

[Zelandeth]

Cheers Chris, I'll have a look at those. As you say though I guess it may well be custom designed.

-- -- --

Somewhat frustrating day here. Well on the Merc front anyway.

I wanted to have a look at what the journals under the camshaft looked like. More for the sake of my curiousity and because everything at this stage is an education.

Now this is where I fell into a trap that it sounds like many people working on these engines have. The only OHC engines with chains I've messed around with had tensioners which were either manually tensioned or ran off oil pressure. As the camshaft is keyed to the sprocket, provided I didn't let the chain go slack so it could slip at the bottom end it shouldn't be an issue.

Yeah...oops.

Turns out the timing chain tensioner on the M102 engine is near aerospace levels of over-engineered.

Tensioning method number 1 is an oil pressure actuated plunger as I'm used to.

Tensioning method number 2 is a spring based setup as a backup and to ensure it doesn't go slack when the engine isn't running.

What's caught me out is number 3. There's also a ratchet mechanism which means that the tensioner can add tension to the chain as it wears, but there's no way for it to go the other way...the only way to reset the thing to take tension off is to completely dismantle the tensioner. Which involves quite a bit of faff.

So I've now managed to move the car from "sick" to "non runner."

I did have the sprocket tied up, but apparently I gave enough slack that it now won't go back on.

Great.

I have read up on how the tensioner works, but working through such a small gap looks like a right pain. Hopefully I can get back to where we started out again tomorrow.

Oh, the camshaft bearing journals are scored to hell, exactly as expected.

Judging from how many stories I've read of people who have had things like snapped camshafts or timing chains after work on it or head gasket changes even done by professional garages, I'm far, far from the first to make this mistake.


The transparency film I'd been waiting for to sort the dash on the BX arrived.

Thankfully because I was working on a scan I had taken I knew the dimensions would be right when I printed it. Didn't look too bad at first glance (yes this is the wrong way round in the photo).



Though precisely as I expected opacity was clearly going to be a problem. There was also an issue with boundary alignment between black and coloured areas. I knew this sort of thing was going to be stretching the abilities of my printer so this was not a huge surprise.



I'd already got a plan in place for this though - and was one of the reasons why I made the image in several layers.

I printed this in several layers (from back to front):

2X with the colour filters and black borders (coloured areas slightly oversize to ensure the edges are pure).
1X with the borders and legends on.
1X with the borders only.

The result looks like this when held up to the light, looks a lot more convincing I think you'll agree.



I was just holding the sheets together by hand there which is why I have obvious registration errors visible.

With everything back into the panel it looks far better than the blotchy, faded original ones.





Such is the curse of digital cameras that it's really hard to get an accurate looking photo of how it looks when lit...but this is vaguely close. Colours still look more washed out in the photo and the hotspots aren't really that pronounced.



There is more of a hotspot than with the original filters but personally I don't find it objectionable. If that was an issue it would be easy enough to slot in a diffuser of some form behind the filter stack.

Opacity was going to be most critical on the left hand light bank as one of the dash backlighting lamps is behind it. So looking at this in the dark was going to be important to see if I could see the light bleeding through.

Using the night mode on my camera to obtain a really overexposed photo allowed me to confirm a solid "nope" on that. Exactly as I hoped.



The edge lighting on that panel for the car diagram is actually far more subtle, this is more accurate in how it looks.



Might get that dropped back in tomorrow. LED illumination hasn't been done yet, but I've too many projects going on right now so could do with it back in the car and off my workbench. Hoping in daylight I can get some better photos too.

[white exec]

On the hotspots, you could try a diffusing sheet between lamps and display, maybe.

On the lack opactity for the black, maybe try
- a double printing of the same sheet, if the register on the printer is good enough
- use two sheets of the same print placed together (maybe one of them mirror image, to keep the two layers of toner in contact)
- varying the fuser temp (paper type) of the printer - my guess would be to a slower (higher temp) setting
- using your laser print of the black as a contact film to LITH FILM, which will give jet-black when processed
Anyone making traditional litho plates with UV should be able to do this. Screen printers would have similar kit.

Looking good, though.

On the chain tensioner, I remember those on Rover P6 4-cyl having all those widgets
- oil pressure push
- spring loaded, for engine off and start-up
- a combined ratchet/stepped wear compensator, which also incorporated a rear-end Allen key hole for manual retraction of the ram-shoe, so tensioner or chain could be removed. The hole for the Allen key was quite small.
Placing a temporary wire loop (cable tie nowadays) around the tensioner was recommended to prevent the ram accidnetally popping out during removal or installation.