4252A Pastoral Invasion Toss Up Updates

Our team has decided to keep our progress public (as many others) so as to help others, receive feedback, and hopefully keep ourselves at the edge of Toss Up competition.

We will most likely be posting pictures of what is built as we build it with brief explanations. You can also like our Facebook page or follow our website if you’d like.

So far we have a chassis mostly built. We need to buy more sprockets to complete it but here is a picture so far:

https://sphotos-a.xx.fbcdn.net/hphotos-frc1/p480x480/1004029_678008522226363_1106825242_n.jpg

Our “I” shaped design aims at being able to fit mechanisms in between the chassis sides on either end of the robot. We are using a 6-wheel drive designed to clear the chassis when driving over the bump and keep the skirt relatively low. We are using 6 393s geared at 1:1.6. All wheels are chained together so that they share power. The chain required very precise tension to minimize friction and slipping. The middle wheel is a standard VEX 4" wheel wrapped in non-slip mat to increase the diameter and provide maximum traction. Once we finish this chassis we will begin to incorporating our lift system.

Looks like a good concept to have separate manipulators. Many teams so far seem to be building to handle bucky balls well but are leaving the big ball handling as an afterthought.

Test your chassis on an actual bump as soon as you can. The coated metal surface of the bump does not offer much traction, so the wheels that are contacting the foam tiles are doing most of the work in getting the robot across it. Shortening the wheelbase a little (moving the corner wheels in) may help in getting across the bump more smoothly (hence more quickly). A 12" tower robot with a fairly central tower should be pretty stable, so a shorter wheelbase may be feasible. See how it goes. :slight_smile:

Cheers, Paul

Looks like a solid chassis; interesting thought on the traction material on the middle wheel; will be interesting to see how that works out. One thing I would advise you to do is to look at implementing some standoffs in the chassis instead of just relying on the chopped up bits of 1x25 and the axles. It looks like you would have space to put them in. Also, nice job implementing removal motor mounts! That will reward you later on down the road.

Thank you for the feedback! We will definitely make sure to test the drive as soon as possible and make changes as needed. HS sprockets were out of stock last time I checked so we haven’t had a chance to finish the other side.

We have began work on a double 4-bar lift. It should give us enough height to reach the hanging bar. The linear motion will compliment our de-scoring device. We currently plan on using a 5:1 ratio with two 393 motors. If we can’t pull that off we might switch to 7:1. We chose this design due to wanting a linear lift but while keeping the simplicity and reliability of a 4-bar linkage. We need to continue strengthening it and making the middle gear tower more robust. It’s looking good though.

https://fbcdn-sphotos-e-a.akamaihd.net/hphotos-ak-ash3/1016220_681698078524074_2140961165_n.jpg

I’m not sure if you remember this from last year, but 254D had a double 4 bar last year that didn’t have any of the slop from gears to switch direction for the top 4 bar. If you are pursuing the double 4 bar design, you might notice that there is noticeable slop from using the gears; using a bar will help this a lot, especially since you want to hang.

Here is the picture for the double 4 bar, don’t worry about the gears, they are there just for structural support.
https://vexforum.com/gallery/files/5/1/2/5/5/5/2012-10-22_17.33.55.jpg

That is a great idea. we’ll definitely play around with it on our next meeting. We did notice the gear slop and this looks like a great solution. The double 4-bar is certainly proving itself to be tricky, especially one you start adding a load. Luckily we have a lot of time to prototype and experiment. Thanks for tip!

We have not posted in a while but here are some pics of what we’ve got lately. Our design has shifted a bit. I won’t go into too much detail, but feel free to ask questions.

https://scontent-b-dfw.xx.fbcdn.net/hphotos-prn2/p480x480/1233556_720183721342176_1965011076_n.jpg

https://scontent-b-dfw.xx.fbcdn.net/hphotos-frc1/p480x480/998129_716529958374219_708082180_n.jpg

Hello,
First off the robot looks great :). I do have a few questions though,

Which direction would you define as your “front” and what made you choose to have different scoring mechanisms on opposite sides?

For the claw, I assumed you placed those 3 large balls on the robot for show. But can the robot store multiple large ones?

Overall the robot looks great :slight_smile: I look forward to seeing it on action!

How much does that weigh? It looks like at least 14-16lbs. Can you still accelerate at a decent rate? 6 motors seems like it should be fine, but I’m curious to know.

And what’s the lift ratio? I’m guessing you ended up needing at least the 1:7 you mentioned earlier.

This is a matter of great debate for the two of us. I wanted the large ball side to be the front, but Shane was extremely insistent in making the bucky-ball side the front. He won. Initially I planned for code to switch the front throughout the match, but Shane (the driver) preferred otherwise.

We chose two sides because we prioritize the independent flow of each kind of object. This expands our possibilities for transportation and scoring. Each intake is extremely well fitted for its object. We found our large ball scoop to be extremely accurate and effective.

The robot can pick up and store 3 large balls at a time without human intervention.

It is about 16lbs. The acceleration is definitely quick. Speed and maneuverability are not an issue with this robot. Going over the bump is also fairly easy.

2 393s at 7:1.

So on the subject of picking up the big balls… the roller doesnt look big enough, so does the fork flip them back into the hopper area?
Also kindly check your private messages. :stuck_out_tongue:

I am also curious about how it stores three large balls , with my robot i can barely hold 2, so i find that impressive :slight_smile:

another thought, how are your custom wheels working out?

as for the driving, would it be possible to use an arcade function on the joysticks, having “two fronts.” channel 3 would be “bb intake forward” and channel 4 would be “buckball intake forward”

Now if your driver prefers tank drive, then thats a diffrent story.

If your driver does prefer tank would it be possible to change the “front” direction by using a button insted of time? that might suit your needs more, this is just a suggestion :slight_smile:

They work as expected. They do not seem to affect the maneuverability of the robot in any noticeable way. They do make it much more difficult to push sideways, though. The biggest downfall is that it leaves little specks of non-slip mat around the field. We’ll also have to replace the mat between tournaments.

Can you guys hang?

Very cool and unique design. Looks like it will do the business :slight_smile:

Was the deviation from the reverse 4-bar arm design precipitated by the degree of difficulty in getting a bucky ball de-scoring mechanism to work effectively?

Nice work, Paul

Looks good, are ya’ll going to be in Houston on the 26th?

Kind of not really. We eventually decided to not implement a buckyball de-scorer which affected our decision to get rid of the double 4-bar. The biggest reason to get rid of it was the double 4-bar itself. In order to get rid of certain amounts of slop and instability there were certain modifications to be made. Modifications we were not willing or able to produce. So we switched lifts completely.

We should be going. See you there.

In our robot’s current state it cannot hang. With that being said, we do have a hanging mechanism built (there is an iteration of it on our Facebook page) using elastics and a pneumatic cylinder. As far as hanging with the lift is concerned we are able to lift the robot slightly off the ground, but it isn’t too reliable and would require some sort of wench to keep the lift down once the robot is disabled.

How many large balls does it hold at one time in a typical match? this is using your most dominant game strategy
Looks good btw! different than most designs!

Thanks. We are most likely to handle one large ball most of the time. We believe the most useful part of the 3-ball capacity is for endgame de-scoring. For example, if we can take 3 of their balls, hide in a corner while our partner can theoretically grab one, the opponents have no large balls to score or hang with. This could be done relatively quickly if they have a lot of balls scored in the goal zone.