Monday, May 16, 2011

The influence of Power Functions

After the introduction of Power Functions in 2007, the amount of motorized models has seen an exponential growth. Since then not only has the Technic line introduced at least 2 sets with motor every year, but also it seems like Power Function models are the new standard among fan creations, gaining even more popularity due to the various Trial Truck competitions. It has become quite a phenomenon, showing LEGO Technic trucks clearing a challenging obstacle course, something that would have been unimaginable several years ago. Those trucks have evolved very fast, with high focus on efficiency, meaning that structures have to be as light and strong as possible, whereas power trains as short and compact as possible with end reduction. On a positive note those competitions have drawn a lot of people into Technic and teaches many of the elementary principles of kinematics. There are however a few other things to consider.

The trend of today is that things have to be cool, not necessarily realistic. LEGO Technic seems to follow this trend. When launched it became well known in Germany under the slogan 'Technik wie in wirklichkeit' (Translated roughly as Mechanics like in reality). Today, 2 of the pillars are Authenticity and Functionality, but that doesn't necessarily mean authentic functions.One example could be the linear actuator, which in many cases is used for functions that are in reality hydraulic. Pneumatics would have been a more suitable alternative considering authentic functions.

But probably a better example is comparing the Technic 'Supercars' that LEGO has introduced over the years. In the past it has been all about the interaction between drivetrain and engine through a gearbox. Of course there are limitations with the system, so things had to be simplified and put in perspective, but the focus was on authentic functions and their educational value. Looking at the latest 'Supercar' 8070, I can't help but imagine a child that is playing with the gearstick in a real car and wonders why the doors are not opening. Not very realistic, but it's 'cool' especially when those functions are motorized with Power Functions.Why wasn't Power Functions used for motorizing the drive and steering function instead, especially considering that in this case there was not the problem of a complex drivetrain like with previous 'Supercars'? That would have been much cooler, right, looking at the popularity of the Trial Truck models?

Courtesy of Paul Ian Kmiec (Sariel)

Could it be that motorizing large, wheel based LEGO vehicles with Power Functions is actually beyond what is reasonably possible with the system? Looking at what kind of driven remote controlled Power Functions models LEGO has launched so far it is striking to realise that all of those have been track based. Another interesting thing to notice is that 3 of the recent Technic flagships with Power Functions, 8275, 8258 and 8043 all seem to have had some issues which led to revised parts and/or building instructions. It seems like motorizing big complex LEGO models is really challenging what the system is able to handle and made for.

So apparently official LEGO designers are already pushing the boundaries of what is safe, but this is in no comparison of how far beyond the limitations of the building system certain fan created models, and in particular Trial Trucks, are. Either broken or grinding gears, twisted or bent axles, and stalled motors are just a few common indicators that show that the system is not capable of handling well the high forces and torque applied. To get high clearance big wheels are often used, but from a torque and stress point of view it only demands more from the system. Maybe that explains why we haven't seen any official LEGO set with big wheels and driven by Power Functions?

In conclusion with LEGO you can build anything, but the system certainly has its limitations. How far (beyond) the boundaries are pushed is up to the individual on what is acceptable. With my background I try to keep things within reason. Due to the popularity of Trial Trucks, and the coolness of Power Functions, however, many people have higher expectations of models, pushing the system beyond limitations, shifting the focus from authentic functions to effective and cool functions.


Alessandro said...

Very good post. It would be interesting to see the TLG designers coming up with a large wheeled vehicle motorized with Power Function system that is showing a reasonable level of reliability. A remotely controlled mototorized gearbox is something I really would like to see in an official set. The reason why we have only seen so far tracked vehicles with a PF remote control must be in the low reach of the remote system. Yet motorizing a Trial Truck - that is not moving that fast - there should be no issue with this topic.

uLLo said...

It is normal - in competition - to go beyond limits.
So with LEGO TrialTrucks.

In real life, Ferrari for example designs its engine totally different for Formula1 and for their custom cars.
So it happens, that the F1 engine blows up after few kilometers...

Lego itself HAS to design sets that are reliable - TruckTrial- Trucks only have to win...

"Any car which holds together for more than a race is
too heavy." - Colin Chapman

Felix Schiffler said...

Good post! I would like to see an instruction for the upcoming 8110 Unimog how to make it remote contolled drive and steer. I think this isn't so hard, seen the instructions and videos of (trial) trucks you can find on the internet. I myself have motorized the 8285 tow truck, it handles fine.

Anonymous said...

I am surprised there are no official Power Function cars or trucks with motorized wheels and steering. There were many during the 9v System but I think most of them were small or medium models, slow, and had a rubber belt between the motor and the drive train to reduce strain on the motor.

Rohan Beckett said...

The best, most reliable (and most fun) motorized lego vehicles, have been the RC Racers series.

I own two of them:
8376 Hot Flame
RC Race Buggy

and I've had them at mini exhibitions, where kids have played with them for *hours*, both indoors, and out, and they withstood everything (bar the odd wheel falling off!)

I think it's just the nature of lego parts - ease of assembly, and dissassembly vs reliability and strength - There are no regular technic gears, or steering parts in the RC cars - they are all custom.

Indeed - the main weak point in the models is the 3-pin connection from the steering hub to the wheels

I think there IS room in the Lego family for models like this... but I think Technic should be more about internal mechanics, rather than 'pure remote control'


kona_lm said...

good blog, i am a big lego fan and found this interesting to read.

connor@red kitchenaid mixer

Al said...

Excellent post. It echos many of my feelings. It is certainly possible for a large, flagship sized set with large wheels to be easily and reliably motorised with a gearbox and so on, just not so instinctively with the current parts. Looks at how a real gearbox produces it's different gear ratios. It very different and far better than the way lego gearboxes do it. This is just one of many areas that are crying out for improvement, along with the pneumatic system. Sure, the current transmission worked great and was a fantastic innovation when it was first introduced in the 8880 17 YEARS AGO!!! Now it's time for something new.

Al said...

So i'de just like to add to my above comment by saying that it is very possible for technic to be both cooler AND more realistic than ever before, the unimog is taking baby steps towards that goal I think.

Anonymous said...

Pardon my ignorance, but what were the problems with 8275 and 8258?

222Doc said...

I have always felt it was the inadequacies of some Lego parts that give it that unique'ness that makes one think out of the box to be able to do things many thought not possible. I have broke many a gear, twisted many axles and other parts as I tend to push them as far as i can and just a wee bit more just to be sure I am at the the full load. The parts are rather inexpensive as well so you can do this with out breaking the bank. truley a great product. But if they make parts more robust is good too, i will still test them to breaking force anyway. LOVE these films of TT trials and the crashes. These guys know how to have fun!

Conchas said...

Indeed, LEGO Technic system has its limitations, and it is not difficult to reach them.

The Hurricane is for sure a good example.


8275 got an errata for the instructions, to fix one common problem during assembly.

For the 8258, I'm not so sure about what Nathanaël was referring to, but the same LAs were revised after 8043 release.

Anonymous said...

If folks are breaking axles and gears, why doesn't TLG make them out of ALUMINUM? There have been metal Lego parts in the past. I know that they would cost more, but "You get what you pay for."

Ulf Andersson said...

"Pneumatics would have been a more suitable alternative considering authentic functions."

Yes, but the pneumatics aren´t strong enough to keep the
required pressure. Linear actuators stay
in the position you (by hand or by motor) left them in.
And when the linear actuators are
at their maximum, they realease
instead of breaking, like the
Technic Gear 24 Tooth Clutch

"In conclusion with LEGO you can build anything, but the system certainly has its limitations."

That´s true. But I guess that it
is the challenge in itself that
makes one try to elevate one self.
For instance: in my current MOC,
I´m using a standard down gearing
(having replaced the old 4,5V Technic Motor with and I´m using
to make 3 - 3,5 kg (6.6 - 7.7 lbs) revolve on a baseplate/foundation -
i.e. a bit heavier than the top
of the 8043 Motorized Excavator.
And I also use a modified version of
with four
(not necessarily the old one´s) - of course.

I´m quite happy with the performances of Lego motors
so far. And as far as MOC´s goes,
I think it´s in the human nature
to push things to the limit.
I mean: you build a ceartain
MOC because you can/know how to.

Much appreciated blogpost.

Kind regards from
Ulf in Sweden

ER0L said...

Good post, I agree with every argument. I would like to add the following thoughts: First I think the limitations are a result of a certain marketing strategy. Motorizing all functions means you need a lot of motors which make the sets too expensive. Lego rather tries to feature different functions to keep the models interesting. Second I think there is rather a steering problem than a motorizing problem. Maybe this explains the featured track models which are steered by two motors interacting. As long as there is no suitable solution - a servo - for steering I guess there won't be any suitable wheel models steered by power functions. Third: To get offroad models like trial trucks sturdy enough you need a lot of parts - which once again would probably make the sets too expensive. They rather produce models which look fine indoors than strong vehicles which are wrecked outdoors ;-) Just my two cents.

Anonymous said...

Let's face it, the Lego motors are cheap and they are made for limited types of use. Lego will never release any kind of vehicle that uses them that exceeds any speed other than slow because they will wear out far too easily causing an uproar from the consumer. And until lego starts making gears and other parts in metal, these larger remote control vehicles are going to continue to be hindered.

Al said...

I don't think metal parts are needed. What we would consider to be quite fast for a large set, would still be really slow compared to most other RC toys.

Whilst i'm sure technic as a system has it's limitations, and that they are good for making you think, the system still have vast room for improvement. The parts are better than ever but they can still be improved upon. A servo motor would be great, longer pneumatics obviously, etc etc you know the rest. We would still have many challenges and problems to overcome. But we would also have cooler, more reliable and more realistic sets aswell.

Anonymous said...

Thanks for the explanation of the problems! This post makes a lot of sense, in particular the comment about 8070. When it first came out I thought that Lego would "do an 8448" and include a gearbox, but it wasn't to be. As a result, Lego won't be making CAD$155 off me!

222Doc said...

We do have "servos" its the NXT set. I know most technic people tend to stay away frm nxt but alot can be done with programing for stearing. The offset is the weight perhaps and for sure the size of the servos and there shape. I wou;d like to see the NXT servos get a make over, like take the Large PF motor and add a rotational sensor, this would be very cool.

Conchas said...


The problem with NXT servos as you said, is size, form factor and to some extent also the weight.

IMO if Mindstorms wants to take one step ahead, it desperately needs something like the RC servos. Specially the form factor, as used nowadays everywhere in robotics.
Not new motors that look like the existing ones.

Menno Gorter said...

If everybody accepts the fact that Lego will be never light enough to make flying helicopters or fast enough to build lightning fast cars... ;-)

The more functions you add, the more weight or friction the project will have, the slower the result will be, the challenge remains to beat that....

Never accept a first attempt to be perfect, only use it for tests and make a better version.

In my opinion, the Hurricane can be finished for example, if Nathanaël wants to and the audience accepts that it might be a bit slower.

BTW: I wouldn't dare to call the NXT-motor a real servo; If you start the program the NXT doesn't know at all in what position the motor is!
And it's a shame and unLegolike the two electric systems of today are hardly compatible!
However: even that is a challenge. :-)

Finally, Lego is very good for training brains and patience. :-)

Anonymous said...

What do you mean the Hurricane can be finished? It looked complete when the pictures were posetd.

Anonymous said...

@Anonymous: Yeah, but it doesn't have the skid steer function.

222Doc said...

No the NXT wont at start but you can in programing, pluss the new motor block with pid looks cool too. Have yet to try this out in my Biped X2 but soon.

Lego Stalwart said...

As lego motors have become stronger, lego tyres have also become more grippy. Tyres such as the 20x30 would not generate enough grip to damage most transmissions and so you have a natural clutch.

The XL motor, unlike the older motors, has enough torque (ungeared) to damage lego, it can only be used in situations where the function allows for slip, for example, plastic tracks.

Simply, I think that the torque required for decent performance in medium to large wheeled models requires either pre-constructed drivetrains connecting the motors directly with bespoke parts(in a similar way to the internal gearing on an XL motor) or a selection of stronger, higher torque loading parts that possibly use a different fitting standard (hex?) to avoid confusion.

uLLo said...

I think, Lego should stay in its tracks, like 8860, 8865, etc.: it is not necessary to use motors for stearing and acceleration.

Lego TECHNIC shows HOW it works - principally.
When Lego begins with stearing and accelleration, than it is confronted with so many problems which - if not expensively worked out - will lead to unsatisfactoring results.

For me, PF should only be used for features (like today) not to make RC-cars..

If some AFOLs like to compete in TruckTrials with LEGO the may do so. But the should not demand more robust elements (when you start this - where should it end?)


Anonymous said...

The problem is that Technic parts and Power Functions motors were never created for use in motorized vehicles. Although I myself have created several Power Functions models with wheel drive that worked perfectly well, I have to admit that the motors work better when used to drive functions, ie winches or cranes. Metal parts are not the solution (although they would be really nice to build with!), mainly because the motors would reach breaking point before the pieces, not the other way round as it is now. If I was using an RC PF car driving at high speed using several motors, I'd definitely want the motor to break before the pieces. As uLLo said, if you start demanding more robust elements, where should it end? The whole point of Technic (in my opinion) is creatively finding the limits of the Technic building system, and stronger pieces would completely take away that experience.

James said...

I agree with the statements of staying with the good quality plastic that we currently have.

But I would like to see a new Power Functions element as well. I would like to see a "dumb" servo. that utilizes the same principle as electric solenoids (standard magnet affected by an electro-magenet) but with a rotational output.

Maybe 5x5x3 studs LxWxH. with two pass-thru axle holes. The axle holes would be geared together with a 2:1 ratio, and would self center. one cold turn -45 deg to + 45 deg, and the other would turn -90 deg to +90 deg.

This could be easily done with the current PF connector (two electro magnets, each wired to one of the C1 or C2 pins in the PF connector)and grounded to the constant negative terminal.

A servo like this could be great for manipulating toggles like transmissions or pneumatic valves, or for full lock, self centering steering. It would be interesting to see how the PWM signal from the PF Receiver would effect the electro-magenets.

Al said...

Yes, the hurricane can be "finished" as I have done it. But it required a complete redesign from scratch. BTW when I say i've done it, what I mean is it all works fine with four steering modes (2w steer, 4w steer, crab steer and turn on the spot. All steering and steering wheel powered by one motor and gearbox(s)), 2 v8 engines, 3 differencials, one PF m-motor (for steering) and 2 RC buggy motors (for drive). All steering modes are controlled by two levers. When the turn on the spot mode is selected, The wheels on the drivers side are automatically revearesed via another gearbox. Problem is I really can't be bothered to do the boring bodywork just because there is no challenge in it!

Conchas said...


Would be great if you can show it to us, even without the bodywork.
Easier to see how did you made the mechanics. :)

Al said...

Once moderated, the pictures are viewable here:

The pics are crapola, but they should give you an idea of what it's like! It all works fine without any gear slippage. Can turn itself on the spot, on the ground. Speed is good but it's geared a little too high for trial trucking but with some extra gearing down it will do that also. Much respect to NK for even attempting this as it was quite hard to get working. It's thanks to his efforts that I was inspired to make my own.

Conchas said...


It looks also interesting, your solution to control the different steering modes.


minks502 said...

If TLG produced a Car that included drive and steering with the power function system, everyone would complain about what a shitty job they did(the last excavator for example) I believe that their models are only to inspire people on what could be done. Who wants to buy a framed jig-saw puzzle? I don't.

Ulf Andersson said...

Thanks to

Power Functions Extension Wire
"Allows you to connect your LEGO 9V electric systems to the new Power Functions!",

you are not limited to the PF M-Motor or the PF XL-Motor:
you can use the whole range of
9V Motors.

Al said...

Which is great as the ungeared 5x4 9v motor and the buggy motor remain my favorite motors! Although I do really like the form factor of the PF motor alot more, espescially more than the RC buggy motor. The perfect motor for me would be a PF ungeared motor that has lots of power!!!

Conchas said...

From the discussion a little above, let me recall that LEGO indeed made a series of proper models for high speed and robust steering. These also had specific parts designed to cope with the needs of such models.

And these were para of the Racers series, compatible with LEGO Technic to some extent.

I'd highlight the need of special parts, so that the models won't break apart while playing.

Conchas said...


I just reminded that I should congratulate you. Instead of just criticizing Nathanaël's work, you tried something different and came up with your own solution, to prove it was feasible.
I believe this was also one of the intents from Nathanël. To provide some inspiration source to other builders out there.

I don't think the bodywork might be boring or that trivial. Would like to see your model also finished and of course one video featuring all the steering modes and drive capabilities of your model. :)

Mark Bellis said...

PF was always going to be limited, simply because the market includes children as well as AFOLs. This set the current capacity at 400mA per channel from the IR receiver, as well as the battery capacity. It's good that the motors are not so often the weakest link in the chain from battery to movement. We waited years for those XL motors!
I once drive a 4-wheeled robot, with 4 12V train motors for power, up a pillow at 45 degrees, using a 12V 6A power supply. It went up the pillow fine but melted the pole reverser switch!
I find the same limitations with trains - larger trains need more power, more motors and more electric power than the system is designed to provide, either 9V or PF.
BTW we have pneumatic servos already (great for doing vehicle steering that will centre) and I'm sure you can invent a way of making electric servos using PF parts - try connecting a PF train handset dial to a geared down motor shaft that is driven by the IR receiver on the same channel, hence the motor speed will reduce as it nears its target. The initial "move" command would come from a bang-bang handset. It's an extension of these machines:


Al said...

Thanks conchas. I would love to show a video. If I see my brother again soon we'll have to film it in action if you like.

Hopefully I have offered some inspiration to those who want to revearse engineer mine and make a body shell ;^).

Al said...

BTW if it was his intention to inspire with his jeep hurricane, it certainly worked!

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