This reminds me of the flintbow from the Ultimate Equipment Guide II, but this is definitely way more detailed and interesting. Players always want to know how these things work. Well done. Go to Comment
A common mistake when writing adventures set in deserts is to assume that the climate is too ferociously hot to wear armor. Historically, most battles in deserts involved troops dressed in protective armor. Although they would have been miserable during the hottest part of the day or the hottest part of the year, desert weather isn't intolerably hot 24/7.