[pmangels17]

Sounds like you have a physics problem on your hands. We know torque = r x F, where r is the radius to the point where the force is applied, and F is the applied force.

No matter how you drive the wheels, if you desire a specific speed, the required torque applied to the wheel is a constant. Knowing this, we have a couple options to either reduce force on the chain or increase the maximum force the chain can withstand.

1. Increase the radius of the sprocket. This will reduce the force on the chain, and with a little algebra, you can calculate how much the force will be reduced if you so choose. Additionally, this will give more teeth for the chain to "bite" on, so the potential to put a ton of load on a single link pin is somewhat reduced

2. Upgrade to #35 chain. I say upgrade because if you have the weight for it, #35 chain is a fantastic solution for drivetrains. This will increase the maximum force the chain can withstand, and lessen the chance that the applied force on the chain will exceed the breaking point. This can also help you to lower your center of mass slightly, which, depending on the shape and height of your robot, could be a nice improvement.

3. Combine 1 and 2 by switching to #35 chain and increasing the size of your pulleys. Since you have to buy new sprockets anyway if you switch, why not get the largest radius that will work for you without creating clearance issues? You can decrease the force on the chain and at the same time increase the max allowable force for the chain.

You could also experiment with properly tensioned belts of appropriate width, spacing, sprocket size, etc, but I honestly do not know enough about belts off the top of my head to give a good suggestion for you.

Additionally, like other people have said, you will in any case do well to make sure that everything is properly aligned and tensioned without any half links. I know that when my team did some seriously tough drives during my high school years, we didn't even use master links, let alone half links. If you invest in a good chain tool, you can make complete loops of chain for your drive, and by removing master links you can remove another point of failure from your system, provided you properly use the tool to reassemble the chain.

EDIT: While I was typing this, some other people beat me to the punch. But nonetheless, if you can do it, #35 chain is awesome.