It is amazing what this guy has built over the years. I can also tell you it was very interesting being the flag man at the end of the track for him on day two.
Actually it is an Allison engine that used to be used in airplanes and I believe some tanks if I remember correctly. I think it took him about 15sec to travel 300ft and he was taking it easy.
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I don't think I have ever ran backwards for 30ft that fast in my life.