There's a real art to doing that stuff. We did some drawing on the archaeology course, and my favourite thing to draw was flint tools. You indicate the clean cleaved surfaces with concentric curves, and the outer rough matrix with stippling. Lots of fun, and very absorbing. I must have a few of them leftover somewhere.
We used a trick to copy real objects, we sat them under a frame and drew on a sheet of clear plastic above it, to get the size and scale right, like tracing a 3D object. You've done well copying, rather than tracing. I find if I draw from life, I start off right but the scale runs away with me a bit and the lines don't meet at the end!
Meanwhile, I went down to Bike Rescue to see if they had any tyres or tubes spare. I wondered whether to walk, or ride, and took the bike in the end. I'm glad I did, coz they had a few bits going begging, which I hung over the handlebars...
I wheeled it home....
Now time for

and a bit of stripping....