Blue Mamba V2 [MOC]

[Daniel-99]

Hello Eurobricks!

 Here is a Blue Mamba V2 - a wild mix of energy and rigidity.

 

The story begins.

Several months ago I build a fast off-roader for the King Of The Hammers competitions. The main idea behind that car was the minimalistic transmission. Well, there were now gears in the transmission, but there were CV-joints at the front axle and they were very weak!

There was no way to fix that problem until one Russian AFOL comes with the custom wheel hubs with metal bearings and metal U-joints! These hubs allow to use a variety of RC wheels with 12 Hexes. Awesome!

 

I purchased a set of custom hubs, and started the development of the Blue Mamba V2. Before diving into details I want to highlight another principal change in V2 project. V1 Mamba was powered by Buwizz 3.0 unit, but it drowned with my mid-scale trophy truck this spring. So for V2 Mamba I bought a custom Lego-compatible compatible RC controllers “Wixy” provided by another Russian AFOL. These controllers allowed me to use all benefits of GeekServo and Powerful 3S Lipo with 2600 mAh capacity.

 

Bodywork.

The car has a minimalistic bodywork. All panels used as structural elements. There is a plenty of space for the cockpit if one would sort all the wirings. The only decorative element is a fake V6 engine located behind the cockpit. Currently I have no PF motor available to make the engine work, but I keep in mind such possibility.

 

Drivetrain.

Blue Mamba V2 is a true E-vehicle with 4 PF L-motors powering each wheel independently without any transmission. Custom wheel hubs with metal bearings and metal U-joints make the transmission totally undestroyable. My goal was to minimize the width of the car. But the complexity of the front axle provided a lot of restrictions, so I had to widen front axle by 2 studs comparing to V1 Mamba.

V1 Mamba has a steering motor located in the cockpit and linked to the front axle with new CV-joints. I replicated same configuration to the V2, but driving tests revealed big wobbling of the steering system, so I decided to place a GeekServo on the front axle (luckily it is very compact). A small regret is that GeekServo is not powerful enough for this wide and grippy RC wheels, It can not return them back if the car does not move. Likely, a positive caster angle of the front axle helps to back steering when car moves.

 

Suspension.

Mamba has 3-Link bridges at both axles with heavy-duty suspension arms. I had many attempts with the spring attachment. Finally, I understood that a responsive suspension requires a direct mounting of springs to the axles. 9.5 L shocks has very good springs (comparing to the soft 9.5 L one), but they were too hard for the car because all motors were placed on axles. An interesting idea came to my mind: why don`t you place these shocks diagonally? It works like a charm!

 

Control.

Car has a low center of gravity due to the placement of motors and 3S Lipo batteries. In addition, it has a proper wheel base and grippy tires, which makes the car very stable. Accuracy of GeekServo and RC transmitter provide a very smooth driving experience (though a stronger servo motor would improve the performance). Finally, 4WD helps to go through any terrain, such as sand, grass, etc…

The top speed of the car is about 8.5 - 9 km/h. So it is very interesting to play with it outdoors and take it for a walk, since it has enough speed to drive back and forth while person walks. I tested this car with 120 mm RC wheels. The motors have enough power to handle and increased load while all the other plastic components (such as steering elements) were struggling a bit... On my opinion, 95-100 mm wheels are the optimal solution for fast outdoor cars. From one hand they provide a decent ground clearance and able to roll over the bumps. From the other hand they does not provide a lot of stress to the Lego parts.

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Conclusion.

After multiple outdoor tests I conclude, that Blue Mamba V2 is the perfect Lego car, which is capable to go through any terrain with decent speed. It is strong and efficient and very controllable vehicle, which is pleasure to drive! Though It is too fast for trial. It is hard to go 2 km/h balancing between obstacles and barriers. But this is not a disadvantage, simply because each vehicle has it`s own areas of use.

 

 

P.S. Speaking about Wixy

Some of you wanted to know more about "Wixy" setup. So I placed all the component on the desk and marked them as follows:

1. Wixy units 
2. RC receiver 
3. 3S Lipo
4. PF motors
5. Geek servo

"Wixy" unit plays a role of an RC ESC unit, and it connects to the other electronic components in the same way:

• B-cable transmit the power from Li-Po batteries to the bottom PF connector (input) of Wixy units.
• A-cable feeds an RC receiver for Wixy units and translates the controlling signal at the opposite direction. Unusually for drive the "Channel 2" is reserved.
• PF motors get connected to the top PF connector (output) of Wixy units.
• GeekServo gets connected to the receiver. Two Wixy units provide enough power to feed GeekServo, otherwise I can plug and extra power from one of B-cable outputs (there is one specific 3-pin one).

 

At the second picture all components are connected. 

It is important to note, that a Single "Wixy" unit can transmit only 3A to the motors, but it is the maximal power which PF connectors can handle . So you have to use one unit per Buggy motor. Luckily, 3S Lipo as an enormous amount of power, so it can handle 10 Buggy motors easily!

 

Hope I cleared out the "Wixy" setup for you, but if you have any questions left, do not hesitate to ask them!

 

 

 

 

 

Edited August 17, 2022 by Daniel-99