Dad's Design

[Tanner]

Ah, didn't know that option was being explored.

Well, I just thought about it last night. You didn't wonder what that thing was on the back side of the robot in the CAD drawings?

Anyways, I still stand by the option to implement space saving devices. At the least, implement the things that you and I talked about at the meeting just so it's not spanning over the entire chassis.

Yeah. If I could remember them and didn't have a headache, I would implement them.

-Tanner

[Sunny]

Well, I just thought about it last night. You didn't wonder what that thing was on the back side of the robot in the CAD drawings?

Ah..that's what that is. I thought it was the winch for the end game. And just thinking about the torque that we'd be getting out of one of the fisher price motors, we could probably get upwards of 50-60 pounds of pull back, assuming we'd be using a 2" radius winch.

Yeah. If I could remember them and didn't have a headache, I would implement them.

Whatever, we can go over it in the next meeting if we have time. It's just a prototype anyways. It'll need some trimming/fitting done until it's ready for an actual bot.

[Tanner]

A reiteration of the ideas for tensioning/cocking mechanisms.

Tensioning:
Surgical tubing is led from the top of the kicker to the back onto a pulley controlled by a motor. This motor is run by like a worm gear or something - ideally something strong and fast. This allows us to tension the kicker at different strengths allowing us to kick the ball different distances and so forth.

Cocking:
A string is attached to the top of the kicker to a pulley mounted about the same height at the front of the robot. From this pulley, we lead down to a) another pulley with a motor or b) a linear actuator linked to the first pulley with a series of pulleys forming a "U" shape with the string.

How does this all work together? Simple. This list is assuming, hey we just shot ergo the kicker is in a state of wobble not attached to anything with no power.

1. The tensioning mechanism (thing attached to surgical tubing) relaxes the tubing.
2. The cocking mechanism begins to wind up the string attached to the top of the kicker. Hence, the kicker begins to easily move into the cocked state.
3. Latch grabs onto the kicker. Tensioning mechanism begins to increase tension to the tubing, setting up the power of the shot.
4. Cocking mechanism unwinds the string. This is so we can easily fire without relying on the motor driving this.
5. Driver pushes a button, latch releases, sending the kicker rotating and the ball flying.
6. Whole process repeats without delay.

Obviously, the limiting factor is the speed of the motors. There are at least one or two motors that we are "waiting on" for this entire process to complete and for us to fire a ball. Though we have two seconds until we can fire again, I do not know if we can do this. If we could use another CIM it would help a lot.

Dad has been thinking of some way to combine the cocking and the latching mechanisms into one mechanism in a way like the we cocked the catapult in 2008 for Overdrive. Though we can't use those magnetic clutches, he's thinking of air clutches. I think we could use a gearbox with two gears - one neutral and one drive or some sort of gearbox where we can switch from drive and neutral by switching the direction of the motor (without relying on pneumatics/servo to switch gears).

Obviously this design needs some tweaking to make it a bit more efficient.

-Tanner

[Tanner]

Dad was thinking about using the Forsyth catapult mechanism for forcing the kicker back into place, but it seems theirs relies mainly on gravity and the force of the arm. Not really applicable for us as we are lifting ours up, not down.

-Tanner

[Sunny]

Obviously, the limiting factor is the speed of the motors. There are at least one or two motors that we are "waiting on" for this entire process to complete and for us to fire a ball. Though we have two seconds until we can fire again, I do not know if we can do this. If we could use another CIM it would help a lot.

Dad has been thinking of some way to combine the cocking and the latching mechanisms into one mechanism in a way like the we cocked the catapult in 2008 for Overdrive. Though we can't use those magnetic clutches, he's thinking of air clutches. I think we could use a gearbox with two gears - one neutral and one drive or some sort of gearbox where we can switch from drive and neutral by switching the direction of the motor (without relying on pneumatics/servo to switch gears).

Ideally, a CIM would be great here, but I think the extra CIM is needed more in the end game than the actual game play.

I'm not sure what you mean by "switching the direction of the motor." But on Chief Delphi, I think the preferential cocking/launching mechanism is a dog gear. From what I understand, it's basically like a shifter, but when you're in the dog gear, the motor pulls the winch back, and when the dog gear is shifted out of place, the entire mechanism spins free. I know we were trying to avoid shifting, but this mechanism does two things for us.

One, it gives a mechanism to gauge how far we want to kick the ball. You've taken away the CIM, and put the fisher price motors to pull back the "cocker". Whenever we feel like firing, we kick the dog gear out of place. This is an instantly adjustable method, we don't need a winch for the pneumatic tubing, and we've saved that CIM until the end game.

I dont' quite 100% understand how the dog gear system works, but its best implementation can be found in 1114's 2008 robot, which was pure beast. http://www.chiefdelphi.com/media/img/ad ... fa84_l.jpg

[Tanner]

I kinda think that we should stick to the theory of "let's do one thing and do it well." Not that we can't do multiple things well, but usually teams don't do them well.

Getting Dad to do some research on a dog gear. Or at least, I'm waiting for him to explain it to me as a Google search returns nothing but gear for dogs.... Heh.

Remind me to make a image like that to print out to give to teams for scouting. That's quite nice.

-Tanner

[freds]

Sunny, any details on their wench drill mechanism, which drill manufacture and whether the dog gear was part of the drill or not?

[Sunny]

Sunny, any details on their wench drill mechanism, which drill manufacture and whether the dog gear was part of the drill or not?

The following thread talks more about the dog gear setup: http://www.chiefdelphi.com/forums/showt ... t=dog+gear

"Simbotics used a Dewalt transmission that does not backdrive, so they don't need to power the motor to hold it in place (this is important because you don't want to put power to the motor when the motor isn't moving). The Supershifters and the Gen 2 can backdrive, so you would need to further modify them so they don't backdrive if you wanted to do a winch like Simbotics did."

The above seems to be the most descriptive statement I can find.

"In 2008, we used a Gen 2 servo shifter to a garage door spring (200 lbs. force or more to "crack it"). The AM shifters are GREAT at winch applications. Instead of winding up the surgical tubing itself, try winding up 550 cord (google it or ask any armed services member) to winch. It has a 550 lbs. breaking strength in a very small package with minimal stretch."

It seems that the Gen2 shifter from andy mark is a popular system. Although I don't quite understand the difference between Gen1 and Gen2. But I would think that if we were to get one of these shifters, we can just not place in one part of the tranny, so when we shift from a to b, b has nothing to connect with and we are effectively in "neutral" and the kicker has free reign to swing.

[Logan]

A dog gear is usually interfaced with another dog gear to create a "lock", connecting two independent shafts. When they are disengaged (like in a shifter), the two shafts spin freely.

Here's a nice picture of one.


Imagine two put together and you can rotate two independent shafts together while the gears are engaged, and you can rotate the two shafts separately when the gears are disengaged.

Here's an image of two dog gears engaged.

[Tanner]

There's not much difference between Gen1 and Gen2. Gen2 just allowed for larger motors in years ago.

The AM Shifter Gen. 2 is the same version as this Gen. 1 gearbox, except there are different side plates on the Gen. 2. These side plates were used for a larger motor provided to FRC teams in 2005-2007. We still make this part available for legacy purposes. The two side plates have different holes compared to the Gen. 1 and the Gen. 2 is taller by 1/4" and shorter in length by 5/16".

I think our best bet is a shifter, but that is only because we can't use anything else without breaking the rules.

-Tanner