This wouldn't really be a woodworking question but I need to know for future reference. I'm doing a school project where my team and I are making a car out of cardboard, glue and two 3/4in x 40in dowels. So I would just like to know the strength of the dowels because they would most likely be used as the axles of the car (Where the wheels attach). Our "Driver" per se, weighs about 120 pounds so he's a skinny guy, but I just want to know if they have they strength to support his weight. The pressure would be mostly situated on the middle of the dowel so that is where my concern stems from. If anyone who knows what they're doing then that would be a big help because I know nothing of this. Thank you for your help!
The centre of the axle is the worst place a point load. The best place to apply it is just inside the 2 wheels. If the structure can't transfer the driver's weight out to those points, then build a truss unit that rests on top of the axle to help distribute the load without too much flex. You can also build a box beam or a triangle beam, much like a tower crane.
If the driver is the only major load, try to have the weight shared evenly by both axles.