Hod Carrier

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.

Who do I see about claiming my royalties?

@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.

@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.

@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".

@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.

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

@McWaffel The axle arrangement is very straightforward as they simply pivot independently. The key detail is the offset between the line of the pivot and the line of the axle, as this is what allows each axle to caster. Most of what you can find online concerning the castering effect is relating to car suspension and steering set-up. However, the basic principle can be observed by watching the behaviour of the wheels on a supermarket trolley. It is the offset between axle and pivot that makes the wheel effectively "trail" and the forces acting on it ensures that it self-steers and aligns itself with the direction of travel. It is this effect that I am attempting to harness to create self-steering axles and, for the most part, it seems to have worked. @LEGO Train 12 Volts I'm already ahead of you. The second prototypes will be of more conventional "bricks and plates" construction (which I am hoping will form the basis of a heavier MOC) and will have the facility to use a passive steering link between axles. However, I am not confident of the results and it may actually be a step backwards. The problem is the phenomenon I've been calling "bunching", which is what you can see in the last overhead shot of the second video. In normal hauled operation the couplings are kept in tension and that is what allows them to caster. However, when the vehicles are being propelled the couplings are in compression and this actively forces the axle out to one side or the other. All that a passive steering link will do is to transmit the steering impetus from one axle to the other, so if one axle is forced out of alignment it will force the other out of alignment also, and that is what is already happening without a passive steering link. This "bunching" issue may be insurmountable without some means of centring at least one axle, but I'm currently at a loss to see how that might be achieved without somehow restricting the axles ability to free caster. However, I am hoping that a passive steering link may at least be enough to stabilise the rear axle sufficiently that it won't derail when propelling, so it will be tested. The other potential issue with a passive steering link is that it may affect the train in forward motion too. There may be times when you want the axles of a vehicle to steer in opposite directions, such as going through points/switches, which is why my test track includes a couple of S bends. Free castering allows this to happen very successfully, but adding a passive steering link could prevent this from happening resulting in the friction I'm trying to design out. That said, the concept seems to work very well within certain parameters. You could run an entire train formed of long wheelbase two axle vehicles with castering axles provided you don't want to propel (push) them. If propelling is on the agenda they should behave reasonably well provided you have a non-castering vehicle to stabilise the last axle and stop it from derailing. It's not shown in the video, but the test train did several laps of the track successfully in propelling mode. I should also add the caveat that I have not yet tested the train through points/switches. I expect they should go through forwards safely but will probably derail if going through backwards due to the "bunching" issue.

One of the questions that pops up here on a fairly regular basis concerns the maximum distance between axles without binding or derailment becoming an issue. On a couple of occasions I have mentioned the Castering Effect and it's possible application to the LEGO railway world. Having raised the possibility I thought I should find out for myself what use it might be and to see whether I could harness this effect and see what it might be made to do. And so I set about building myself some prototype vehicles and a test track and got to work. This is the test vehicle I designed. It's a bit of a "parts bin special" but it does the trick. In the light of the lessons learned the test vehicle design was changed slightly and then retested. There is still much more work to be done with more prototypes and testing, but I'm hoping to come out with some sort of working MOC at the end of this process. I appreciate that there is rarely anything new under the sun and that I'm probably just replicating someone else's work. Comments welcomed as always. **EDIT** By the way, those black boxes are video links.

I used the power bogie design pioneered by @Space2310 for my 4-wide TRAXX loco, which has a 5 stud wheelbase. This seems to cope with the standard LEGO narrow gauge curves quite well, as the video on my Flickr feed shows. Whether or not the wheelbase could be successfully extended I couldn't say.

@scruffulous Funny you should mention that, but I was just in the middle of knocking up something along those very lines on LDD.

@SwengX Oh blimey!! And I thought it was only us Brits who were crazy enough to come up with a self-propelled 4-wheel railcar. If the idea is to run that as a single car and not as part of a larger consist then even castoring is unlikely to help, because at least the leading axle will need to be lead through a curve in order to impart steering impetus. @Toastie SwengX doesn't appear to have set up his MOC to take advantage of castoring because it appears that his axle pivot is directly on top of the axle itself. For that you need to move the pivot point away from the axle, in the manner of the supermarket trolley wheel. Apart from that there are few similarities between the dynamics of trains and supermarket trolleys, I agree. I'm beginning to think that I might have to build a proof-of-concept prototype to test this out.

Forgive my ignorance, but is there really any need for having centring springs at all? Wouldn't the natural castoring effect of having the pivot point for the axle mounted inboard of the axle itself not produce the desired result, the same as for the wheels on a supermarket shopping trolley? Naturally you may need to limit the amount of articulation to prevent the wheels falling between the rails, especially on longer cars, but the steering impetus can be imparted to the leading axle of each car through the coupling to the car in front while the trailing axle will simply follow on behind obeying the laws of physics. Has anyone tried this?

3-wide...? Damn!! Now that’s a challenge. What a cute little fella. Excellent work on capturing the shape and look of the original.

Thanks go to the guys from BMR for all their hard work organising an excellent competition. I had a lot of fun and enjoyed all the entries immensely. Congratulations to everyone who entered. I can’t wait for OcTRAINber to come around again.

That’s an epic suspension bridge. I bet you all held your breath the first time a train went across it. Ha ha!! Thanks for sharing the video. You guys have some lovely trains.

How large or powerful would the magnets need to be simply to align the coupler heads? I mean, all they’d need to do is pull the coupler faces towards each other just before they make physical contact, and provided that the heads swing freely enough I can’t imagine that the force required to do this would be very large. I was just idly musing while looking at the proposed design whether you could add two small magnets, one each side of the knuckle. With the poles correctly arranged they *should* attract each other as the coupler heads approach each other aligning them so that they are square to each other and removing the need for them to self-centre. I know this is likely to detract slightly from the prototypical look of the design, but it might help to make them more functional. Thoughts...?

A lot of real world couplers have structures that help to align the coupler heads as they come together. For example, Tightlock couplers (which are a development of the Buckeye knuckle coupler) have a “nose and pocket” arrangement that assist with alignment. Whether such measures can be replicated at LEGO scales and on LEGO curves is another question altogether. One thing I would advocate though is that any coupler design should be capable of self-centring so that they can at least operate correctly when used on straight track. Rather than considering the Type E design DOA, have you considered other alternative designs? The Scharfenburg coupler could be an option with a sprung catch, as could the conceptually similar BSI coupler. **EDIT** On reflection... I’ll be honest and say that I think the existing LEGO magnet couplers are probably the best solution we have at present, although that’s not to say that they couldn’t be improved upon. A free-swinging coupler that can self-align, even on tight curves and on a variety of different stock types, and make a reasonably strong coupling, all without the need for springs, latches or other mechanical aids, seems to be a good starting point. I wonder if all that’s really needed is a development along the existing theme, perhaps using stronger neodymium magnets and perhaps adding a weak sprung catch that can be easily made and broken, would be a good solution. Such a development might also have the advantage of being backwards compatible with the existing coupling standard. As a railwayman with a dozen years experience I can see that there are real-world solutions that have applications for LEGO train construction, but equally I can appreciate that some real-world technologies could not easily be applied without introducing further complications. I can certainly see a use for a mechanical coupler such as the one you propose, but I don’t see it as versatile or user-friendly enough to be a universal replacement for the LEGO magnetic couplers. At the end of the day it all comes down to how well they work. For long semi-permanently coupled trains I can definitely see a use, but for frequent coupling and uncoupling it could be more problematic. However, you will only know for certain by making some and trying them out in a variety of scenarios, and I’m interested to know too.

Hi Glenn, Thanks for the update. The time and energy that you guys are putting into this contest are greatly appreciated.

I suspect we've set them a real challenge to judge our entries. I certainly wouldn't want that job. That said, it would be nice to know if there is some date or other they're working towards for announcing the results. It would be ironic if it took as long for the results to be announced as we were given to design, build and present our entries. Ha ha!!

@Tenderlok That's a very interesting prototype, but please can you post some photos of your model for comparison purposes. Thanks.

@LEGO Train 12 Volts Thank you, but I'm not sure it ever will get built. It's already more than 3600 parts, and the part count is still slowly creeping up. Unless either the manufacturer or operator wish to offer me a handsome commission I think this will remain a virtual build only.

That is good news. I was worried that I’d built a model of something soon to be extinct. I only hope the refurb the trains will get will sort out all the problems that they experienced during their time in the Low Countries. Thanks for posting the link. Are the proposed routes on which they are likely to be used prone to heavy snowfall...?

Holy smokes!! How did this end up on the Flickr Explore page?

Thank you gentlemen. That’s most kind.