After completion and playing with the Leopard for a few months, I noticed the model had a few shortcomings which I wanted to eliminate with this version.

These include:

• Suspension oscilations at high torque
• High center of gravity
• Instability on rough terrain at high speeds

Most of these issues were due to the usage of the torque tube suspension which is simply too heavy and unresponsive at high speeds. What I needed was to replace the live axle suspension with independent suspension while keeping the articulation needed for offroading.

Here's what I came up with:

Let's break down the suspension to it's basic components to better understand how it works:

Colored green are the main shock absorbers. These caryy most of the wight and provide a high suspension travel

Colored orange are the gearbox transfer arms which fix each perpendicular gearbox firmly to the suspension, thereby reducing friction and fixing the U joints to keep them from popping out.

Colored black are the side beams which help guide the transfer arms and hold the suspension together

Colored in red and gray are the two independent drivelines powering the wheels.

Finally in transparent, the suspension arms are made as long as possible for maximum suspension travel.

 

I built the first version with this setup, but soon discovred a flaw. The torque from the drivelines would push the suspension arms down, causing the suspension to stop responding (indicated with red and grey arrows in photo above). In order to solve this problem I added the suspension bridge above, colored in pruple.

The suspension bridge performs the following functions:

• Compensation of the driveline torque
• Supports 20% of the model's weight
• Improves articulation when going over rough terrain

 

With the suspension solved, I turned my attention to the chassis. I wanted a model with high torque and high speed. To achieve that I installed a two speed gearbox for each independent driveline powered by a total of 4 RC motors:

 

Finally a very sturdy chassis based on frames was built to support the model. Each axle was given it's own independent steering with servo motor and each driveline has an M motor for switching gears. This redundacy means that even if half of the model breaks down, it can still drive back home.

 

Next step was building the model in real life. Thanks to ForwART's custom stickers the exterrior really came to life:

 

The doors can be opened, revelaing two seats and the steering wheel:

 

Each wheel has over 6 cm of wheel travel, allowing the Tiger extreme articulation rivaling live axle setups:

 

And let's not forget the most important photo of them all:

 

Finally, since there is only so much I can tell in words, enjoy the video experience:

 

As usual the LDD file of the model is available by clicking the photo or link below:

https://www.bricksafe.com/files/Zblj/tiger-4x4x4/Tiger 4x4x4.lxf

To summarize, compared to the previous Leopard, the Tiger has the following improvements:

• Improved stability due to the independent suspension and low chassis
• Higher top speed due to the gearboxes
• Eliminated suspension oscilation
• Improved performance at high speed thanks to lighter and more responsive independent suspension
• Improved maneuverability thanks to all wheel steering

Sadly there are also a few drawbacks which I plan to fix in the future version:

• When pushing the model hard in Ludicrous mode and in low gear the 12 tooth bewel gears can get damaged and need to be replaced
• Low steering angle (18 degrees)
• Because only one servo motor is used per axle, steering is more prone to be bumped out of center.

 

 

 

Edited June 2, 20195 yr by Zerobricks

Nice! I've been dragged into the rc hobby just recently and being a happy but skinned owner of a short course truck, this creation warms my heart.  My first thought during the video was that the bevel gears must be suffering, then scrolling down you've confirmed that. Still it is a respectable achievement regarding the performance. Sadly, plastic has it's limits. Nice job, what a monster! 

21 hours ago, Attika said:

Nice! I've been dragged into the rc hobby just recently and being a happy but skinned owner of a short course truck, this creation warms my heart.  My first thought during the video was that the bevel gears must be suffering, then scrolling down you've confirmed that. Still it is a respectable achievement regarding the performance. Sadly, plastic has it's limits. Nice job, what a monster! 

Than you for the praise. I hope to improve the model with the use of the new hubs and joints, and no longer requiring use of bevel gears.

25 minutes ago, Zerobricks said:

Than you for the praise. I hope to improve the model with the use of the new hubs and joints, and no longer requiring use of bevel gears.

If those new parts live up to our hopes, they gonna take the lego offroad to a new level.

My eyes are watering... Excellent model, that articulation is wonderfully huge. Add in the speed, and this is just good old fun.

EDIT: Just finished the video... Was that a wheelie?!

Edited June 3, 20195 yr by Leonardo da Bricki
Long video...

That looks like FUN!!! That's an awesome creation. WOW!!

Thanks to a Chinese fan by a name of Kyon, the instructions for the Tiger 4x4 are now also available in Stud.io

https://bricksafe.com/files/Zblj/tiger-4x4x4/Tiger 4x4x4(1)_Copy.io

Edited April 7, 20204 yr by Zerobricks

21 hours ago, Zerobricks said:

Thanks to a Chinese fan by a name of Kyon, the instructions for the Tiger 4x4 are now also available in PDF:

https://drive.google.com/open?id=1iub0olYMmVF50ZHELJHo5OIqw_8YRZri

And in Stud.io:

https://drive.google.com/open?id=1s-L5n1L8Pgr0weH3Z03Y4rko9qeQD0_w

This is a 6X6, quite different from your design here.

1 hour ago, 1963maniac said:

This is a 6X6, quite different from your design here.

Indeed, I posted a wrong link.

Here is the correct link to the .io file:

https://bricksafe.com/files/Zblj/tiger-4x4x4/Tiger 4x4x4(1)_Copy.io

 

Hello, ı couldn't find its part list. Can you help me 

WOW! Very impressive!

It seems to be a lot of fun and it could be an alternative for a RC Offroader...

Thanks for the instruction!

On 6/2/2019 at 2:37 PM, Zerobricks said:

These include:

• Suspension oscilations at high torque
• High center of gravity
• Instability on rough terrain at high speeds

 

 

wouldn't u want stability on rough terrain at high speeds and a low center of gravity 

 

17 minutes ago, MY1 said:

wouldn't u want stability on rough terrain at high speeds and a low center of gravity 

 

Given enough space I could have given it adjustable suspension height which would increase stability even further at high speeds.