DR4B Problems

It seems like I only post about DR4Bs these days…
Yesterday, I built one side of a DR4B.

Here is the link to pictures / videos.

The gears are bending, there’s so much friction and its unstable and lots of motor power is lost from the bad build.

Can you suggest any way to improve it? I seriously have no idea how to do this.

Use latex tubing to assist the motors, looks like the motor is struggling a bit ??

Also the lift is over hung, maybe replace the motor to the other side so it would not tilt as much

From my experience, green inserts work better than the black ones for 72 tooth gears

Definitely need some assistance (rubber bands or latex tubing) on it. The motor is definitely struggling some.

As far as stability goes, most of your problem right now is that you only have 1 side built. Once you build the other side and brace both of them together it should become much better.

There’s also some slop between your bottom gear and the bottom 4 bar. I would suggest you build the gearbox in such a way that you can mount each gear directly to the c channel pieces on the top and bottom 4 bars. This will help with the slop and result in it lifting more linearly.

Hope this helps!

I’ll start from the bottom of the lift and then work my way up stating the improvements that could be made at each point.

The lift tower looks like it isn’t perpendicular to the ground. This can heavily contribute to issues as it creates another point of weakness for the motor to power through.

It looks like you have already attached points for a triangular tension system. Rubber bands are pretty much mandatory for any motorized lift, so I would attach those as well. Don’t put on too many since there are no cross supports due to the lack of the other side of the DR4B. The fact that you are already using 1 x 1 pieces for the lift can create significant weakness.

The standoff that you are using to connect the 84 tooth gear to the 1 x 1 piece on the bottom half of the lift seems to be composed of 2 standoffs connected together either by a coupler or a long screw. If possible, buy the standoff size that is equal to the length of what you have shown. From what I see, you have a 0.5 inch standoff coupled to a 1 inch standoff (I’m eyeballing it). To save weight and money, you can use a 0.5 inch spacer instead of the 0.5 inch standoff so that the screw runs through smoother.

The bottom 84 tooth gear looks really funky. It looks like you are trying your best to incorporate screw joints at any place you can, however the distance in-between your gearbox is longer than the legal screw length leading you to try some strange techniques. I would just use a really long shaft to go through the gear and the 1 x 1 which creates the top portion of the bottom 4 bar. Same goes for the top 84 tooth gear. I can’t tell what insert is being used on the top gear, but really either insert will work for the intensity of this game. Trust me, the screw joints and insert types won’t make or break your overall performance.

I am heavily concerned about that potentiometer placement. The wiring can be tricky and your technique to use the bar in order to keep the potentiometer in one position seems unnecessary. I would mount it on the outside of the gearbox on the long shaft you have sticking out from the motor. It looks like you could easily fit screws to hold it in place if the head is on the inside of the gearbox. A much more effective idea would be to mount the potentiometer on the same shaft as the top 84 tooth gear on the outside of the gearbox if you choose to switch to shafts. This not only eliminates the bar you have to hold the potentiometer in a constant position, but also a less sensitive range of values when collecting sensor data from the potentiometer. If you do choose to pursue this technique, make sure to use the square inserts on the 84 tooth gears so that the shaft is actually rotating.

Another thing that may be contributing is the bearing mount that you have going on within the gearbox on the side using the 1 x 1. Bearings do not properly fit in that position on a c-channel unless they are sanded. If you don’t want to go through the trouble of sanding bearings to properly fit, using a normal 2 wide c -channel rather than the 1 x 1 will solve that problem without contributing much as far as weight goes. Just know that using un-sanded bearings in that position on the 1 x 1 can cause significant amounts of friction.

You may want to look into putting a bearing on the motor. It looks like there is one directly contacting the motor, however this can cause greater amounts of friction since there is no guidance tool to make the motor fit into it properly. If you put the bearing on the other side of the c-channel, however, the out-dents on the bearing will “click” into the c-channel and the motor screw holes will lock in on the other side as well, leaving more room for a shaft collar and creating less friction. I’m not sure if you can fit a bearing in this position since it looks like it may hit the 84 tooth gear, but once the gear is straightened out you have just enough room to fit a bearing in the place of the spacer spacing the pinyin gear away from the c-channel.

I can’t tell if this is because of the lift tower not being straight, but make sure those 84 tooth gears are properly meshed together. There should be a point within the cycle of the lift whenever it is going up or down where the c-channel connected to the top 84 tooth gear and the c-channel connected to the bottom 84 tooth gear are parallel.

Aside from that, it looks like a solid start. If you don’t take any of this advice and build the other side of the lift with tension and supports between the two, this will already show a more stable build. Since the motor is causing an imbalance due to uneven weight distribution, it will continue to contribute to the issue until supported by the gearbox of the opposite lift side.

Hope I helped!

I think the advice given above should be quite useful for you.

Another part of the lift you may want to check will be the high strength 84 teeth gears. When I was using them during In The Zone, I realised that some of the gears are defective (I identified the same problem during NBN but I thought they would have already been fixed). They are slightly larger than they should be. You can compare the high strength 84 teeth gears to the low strength ones to see if they are slightly bigger than the should be.

I do not believe there is anything you can do because this is a manufacturing error, so you probably have to screw together 2 of the low strength gears in order to get a gear with the same thickness.

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@ItsAlex Thanks, I will make the other side later so the tilting shouldn’t be a problem after the other side is made… I used green inserts because for some reason, black screws goes into the green inserts smoothly but the silver screws don’t go into the green inserts unless pushed hard or screwed in. Do you have any ideas why that’s happening?

@2158R_Arrash Thank you, that was a LOT of information. I will follow all your advices. But for the Bearing flats, I have to keep on using 1 x 1 because of the weight and the motor limits. We are only capable of using 2 motors for the DR4B 1 side each according to plan… But thanks anyways and I’ll keep this reply for more uses.

@Tring I didn’t know that. Thank you, I will change the gears.

Make a triangle brace like this one to support your tower.
Screen Shot 2018-06-23 at 11.21.31 AM.png

Seems like the main issue is that center gearbox. One thing that I found very helpful is to make the center gearbox as 1 large and robust piece instead of building separate sides. I will attach a picture of my ITZ worlds robot to show you what I mean but I like to build it by having 2 horizontal c-channels connected with 4 vertical c-channels to make a very sturdy frame. I like to have everything in between the pockets created by the vertical c-channels because it forces me to connect the c-channels directly to the gears (which I have found to work better, not entirely sure why) and gives a challenge of having the shortest shaft length possible. I was able to fit everything within 4 holes horizontally this year.