Hi all,
I would like to know your thoughts on using #25 chain vs #35 chain for 6 inch size wheels and if you’ve had any experiences breaking #25 chain using 6 inch wheels. I am not sure how to analyze this without making a chassis with each type of chain so I’m hoping someone will have some insight on this topic. Thanks!
The sprocket has more to do with breaking chains than the wheel size. You generally don’t want large differences in sprocket sizes. 25 chain is easier to break, but if you’re careful and line them up properly, you shouldn’t experience a problem.
I have not used 25 chain before so I can’t speak on that behalf but the reason my team uses #35 and don’t really risk the 25 is due to the drivetrain being the most important part of your robot. No drivetrain, no scoring (minus a few teams from 2015 and 469 in 2010, but besides that) so even though it may add a pound, maybe 2 at very most, I believe it’s worth it to have a rock solid drivetrain you don’t need to worry about chain tension or chain breaking.
If you use large sprockets #25 can work, but #35 with any sprocket is a lot safer.
We ran #25 in 2016 with 8 inch wheels, aiming for high torque low speed. Because we didn’t have good spacing we threw some chains, but I don’t recall breaking any. We ran 16 teeth on the gearbox and 32 on the wheels; larger would have been better.
Note that we used a Dark Soul chain tool (Vex now has a similar tool for chain) which does not require master links - I absolutely endorse using this type of tool to splice chain. Spliced chain is stronger, and does not have any parts that stick out and tend to catch things. Order a few spare pins for the chain tool, because we’ve had several shear, especially when used by those who haven’t gotten the hang of it yet.
Are 18t sprockets with #25 chain too small for 6inch wheels? We are direct driving the middle wheels and then connecting 18:18 to the front and back.
That setup works just fine. 1678 has used 25 chain with 18t sprockets with various different wheel sizes, without major issues. Just make sure you check the chain often. Use #25H chain if you can, as it is stronger. Also, Chain-Saver the drivetrain a couple times every competition.
Wha’chu talkin’ 'bout, Willis?
A decade of experience with 25 chain… and we’ll not use 35 again. Once you know how to.engineer it you start worrying about weight, then you never look at 35 again unless you’ve got an application that must have the increase in strength.
I love how in 971’s recent video releases they said they’re only doing #35 chain for now on. Thought it was funny…
Worth pointing out 971’s preference for #35 chain is due to the stiffness, not the strength. They use very advanced controls, and need the stiffness to be able to do what they want with the robot. For most teams, #35 chain is overkill in terms of strength and controlability, especially on drivetrains. In the same vein, 971 also make custom sized interference fit hex shafts to reduce slop in their mechanisms, and belts on the drivetain.
There are definitely places to use #35 chain on a robot, but using #35 all the time is just added weight and size for most teams.
We used #25 chain in 2016 with 8" pnuematic wheels and 16 tooth sprockets. The reason we used such small sprockets was we did a West Coast drive with chain in tube. There was very little clearance but it worked. We had only one chain failure from a chain that kept catching a pop rivet (fasteners not recommended sticking inside the tube (versa chassis 1x2) We did two district and one district championship with this. We use the dark soul tool to make chains. This year we are using wider 1.5x2 tube. We have also used #25 chain for the lifts on our 2007 and 2011 robots.
If you have the weight and space use #35…but #25 works almost as well but use it carefully.
We have been using both #25 and #35 chain for many years.
When setup correctly and maintained they both work very well.
In a drive train we stick to #35 now.
We stopped using #25 in the drive train after 2014… We were using 3CIM transmissions and the chain stretches easier and requires more diligence on the re-tensioning or replacing.
Many scooters and go carts run on #25 so they are easily up to the task.
The tire size really isn’t as much of a concern in FRC as the amount of chain you have interfacing on the sprocket…
Keep it at half the sprocket and make sure you have a way to tension and check it before each match and it will work fine.
Just might need small adjustments and keep a few spare lengths (already cut) to swap if they get bad…
Good luck,
Aloha!
Sorry, just wanted to correct this. Properly tensioned and with plenty of wrap on both sides (120 degrees minimum) there is absolutely nothing wrong with a large sprocket reduction, as long as the small sprocket isn’t too small. This has been done by hundreds of teams over many years, and is generally the preferred way to power an arm for example.
Yes, 1678 exclusively uses 25 VEX chain which is stronger than the typical chain. It’s not sold as “#25H” chain, but I can assure you the stuff is not a regular size and may as well be considered #25H for your purposes. In 2016 we use 6 inch pneumatic wheels and 6 inch Colson wheels with 18T sprockets, worked well all season.
Thanks! We’ve just used white lithium grease in the past, and put some rags around the turns on the first run. This sounds easier and cleaner.
#25 is plenty strong for FRC drive chains.
The larger size of #35 makes it more tolerant to poor alignment and tension.
So, generally, if your using hand tools then #35. If you have milling machines then #25.
If you have a clean and tidy room then your a #25 type of person.
#25 can be easier to design with because each link is 1/4 inch. Helps when your doing the math in your head. And don’t do the math in your head.
Where can I find 6 inch colson wheels? I have been looking for them and I can’t find them. Only option I’ve seen is buying some directly from Colson which isn’t ideal since they don’t have hex bores.
Thanks for all the replies everyone! it has been more than helpful