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Here I will give some tips how to build heavy duty tracks for models like excavators or crawler cranes.
Read first about the importance of the track tension, then about different track shoes and finally see how to build track frames.
Perhaps the most important thing you have to know when building heavy duty tracks with LEGO Technic chain links is the matter with the tension. As you can see in the first image, always build tracks that are under a high tension. You know when the tension is strong enough when it is not easy to close the chain links in a circle.
Although in real life the tracks are not under such a tension, your models won't work properly, if they are heavy and you try to move them on carpet. It then can happen that the gears jump some teeth when the resistance of the floor is too big.
Another thing is the speed. Better build them a bit slower but then you will be able to mount over obstacles more easily.
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The standard LEGO Technic models feature just one chain per side. For heavier models this is often not enough. Narrow crawlers look not very good on a big excavator or are not sufficient to distribute the heavy weight of a crawler crane to the ground.
A solution to this problem is to add a second or even a third chain on both sides of the crawler chassis. If you just need a slightly wider track shoe than the standard one, you can add a 1' by 4' tile on every second chain link. Another variant is to connect two chain links side by side with a 1' by 6' or even a wider plate. The picture shows another variant which I used in my P&H mining shovel. Two chain links are connected with a 1' by 8' plate which is connected to two 1' by 2' plates to make it even a bit wider and to make it loke like they were sloped at the ends.
The numbers above the different drawings show the area which touches the floor for the lenght of two chain links. Two standard chain links have an area of 123 square millimeter while a 1' by 4' tile has an area of 250 square millimeters. Therefore you've got twice the area of a standard chain. The solution I used on my P&H just has an area of 151 square millimeter because only the studs of the plates touch the ground. Using tiles would improve this, but normally it plays no role when using the model on a carpet surface.
There's another thing you should know. There are the old chain links which are more brilliant than the newer ones which are somehow flat in color. I recommend to use only the newer ones because on the older ones the plates and tiles will fall off easily.
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An important thing when building heavy models are the track frames. They have to support the weight and direct it into the ground. One thing is to make the area which touches the ground as big as possible, but the other thing is to make sure that the weight is directed properly into the chains.
Because there are just 40 teeth on the biggest gear from LEGO, I normally use 16 teeth gears for the rollers. The 24 teeth gears are too big, compared to the ones with 40 teeth. With the smaller gears it is possible to create more points where the weight of the model is directed into the chain. But there's a problem when using 16 and 40 teeth gears. The outer gear circles should be on the same line. Otherwise the big gears at the ends of the track frames don't direct forces into the chains and from there into the ground. Or just the big gears support the weight and the small ones are just for decoration.
The picture on the left shows a solution how to solve this problem. By using 1' x 1' x 1' and 1' x 2' x 1' Technic bricks it is possible that both, the big with 40 and the small gear with 16 theeth touch the ground.