Do an image search for bulldozer or crawler on a flatcar, and you'll get about a thousand results. Most of them pretty useless for those wanting to do it right, rather than the Lionel way (big screw from underneath)
Except this one:
A damaged in transit load costs money, not makes it. A partially dislodged load could not only damage itself and stuff close to the track, it could kill people. The railroads tried to make darn sure that stuff wouldn't move. Things were blocked and braced, then tied down.
The Spec Cast TD-24 is quite a bit larger machine than the TD-18 shown above. When it was introduced in 1947 it was the largest built.. So extra care would have been needed.
And there still should be two more chains on the undercarriage for a crawler of this size.
I also found an Army Transportation Corps training manual with blocking dimensions and illustrations. for securing crates, coils, machinery even aircraft parts. The heavy machine section starts about 1/3 of the way down
http://www.tpub.com/content/railroad/TM-55-2200-001-12/index.htm
Besides, it just looks a lot more realistic tied down than just sitting there
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