Brickthus

The saying that looking at a Playmobil catalogue shows what TLG will produce in 2 years time proves true once more! Are the level crossing lights printed on tiles? I hope there is a PF light conversion in the instructions. The 7866 12V crossing was great, but the light bricks, point motors and wires made it complex and expensive. It was £45 in the UK in the 1980s. The thing about crossings on a model railway is that the barriers would be down 2/3 of the time because the train service is so intensive! Real crossings might have train detection at least half a mile away, depending on line speed, which would keep the barriers down all the time on a model railway because there's rarely more than half a scale mile of track even in OO or HO (N-gauge sometimes has a scale mile at shows)! It might pay not to be too prescriptive in track furniture for a level crossing because different countries do them differently. The UK 3-light system is more complex than most. There's an extra half a cross for double track and each subsequent track too. I think 4-track crossings are rare now. Mark

Very nice Ralph. I especially like the roller-shutter doors. How long did it take? Mark

The valves are stiffer than the old light grey ones, but that's better for long term seal reliability. I think a small cylinder can still push 1 valve. A 48mm cylinder can push 4 valves in a 2x2 configuration, which is not worse than with the old valves. I got some non-official tubes in 25m lengths. I make tens of each size at a time, usually 2, 3, 4, 5, 6, 7, 10 and 15cm. I also use more 3.2mm stiff tubing for the straight bits, to reduce the balloon effect. Therefore I cut more flexible hoses into shorter lengths for the corners. I'd really like to get a 100m reel of the 3.2mm stiff tubing. Let's send TLG a positive message about the return of pneumatics to the range! Mark

It depends whether you want to be able to run 3 trains or only 2. You can have 1 train in the station loop, one in the inner half loop and one running round the outside. Then run one into the yard front left and run another to swap them round. If you didn't have the inner half loop there would be nowhere to stop the 3rd train. With a city layout you can always put some track in a tunnel and build the city over the top. Just leave plenty of width for train overhangs! Make buildings removable (on a layer of tiles with anti-slide location parts) so that you can rescue a derailed train if necessary. Curves tend not to be fixed down but supported from the straights at either end of the corner. For ballast I have attached some plates to the curves for the trackbed and added ballast on top, then lay the ballasted curve on tiles (you can get 8x16 tiles to cut down the number of small tiles required). Pictures here and here. To ballast a curve you need: Plates to go underneath the curve - maybe including 4x9 wing plates if you want no see-through gaps. 1x1 plates and perhaps some with clips to do the ballast. Perhaps 1x2 with door rail to reduce gaps on the inside. 1x4 and 1x1 tiles for the sleepers if you do a 1M sleeper scheme. A 2M scheme is easier, just using the studs on the curves. Mark

Can we get a better image of the battery box, as displayed on the train set boxes? It is not certain that the LiPo battery is included because the price points may be too low for that. That would also remove the need for the charger to be included. Instead, it might be a new type of battery box. Might such a box be the same size as the LiPo one and contain 6 AAAs? Mark

I exceeded the LiPo battery current limit with two 8866 train motors (though 9V train motors were fine with the same load)! The battery box can supply about 800mA and an XL motor can draw as much as 1.5A. An IR receiver is limited to 1A. Since the LiPo battery box is light, having one per motor would be OK for weight if you could afford it. 4x battery box, receiver and XL motor = £246! AA battery boxes adding weight might not be a problem for a tracked chassis (more grip is good), unless you were driving it on an icy pond! It would be possible to add a greater power system, still controlled by the IR receiver. I have used a circuit to read the motor output of a receiver and convert it to a sensor voltage for the WeDo system, so a similar a circuit could drive a power H-bridge instead of generating the sensor voltage, and could use a set of RC car NiCds (or NiMH or Li-ion cells) and a few RC car motors for serious power! Mark

Given that the maintenance vehicle on the box is lifting a track panel, I'd say it's like .Buy two level crossings and you can re-enact it! There is a great range of hydraulic tools for real vehicles of this type. The ones used here have a pair of clamps for grabbing the rails. As you see in the video, sleepers can fall off the rails quite easily, so it's best to grab the rails, which are the heaviest bit of the panel. I saw another tool for tamping ballast, so it's not just a tamper vehicle that can do it. I was impressed by the co-ordination required (note the use of the horn). If one driver pushed his joystick the wrong way, both machines might tip over! Mark

Very nice loco. The best ones usually take a long time. My Class 14 diesel loco has counterweights, though they are on a jack shaft. Not many British locos have separate counterweights on the same shaft as the wheels. Mark

Much better! It lines up now. This engine solves one problem that arose as soon as I had too many cylinders for one vehicle. The feeling of "Hey, I can make a 40-cylinder engine! What's the point?" It's just that every set has to have an engine. At least a few sets manage to miss it out, but the proviso for me is that something better is put in instead, e.g. a JCB could have a motorised air compressor in place of the engine. I'd quite like to do an aircraft engine - not sure a ring of 7 or 9 cylinders is possible with these parts because of the big peg hole extensions each side, making the radius too large, though they could be mounted the other way on. Also a set of 7 or 9 big end pieces would be required, fitting all lobes into 2M length. A 2-ring engine would be great to make. Mark

This circuit could help with IR control for large layouts and tunnels. My idea was to put the IR LED in a tunnel so that there were no IR "not-spots" along the track. The receiver would be visible to the operator but out of sight of the public at a show. There's no reason why you couldn't use two IR receivers in parallel, as long as they received the same signal. Also, use receivers per track section, with insulating tape at the rail joints. That way you can use separate transformers to supply the power. I'm working on hybrid 9V/PF trains, which would use the PF battery for the lights whilst running off 9V track but would be able to switch to battery power for the motors too, to go over double crossovers and other plastic track sections. I have found a need to isolate the PF power from the 9V power because the 9V power attempts to charge the battery, drawing too much current! I've added a relay circuit to solve this and it is working in the prototype, but is not ready to publish yet. For the PF LiPo battery, we need more power in the smaller size - both attributes are limited by the technology! Let's hope there's a new battery in 3 years' time, which has double the energy density (riding on the back of mobile phone and laptop battery technology!). We also need faster charge time, though the charger puts out 700mA already. Faster charging might not be possible due to child safety restrictions on the maximum voltage and current in a toy. I hope we get inductive charging - a device that sits on top of a track piece (4x8 and 2 plates high with smooth top), making it look like a level crossing, containing coils, with a wire to a transformer that supplies a charging signal. A 4x8 device containing another coil is slung under a wagon to pick up the charging current, with a wire going to the battery on the train. Inductive charging mats are in the shops now, able to charge a phone or DVD player, so hopefully such a device for LEGO trains is not too far away. Mark

Look into the nozzle at the bottom. If it isn't clear, use a 1.4mm screwdriver to bore it out. Be gentle! That should unblock any air blockage problem. I've bored out some cylinder nozzles to improve performance. Bottom ones are fine but with top ones you have to ensure not damaging the cylinder top seal. Anything else might be a stuck piston, which would require opening as above. Not done it myself! Mark

Does it not work just because there's no video? This is the principle that anyone can throw a few pieces together and take a picture! Well I'm not James May! I don't do bad engineering on telly! My personal integrity means that what I share is appropriate to the readiness of the technology. * The original mechanism works well and there is a of it. * It also works using the small cylinder, but is more jumpy than with the larger cylinder. There are pictures of that. * The steam engine works but is not very reliable yet. It works well enough for a few pictures, and for others to try it. How could it work better? By understanding the principles. This takes time (unfortunately too much maths in this case). A set of reliability improvements would be required before making a video. A few extra components, such as extra crank bits on the dither, supported in beams, to stop the cranks falling off the axles next to the pulleys would be a good start. That might facilitate a video, when I'm ready, when I have time, when the technology readiness supports it (i.e. guaranteed >90% chance of working for 10 minutes at a time, including reversing). No-one has done closed loop stop-anywhere pneumatics before. It takes time to develop it. A video without proper understanding would be a sham, and bad engineering. I think the cart is before the horse. The how-it-works always comes before the video, otherwise I would have nothing to put in the script! This is proper engineering. the technology is new to LEGO. It takes time, behind the scenes. It's not done on stage. It's not the Strictly Brick Factor talent show! LEGO is about hands-on, each person trying it out for themselves. I have posted that amount of information so people can try it for themselves and help in its development. The video of the original mechanism demonstrates the principles working. This steam engine is just 2 of them together. Each mechanism drives a wheel crank. Because the cranks are at 90 degrees to each other, each pushes the other over top dead centre, back into a region where it can apply force again, just like a real steam loco. I showed it working to UK AFOLs a few weeks ago. It worked till the dither motor batteries ran out Unfortunate that you saw it at the end of the day with flat batteries! This is far from the only LEGO engineering I'm doing at the moment. I have to make Power Function hybrid trains work too, to facilitate the transition from 9V to PF! This involves lots of electronics. Mark

The valve integrates twice by turning lever position into pressure, hence two 1/s blocks. The piston differentiates twice by turning pressure into position, hence two s blocks. The valve multiplies the pressure by the pressure of the compressor, which can destabilise the system if it gets too high (pushing the valve out of its linear region). The region is not quite linear. I think it approximates to a sine curve from -90 to 90 degrees as the circular track within the rubber piece reveals more of the round port in the casing. The long levers are an attempt to use this region, with the lever length fitting with the dither crank length of 0.5M so that the dither covers only the full linear range when the input vs. feedback sliding beams are aligned. The feedback and fast dither exploit parts of he non-linear range. As long as part of the dither travel is in the linear range, the average pseudo-PWM output will have some usable linearity. In that sense the dither extends the linear range of the valve, which is the only reason why the system works at all, because the linear region of the valve is so small! Wish I had the time! I'm glad this system in its simplest form uses just 2 valves and 1 cylinder, making it accessible to anyone with an 8049 set! If you'd like to make a Matlab model, a few variables: The Pressure is 20psi. Some people use up to 60psi for engines but I recommend no higher than 25psi for significant periods, and 30psi max for any model that is not free-running. The dither motor turns at about 240rpm. This is deliberately faster than the control loop response time. System performance is impaired if it gets too slow. Obvously the piston areas are unequal, but that is sorted out by moving the null position of the red-blue beam offset in the original system. I think there's data on pneumatics on the web somewhere. As I say above, the linear region of the valve is so small that the dither (using parts of the non-linear region) is the only thing that makes the system work! This is like PWM for an electric system, taking x% of the time at full power and y% of the time at no power to make an average of z%. In this case we take x% of full valve travel at on end, y% of linear valve travel and z% of other-end valve travel to make a% of the supplied air pressure. This is like an op-amp with a slow slew rate, taking its time to go through a linear region between saturation at either end. It's also like over-driving an amplifier e.g. when playing an electric guitar, so that the waveform is clipped at both ends. That probably means we would need to solve a differential equation in three regions! I'm not really a glutton for punishment but these equations just seem to crawl out of the plastic! I finally make the step to a linear system and what happens? A load of maths descends on the problem! What I would like to see is this system being used in MOCs. Even better in a set, though that is a long way off if it ever happens. I've made the steam engine from the basic system, and it's not the most efficient pneumatic engine. That is what I expected. I'm working up a steering mechanism, which is one of the most appropriate mechanisms to be controlled by this system, given that it needs to stop anywhere. I have ambitions for a flight simulator platform, or maybe a gymbal, with 3 or 4 systems at the corners doing realistic hydraulic motion. A similar application is helicopter rotor pitch control, needing at least 3 systems and some addition logic for the collective and differential pitches. Mark

Yes, without the dithering it moves only as pneumatics usually move. Dithering is a standard technique in industrial hydraulics. Unfortunately the maths varies between A-level and degree level! I don't relish it quite as much as the modelling! The air pressure in a pneumatic cylinder can only affect the acceleration of the piston: Pressure = Force per unit Area Force = Mass x Acceleration We are applying an air pressure (acceleration) but what we want is the absolute position of the piston. The position is the double differential of the acceleration with respect to time. Therefore the cylinder is a double differentiator because it turns pressure into position. We measure position and feed it back to the valve. The valve is a double integrator because it uses position to control pressure. This diagram is the control diagram for the system. there are two similar systems in the steam engine. "S" is an integrator (LaPlace), "1/S" is a differentiator. The position is used to drive wheels. The drive is sinusoidal. A steam engine takes a multiple of the signal 90 degrees out of phase with the piston, to feed it back to the valve gear. 90 degrees out of phase from a sine wave is a cosine wave, which is the single differential of a sine wave. (+ or - cosine used depending on direction; the differential of sine in an equation is -cosine) A steam engine also takes a negative multiple of the piston position to feed it to the valve gear. 180 degrees out of phase from a sine wave is minus a sine wave, which is the double differential of a sine wave. Hence multiples of the single and double differential of piston position are used to determine the next valve command. The Fibonacci series (1,1,2,3,5,8,13,...) works the same way because the two previous results are used to find the next one (albeit with multiples of 1, and not using sine waves). Believe it or not, my colleague's 8-year old child's maths homework said "find the equation of the series"! They definitely wanted engineering dads to get involved :-) Mark

Very Nice! How many hours' work did it take you? I guess well over 50! Will it handle curves OK: - are the couplings attached to the bogies or the loco body? - Is the wheelbase of the bogies OK with curves or have you replicated the wheel turning geometry from the real thing? Mark

It fulfils both markets then! Must be a good set. Will Woody's longer legs work with train doorways though? Headroom for minifigs is already a bit tight. Mark

Yes, I was aware of the worm-on-diff method, but I wanted to do something different. The lever method also fits well with the steam loco concept. Thanks for the maths explanation. That'll help when I look it up. I wonder if Walschaert or Stephenson did these equations when they designed their original valve gear schemes? Not often we get to do serious maths with LEGO! I'll look for the design intent as well as what the equation is telling me, to see if the two will meet in the middle! Mark

The phase of the two dither cranks doesn't matter, though there may be an optimum relative phase to be discovered. The idea is that the dither is much faster than the response of the cylinders and valves, so that it evens out the pressure to both sides of the cylinder alternately without provoking inadvertent movement of the cylinders. The cylinders each push and pull, with air pressure on either side (like a Class 9F steam loco, 4 pressure strokes per wheel revolution). The 2L dark grey bit keeps the lever in range because it cannot "fall over" by more than a certain amount when the lever is pushed. It's not an official way to limit lever travel but the limit stops the gears disengaging by pushing the lever too far. About +/-20 degrees is the usable range, which is quite adequate. A proper limiter would be in the next mod package! There is a fair bit of torque in the gears, which could move the lever on its own. I might use a worm gear in the cab, like some real steam engines use. That could also be motorised with PF. PLMKWYT is the acronym Please Let Me Know What You Think - you understood without realising it! Mark

I've posted details of my pneumatic steam engine in this thread. It works like a real steam loco but is not the most efficient LEGO pneumatic engine. Nevertheless it is reversible and could be made to run on L-gauge track with BBB wheels and a few tweaks. Please add your comments to the discussion in the original thread. Mark

From my original concept of Continuously Variable Pneumatics in this thread I have developed a variable pneumatic steam engine. There are two of the original CVP mechanisms in this model, with the driving wheel shaft connecting them together. The two mechanisms share a dither motor by using belts (because they are 90 degrees out of phase). The piston drives the wheels and also provides feedback to the valve position on its own side. The driving wheel axle connects to the other driving axles with the usual steam engine rods. The driving wheel axle is geared onto a valve gear axle above it. In the picture above, the timing of this axle is the same as that of the driving wheel axle because the black lever top left is vertical. The phase may be advanced or retarded as the black lever is pushed forward or backward. The position of the valve gear axle moves the upper dark bley sliding rods on each side, which moves the valve levers by varying the sliding positions of the centres of rotation of the dither pulleys. Given a continuous air supply, the wheels will rotate forward or backward in response to the position of the lever. The variable phase gearing uses a pair of triangle frames and 16-tooth cogs, the frames pivoting about the valve gear axle. The valve gear and feedback perform the same functions as the standard Walschaert's valve gear or Stephenson Link Motion on a real steam engine. It's not actually the most efficient LEGO pneumatic steam engine, certainly not a patch on the V8 pneumatic engines doing 1500rpm, but it works in a real way and is reversible. I think its speed of rotation also has proportion with the extent of lever angle movement from the vertical, just like the reversing gear on a real steam loco. I will try different phases for the valve gear axle (real steam engines are more likely to have it at 90 degrees +/- delta to the driving wheel axle, rather than in phase +/- delta as you see it above). The complex bit: The valve gear adds together a multiple of the differential of the piston position and the double differential of the piston position to set the valve position command for the piston. Therefore it solves a 2nd order differential equation, which I think might have sine and/or cosine solutions, given the way it works in practice. I'll have to look up the maths in a book to prove it. If the mechanism were smaller then exchanging the wheels for BBB ones and lifting the bottom of the frame in front of them would allow the loco to run on L-gauge track. Obviously it wouldn't fit in the boiler without some shrinking work! I used the small cylinders to fit better with the loading gauge of L-gauge trains. Positional accuracy with the small cylinders is more jumpy and more prone to deviation with variations in air pressure, but it has enough power to turn the wheels. I have also added pictures of the original CVP mechanism with the small cylinder and my first attempt to control the 8421 crane jib height with the original mechanism (WIP) in the CVP folder. Surely a pneumatic steam loco is one of the holy grails of combining LEGO Technic and trains! More info here and pictures here. PLMKWYT! Mark

No, but I have one that will climb a pipe or rope (naturally, not with wheels). Photos in process, will post here when I have time! Mark

To use PF, I would start with an ordinary carriage base rather than wrecking the RC one, as it's an expensive custom part. PF uses a different IR frequency to RC. PF is so much more versatile that I wouldn't need RC anyway. It is possible to send the RC codes from an NXT with the IR Link sensor. The same is true for PF, so you could have a common NXT controller. Other than that, there's no point modding RC to use PF. Once you've installed a PF IR receiver you might as well go all the way and install the PF battery box as well, hence no need for any part of the RC chassis. One thing to be said for RC - it's a ready-to-run system with all the parts in one box. Therefore it's easier for the "instant gratification" generation. I wonder whether one of the PF trains next year will be all in one box for that reason. Parents might struggle to pick the 5 extra sets plus track to go with the Emerald Night, unless they all appear in one pack, as they did initially. Mark

Thanks for the name drop Dave I suggest that trains are more likely to use the PF train motor, as it's easier for a younger customer. That is where I would urge caution that might counter some of the "supporting the line regardless". I have found the PF train motor to be geared too highly for AFOL trains. It's fine for kids who enjoy driving trains as if they were Scalextric cars (flying off at every corner) but it doesn't have the same controllability as the 9V train motor. When I bought the PF train motors I did so without prejudice - I wanted to cerify that they were a drop-in replacement for the 9V train motor. I'm disappointed for the whole AFOL community that they are not. This leaves AFOLs with primarily PF XL-motor powered steam trains (like Emerald Night) and dual PF medium-motor powered diesels (one motor per bogie, mounted vertically on the bogie to avoid torque steer, the whole rotating within the loco body). This is a considerable design philosophy change for AFOL trains, not insurmountable, just inconvenient. We need to petition for the PF train motor to have the same gearing as the 9V train motor, such that it is a drop-in replacement. The PF LiPo battery and IR receiver work well with two 9V train motors in the loco, so why not? Comparison between the PF train motor and the 9V train motor is something I asked of Ben, but unfortunately he's dismantled the train test rig If it were not for this one mess by TLG, I'd be with you in saying the system isn't as bad as people think. My reasons for pushing the boundaries: - I'm an engineer, both by trade and by character! It's one of my roles in the community. - Someone needs to sort out the PF system to facilitate AFOLs buying into it. I want to get us to the stage where we're as happy with PF as we have been with 9V, and it takes work to adapt. - My trains are bigger than many people build, so I have to be sure the power capability and reliability are there, in order to exhibit PF trains. - I have a couple of crossovers, one of which I've motorised with pneumatics, but I need to use PF trains in the yard because of it. That delays my railway layout completion for exhibition. I hope there isn't another similar hiatus before I've completed it in a few years' time! I have found some really positive things about PF trains: - The battery is easily as good as its price tag. It works really well and will drive 2 motors easily. - The lights are the most versatile we've ever had and they fit in smaller spaces and are brighter than their predecessors. I was privileged to help design them (Philo, Stefan and I sat round a table one night in Billund and drew the ideal light, designing it to fit into other bricks. The only compromise from that design was that the wire had to be incapable of being pulled out, which meant the light couldn't go right through a beam hole). Now I make circuits to set them automatically to the train's direction and keep them on when the train stops. - The electric parts may be placed where we wish, unlike the RC train chassis. - The IR receivers are becoming more versatile, with 4 extra channels (usable by NXT IR messages). They can also be cascaded to get 128 bidirectional channels, even without the extension. There's just the PF train motor power to sort out, but those who have built with 9V train motors can continue with those motors for a while yet. BTW for permanent public exhibition (e.g. discovery centres), a little bird told me that in constant use a life of 3 months is expected from PF train motors, with the track lasting 9 months. That is with 6-wide trains. Bear in mind that AFOLs would do two 8-hour days at a show, so motors should last for 45 shows and track for 135. Mark

For accurate dimensions, look for UK Class 58 diesel loco - we exported them all over Europe when we got newer diesels! I have a book with 4mm scale drawings and specs, called "British Main Line Diesel Locomotives", which has pictures for classes 15-67. Mark

In the light of the above explanation of why there will be no train cars... We have to buy more Emerald Night sets: - add the carriages to the engine - turn the remaining engine parts into something else At least we're not forced to buy a motor and battery with each Emerald Night - therefore it is feasible to buy more sets without making more engines. Green tanker anyone? The question is, would TLG make more EN sets if we bought the lot sooner than they expected? If not, could we petition for there to be one AFOL exclusive train set per year or two, while-ever we bought them? The recommendation for the RC train sets, on the TLG website, is to add no more than 2 carriages to the ICE train and no more than 4 wagons to the goods train. This indicates that TLG don't design trains to have a lot of wagons. They couldn't pull them if they sold them. At least the train power and market policies are consistent! TLG is no longer in the ready-to-run train market. We just have to be creative ourselves - that's what it's all about! I think this century MOC trains are the best anyway. Mine are here. I'm working on hybrid trains, to make PF and 9V trains sit more easily alongside each other. We have to be creative with the electrics too! Mark