Adjustable Way of Dropping the Center Wheel

[R.C.]

Well, every drivetrain created in FIRST is unique and different. I thought of a way to adjust the amount of drop in the center wheel.



The first drawing is the part of the frame, the second part is the adjustable part. The drop is an increment of 1/16". 1-16 to 1/4.

[Greg Needel]

I really like your thought process here, and it is defiantly an interesting solution. The question I have is how often do you think you will have to change your center wheel displacement? Probably not very often during a competition but if this was for a development platform or practice bot I could see this coming in handy. Nice job.

[AdamHeard]

That's certainly one way to do it. I like it.

In 2007, 294's center wheel sat in a block on each side that was sitting in a slot. The bottom of each block was tapped, a bolt came up from the bottom of the frame into it. Tightening the bolt would pull the wheel farther down. Similar to how 294/968 tensioned their outer two wheels in 2006, but rotated 90 degrees. However, we quickly realized during the season that it wasn't very useful.

[RyanN]

We used a pnueumatic center wheel. When we wanted to raise it, we put more pressure in; lower it, drop the pressure.

[Herodotus]

I really like the idea, but I will echo what the others have said, as you probably won't have to adjust it much during the season. However I could see the idea being applied to different areas where adjustment is needed.

[EricH]

Originally Posted by RyanN

We used a pnueumatic center wheel. When we wanted to raise it, we put more pressure in; lower it, drop the pressure.

That's 330's strategy, except that the wheel is already dropped.

[R.C.]

The reason for this is that we dropped our wheel last year at 1/8", but this year it needed more but we were stuck with an 1/8 because of the way we did it. So in postseason i tried this and we lowered it to 3/16" and the frame turned like a champ.

[popo308]

Originally Posted by RyanN

We used a pnueumatic center wheel. When we wanted to raise it, we put more pressure in; lower it, drop the pressure.

Originally Posted by Herodotus

I really like the idea, but I will echo what the others have said, as you probably won't have to adjust it much during the season. However I could see the idea being applied to different areas where adjustment is needed.

Well one situation when a pneumatic actuated center wheel is nice is if the game requires alot of pushing power then you can make it so all 6 of your wheels are on the ground at once. That obviously would make it very hard to turn especially if your wheels are wider than an inch. Then when you wanted to turn you could increase pressure and push the center wheel down farther and spin around very nicely.

However if your not going for that as others said you probably wont move them much once you find a nice offset that works for your robot.

[EricH]

Uh... not pneumatic actuated, pneumatic. There is a difference. Pneumatic actuated is a cylinder attached to the wheel; pneumatic is like a car or bike tire; i.e. air-filled. You can't change the pressure mid-match, though a nail on the field might change it for you.

[IKE]

Originally Posted by rc_cola1323

The reason for this is that we dropped our wheel last year at 1/8", but this year it needed more but we were stuck with an 1/8 because of the way we did it. So in postseason i tried this and we lowered it to 3/16" and the frame turned like a champ.

Cool. One thing to be careful of when testing a chassis during the build season is to have proper weight and surface (i.e. carpet). We have built many chassis that seemed crazy manueverable on concrete, and then added mechanisms and put it on carpet and voila, it turned like a 10 ton dump truck.

You can also change the "drop" by lifting the front or rear wheels. These are often easier as this will only effect tension on the chain loop to them as changing middle wheel drop often includes messing with multiple chain loop tensions.

[R.C.]

Originally Posted by IKE

Cool. One thing to be careful of when testing a chassis during the build season is to have proper weight and surface (i.e. carpet). We have built many chassis that seemed crazy manueverable on concrete, and then added mechanisms and put it on carpet and voila, it turned like a 10 ton dump truck.

You can also change the "drop" by lifting the front or rear wheels. These are often easier as this will only effect tension on the chain loop to them as changing middle wheel drop often includes messing with multiple chain loop tensions.

We found this out the hard way, we could turn on the concrete with the arm, so we didn't drop the center wheel enough. Competition time comes and boom, we can't turn unless in low gear.

[gorrilla]

{kinda off topic} because we usually only had to turn right 1557 used a two wheel drive in the front with two skyway wheels side by side to each other in the back left and a caster in the back right that was raised about an 1/8th inch so when we turned the robot would lean to the right and make turning a breeze.

[Jonathan Norris]

I remember hearing that Truck Town had a pneumatic actuated center drop in '06. From what I heard they would have all 6 wheels on the ground when pushing, and could 'pop' their center wheels down with pneumatics when needed for turning.

[R.C.]

How much stroke on that piston???

[R.C.]

also how thick should the second piece be for safety reasons, 1/8, 1/4 or 3/8