Hod Carrier

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  1. Another little video to have a look at showing a few additional tests I carried out. Click on the pic below to see how things have progressed. If you'd like to build one of these vehicles yourself or use the principles for a MOC of your own you can download the .lxf file for the chassis mechanics. Notes on the download: Due to some issue with LEGO Digital Designer the centre axle in the passive steering link is not the correct length. It should be 7 studs long not 6 studs as shown in the file. If using the steering link take a few moments to adjust the length of the link so that both axles centre correctly. The floating 1x2 plates are the axle deflection stops which prevent excessive movement. These will need to be attached to the underside of whatever chassis you wish to build.
  2. I've been asked a couple of times over on Flickr how these vehicles perform on LEGO points/switches. Embarrassingly I hadn't actually got any points to test them on, but just today the postman brought me a pair that I had ordered specifically for the purpose. So this evening I set them up, put the train in motion and, well, click on the box below and see for yourselves.
  3. @icemorons The "bunching" issue isn't caused by the last axle but by the pivots for the magnets on the couplers. It's like trying to push something with wet spaghetti. It's true that locking the last axle should also have the effect of locking the other axle on the same car via the steering link, but the next car would still "bunch" because of the magnet pivots. The simplest way to deal with "bunching" is to have rigid couplers between each car (effectively a Jacobs bogie), but the trade-off with that arrangement is that you limit the movement of each axle relative to each other and I think I'd probably lose something in the forward motion stakes if I did that. I'm sure that there may be other alternatives, but it's difficult to work out how each vehicle would "know" it's on a straight and not a curve. It couldn't do it through the motion of the couplers because "bunching" creates the same movement as going forwards through a curve, and in this circumstance it's a motion that I want to create. The only way would be by reference to the track, as @jtlan's Umbauwagen 3yg does, or by reference to the body positioning relative to the neighbouring car. I'm starting to be of the opinion that I can live with "bunching" provided that it doesn't cause derailments, and the increased weight of these vehicles compared to the first proof-of-concept prototypes seems to prevent that. Using a passive steering link on the last car does at least steer the last axle into the bends and seems to keep things relatively ship-shape and Bristol-fashion. The last car issue that I'm having at the moment is trying to get the axles to self-centre when they come out of a bend. They do manage this in the end, but it's mostly done by applying more speed which increases the draw force through the couplers. In this respect the passive steering link can help because if I apply enough power through the coupler to centre the first axle the link will see to it that the last axle centres also.
  4. MOC - Lego Clockwork Locomotive

    It sounds as though you're making some good progress there. I'm still a little surprised at the gear ratios you've selected, but you have clearly done your homework and selected them on the basis of sound scientific evidence. What scope is there to modify the motor itself? I'm just wondering if there was any way to change the spring for something more suitable (longer...? softer...?) that would give it's power in a more controlled, gradual manner more appropriate to railway operations. I was just wondering if you'd got access to a motor that's already blown up that you could explore the inner workings of.
  5. A little update for you all. The second prototypes have been built and tested and the results are in. I have hit a bit of a snag, which you will see if you watch the video all the way to the end. The failure of the last axle to centre on it's own is vexing me. So far I've tried; altering the distance between the pivot point and the axle to see if more force could be exerted on it to make it centre, adding and removing weight, changing the pivot design from a 2x2 turntable plate to a pin and hole, and raising the chassis so that there is no way that the underside could possibly rub against the top of the axle assemblies and create friction preventing the assembly from turning. Frustratingly none of these attempted fixes have had any affect whatsoever. About the only thing that makes the last axle behave correctly is increasing the speed. I can only conclude that the problem is being caused by internal friction in the pivot, so I'm giving serious thought to stopping at the RC model shop on my way to work and picking up some sort of plastic-safe grease to sparingly apply and see if that helps at all. While I was tinkering I thought I'd have a look at passive steering. The results of this are mixed. The centring problem affecting the last axle makes this test a little inconclusive, and actually makes that problem worse. While the axles move independently it's only the last axle that fails to centre, but physically linking them using a passive steering system means that now both axles on the last car fail to centre. There is also some issues with axles being steered the wrong direction, but this is actually not as bad a problem as I anticipated before. It's actually quite a fleeting phenomena and the axles are not deflected too far for binding to be a big issue. That said, it does help when propelling (pushing) a train because the last axle is being steered into the bend under the influence of the passive steering rather than doing it's own thing and potentially causing a derailment. However, as predicted, passive steering does not prevent "bunching" as that has more to do with the manner in which the vehicles are coupled. Basically what's happening is that I'm trying to push something with a hinged bar, and of course that's not a great recipe for success. As a result of these tests I think that, on balance, if you were wanting to run a formation of long wheelbase vehicles you could get away with having free-castering vehicles and only the first and last vehicle using passive steering. Your comments are invited. I'm interested to know what you all think and what suggestions you may have for things I might have missed. **EDIT** Images are clickable video links. Enjoy!!
  6. Forgive me if this is in the wrong section. I'm looking for recommendations for a UK-based trader to carry out some custom printing onto LEGO parts. Google throws up masses of hits but I've no idea where to start. Quality, price, reliability and the openness to tackle a very small number of parts are my selection criteria. Thanks in advance.
  7. MOC - Lego Clockwork Locomotive

    I look forward to seeing how you get on. When I mentioned the gearing I was thinking more about gearing it down rather than gearing it up. Or has that already been tried?
  8. MOC - Lego Clockwork Locomotive

    The pullback motor probably isn't the best candidate because it's designed to give all it's power quickly to produce a rapid burst of acceleration rather than a gradual release of energy for longer running. However, I do admire your enterprise in trying to get it to work. I'm not familiar with clockwork motors so I can't help much with governors. I've had a quick read of the internet and it seems the most appropriate type might be a centrifugal brake of some sort, but I'm not sure if LEGO is the right medium to build such a thing. Probably the most LEGO-friendly governor would likely be a fan, but that's going to look weird sticking out of the top of a train. Maybe it's going to come down to finding a way of using the power delivery of the motor in the most efficient way possible. It looks like you've got the drive geared quite high; something like 1:5. If you're getting loads of wheelspin when you release the brake, the motor is just spinning a lot of it's power away uselessly. It also sounds like the top speed is too high if it can't manage curves. Have you tried any lower gear ratios? If you could get the power from the motor down on the rail with less wheelspin you might find that the train travels further and at a more controllable speed. Another consideration might be the weight of the engine. Train wheels don't tend to grip very well, but increasing the weight can help increase the wheel adhesion which would help reduce wheelspin. A heavier train also has greater inertia, so it would accelerate more gradually.
  9. MOC - Lego Clockwork Locomotive

    Oh yes!! I love this. So retro and so cute, and such a different idea. Would it be possible to show some more detailed photos of the drive mechanism, as I think I would be interested in building one of these too.
  10. 2018 Lego Trains

    Who do I see about claiming my royalties?
  11. @Legopold The next prototypes will be conventional “brick and plate” construction rather than Technic, so the weight bearing pivots should be much easier to construct and more straightforward in operation. But we shall see. That’s the joy of prototyping. You build, you test, you learn and you adapt.
  12. @Legopold You’re most welcome. I agree that adding weight to the centre beams of these prototypes would be likely to overstress the pivots and affect the performance, but these are just proof-of-concept models not designed for anything more than checking how the castoring effect might work. The second prototypes will be of a completely different design and construction which should be better able to carry more weight.
  13. @Legopold Funny your question should pop up when it did because it's something I had thinking about just at that precise moment. Counting across the coupling from the centre beam of one test vehicle to the centre beam of the next, there are a total of four pivot points; one each for the axle assemblies and one each for the magnets on the couplers. This is why the test vehicles experience "bunching". To dial this out you wouldn't want any more than two pivots, ideally the ones for the axle assemblies only with the magnets mounted rigidly. Once coupled to a neighbouring car this would, in effect, create a Jacobs bogie across the coupling (assuming no flex between the magnet faces themselves) and "bunching" would be eliminated. On the down side, such a rigid coupling between the cars would not permit each axle to caster freely, generating friction between the wheels and the track. What you would be creating in effect would be rigid bogies with a wheelbase of @10.5 studs. The biggest impact that I have noticed was with the amount of axle articulation you permit. Moving the axles either closer or further away from the pivot points doesn't seem to make as much difference because the amount of deflection is the same. The limiters on the test vehicles (the yellow structures behind each axle assembly in the renders) allow @16 degrees of deflection which, by happy chance, is about the correct amount of deflection needed for a 25 stud wheelbase vehicle to negotiate a standard LEGO R40 curve (obviously more or less articulation would be required depending on the wheelbase of the vehicle and the radius of the curve). In this configuration, no matter where you place the axle in relation to the pivot points, it will always deflect by up to @16 degrees when "bunching".
  14. @zephyr1934 I absolutely will. I'm hoping this is something that other people will find helpful too. Just as an aside: Some people might be wondering why I haven't explored the use of some form of springing to help with centring the axles. Well, part of the reason has already been touched on elsewhere by someone else on this board, and that is to do with springing rates. Whatever method of springing that you choose it would need to be strong enough to centre the axle but not so strong as to prevent it from articulating at all. In order to overcome the "bunching" issue it would have to be quite strong indeed, and that would probably defeat the purpose. But the real reason is that my interest was in exploring the castering effect and it's potential uses. I have no wish to try and prove whether one idea or another is best, but simply to discover whether or not castering works.
  15. What's the current state of third party 9V?

    I think that what @McWaffel is suggesting is that third party 9V appears to be dead.