pic: 114's new tensioner

[Madison]

Originally Posted by Ben Piecuch

We're looking at implementing a cantilevered drive system like this, and am wondering if those bearing blocks are absolutely neccessary. We'd rather just bore the 2"x1" rail to accept a flanged bearing/bushing, and not have to machine a "complex" bearing block. Are teams finding that the 1/8" rail wall isn't strong enough? Or is the support span on the axle too narrow for the applied torque? Or, are teams simply not following the KISS rule and making unneccessary machining for themselves?

If we have to go to a bearing block setup such as this, I do really like the tensioner outlined here. I agree that it can be made simplier, maybe out of just one piece. How does the cross rail mate up this to assembly, and does that connection (bolted or welded?) interfere with any of this?

Thanks,

Bengineer
Team 228

To my knowledge, 195's 2007 chassis was built as your describing -- bearings pressed into 1x2" tube.

We use bearing blocks because I can mill a set and some extras in an hour or so on our mill and they're easy to replace in case of some catastrophic failure. Our mill's travel is only 20", so I can get accurately spaced bearing holes into a frame member in one operation and we're very likely to screw that frame member up on some other way down the line. Bearing blocks minimize the time spent redoing work, I guess.

I wish there were some better, more considerate reason for our process. But, with the time constraints we have, taking baby steps is preferred -- even if they're more complex -- than putting all of our eggs into one very complex, important basket. Of course, I understand the definition of "complex" varies from team to team. We have awesome machining resources, but none of us are great machinists, so we work with what we have.

Originally Posted by spazdemon548

It looks great. I would be concerned with the tension bolt loosening. Instead of using a bolt for tensioning, you cold use a threaded rod with a hex insert at the end for an allen wrench. Then by tapping the end plate on your 2x1 extrusion, you can put another nut on so it would be double nutted.

We used a similar system in the 07 season, and have never had any issues with the bolt backing out or loosening. Doing the other setup is actually more parts, and more machining needed.

Originally Posted by M. Krass

I think this is where you'll end up on the next iteration, Craig. The concept is sound, as I see it, and it's pretty much where I ended up a few weeks ago -- though I'm probably a few iterations farther down the road and I'm interested to see if we end up in the same place.

Also, the extant model has far more space for adjustment in the frame rail than the screw provides. You can narrow the opening to the length of your required adjustment -- .25" for #25 chain and .375" for #35.

For what reason are you intending to press your bearings in to the outside of the bearing block? I think you could change that a bit and end up with bearing blocks that can be cut in one op. instead of two.

I've been trying to work on a one op setup, but I'm not sure exactly how to do it yet. The reason for putting the bearings on the outside is to allow as much stability on the axle as possible, which still keeping the setup as small as possible. As for the adjustment size, you have to be a lot more precise with your chain length if you shorten the adjustment size. We prefer to keep as much precision out of something like that as possible, for when you need to do those hasty repairs in between matches. Instead of only 1 link of travel, we prefer to have at least 3 to 5, so it's simple to swap out when we need to.

The next iteration should be 1 op, we'll see how that goes.

Thanks for the feedback!