Couple of options you have to achieve what you want:

1 Set router 2 up so that it doesn't do address translation. Make router 2 work as a hub/switch only.

or

2 remove router 2 and plug everything into router 1

It all depends on what your aim is. I dont understand why you would want to put router 2 where it is. It adds additional costs to your network without adding benefits that I can think of, given that you want all the computers to be on the same segment.

If you don't have enough ports for all the systems to connect to then a hub/ switch would be a cheper alternative. If you want to secure the network on router 1 then allowing them to be on the same network defeats that purpose if you dont add any other protection in.