Does anyone have an idea to why our lift is not working? We suspect it’s the gear train. The lift moves very smoothly up and down lifting it up with your hands. When the motors are active, it can go down as it should, but it barely goes up. We tried some different motors, but it still wouldn’t go up.
If you need anymore information, let me know.
You’re trying to direct drive it. The motors do not have enough torque for that.
The motors should be connected to the 12 tooth gears instead of the 60 tooth gears to increase the torque because the motors do not have enough torque to lift the arm directly.
Also, where the bottom section of the arm is bolted to the 36 tooth gear, the shaft will twist so you should connect the c-channel to the holes in the gear as you have done on the upper gear which the motor is currently attached to.
From what I see from this picture there are also no rubber bands on the lift. You will probably need to attach some rubber bands to get a high performing lift.
Also be sure to adequately rubber band your lift, you can look up DR4B videos on YouTube to get an idea what that should look like.
LOL same comment within seconds of each other
Considering the possibilities, I am guessing that if you rubber band the lift it would still “barely move up?” I think what’s going on is that one of the motors have locked up where they can easily spin one direction but not the other. I had this problem with my lift before but replacing the motor fixed it (obviously). I’m unsure if this is the case for you but try replacing both motors with any other two motors and attach the previous lift motors to an axle with a gear and hand spin them to see if they spin or not.
I’m pretty sure his main problem is that he has a 1:1 gear ratio on a DR4B. The rubber banding was just a tip that would help in the future.
The motor should drive the small gear which then drives the big gear giving you more torque
Oh, I didn’t even realize that. Yes, that’s a very good point.
A 1:1 gear ratio won’t lift a DR4B no matter what gear cartridge you’re using.
Okay…okay. Fair enough. But it’s not exactly practical.
We already knew about the rubber bands, they were just off as the lift was being taken apart already. Thanks for the help. We’re going to try and move the motors down to the 12 tooth. Will keep you updated if the problem persists.
Yup. Should fix your problem. Good luck. 
So after moving down the motors to the 12 tooth, it actually did seem to work. However, when we added our structure for collecting the cubes to the lift, it ended up having not enough torque to lift the lift anymore. We attempted to replace the 60 tooths for 84 tooths, but the same issue happened. Is there a better gear train layout that could give us more torque?
Try checking for any spots with friction. If that doesn’t work use 100 rpm cartridges if you haven’t yet.
You can also use rubber bands to help with that, although it’s not recommended to depend on those to make your lift work.
Try cutting weight from the lift. Keep in mind your lift will still have to lift the weight of the cubes.
If you’re dead set on a dr4b and you still cant make it work, maybe create a double layered 12:84 ratio. It’s really bulky and impractical, but if you realllly want, then it’s an option.
Use this tilter mechanism if you want to make a jacked up lift. Otherwise consider redesigning.
#leeks
Here are a few things you could try, you could replace your acle jointa for your unpowered gear with screws going through the the center hole acting like a shaft for the gears. You could try making the space between you support bars smaller, I noticed you have a 4 hole spacing between those bars but you only have an HS gear and a C-channel between them. Last thing, you should provably move the powered 12 tooth to either the top or the bottom of the gears, and the lifting bar gears are meshing directly.
Try this design that @technik3k proposed but substitute the 60 tooth gears with 84 tooth gears.
It is a well known “secret” among the veteran VRC teams that it is best to use single bearing screw joints when building 4B, 6B or DR4B/6B lifts.
With them you can achieve minimum slop, which translates into more stable lift that could go higher with more precision and less wobble.
When assembled correctly nylock nut is tightened almost all the way, but not fully such that you could still rotate the white spacer with your fingers.
To reduce slop and increase precision further you can use longer (2") screws. Below is a picture of the 2" screw tower connection for DR4B:
However, you have to be careful and need to regularly check those screws, because if they get bent you will end up with more friction losses than benefits.
Similarly, to reduce wobble you could increase the width of the arm/gear assembly in the mid-section. Here,1.5" screws hold an extra bearing on 3/8" nylon spacers (note that spacers are slightly rounded with a grinder wheel to fit the shape of the newer 60T gears):
On the other side of the gear keps nuts are used for better overall stability:
Washers are added under and over the keps nuts to get the perfect distance where c-channel is almost touching the gear.
This fits perfectly with 2" screw that acts both as a gear axle and rigidly connects both sides of the DR4B mid-section. Same as with the tower connection you need to tighten the nuts such that there is no visible slop, but not too tight, to avoid any unnecessary friction. After the final assembly you can use a small ziptie to add some white lithium grease lubricant under the bearings and onto the gears.
As you can see on the side view there is no need for any additional connecting hardware. Four 2" screws used as axles also connect the sides of the mid-section.
You can assemble top and bottom parts of the DR4B separately and then connect them at mid-section to get the optimal alignment between the gears.