[retsibsi]

I've seen a lot of bikes (and ridden thousands of kilometres), but when I had reason to draw a bike I felt the need to look up some photos to refresh my memory. I'm pretty sure I would have made some basic structural mistakes without that visual reference.

If you find this inconceivable, IMO you're assuming other people's minds work more similarly to yours than they actually do!

In my case (not aphantasic, but I think my visual imagination is significantly weaker than average), the information just didn't seem to be filed in full detail. The image was weak, as are most of my mental images, and I guess I had never paid that much attention to the concept (i.e. how the parts of the bike fit together as a whole; when I had had to pay attention, it had been to specific things like how the brakes work, how to reattach the chain, etc.), so it was all a bit of a muddle.

[jiggawatts]

Did you see the pictures in the link? The chain was going between the front and back wheel! The pedals were where the seat goes! Basically, a bunch of nonsense. There are chat-bots now that can do better.

I couldn't draw a detailed 3D technical drawing of a derailleur, but I can draw a sketch of a bicycle without needing a photo reference!