DR4B Assistance

DR4B Assistance

Hello, my team has begun to build a dr4b but had a few issues I was hoping someone could help with.

 1. The lift seemed to wobble left and right is this something that could be fixed by tightening things?

 2. There was a lot of slop on the lift again is this something that can be fixing with tightening?

 3. What gear ratio and how many motors should be used(we used EDR).

an optimal gear ratio would be 1:5 on High speed, considering that most of the rd4bs this year are a lot lighter than the ones from last year. For, wobbling, you want to add cross bracing between the 2 sides and screw the x together in the middle. Try watching some videos of good fast rd4bs from last year and look at the designs. They should give you a pretty good idea of how to go about it.

I’ll disagree here. If you are a new team with not much DR4B expirance. Stick to a 1:7 gear ratio

Try to power the lift from the midsection, and also try to make sure your lifting bars are directly connected to the powered gears for extra stability.

Use as few axels as possible. Right now I have a dr4b that used to be on my robot that only has two axels in the entire thing and it could easily high stack caps. It would only have one axel, for the motor, but I used some low strength gears that I didn’t want to have to dremel out.

Instead of axels use screws. The correct way to make screw joints it to put the screw through the metal, then tighten a kep’s nut all the way down onto it. This makes a joint that cannot wiggle. Then place a three hole spacer (not strictly required but its good) on what is going onto the axel, and then place that onto the screw. Now place a spacer or washer onto the screw after your second piece of metal (the one with the 3-hole spacer), and then a nylock.

You can probably find a better youtube video explaining this but thats basically how to do it.

edit: I found the video showing screw joints. They are shown at the end of it.

+1 it leaves more room for error

As the lifts are lighter you don’t need to do what we did last year with the overly torqued 7:1 6 motor (4 torque 2 Hs) but I would instead recommend 4 motors 7:1 high speed. It takes a little work to convert and might not work with the way you set your bot up but inverse DR4Bs are super stable. If you make the center towers super close together and try to make the lift as thin as possible you will be able to go straight up easily. Also 2 encoders one on each side can help significantly. Have them try to have the same counts as they move and the lift should* go up straight.

are you saying that making the second stage encompass the first stage is better? my instincts tell me that you’d want it to be narrower as you go up…

Indeed. You want less cross space to increase stability as the lift raises. I’m not sure what this means, or if we’re misunderstanding something.

I’m confused: do you want us to put screw joints were the hs gears with the bars are?

Here is a diagram of what I mean along with a robot that has a dr4b on it that is pretty much the same as the diagram. The only difference between the two lifts is that the lift on the robot has an axel on the upper set of gears as they are non-HS gears and I didn’t want to dremel them.
DR4B Example.png

Personally I have built both types of DR4B lifts and a DR4/6B and the the narrower the whole thing is the better. I have found that for me I was able to achieve a narrower lift and more stable lift with the inverse DR4B

if you say so… never seen it done that way before.

Essentially We build a DR4B, You need to have more rubber bands if it wobles. The add a rubber band to the side that the robot doesn’t lean on, So if it leans right then put rubber band on left.
2)Your rubber bands get used to the streching so you must change them over time
3) We used 4 motors and a motor with a 6 tooth metal gear(The tinest one) to a 64 high strength gear to a 64 high strength gear.