1 motor 4 bar

Hi. Is it possible to make a basic 4 bar to lift a mobile goal with no struggle with normal axle? I do not want it to be too slow, and I have no access to long high strength, and they have their own issues too. Thank you for replying.

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if you build it properly, yes it’s possible, though it might be difficult to prevent axle twisting without HS shafts.


Hey Connor,
Fortunately, it is very possible to make a one motor four-bar. It is slightly more difficult with the lower strength axles, but still very doable. The key is to run a 12 to 60 (with a red motor) or possibly a 36 to 80 (with a green motor) if you have the space. Both speeds are a perfectly acceptable speed to run a lift. Since you are working with low strength axles, it is important to have a bearing on both the outside and inside of the bars. This will negate a good amount of bending you would typically see when using low strength axles. Any lift speed between 30-40 rpm gives enough torque and is much faster than you might think.


I would strongly advise against a 3:7 ratio on 200 rpm, it will be far faster than you’d ever want it to be, but very weak that it could only work with very short lift arms, very high build quality, and an absolute dependency on rubber bands.

Depending on the length of your arms, I would go 1:7 on 100 rpm or 1:5 on 100 rpm.


Ok. Thank you for the help. I will work on that right away

Sorry about that, I was thinking 12 to 84 on a green motor, which I believe should work. 36 to 84 with a red motor should work as well.

Currently, with everything as it is in the pictures, at 100 rpm, on a green motor, it does not work. I tried whatever I can think of. Any suggestions?
Thank you for reading!

setting a green motor to 100rpm does not increase the torque. By 100 rpm, we’d meant to use a red motor cartridge to halve the speed but double the torque compared to a green 200 rpm cartridge.


Oh. Lol. That is my fault. I will try again!

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make sure to add some more rubber bands to the 4 bar but your setup should work pretty well.
If not
Drills are fun

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increase the gear ratio you can compound it if your already at the 12 to 84.

that could be an option, you would want to screw the gears together because a compound ratio might bend an axle by the motor.
something like 1:7 and then attach a 36t to the 84 w/screws and then 36:84 and the 84 that connects to the bar

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We did a 1 motor 4- bar like this, it was fairly fast and had little to no struggle ( I believe it is a red cartridge)

Full robot: 7996B mid-season reveal (videos coming soon)

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That gear ratio should be able to lift with a 100 rpm motor easily. We use 100 rpm with a 12 to 60 and we have no problems, you are using 12 to 60 so you should be fine.

You might want to look into how you’re retaining this shaft. It looks like there is nothing holding the shaft in the motor

I wouldn’t be surprised if you had unnecessary friction here too from the gear being squeezed between the spacer and the motor. In fact it looks like the gear is being leaning towards the left


We fixed that after this picture, we put a small c channel over that shaft collar to stop it from falling out. It never fell out, but just to be safe we added that.

That is just the angle of the picture, we noticed that it was close, but it never rubbed the spacer, I think the spacer wasn’t bigger than the gear, but I can’t remember

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