Originally Posted by nova

each d motor has i think 3 pounds of thrust or is it 7. Ither way youd need alot of them. Infact me and a friend who was in to rocketry put 3 large coffee cans packed with d motors. All we managed to do was make him wreck. All the engines went off but it just managed to make him fall over sideways. The bike was a diamond back bmx that was under 10 pounds. Total rockets on it was around 40 or 50 the bike on its side with all the engines pushing it didnt even move a foot.

If you look at even th biggest model rockets they have at most a cluster of 5 engines. Simply put thats about the largest number you can use and have any stability in flight.