Hello beck! Overall you've done a pretty good job, though there are still a few things I want to comment on:

On the construction you've done a great job at constructing both the initial forms of the wheels and the smaller forms within them. It would have been nice to see more orientations of wheels since you pretty much drew all of them on the same angle, though that's understandable since you probably just had that angle on the ellipse guide. Nevertheless remember you can still practice some of them freehanding, so keep that in mind specially on lesson 7.

About the textures, you are also doing a good job overall focusing on drawing only cast shadows but a few things:

-It's a bit hard since I don't have access to the references, but for example on the silhouette of this wheel you have a shadow that gets outside the wheel, but you didn't change the silhouette. If that's the case then make sure you pay attention to the reference as much as you can. Silhouette is the most important part that helps to convey the textures, so it's super important to do your best on them. Example

-Second thing is that your cast shadows sometimes get a little bit rough such as here. To make sure this doesn't happen you can approach your shadows like this, first drawing the outline carefully, and then filling it in .

-And third and last is that I think you are drawing with both a fineliner and a ballpoint. Using a fineliner or a brushpen is fine for filling the shadows (like on the thingy I just mentioned), but you shouldn't mix two different pens on the same drawing outside of that. Here's an example on your work.

So! Overall you've done a good job so I'll mark this as complete. Remember to ask any question you might have and good luck on lesson 7, you're almost finished!