Do you have to use 2x1x1/8" tubing for a WCD?

[MattC9]

Originally Posted by SuperNerd256

While I can use it, we've used .5x.5x1/8" steel tubing for our entire superstructure this year and found great success with it. Is there a reason for using the 2x1x1/8" tubing most teams use when making a WCD?

Thanks!

Now is it steel or aluminum, because steel would get really heavy after awhile.

Originally Posted by MattC9

Now is it steel or aluminum, because steel would get really heavy after awhile.

It's steel, but it's surprisingly light. Our entire superstructure this year was under 60 pounds, which allowed us to switch out our entire frame with the steel by our second regional.

[BrendanB]

I think there needs to be some clarification in this thread. WCDs typically use 2x1x1/8in walled ALUMINUM tubing, not steel if I am correct. There is a huge weight difference between the two!

[sanddrag]

Originally Posted by SuperNerd256

It's steel, but it's surprisingly light. Our entire superstructure this year was under 60 pounds, which allowed us to switch out our entire frame with the steel by our second regional.

I hope that 60 lbs includes all motors and additional parts. Our superstructure frame was about 8lbs. I just can't see the argument for steel tubing (or steel anything other than gears, chains, bearings, and bolts) in FRC.

Originally Posted by sanddrag

I hope that 60 lbs includes all motors and additional parts. Our superstructure frame was about 8lbs. I just can't see the argument for steel tubing (or steel anything other than gears, chains, bearings, and bolts) in FRC.

All motors and additional parts were bagged and tagged. An 8lb superstructure? What did you use? What did it look like? Was it strong enough?

[billbo911]

I have a simple question about the construction of a "WCD" system. Having no experience with these, yet, we want to learn from other's experience to help minimize the normal error associated with trying something new.

I see mention of using "bearing blocks" quite often when building WCD's. It is necessary? Couldn't the bearing's be pressed directly onto the walls of the tubes?

[A_Reed]

Originally Posted by billbo911

I have a simple question about the construction of a "WCD" system. Having no experience with these, yet, we want to learn from other's experience to help minimize the normal error associated with trying something new.

I see mention of using "bearing blocks" quite often when building WCD's. It is necessary? Couldn't the bearing's be pressed directly onto the walls of the tubes?

Team 48 has done this the past two years with no issues. Instead of including movable bearing blocks to tension the chain you have to design in additional tensioner. We have just used 1" round Delrin(Acetyl Resin) with a hole drilled off center with great success, turn the cam against the chain and then tighten down a bolt to hold the cam in place.

Here are the CAD files for our 2011 robot. The bearings are pressed into the frame members as discussed, but the delrin chain tensioners aren't included. They are more of a install as needed device. You may also want to find the equations to calculate chain lengths based on an even number of links, this should lessen the need for tenioning and half links.

[HammadB]

Originally Posted by billbo911

I have a simple question about the construction of a "WCD" system. Having no experience with these, yet, we want to learn from other's experience to help minimize the normal error associated with trying something new.

I see mention of using "bearing blocks" quite often when building WCD's. It is necessary? Couldn't the bearing's be pressed directly onto the walls of the tubes?

I see two main purposes of the bearing blocks. One, they allow for adjustable chain tension by sliding back and forth. And then they also support the axle more. However, we did run an 6WD drive this year with another set of wheels in the front for total 8 wheels. The set in the front had bearings pressed into the frame. However, since we were running a drop center they were raised above the ground while we were driving, and not really taking on any load.

[BJT]

Those bearing blocks on many wcd's are really nice, and if we had the resources, we might do it that way, but they are not necessary. We also build ours like Mr Reed from team 48 explained. I use one of those step bits to drill the 1.125 holes for the bearings. they make a real nice hole. It's not a super tight fit, but a little loctite takes care of that. The real trick is getting them perfectly across from each other.

[Chris is me]

Originally Posted by billbo911

I see mention of using "bearing blocks" quite often when building WCD's. It is necessary? Couldn't the bearing's be pressed directly onto the walls of the tubes?

If you are abandoning a sliding bearing block, absolutely. We've done this for two years without issue.

[Gray Adams]

Originally Posted by Chris is me

If you are abandoning a sliding bearing block, absolutely. We've done this for two years without issue.

What do you do for chain tensioning? Sliding bearing blocks are one of the cleanest ways of tensioning chain that we've discovered. I suppose you could do exact distances, and hope that your chain is perfectly tensioned and doesn't stretch enough to become a problem, but I wouldn't want a drive train without control over my chain. That's what happened last year basically (and every preceding year), and it was really terrible. We thought breaking chains was a normal thing during operation.

[Chris is me]

Originally Posted by Gray Adams

What do you do for chain tensioning?

We don't use chain, we use timing belt. That's the only reason we can get away with it, since timing belt does not stretch.

[Gray Adams]

Originally Posted by Chris is me

We don't use chain, we use timing belt. That's the only reason we can get away with it, since timing belt does not stretch.

We're probably going to try timing belt for next year, so that would be an interesting thing to test. Do you weld anything near your drive trains (or would you worry about warping ruining your tension if you did)?

[JackS]

Originally Posted by Gray Adams

We're probably going to try timing belt for next year, so that would be an interesting thing to test. Do you weld anything near your drive trains (or would you worry about warping ruining your tension if you did)?

I'll give the basic run down of our chassis.

We use 3x1.5" 1/8" wall AL tube for the drive rails and 1x1x1/8" tube for cross supports and a 1/16" belly pan. We start by riveting on the belly pan and "framing gussets" to hold the assembly in the proper orientation for our welder. As he goes, he removes the gussets, but welds the belly pan to the chassis.

Next we put the belts in the tube. We put the belt around the pulley and feed the pulley down the tube using gravity (the chassis rails are tipped up.) This works because the pulleys are the exact same size as the inside of the tube and the belt is unable to slip off the side of the pulley. Once the center axle is placed in the center pulley (which already has both belts on it) the outside pulleys are next. Our bearing holes have a key which allows the axle to fit through. We slide the axle in the pulley and pull back on the axle until it is in the center of the bearing hole and slide the bearings on either side of the axle, securing it in place. This is the center to center location.

If you remember, the pulleys are the exact size of the tube, and the bearings are 1/4" long. This forces us to space the bearings out of the tube with a 1/8" spacer. On the ends, where the bearing holes are keyed, the spacers are riveted to the frame for extra support. We then use 4 10-32s and attach our gearboxes to the tapped holes in the frame.

This was the last time we touched our drivetrain the entire season. (We did do a dry run of the gearboxes before we took them apart to teflon the gears.)

Let me know if this doesn't make sense. We do plan on taking apart our drivetrain and putting it back together to make an instructional video. I also have been cleaning up our CAD model for publishing. Renders should be up in a few days and I will have a link for download.

[Hawiian Cadder]

Originally Posted by JackS

I'll give the basic run down of our chassis.

We use 3x1.5" 1/8" wall AL tube for the drive rails and 1x1x1/8" tube for cross supports and a 1/16" belly pan. We start by riveting on the belly pan and "framing gussets" to hold the assembly in the proper orientation for our welder. As he goes, he removes the gussets, but welds the belly pan to the chassis.

Next we put the belts in the tube. We put the belt around the pulley and feed the pulley down the tube using gravity (the chassis rails are tipped up.) This works because the pulleys are the exact same size as the inside of the tube and the belt is unable to slip off the side of the pulley. Once the center axle is placed in the center pulley (which already has both belts on it) the outside pulleys are next. Our bearing holes have a key which allows the axle to fit through. We slide the axle in the pulley and pull back on the axle until it is in the center of the bearing hole and slide the bearings on either side of the axle, securing it in place. This is the center to center location.

If you remember, the pulleys are the exact size of the tube, and the bearings are 1/4" long. This forces us to space the bearings out of the tube with a 1/8" spacer. On the ends, where the bearing holes are keyed, the spacers are riveted to the frame for extra support. We then use 4 10-32s and attach our gearboxes to the tapped holes in the frame.

This was the last time we touched our drivetrain the entire season. (We did do a dry run of the gearboxes before we took them apart to teflon the gears.)

Let me know if this doesn't make sense. We do plan on taking apart our drivetrain and putting it back together to make an instructional video. I also have been cleaning up our CAD model for publishing. Renders should be up in a few days and I will have a link for download.

What type of belt do you use? We have shredded the .2 pitch XL .4 wide belts we have used every time we ran them on a robot.