Cap Flipping Arm Help

Our team is new to vex and we would appreciate help in fixing our arm. It is a double reverse 4 bar. As of now, it struggles lifting all the weight and our only solution is to keep adding rubber bands. Does anyone have any advice? I’ve attached a photo.

What You could do is reduce the weight of the entire structure by half cutting the c-channels lengthwise at the top of the lift. As well, you could try to reduce as much friction possible by using screws instead of shafts at any axles possible. You can also add grease or some form of lubricant on the gears. Makes a huge difference!

PS, how are you rubberbanding it? The triangle method works best.

Looks like you’re straight shafting your motor to your lift. That’s a problem. You’ll want a torque ratio on that thing.
Also, one motor on your lift with 393 is pushing it. Unless there’s a second I missed. It may be helpful to strap on a second if you have a spare.
I can’t tell, but it looks like you have a steel frame. Alluminum is lighter, if you have enough. But steel can work in a pinch.

Additionally, that looks like an odd design for your lift. It won’t help your lift problems probably. But, why not make your base tower higher? Then, your whole lift can lower more and take up less lateral space on your robot. It would also lift higher, meaning your arms wouldn’t have to be quite so long.

Rubber bands

Drive the lift from the support towers, will reduce lots of weight

Thank you for answering! I think we are going to cut the c channels at the top, but how could we replace shafts with screws? Also, is there a better way to rubber band than what we have here?

Thanks for the help! If you don’t mind, I have a couple questions. We are gearing our lift for torque (with one v5 motor). Is there a better way? The motor is really weighing the lift down since it is on the c channel that raises and I don’t see a way to put it in the other side.

If it’s V5, you’ll be fine with just one. As @seanmac0230 suggested, you could drive it from the support towers, but I wouldn’t think that the energy transfer through the bars would make that much of a difference no matter where you have your motor. But if it’s in the middle, you are exerting energy through your upper stage and your lower stage, rather than through both in succession. I’m not sure if the weight of the motor would make that much of a difference.

No, you really do want to be gearing it for torque. I’m just saying that maybe it’s not quite enough torque. I assume you have the standard 200rpm motor on there. If you have it, a 100 rpm gearbox would give you more internal torque. Otherwise, I’d really suggest boosting your ratio by one gear size.

If looks like you have a 12 tooth gear powering a 60 tooth gear. Correct me if I’m wrong. That’s a 1:5 ratio. It’s not bad if you have aluminum. With steel it can be troublesome. Maybe compound your gear ratio to 12:36 (1:3) twice and then have that power your lift. It would be a 1:9 ratio, which is almost double what you have.

Another way to reduce weight would be to make your arms shorter. If you move your linkages closer together, you can also get more height. I would just figure out what height you need to get and see how high your lift is. If it’s overshooting, you can shorten your arms, thusly reaching not quite as high while still reducing weight.
You’ll also want to make your base towers about as tall as you can. That way, you can get more height from your lift, and hopefully end up being able to shorten your arms, reducing weight.

If you can’t find the space for your bear train where your motor is, you can move it to the base towers and attatch a gear to your arm. However, you’ll need two motors to do it on both sides; an advantage to powering it from the middle.

Hope this makes sense. Ask for clarification of needed.

I’m having issues visualizing this. How does this work?

i have had the same issue with my robot, how i fixed it was having the motors powered for the lift even if it was a stand still. don’t add too much power so it doesn’t go up on its own but add enough to hold the cap nicely.

@Got a Screw Loose @Vyx @Siraj @Kyle_Hodowany @seanmac0230
Thank you so much everyone.
I moved the motor to the tower so it is a lot lighter now but I am having trouble because the motor shaft only goes through one point. Any suggestions?

You pin your arms in certain places on each tower. If you pin them closer together, the lift will go higher.
Will go higher than:

The O is a pin point. @Vyx hope this helps. I would actually draw a picture, and I will if needed, but I suck at drawing.

What do you mean by “goes through one point?”
I assume you mean it’s not powering both sides, only one. If you can’t duplicate your setup, you could offset your rubber bands. Use more on the side without the motor than the side with. But that’s one advantage having of 1 motor lifts powered through the middle; they can power both sides.
I really recommend sparing another motor and lowering your torque ratio some to make your lift faster, but this will work if you don’t have the extra to spare.

@Embot I’m sure there are some teams out there who don’t have accounts who may appreciate a picture of your finished product when it’s done. Also I’m curious as to how much has changed visually. Just an idea.

What do the 1’s represent?

probably means this

Oh! Okay, that makes more sense. Thank you.

Yes. The 1s were the base tower. Thanks.