Mirror Mirror – IBM RAID had to be different

Years ago I had the pleasure of getting called out to a client site where they had some problems with their IBM Server. I needed access to the data from their Raid 1 pack running on an IBM ServeRAID controller. For some reason that eludes me there was a problem on that machine. “No Worries” I thought, I’ll just drop it in the box beside it and read off the data. It’ll show up as a normal disk on a normal SCSI controller.

Err – NO

You see whilst Adaptec and others do genuinely mirror their disks, IBM implements some type of Mirrored Striping. I don’t know and haven’t researched all the details, but the short story is that if you want to read the Mirrored disk – you need an IBM RAID Controller. I did speak to an IBM tech and was told it was for performance reasons.

Now using an IBM ServeRAID controller to read the data isn’t the end of the world – just throw it in another box (assuming you have one). At least IBM RAID is compatible across their controller model ranges.

This is where your world will now get “interesting”. You see IBM has this interesting concept where they store a copy of the RAID controller configuration on the disks. If you install RAID Pack 1 from Server1 into Server2 that already has a RAID pack (Raid Pack 2) operating, the RAID Controller (assuming there is only one for that backplane) will see two different configurations. Pack 1 knows only about itself and Pack 2 is the same.

Fair enough you say – we’ll just teach them about each other. Well – you can’t. IBM does not allow “merging” of RAID pack configurations onto the controller. This means that if you try, it’ll delete one of the packs. Fun Fun Fun. Great design effort boys.

 I haven’t seen this much brains used since Intel decided to make a RAID controller with no recovery console except for the one installed in the OS – THAT YOU CAN’T BOOT to because that’s why you need the recovery console. (I use these for doorstops)

OK, so you can’t merge, so you can’t easily swap packs between machines for quick recovery. Good marketing move, it does give a reason to keep a spare IBM box in the corner.

It also makes one of my safety tricks useless. I have on more than one occasion seen an administrator delete the wrong pack or disk on a machine with several arrays. I haven’t had it happen, but it’s entertaining to watch. It’s not that hard to do. Often the logical labeling is not the same as the physical labeling, or is inconsistent in some other way. My solution to this (assuming things are offline) is to drop the healthy pack out whilst working on the failed one. It’s very hard to make a mistake and delete something that isn’t plugged in.

BUT – if you try this with an IBM ServeRAID controller, the pack you are working on will likely lose knowledge of the offline pack. When you go to plug it back in – presto – pick one, but not both. You then start all over with the healthy pack online, and waste another two hours. Wonderful during a DR situation.

So – if you are used to other RAID manufacturers kit and get dumped with an IBM system, things are a little different.

I actually like the IBM ServeRAID kit, I just get frustrated by companies that insist on being different and make my life harder in the process.

A Safer way to Snatch

I’ve been tossing round the strength of recovery points and the techniques I see used to recover vehicles. My primary concern has always been a shackle or other piece of heavy hardware staying attached to the strap and hitting one of the vehicles or occupants at x00km/hr. A broken strap may not be fun, but a high speed steel projectile is far more dangerous.

My preference is not to use shackles with snatch straps unless it can’t be avoided. They will nearly always be stronger than the vehicle mount points. This means if the vehicle mount fails (likely from the debates circulating) before the strap at 8000KG, you’ll have 3kg of shackle headed toward you at high speed. You just supplied the projectile needed and you know it’s aimed straight at your vehicle.

A rated vehicle hook (not loop) circumvents this problem in a number of ways. If it fails in the hook itself there is little to become a missile, and it likely won’t stay with the strap. If the mounts or chassis fails there is a fair chance as it tears off, the strap will simply pull free of the hook. 

 In the situations where you have to use a shackle with vehicle loops there is a simple solution would provide a great deal of safety. Use a second strap – preferably a rated tree trunk protector – and connect it with shackles to two separate mount points on the car. Feed the tree trunk protector through the eye of the snatch strap. Now you have the situation where:
a) Each mount is only subject to approx 60% of the load (depending on the angles)
b) The tree protector is only subject to 60% of the load
c) If a mount fails the unraveling of the protector as it passes through the eye will significantly dampen the recoil of the snatch strap
d) If the mount fails the shackle and mount is still attached to the vehicle via the other side of the short strap – no projectile risk.

Safer Snatch

I don’t mean this as an excuse to fitting rated mounts, or as a reason to use the factory tie down points. BUT. We all know it happens and may be guilty here and there of doing the same. At least this way the result won’t be catastrophic and the only additional hardware is a second strap of some type.

It’s definitely a lot simpler than some of the techniques I have seen suggested with a rope at each end, and more reliable than a damper thrown over the strap.

Emergency in Texas

A tragic flood this morning destroyed the personal library of President Bush. The flood began in the Presidential bathroom where the books were kept. Both books have been lost. A Presidential spokesman said the President was devastated, since he was almost finished coloring the second one.
The White House tried to call FEMA, but there was no answer.

Microsoft Please Please KILL Share Permissions

It’s been 15 years or more since Microsoft launched Windows NT. No one has used a Windows 3.11 Server in production since Windows 2000 was around.

So why oh why do we still have share permissions in W2K3 and Longhorn? All they do is confuse Administrators and allow for weird security configurations and the problems that come with them. I frequently see mismatched configurations, confusion over remote and local access or confusion over other sharing methods such as HTTP.

There is a small supportive argument or them that goes along the lines of “but what if the NTFS permissions are wrong”. Well, lets look at the failure mechanisms.

1. Attacker has User Account and Password – Share permissions do nothing that NTFS wouldn’t – “All your base are belong to us”

2. NTFS vulnerability found – After this many years, I trust the NTFS ACL’s far more than I trust the Share Permission controls.

3. Mis-configuration of NTFS Permissions – This is generally due to an inadequate design for management of the user groups and permissions. If your change control is inadequate, Share Permissions are not going to save you. I’m working on a paper at the moment to smooth this problem out.

Microsoft, please get rid of them, they are a legacy solution that confuses many administrators.

In the meantime – Share Permission – EVERYONE FULL CONTROL

HZJ105 Radiator Bash Plate

If you own a live axle 100 Series cruiser, it’ll have the 1HZ diesel motor in it. There is also a fair chance of it having the factory alloy bullbar, or one similar.

This model (as opposed to the IFS models) didn’t get a bash plate or and form of protection in front of the radiator. If you look under there you’ll see that it is easy for any stick coming up to jam into the Air Conditioning condenser, and possibly into the radiator as well. If you have seen the 4WD Monthly video of Tasmania and the Prado with a smashed bottom radiator tank you’ll know exactly what I mean.

They also have a tendency to suck up every bit of seed and fluff through this gap and block the bottom of the radiator. As there is generally no foam seal between the cores, it gets into places that are a bugger to clean out.

I bought 2 strips of 40mm high density open cell foam from Clark Rubber for about $5 and jammed it in there to fill this gap. This is what the normal factory fitment is and I see the latest year HZJ105 has this foam installed. This will improve airflow through the airconditioner core, reduce recirculating airflow, and prevent seeds and bugs getting between the cores where they can’t be cleaned.

I then bought a sheet of 3mm checkerplate aluminium measuring 610mm x 470mm for $30. 2mm would have been adequate, as it’s only to deflect sticks, not to drop the car onto.

You can use the factory bashplate and steering damper bolts to secure the rear. The holes are all 8mm and are at 100mm, 180mm, 303mm, 474mm.

Once the rear is bolted up it is easy for force a bend in it with a bit of timber and the jack. I didn’t want to have to deal with loose nuts, so used tek screws to secure the front. Captive nuts are difficult with allow unless you have access to rivnuts.

This now keeps all manner of gunk out of the radiator. It should help prevent surges of water coming in on water crossings, and protect it from errant sticks coming up at it.

Cooling may be an issue, but I just towed 3500kg of trailer for 200km and had no worries on the highway. It got hot on the range, but it always has done so. I wouldn’t expect low speed cooling to be affected as that is primarily draw through from the fan. High speed is a more likely problem, and has been fine. The IFS cruisers have a slotted plate instead of a solid one, and it would be possible to slot this plate if it is a problem. It does block some airflow to the power steering loop, but again, I would expect this to get enough air from the surrounding airflow, and the metal is it bolted to.

Cheap easy protection.

Building a cheap 2TB RAID Server for home

I like having a bit of space to store stuff at home. Dumping the Media Centre, Music, Photos and Backups back to a central server makes sense to me. It lets me use my XBox (chipped original) as a brilliant DivX player with AC3 Surround. I also worry about losing this data, and find it impractical to back it up to CD (3000 CD’s is difficult). This is why I run RAID on my server, to help protect my data. It’s not perfect, but it’s a good start.

You’ll need an old PC. This is a great way to reuse your desktop when you upgrade. Any old piece of junk will do, but ideally it will have the following:

  1. Tower Case
  2. 300W Power Supply (250W may do at a pinch)
  3. 4 x SATA Ports
  4. 2 x IDE (PATA) Ports
  5. Any CPU – doesn’t matter
  6. 512MB RAM
  7. On Board Video preferred

The intent is to run 5 x Hard Drives and a CDROM. You can do this with all IDE (PATA) but it gets difficult to find IDE adapter cards, and their performance can be poor. You can run two drives per PATA cable vs 1 per SATA.

You want 4 drives the same size. 500GB is about the most cost effective per GB at the moment (mid 2007), but do the numbers on whatever gives you the best deal at the time. You could use 5 – 10 old smaller drives, however finding a controller to plug them all into is next to impossible. 4 x medium size drives tend to be the most cost effective way of getting bulk space. The fifth HDD can be any old piece of junk. It’s only to run the OS, and can be replaced if it dies. It doesn’t hold any data.

The case doesn’t need to have mounts for all these drives, and it doesn’t have to be anything special. If the drives are all 7200RPM, they tend to get a little warm. They should have some space between them and ventilation. If they are 5400RPM’s you can stack them together on the base of the PC, they won’t care.

As it is a server you can shove it anywhere in the house, making super silent a lower priority. If you want to build it silent see my “building a quiet PC article“. I prefer to shove it under the stairs where noise isn’t a problem. I manage it through Remote Desktop, so it doesn’t even need a monitor, keyboard or mouse.

Install Windows Server if you have it (licensed and legitimate of course) or XP onto the single small HDD. Nothing special here. If you are running XP you’ll have to do some hacks that are covered in this article on Tomshardware. I haven’t found a hack to get Vista to support RAID 5 yet. Windows Home Server should be an interesting one to evaluate when I comes out, as it has some new takes on RAID. In the meantime however, I’ll stick with Server 2K3.

The objective is to protect the data through the use of RAID. I see plenty of people with data on a single machine at home they use as a server, but most don’t run RAID. I always run Software RAID, that way if a HDD dies, I lose nothing. I prefer software RAID in windows to any of the Hardware RAID adapters for home use. The reason is simple. If you Hardware RAID adapter fails, you have to get one the same or compatible to get to your data. Being cheap equipment, this has a fair likelihood of occurring, and then not being available. Using Software RAID on the other hand means any Windows Server can read the disks, and recover the data. We are doing this for data safety, not performance. I have always found software RAID performance to be acceptable, even when I was running an old Pentium MMX 166 box.  In a business environment it’s a very different story and cost.

Once Windows is installed I recommend you configure RAID 5 across the other 4 data disks. There are instructions here.  The disks need to be the same size to participate in the RAID pack. They can actually be different sizes, but you’ll waste space on the larger disks. Now most RAID solutions support two different types of RAID to protect your data – RAID 1 and RAID 5, which I’ll outline.

Raid 1 is a Mirror. It makes a copy of one disk onto another, and shows them as a single disk. If one dies, you have the data on the other disk, and the failure is transparent. The problem is you lose 50% of your space. Your 2 x 500GB disks (1TB total) give you 500GB useable space. Not particularly efficient. To make it practical for a home server you have to buy larger more expensive disks. This is supposed to be a cheapish exercise.

RAID 5 is referred to as a Stripe with Parity. The redundant data is spread equally across all of the disks. You need a minimum of 3 Hard Drives to run RAID 5. The way the algorithm works you lose the effective space of ONE disk to the data protection. If you think about it, the more disks you add, the more efficient it is. The data being spread over multiple disks tends to make the system faster as well, disks being the most common bottleneck. Our 4 x 500GB (2TB) gives us about 1.5TB useable. It’s actually a little less due to HDD manufacturers counting differently to the rest of the IT industry, but hey, that’s marketing for you.

With your RAID 5 setup on your old PC and some cheap Hard Drives, you’ll have one of the cheapest large data stores around. You also get the benefit of knowing if one of those drives dies, your data is safe. The gotcha is you actually have to check the RAID occasionally to be sure it is healthy. You can do this by checking the system event log. There is a risk that as it all just keeps working in the event of a failure, it will continue unnoticed, until a second disk fails, resulting in the loss of everything. I am still looking for a freeware utility to alert in the event of a software raid pack error.

It should be noted that RAID only protects against one type of disaster – loss of a single Hard Disk Drive. If you lose multiple drives, accidentally delete files, get a virus etc etc, your data will be lost. As I tend to store non critical data, and use this space to backup my other PC’s, loss of this type is not a significant problem for me. This risk should be kept in mind and managed where possible. There is no cheap large scale backup for home use that I have found on the market. The ideal would be some type of 100 disk DVD Loader, however all the library’s out there don’t have integrated burners. If anyone finds a large cheap loader with a burner, I would love to know about it (another market opportunity for some Taiwanese company).

Now this machine is going to be on 24/7 and you should think a little green. Most CPU’s aren’t too bad for power when idling, even if they aren’t the latest models. The biggest energy chewer will be the HDD’s. If you go into Power under Control Panel and set the machine to shut down the Hard Drives after 15minutes of inactivity, you’ll save a heap of power, and extend the life of your drives significantly. Consumer drivers aren’t really designed to spin 24/7. Stopping them spinning also reduces noise. Overall it will probably chew about 30-50W at idle and up to 250W under load, depending on the CPU you are running. It’s not practical to enable Standby, as there is no remote wake up command.

Jasjam Stupidity

The screen rotation feature of the Jasjam is cool, but it takes a while, and some apps really hate it. It will even crash some video playback. It’s a great function for the slide out keyboard, but it is slow.

Have you ever noticed your Jasjam is incorrectly aligned when you answer the phone or an SMS message, and it takes a few seconds to sort it self out?

Well – it turns out the way the rotation is sensed is via a magnetic pickup. iMate in their wisdom supplies a case that has its lid closed by some very strong magnets. Presto – they just broke their own orientation sensing mechanism, causing the poor thing to heave  heart attack when it’s removed from it pouch, and it’s owner to wonder “why is this thing always trying to sort out it’s screen”.

Time to find a leather non magnetic case I think.

Why generators SUCK for camping

Basically every generator on the market is next to useless for the average four wheel driver. The normal generator puts out 240V. Next to nothing you need when camping runs on 240v, you need 12V. That will run your fridge, flouro lights, water pumps and recharge your batteries.

Here’s the catch. To get 240V down to 12V means a battery charger. Most battery chargers only put out 4 – 8 Amps depending on the model. Expensive versions put out 10 – 16A but will cost $150-$400. Assuming the average person uses approx 40A/H per day, that’s going to take 4 – 8 hours to be replaced.

Some generators have a 12V output. It’s rated at 4 – 6 Amps. You are still looking at 4 – 8 hours runtime.

Now lets look at a car alternator. They produce 12V directly at 40A minimum in an old car. My Cruiser is 120A from factory. Most are over 80A. It’ll recharge 24Hr discharge in half an hour (if your battery can accept that much that fast).

All your stuff runs on 12V and what doesn’t can run on an inverter for the time needed. Switch mode power supplies (Laptops, Phones, Camcorders etc) are happy running off a cheap $40 inverter. They do NOT need sine wave inverters to be happy, as they convert straight back to DC anyway. Sine wave inverters are good for things with coils in them – motors and transformers.

What we need is a  high output 12V generator based on a car alternator. Currently the only one avaialable is from Christie Engineering. Nice toy, but expensive, and a little loud, not like the quiet Honda’s. A tiny diesel version would be nice too, run it off the car fuel tank. Any chinese importers want to step up to the plate, I reckon you would have an excellent market.

I have made one in the past, but it was bulkier than the Christie unit, belt driven, and needed more HP due to the RPM requirements. ie. It’s not quite simple, but it’s definately do-able.

Quiet / Silent PC Design Fundamentals

Sites like www.silentpcreview.com offer some great component reviews for bits to build a quiet machine. What is missing is a guide about the fundamentals to think about to do it simply, without having to buy super expensive gear. This is that guide.

It’s probably a geek thing, but the “why bother” for me is that I run a home server to keep my stuff on and a noisy PC is just plain irritating. Ditto for the media centre PC, or even the desktop. Because my machines are on all the time, keeping them quiet, and power saving matters.

Interestingly enough the Corporate (not the home user crap) Dell’s and IBM’s I see through work are relatively quiet, not super silent, but not bad for an off the shelf machine.

The key is ventilation design. Move the most air you can, where it is needed, as quietly as possible.

The method to do this is quite simple. Unfortunately most PC cases and motherboards out there do nothing to help this, they just make it worse.

Lets try some basic rules

  1. Big fans move more air for less noise than small ones (listen to a 1RU rack mount server to see the ultimate of this – like a jet engine, noise is astounding)
  2. Moving air round and round inside the case is inefficient and makes noise (most servers don’t run CPU fan’s, they put decent heatsinks in the system airflow).
  3. Pumping the air in AND out is unnecessary – more noise (in 99% of cases two fans blowing out will move more air than one blowing in and the other out)

So what we want is a case that uses one big fan to pump air out (or in) and flows it past all internal components such that small fans on heatsinks are not required. It’s called ATX and was designed to solve the deficiencies of the AT design, especially those relating to cooling. Unfortunately the cases we get today aren’t really the original design.

If we look at components.

Case:
Tower cases are easier to do this with due to their natural tendency to flow air up. Hot air rises (heat does not rise, that’s a myth) You want a case that lets as much air in as possible at key points – down low toward the front. Some flowing in past the hard drives is also ideal. It should NOT have vents up high, or at the rear or  near the CPU. If it does, seal them up, as they’ll let air bypass the other components. Cases with 60mm rear fans are particularly noisy. Look for something that will take a 120mm rear fan, or if you are running a Core Duo CPU – no rear fan is needed – seal it up. Holes over the CPU are a waste – seal them up too. If your case is well designed, you don’t want fans in the front of the case.
Desktop cases are more difficult. You’ll have to plan it a little more.
Make sure either case has provision for mounting the HDD’s in rubber.

Power Supply:
This is the most important component, the thing in the original ATX specification designed to cool the system. Look for a power supply with a SINGLE 120mm or 140mm fan. Big = more air for less noise. It will be mounted in the base of the PS over the CPU – ideal. It will also leave the entire rear of the power supply as a large mesh grid – ideal for moving more air. Finally, the fan is inside the box behind the power supply electronics, this will further muffle any noise. You don’t want a second 80mm fan in the rear. This is a restriction, makes noise, and fans in series are un-needed.

CPU:
The coolest running you can buy. A Core Duo is ideal here. Also the smaller the die size, the cooler they tend to run, so if given the choice pick the CPU with the smallest nanometer size. The late P4’s are awful and need huge heatsiks to compensate.

CPU Heatsink / Fan:
This is where it gets tricky. My base assumption is that I want the airflow from the power supply to do most of the cooling. Therefore it has to have fins that face into the power supply and cool from air running ACROSS it, not down into it as most stock and many aftermarket coolers do. This one is good. This one is not. It has to be oriented the right way. The factory heatsinks that force air down onto the CPU rather than across are simply recycling hot air round and round. They rely on the other system fans to keep the system cool. Seems like a waste to me, more noise for no reason. Reviews on the internet are not always useful for this, as they test the heatsink in open air, not in a sealed forced airflow like a well designed case should be. My CPU fans often never even run.

Fans:
Buy quiet one’s, but don’t spend too much money. Centrifugal fans tend to flow more air for less noise, but are rarely available in useful sizes or configurations. Fan grills should be the thin wire style. Grilles in cases that are punched gaps in the press steel, or worse, lots of small perforated holes, should be cut out and replaced with a wire grill. Remember – larger = more air for less noise. The quiet fans simply tend to spin at lower speeds. I tend to run mine at 7V to achieve a reasonable result. 7V comes from between the 5V and the 12V rail.

HDD’s:
Just follow the recommended drive on www.silentpcreview.com. I tried a “similar” drive, and the seek noise was irritating during movies. I learnt to follow their recommendation exactly. Mount them on rubber.

DVD Drive:
I can’t find a quiet one – any one that knows please help me.

Next time you go to buy a “quiet” component, ask yourself, is this simply covering an existing problem, it this just another “quiet” noisemaker. The quietest fan is the one that isn’t there, and with careful design you’ll need far fewer.

There it is – simple. Pick the case with the holes in the right spot, put in a power supply with the big fan in the base, and pick a CPU and Cooler combination that will let you run your heatsink passive most of the time, and damn quiet the rest. Don’t install more fans than you need and make sure each is actually doing something useful. Finally add some quiet drives and presto – a quiet PC without too much hassle.

 
80mm fans – OK
120mm PS Fan – Good
60mm CPU Fan – Bad (luckily the Core Duo makes very little heat, so it spins very slowly)


60mm fans – Bad
80mm PS Fan – Bad
90mm CPU Fan recirculating – OK as nearly turned off.
High Efficiency Heatsink – OK – needs very little airflow.


High efficiency Heatsink – OK, but airflow is wrong – recirculates.


Clear exit from P/S – Good   Entire rear of PS is available for airflow.


120mm Exhaust Fan – Good, but ideal would be not at all.
140mm PS Fan – Excellent – this does most of the work.
Huge CPU heatsink – Excellent – Aligned with P/S airflow and convective currents. The CPU fan is off 99% of the time, it’s not needed.


Grilles removed behind fans improves airflow.

Web Hosting Review – Bluehost.com

We had to move Neuralfibre at Doteasy had gone to crap. WordPress and Tikiwiki both had Bluehost in their list of recommended providers. As we wanted to use both, and the features, price and other reviews were fair to excellent, went with it. These are my comments.

Package – Excellent
Price – Good
Features – Excellent
Auto Install Scripts – Excellent
Upgrades for Hosted Products – Yes – Scripted
Multiple Domains / Shared with mates – Yes
Heaps of space – Yes
eMail Limits – Good
WebMail Interface – Bad – only on weird port (But you can install and run Roundcube, and that is a good webmail client)
Help / FAQ – Excellent
eMail responses for Help – Excellent

Overall, I’m rapt.

Review – Crompton CF Downlights

 

 The website is here

These things are excellent. 15W each. AU$40 for a pack of 4 from Lighting Illusions.

They are a reflective compact fluorescent downlight. The glass cover keeps the bugs out from between the tube elements as a bonus.

Startup is electronic and nearly instant. Warm up time is minimal, about the same as your eyes.  

The bulbs are 5000K colour – Daylight. It is a very white light, makes the 50W halogen downlights look dull yellow in comparison. They look far whiter than the 3800K Warm White reflective downlight I tried.

They don’t shed as much light per watt as a straight or round tube, but not much does. For a downlight they are far far more efficient than a Halogen.

If you want to go green, with a modern unobtrusive look, these are a great product.

Highly Recommended – 5/5

Mechanical (Auto) Lockers

Now I see the topic of mechanical lockers come up time and again on lists. There are descriptions all over the place of these things, and most are right in their outcome, and wrong in their “why”. So this is the “why”.

This mainly relates to the Lokka and Lock-Rite lockers. Detroit has a similar process, however I have never pulled one apart and I believe there are some differences.

First, Mechanical lockers are NEVER locked. Any document that says they are locked is either over simplifying, or doesn’t have a clue.

They have ONE SIMPLE RULE:
One wheel will be coupled to the crown wheel at all times. The other wheel *may* do MORE of whatever the system is doing at the time, but not less. If it is placed under a load that attempts to make it do less, it will become the coupled wheel.

This is best understood from two different perspectives – internal and external.  

Internal and External Perspectives.

External

  1. When you turn a corner the outside wheel has to speed up and the inside wheel slow down. The system is driving, so no wheel is allowed to spin slower than the crown wheel. The inside wheel takes all the drive load. This unloads the outside wheel allowing it to do more (go forwards) freely – it uncouples and free-wheels forward.
  2. When you come off the throttle and start to engine brake downhill the situation reverses. The crown wheel is trying to slow the car. The load will transfer to the outside wheel. The inside wheel, going slower (more of that the crownwheel is trying to do) will uncouple and freewheel.
  3. In a straight line both wheels take the load, but neither is locked. The load actually is applied varied between the wheels, but the flex in the suspension, axles and tyres evens out the uneven power to deliver what feels to be equal torque to each wheel.

Internal

  1. The principle of operation is actually simple. A pair of drive rings are forced outward into the side gears (or outer dog clutch in some models) engaging with them and forcing them to rotate. It is not locked here, it is just that both wheels are being driven. A key point to note is why they are forced outward. The cross shaft in the middle of the diff bisects the two drive rings. They have an elongated hole for the cross shaft to sit in. This results in a portion of the rotating torque being transferred into a strong outward force – pushing the drive rings into the side gears and holding them engaged. Think of it as a wedge splitting a log – pushing the rings apart from each other. There is also a very weak set of springs to assist the process, and some dowels to keep the two rings nearly rotationally static in relation to each other.
  2. Now lets turn a corner. The inside wheel tries to slow down, and the outside to speed up. The fixed coupling of the side gear stops the inside wheel from slowing, so it starts to take all the power. The outside wheel is speeding up and becoming unladen, as it wants to go faster then the crown wheel. When unladen the outward force on that side drive ring is reduced to near zero. There is another angle manufactured into the dog clutch teeth. This angle is steeper than the one in the cross shaft. It will exert LESS force inwards than the cross shaft exerts outwards, but the principle is similar. Now that there is no outward force from the cross shaft bevel, the side gears slide over the beveled angles on the drive ring forcing it inwards against the very weak springs. This allows the outside wheel to “cam” freely forward. The outside wheel is freewheeling, the inside is driving. I could do this on my Hilux using my little finger, it takes almost no force.

The “clicking” sound from these diff’s is the dog clutch engaging and disengaging. It’s normally only audible in closed spaces like carparks.

The often commented on dog clutch teeth that are not undercut are designed to be that shape. This shape is what provides the force to uncouple the dog clutch. When driven this is overcome by the shallower cross shaft angle, forcing the clutch to be engaged.

The weakness I can see with the system is that the engagement depth with the side gears is very shallow, and on the tips of the teeth – not their strongest part. On the other hand it is engaged the full length of every single tooth – far more than the 2 or 3 teeth under load normally in a diff. I believe that under the right shock loadings it would be possible to catch the diff in a partly engaged scenario and tear the tips off the teeth, although I haven’t seen it done. The best way to do this would be vicious bouncing of the wheels transferring load side to side. Smoothly driven I never had a problem.  

The issue if the inside wheel driving, but the outside wheel braking does result in some rear axle steer under throttle transition. It is evident partly as bush compliance moves the axle, and partly as a slight understeer effect. I noticed it mostly with the large throttle movements from cruise control on winding roads. In a long wheelbase Hilux it was not noticeable under normal conditions. I never had a problem with it towing trailers on steep roads.

In the wet there is an increased propensity to spin up the inside wheel, BUT and this is a big BUT, only to the point where it was going as fast as the outside wheel, then they both drove out of the corner. There was never any significant loss of traction toward oversteer.

I could never see any reason why tyre wear would increase. The unlocking is so gentle I could do it with my finger. The inside wheel would do more work, but the outside less, and as I go around as many left as right corners, this wasn’t a problem.

Documents like these mislead people (since removed) about how mechanical lockers work. After my experience with ARB airlockers, I know I would prefer the mechanical in the rear.

There is long discussion on mechanical lockers here, but you’ll need to read it a few times to catch all of the details.

My personal preference is an AWD car, with a Torsen LSD in the centre and electric locking. A mechanical locker in the rear and a Torsen in the front, preferably with electric locking over the top. Unfortunately I can’t buy this combination.

NOTE: In the diagrams below clearances and angles are exaggerated for clarity. The actual cross shaft hole is eccentric rather than triangular. The side gear teeth slots are a much closer tolerance to reduce lash.

 

 

 

 

MS Office team to be shot – MS Project 2003 Auth

I firmly believe one of the reasons MS holds the position they do is due to their control of the Directory, and their integration with it. MS thought so once too, and tried to extend it to the Internet with Passport.

So why oh why then does this MS product NOT support any of the normal UI’s for authentication.

MS Project 2003 Professional connecting to a MS Project Server 2003.

It gives the option of connecting with your domain account, or using a “Project Server Account”. Here comes the crunch. NEITHER of these options works on a PC that is not a domain member. There is no popup UI to ask for a password.

Now, many many projects I know of are managed by external consultants, working for other companies, with laptops managed by IT teams that are DEFINATELY NOT on our domain.

Glad to see the thinking caps went on for this one boys.

*sob* My small compressor feeds my feelings of inadequacy (or why you should install a regulator)

It’s only the ARB one that came with the lockers and it takes 127.35 seconds per tyre instead of the 124.28s of the other one. I’m never going to get a girlfriend with that sort of performance.

OK – so it’s not real fast, and I am real lazy. Pumping up tyres, bending, checking pressures, inflating still, checking again etc. It’s all too hard. A faster compressor would help, but I prefer the Shell digital auto inflator thingy – drive up – attach – tyres are set. So simple.

My solution, no matter what the compressor. Go to your local air supplies or hoses and fittings shop and buy the 2nd smallest regulator they sell, with a matching gauge and any adapter fittings you need. You’ll spend $50 – $60.

Attach it to your ARB or whatever compressor you have that has a small tank and cutout switch – it needs those, but if you run air lockers, you already have them.

When you want to inflate your tyres, set the regulator to the desired pressure – clip the hose to tyre one. When the compressor cuts out, you know it’s time to detach and move to tyre 2. No checking and standing round. I do it whilst having a coffee and giving the kids a break after hitting the blacktop again.

I could put in a huge tank, but unless it’s big enough to inflate 4 tyres without the compressor then it’s not going to help, as when it depletes it will slow the remaining inflation time to the same as not having a tank at all.