Chain vs. Belts?!?
 

Hey everyone. I'm from team 240 T.E.M.P.E.S.T.

The past 2 years we have used chain everywhere. There was one thing that happened, we had to fix the chain a lot more than we liked too. I know this could be due to poor alignment, etc. but next year we plan on using belts.

What are your thoughts on Chains? Belts?

Thanks, Drew

Re: Chain vs. Belts?!?
 

This is a topic that is discussed quite often.

There is a good white paper written by team 234 which evaluates the power transmission methods:

https://www.chiefdelphi.com/media/papers/2216

Re: Chain vs. Belts?!?
 

Thank you! I'll check it out

Re: Chain vs. Belts?!?
 

Its worth mentioning that if the issue was alignment whether you are using chains, belts or interlocking plastic monkeys the issue wont be solved.

If you are using #25 chain and there are alignment issues switching to #35 could help but really the best thing to do is fix the alignment.

If your issue has to do with master links I would buy a dark soul chain remover.

iirc belts actually are more sensitive to being out of alignment so switching to belts is only going to make things worse.

Re: Chain vs. Belts?!?
 

After seeing what 5172 did with poly cord this year, im excited to use it more in the future. Belts don't stretch which is nice, but you have to design around belt size more so than you do with chain. Personally I'm sick of chain, but that's because it cost me a ton of time during Ri3D. It's more difficult to align a chain than it is a belt in my experience.

You can't go wrong either way if you do it correctly. I would suggest looking into poly cord belts as an option.

Re: Chain vs. Belts?!?
 

For the uninformed, what did 5172 do with polycord?

Re: Chain vs. Belts?!?
 

It is important to consider the advantages of both based on specific applications.
Pros of Chain:

• Sprockets can be more compact (Slimmer than pulleys.)
• Chain can be broken to allow for easy servicing.
• Chain, #35 in particular, can support higher load than belts.
• Sprockets can be found in COTS solutions in more sizes than belts.

Cons of Chain:

• Chain, particularly #35 chain, can be heavier than belts.
• Chain can stretch over time (Chain should be fine for at least 2 regionals if properly tensioner or set for an exact c-c distance).
• Chain comes in links, it can be a PAIN to deal with chain if you don't use a whole number of links.
• Chain probably shouldn't be run at higher rpms. I've seen a team explode #25 chain by running it at 5K RPM.

Pros of Belts:

• Belts come in many sizes. (You may need to buy from sources other than VEX or AndyMark, however.
• Belts can be much lighter than chain if used in applications within their load range. (Provided you use larger pulleys, you should be able to push their load rating in FRC applications.)
• Belts are much quieter than chain.
• Belts do not stretch as much as chains when properly loaded.
• A broken belt will not shatter (from what I've seen at least!). Flying belt material is safer than flying steel or aluminum.

Cons of Belts:

• Belts require pulleys than can be much wider than sprockets.
• Belts are more likely to stretch or break if misaligned or if their C-C distance is inaccurate. (Belts in Drivetrains and many other FRC applications are already being pushed beyond what they're rated for; you will see catastrophic results much easier than chain that isn't being pushed well beyond what it is loaded for.)
• Belts require a higher accuracy to properly use in comparison to chains. (I've been told ~.003in is optimal).

This document is really helpful for finding information on belts: https://www.gates.com/~/media/files/...ion-manual.pdf

If you want additional information, post here or look for Travis or Austin Schuh. I learned most of this information by reading posts from those two and they are very experienced with using both belts and chains on their robots.

Re: Chain vs. Belts?!?
 

They used it everywhere! Most of the mechanisms on their robot were powered by polycord. It was cool to look at, and obviously functional.

Re: Chain vs. Belts?!?
 

A quick skim of the 20 pages of search results for chain vs belt gave me these:

https://www.chiefdelphi.com/forums/s...=Chain+vs+belt

https://www.chiefdelphi.com/forums/s...=Chain+vs+belt

https://www.chiefdelphi.com/forums/s...=Chain+vs+belt

Re: Chain vs. Belts?!?
 

My FTC team is looking at it as complete replacement for gears and chain.

Re: Chain vs. Belts?!?
 

I wouldn't trust it in high torque situations such as drivetrains, as I haven't worked with it yet. If anybody can speak to polycord's power transfer ability before slipping that'd be awesome. I can't wait to test the stuff in many different applications.

Re: Chain vs. Belts?!?
 

It could just come down to what your team already has or is familiar with. CD has no consensus on whether belts or chains are better. So, I just use chains because that's what the team already has.

Re: Chain vs. Belts?!?
 

Whatever you choose, make sure you have good alignment. We had a regional last year where we broke about nine belts because of poor/weird alignment. We also had to disassemble the third stage of our gearboxes for at least six of those belts, so we basically got so sick of replacing belts that we went with #25 chain this year. But again, alignment.

Also, be sure you can tension your chain because it will stretch.

Re: Chain vs. Belts?!?
 

I like belts for everything other than drivetrain. Why drivetrain? Because for a given strength, chain is more compact than belts, and with the 4-cim loads in the drivetrain compactness is a high priority for me. That's a point that's often overlooked in the belts vs. chain debate.
It's also possible to run chain in tube in a 2x1 easily and reliably, whereas doing the same with belt is a lot harder.
Belts run quieter than chains, so for anything else- from shooters to intake to arms- I prefer them. In the specific case of arms, the belt will likely slip before the gears start shearing teeth (in theory), so I get a bit of a safety factor there.

Re: Chain vs. Belts?!?
 

We tried using it this year for driving our intake. Our intake was designed to pinch the ball between the wheels and a churro and we could not spin the ball out. The polycord would just slip. We were attempting to use it more like a traditional belt, which was probably our mistake, and only had 2 cords. However, in 2015 we used it for a conveyor belt and it worked fine. I think the main dlfference is we had a lot more cords (4 or 5) and it was a lower torque application.

Re: Chain vs. Belts?!?
 

QFT.

If alignment or tolerance is what is causing you problems now, switching to belts will make the situation much worse.

Re: Chain vs. Belts?!?
 

We successfully used a Polycord drive system in the past. One of the center wheels was direct driven by a custom super shifter based gearbox. The other wheels are all direct driven by Polycord using custom pulleys directly attached to the wheels (Dead Axles). This is the best picture I could find of the drive train. (This is one of our signature Round Robots)

Attachment 20906

Re: Chain vs. Belts?!?
 

Out of curiosity, what year was it? Also, did you have any problems with the polycord slipping in shoving matches or other high-torque situations?

Re: Chain vs. Belts?!?
 

There's no single correct answer (despite what some CDers would say) of what you should use. It all depends on your situation. If you need the weight, you may need to go with belt. If it's going to be a giant PITA to change a belt, you may need to go with a chain.

In my opinion, the "default" choice, when nothing really matters, you just need a reliable drivetrain, is to go with #35. It doesn't break, it's dead simple, it's forgiving, but is heavy. However, the "nothing really matters" portion is rarely the case and each situation needs to be handled on a case-by-case basis. What is important is knowing the tradeoffs (which have been outlined pretty well already in this thread). I wouldn't, however, deviate from the "default" of #35 chain without a good reason. The good reason may be weight related or space related, but you should at least have one.

Re: Chain vs. Belts?!?
 

Agreed. My team has learned the hard way to just use #35. The way I like to think about it is that #35 is complete overkill for FRC, which is why its the best option for FRC. Since it is overkill, it is a lot harder to mess up and will just work, which is exactly what you want for a drive train. The question you should be asking whenever you use chain should be why should I use #25, not why should I use #35.

Re: Chain vs. Belts?!?
 

Belt and chain weight is the same when you factor in pulleys/sprockets. That being said I 100% agree that #35 is bulltproof and should be used for a "first chassis" sort of deal.

Re: Chain vs. Belts?!?
 

Assuming you are using aluminum pulleys, the pulley/sprocket weight is probably close to a wash. Factor in 35 chain, the chain is a lot heavier.

Polycord will slip given enough torque. That is either a bug or a feature depending on your needs.

Re: Chain vs. Belts?!?
 

That was the 2014 season, Our Jupiter Robot. No real noticeable issues with belt slip.

Here a match from that season with plenty of pushing.
http://www.thebluealliance.com/match/2014pncmp_qm41

Re: Chain vs. Belts?!?
 

Wow, I never would have thought that polycord would work in a year like 2014. I'm impressed.

Re: Chain vs. Belts?!?
 

I was thinking about #25. For #35 nothing beats it in terms of weight. :rolleyes:

EDIT: InFlight, that is a gorgeous robot and a great performance! I can't believe polycord drive worked that well.

Re: Chain vs. Belts?!?
 

Our team has used #35 chain with no master links for the past 3 years. Before that we used belts one year and did some direct drive from the gear boxes before that. Personally i dont see us ever moving away from #35 chain. We have never had a problems with it while i have been on the team, however i think that our first year we did break a few chains dew to improperly installing the master links. Since then we just haven't used master links and it works very well.

Re: Chain vs. Belts?!?
 

How do you avoid using masterlinks? Do you have a #35 chain tool like the Dark Soul one for #25?

Re: Chain vs. Belts?!?
 

This year my team's robot had 8" wheels and 22t sprockets, which stressed #25 chain more than in any of our previous drivetrains, and had zero issues. On the other hand, we broke our #25 intake arm chains multiple times, and in the future we will likely use #35 chain for arm applications. At least for our team, we have found applications for both #25 and #35 chain.

Re: Chain vs. Belts?!?
 

Where would you go about getting a dark soul for #25. Our team needs one.

Re: Chain vs. Belts?!?
 

221 Robotic Systems recommends here.

Re: Chain vs. Belts?!?
 

I bought one from Dave's motors earlier this afternoon and it shipped only a couple hours later. So far they seem to be a good supplier, and they take PayPal which is nice.

Re: Chain vs. Belts?!?
 

Ditto here. I've bought two from DDM. (Get a spare set of pins when you do; I'm not sure how long they last after you know how to use them, but we had one break under first time handling by a student on Saturday.)

A similar tool for #35 is available here. As it happens, I'll be ordering a couple this evening, so I can't make a recommendation.

Edit:

For the record, the Dark Soul tool requires slightly different usage for standard duty vs heavy duty (e.g. Vex, and I believe also AM) chains. The difference between the two is the "plate thickness", that is, the thickness of both the inner and outer plates that run from pin to pin. For heavy duty chain, when removing a pin, it is necessary to go to the point of increased resistance, then about another 1/4 turn. For regular duty chain, doing this will result in the pin being pushed completely out of the outer plate, making it essentially impossible to use that link again, at least by using the DS tool.

Also, take care not to over-tighten on pushing pins into the chain; stop just before the screw pin reaches the outer plate of the chain. Even when doing this, I have found it necessary at times to use a screwdriver of just the right width and a hammer to push the outer plates away so that they do not bind on the inner plates -- especially when using standard-duty link-and-a-halves.

OBTW, does anyone know where to source a heavy duty #25 link-and-a-half?

The order is placed. I'll try to remember to post some info back here in a few weeks. If not, send me a PM around 1 August to remind me!

Edit 2:
On the first tool we ordered (all I've had in hand so far), the pins were driven perfectly by 5/32" allen wrenches. That was already our most-used hand tool*, so I just bought a couple more!

* - I even have one on my non-car key ring - not only for use on robot stuff, but the "crash door hardware" at the school and church both use 5/32" hex keys to place the hardware in and out of "access from outside" mode. I pretty literally never go more than 50' from my house without a 5/32" allen key in my right pocket.

I did notice some online directions for using the Dark Soul tool referencing a millimeter-based tool (4mm, IIRC).

Re: Chain vs. Belts?!?
 

While we do have a few hand held chain breakers, what we use most is a custom press pin we made to mount right to a small bench top arbor that we have. On the face of the press there is a piece of steel with holes drilled to align the chain under the pin and then we just press out one of the pins so it is just in one side of the link. Then remove however links we need to and flip the chain and press the pin back in.

Re: Chain vs. Belts?!?
 

I'd love to hear how these tools perform. I want my team to get away fro Master Links in #35 chain, so just some info about how well it works would be greatly appreciated.

I would be really interested in seeing some pictures of this. This sounds amazing, and a clever piece of engineering.

Re: Chain vs. Belts?!?
 

I will try to get some picture in the next few days. It has done wonders for making chain lengths for us.

Re: Chain vs. Belts?!?
 

We bought that exact chain tool from Amazon for this build season. It works, and it does the job, but the quality is not the best. One of the bolts had a hex socket that was ever so slightly too small, and I had to widen it by pounding the 3/8" hex key in and shaving off a thin layer of metal off the bolt. No other hex key, in mm or inches, was as close to fitting as the 3/8" - which works perfectly fine for the other bolt. I was probably just unlucky, but that's still bad quality.

Re: Chain vs. Belts?!?
 

Both chain and belt are legitimate forms of power transfer and can be used successfully with proper implementation.

My personal preference is chain for low speed high torque applications, such as drive. Chain takes up much less space than an belt with the same strength. IMO chain has more reliability and strength in a smaller package, with less efficiency and more weight than belts.

Belts for high speed low torque application, the gains in efficiency are noticeable over chain. Also, belt for long runs for weight reduction.

The beauty is there is no right or wrong answer, there just has to be consideration for the down selection and performance desired.

Re: Chain vs. Belts?!?
 

We have been using this little guy for years now and it performs very well. It can be a small hassle to get the new pin to line up properly with the holes in the chain as you tighten down the screw, but isn't as bad as installing a masterlink. Like everything, doing it with the chain untensioned is going to make your life easier, but we have had success even with chain lengths that are technically too short for where we are using them.

Re: Chain vs. Belts?!?
 

We have a chain tool that looks just like that Gee Two linked to. I think we bought from the same place some years ago based on CD recommendation. Works great. The guides line up the chain and help to hold it in place. Assembling/breaking chain takes a bit of technique. Easily learned through practice.

We have also found this tool useful for putting master links on chains.

For those considering poly cord for drive train, keep in mind that one wheel per side on Inflight's nicely done robot was direct driven from the gear box which plays into how much torque needs to get transmitted to the other wheels by the poly cord. The pulleys for the poly cord where also large which helps with the force transfer.

Re: Chain vs. Belts?!?
 

I can attest that that tool is approximately 5-10 times faster to use than the one-size-fits-all spring-loaded chain breaker.

Re: Chain vs. Belts?!?
 

Which tool? This links to the "chain tools" page on McMaster

Re: Chain vs. Belts?!?
 

My apologies. This tool
Which should be a roller style chain holder. It holds the chain together so you are not trying to put the master link in with the chain in tension.

Re: Chain vs. Belts?!?
 

Thanks for the recommendations! My mentor asked me to find what tools/equipment We needed to look at buying for next year, and at around $15, I think that will be the first tool on the list.

Re: Chain vs. Belts?!?
 

I would get both that and a dark soul because you will most likely use both #25 and #35 and trust me, if you use it just once, you will feel you got your money's worth.

Chain vs. Belts?!?
 

If you are looking to buy a #25 chain breaker this thread (https://www.chiefdelphi.com/forums/s...d.php?t=143362) has some good suggestions. I would absolutely stay away from one of those "one size fits all" spring loaded models. We have one and it is absolute garbage. Instead of pushing the pin out, it just bends and destroys the chain side plates. We were able to mess with it enough to break the chain for our shooter this year but it was a nightmare.

Re: Chain vs. Belts?!?
 

I'll try and slip the DarkSoul tool in there, but most of the build members on my team are unwilling to try out #25 chain, due to strength and the fact that we have some #35 sprockets left over. I'm working on turning them to the DarkSide (bad joke, couldn't resist) and run #25 on at least manipulators and such, but we'll see how it goes.

Re: Chain vs. Belts?!?
 

There are plenty of applications where #25 is more than strong enough (like by magnitudes) and the size and weight saving are very useful.

I understand the concerns with #25, although we ran #25 on our shooter/intake and had zero issues, even with a master link. For context we ran 2 22T sprockets from VexPro driven by a MiniCIM with a 4:1 VersaPlanatary. In my opinion, it's a useful option to have where #35 would be overkill.

Re: Chain vs. Belts?!?
 

I certainly understand; I designed our 2016 bot with #25 chain in mind for all of the sub-assemblies except drive, but the rest of the team was worried about it, so we went with #35. We had experience with #35 from 2015, and we already had the tools we needed, so it was the quicker option at the time. By the time Kickoff for 2017 rolls around, I hope to have the younger members trained and the shop outfitted so they feel comfortable using both and can determine which is better for different situations.

Re: Chain vs. Belts?!?
 

Defaulting to #35 is a good first step, but you should then evaluate on a use by use basis whether you should switch to #25. There are some applications that a really obvious, like for spinning your intake wheels or rotating a 1/2 pound hood subject to no load on a hooded shooter. Then there are things that are more questionable, mostly different size arms. You could try doing the math (and add a safety factor if you want) or just play it safe with those applications. Or, if you expect weight to be an issue, design the system to work with both chain sizes, so if #25 fails, you can use #35. Overall, I would say #35 is better for drive and large arms, while #25 is better for spinning wheels, small arms, and miscellaneous small purposes.

Re: Chain vs. Belts?!?
 

A 4mm metric allen key is recommended( what it is designed for) which is handy for us being an Australian team and using a lot of metric( M5 and M6) hardware. In reality 5/32 inch is 3.97mm so there isn't exactly a big difference, probably not worth worrying about.

Re: Chain vs. Belts?!?
 

We often confuse 4mm and 5/32". The Dark Soul chain tool is one of the fortunate and rare cases where using metric or imperial has no noticeable effect.
0.03mm is ~0.001" so it's well within the tolerance on the hex and on allen keys.

Re: Chain vs. Belts?!?
 

Would you recommend this tool for #35 over a roller chain breaker (which we currently use)?

Re: Chain vs. Belts?!?
 

I'm not the best person to answer this because I was just getting advice about the same part earlier, but I believe the distinct advantage with the tool GeeTwo and others were referring to is that you can use it to break and reform the chain. The threaded rods can be used to push the pins out or push the pins back in to create continuous chain loops without master links.

Re: Chain vs. Belts?!?
 

I fully agree. After a few hours working with the Dark Soul tool, I've decided to add another line to my auto-signature.

Edit: On the off chance that I ever remove this from my auto-signature: Friends don't let friends use master links.

Re: Chain vs. Belts?!?
 

We have 3 dark souls and 3 of these tools in the shop and they are both beautiful. I highly recommend both of them. They are easy to use and with a little practice they break and assemble chain beautifully.

ONE VERY IMPORTANT NOTE!!! When breaking the chain with these tools DO NOT FULLY REMOVE THE PIN!! This makes re-assembling it nearly impossible. Its better to push it out until it is stuck in just the last thin piece of the chain. This keeps it aligned and in place to push back and re assemble when needed.

Re: Chain vs. Belts?!?
 

This is anot extremely common questions on CD and TBH this thread is TL;DR.

My personal take on belt verses chain is dependent on where it is on the bot. If it is on the drive train I use Center to Center chain #25 and forget about it. In my experience the stretch is small enough that it has no noticeable impact on the bots performance.

Everywhere else I use belts and put them in tub.

Re: Chain vs. Belts?!?
 

The chains vs. belt discussion is a common topic that the OP probably could have searched for and gotten the same results more quickly, but the last page and a half of this thread actually turned into a helpful (for me at least) discussion about tools for chain. Your info about the #25 chain is still helpful though; it's always good to know of teams that used a less common method with success.

Never underestimate a CD thread's ability to get derailed.

EDIT- Oh, and there's a brief excursion of people discussing polycord as an alternative to belts and chain. The more derailment, the better!

Re: Chain vs. Belts?!?
 

I know for the past page and a half we have been talking about tools for chain. But back to the belts... What sizes would you recommend. I know 100% that the sizes may vary between years and robots. But I'm not sure on the standard belt sizes due to the inexperience with the topic.

Thanks, Drew

Ps. This is very helpful and I appreciate it!

Re: Chain vs. Belts?!?
 

The pulleys that VEX and AM sell are 5mm pitch HTD, so that's what most FRC teams use. Usually 9mm or 15mm wide. You can also run GT2 tooth profile belts on HTD pulleys.

Re: Chain vs. Belts?!?
 

If you use a GT2 profile with HTD pulleys, it's not supposed to add any benefit, so generally speaking it's better to just stick with HTD for availability purposes.
The lower limit (and it's a sketchy one) for 5mm pitch 9mm wide HTD belt pulleys is 24t apparently for a typical year (read: not this year). I believe that 36t is safer than using 24t, especially if it's your first time. If you use 15mm wide belts I'm not sure, but 24t is supposed to be safe with those.
You would be better served asking "Chris is me" because I'm just parroting what he says at this point. :P A quick search on google should turn up some relevant threads about belt sizes.

Re: Chain vs. Belts?!?
 

We ran belt our second year (2013 Ultimate Ascent) for the lighter-duty portion of our climber, and for our frisbee feeder (or more precisely, frisbee arrestor), and in our fourth year (2015 Recycle Rush) for the drive system exactly according to the AM-14U2 plans. IIRC, all were stock 15 tpi belt.

Obviously an edit:
Yes, RR is RR is RR. I also fixed this above...

Re: Chain vs. Belts?!?
 

I think you may have your games mixed up a bit.

Re: Chain vs. Belts?!?
 

Others who have run custom drivetrains with belt would be able to tell you better, but the numbers Sam posted are great to start with. Though if you need to run smaller sprockets than what is recommended, you can always incorporate idler sprockets/bearings into your belt run to increase the amount of wrap you have on your pulleys. This adds weight and complexity, but it is an option.

Re: Chain vs. Belts?!?
 

Sorry it took a bit longer than expected to get the pics but here they are. This is the chain break that we made to break #35 chain so that we could get away from using master links. The chain is aligned in the line of of holes on the bottom while a pin is pressed down with the handle. It works great for us and is really fast as it does not use any other tools at all.

Re: Chain vs. Belts?!?
 

The links don't work right now. It looks like they are links to email attachments. Can you upload them to google drive or similar and share them that way?

Re: Chain vs. Belts?!?
 

Fixed it, the pics are visible now.

Re: Chain vs. Belts?!?
 

How do you assemble chain onto the robot? Or do you always create a loop of known length and wrap it around un-tensioned sprockets?

Re: Chain vs. Belts?!?
 

We always just create known length loops like you said. With how much #35 stretches on something like a drive train through out a season, we find that we always need chain tensioners anyway so it really is not to big a deal.

Re: Chain vs. Belts?!?
 

Belt vs chain, in my 4 years, relatively short compared to many of these people, I have not seen a lot of difference if the shafts the belt/chain is on are attached to the same plate, when you start getting joints in between it gets a little hairy with belts, but we have only broken a chain once, and that was on our t-shirt shooter while driving in the grass and all its drive is 25 chain, our 2012 robot, a very similar design, uses 35 chain from the gearbox to the center axle, then 25 from the center axle to the end axles and we have never had any problems. On the belt side, the past 3 years we have used belts in the drive and never experienced any issues, our 2014 bot is still running all original parts, except the wheels. 2014 and 2015 we used the standard kit base and 2016 we used a modified version of the Rhino Track system. (custom fit to our Breckoflex tracks) We have used poly cord in the past as well, the last time was 2012, but the stuff is quite useful for intakes, our 2006 robot uses a crazy pulley system and a bunch of poly cord to run the intake and spiral ball storage system off one motor. Poly cord can't take too much torque, but sometimes that is a good thing and the cord is not near as picky about alignment as long as you have deep pulleys and if needed you can even make it turn on multiple planes.

Re: Chain vs. Belts?!?
 

Some thoughts, from my personal experience:

Belts are more sensitive to C-C distance. Chain is more sensitive to alignment. I've never once, in my many years of FRC, seen a timing belt jump off a pulley (exclusively using flanged pulleys, admittedly, has helped with this). I've seen chain jump off not-quite-aligned sprockets more times than I can count. However, I've seen plenty of not-quite-tight-enough belts ratchet, whereas chain will only ratchet if it's basically falling-off-loose.

Complicating this fact for chain is the tendency to stretch, which is not a problem with belt. Once a belt is properly set up, you can forget about it. Chain, not so much.

The upshot of this is that chains will (almost) always require either tensioners or adjustability at one end of the run. On the flip side, if you don't have the machining capability do to precise C-C distances, so will belt.

Belts are much, much quieter, which is a bigger benefit than you'd think.

Chain can be put on in-place without moving a sprocket, via. masterlink. Belts cannot.

Chains can transfer a much higher maximum load, given the size of belts used in FRC. If you're limited in your pulley diameter or belt width, or if you just have a mechanism with whopping forces involved, this can matter.

This isn't rigorous at all (so take it with a grain of salt), but belts seem to be less-prone to bizarre one-off undiagnosable failures than chain. A fair number of times I've seen chain fall off drives with no visible faults, with no hint of the cause and no subsequent failures despite nothing being changed. I have seen a grand total of one belt failure in my entire time in FRC.

My teams tend to use belts, because we value reliability and belts basically never fail.

On #25 vs. #35 chain, my advice is to avoid the former unless you are certain of your team's machining precision. As I mentioned, #35 chain is already more sensitive to mis-aligned sprockets than belts - but #25 chain is *far* more sensitive than #35 chain, still. If you cannot align the sprockets extremely well, it will fail. My teams, which machine almost exclusively with a chopsaw and a drillpress, have abandoned #25 chain for this reason, and we do not regret it one bit.

Re: Chain vs. Belts?!?
 

+1. #25 has only worked well for us when alignment was due to COTS parts, rather than our own machining. Then again, I wish we did more machining with a chop saw and a drill press; I am fighting an uphill battle against the hand drill and the Dremel tool.

Re: Chain vs. Belts?!?
 

I know for a fact that my team has published a paper evaluation this very topic. If you'd like, I can post a link to it!

Re: Chain vs. Belts?!?
 

You can find it here, scroll down until you find the "Belts vs Chains presentation" PDF.

Re: Chain vs. Belts?!?
 

Chains suck if you dont know how to instal them or get that finicky half link in however used correctly i think its fine. As for belts, a good belt is better in my opinion "but belts might stretch" people argue. Youre using the thing for 6 hours flat out total at most, it doesnt matter in the time span of build and comp unless youre using a multiyear old belt. BELLLTSSSS

Re: Chain vs. Belts?!?
 

For FRC applications belts shouldn't stretch. Chains will stretch though.

Re: Chain vs. Belts?!?
 

I've heard that multiple times, but I've always wondered what "FRC applications" means. After all, one team's robot might go through tons of matches and hours of practices. Another team's robot might go through just one competition with minimal practice time. Doesn't the difference in runtime affect how much chains/belts stretch?

Re: Chain vs. Belts?!?
 

For chains definitely. Belts just don't really stretch under normal loads of an FRC robot.

Re: Chain vs. Belts?!?
 

Because of the fiberglass tensile members in the belts we use, there isn't much 'stretch' in the belt at all, regardless of loading. Basically, if you're putting enough load on the belt to stretch it, it's about to snap, and cause a complete failure. Belts do not stretch appreciably over time. Theoretically, the teeth of the belt will deflect under shock loading because the tensile members do not support the teeth themselves, but that doesn't really affect wear and tear, that just increases the likelihood of ratcheting when you're overloading the belt's hold on the pulley.

Re: Chain vs. Belts?!?
 

Yes, but even given the variation in runtime between different FRC robots, the runtimes of all FRC robots are on a scale that's orders-of-magnitude smaller than that of these parts in actual industry, so "FRC applications" remains a very meaningful distinction.

Re: Chain vs. Belts?!?
 

How does one account for stretch? Tensioners like delrin rods on bolts?

Re: Chain vs. Belts?!?
 

Basically having tensioners at some point, yes. There's a lot of ways to do it, including using idler sprockets, bare tensioners like you describe, or moving the bearing blocks farther away from each other via a Vex cam.
I heard from someone on 1296 that they used preloaded chain to account for chain wear-in so that they could run direct C-C without any change in tension over the course of a season.

Re: Chain vs. Belts?!?
 

All sorts of different ways to tension chain. You can find nice ones on McMaster but are expensive, but if you don't over tension you can get away with Delrin of some sort.

Be careful to not over tension. Cost 229 a chance at a regional win this year.