Great idea, I may join for 30 minutes a day in the Doodles thread.
For ink sketches, I always find they are much better if I start drawing the rough perspective lines and composition with a 9H pencil.
You can then do the expressive ‘draw through’ strokes of the sketch by just following the pencil.
For the rest this is mostly a matter of refining your line work by doing. It also helps with sharpness if you consciously break down the details into sketch elements as you would in Solidworks while sketching (“spline-fillet-arc-spline-fillet-line-fillet-line”) instead of drawing it as one shape.
The more your mind is with the shapes the better they will come out on paper.
To be honest, besides them needing to be a bit more precise and expressive, I think these are pretty good sketches.
Definitely much more than just getting by from the studio work I see on average.
The typical time spent on such a sketch sheet is 1 hour for a designer, including some basic color indications.
So you can get faster too, keep in mind what you want to communicate and what is essential to the sheet.
Keep posting!