Hi! My team is thinking of putting our intakes on arms, and I was wondering what design tips you guys can offer to make the arms stable and avoid bending or warping
Would you recommend using 1 motor or 2 for the arms? I feel like 1 would make sure they’re perfectly in sync, but might also not be strong enough
for lifting them, one is strong enough, geared 1:7 with hs axles. For the intakes, 2 is like the only choice or at least meta
yeah, we already have the intakes built, we’re just building arms for them
make sure to make them vertical, and supported/braced well. Just have them on the same hs axle and you should be fine.
how would you recommend bracing the posts to the base? i’ve had trouble connecting stuff diagonally b/c the holes don’t line up.
PS i’m sure there’s some easy way to do this, this is my first year in VEX and i don’t know all the building techniques
you mean the c-channel stuff to the base? a triangle brace and a brace with c-channels to the base.
is it easy to get the screw holes to line up? I haven’t been able to make diagonal connections work
so a c-channel connecting the upwards c-channel towers to the base, and a triangle brace, or have the sides connected to the base, like this: (it starts at a certain time so click)
make sure your arms cannot flex. if you box the c channels on your arms, and have really good bracing between the two, you don’t even have to power both sides, you can just power one side and it will be able to pull the other side up with it without causing any leaning.
by boxing you mean overlapping two c-channels facing each other right? basically making a tube?
yes. also using spacer-screw connections where you attach your cross bracing helps reduce torsion on your arm. that’s where you put a screw all the way through the bracing, the top of the arm, and the bottom of your arm, and fill the gap inside the c channel with spacers.
Just wondering, would using a 1x5x1 c channel or maybe even a 1x3x1 eliminate the need for boxing?
1x5x1 would be thicc as hell for arms though
on the arms or cross bracing?
if on the arms, no probably not. you’d just add more weight.
if on the cross bracing then maybe. you want to use 5 wides for the cross bracing, the extra stability is worth the weight.
you technically don’t need to box your arms, but I recommend it, it will make them rock solid, and it doesn’t add too much weight.
For arms and cross bracing, Iv’e seen other teams with the 3 wides on the arms, bracing, and without boxing have enough strength for 11 cubes because we do not have enough c channel to box in the arms.
if you wanted to decrease the horizontal flex in your arms, you could maybe have your arms’s c channels mounted on their sides, c channels don’t bend as easily side to side as up and down. you’ll just have a funkier gearbox and less space efficient arms.
Unfortunately our mounting space is not large enough to fit a C channel on the side so we’re limited to having them face up
Here is a list of options and how you can do them from easiest to most difficult.
- 1bar lift (9:1-15:1, red motor)
i. Pros: Simple, less weight, compact
ii. Cons: Not much mechanical advantage, slow, higher tray angle, can’t reach middle tower
- 3bar lift (7:1-15:1, red motor) [Power this from the lower horizontal bar]
i. Pros: Mechanical advantage, fast, lower tray angle
ii. Cons: Can’t reach middle tower
- 4bar lift (9:1-15:1, red motor)
i. Pros: A lot of mechanical advantage, can keep intake level
ii. Cons: Somewhat heavy, takes up a lot of space, Can’t reach middle tower
- Scissor lift (15:1-36:1, red motor)
i. Pros: Can reach middle tower, very low tray angle
ii. Cons: Heavy, usually needs two motors
- Double reverse 4bar lift (9:1-24:1, red motor)
i. Pros: Can reach middle tower, mechanical advantage, faster than scissor lift
ii. Cons: Heavy, usually needs two motors, high tray angle, unbalanced
- Cascading lift (15:1-36:1, red motor)
i. Pros: Can reach middle tower, compact, balanced
ii. Cons: Heavy, needs two motors, hard to build
I could be wrong with something on here or missing one, but this is what I’ve learned so far. My team is using a 3bar lift with a 9:1 geartrain and a red motor. The tray can get to 40 degrees. There is a lot of tensioning with rubber bands to get the whole thing working, but it does its job well. Sometimes, though, we will have a 36 tooth hs gear just break a tooth off and it’s happened twice now where we’ve had to replace them. It is hard to pinpoint the problem, but it could be a number of things. Good luck!