Hi Audrey - I replayed Episode One this morning to see if I could reproduce the difficulty getting on the Tripodon. It turns out that you cannot, as long as either guard is alive. (If you visit the city gates before you get the compass, there are two guards there, if you wait until the last moment to go there, there is only one - the other one is guarding a different location.)
Anyhow, the Tripodon will not respond while his owner, the guard is there. You must kill the guard. The most efficient way, though not very sporting, is to become invisible and shoot him in the back with the wrist jadgar. You can get a couple of shots in before he turns around and shoots back, and it only takes three shots to deharmonize him.