[MOC] LEGO Technic Complex Heavy Duty Multilink Suspension System Trial for LEGO remote control vehicles

[Kamil]

LEGO Technic Complex Heavy Duty Multilink Suspension System Trial for LEGO remote control vehicles (MOC)

 

Aims: This experimental suspension system here was intended to be used as a front axle of a tough 6x6 Lego remote controlled off-road vehicle. The reason of constructing this system is to decide whether it would be appropriate to use such a suspension system in a remote controlled 6x6 LEGO car that I want to build in future. In short, I wanted to verify the system I had in mind. The aimed specifications of the suspension system are:

1. Soft suspension for off-road use

2. Long suspension travel

3. High impact resiliance for off-road use

4. Being capable of maintaining its integrity for off-road use

5. Flexible enough for off-road use

6. High ground clearence for off-road use

7. Reasonable turning Radius

8. Reasonable powertrain to transfer 25-30% motor power to the front wheels (intended to be used with  clutch gear(s), and remaining power is intended to come from the rear 4x4 wheels).

9. Correct geometry turning of front wheels

10. LPEpower*^{Youtube (https://www.youtube.com/watch?v=NBw44g2uEis)} multilink suspension pivoting adaptation for turning the big wheels in tight fender spaces  to prevent the wheels from hitting the fender while turning left and right

11. Having gear reduction units for better power transfer to the front wheels

12. Having neutral camber when touching the ground

13. Obtaining a positive caster angle by connecting the main chassis and this suspension system at an angle

 

The Suspension System:

The suspension system is approx. 280 mm wide and 140 mm high. The sytem is designed for 15038 rims / 23798 tires.

Figure 1 Width of suspension system

 

Figure 2 Height of suspension system

 

Overall view:

Here the suspension system is shown from different perspectives.

Figure 3: Front view

 

Figure 4: Front view with steering right

 

Figure 5: Rear view

 

Figure 6: Top view

 

Figure 7: Side view

 

Figure 8: Bottom view

 

The Youtube video of this suspension is also included below. Many details were given in the video:

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https://www.youtube.com/watch?v=suqPfu8HZDo&lc=UgzrsbQ_SmJRpOu-s-p4AaABAg

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Results and Discussions:

Each topic given in the “Aims” section will be discussed one by one in the same order.

1. The softness of the suspension system was found to be adequate (see video)

2. Suspension travel (22-30mm) is fairly well, however this does not fully meet my expectations

3.  This topic may be tested once a complete remote controlled vehicle is available to perform an off-road test. The weaknesses then can be determined. No further information is currently available at this time.

4. The integrity was maintained during the tests in the video. No further information is currently available at this time.

5. The suspension and the steering system seems flexible enough to work in off-road conditions (see video)

6. This suspension system has approx. 48-50 mm of ground clearence (see Fig. 9). This is fairly well but remains below my expectations. The restriction here is the short length of the control arms (see Fig. 4). Some additional spacing was needed for the LPE type pivoting, and the gear reduction units. As a result, the control arms are shorter.   

 

Figure 9: Ground clearence

 

7. This topic is the highest shortcoming of this suspension system (see video). Turning Radius is fairly limited due to the structural nature of the multilink pivoting, see Fig. 10 and 11. Also the bottom steering link is using the maximum space (see blue circle, bottom in fig.10), so this is another limitation here.    

Figure 10: Turning radius limitations. Multiling pivoting limitation (blue circle, up), and bottom steering link space limitation (blue circle, below)

 

Figure 11: Multiling pivoting limitation

 

8. The differentials and universal joints used here can be replaced with new generation stronger Lego ones. Then double differentials would be eliminated. The use of 46490 hub here may require some design changes. 

9. Correct geometry turning slightly exists on the system, but it is barely visible by eye even when measured by rulers (see Fig. 12).

Figure 12: Correct geometry measurement

 

10. LPE*^Youtube multilink suspension pivoting is capable of keeping the wheels in place during manoeuvring

11. Structure of the gear reduction unit ease angular constructions, and this provides to move the upper pivots through the center of the vehicle. As a result, pivots are in the desired position.

Figure 13: Angular construction of the gear reduction unit’s upper pivot

 

Figure 14: Closer look on the gear reduction unit

 

12. Neutral camber gives a nicer and tidy look to the suspension system. However, when the entire suspension system rests in neutral position, it has neutral toe. When suspension is pressed downwards, a slight toe-in appears. I think, slight plays may be expected for such a complex suspension system. 

13. Positive caster can be obtained by connecting the suspension system to the chassis at an angle.

Figure 15: Positive caster construction

 

Conclusions:

It would be fun to watch this complex heavy duty multilink suspension system on a RC Lego vehicle while working. Besides, it has some limitations and plays due to its complexity. For a 6x6 vehicle, the rear two wheels must also be steerable to obtain a proper turning radius. This suspension system also consumes a lot of space. In my opinion, this system becomes an over engineered one when compared to Lego X-treme off roader or similar vehicles. 

 

Additional images:

Figure 16: Multilink lower pivoting and universal joints

 

Figure 17: Double differentials and steering lower arm

 

Figure 18: Left steering setup from above

 

Note: This suspension system was built by imagination only. No computer aided design or plan exists.

 

Thanks for watching 

Edited 13 hours ago by Kamil