Introduction: Center Arm Lift, a Knex Ball Machine Lift

Picture of Center Arm Lift, a Knex Ball Machine Lift

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

Picture of 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

Picture of Entrance

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

Step 3: Motor Section

Picture of Motor Section

This part contains the motor and some gears.

Step 4: Ball Track

Picture of Ball Track

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

Step 5: Sides

Picture of Sides

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

Step 6: Axle and Arms

Picture of Axle and Arms

This step contains the axle and the arms.

Step 7: Rails

Picture of Rails

The ball will roll to the center on the rails.

Step 8: Exit

Picture of Exit

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

Step 9: Finished!

Picture of 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!



KneXFAN200 (author)2017-02-02

Thanks! This will help!

With pleasure!

nerfrocketeer (author)2014-01-03

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

Sounds awesome, I can't wait to see it!
I have some lifts without the big yellow gear ;D

Do you have any without any gears? All i have is chain gears and those little tiny grey gears.

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).

hunter999 (author)nerfrocketeer2014-01-07

Here is some help ;) :


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 ;)


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.


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)


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.


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 :-)

That's some good help :p
Also, the blue motor is much slower than the green motor ;)

Ok, what is the fastest motor you know of?

12v motor. And battery motors: I think the green one.

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

Ah yes you're right. And is the green motor the fastest with 2 batteries?

Correct :-) whilst the blue has the most torque.

Shadowman39 (author)hunter9992014-01-09

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

Sorunome (author)Shadowman392014-01-18

Shouldn't the 12V motor have the most torque?

Torque isn't only about speed ;)

Shadowman39 (author)Sorunome2014-01-18

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.

Sorunome (author)Shadowman392014-01-18

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.

Shadowman39 (author)Sorunome2014-01-18

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

hunter999 (author)Shadowman392014-01-15

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

Shadowman39 (author)hunter9992014-01-15

I got that info from here. (I think you posted the same link somewhere on this Ible, lol)

hunter999 (author)Shadowman392014-01-15

XD Yep I could agree with you on that one whilst the green is the fastest, it has the least torque? :-P

Shadowman39 (author)hunter9992014-01-15

I think that's true, but that would be the silver one because that's the fastest of the single-speed motors.

hunter999 (author)Shadowman392014-01-15

Oh yeah just noticed that! For some reason most people use the green motor though for lifts like this one. I think its because they are the ones that come in the sets like for roller coasters etc

Shadowman39 (author)hunter9992014-01-15

Yeah, green, blue, and black ones seem to be the most common.

hunter999 (author)Shadowman392014-01-15

I have the black and blue, but not the green unfortunately. From seeing your epic builds, I'd say you have like at least 5 of each lol

Shadowman39 (author)hunter9992014-01-15

Lol, I like to use green the most. I think Sorunome has the most motors, around 40. And thanks! :-P

hunter999 (author)Shadowman392014-01-15

O.O 40! Wow thats a lot. I have around 10: 3 red battery pack motors, 2 battery motors (the ones we talked about above) , 1 trekker motor, 1 12 volt motor and 3 cyber motors. Also around 4 friction motors.

Sorunome (author)hunter9992014-01-18

Hm, let's see

17 red battery pack

3 12V

5 cyber knex

2 solar

those 4 from control-a-bot

7 re-wind

2 ripping rocket boosters

So not quite 40 :P

Also, funny how i don't have any newer battery motors :P

Sorunome (author)Sorunome2014-01-18

Oh, also, I modified quite a few of my red battery motors to be able to plug them in - i ran out of batteries too quickley >.>

Do they have the same power as before?

yep! I also made instructions on how to modify it over here:

Ha, cool!

Shadowman39 (author)hunter9992014-01-15

Ah, I don't keep track of my motors too much, all I know is that I have 3 plug-in motors and more newer motors than the old battery pack ones.

Really? It's a shame that I didn't know that -,-

Ah I didn't know that :3

Shadowman corrected me, the silver 2 battery one has the most speed.

The 12 volt motor is not necessarily the fast, but it has the most torque of all the motors.

It is also the fastest I think :p

The grey 2 speed motor has 240 rpm at top speed but the 12V only does 66 rpm :-P

Referance -

Ah haha :p

Ok, thanks!

Sorunome (author)hunter9992014-01-18

The Tower Helix Lift uses gears, a green gear in particular which is pretty important to get it to work, because of how the center is static.

Lol, i only ordered green gears for that lift xD

hunter999 (author)hunter9992014-01-07

also you can use a wheel lift if you like, since they require no gears too :-)

nerfrocketeer (author)hunter9992014-01-08

True, true.

I also had this concept for a vertical catapult lift that launches the K'nex balls up a vertical tube with a curve at the top. But first, has it been done?

I don't think it has been done before. And that's actually a very nice concept!

Thanks! I'm going to give it a try sometime this week.

hunter999 (author)nerfrocketeer2014-01-15

It sorta has in the ultimate big air ball tower. The air motor shoots the balls up the tubes which is curved at the top.

By all means Nerf, don't let this dis encourage you, go for it! I would :-)

nerfrocketeer (author)hunter9992014-01-15

Ah, I see, well the catapult couldn't get enough leverage or speed, so I have a different idea, involving a roller coaster. (It's still a ball machine lift, though).

hunter999 (author)nerfrocketeer2014-01-16

Would you mind if I take on this idea? I have some concepts on how to shoot the balls up. Here's a clue, I will be using this in it....

About This Instructable




Bio: 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 ... More »
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