paper: Cyber Blue 234 Belt vs Chain Technical Evaluation

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Cyber Blue 234 Belt vs Chain Technical Evaluation
by: Chris Fultz

This is the presentation pack from Cyber Blues presentation on a Belt vs Chain evaluation for FRC robot drive systems, fromthe Championship Forums.

In the fall of 2008, Cyber Blue completed a technical evaluation of Belt Drive vs. Chain Drive for FRC Robots. The team used Design of Experiments Methodology to create an unbiased evaluation process to compare the two systems.

This is the presentation package used at the 2009 Championship Forums.

234 Belt vs Chain CHP Forum.pdf (159 KB)

This is the presentation package from Team 234’s Presentation at the Championship Forums on “Belt vs. Chain” for FRC drive systems.
The presentation was given by students Jamie Cartwright, Miranda Goelz, Phil Welsh and Mentor Collin Fultz.

Interesting… I wonder if this all would hold true with 25 chain… I would def. consider belts next year, but they are a bit harder to assemble and take up a bit more space… Cool presentation!

our plan is to repeat the testing and duplicate the parameters, only use #25 chain and 9 mm belt. That should give us a 4 way comparison.

Very nice presentation and good information. Well done!

Interesting! and could you try V belts too?

We have looked at using toothed belts, and #25 chain, and have always used #35 because it’s easy/available/inexpensive/forgiving. The extra weight is generally down low on the robot which makes it not very important, and the extra efficiency of belt seems to be negligible.

I guess as your team gets better at designing and building robots, the importance of these paramaters shifts.

Testing v belts would be a waste of time. A team tried v-belts in the past and the results were very poor. V belts require high tension to function correctly thus reducing efficiency greatly over timing belt or chain.

Think about it this way. We made one change between Purdue and Atlanta that made us 8% faster. That means in the time we could go 40 feet, we could now go about 43 - 44 feet. It doesnt sound like much, until you realize that is equal to a robot or a trailer.

So you did end up switching to timing belt on the real robot? I am planning testing timing belts this year either in a swerve drivetrain or in our standard 6wd. I am very curious to see how it holds up to the torque of a 2 speed transmission.

We made a change between Arizona and Atlanta that made us go about 30% faster…we bought some sprockets from Small Parts Inc for under $10 each, and brought a short piece of #35 chain and a couple extra master links with us. I hate to think of what it would have taken to make this change if we had used a toothed belt drive.

If the robot is right at the edge of optimum performance (not the case this year), then the efficiency is important. Most years it does make some difference, but careful drive ratio selection might be more important. The wide availability of different tooth count #35 sprockets, and the ease of changing the chain length, seem to me to be a much bigger advantage, especially for teams like ours that don’t have enough experience to get it right the first time.

My point is that there seem to be a lot of considerations that you left out, which may not be important to your team, but make a big difference to many other teams.

Still, it’s great that you did the research, and showed us that there is advantage to be gained by careful experimentation. It would be neat to see more belts on robots next year. The experiments with smaller chain and belts will also be very helpful, and if more teams see the benefits, they will increase demand for the parts, and hopefully it will become even easier to make these changes.

Did you get a chance to look at 1717’s robot?

I definitely looked at there robot and I have many pictures saved of there robot. I have also talked with them about timing belt a little bit. IMO timing belt is far more effective than chain. The past 2 years, we have run #25 chain without incident and without any tensioning devices. While initially this would seem ok, the chain did still stretch. With kevlar reinforced belt, this problem would be eliminated. Additionally, changing belt for many designs would be as simple as changing wheels, which is something that many teams do throughout there regionals due to using conveyor tread. In our drivetrain this year it would have been almost as easy to replace belt as chain and certainly in the future it could be made even easier. Timing pulleys, especially polycarbonate ones, are much lighter than sprockets and cheaper as well. While I have had an enjoyable experience with #25 chain, I am also eager to test out timing belt for myself.

so what does your team use?

we tend to just use bike chain for drivetrain

and we use pulley mechanisms with belt drive

Due to the low friction between the wheels and the flooring this year, we used #25 chain.