Three Dogs & Two Sulkies 

Two big dogs = more speed, more distance, more power, more fun.

These are suspension sulkies. Simple sulkies would have done well also.

The brakes are bicycle brakes. The newer Chalo Sulkies have disc brakes. This is probably a sulky with caliper brakes. You are correct the pole (called a forward shaft) keeps the sulky form crashing into the dog when it stops.

some people use tricycles.

This way they can pull 3 times their weight but it looked like a struggle uphill

I can't tell you how to make this. The man in this video makes them for me at my shop for Chalo Sulky. www.chalosulky.com If you use side shafts and the rear of a tricycle and add a seat, you can make a fine sulky.

thanks