Hello. I recently competed in a Skyrise competition at Sultana High, and my robot stripped 3 high power 5 gears in a 1:75 ratio and bent a few driveshafts. It was very inefficient, and after posting pictures of it on other sites, I’m being told it was build horribly wrong. Here are som pictures http://imgur.com/gallery/5qBFQ. I’ve been told there should be at least 4 393 motors, and they should be lifting from the top or top and bottom. Does anyone know how I can fix it? If I can’t fix it, I will probably build a whole new bot, and if that happens I’d like to build a linear slide or chain driven vertical lift, but I can’t seem to find designs or building instructions anywhere. Any help appreciated 
VEX 393 motors are more powerful than you think. Usually a 4 motor 1:25 lift is enough for most normal applications in skyrise, based on my experience. When you increase your gear ratio, you give your motors more power to potentially break gears and shafts if not handled properly.
I would suggest trying a gear ratio more like 1:15 or 1:21 on your lift. A lot of teams prefer 1:7 with elastic assist for a bar lift also.
Okay. I was planning on trying 1:15 on both sides anyways. I would’ve had elastics on there, but we didn’t have any. Should the motors be lifting from the top, bottom, or both?
According to your image, I would suggest powering it at its gear tower, the point where the arm connects the fixed structure on the base. This usually provides more stability and is what most teams do.
As a side note, you might also want to take a look at how your wheels and drive motors are mounted. Try to avoid cantilevering them and see if you can move the motors closer to the wheels.
P.S. I like your username.
That’s what I was planning
That’s what I was planning. THanks for the input.
Everyone always thinks it’s cantilevered, but the axles all pass through 2 parts of the frame with bearings, but they could be closer together.
In my time in Vex, I have split 2 worm wheels, ruined teeth on 2 worm gears, broke multiple teeth on 2 hs 5 gears, and stripped the inside of 1 5 gear (not to mention ruined driveshafts :p)
This robot here uses the same lift design.
However it uses a 1:7 ratio on 4 393’s and lifts 2 cubes.
I thought carrying more than 1 cube at a time was illegal. Or maybe it was skyrise sections. I don’t remember:confused:
Skyrise sections are limited to 1 at a time, but there is no limit on cubes. Well, there is a limit of 44, but it would be pretty hard to hold all of them.
I didn’t see, but my dad said that there was a bot that grabbed 3 at once in a claw and put them on the skyrise. Sounds interesting. I still think I’m going to try a linear lift or heavily modify what I have.
:eek:
:eek:
go to a local dollar store and buy a bag of #32 and #64 rubber bands for your robot ASAP. Last year, I didn’t use any on my first robot and almost destroyed it at a competition trying to get it to lift up.
Will do