Can't finish drivetrain?
 

We are trying to build a wide 4 wheel drive using the kitbot. For some reason even though the chain lengths are the same they fight correctly on one side but on the other the back is too tight by only a little bit to put on. Any ideas why this would be? Pics attached.
Thanks!

Re: Can't finish drivetrain?
 

Try sliding the transmission on the tight side towards the wheel just a bit to put the chain on.

Re: Can't finish drivetrain?
 

Try loosening the bolts attaching the gearbox to the frame, then attach your chain and reattach the bolts. That should take care of the problem if your lengths are only off by a little bit.

Re: Can't finish drivetrain?
 

On team 2879 putting the chains on is an event in itself...

We are obsessed with perfectly tight chains, and will struggle for hours to achieve that perfection...

One of the methods we use, aside from loosening the gearbox mounting bolts, is to use 2 small (but strong) screwdrivers to pull the 2 ends of the chain together the last little bit, and have a seconds person quickly insert the connector link thingy.

Re: Can't finish drivetrain?
 

Use the sprocket to force to some extent the chains together enough to fit the master link in. Its hard to explain but the teeth on the sprocket can help to get the chain in place.

Re: Can't finish drivetrain?
 

Thank you guys for your answers. Let me give just a little bit more information than was initially given, however, to possibly better explain what we have going on.

It appears to not be a chain length, nor is it a fastening problem. When setting the chains, they are so tight on one side that it bows the wheel inward on the offending side. The other side, using the exact circumference of chain, it is slightly loose. This is true no matter where one slides the gearbox.

I have counted the links, the teeth, and measured the circumference of the chain and found both sides to match each other within a measurable tolerance. However, even though all major variables regarding the chain and distance are the same, we are off by as much as a quarter of an inch when inserting the last screw. I would say it's a squaring issue, however, both the left side and the right side of the drive train have nice strong squares holding them in place.

The only real possibility I can find is that the height of the sprocket is off by 1/8 of an inch or something is wrong with the installation of the gearbox. Can you install a gearbox incorrectly or is it very much so built to prevent any kind of user failure.

The other major factor is, of course, that our robot has an opening in the front of it, we have resolved this temporarily. I'm not sure if the team has confirmed the problem persists from this point.

Re: Can't finish drivetrain?
 

On a sidenote, I love this. We'll start doing this in the future, that's a great idea that would keep the chain in place without needing any specialty equipment. Do you feel it endangers the sprocket? Do you use your active one or do you keep a spare one just for doing this?

Re: Can't finish drivetrain?
 

What exactly do you mean by this?
Is your robot's frame a U shape? And that is somehow a problem?

Re: Can't finish drivetrain?
 

If you find it's really impossible to do, you may want to look into ordering half links. That being said, chains are funky things - it's a possibility that the chain you're using on the other side has been stretched out (as chain tends to do with wear) which would explain the slack. Measure chain for your application; avoid pre-measured chain lengths.

Re: Can't finish drivetrain?
 

Is it just me, or does the left rear wheel look like it's out of alignment with the frame?

Re: Can't finish drivetrain?
 

The axle holes in the C-Channel aren't exactly in the center of the channel. When you assemble everything, this means the holes are closer to the top or bottom of the frame. One or two of the channels on your tight side might be upside down relative to your loose side. The easiest visual check is to look at the one hole that's out of line with the rest. Make sure it's shifted in the same direction on all your channels. The correct direction is probably down, which puts the rest of the holes closer to the top of the frame.

Re: Can't finish drivetrain?
 

My oh my that would do it. We'll check that tomorrow.

@aeniug2: we are making a ball collection facility, so we opened the front side of the drive train chassis up to allow the ball to pass through. So, we cut out the front of the robot. That said, it compromises the integrity of the robot to a moderate degree as you no longer have a full square chassis to build the robot on top of. Does that make any sense?

Re: Can't finish drivetrain?
 

I've never seen the chains end up the same length on both sides of our robots.....there's some mystical force in the universe that makes chains always be the wrong length.

We make the chain to fit the robot, and we use half links a lot.

Re: Can't finish drivetrain?
 

HALF LINKS ARE THE LIFE BLOOD. WITHOUT THEM WE ARE ALL DOOMED... doomed to suffer at the hands of lose chains!

Re: Can't finish drivetrain?
 

Haha, you have no idea how much better that makes me feel. I'll just buy a half link.