#25 Chain Information

[Cuog]

#25 chain is nice and light, it was still strong enough for us in 05. The problem is that getting more in a hurry is a problem since it isn't used as much in FIRST. Also its smaller and you have to use a different chain breaker and the master links and half links are a royal pain in the...

Other than that if you don't mind the extra effort of using the chain and the lower number of available sprockets you will be happy with its weight savings.

[David Guzman]

I want to thank everyone for their input. We will be making a prototype with 25 chain and seeing how it goes. We are going to most likely use wedge top as our material of contact with the carpet (or w/e it is) and according to what you guys are saying the rubber should spin before the chain breaks. Also our gearboxes are not "over designed" so we rather lose chain than damage the gearbox by having the strong chain (thanks for pointing that out)

I am glad to hear so many good comments about 25 chain because I wasn't sure, but it definitely sounds like worth a try.

It will be great if people who have more information on this chain can keep posting it as it will be helpful to my team and I am sure many others.

David

[ahecht]

Theres another thread with lots of tensioning ideas at http://www.chiefdelphi.com/forums/sh...474#post249653

[Andrew Blair]

I'd like to stress that, as Sanddrag and Travis pointed out, proper alignment and tensioning is crucial. We've used #25 practically forever, and had great success- and failure. #25 is almost entirely suitable as far as FIRST goes in terms of actual chain tension loading. What the motors put out, stopping and starting forces- the chain can handle the tension forces well.

However, #25 will quickly inform you if there is *any* misalignment, angular or lateral, mis-tensioning, or other problems. Last year, even with properly tensioned, aligned, and lightly loaded chain, if we ran over a ball, we crossed our fingers!

Regionals can be a humbling and frustrating experience should you screw up- mechanical reliability is paramount, and badly implemented #25 *will* cause problems there. We broke ~6 chains at Pittsburgh last year, and paid the price. Limping robots are bad robots. However, we tensioned and protected the chains better, and had a great success rate.


As Travis said, you must evaluate each case individually and weigh the consequences. You save huge amounts of weight using #25, but it's very important to design the system well. It will not hold up to running barriers over, or rubbing against a bent frame, or dealing with the mis-alignment caused by that bent frame. But I don't want to get too down on #25; we love it! It saves so much weight, and when properly implemented, won't give you any headaches. Just be careful!

[JoshuaFreier]

One additional bit of information our team has found over the past six years of working with #25 chain is you must do a better job aligning the sprockets then you do with #35. #25 chain is much less forgiving in this regard.

Have Fun,
Joshua

[Kit Gerhart]

We have used #25 chain for years for our 6WD drive train with good reliability. The chain itself is very strong, like 700+ pound breaking strength, and is, of course, much lighter than #35 chain. Also, it allows us to get more reduction between the transmission output and the wheels than is possible with larger chain.

Good alignment is much more important than with #35 chain, and you need to have adequate wrap on smallish sprockets. We use a single chain around a transmission output sprocket, a tensioner, and the three wheel sprockets. Some of our machines have had only about 90 degrees of wrap on a 19 or 20 tooth transmission output sprocket, and the chain needs to be pretty tight or it can slip, not a good thing. The bottom line is that #25 chain will work for most applications on our machines, but everything needs to be more precise than with larger chain, including sprocket alignment, lack of wobble, and lack of runout of the sprockets.