[Merry Christmas]3921B's new robot CAD!

Merry Christmas VEX forum! In the last day of school I finally managed to finish off most of the designing of our new robot… So here is a pic and I’ll update it as things go.

You can see that everything is extremely messy… will fix it later.

Comments & criticism are welcomed!

new bot picture.jpg

What will be the max hight on that and what type of robot is it a cube bot or a sky rise section bot or both?

It is a double reverse six bar, the distance increase of the lift is about 57.7 inch, but because the cube intake seems to be able to flip the cube up we plan to score 3 on 7 skyrises.

We designed it to be a cube oriented robot, with three cube capacity. But it has a flipout slide behind the intake tray. We plan to use pneumatic intake for skyrise. Because the skyrise intake is designed to slide out very far, we basically plan to do the same as Canada videos- turn, lift and build with no extra movement.

Few things about this messy CAD:

I patterned bearing block on one bar to easily find out and constrain the best hole…
Only one side of the robot is built…
I started to dislike imates because of multiple reasons, so I turned on the extrusion surfaces and did old fasioned axis or insert constraints. Because I simply used extrusion to cut c channels, while not modifying any patterns, when the suface is turned on, things look very very ugly…

But anyway, we need to know what to do prior to building, and that is the most important thing.

Info about the bot:

mecanum drivetrain
4 motor 1:7 lift, 2 motors on the gear tower, 2 motors on middle section
2 motor 24 chain pieces per revolution intake. If I spare 2 motors on intake I make sure I push to their limit.
Because I am so used to designing with steel and that we just ordered aluminum, my design is very much weight reduction oriented. Sooo… I did a rough calculation of the weight of all structure based on the data in supersonic spark’s library, and the weight is 5.6 lbs. … … that is too light…

updates –
three positions: max, max stress point, lowest
The screen on my computer is so small, I had to orient the robot sideways to shoot the picture and then flip it back…

Looks like a pretty solid design, I’ve been working with a double reverse six bar for a while now, they’re awesome. Positioning one set of the motors on each vertical section of the lift will give you a ton of power, you’ll lift the three cubes like they’re nothing.
I only have two concerns, firstly the way you mount the bottom motors could be risky, just make sure that you tighten everything down very very well. Even the slightest change in how the gears mesh together will cause slippage.
Secondly, the cross support/stability bars that you have may not provide enough resistance to flexing. If when you build it you find that your lift seems even the slightest bit wobbly/unstable, try adding some ‘depth’ to the cross supports. Standard c channel is 1 by 2 by 1, it only rises above the plane formed by the bars of your lift one segment, this is the ‘depth’ of the piece. I have found that using L pieces works pretty well. Even just putting a c channel on the top side and bottom side of bars of the lift and then bridging between the two with some standoffs can greatly increase rigidity.
This is all because resistance to flexing in a rectangle is proportional to how close the width and the depth of your cross supports are (where width is the 2 part in the 1, 2, 1 X35 c channel, the 35 is the length and the 1 is the depth), your strongest cross support will form a square at the end (like a long piece of square tubing). L brackets model this shape nicely (they have equal width and depth).

Hope this helps, it looks like you guys are going to have an awesome robot pretty soon, good luck!

Thank you so much for the feedback. As a matter of fact, the thing I am worrying about the most is exactly rigidity. I have never worked with a double reverse before and I have little idea about how well my cross connection will perform. Thanks so much for the information.

The bottom motor mounting is more like an experiment-- aiming at saving space and minimizing the distance between motor and gear (practically zero). More importantly, I want to be able to reach motor screws conveniently. That’s a goal of my designing, the ability of conveniently taking off motors for inspection at worlds!

I’ll post some more details and changes later. Good luck to you too.

Keeping motors and sensors accessible is really important, especially at competitions where if something goes wrong you want to be able to fix it quickly. (Also prevents you from spending a whole afternoon replacing a motor that someone broke the pins off on. :))

An alternative to having the motor screw accessible if it’s not possible is to mount the motors on a small plate that is i.e. 2x2 holes, and then mount that plate on standoffs just beside the motor. This means you can remove screws facing out from the motor (opposite the motor screws themselves).

I’m not sure why you would want to remove the motors for inspection at worlds. The way they did PTC checks last year was that they asked you to unplug a motor at one point so they could connect it to a Cortex they had. They then applied power to the motor and held it still by hand until it stalled.

Just don’t want to crack or pop any gears by accident… never been to worlds before.

I did something similar on my previous scissor lift. I discovered how important it is to keep screws accessible after we were compelled to take apart the entire first stage of the lift to tighten a motor screw…