Picking Out Roller Chain

[Matt Adams]

And though this is sort of off topic, since the question has already been answered, I'd still just like to throw in my four cents about #25 chain ahead of time.

Originally Posted by Someone Will Say This

"#35 chain is so much heavier than #25, we've used #25 chain for the past 2,000 years and past 8,000 competitions and not once have we had a single strand of chain break EVER, and we've reused the same lengths of chain each year too. It is perfect in all FIRST applications."

Someone is going to say this. It'll be during week 2 of the build season, and a rookie team will ask for advice on chain in these forums. 40 people will reply, many of them like the above.

The truth is that there have been instances where #25 chain has broke on some teams' robots on the last leg of the drive train. Since the forces are relatively the same for about every team (and the only way to reduce this is by having poor traction or big sprockets) it's definitely in the best interest to not cut weight in something as critical as your drive train.

In addition, #25 chain will stretch significantly more over the course of the competition, and misalignment is not fun, as Ken has said. Let me be clear: chain stretching isn't a fun problem! Nobody gives high fives or a does a fancy FIRST dance because of chain stretching.

Originally Posted by Someone Will Say This Too

The Small Parts catalog says #25 chain has an average break load 925 lbs. Since A^2+B^2 = C^2 (or some other exciting formula) there's no way that you can ever break this chain. Look at the math, number cruncher Matt Adams, you're WRONG.

And numerically... I don't understand how or why it happens either, but it does. It's probably a dynamics forces thing. Every year there are teams that have #25 chain break on them. It's an extra couple pounds to ensure NO worries about this problem occur. It's well worth the weight to save on what could be competition altering failures.

So... there I go being blunt with a person that doesn't exist... If you disagree... I'm jealous of the 2 lbs you're saving this year.

My Advice:
#25 chain on the last leg of your drive train - Don't Go There.

My 4 cents,

Matt