Reverse Double 4-Bar Help AND Critique

I’ve just finished my first prototype for a Double Reverse 4-Bar. I’m looking for some constructive criticism. Some problems I’m having now are the center gears clicking and catching at the apex, I’m also having some problems with the two sections of the lift getting out of sync occasionally. I’ve attached a link to a video of the lift moving from different angles.

Well your best bet would be look through different youtube videos from skyrise and see how the better performing rd4b’s are built. Just from looking at yours though, make sure you use bearing blocks at every joint. Also, don’t cantilever your gears(support from only one side). It creates excess friction and it isn’t as stable. And lastly, use two sides to your lift, not just one. Its a lot more stable, which is key with this type of lift.

The gears are skipping because they are only supported on one side. You want to have the gears sandwiched between 2 C-Channels with bearings, the easiest way to do this is by using standoffs between the two.

Cantelevering is not a good idea on a lift most times. Shoring up both left and right sides of the lift with another braced piece of metal will go a long way.

The clicking may be alleviated by using rubber bands to assist the lift. As you lift higher and the lift get vertical, the weight distribution changes a bit. The first joint where you have the big motors carries a bunch of weight. You could also be getting some torsional twist on those points as you lift up and that coupled with the cantelevering could be causing some separation of the gears.

Remember the gear touch point is pretty small. It’s just along the face of the gear teeth. You need good contact there to transfer the force.


Is the DR4B lift for this years game? maybe you could find some help in my teams reveal from last year which is still in my signature. check it out!

As has been said, don’t cantilever in the final build and if you are planning on lifting another robot with this lift, us HS shafts, gears and plenty of cross braces. cool idea!

hope that helps.
good luck!

that probably wont lift a heavy load in it’s current form. once you get a load on it it will start bending shafts and such. that what is so difficult about rd4s, the more bracing you add the heaver they lift gets and the heaver the lift gets the more bracing you need.