pic: 114's new tensioner

[T3_1565]

I really like this idea thanks for sharing it I may show the team it at sometime lol

[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.

[MrForbes]

Also you could make the "halves" so they are not really halves, but one thicker than the other. Then you could just thread one of them and eliminate the round part. The hole for the tensioning bolt can go thru to the center area, since it only has to "miss" the axle.

I think it's a neat design, I also think you can refine it quite a bit more to make it more simple or easier to make. This part of the process is great fun!

[Tom Bottiglieri]

What are you concerns over constantly changing your robots wheel base? I've seen a few systems that work like this.

[JesseK]

Hmm, this is in deed much better than the last design. For further refinement, you could turn the bolt around so it faces the opposite way, screwing into a nut that's spot-welded to the frame or an immovable delrin block. Flatten the round shaft on the bolt at one point to give 2 or 4 flat surfaces for a wrench and I think it's nearing perfection.

It's still fantastic as-is though.

[Nuttyman54]

Originally Posted by Tom Bottiglieri

What are you concerns over constantly changing your robots wheel base? I've seen a few systems that work like this.

Team 971 used a tensioner like this last year, and that really wasn't a concern for us. The amount that the wheelbase actually changes is insignificant when compared with the distance between wheel contact points.

[Karthik]

Impressive, it looks very similar to the tensioner that 968 used last year. Another fine example of west coast teams sharing each other's designs to the benefit of all. No wonder the quality of play has increased so dramatically!

[Elgin Clock]

I'm all about visuals, and understanding things by seeing them... but...
uh... what is this for?
I'm actually quite lost on this one it seems.

Edit: Ok. Seeing this pic helped me see what it was going to be used for.
http://img50.imageshack.us/img50/155...ndframeur8.jpg

There is only one issue I can think of right now. When you move the bolt so the head is sticking out of the frame more to increase(?)/decrease(?) tension as it may be, wont that bolt go out of profile if your frame is not short enough to account for that? (Edit: Wait... will the bolt head move, or is it just acting like a lead screw? <-- Answered below by Nuttyman. Thanks. I was imagining something a little different than how it actually works.)

It is a cool concept.
But, I would have rather used a turnbuckle style fastener between the centers of the pillow blocks rather than something on the outside if that would be possible while not interfering with the chain itself running (presumably) inside the box extrusion.

Also, a side question for teams who run chain inside box extrusion.
Have you ever had problems of your chassis getting damaged and thus the deformed shape interfering with the chain running inside?

[Nuttyman54]

Originally Posted by Elgin Clock

Wait... will the bolt head move, or is it just acting like a lead screw?

It acts as a lead screw to slide the bearing block in the frame slot.

[Elgin Clock]

Originally Posted by Nuttyman54

The bolt head never moves farther out (look at where the threads engage). This works by sliding the actually bearing block in the frame, and thus moving the wheels closer or farther away from each other.

You beat me to the punch. lol Look at my edited question I popped in. I guess some issues are non-issues now. Thanks for the explanation.

[Madison]

Originally Posted by squirrel

Also you could make the "halves" so they are not really halves, but one thicker than the other. Then you could just thread one of them and eliminate the round part. The hole for the tensioning bolt can go thru to the center area, since it only has to "miss" the axle.

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.

[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

[MrForbes]

This is all making our practice of drilling two holes thru a piece of fiberglass I beam sound very easy......

[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!