I was wondering what size chain do you use for your drive. Team 663 has used 32 size, but I have noticed teams use considerably smaller. Do teams with smaller chains encounter many problems?
Also, how much tension is really on the chain?
32? Do you mean 35?
The two types of chain I’ve seen used in FIRST are #25 and #35. It all comes down to personal preference, I think. #25 is strong enough for most drive systems, and when you factor in the weight loss from sprockets and chain, it becomes very appealing.
My team has used #35 the last 5 years or so since we have a ton of it, and it gives us a big strength safety zone
my fault, I know it was 30 something
#25 ANSI chain has a working load of 140lbs
#35 ANSI chain is 480lbs
then next after that is #40 at 810lbs
So you get a significant increase in strength going from #25 to #35
I think it’s possible with some FIRST bot setups to take #25 past yield
or at least well into the built in safety factor whatever that may be
But I can’t see harming the #35 with a strong drive train under some
shock loads.
I think #40 is just overkill and too much weight.
FIRST provided #35 chain in our kit last year, I think it was 20’.
along with some #35 sprockets. So it’s not a bad idea to stick with
#35 just in case you want to use them.
Check out this thread:
hmm #25 vs #35. We have used both sizes of chain. for the last two years we have used the #35, and have had no problems with it. Because teams are employing stronger multi-motor drivetrain configurations. the larger chain can take bigger shock loads, and not even break a sweat. the smaller lighter chain works, but with the #35 there is no question of it breaking. We tried the #35 composite chain, and it was expensive, and weak, we broke it in ten seconds. I think that with the stronger gear boxes, you should beef up the entire drive train. the #35 chain works well, and offers a sense of security that atleast you know the chain won’t be failing you. I had a much nicer post typed out, but I timed out, and I just dont ave the long drawen out - more technical explenation.
I know this is posted elsewhere, but I will post it again.
We use #25 chain all the time in our drive systems. Last year we used #35 chain to connect our transmissions to our back wheels. We then connected our front and back wheels with #25 chain. That way if your #25 chain breaks due to high loads or some other reason you will still be able to drive around. Of course only with 3 wheel drive… that is if you do a 4 wheel drive robot.
EXAMPLE:
Last year when one of our gears connecting the front and back wheels shattered into many pieces, we were still able to climb and drive around the field.
Just remember it is better to have #25 chain break than your transmissions!
I think most teams that have trouble with #25 chain, don’t actually exceed it’s tensile load strength, but in actuality just throw it off the sprockets.
The major difference I’ve seen between #35 and #25 chain, is that #35 just holds up better in cases of misallginment.
It is very forgiving under abuse of any kind, and in my experience, you want as much forgiveness as possible when the chips are down.
$.02
John
Good point John, I had a note close to that in my original post, but it took me so long to write it, my session timed out, and I had to log in again, loosing my post. Needless to say I was a little frusterated.
Woburn in 2003 was an exception–the 25 chains, though tensioned correctly, were used with too small a drive sprocket (18 tooth, if I remember correctly), and too powerful a gearbox (3 motors each, approx. 2.8 HP total, before efficiency losses). The individual links stretched to failure, probably as they were passing around the drive sprocket. It’s unknown whether the rigid idlers further stressed the chain.
For information on the proper use of chain at various speeds and horsepowers, with various sprockets, consult the Tsubaki Chain catalogue, specifically pages A-1 through A-7 (Acrobat pages 12-18) of Section 1: Drive Chains. There’s a chart which will allow you to determine whether the design you’re working with needs 25 or #35 chain.
Let’s just say that the 2003 Woburn drivetrain performed exactly as Tsubaki predicted…we had doubled the acceptable maximum power for the chain. 13 broken chains later, it was decided that the next robot would probably need to use #35.
The chains for Blizzard V never broke, but the same can’t be said about the gearbox… 
I think we would all rather have a chain break then the gear box, although if everything is designed right, a key should break first before too much damage is caused to any key hard to replace component, or at least you would hope. I like to build everything strong enough, and robust enough to not worry, but the drill motor gear boxes where my weak link last season, but we powered along, and did a lot of pushing just with he cims, sometimes I would swear the drills had to be helping out the cims, but then I’d get it back in the pits, and sure enough, we would have wrecked another set of drill gb’s. (plastic lock rings)
ok, I would like to thank all for the replies. Now, I read the thread that Steve W suggested and was wondering if anything came out of the tread design that Adam Y. was designing.
I think in that thread, Adam was talking about an attachment chain style tank drive. Though I’m not sure about his particular results, I KNOW FIRST has seen this design many times in the past…
The Technokats - Team 45 made attachment chain treads famous.
(Some refer to them as “Techno-tracks”)
Refer to their 1999, 2001, 2002robot designs.
Many other teams have used similar systems as well.
Wildstang 2002used a chain tread in their drop down tank.
(Why choose between a swerve and a tank drive? Just do both! Crazy!)
These “mean metal treads” aren’t seen in FIRST anymore due to limitations on metal interacting with the playingfield. Some teams have modifiedtheir chain treads with non-metal cleats. (I believe the pictures I link to, are from team 885’s 2003 robot.)
Many teams now prefer timing beltstyle treads.
I believe (from what I’ve heard from 45) when using a chain drive, difficulty often arises in keeping the chains from throwing off their driving sprockets. Side loads during turning will cause the chains to walk off their sprockets despite tensioning. When one uses timing belts, this problem still arises, but can be overcome by using timing beltswith some form of built in, central allignment.
The merits of using a track drive, and of using various drivetrain types has been WELL discussed. Feel free to search previous discussions of these topics for more information.
It all boils down to simple physics!
Hope this helps,
John