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## The Physics of Chariots

Anything about painting, modelling, and beyond.

# The Physics of Chariots

Doombull
Doombull
Joined: Dec 4 2010, 09:31 AM
I've mentioned to a few people that their lovely chariot models offend my sensibilities - not because of poor painting or shoddy glue, but because they just don't work in the real world!

So, here we go: my guide to why chariots need more than just chains...

In the top 2 diagrams, a standard chariot with solid pole. The first one is stationary.

The arrows are forces acting on the chariot - W is its weight, pulling downwards from its centre of gravity. To stop it falling to the centre of the earth there are forces B (the ground) and A (the tuskgors shoulders) "pushing back". It's worth noting that because the pole is rigid we can treat the whole chariot as one body. Also, A+B = W

The second diagram shows the same chariot moving. We now have a pulling force P, and also a force due to friction of the wheels on the ground F. For the chariot to accelerate, P>F. When P drops below F, the chariot slows down. A+B = W still.

Because the chariot above is all one rigid piece, it doesn't matter that the forces don't line up. As long as neither ground nor tuskgor collapse, the chariot stays upright. As long as pole and wheels stay attached, the forces P and F act directly against each other, and the chariot stays upright. You may be able to see where I'm going with this?

Okay, the last 2 diagrams show the ever so popular chariot with chains.

Notice that because the chains are not rigid, there is no force A. This means that B = W. However, unless B and W line up, in other words the centre of gravity of the chariot is exactly above the axle, we have what is called a "moment". This is the physics term for when misaligned forces on an object cause it to move, in this case the chariot topples around its axle and falls forward (the big white arrow).

What if the chariot moves off? Well, the chain goes taut and now provides a pulling force P to act against friction F. There is still no force A! Moreover, note that force P and force F are not lined up. Guess what? This also creates a resultant moment, which also encourages the chariot to topple forward.

Now, it might be argued that a skilful crew could constantly move themselves to adjust the centre of gravity to keep all forces in balance. For example, moving the centre of gravity behind the wheels would create a moment acting against the one created by the pulling force, and if you got it just right everything would stay upright. A bit like surfers constantly adjust their balance perhaps. I would counter that with, "Yeah, right, and fight too?"

At the end of the day, physics says you must either:
a - put a solid pole on so that the warbeasts take some of the strain or
b - add a second axle of wheels to do the same job

Okay, now I've done this I will try not to mention it again...

Doombull
mrtn
Doombull
Joined: Aug 28 2006, 04:53 PM
Very good!
Now, it might be argued that a skilful crew could constantly move themselves to adjust the centre of gravity to keep all forces in balance. For example, moving the centre of gravity behind the wheels would create a moment acting against the one created by the pulling force, and if you got it just right everything would stay upright.
This is exactly what you do when riding a unicycle. No, I wouldn't want to try to ride a unicycle pulled by a mutant pig.
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Doombull
Blackspine
Doombull
Joined: Aug 29 2010, 05:14 PM
Here I was thinking that those slack chains were bogus was me being too much of a nerd.
I salute you.

That being said, it IS a fantasy world. However that does not mean sh*t shouldn't work.

side note, never understood why our ungors just couldn't ride warhounds.
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Doombull
Sherlocko
Doombull
Joined: Mar 12 2006, 03:21 PM
Nice read! It was actually quite intresting.

Is it still the same when you have 4 wheels on the chariot? Shouldn´t that change the centre of gravity or something?

Ah well, anyway, now I have an excuse for constantly rolling 1´s for impact hits. ""How can it hit the enemy when it is stuck to the ground?!".
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Doombull
Saintspirit
Doombull
Joined: Sep 17 2009, 07:04 PM
Blackspine @ Jan 9 2011, 05:40 AM wrote: side note, never understood why our ungors just couldn't ride warhounds.
Would you dare ride something that had better weapon skill than you?

It is good that it has finally been made clear, why you have to do chariots in a special way. Lets make the chariots that way now, especially as we are the only army lucky enough to have core chariots, no matter what kind of lords we have!
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Doombull
Meals
Doombull
Joined: Mar 17 2008, 08:17 PM
While I like that you've gone to all that effort I think you have forgotten something.

Beastmen long ago raided and destroyed Segway HQ in an effort to remove those god awful things from existence. However while there, the Shaman, Melekore the Dark was sent a vision by Tzeentch showing him how useful the technology would be and thus many tortured and killed Segway engineers later, all Beastmen Chariots now employ the Gyrostabilization used in Segways. This means they can just use chains, in an effort to save the trees, as we all know Beastmen are in fact part of Greenpeace. (I mean, seriously, have you seen some of those hippies?? theres something slightly hairy and not quite right about all of them.)

Forum Arguments are like Nascar: Everything goes round and round in pointless circles until you get lucky and there's a fiery explosion.

Doombull
Meals
Doombull
Joined: Mar 17 2008, 08:17 PM
But on a slightly more serious note, if you connect the chain to the bottom of the chariot in your diagram it will provide both Force A and P, which combined with proper weight distribution of the riders to counter the torque created by Force W does allow the Chariot to function correctly at speed.

I agree though that this doesn't quite work if the chariot has to stop.
Forum Arguments are like Nascar: Everything goes round and round in pointless circles until you get lucky and there's a fiery explosion.

 Posts 540
Beastlord
Targhl
Beastlord
Joined: Aug 12 2009, 09:29 PM
I always think, that chain-chariots suck many behind!
GW chariots show us typical way of making a carriage pulled by an animal. Roman chariots had more complex system, that allowed to throw away dead horse (one of two), but apart from those strap system the basic structure of a chariot was pretty much the same.
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Doombull
Chaos, MD
Doombull
Joined: Jun 23 2008, 07:18 PM
The Chariot is crewed by 2 mutant goat-men, and pulled by huge, horned pigs, and you are worried about physics?

Just kidding around. The chain thing always bothered me, but more for the Tuskgors safety than anything. What happens when the tuskgors hit an enemy unit? The momentum of the chariot body carries it into and over the backs of the pigs, and I doubt that Gors are nimble enough to land on their hooves afterward!

More importantly, the animals pulling the chariots are not even attached, the yoke just rests on their shoulders. Except on the Orc chariot, where the pigs are attached by the inside tusk!

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Doombull
snowblizz
Doombull
Joined: Nov 26 2007, 08:35 AM
Chaos, MD @ Jan 9 2011, 04:48 PM wrote:
More importantly, the animals pulling the chariots are not even attached, the yoke just rests on their shoulders. Except on the Orc chariot, where the pigs are attached by the inside tusk!
I'm thinking that's pushing it a bit too far.
After all for obvious reasons almost all bows are modelled sans string.

I'd be willing to assume that there is a ropey harness we are not shown. Same as the bows.

 Posts 43
Gor
alexos
Gor
Joined: Oct 4 2010, 02:50 AM
I have one problem with this, though I don't think it would change much. Gw's chariots don't have their wheels in the center of the chariot, but in the front, meaning that if one was to use chains, it could work.

You see, if the cart was stationary, the cart would actually tilt backwards, meaning that while moving, the cart would tilt forwards once it's standing inertia (F) was overcome by it's momentum, it could possible stay upright.

Just my thoughts.

 Posts 766
Doombull
BeastieBoy
Doombull
Joined: Feb 27 2010, 01:52 AM
Chaos, MD @ Jan 9 2011, 04:48 PM wrote: More importantly, the animals pulling the chariots are not even attached, the yoke just rests on their shoulders. Except on the Orc chariot, where the pigs are attached by the inside tusk!
My problem with the orc model is they try to hard to make it look like it really works, but all the rigging is to much and takes away from the model.

The best rational for all of them ... it's magic Is it so un realistic that your chariot that is rigged up by chains, pulled by mutant pigs, manned by goat men has some sort of magic involved to make it work? I don't run the chains, but I figured we just needed to put this in context.

 Posts 43
Gor
alexos
Gor
Joined: Oct 4 2010, 02:50 AM
Or it's the fact that the Tuskgor's and Gors have some form of bond, like a person gets with a Dogsled team, that allows them to almost communicate without words.

Also, as per my earlier post, I realised that the whole "Wheels in front" thing may work on even, smooth ground, but a chariot with chains going over rocky, snow-covered, forest-covered ground wouldn't be able to manuever, let alone stay upright.

We could always get those models, and replace the Chains with bits of plasticard to resemble wood.

 Posts 406
Gorebull
JensDK
Gorebull
Joined: Jun 14 2010, 07:08 PM
Shadespyre @ Jan 9 2011, 01:24 AM wrote: Okay, now I've done this I will try not to mention it again...
Hehe, good post.

Why oh why is there so much poop in the beastmen fluff?
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Doombull
Chaos, MD
Doombull
Joined: Jun 23 2008, 07:18 PM
snowblizz @ Jan 9 2011, 12:06 PM wrote: I'm thinking that's pushing it a bit too far.
After all for obvious reasons almost all bows are modelled sans string.

I'd be willing to assume that there is a ropey harness we are not shown. Same as the bows.
I understand that, but warhorses have belts attaching the saddles, why not the same on chariot mounts? I'm just nit-picking though, and trying to be a part of the conversation. The chariot I am working on now will have rope added to attach the mounts. My main gripe is the Orc Boar chariot having the tusks attached, but no strap. But you make a good point.

Sorry to derail the thread, back to the chains!

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Various Projects & The Herd of Khraal-Anok the Crowned-One Working towards the P3 Masters Paint Comp(Success!!!) Updated 10/21/14
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