Do they seed the junkyards?

I have suspicions they drop a few items about, e.g propellors when aircraft are involved, elastic bungee when flinging is required, stuff like that. I kinda noticed how out of place some objects seem, on the clockwork cars episode a guy returns from the heap with a nicely folded bag of rubber cord, and in a boating episode there seemed to be an abundance of propellors.


I eat Lions

I saw an episode the other day where the teams had to make regular full-size cars work via remote control. There were two cars in the junkyard that had keys in them and started right up. I can't imagine a car with a working engine being junked like that -- the producers almost certainly placed them there.

In fairness, they would probably have to. In this particular challenge the teams barely had enough time to get the remote control working, and would have had no time to try to get a car with an old rusted engine running.

Absolutely. In fact, I'm sure they consult with the team experts to find out what they plan to build, and what sort of "junk" they'll need to do the job.

There's other stuff that happens off screen, like _somebody_ fabricates those roll cages that magically appear on race day. And I suspect that some painting happens before the "one hour tinkering time". Paint needs time to dry.

[update]
As for the vehicles that start with a key... some cars get junked for failing an MOT test or after collisions when repairs would cost more than the car is worth.

First, it is not a real junkyard. So the producers go about real junkyards looking for stuff that could come in hand.

I imagine for specific challenges they look for certain items.

In the rocket episode they said they planted the rocket motors.

Th is old news; but, for history's sake, for any future readers, the junkyard is seeded with specific things, like working engines, pumps, hydraulic rams, and very specific components for particular challenges. The challenges were designed with 4 particular otions and are given to the team experts. They each pick one of two options and the teams then go with that. There have been instances where the production crew have actually gone out and bought a component and brought it back, to be placed in the junkyard. When the teams are struggling, they are "encouraged" to give it one more look. Also, the time allotted is flexible and they have gone later, to finish up a machine and make it safe. There have also been significant modifications made before the competitions, well in excess of one hour. There have even been manipulations of the competition to favor a team. One of the American competitions had a team that was ignoring the time constraints and took their time putting a dragster together. They didn't finish and the production crew experts and technicians actually completed the job and modified it. It came close to causing legal actions.
The thing is, the mandate of the show is to be educational, not an actual competition. The competition component is there to present scientific and engineering principles in an entertaining way. There is no prize money or anything beyond the trophy. As such, the production team has often structured things to present "better tv." For instance, the rocket expert on the first series, called Buzz, never had that nickname, in his life. Some team members, like Dick Strawbridge and Bowser Munson were brought back because they were popular and footage was designed to showcase them. I have wondered if the Barley Picker's trebuchet wasn't specifically designed to fail, so they could illustrate the pitfalls of structural engineering. Even the team doubted the strength of their materials and the graphics kept emphasizing the structure collapsing under its own weight, which is actually what happened.

You can read a very illuminating behind-the-scenes interview here:

http://www.qwizx.com/jyw/interviews/neal.html

Fortunately, Ah keep mah feathers numbered for just such an emergency!

Obvi