Steam Lorry! – Wilesco D320 (Initial Run Review)

So it’s that time of year again, the time when I normally lose control of my wallet, perhaps. This year was particularly unforgiving, especially seeing as I’d just spent a bunch of cash on the 3/4″ Maxitrak Allchin all the way from the UK.

Nevermind, the heart wants what the heart wants and so here is the outcome/result/consequence:

The Wilesco D320 Steam Lorry!

What have I done…

So after reading some fairly mixed reviews of this Wilesco live steam vehicle for some weeks, I had finally settled on it (with some persuasion from my loving wife – aren’t I ‘lucky’ or doomed!?). It was basically a toss-up between this, or the Wilesco D305 Fire Engine. In the end, it seems the (much more expensive) Steam Lorry won out…

This is the third Wilesco I own in my collection now (the other two being the D405 Traktor and the D365 Steam Roller), and I must say, after having owned this Lorry for just-on 24 hours, and only having it run it once so far, it’s a keeper!! To put it into some perspective, price-wise, it is about double the cost of any Wilesco live steam model I’ve owned previously, and about half the cost of the 3/4″ Maxitrak Allchin Tractor (which is, rightly so, still in a league of its own).

Read on for a more detailed review of this beast!

What’s under the hood

The Wilesco D320 Steam Lorry is powered by Wilesco’s standard single cylinder steam engine, vertically mounted, and plumbed to a rather attractive brass upright-style boiler, allowing the engine to be driven with less issue over gradients.

The engine is actually mounted inside the driver’s cab towards the rear and is mounted centrally and longitudinally on the frame of the Lorry. The crankshaft passes rearwards to the externally-mounted flywheel which is mounted just outside the rear of the cab, again longitudinally.

From the flywheel, there is a pinion which meshes with a larger spur gear (both the pinion and spur are PLASTIC however they appear to be made of good quality plastic, similar to those gears seen in RC cars). From the spur gear,  a pair of bevel gears (again plastic) rotate the drive 90 degrees so that the resulting drive shaft protrudes just fore of the left hand rear wheel. A simple chain drive arrangement then carries the drive the rest of the way to the left rear wheel, the only wheel of which is driven.

All-in, the drive train seems fairly robust and should be able to cope with the stresses of driving not only the Lorry, but of any additional loads and trailers that may be attached in future.

The frame (or base if you will) of the Lorry seems sturdy enough as well and has very little flex considering the overall weight of the empty Lorry (3.1 kg according to Wilesco).

I will get to the actual performance a bit later in this post, but suffice to say that the little single-cylinder steam engine does a good-enough job of powering this behemoth along even with load in the rear tray, but this does come at a cost of a LOT of Esbit fuel tablets!!

Control system

As I purchased the model (only yesterday!) one of the gents behind the counter exclaimed “A radio-controlled steam engine! Who would have thought of that 20 years ago!”. And rightly-so, Wilesco haven’t done too terribly by fitting their radio-controlled unit to this model, as standard equipment. It only actuates the steering system of the Lorry, but the idea is that once the throttle is set and the fire is stabilised with a good head of steam onboard, one can simply sit/stand nearby and issue commands courtesy of the 40Mhz radio unit and guide the Lorry on its desired path, without having to constantly chase after the model to steer it this way and that. You even get indicators that blink when issuing left/right turn commands!

Now, before I go too much further, this is perhaps the only part of the model that didn’t exactly win me over 100% when I first un-boxed it. I certainly had some teething issues which I will go into shortly…

I had read of issues others had encountered with the RC system and I promptly encountered the same (and more! :() upon loading the RC unit with fresh batteries and trialling it out on the dinner table (well before I intended to steam the model itself).

The main issue (that I had already known about) was that the servo motor in the RC box wasn’t up to the task of steering the wheels left and right with the full, stationary weight of the Lorry loaded upon front wheels (it must also be noted that this was even before I had filled the boiler full of water, so in theory, it wasn’t at its full weight just yet either). Not only that, but left turns resulted in the long steering rod flexing rather alarmingly, caught between the resistance of the steering system and the torque that the little servo motor was trying to exert.

OK, not a big issue I thought…as once the Lorry was moving the steering system should work OK, and I tested this as well by rolling the Lorry along by hand before steaming it up and trying-out the steering.

BUT, the next issue (that I honestly wasn’t prepared for!) was that left turns seemingly did not register when commanded from the handheld radio control unit. I fiddled with the antennae, checked the ground connection, battery levels, orientated the controller this way and that around the model, all to no avail. Right turn commands would be registered just fine however, so it seemed the issue lay in the handheld unit itself, rather than a control signal/receiver unit issue perhaps.

So, after about 30min of fiddling (including trying completely different batteries) I was close to considering calling up Wilesco/my local hobby store, when I decided to take the plunge and dismantle the handheld radio control unit. :o

Once I had the covers off the handheld unit and was left staring at its internal circuit board, I found the issue fairly quickly and I’m glad I did: basically the plastic fitment of the controls prevented the steering control stick from travelling far enough to close the contacts for the left turn switch inside the controller!! The fix was to remove the bulbous control stick (they simply pull-off) and file down the plastic so that it could travel slightly further before it contacted the external casing of the controller – we’re talking millimeters here.  A quick test whilst everything was apart confirmed that left-hand turns were now registering 100% reliably and without issue, and I proceeded to screw everything back together. Yippee!

So, after all that head scratching and fretting, I had the control system issues under control (pun not intended!) and I was ready to steam!!!

Steam up!

So what’s it like steaming-up this big Wilesco Lorry and driving it around? I’ve placed my thoughts below, from initial preparation, to steam-up, to after-run!

The boiler takes almost 200ml of water, which, while somewhat on the low-side compared to Wilesco’s other models, is just reasonable in practice. I use filtered water from a food-grade charcoal filter, with perhaps a touch of tap water added (but only a touch!). (note: I am seriously considering purchasing a water distiller soon, as proper “distilled” water is almost impossible to find around my area.)

The boiler is fitted with an unconventional sight glass setup which I’m not particularly fond of, but it’s better than no sight glass at all: the sight glass(es) actually consist of two ‘port-holes’ mounted vertically (one a short distance above the other) on the side of the boiler. The idea is that you fill the boiler until water appears in the upper-most sight glass. Then as you steam about, you watch the water level until it reaches the lower glass, and that’s when you know it’s time to shut her down and refill the boiler or end the run. That’s the theory; in practice, it works just OK, and involves a bit of head-scratching at times to ensure the water level is sufficient. From what I’ve ascertained so far, there’s about 50-60ml of water remaining in the boiler when it appears in the lower sight glass – a good time to abandon the fire!

Anyway, more on that later. Once the water is filled into the boiler, I close off the boiler by fitting the safety valve, give the valve a quick pull to verify it’s not stuck, then make preparations to oil-up, followed by lighting the fire!

Oiling-up is fairly standard per the other Wilesco live steam engines; open the jet oiler, fill with steam oil, (I use about 4 drops for a 20 minute run-time), then oil with standard car-engine oil all around the drive train and moving parts (it’s worth noting that I do not use mineral oil on the plastic gears, but instead a light application of silicon oil).

The fuel/fire aspect of the model is supplied by Esbit fuel tablets and these are fairly standard across the board for Wilesco models.

The act of raising steam doesn’t take a very long time, but it helps to fill the boiler with warm water beforehand, and this also saves on fuel tablets. As steam builds, one can watch the handy steam pressure gauge on the front of the boiler; it’s calibrated in ‘Bar’ measurement and is red-lined at 1.5 bar (about 22 PSI) – a far cry from the 60 PSI beast that is the Maxitrak Allchin! All the same, once the gauge registers about 0.5 bar, the engine can start to be run, but don’t expect to carry any type of load or pull trailers until there’s at least 1 bar on the gauge, from my experience so far. That leads to one other minor gripe I have with this model, and that is that it cannot be run in ‘neutral’ gear – one must raise the left rear wheel slightly in order to run it stationary. No biggie, but nonetheless a slight annoyance; a suitably-fashioned stand sorts that issue out.

Once up to pressure and ready-to-roll, open the steam regulator slightly and flick the longitudinally-mounted flywheel clock-wise (when viewed from the rear of the cab) and after a few seconds of initial condensate clearing-out, she splutters into life!!!

The radio-control functionality when the Lorry is underway also proved to be a non-issue, as all my earlier frustrations faded-away – left and right turns were issued without any problems even from several metres away. I was running the Lorry on a concrete driveway with several of the usual concrete gaps and the Lorry traversed these with no issue. At one stage though, I did find the single driving wheel lose traction as the Lorry traversed a slightly uneven portion of the driveway!!! The driving wheel spun aimlessly whilst the Lorry had come to a halt! Because a lot of the weight is focused on the front wheels, it does pay to load the rear tray with some form of weight, and perhaps bias the weight towards the left hand side over the rear axle, as the frame flexes very little and with no suspension to speak of, it’s rather easy to lift the driving wheel, even with all the traction that its rubber tyre normally affords it.

The sounds and smells as the Lorry drives is somewhat typical to a Wilesco, but there’s a special connection I feel when I drive this Lorry; for one, with a loaded tray and the somewhat limited boiler capacity, it causes one to think ahead and ensure there is enough fire onboard to maintain the pressure – especially outdoors! That, and the fact that it has cracking good looks as it drives about also helps too!

From a utility point-of-view, the pulling-power from the Lorry once at full steam pressure is quite reasonable indeed and the well-thought-out gearing allows for powerful output and realistic scale speeds to be achieved, with certainly enough power to carry moderate loads and trailers; the challenge is however, in maintaining the head of steam…

Whilst some have noted that the boiler cannot provide sufficient steam for hauling the Lorry at a reasonable speed, in my initial run I have found that it does OK, but the Lorry certainly eats up the Esbit tablets! So much so that I am *very close* to naming this Lorry “The Gobbler”!  I went through about seven of the newer, larger Esbit fuel tablets during my initial run last night (the run lasted about 30-40 min and consisted of several ‘intermissions’ along the way to top-up the boiler and re-oil). So yes, definitely a model to run when your Esbit collection is rather large and well-stocked! This is especially so if running the Lorry outdoors, with any semblance of wind or breeze present. An aftermarket or add-on gas burner may be the way forward with this model, as others have also suggested, but all in all, the Esbits do not provide a terrible experience from what I’ve seen so far.

Two items I’d definitely recommend to those looking at purchasing this Lorry are 1) a stopwatch or other suitable timer and 2) a powerful handheld light source.

Both of the above items will help keep track of the water in the boiler, as it can be easy to lose track and not be certain as to the water level once it has dropped so its between the upper and lower sight glass port-holes. It’s also helpful to partly-fill the boiler and get to know the look of the portholes when they have (and don’t have!) water behind them. There is a slightly different look to the glasses in each scenario and I’ve also found that an intense handheld light allows one to see very fine water bubbles/particles behind the port hole glasses and this helps retain confidence that there is still water in the boiler!!

After a run, the cleanup involved is fairly straightforward. It’s worth noting however that there is a SEPARATE exhaust pipe for the steam; it does not get routed into the chimney as per some other Wilesco models, because the boiler actually has a central flue which is integral to the chimney, which helps in raising steam (and dropping the steam exhaust/condensate into there would put-out or otherwise disrupt the fire in fairly short order).

It’s pretty cool to see the exhaust steam exit from the right hand side of the Lorry as you drive along. At one point during my run, noting that I needed to stoke the fire and being too lazy to remove the burner slide, I momentarily removed the spark arrestor atop the chimney (CAUTION: EXTREMELY HOT! WEAR STURDY GLOVES!!) and added chunks of Esbits straight down the chimney/boiler flue and into the burner tray and then quickly replaced the spark arrestor. To my initial horror, this resulted in a touch of flames appearing out of the chimney and maybe a spark or two! The spark arrestor on top of the chimney did a great job of keeping these outbursts under control though and the spectacle only lasted a short moment (unfortunately I have no photographic goodness/evidence of the event – you’ll have to take my word for it!) – not a recommended way of running I’m sure though – and make sure you have enough water in the boiler if you do this!!!


So in closing, a very attractive (and perhaps ambitious) model from Wilesco, with some reasonable power given its sheer size and weight, but not without some (mostly) minor annoyances.

Given a larger-capacity boiler, a proper sight glass, a larger burner surface and a more-powerful/robust RC system, this could have been an absolute winner, but even without these, it’s still a worthy item for any live steam engine collection, if a little pricey.

Notwithstanding everything else, it certainly looks very imposing on the shelf at the end of each day and I think that ownership of one of these Lorries certainly signifies that you’ve “made it”…in the world of Wilesco live steam engine ownership anyway. :D


Of course, I cannot close this post without a collection of photos! Enjoy!

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Wilesco Product Page (D320 Steam Lorry):

LEGO – Fluid Drive Bus #6683 – It’s Alive!

So after several months of painstaking development and experimentation, my first (and hopefully not last?) fluid drive LEGO vehicle is now complete! I wasn’t certain whether or not I’d achieve this feat, of building a successfully, genuine, model of hydro-dynamic awesome-ness (if I may say so myself), but it seems I’ve done it and here it is!

For those interested in the ‘journey’ I’ve taken to get to this point, I’ve posted photos of the progress below, most of which you probably haven’t seen before. Unfortunately the earliest photo of the development I have, is from the 12 April 2014. It really is amazing how quickly things have moved, even though it has taken me about 6 months to complete this project. I can still remember the prototype chassis frame I ran through the house with a very early fluid coupling iteration. I wish I took photos back then! Oh well.

Of course, also included in this post are photos of the completed bus as it stands today.

‘In Progress’ Photo Gallery (Circa April-May 2014)

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‘Complete’ Photo Gallery!

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PDF Operator’s Manual:

Click here to access the PDF Operator’s Manual

Next steps

So where to from here? Aside from the mountain-load of plastic model kit boxes which currently await me in my hobby room, I think the ‘LEGO bug’ has well and truly bitten (for better or worse!). Sooo…I’m thinking that next on the agenda may well be another LEGO bus! Whether to utilise the wonders of fluid-drive or not for next time remains yet to be seen however.

One example of a bus I am eyeing-off at the moment is the famous Greyhound/GMC Scenicruiser. The very earliest (prototype?) version of this bus had TWO engines, driving through a fluid coupling to a 3-speed transmission with a 2-speed auxiliary transmission behind that, offering 6 speeds in total. Building this in LEGO would certainly be my next challenge…and if I chose to model the prototype, I’d be putting in two LEGO motors and probably TWO fluid couplings to ensure I extract the maximum power from those motors. Or, I could choose to model the later, more prevalent models of the Scenicruiser which had a standard clutch and transmission. Boring?? Haha. Time will tell…but I will be sure to keep you all posted here on this blog! I will close with a photo of a real-life Scenicruiser…


LEGO Pneumatic Tractor Mk1

So here it is finally!

Over a year ago, I managed to build myself a prototype pneumatic engine out of LEGO, after viewing some examples on the Internet. I was quite chuffed that my initial version worked so well, that I even posted a video about it. Then it seems, nothing happened for a while. Well really, it did, I just neglected to blog about it!! :( So, here it is, the main model which resulted from my dismantling the LEGO Unimog kit I had blogged about a while back.


So what exactly is a pneumatic engine you might ask? Well, a long time ago, Lego came up with the idea of incorporating pneumatic cylinders into their kits. These are basically cylindrical rams powered by low-level compressed air and were designed to operate kits with crane arms and other such creations. It seems however, that Lego builders around the world (me included) will always find ways to re-purpose these parts and thus, the pneumatic engine is born. Looking on the Internet, there are quite a few different types of these engines, some operating at crazy-high, Lego part-melting RPMs. Others (such as mine), operating at more ‘reasonable’ levels of speed, and boasting steam-engine-like levels of torque. In this post I’ll give a ‘teaser-like’ overview of the main points of the tractor, but I do hope that related documentation and assets, such as the video at the end of the post and also the images will be able to do some of the talking too.

Also, be sure to check out the detailed Operator’s Manual which I’ve written for this tractor!! (link at the bottom of this post also)

How the pneumatic engine works

I have, as aforementioned, already written a very in-depth operator’s manual regarding this tractor, and so here’s an excerpt from the manual, which I think describes the principles of the pneumatic engine best:

The engine operates because a flow of compressed air is directed to each of the two cylinders in a predetermined sequence. Once compressed air reaches the inside of the cylinder, it is directed to push against a piston, as it has nowhere else to go. Each piston in a cylinder is connected to the engine’s crankshaft, which is forced to revolve as the pistons move up and down. Finally, the crankshaft is connected to the Tractor’s transmission.
The engine can continue to run as compressed air flow to a given cylinder alternates as the piston in that cylinder moves up and down.

As the piston reaches the bottom of a cylinder, compressed air is routed to the bottom of the cylinder to push the piston upwards.
When the piston reaches the top of the cylinder, the compressed air is routed to the top of the cylinder, pushing the piston down, and the cycle repeats as long as compressed air is supplied.
This is referred to as the ‘double-acting’ or ‘double-action’ process.

The result is a continuous rotation of the engine crankshaft, which is directed to the transmission, which then feeds power to the rear wheels.

Other components and systems

I saw fit to load this tractor with as many systems and components as I could, being that I had quite a lot of parts left-over from the dismantling of the Unimog. So, here’s a short list of the systems and features of this tractor, in addition to the pneumatic engine (I’ll mention the engine again anyway ;)):

  • Two-cylinder double-acting, non-reversible, pneumatic engine – runs on air alone
  • Two-speed forward and one-speed reverse constant mesh gearbox
  • Automatic pneumatic parking brake featuring twin-brake shoe design
  • Drag link steering system
  • Rear differential
  • Rear pneumatic-operated ram (actuates various accessories)

The Operator’s Manual I’ve written describes these systems (and more) in much greater – almost exhaustive – detail. Be sure to check it out (link at the end of this post)!


Here’s some pictures of the tractor as well as a video and a link to the very detailed Operator’s Manual. Enjoy!!

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Link to the Operator’s Manual PDF

Where to now?

So what’s next at the Harman Motor Works? I am currently working on a remote-controlled Lego bus, to be based loosely off an AEC Regal MkIV single-decker. This Lego bus is fitted with my latest prototypical fluid drive coupling, of which I’ve also recently blogged about. I’m currently at a reasonably-advanced level of completion of this vehicle, having got the rolling chassis and box frame mostly complete. There is however still quite of bit of work to go. I will post an update or two on this blog over the coming weeks!

Here’s a sneak-peak at what the Harman Motor Works work-bench looks like at the moment:


Büssing 8000 S13 Massive Update! Project Complete?

It’s been too long, several months too-long in fact, since my last update on my Revell Büssing 8000 build. I’m glad to report however that the truck is 99.9% complete!! Why 99.9%? Well, in a way I could never really ‘complete’ something such as this; there’s always something more to ‘weather’ or ‘touch-up’! But for all intents and purposes, I’m happy to say it’s complete for now.

In the end I decided to leave the top panel of the hood (bonnet), roof and tarpauline (as well as the stanchion frames) unglued for quick and easy removal for a better look at the truck. Unfortunately, the roof panel is warped slightly and you may notice panel gaps in some of the pictures; had I glued this down this minor imperfection would not have been evident, but I chose to keep the roof ‘loose’ in order to better show off the interior as desired.

The final process in the build involved generous use of ‘MIG Productions’ weathering powder and I tried not to go overboard. I am quite happy with the final result though.

Pictures Tell a Thousand…

I’m happy to chalk this project up as ‘done’ for now and will let the utter boat (truck?)-load of images do the talking again for this post. Good thing too, as I have a pile of other projects waiting for that precious little space on my workbench. I will keep you posted as to what’s coming up the pipeline soon ;).

For now though, enjoy several month’s worth of progress on the Büssing (from January) up to present-day ‘completion’! (note: it was a difficult decision to choose which pictures made ‘the cut’ below as I had so many of them; I tried to capture a good variety of shots to tell the story). Also included below the images is a link to a quick video on my YouTube channel, HarmanMotor.


Christmas Comes Early – Unimog Style

This latest news comes courtesy of my “enabling wife” (her words not mine). An overly-large parcel arriving in the mail, and uneasy looks from her eyes when pressed as to the contents, I guess I should have known something was up…but no, I was caught completely off-guard by this; and what a pleasant surprise it was too.

Do you have anything smaller?

This has got to be, by far, the largest Technic kit that LEGO has ever produced. I don’t pretend to possess detailed information on every single kit ever made, and I’m not normally one to go for the biggest and baddest kits either, but this one is simply massive and comes in at over 2,000 pieces!

Not only is it big, it’s also licensed by one of the world’s most respected automobile manufacturers…Mercedes Benz.

Ladies and Gentlemen, I give to you…the Mercedes Benz U400 Unimog….

Devil in the details

Of course being the type of blog that this…blog…is, I couldn’t go without detailing some of the cool features that this kit promises to offer. As I type this, the massive box sits beside me, beckoning me, and luring me in. Deep within the box are the makings of some pretty cool systems just waiting to be built; things like pneumatics, raised hubs, electrics, tilting cabs, steering, cranes, winches, 4×4, and much more.

As I alluded to above, this kit comes with pneumatics. This will be the first time I’ve ever built with such systems and I cannot wait to get started. The pneumatics will power a fully articulated crane system which will sit on the rear of the vehicle, and there also seems to be an electric motor which can “charge” the pneumatics with the aid of a piston air-pump. What is missing is LEGO’s air tank system which is on my list of things to add to this vehicle as part of my grand (re)engineering plans (more on that below).

The vehicle also comes with a 4×4 system which features Mercedes Benz’ patented (I think?) ‘raised hubs’ design, referred to here as the “gear block”. This is basically a vertical gear-set which sits just inboard of each wheel and serves to greatly increase overall vehicle ground clearance while still providing drive. I’d known about this system in real life since forever (I remember looking at the real thing on the Unimogs at car shows in the past). Very neat.

A little more about the 4×4 system though: it appears that LEGO has again done what they seem to be doing a lot with their Technic kits…the drivetrain is not powered in any way shape or form by a motor or otherwise. There is, what appears to be, a fully-fledged full-time 4×4 system under there, with no less than three differentials, but not a driving motor in sight. This is definitely where I think I will come in…

There are just too many little awesome little features in this kit for me to mention here, and it’s getting harder to continue typing this with the box so close to me, so I will have to wrap this post up (pun not intended) shortly, but not before giving you a taste of what you can expect from me once I finish this vehicle in its “stock” form…

(Re)engineered madness

As awesome as this vehicle will be once built, I can see (already) that there will be heaps of room for improvement (and also to see how many additional systems and features I can cram onto this platform). I haven’t even started building this kit yet and already here’s my list of ‘to-dos’ or even, my ‘wish-list’ for this vehicle – some of the things may not be possible but that doesn’t mean I won’t try ;)

  • Add additional motor to drive…the drivetrain (believe it or not, this vehicle does not move under its own steam out-of-the-box). A fully-fledged 4×4 system is just waiting to be driven with this kit. I may also look at incorporating high/low range gearing controlled pneumatically if at all possible…
  • Customised pneumatics system (add an air tank for increased pneumatic capacity and add a manual pneumatic charging system option in addition to motorised compressor)
  • Possible remote control system utilising LEGO’s IR remote systems
  • Tilting flat bed using pneumatics
  • Steering using pneumatic assist (“power steering”)

Many of these things might have been nigh on impossible if this kit was any smaller (and who knows, may still be impossible), but the sheer size of the vehicle makes it an excellent platform to start trialling out these extra systems and it will really make it easy(ier) to let the imagination run wild and see just what can be achieved.

I guess it’s a good idea to mention that now this kit has arrived, my doomed Technic half-track project has stalled even further! Before I close, I will leave you with a pile of pics of what this kit looks like at this moment (see if you can “Where’s Wally” the little LEGO man in the pics below…just to give you a sense of the scale of this kit…).

The next few weeks are bound to be quite interesting…

Merry Christmas all! (hehe)

Blood, Sweat and Gears (Mk2!)


Here’s the follow-up post to my LEGO Technic Custom Flat-bed Truck, Mk1 of which I blogged about a few days earlier.

What you’ll see here is the latest and greatest iteration of this truck of mine – and probably the last one at that – alas, I’m looking for bigger fish to fry. More on that later though, let’s start by getting down and dirty with all the changes and upgrades which have happened to this vehicle since Mk1 back in 2009…

Point me in the right direction

One of the things I could have done better with the design of the Mk1 was that of the steering system; the steering gear ratio didn’t deliver as much steering torque as I would have liked. I solved this by adding an additional gear-set to which increased the gear reduction by another 3:1. This means more turns of the steering wheel is required to get the same amount of steering action, but with it comes a welcome increase in steering force and realism.

I’ll let the following video do the rest of the talking…

Chain me up (again)

Another new feature with Mk2 is the addition of a “chain brake”. This is basically a form of “handbrake” which serves to hold the vehicle stationary and stop it rolling away, or off a table onto the floor for example. :o

Normally the gearbox serves as a sufficient braking mechanism when either 1st or 2nd gear is selected and the motor stopped, however if the gearbox should slip into neutral, the vehicle has the tendency to let gravity take over…

The chain brake operates by sliding a “friction gear” into mesh with the gearbox final drive gear. The friction gear is keyed to a stationary shaft which cannot rotate, meaning that once in mesh with the gearbox, it resists movement of the drivetrain and thus, the rear wheels. The only disadvantage of this system is that if one rear wheel (or both, somehow) are off the ground, the vehicle can still roll even with the chain brake engaged due to the action of the rear differential.

The picture below highlights the location of the chain brake and its associated linkage system and lever (red). Keen observers may also notice the chain tension gear I’ve added to the rear chain which helps avoid the chain jumping links and slipping over the rear differential crown gear under load:

Chain brake

Trippin’ on LSD

That somewhat controversial heading is somewhat (fully?) matched by the sheer innovative genius that could only describe the limited slip differential (LSD) that has made its appearance with Mk2. /brag

A bit of background…

The design of this LSD is purely my own and took a bit of experimentation and tweaking to get right, but I must say, it works quite swimmingly in its current form. For those who aren’t quite familiar with what an LSD is in “vehicle-speak” (you’re still reading this?? just kidding!), it’s a differential system which attempts to overcome a traditional differential’s one major short-coming: the tendency to transfer ALL torque to the driving wheel with the LEAST amount of traction.

Let’s step back one step further: the purpose of a differential is to allow one wheel on a common axle to turn faster than the wheel on the opposite side during a corner. This ensures effective steering action and reduced tyre wear. I won’t go too far into this, as there are a lot of articles and info on this on the Internet already (see the end of this post).

“Most” cars and vehicles are fitted with what’s known as an “open” or “standard” differential. This works fine around corners and during general operation on stable, high-grip surfaces where both wheels on the axle have equal amounts of grip. However, if one should venture into a loose surface, and one of the wheels connected to the differential should slip, or become raised off the ground by a bump, etc, all torque is immediately transferred to that wheel. Meanwhile, the wheel on the ground on the other side of the axle (in most cases with all the traction) sits motionless – when it could be driving and moving the vehicle.

An LSD works by re-routing the torque that normally takes the “path of least resistance” and transferring it to the wheel which actually has traction, i.e, the “loaded wheel”. Thus how the system earned its titled “limited slip”. A good measure of how well an LSD works, is to raise one driving wheel off the ground, and seeing how much torque gets transferred to the “loaded” wheel on the other side (an “open” differential in such a situation would spin the lifted wheel uselessly and move the vehicle nowhere). You’ll see me perform this test in my LSD test video below shortly.

How it works!

So we finally get to the nitty-gritty; just how the LSD system on the Mk2 functions. Originally, I was going to trial a geared version but belts and bands have always intrigued me for their smoothness in operation and the fact that they are generally more forgiving under load and perhaps even more variable in setting than straight-up gears.

So…I went with a “dual-band” setup for the Mk2’s LSD system. I’ll do what I always do and attempt to explain in text, follow with a vague pic, and finally show you a video. :)

On each half-shaft of the differential, I’ve mounted a large pulley. Now these two pulleys on their own don’t achieve anything special, but to these pulleys I’ve added a “band” each, which then connects to a “common shaft”. This common shaft is mounted upon an adjustable mechanism which moves the shaft back and forth (adjustable by the user using the “torque wheel”) so that it’s either closer-to or further-from the pulleys and thus band tension can be almost infinitely adjusted.

Here’s that pic:

LSD close-up

Increasing band tension has the effect of making the common shaft “connect” both of the large pulleys (and the two halves of the differential) together as a single unit. What this ultimately achieves is making the differential unit behave less like an “open” differential and more like a solid axle. This naturally means that when the LSD is set to its maximum torque transfer setting (maximum band tension), differential action (allowing one wheel to turn faster than the other around corners for example) is limited, but this is where the magic of using bands rather than solid gears comes into play: no matter how tight the band setting, there is always a little bit of “give” in the system.

Time for a video…

Some additional notes…

Band wear

As mentioned earlier, the use of bands rather than “solid” meshing gears gives this system its own  type of “elegance”.

With this so-called elegance however comes one disadvantage over the use of traditional gears: band wear. It must be said however that under “normal” operation on solid ground and with minimum tension, the bands experience almost no wear as the pulleys go about spinning by their own free will. It’s only when the bands are tightened and the differential subjected to prolonged slip condition (where one wheel turns faster than the other), band wear starts becoming evident as they try to rotate the common shaft and transfer torque (band wear is generally visible in the form of bits of rubber residue along the bands). Having said all that, I’ve gotten several hours worth of LSD operation out of the bands currently fitted to the truck, and they haven’t let go…yet!

Slip ratio

Now slip ratios are not an easy thing to determine with a band-drive LSD system as there are many factors and variables which could affect it, such as band wear, band tension and perhaps ground surface type.

From my observations so far though, I’ve noticed that under full band tension, the LSD unit comes reasonably close to achieving a 1:1 slip ratio…meaning that the loaded wheel in a slip condition almost turns as fast as the wheel up in the air (doing nothing). Obviously getting as close to 1:1 as possible (or even over-driving) is desirable, but with a band system, it’s not as easy to achieve this (as compared to a geared setup). I’d hazard a guess and say that under band tension, this LSD transfers around 50% to 75% of the torque to the loaded wheel, which is not a bad effort indeed and as you can see in the video above, seems to work quite well in practice.


One of the other major advantages I’ve seen with this LSD system is the fact that the system is very compact and hardly takes up any more space than the standard differential unit. The large pulleys mounted on the differential half-shafts hardly protrude from the vehicle and the common shaft is tucked neatly up into the chassis of the vehicle too.

Me likey.


Differential article (Wikipedia)

Other stuff in Mk2

Some of the other additional features I’ve added to Mk2 that I thought worth mentioning (but not exactly worth their own heading) are as follows:

  • Rear flat-bed-mounted hoist (adjustable for tilt via linear “hydraulic” system)
  • Headlights! (yes, that actually work)
  • Various miscellaneous chassis strengthening tweaks


Here’s a bit of an image gallery showcasing the Mk2…

Mk2 Showcase
Chain brake
Underside 1
Underside 2
LSD adjustment wheel ("torque wheel")

Final thoughts…

I’m quite happy with the way Mk2 turned-out in the end. It’s certainly come a long way since I laid out the bare chassis rails on my building bench and started dreaming for the first time. I would have loved to add an RC system to this truck and maybe even a PTO (Power Take-Off) unit to the rear-end, but alas, some things just weren’t meant to be it seems.

Where to now? Onwards and upwards onto bigger and better things! My next model could be a U.S. Army Half-track, or a robot. Who knows?

LEGO! “Technic” To Be Exact


This is the first post in my blog where I talk about the custom LEGO Technic  Custom Flatbed Truck that I’ve had since about May 2009 when I started to get back into building LEGO Technic models. This model truck (purely my own design if I may say so) has gone through quite a few iterations since May ’09 and I’m still working on putting the finishing touches to the latest version as I type this.

Let’s take a step back though; this first post will introduce you to the development (from scratch) of the prototype truck and the subsequent (initial) MkI “release” (I’ll leave the latest-and-greatest version for a future post).

Prototype me!


When starting any new LEGO Technic vehicle project, I tend to start off by getting the basics down-pat first: the chassis frame “rails”. The chassis will form almost the back-bone of the vehicle and will function as the main component which everything else bolts onto (much like real-world trucks). I normally go through a few design “phases” before I settle upon the length and width of the chassis unit. It can be difficult to envision just how long and high I want the vehicle to be, so I try to get the chassis as close to “perfect” as I can before I move on (because changes to the chassis rails can become very hard once everything else is attached to it!).

Rolling gear

Once the chassis is sorted, I start thinking about the next most important thing: the wheels! Obviously the wheels and their mounting system will form an integral part of the chassis unit and are obviously an essential part of the truck. Considerations such as wheel-base, wheel-track, steering and ground clearance start coming to the forefront of my thoughts.

Once I’ve got all these considerations sorted and perhaps after experimenting for a little while, I’ll normally end up with what you see below – a rolling chassis!

Not much to look at...yet

Wait a sec!!??

Ok so I cheated a bit here. What you see above is actually (believe it or not) the truck at a slightly more “advanced” stage of completion. You may (or may not) notice a longitudinally-mounted electric motor connected to a 2-speed gearbox, so let me fill you in those components now.

Electric motor

The electric motor I settled-on for this project was one of LEGO’s own: the “M-motor”. One thing I’ve noticed with most of LEGO’s motors, is that they mostly come with their own integrated gear-reduction. This is helpful as it means I don’t need to worry about tweaking the overall gear ratios too much before the power hits the ground. For this truck however, I still opted to build a gearbox of my own design…

Box of gears anyone?

For this project, I decided to custom-make my own LEGO gearbox from scratch. The gearbox offers 2-speeds: LOW and HIGH, plus a “neutral” range (which obviously transmits no power to the wheels).

The actual design of this ‘box is one which I’ve used for ages in my LEGO models now…it utilises an “input” shaft which connects to the electric motor, and from there, transmits power down to a “layshaft”. Finally, the power reaches the rear-end of the gearbox where I generally mount a drive shaft to the rear wheels, or in this case, a “final drive” unit which will run a chain/sprocket drive on the rear axle. If I’ve lost you several lines back, here’s a pic:

Gearbox explained...maybe

Selection of gear ratios is obtained by sliding the lower half of the gearbox (the layshaft)  back and forth so that it engages LOW, neutral, or HIGH. It’s a relatively simple design but one that works admirably. As any gear head will tell you though, only one gear ratio must be able to be selected at a time, otherwise (as expected) the gearbox cannot rotate and will lock-up, so I ensured that the gears were aligned sufficiently to avoid any issues.

Here’s a YouTube video of the gearbox in action…you’ll also get to see the rolling chassis in this video (incidentally, the proposed “RC” [radio-control] feature never materialised – at least not yet anyway):

Gear ratio-wise, LOW gear offers 3:1 reduction, while HIGH gear doesn’t change the ratio at all, offering a true 1:1 ratio (direct) drive straight through the gearbox. That’s not the end of the gear reduction though; at the rear end of the gearbox, the final drive reduces the ratio (no matter what gear is selected) by 3:1 again. In other words, the trucks enjoys some fairly serious gear reduction with LOW gear engaged, to the point where the motor can easily break the rear rubber tyres loose on slippery surfaces.

Chain me up

Eventually, I hooked up a chain drive from the rear-end of the gearbox down to the rear axle of the truck (which incidentally added another 1.5:1 worth of gear reduction!). The rear axle features a fully-functioning differential unit with three spider gears. I won’t bore you too much with the details, but some of the pics you’ll find at the end of this post should hopefully tide you tech-heads over.


OK, so I’m speeding things along a little bit here (mostly for the sake of readability)…to talk about the other major component and consideration for the vehicle. The frame! Otherwise known as the body or cabin or “cab”.

Here’s one of the earliest iterations of the framework which I came up with for the truck (note the battery box mounted immediately behind the cab, which takes 6x AA batteries):

First version of frame/cab

But alas the angles in the front pillars drove me crazy from a geometrical perspective (they could never seem to line-up 100%), so I scrapped that design and went for something a little more rigid (and at more sane right-angles!):

Final frame - awaiting gearbox

Once the frame was mostly settled-on, I could focus on getting the interior sorted and other somewhat minor details such as hooking up a gear lever and linkage so that the gears could be selected from the cab (as you’ll see in videos further down this post). But there was still one of vital component remaining…a steering system!!


Steering systems are always a challenge to build. On the one hand you have two giant front tyres which need room to be turned about their steering axis (this is where you need to make sure your chassis rails are narrow enough at the front end to allow this!), and on the other hand, you need to devise a way with which you’ll get the motion of the steering wheel inside the cab all the way down to the front axle to do the actual turning of the wheels (read: a pile of linkages!). On top of this, all these linkages must clear the rest of the vehicle, the motor, etc and everything else as they move back and forth, to and fro, to steer the wheels.

The system I ended-up using for the truck could perhaps be considered a type of “drag link” and you can see a bit of how it works in the YouTube video at the end of this post. The steering system you see in action here, while satisfactory, didn’t make me as happy as I could be – the steering gear ratio was too high – so after MkI, I lowered the ratio significantly. I’ll fill you in on this in future posts.

Mk1 ready!

So I eventually got the truck built to a level of my satisfaction and thought I was done. Hah! Unfortunately (or fortunately), in LEGO land, things are never finished…there’s always something more to be added, adjusted, broken-down and re-made or just plain changed. I will save all that subsequent development for future posts though, and instead leave you with pictures of how MkI turned-out. Enjoy!

Rear 3/4 view
Heli view
Front 3/4 view
Belly of the beast
Chain drive to rear differential
Looking down into cab...
Rear end

Mk1 videos

Average Joe’s Guide to “hypermiling”

All this talk of “hypermiling” – you may or may not have heard about it already. With the cost of fuel increasing it’s perhaps no surprise that there is a huge community of drivers out there who are challenging themselves to achieve the best possible fuel economy from their vehicles on a daily basis.

I’ve only recently become aware of this “phenomenon” and I must confess that already I’ve become a little bit addicted to it – it’s almost like a game where you repeatedly try to hit a higher score. This is quite a confession coming from me, as only 2 or 3 years back, I was a serial speeder or “hoon”, trying to get from A to B as fast as possible, and getting myself worked-up and stressed out over people who seemingly couldn’t get out of my way fast enough.

So…just what is this “hypermiling” business all about?

Basically, you take a car – any car (preferably your car mmkay) – and you set about driving in the most efficient manner possible. Note: this does NOT mean you drive as slowly as possible, making every other poor driver who’s stuck behind you furious and ending up late for every appointment.

Rather, hypermiling is all about getting the most out of your tank of fuel. There’s heaps of hypermiling guides out there (some of them pretty extreme) on attaining the absolute pinnacle of fuel efficiency from your vehicle, but that’s not what this post is about.

This post is intended to introduce you (and I’m not calling you an Average Joe btw – not directly anyway hehe) to hypermiling and open your eyes to just what it can do for you and outline some simple things you can try next time you’re out on the road to start you on your own way to “hypermiling”.

So let’s get started…

1. Get your car serviced

It should be no surprise that a well-maintained vehicle uses less fuel. The main thing is to ensure that your engine’s oil and filter is changed in accordance with the manufacturer’s recommendations – generally every 6 months or 7,500km if you drive regularly and drive in traffic (who doesn’t these days). Apart from this though, ensuring your vehicle is serviced and tuned regularly will go a long way to helping you save cash both in the long term (by avoiding costly repairs later on down the track) and the short term (by saving you money in fuel).

2. Check your tyre pressures

Yes this might seem obvious, but when was the last time you checked your tyre pressures? Low tyre pressures have the effect of increasing drag and friction on the vehicle and can also adversely affect your road handling. Properly inflated tyres help your vehicle move along the road as efficiently as possible. I’m not sure if you’ve ever tried to pedal a push-bike with flat or under-inflated tyres…believe me, it’s no fun. The laws of physics for cars is no different.

Check the tyre placard inside your glovebox or on the driver’s side door jamb which shows you the manufacturer’s recommended tyre pressures depending on your vehicle and its load. If you have aftermarket tyres and wheels of a differing size than the manufacturer’s standard, this placard may not be of much use to you, but generally speaking, the lower the profile (skinnier the sidewall) of your tyres, the higher the tyre pressure you should run.

3. Lose some weight

Every single object inside your car requires energy to move it along as you drive. Things like unnecessary boxes loaded with miscellaneous paraphernalia and any other junk which you might be carrying around in the car with you – it’s safe to say if you won’t need it at your destination today, then leave it at home. The lighter your car is, the less energy it will take to move it along. Some might argue that most items you remove will make such an insignificant difference it’s almost not worth it, but I believe that every little bit counts and it’s the mindset that matters.

Plus if you regularly cart around your favourite 5 bowling balls in the boot of your car, they definitely can’t be doing you any favours in the fuel efficiency department…

Note: I’m not asking you to be paranoid here and start removing everything from your car (you can leave the back seat and the spare tyre in the car – you might need them one day) – and I’m not asking you to flatly refuse taking your slightly obese Aunt Betty along to her doctor’s appointment once every few years either.

4. Leave early – relax!

A lot of people these days jump behind the wheel of their car and start racing towards their destination. Sure, we all have our days when we’re running late and simply must GO, but speaking in an overall sense, if you finding you’re having to do this more often than not, it will actually contribute to you using more fuel, wearing your car out faster, AND, perhaps most importantly, stressing you out more as well.

By leaving the house a few minutes earlier than normal, and driving at a comfortable pace (read: not a snail’s pace), you will find you will eventually end up being a calmer person behind the wheel and you may even save yourself some money at the fuel bowser too.

5. Accelerate gently

Moving a car from a dead stop takes the most amount of fuel of all and this is arguably the most fuel inefficient time as you drive (see point 6 below on ways to avoid this). Once you get up to speed and start “cruising”, you’ll find that your fuel consumption drops off quite significantly (provided you’re not “cruising” at 120mph). This is the main reason that cars generally use more fuel “around town” – because driving in busy areas generally requires more stopping and starting (and thus more fuel) than say, cruising comfortably down a quiet country highway at a constant pace.

So, with that in mind, the goal is to accelerate from a stop gently, and reach the speed limit (yes that means staying within the speed limit – see point 7 below) in a timely manner – not too slow, but not too fast either – and to try and maintain that speed for as long as possible.

If you have a manual transmission or an automatic transmission which allows you sequentially select gears (+ and -), aim to shift as early as possible as you accelerate (but not so early as to labour the engine). Holding gears excessively and building up engine RPM as you accelerate will only hurt your fuel economy. You will get to know when your own vehicle’s “sweet spot” is to shift up. In my Tucson, the transmission will shift up into top  gear at a measly 57km/h and the torque converter lock will kick-in straight away provided the throttle application is light or moderate allowing the revs to drop right down.

6. Build a “buffer”

As you drive, particularly in urban and built-up areas such as cities and towns, you’ll generally encounter many sets of traffic lights. As we’ve learnt above, starting from a stop is the most fuel inefficient time as you drive a car. This is because it takes much more energy to move a stationary object from a standstill than it does to simply maintain speed or slightly increase your speed.

With that in mind, aim to “time” your red lights, i.e., lights ahead just gone red? Start slowing down earlier (again, be mindful of drivers around you – don’t be a snail) and you may find that by building up a so-called “buffer zone” between you and the red light, the lights will more likely go green again before you reach them, allowing you to coast through them perhaps even without ever touching the brakes. This is obviously much more fuel efficient than speeding right up to the red light, stopping the car, then starting it back up again.

7. Stick to the speed limit!

This is probably the most annoying point of all to a lot of people, but believe me, speed limits are there for a reason. Driving at elevated speeds only causes more wear on your car, more stress on you and of course, increased fuel consumption.

By driving the speed limit, you’ll be able to react to events around you earlier and with greater efficiency, not to mention you’ll definitely use less fuel cruising at the limit (or dare I say it – just below it…).

8. To sum it up…

There’s loads of other little things you can try to get better fuel economy from your car, but the above is what I consider to be the key points for starters. I may no doubt delve deeper into this “phenomenon” in future posts, but I figure this is enough bed time reading for the time-being.

You’ve probably realised by now that hypermiling is all about “energy preservation”; by driving in a consistent manner, changing your speed as little as possible, and if you need to make changes in your speed (stopping or starting) aiming to make those changes as moderately as possible. Hypermiling is not about driving slowly, but about driving as efficiently as possible, as much as possible.

Until next time, happy hypermiling!