Brain-ache from too much engineering

The last few days I have been doing a lot of thinking.  Not about philosophy, or theology, or relationships, or anything that one might ordinarily spend a lot of time thinking about.  Oh no, I’ve got to be different.  I’ve been thinking about how to create suspension systems in Lego Technic.

Some of you may remember that a while back I spent a week creating a Lego ‘Tumbler’ (from the film Batman Begins), with working suspension and steering.  That was a technical challenge, but I managed to pull it off eventually.  I even made a couple of videos of the progress.  Since then it’s sat quietly on top of the unit in the lounge, silently gathering dust and being generally forgotten.  Until recently I couldn’t bear it any longer, and just had to start thinking about the next version.  Yes, not satisfied with a Lego Tumbler that has working suspension and steering, now I want to put motors in it too.

This presents several problems, however.  The addition of two chunky motors (one for forward/backward motion, one for steering) will add a significant amount of weight to the model, and the suspension is already struggling to cope with the weight as it is.  So I am having to look into better, more effective ways of setting up the suspension, and generally putting the rest of the model on a diet.

At the front of the car, the setup is especially complicated, because it doesn’t use a conventional steering rack.  Just take a look at the original Tumbler and you’ll see just how odd it is.  Squeezing a comparative mechanism into something much smaller is something of a challenge, and although I managed it last time it was a little crude in places, and I’ve been thinking about alternatives.  From looking at various pictures and the bonus DVD I can see that the actual Tumbler uses a system that would actually be pretty much impossible in Lego, simply because of the amount of space it would take up – it works really well, but the Lego components are just too large relative to the wheel to accommodate that approach.  I’ve done a lot of mental experimentation (which is quite difficult without having the Lego in front of you), and pretty much concluded that my previous method will probably still be the most effective, I’ll just have to refine it.

At the back of the car things are equally complicated, though not because the setup itself is difficult.  People have been making cars with suspension for over a hundred years, so it’s not actually something that’s technically complex.  My problem is that Lego likes to be at right angles, not arbitrary angles to cope with pieces moving in an arc.

The problem derives from the combination of needing each wheel to be sprung, preferably independently, whilst still being connected to the engine so as to be powered.  I have done much research on the various different suspension techniques used in real life, and most of them are actually quite difficult to reproduce faithfully in Lego.  The simplest form of rear suspension is the leaf spring, which works really well in lorries and heavy vehicles.  But Lego doesn’t do leaf springs.  It has coils.  I can’t use a proper independent suspension system because I don’t have enough universal joints to connect the wheels to the differential.  A fixed axle is good and simple, but only reliably works in Lego when both wheels are going up and down at the same time – having the wheels going up and down independently causes alignment problems because Lego doesn’t like odd angles.  Trailing arms are out of the question, as are multi-link, A-arm, and MacPherson struts, for much the same reason.

Don’t get me wrong, suspension is possible with Lego – I’ve done it many times before very successfully.  It’s just a matter of choosing the right setup for this particular application, where space and weight are limited.  I may have to resort to some ‘fudging’ or using a limited style of suspension, which would be a shame, but at the moment I’m struggling to see an alternative.  I’m hoping it will all become clearer once I actually get the Lego out and start fiddling.  Ellie is at back at work starting tomorrow, so I’m planning on taking over the lounge each evening next week and see what I can do.  It’ll be shame to take apart the old model, but it needs to be done, and it’ll no doubt be even more satisfying to get a proper motorised version completed!

As with last time, I’ll put photos up at some point to document the progress.  And since the technical aspect is so important, I’ll try to take some close-up photos of the mechanisms for those as geeky as me who like such details.  I’ll also need a good supply of tea to get me through…

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