This is the second of my mobile outdoor rowing exercise machines. It has brakes on both rear wheels. It breaks down to a 48" overall length to fit in the trunk of your car. If you want to build your own, I have drawings available. You can email me at mursinna28@san.rr.com and I will answer any questions you might have. My first machine can be seen on "Rowing machine, outdoor, mobile". The speed is only a function of how fast and hard you pull on the cable. This unit gives one a great workout for the arms, legs and abs. If you would like more info, you can email me at rmursinn@san.rr.com.