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:


Happy New Year! And a revival…of sorts…

Happy New Year  2014 all!

As usual, it’s been way too long since I’ve updated this blog. Many things happened in 2013, both blog-worthy and not (unfortunately), so I’ve got a bit of catching-up to do I fear.

One of my new year’s resolutions is to make sure I update this blog more often!

So, I thought I’d start this post with a bit of a rundown of the content you can expect to see on the blog this year:

1. More model kits! Yes, I have been building more model kits since the last update where I showed-off the Bussing 8000. Since the Bussing was completed six months ago, I have obtained no less than six kits which have promptly filled my study/hobby area, and I have so far completed two of those kits. Yes, the Harman Motor Works has its work cut out for it model kit-wise this year…and I intend to blog them all to within an inch of their plastic!

2. More Lego! Since having dismantled the Unimog kit, I have built (and completed) a brand new vehicle of my own design: a two cylinder pneumatic-engined tractor, using an engine I created as seen here in a video from over a year ago. Stay tuned for more info on that! (btw, I have also been dabbling in Lego robotics as of late, so you may come across a post or two detailing some of my creations on that front…I make no apologies for the any mind-bending robotic behaviour you may witness…)

3. More sim stuff! OK I will admit I have been a bit lax in updating this blog to align with my YouTube channel which has been updated a fair bit more frequently, mostly with simulation-related content. I will endeavour to have some posts up on this blog that will hopefully support those videos.

Again, thanks to all that are reading this (and have found this blog useful), I hope this year proves a successful one and here’s to more content!

P.S. Stay tuned: in keeping with the spirit of updating this blog regularly, I will very shortly have a new post up following this, that will showcase the latest model kit which I have just completed. What ever could it be?? More on that shortly!


Lego Unimog U400 Kit – Modified by Harman Motor Works

This post has been a while coming, but I thought it was high-time I did post it, as the Unimog might not be around for much longer! :o

You may be aware from one of my previous blog posts, that I received the Lego Unimog kit as a gift a while back. At the time, I mentioned that I would kit-out the model with my own custom modifications in order to get more out of it and ‘make it mine’. Well, fast forward several months, and that has been achieved. Keep reading to see the details on just what it is I did to the truck…

Mod #1: Power to the people

One of the first things that I wanted to do with this model was make it powered. I figure that it came with a very capable all-wheel-drive system out of the box, so why not make proper use of it? So, I promptly ditched the fake piston engine provided by Lego in lieu of an M-motor, coupled to a hi/low range gearbox, to drive all four wheels. The result was certainly worthy of the effort.

Mod #2: High/low range gearbox

As I briefly mentioned above, I also added in a compact two-speed gearbox just behind the motor, to enable speed and torque to be adjusted to the conditions. In low-range, this thing really develops some decent torque given that it’s one heavy truck powered by only an M-motor. In high-range, the vehicle picks up some good speed as well. The gearbox ranges can be controlled via a lever which protrudes up into the cab beside the driver’s seat.

Mod #3: Air suspension (rear) & air tank

The next thing I did was add in an air tank to the truck’s chassis. I managed to neatly tuck it in within the chassis frame…it just turns out that there was a perfectly-designed ‘nook’ just waiting for the tank to make its new home. Cool! The air tank not only extends the capacity of the pneumatic circuit, it also means the electric motor which drives the air compressor (on-board) doesn’t have to run constantly when operating the air-driven devices.

Another thing I did while I was at it, was to replace the main drive gear from the compressor motor, with a gear which has a safety clutch it its hub; this basically means the clutch will kick-in when the air pressure in the pneumatic system reaches its upper limits, and prevent the motor and the related pneumatic components from strain and damage.

With the air tank fitted, I decided to ditch the rear springs and replace them with two pneumatic cylinders, which act as adjustable height air springs. The great thing about these things is that the ride height can be adjusted to suit no matter what type of load is carried on the rear of the truck, so no more spring-sag when carrying heavy items. The rear air springs are controlled via a pneumatic switch in the cab.

Mod #4: Auxiliary manual air pump

My efforts to cram as much as I could onto this model resulted in this next mod: a manual hand pump/crank system to drive the onboard air compressor when battery power was unavailable. I figured that now I have the rear air springs, it would be handy to be able to pump them up whenever I chose even if there was no electric power available. The system works well, and the manual pump handle is stowed away in a specially-made storage compartment by yours truly.

Mod #5: Lower-ratio raised hubs

This was actually one of the earlier mods I did the vehicle, and not major by any means, but necessary all the same, if I was to effectively motorise the truck. This mod involved removing the 1:1 gear ratio at each raised-hub, and replacing it with a set of gears offering 3:1 gear reduction. The result was perfect to give that M-motor the extra torque it needs to power such a large and heavy model. Combined with the low-range gearing, this truck seems to easily tackle most obstacles.


So that’s basically it for now. Unfortunately I may have to dismantle this model soon; I have a hankering to use its many parts on some new models of entirely my own design, and it pains me to see that I have several hundred Lego parts sitting on the shelf locked-up in this kit, that I could otherwise be using for my own creations. I do seem to enjoy building my own models from scratch moreso than building Lego kits to the letter. With that said however, I did thoroughly enjoy custom-modifying this kit, and even stock out-of-the-box, it certainly was an impressive kit to build. It’s just a shame that I did not get to add remote-control capability to this kit. Maybe next time.

I’ve included some pics below and also a link to a video of the truck on my YouTube channel, Harmanmotor.


What I’ve Been Up To Lately

It’s been a while between drinks, this is true.

So what’s been keeping me busy lately? Well, everything from driving double decker buses, to flying a Spitfire Mk1a it would seem…

Did you just say…bus?

OK, so this ‘part’ post will predominately focus on the ‘bus’ bit of what I’ve been doing. I will cover the Spitfire and other planes I’ve recently had the pleasure of flying in sim land soon, however. I promise!

Anyway, back to the buses…since discovering ‘OMSI – The Omni Bus Simulator’, I have become quite addicted. This is definitely not your ordinary run of the mill ‘game’, no sir. OMSI brings with it unparallelled realism, physics-wise, audio-wise, and hey, the visuals aren’t that bad either. I don’t think you will find another bus simulator this detailed out there right now.

I have several YouTube videos already uploaded to the Harman Motor Works Blog channel that serve to do this sim more justice than just a few paragraphs of text, and I will link to a few of those videos at the end of this post. In the meantime however, here’s a quick rundown of just what to look forward to with OMSI…

Buses? You’re funny, man

Sure, you might think I’m a bit ‘daft’ for driving these things, but I’ve had a secret fondness for buses for a long time and since I was young, I remember riding the various double-decker dinosaurs during school excursions and the like. There is something quite special in driving something so large, with so many people aboard, on ordinary streets, without incident (hopefully). OMSI gives me a chance to (almost) live out that desire to drive these behemoths. All that is missing is the smell of diesel…hmm…

Next stop…Melrose…I think…

One of the great things about OMSI is that you actually have the chance to pickup, drop off and generally transport passengers about in a virtual environment, with variable environments, traffic levels and with a variety of buses. What’s more…you are also given the chance to sell tickets to passengers as they board. I joked early on that this sim could almost be considered to be a fun ‘maths game’ with the amount of ticket sales you are sometimes called on to perform. Not only do you need to select the correct ticket to offer the passengers, but you are frequently called on to deal with calculating and giving back the correct change; some passengers will complain if you get it wrong, others, if you have accidentally given too much change, will gladly accept the ‘tip’. Bastids. :o

What’s under the hood?

As mentioned briefly above, OMSI is blessed with an ultra-realistic physics model. Your buses tyres will scrub kerbs, (climb them if you’re especially careless, lazy, green, or all of the above), exhibit realistic movement physics and each bus also has realistic systems modelling such as air brakes, transmissions, and engine power. Think you’ve mastered the art of driving an old-school MAN SD77? Try driving it at night during a snow storm. It’s whole different ball game.

The cockpits in these old buses are loaded with switches, all clickable in the sim, which offer everything from cab lighting, heating, to hydraulic drivetrain braking. Incidentally, it is quite funny to go picking up passengers during a night bus run, and having forgotten to turn on the interior lights, hear the passengers complain about the darkness.

Which brings me onto another point: passengers won’t say much if your driving well and getting things right (or at least right-ish), but mess something up, and boy will you hear about it! :D Climb a kerb, run late, drive during the freezing months without the interior heating running, and be prepared for the tirade of complaints which will surely eminate from the rear of the bus. Really foul up though (hit another car, stationary object, etc) and most passengers will complain even louder and signal to leave the bus immediately. Fun times.

I would go as far as suggesting that if you should decide to try this sim out (and you definitely should), to avoid picking up any passengers until you at least get the hang of driving these behemoths in the first place. You will quickly learn that there is a certain art to taking corners in tight quarters with cars and pedestrians surrounding you, and you will learn to judge distances down to the last inch as you squeeze past heavy traffic. If this sim has taught me one thing, it’s: ‘when you think you’re close, you can get closer…until you hit something’. Hah.

I should mention that the native language for the game is German and the included maps are somewhat based on real-world German locales, so voices are naturally all German as is the writing on the tickets (which makes selecting the correct ticket a challenge sometimes), street names, destinations, towns, and well, pretty much everything else. However the sim is easily moddable and there are English sound packs and the like out there, not to mention a flurry of add-on third party buses, of which the quality is varying. I have also personally created an English ticket mod which I may well release on the Harman Motor Works official website soon.

Tickets please…

In closing I would recommend this sim to anyone remotely interested in buses, simulations or driving in general. I am glad I found this sim, I stumbled across it back around February whilst perusing real-world buses for sale on eBay. Fancy that.

Having had a Logitech G27 in my possession for over 2 years now, I’m glad to have finally found a great use for it. Being that most buses in the sim are also automatic, I was especially glad to have recently downloaded an add-on bus that offered a manual transmission which fully utilised the G27’s gear shift gate and clutch. Double wow! It should go without saying that all the buses in OMSI support the G27’s excellent 900-degree steering wheel rotation which offers superb steering fidelity and realism.

Below I’ve included a brief gallery of screenshots as well as links to some of my YouTube videos as well as a direct link to the official OMSI homepage.

Enjoy, and get on that bus!!

YouTube video #1: OMSI Familiarisation – Quick Run Around Bad Kinzau

YouTube video #2: OMSI – Bad Kinzau to Saasdorf – Snow Day

YouTube video #3: OMSI – Bad Kinzau – Ikarus 260 – Driving Stick

Official OMSI website: