C&C per req:
Some interesting compositional ideas, but with room for improvement on the technical side. As an aside, it's generally not a good idea to tell people that you especially like the images that you post for critique as that may incline them to be a little less discerning. I however, have no such compunction.
1. A 100 year old barn door can be an interesting subject, and an ideal candidate for a mono coversion, but in this case, there's really not enough of it to give the viewer a sense of what he's looking at. Additionally, the heavy shadow running down the centre is very distracting. As well, I think you may have missed your focus as the wood appears rather soft for the most part. Your mono conversion is well excuted, and your exposure is close, but some work to reduce the highlights in the area middle left wouldn't go amiss.
2. Nice work on the long exposure time. Unfortunately I'm not sure the subject is the most interesting. The main detractor however is that the the "wall" is at least 2/3 - 1 stop under-exposed, making it difficult to discern detail. Make sure you review your images and look at the histogram. A reshoot is definitely in order.
3. Much nicer, but again, somewhat under-exposed. In this case, I would suggest shooting a series of 3 - 4 images decreasing the exposure by 1/3 stop each time.
Just my $00.02 worth - your mileage may vary.
~John