Gears or chain and sprockets?

What are the advantages/disadvantages of gears or chain and sprockets. I cant really tell any difference between them except that chains break quite easily.

So, in terms of driving or lifting a heavy manipulator, what are the advantages and disadvantages of both, and which one is better from your investigation?

Well, it might depend on where you want to put your motor. A chain can be many different lengths, whereas gears must go in certain places. Additionally, gears must ride on shafts.

Sanddrag covers the basic issues well.

On the other hand, you can use multiple chains to increase strength.

Don

Using sprockets and chain gives you a wide range of ratios you can use. Also, it is fairly easy to swap sprockets to change the ratio during a competition, but gears require quite a bit of redesigning of the robot. The downside with chain is of course its weakness, but as mentioned above you can make it stronger by using multiple chains.

There are more options in terms of ratios for sprockets than gears, but the chain is considerably weaker than the teeth on gears (although they are far from impervious as well). You can double-up on both chains or gears if they stress is too high though, and some have used tank treads for transmission of power over long distances (such as FVC 40 and 1281). Gears tend to take a bit more meticulous designing to get them to fit properly than chains do (especially in FVC), and gears cannot have anything between the origin of power and the output of power, aside of the gears (while a chain can go around an object or spacer).

From my many experimentations I have found that gears are more reliable in high tourqe situations and some drivetrains. Whereas chain is good in tight areas so you can mount the motor else where and transmit power over a distance. Also I like to use 6 wheel drives alot and usually I have ATLEAST one wheel powered directly from the motor(through gears or direct drive) and then drive the remaining wheels with chain from that shaft and the hope is that if the chain breaks then the robot can still move a little. When you need to use chain in a high stress application it is better to use 2+ chains.

Our team’s experience with using chain and sprocket for drive trains is that it is disasterous. The amount of tension present causes one of two problems. The first is the chains simply snap. This could probably be remedied with doubling up chains. The second scenario that is far more troubling is the chains loosen eventually and so the amount of tension is reduced. When the gears spin the amount of tension on each side of the gears is not equal and so the difference in tension then causes the chain to snap. This seems to happen even when doubling up. Bottom line - if the situation requires high torque or has a lot of stress on it avoid chain and sprockets.

On another note - gears are hardly impervious. I’ve seen them snap, which just confirms my belief they should have made them out of metal. So if there is going to be a lot of stress on the setup, double up all of the gears.

thanks,

after much consideration, our team decided to gear the drive train and use chains/gears for the arm lift

The Vex chain is plenty strong enough, as long as it is tensioned properly. If your chain is too tight or too loose, it will snap much easier. :wink:

FVC 228 (formerly FVC 59) last year used Vex chain for driving their robot, and they did not have any problems with it breaking. Over the course of two competitions (in which they placed 2nd in both) they only broke the chain once, and that was because another robot rode up onto the frame of our team’s robot, and the wheels of the other robot became entangled with the chain on ours.

Here’s a few pictures of their robot: (sorry for their large size)

http://www.team228.org/images/2006/buildseason/weekfour-vex04.jpg

http://www.team228.org/images/2006/nerve/nerve-05.jpg