Center Arm Lift, a Knex Ball Machine Lift




About: Hey! I'm Sandroknexmaster. I like building with knex, especially ball machines. I live in Belgium. I speak Dutch, but also English and French. I hope you like my stuff, and like always comment, rate &...

Hi knexers!

Here are the instructions for the third new lift in my knex ball machine Paradox.
The Center Arm Lift works good, and it has a low piece count (except for silver spacers).

This lift was originally invented by MechanicalCreationMaster in his ball machine Krypton (Original name: Freefall Wheel Lift)
The Center Arm Lift is based on this concept, so a lot of credit goes to him.

If you build this lift, read every image note! It will help you a lot!
If you have any problems or questions, feel free to comment or PM me.

Thanks for building or watching!



Step 1: Piece Count

If you want you can count the pieces before you start building.
Here is a list with all pieces included in this lift, named by their original color:


Green: 24
White: 8
Blue: 49
Yellow: 14
Red: 45
Grey: 25
Long flexi: 4

Total rods: 169


Dark-grey: 11
Light-grey: 4
Orange: 4
Red: 19
Green: 8
Yellow: 29
White: 13
Purple: 41
Blue: 5

Total connectors: 134


Blue spacer: 23
Silver spacer: 66
Tan clip: 9
Blue clip: 2
Y-clip: 10
Small blue gear: 2
Medium red gear: 1
Big yellow gear: 1
Motor: 1

Total other: 115

Grand Total: 418

Step 2: Entrance

The balls will wait on this track to enter the lift.

Step 3: Motor Section

This part contains the motor and some gears.

Step 4: Ball Track

The ball will roll on this track when the arm pushes it up.

Step 5: Sides

These sides will keep the ball from falling of the arm.

Step 6: Axle and Arms

This step contains the axle and the arms.

Step 7: Rails

The ball will roll to the center on the rails.

Step 8: Exit

This is the exit track. This is the last step!

Step 9: Finished!

Your Center Arm Lift is finished!
Always slide the switch of the motor to the left!

You can always send me a picture of your Center Arm Lift, so I can add it to this step.

Thanks for building or watching!




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    71 Discussions


    5 years ago

    Cool man! My NK Sideliner is finished, and I modified your green path in it. I would have used one of your lifts but had to come up with my own because I don't have a gigantic yellow gear of doom. :( :P

    17 replies

    What do yo mean with chain gears?
    I don't have any lifts without any gears, but if you have a slow motor I think you can attach it directly to the axle (I'm talking about the Center Arm Lift only)

    The black gears that link into a Knex chain, they come with the roller coaster sets.

    But ok, if i build this ill attach it to the axle (i have a green motor, which is slow).


    Here is some help ;) :

    OPTION #1

    Inverted Double Helix Lift - by Shadowman
    This lift is great (for you) since it doesn't use gears

    However, I'm guessing you don't have tubing, and thats why I thought ahead ;)

    OPTION #2

    Tower Helix Lift - by Sorunome
    Although this has no instructions, I reckon you might be to rebuild this. It uses the same concept as the above lift, but with orange bendy rods instead.

    OPTION #3

    Right ok, you know the black gears you said have, are they the ones below? If so, you can build a vertical chain lift like in the photo below (taken from Galactic)

    OPTION #4

    Like Sandro said above, try and run a lift directly from the axle, using that slow green motor.

    A personal favourite lift of mine I think you should use is this. I am not sure if this will be too fast for IaC ball lift, but this lift is very VERY reliable - I have made it before.

    OPTION #5

    The Slider Lift - by Mathsboy314
    This was featured in Sandros ball machine Paradox I believe and it uses NO gears at all and is quite piece friendly to me :-)

    I really hope these help Nerfrock'! Message me for any more problem - I'm happy to help :-)


    um err sorry, but your wrong. With batteries, it is the 2 speed motor which requires 4 batteries (The one in my whisk instructable)


    Reply 5 years ago on Introduction

    Wait, the silver one has the fastest speed. :-P And wouldn't the black motor have more torque since it's the slowest?


    Reply 5 years ago on Introduction

    I don't know, but we were only talking about the newer battery motors. :-P And the black one having the most torque is assuming that all those types of motors output the same power but gear it to different speeds.


    Reply 5 years ago on Introduction

    Well, pretty sure that the 12V one has the most torque, because it is also the one with the most power because of having the most volt and, pretty sure, also the most ampers.


    Reply 5 years ago on Introduction

    Yeah, that one has the most torque, and the newer-battery motor with the most torque is probably the black one.


    Reply 5 years ago on Introduction

    hmm good point :-P I'm not too sure. I can't remember where I heard it from, but I though the blue was. I think your right though :3