We happen to have a couple of LEGO PowerMiners* sets. Some of them can be combined to produce more advanced machines, one just has to download the instructions from lego website.
In our case we wanted to build the Aero Shredder from the 8960 and 8958 sets.
However to my unpleasant surprise I found out that Lego not only discontinued the PowerMiners series - they also erased all documentation as well as user forums related to it.
Upset with this disgusting behavior I sent the lego support people a polite but urging e-mail and got a link for the instructions. So if you're looking for it, here it is.
(In case the link goes dead drop me an e-mail and I'll upload the pdf somewhere)
* This series is a slight variation on the discovery of America. Courageous scientists discover an underground world rich on resources (crystals). However the natives (rock monsters) stand in the way, so the holocaust begins.