Hawkwind have always maintained that "Silver Machine" was about Robert Calvert's bike (but I've never really believed it)
According to el Wiki...
The lyrics are a send-up of space travel, inspired by the Alfred Jarry essay How to Construct a Time Machine which Calvert interpreted as a description of how to build a bicycle:
"I read this essay by Alfred Jarrey called, "How to Construct a Time Machine", and I noticed something which I don't think anyone else has thought of because I've never seen any criticism of the piece to suggest this. I seemed to suss out immediately that what he was describing was his bicycle. He did have that turn of mind. He was the kind of bloke who'd think it was a good joke to write this very informed sounding piece, full of really good physics (and it has got some proper physics in it), describing how to build a time machine, which is actually about how to build a bicycle, buried under this smoke-screen of physics that sounds authentic. Jarrey got into doing this thing called 'Petaphysics', which is a sort of French joke science. A lot of notable French intellectuals formed an academy around the basic idea of coming up with theories to explain the exceptions to the Laws of the Universe, people like Ionesco the playwright. The College of Metaphysics. I thought it was a great idea for a song. At that time there were a lot of songs about space travel, and it was the time when NASA was actually, really doing it. They'd put a man on the moon and were planning to put parking lots and hamburger stalls and everything up there. I thought that it was about time to come up with a song that actually sent this all up, which was 'Silver Machine'. 'Silver Machine' was just to say, I've got a silver bicycle, and nobody got it. I didn't think they would. I thought that what they would think we were singing about some sort of cosmic space travel machine. I did actually have a silver racing bike when I was a boy. I've got one now, in fact." - Robert Calvert
That's rather marvellous.
Sadly I've just googled the lyrics (which I never bothered to listen to - are Hawkwind lyrics ever important?) and it's just fun doggerel. Could be about anything. Shirley
(It's still a nice story - perhaps I should read Jarrey's essay ... )