Re: pic: Prototype 6WD
 

That's asking a lot from some teams (though I doubt that 188 isn't up to the task). Across the three teams I've worked with, it's always been #35 chain for various reasons (paranoia, the free ten feet in the kit, doubt over our abilities to reach the necessary precision for #25, lack of need to try). I'd want to try it on a test robot before relying on it for competition, just to make sure our old tricks are adequate.

Re: pic: Prototype 6WD
 

Some of us out there have converted from chain to belts and have nothing but positive things to say about our experience...just different strokes for different folks.:)

Re: pic: Prototype 6WD
 

Even with poor alignment, 25 chain is very forgiving. On our practice robot last year there were several times when our chain was misaligned and we would run 4, 5, 6 matches without noticing and it never broke. In fact we've never broke 25 chain, ever.

Here's our history with 25 chain:

2006 (drivetrain)
2007 (drivetrain and lift on both competition and practice robots)
2008 (drivetrain and ball grabber on both competition and practice robots)
2009 (drivetrain and dumper/pickup on both competition and practice robots)

Summary: 15 applications over 7 robots.

I think the biggest secret is keeping just enough tension on the chain.

I'm not saying that you shouldn't use 35 chain or gears or belts, but 25 chain isn't a finicky as some people lead it on to be. In the end, every solution had its pros and cons, the right solution is the one that best suites your design goals still fits within your team's abilities.

Re: pic: Prototype 6WD
 

I totally agree, #25 chain is more than adequate. We have used #25 chain in our Drivetrains for years and never had any issues (providing that everything is assembled correctly). #25 chain will not break until you put over 900 lbs of tension on it. It is pretty much impossible to apply this level of force in a FIRST robot drivetrain.

The 3 main issues I see team have with #25 chain are:
1. Alignment - If you don't line up your sprockets you will have issues
2. Frame Rigidity - If your frame is not bolted together tightly, things will come out of alignment when torque is applied.
3. Workmanship - I see lots of teams who mangle #25 chain when removing links. This can create a stiff spot in the chain where it will not bend properly. This will make it more likely to derail. It is much harder to do this to #35.

So basically, the advantage of #35 is that it allows you to be sloppier in your design and fabrication. If you pay close attention to these details, you will never have a problem with #25 chain.

Re: pic: Prototype 6WD
 

This is a big benefit for many teams....maybe not yours...but still.....

Re: pic: Prototype 6WD
 

This is part of what I think of as fault tolerance. You can stack a lot of errors a #35 chain will still work.

Re: pic: Prototype 6WD
 

Fault tolerance is good, but there can be several pounds difference between #25 and #35 chain in a drive. As far as I've been on 973, running a west coast drive with #25 chain, we've yet to throw a chain. I know many other teams have similar successes with #25 chain.

To me, it's a no brainer, if you can allign it right..... which isn't very difficult, it's an easy choice.

Re: pic: Prototype 6WD
 

We've never broken a chain since I've been on 254.

We've never thrown a chain either.

The one time we "lost" a chain was when we got hit so hard a sprocket broke, at which point the chain derailed.

It didn't even break. It stayed on the drive sprocket in the gearbox and somehow just kept spinning without completely destroying the gearbox.

I can't ever imagine using #35 chain in a drive again. The added size of the same tooth count #35 sprocket makes every gearbox, mechanism, etc larger, not to mention the additional weight of the chain and sprockets.

I don't believe that there's any team that's not capable of properly aligning and tensioning #25 chain if they put a little thought and planning into it, regardless of their manufacturing resources.

Re: pic: Prototype 6WD
 

You're probably right Cory, but there are a lot of teams who's effort might be better spent working on the game playing parts of the robot....

#35 works, it's easy, it's cheap, it's in the kit, etc.

Re: pic: Prototype 6WD
 

Same Here, Madtown has been using #25 chain after there rookie year back in 2004. We have never tossed chain during Competition. Its a pretty simple concept, line up the chain and tighten the set screw on the sprocket.

Re: pic: Prototype 6WD
 

I really like the use of your slotted bumper mounts.

Re: pic: Prototype 6WD
 

Everything looks very sound. One trick I learned from Simbotic's drivetrain back in 2008 is, if you line up the pneumatic cylinders on the shifters, you can eliminate a cylinder by linking both to an end of a new one with double the stroke.