K'NEX Mobile Crane Truck (versions 2 and 3)




About: I don't always make instructables, but when I do, I prefer to use pictures. Stay instructed, my friends.

Coming off from the previous crane truck, I sought to improve its functionality and I have made some improvements:

In version 2 and 3:
(+)the crane boom is able to stand by itself due to the addition of a motor
(+)there are two sets of wheels that steer
(+)crane structure is able to rotate somewhat freely
(+)realistic design compared to the first truck
(-) still no feasible way to have a multi-part boom or real structural pneumatic/hydraulic support

Version 2 only:
(+)a total of 4 sets of wheels, giving it 8 total
(+)motorised steering (albeit a lot of friction)
(-) a disproportionate length and unnecessarily heavy; crane structure is not exactly "centered" on the truck bed, and the truck's center of gravity is closer to the vehicle's rear

Version 3 only (INSTRUCTIONS NOW AVAILABLE https://www.instructables.com/id/KNEX-Mobile-Crane-Truck-v3-Instructions/):
(+)looks more akin to a real mobile crane in terms of proportions and center of gravity.
(+)a total of 3 sets of wheels--front and rear set are on a coordinated steering
(+)the ability to implement outriggers was definitely a plus.
(-)the boom was less able to lift itself and still needed some help; the cause was from the gears not catching and thus slipping.

Due to the amount of hours I work during the week, I will need to set aside an entire weekend to post instructions. Thank you for being patient and stay tuned!

As for the project itself, creating a fully functional mobile crane in the form of K'NEX is becoming extremely difficult and approaching impossibility. The most difficult part of this idea is coming up with a) a method for building a rising boom that is not only able to stay up, and can also lift a mass, but one that is not very heavy, or b) having enough power with the small motors to raise a strong boom and lift a mass. In this model, I have opted for option (a) due to the constraint of the vehicle size. Option (b) would force the model to be disproportionate to its wheels, since crane booms in real life are about 1/4 the width of the vehicle width.

Comments and feedback are much appreciated! I am anticipating a version 4 as soon as the epiphany train arrives.

Credits go to the following for ideas:
https://www.instructables.com/id/Knex-Supercar-Instructions/ the K'NEX Supercar for structural support
http://www.jenniferclarkbass.com/lego/demag_crane.htm this website containing scale LEGO mobile crane truck models for the inspiration and idea.



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    13 Discussions


    8 years ago on Introduction

    First off ... awesome crane's :)

    I've made version 3 and am attempting to make version 2 from the pictures you have. Do you have any other pictures of it especially of the steering as i cannot work out how to get the two axle's to turn the same direction :/

    1 reply

    Reply 8 years ago on Introduction

    Thanks! Sorry for the late reply. I got a new one coming up that will hopefully address that issue, but for the time being, if you got one axle to turn, just build another one like it and extend that turning shaft.  Hopefully the schematic below helps.


    8 years ago on Introduction

    Instructions? Please post some thanks! Anyway great write ups..


    8 years ago on Introduction

    i also made one mobile crane if you want check every day if it is there


    8 years ago on Introduction

    would you please send me some insteructions for this crane because i made one but yours looks better than mine, and by the way would you please also send me some photos because i really like your mobile crane truck


    Reply 9 years ago on Introduction

    Thanks! Yes, it can be turned sideways; I didn't have enough room at the time of photographing to rotate the crane.


    I am making a knex crane boom, funnily enough inspirend by gun magazines, I thought that if you put a small magazine (long) into a wider one , then that one into another wider one, then, with string, you could have an extending boom.