Bicycle Chain vs #25 HD

The biggest issue I see is that bicycle chain has a pitch of .5" which is greater than the .375" of #35 chain and much greater than the .25" of #25 chain. There wouldn’t be many teeth meshing with the chain, at least in a west coast drive. We’ve never done it before but that would be my concern.


No, it’s not worth it.

Between #25HD and #35 you have plenty of FRC specific COTS options that are great.

Using bike chain is solving a non issue at great time expensive.

Save your team’s bandwidth for problems that will make your robot better.


We ran #25HD on our WCD—drive train last year, and didn’t have one issue through over 100 matches.

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Not to nit pick but 4 hours? I hope everyone has the chance to or is at least putting effort toward driving their robot for more than 4 hours (especially now with no bag). No idea how driving 4 hours vs 40 vs 400 impacts the use of used bike parts.

If you use 25 chain and show up to a competition, everyone and their mother can help you with spare parts and alternate options to upgrade and repair.

If you show up to a competition running bike chain, you are completely on your own should anything happen.


The effort needed to use bicycle chain is probably not worth it in terms of competitiveness, but it has a very high coolness factor. Case in point over here. Coolness shouldn’t really matter in competition, but it makes it easier for me to remember certain teams.

Thanks to all for some really good and varied responses. A team that I work with in our region has used bike chain on their drive trains for at least the last several years and had at one point offered to help us do the same, machining the sprockets with us at their shop. They’ve had great success with their robots, and I wanted to weigh how valuable this would be for us to devote resources to. I think we will stick with #25HD for our 2020 robot and off-season work.

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Heading into Championships this year, our competition robot had about 3 hours of runtime on it. The practice robot was closer to 700 460 400? Now I’m not sure. 4 hours is not a bad estimate of how much time a robot will see on the field over a season.

From a mechanical engineering perspective, 4 hours and 40 hours are practically identical specifications. A bicycle chain get can ridden for over 1000 hours before an ordinary bloke will replace it; an old chain that had another 4 hours in it will also be fine to 40.

I find quoting 4 hours for FRC applications helps junior designers be ambitious enough about weight reduction (using 1/16" boxbeam, plastics, rivets, etc) without forgetting that if it’s starting to break while they’re testing it in the lab in the first 30min, something’s gotta change. And reminding us that if it breaks in 8 hours… we can remanufacture it at the same weight.

The only mechanism that might get over 40 hours of operation without design changes & maintenance is the drive.

(400 is unrealistic, my most dedicated students are only in the lab for about 250 hours (and the median is closer to 120 hours), I don’t think a chassis could be driving for more than about 150.)

teach me your secrets

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700 hours? Or 70?

By the end of the season it was broken in every possible way. Aluminum brackets snapped, chassis bent, cable chain flopping uselessly, wires torn and rerun, gears worn down, and every part was loose. My secrets? Trash the thing.

That was napkin math that I did months ago. I just redid it and got 460. Is “mid 3 digits” a more acceptable guess?

Edit: the other assumption I’m making is that it’s being driven for all of the time that the drivers and programmers had it, which is questionable at best. It’s not counting the 4 weeks where the chassis was complete and being used, but the manipulator wasn’t. I don’t know how those two factors balance out.

359 has more blue banners then 973.

We’ve got three that are a little more blue.


But what’s that got to do with the price of tea in China? How many banners have #25 chain won?

359 (as far as I remember) uses bike chain because it’s more readily available in Hawaii, not because it’s better than #25 or #35.


359 doesn’t even use bicycle chain anymore


Last I checked, HoF was the bluest banner. 359 1, 973 0.

Now, I would tend to agree that using bike chain isn’t necessarily worth the effort it takes–but that may depend on if it’s a major undertaking to get 25HD or 35 chain. If it is a major undertaking, then it becomes an engineering tradeoff, and we all know how those go… Doesn’t matter which way you go, somebody complains.


It’s not even summer anymore.


Fall CD >>> Summer CD

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it’s never the wrong season to flex your blue banner count win an argument.


Adam has said it well.
With the COTS options available now, using either 25 or 35 chain is good enough.
Back when we used bike chain, we ran a bike program in the school also. Parts were readily available and we have a mentor that was willing to custom make the sprockets as needed.
I think people also forget that years ago, many teams had issues just creating a drive train. I saw many instances where 25 drive chain failed because teams didnt build drivetrains good enough where they were reliable and tensioned properly at all times.
Suppliers were so much harder to source to get what we needed, plus the cost.

But we certainly learned a lot over the years from Team 254 on WCD, like so many others who have also. Our drivetrain reliability has been pretty good to perfect the last 10 years.