Can't finish drivetrain?

[aeniug2]

Originally Posted by y-aji

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

Buy.... A.... half link?........ I think you should seriously consider getting at least 5-10 if you can... remember, the chains will change over time...

[EricH]

Originally Posted by y-aji

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?

No, not quite. And here's why:

First, you have to account for any belly pans--say a piece of plywood placed in the middle of the frame. That alone will significantly increase torsional rigidity even with a section of outer frame "missing".

Second, you can always build an arch or something similar over the gap in the frame. In fact, if you have not current plans to do so, I would encourage you to come up with a way to do that. http://www.chiefdelphi.com/media/photos/23377 has a pretty good example of what I'm talking about--that yellow bar in the low front that everything seems to mount to (and actually, that robot had that bar on both ends--it's just that the other one end had plywood in the area as well). Note that that particular robot has a wider gap than is legal to have this year--back then, bumpers were optional.

You can still have plenty of structural integrity and attachment area. It's just a matter of knowing how to put back what you took away by cutting out that frame section.

[FRC3883FRC]

I would check the sprockets on the wheels themselves. On our robot the sprockets that come in the kit don’t always match perfectly. So when rotating the wheels there will be a tight spot and a lose spot. I would try to rotate the wheels to see if the sprockets are in perfect alignment. I just did our chains yesterday and I fought the chain on to the robot (not an easy task). Hope this helps.

[DavidGitz]

Originally Posted by aeniug2

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.

We use this chain-tensioner from Mcmaster-Carr: 7320K5

It works a lot better (and safer!) than the 2 screwdriver method.

[Phyrxes]

#35 chain disclaimer!

1. Take one small set of needle nose vice grips that will fit between the two sides of #35 chain.

2. Grind pockets into the upper and lower jaws so that they will fit around rollers.

One of these lives in our "emergency" Drive Train box, it often lets one person hold a chain together and insert a master link with minimal problem.

[c.shu]

One thing that teams should be careful of when putting chain on their robot is to not OVER tighten it. After doing chain for my team for a few years I found its okay to have just a little bit of slack in it. You will avoid a lot of broken chains if you do this. You should not have to force the two ends of the chain together. Then you can use the mounting bolts for your gearbox to tighten it down a little if need be.

[the man]

Broken chain or masterlinks? We have never broken a chain. The master links fell out after getting smashed in to while tiped on our side.

[Matt C]

Originally Posted by squirrel

we use half links a lot.

We seem to use half links a lot as well . . along with master links . . . I've seen 3-4 on a single loop of chain.

[R3P0]

Originally Posted by aeniug2

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

We buy 10 links, 10 half links and 10 add a links for whatever size chain we end up using as part of our Pit supplies.

Dooooo eeeeeht!

Also your spacer on the one wheel definitely looks like it is off and to the right. A warped chassis will always cause this issue if everything else is plumb. Get all four chains on the wheels and drives sprockets and bolt the wheels in one by one. TRy this set up for a six wheel drive. Note chains locations.

http://www.chiefdelphi.com/forums/at...4&d=1326676219

[aeniug2]

Originally Posted by Phyrxes

#35 chain disclaimer!

1. Take one small set of needle nose vice grips that will fit between the two sides of #35 chain.

2. Grind pockets into the upper and lower jaws so that they will fit around rollers.

One of these lives in our "emergency" Drive Train box, it often lets one person hold a chain together and insert a master link with minimal problem.

That, my friend, is an excellent idea. I might just have to try it...

[nitneylion452]

Originally Posted by Matt C

We seem to use half links a lot as well . . along with master links . . . I've seen 3-4 on a single loop of chain.

I was working on some chain the other day. I was helping a student get chain on a sprocket since he had never used master links before. As I was attempting to show him how to put on a master link, I noticed something rather funny: the student broke the chain (i.e. removed the pin. It was an old loop from last year) right next to a master link. I couldn't help but laugh.

[kinganu123]

this actually looks like the problem our freshies had with the kitbot our freshies are making...
try flipping around the spacers (they are different lengths) that surround the wheel. It SHOULD make the sprockets parallel with the sprocket on the gearbox

[y-aji]

Thanks guys!

We got it all figured out. As suggested by Kevin Sevcik, the holes in the c channel weren't perfectly center and we didn't think to check that. Upon inspection, we had 2 offending peices of c channel that we just flipped around and everything fit like a dream.

Thanks again!

[2544HCRC]

Late the the posting I knw but.. I agree that chains should be a little slack. If they are stretched like rubber bands you are putting torques on everything. It's far easier to throw a chain or break a chain if something gets slightly out of wack and it will if chains are too tight. If sprockets are inline Chains can be pretty darn loose without a problem. Avoid really small sprockets if possible, they don't handle loose chain as well as a slightly larger sprocket.

I always roll the chain up onto a sprocket and put the master link in on a sprocket. It's easy and it works every time. Half links are invaluable and I'm always happy if I can get one in on a new chain. I know that after the chain settles in and stretches I will be removing the link.

Practice keeping your fingers out of the sprockets. I NEVER stick my hands in between a sprocket and chain loop. I see kids do this all the time and it scares me. If you have to work on something, remove the chain or keep your fingers on the outside of the loop. Worst case you loose a finger but a much more common situation is where I've seen students really pinch themselves on a chain when the robot moved or a wheel rolled on an unpowered machine.