[MOC] EAGLE an RC Trophy Truck

[Daniel-99]

Hey, guys! 

After a 3-month brake from Lego, I am glad to show you my new RC trophy truck, called Eagle. I apologise for the quality of photos and I will try to improve them later after I will get myself a studio light. I will also make a proper introductory video when I will get enough outdoor footage.

Spoiler

Features

• Responsive long-travel suspension with 4-link live-axle at the rear and double wishbone at the front
• Brushless motor A2212 1200 kv for propulsion, Geek Servo for steering, 1500 mAh 3S Li-Po for power
• Strong and efficient transmission with metal U-joints and metal bearings.
• Great ground clearance for outdoor use, 95 mm RC wheels
• Light-weight bodywork

 

Experience and Inspiration

I guess that nobody will be surprised If I would make a confession that I have a deep passion for Trophy trucks. This type of vehicle suits the best for the role of a fast RC Lego cars which are build for outdoors. Indeed, outdoor environment is always rough and "bumpy" for Lego cars. I took my inspiration and first experience form several well-known Lego builders, such as:

• Sariel
• RM8
• ZeroBricks
• GooberReboot

Through the last 3 years of intensive engineering I made a few attempts in building myself a "proper" trophy truck. Each of them had it`s own features and technical problems:

• Heavy-duty Trophy Truck: RWD, 2x BM, 2x Buwizz 3.0 units, 95mm wheels. Problems: "big scale" which caused a serious load for motors, over-tilted front caster.
• Phantom: RWD, 2x BM, Leshy control unit, 85mm wheels, mid scale. Problems: lack of power from Leshy unit, lack of articulation at the rear, plastic wearing in the wheel hubs.
• Wilde Beast: 4WD, 4x BM, Wixy RC control + 3S Lipo, 95mm wheels. Problems: "big scale" which caused a serious load for motors, indep. susp. with a questionable geometry.
• Falcon: 4WD, 4x BM, Wixy RC control + 3S Lipo, 75mm wheels. Problems: indep. susp. with a questionable geometry, overheating of motors at the maximal RPM.

About a year ago I switched from Lego Buggy motors to a Brushless motor (for the reasons which will be covered later). This was not an easy switch for me and I had to learn some RC electronics theory and find the proper ways of using brushless motors with Lego. My latest RC cars with Brushless motors was:

• Unimog trial truck
• Pathfinder SUV
• Hornet 4x4 buggy

With pathfinder and Unimog projects I studied the 4-link live-axle suspension geometry, while with Hornet project I found the way to achieve a proper suspension and steering geometry with my custom wheel hubs. With this projects completed I get myself all cars I need.

- What should I build next?

With such question in mind, I faced a deep burnout from Lego, so I decided to take a summer brake. Hot summer days returned me my passion for Lego, and I had a plenty of time to plan a new project. I felt myself ready to make another attempt in building myself a "proper" trophy truck. That is how the story begins. 

 

Electronics

With my latest truck Falcon I reached the limit of what Buwizz motors could handle. Some time ago there was a discussion about efficiency and power-to-weight ratio. I would not resist that with the growing number of motors and Buwizz units, one could get a better power-to-weight ratio, though such a way faces the problem of plastic-weariness quite soon. With the growth of the number of motors, also grows the size of the car and it`s total weight, which get distributed to the four Lego plastic wheel hubs! I faced the plastic-weariness problem of Lego hubs with my Phantom truck, and solved it by purchasing custom wheel hubs with metal bearings, which I were used in the Falcon truck. Moreover, there was no gearing in the transmission of the Falcon truck: each wheel was connected to it`s own motor via driveshaft with metal bearings. With 4x Buwizz motors on board, powered by strong 3S Li-Po battery, Falcon had a great power-to-weight ratio. Through multiple tests I found that It can not handle full throttle for more than 45 seconds due to the rear motor overheating. It was pretty clear to me that RC Li-Po could easily overfeed 8 or even 12 motors with power, so there was no sense in adding more BM motors. 

Likely to me, one Russian AFOL developed a 3D-printed housing for Brushless A2212 motor which allowed to use it with Lego. I purchased two sets from him, and mot I have 100% RC setup. There was no problem with the lack of power or motor overheating anymore, but it was a real challenge for me to overcome this energy!

 

Transmission

With BM motors it is very natural to distribute the torque among axles \ wheels, by having separate transmissions to each axle \ wheel. But with Brushless motor I had to use "realistic" transmission, since there is only one output with a plenty of speed and torque. Despite the fact this motor is a baby-motor in the world of RC cars, It has enough power to twist Lego axles   with instant reaction to the throttle. Custom 3D-printed housing has a 4:1 planetary reduction, but the speed of the output is enough to cause gear-melting. That is why the following decisions were made:

• use metal U-joints all around, most of them have a 3L lego axle glued from one side to prevent them from falling off. 
• use silicone grease to lubricate the planetary gear in the motor housing and some external gearings.
• use custom parts with metal bearings to separate the transmission from the car frame.
• use carbon-fiber axles in the central driveshafts. 

The new Eagle truck has a very simple RWD transmission with a single "external" 14:23 gearing in the differential. Recall, that the 3D-printed motor housing has a 4:1 gear reduction. So the motor is connected to the differential via carbon-fiber driveshaft. From the differential power translates to the 95 mm RC wheels via half-axles with metal U-joints. The whole transmission sit on the metal bearings (custom wheel hubs with metal bearings, custom 5x7 frame with metal bearings for differential housing, motor output passes through the connector with the metal bearing). Surely you have noticed that I lifted the central differential by one stud over the wheel axle in order to achieve a higher ground clearance! 

Which differential to use RED or YELLOW?

RED differential has a 28:12 reduction which reduces the load from the driveshaft and the motor. Moreover, such gear ratio is more realistic. On the other hand, YELLOW differential has bigger teeth so it is stronger. But more importantly, is that YELLOW differential is 125% more efficient than the RED one, since it has bigger gears and does not scratch the 5x7 frame under the load. In fact, I am using a custom torsen differential with 23-tooth gear. It also does not scratch the 5x7 frame and hold half-axles much stronger than the original YELLOW diff.

 

Suspension

Trophy truck is all about suspension, and it was the most challenging part for me! Non of my previous trophy trucks has a proper suspension: it was either rear live-axle without articulation (Phantom, heavy-duty trophy truck) or independed rear suspension (Wilde Beast, Falcon). As I found from multiple driving tests of Phantom, rear axle need an articulation, cause otherwise RWD car loose the speed on bumps. IRS give the desired articulation and stability, moreover it is very simple to build and it has a low unsprung mass. Despite that IRS has a limited articulation and it is not presented in real Trophy Trucks either! Lego engineers designed a ball-joint connection, which is used in many Trophy trucks. It gives a single-lever suspension (with it`s simplicity and stiffness) and desirable articulation. Well, I did not use it, since it has no metal bearings for the U-joint inside the ball. So I had to replicate the 4-link live axle.

• 12-long reinforced suspension arms, 
• invested upper triangle,
• 9.5 L springs, attached to the mid of lower suspension arms,
• Anti row-bar with a carbon-fiber axle,

Now let`s move the the front suspension. Surely, real Trophy Truck has a complex front suspension, which is impossible to replicate with lego bricks. Though lego-ish version share important principles with real prototypes: 

• double wishbone with 8L suspension arms (9L was too wide here)
• Positive caster angle
• Reinforced lower arms
• Shock is attached to the lower arm closer to the center of the car
• Steering rack is located in the front of the car

Again I use custom wheel hubs with metal bearings. They have an inverted lower arm mounting point, though it is possible to use Lego hubs instead. With hart 9.5 L springs the front suspension has a long travel, moreover it has a great balance btw softness and responsiveness + side-way support. 

 

Bodywork & Frame

In order to achieve a positive caster angle I tilted the lower part of the frame. At the same time, the upper part of the frame. At the very front of the car upper and lower parts of the frame meets together which form the "almost right-angle" triangle with lengths: 13+1, 14+1 and 5+1. (right-angle triangle has the following lengths: 12+1, 13+1 and 5+1). Second time I use the Pythagoras theorem to make a force triangle for the rear springs attachment points. I tried to keep the frame of the truck in 13-15 studs wide, to use 15L liftarms for cross braces. I was Luckily to me I was able to squeeze all electronics into cockpit. This give the model 50:50 weight distribution and a "low" (for such high car) gravity center. Well, one would prefer to obtain 35:65 weight distribution for the RWD truck, but It would raise the gravity center and would require extra structure over the rear axle. 

The whole bodywork consist of 24 panels and a few bricks, so it does not cause much weight to the truck. 

Edited September 16, 2023 by Daniel-99

[2GodBDGlory]

Impressive engineering as usual! That rear differential is quite interesting, too

I also like the way the front wheel arch curves, so it's not just technical things on here that impress me!

[Timewhatistime]

This doesn't seem to be Lego anymore.

Does anyone here know the famous brand for construction toys originating from Denmark?

[Daniel-99]

3 hours ago, Timewhatistime said:

This doesn't seem to be Lego anymore.

Surely the Eagle truck is not a Lego-build for purists, but all the custom parts are designed to fit the Lego technic standards.

Trough the last 3 years Lego showed us their direction of marketing by introducing expensive and great-looking sets with ZERO functionality. Of course, one may argue, that 1:8 supercars has gearboxes inside. Fun fact, that many of them have problems with the gear shifting order, but most importantly, they are far from being "technical". With my builds I am trying to show you how one can tackle real technical problems with Lego bricks + custom parts. It is very frustrating to me, that Lego designed >20 new panel types, but we still don`t have steering links of lengths different from 6 and 9 studs... Lego sells their overpriced C+ electronics, but it can not compete with old Buggy Motors (I am not even compare it with Brushless setup). From my point of view Lego Technic should be more than just brick-build shelf models, but it should present us clever technical ideas from the real world. 

[2GodBDGlory]

I definitely feel the frustration about all these new panels coming out, when there's still obvious holes in the technical side! The one that bugs me the most is the 32T gear, but those other steering links would be extremely helpful too!

In fairness, though, alongside the huge numbers of new panels, there has been a lot of new technical parts this year, from the HD non-geared hub, the shorter HD CV-joints, the GT's double-ended CV joint, and the Yamaha's gearbox system, including the long-coveted 24T clutch gear

[gyenesvi]

Your builds are getting technically really deep, and at the same time the looks are also improving :) I like this one, looks badass! Curious how it drives, waiting for the video!

I agree with you that unfortunately, lately more focus has been on new panels than technical parts, though it's also true that this year brought us some nice positive surprises. But yeah, the selection of links and towball sockets for suspension and steering geometries is quite lacking, I always run into that while building..

Lately, I bought myself an RC pistol transmitter and an ESC to be able to control GeekServos. First I want to try it with PF and Buwizz motors (maybe test MouldKing ones, they seem to be more powerful). I'd love to get one of those motor housings for the brushless one as well, do you know where I could reach the guy? Do you know if he sells to other countries?

I also wonder if there are smaller variants of those brushless motors that are not that crazy powerful, somewhere in the middle. It would be great to have something like the power of a Buwizz motor in the housing of an M or L motor for example..

I like the rear axle and the triangulation there, nice solution, and that differential is pretty cool too. Pity that I don't understand anything about these websites and cannot get my hands on this kind of stuff..

[Timewhatistime]

I'm glad I could manage to evoke a little discussion... :-)

Without any doubt I really appreciate your engineering skills! It's likely that the way you have chosen, i.e. the combination of both, might be even harder than "pure" Lego or "pure" custom modelling.

Furthermore, many of us consent to the opinion that Lego Technic's quality (including their management's decisions) is rather going downwards than going upwards.

However, I don't get the point in combining high-end custom parts (like cv-joints, brushless motors, axles, hubs, wheels etc.) with the somewhat limited Lego parts (especially with the rather boring parts like beams and panels); the Lego parts don't increase the quality and could easily replaced by even more custom parts.

For me, the fascination of building PURELY with Lego lies in these very limitations that are provided by the fact that NOT every Lego part we would dream of exists. The challenge for us is to overcome the limitations - for which here, in the eurobricks forum, are plenty, plenty, plenty fascinating examples.

Edited September 15, 2023 by Timewhatistime

[2GodBDGlory]

3 hours ago, Timewhatistime said:

However, I don't get the point in combining high-end custom parts (like cv-joints, brushless motors, axles, hubs, wheels etc.) with the somewhat limited Lego parts (especially with the rather boring parts like beams and panels); the Lego parts don't increase the quality and could easily replaced by even more custom parts.

For me, the fascination of building PURELY with Lego lies in these very limitations that are provided by the fact that NOT every Lego part we would dream of exists. The challenge for us is to overcome the limitations - for which here, in the eurobricks forum, are plenty, plenty, plenty fascinating examples.

Yeah, I think there can be different styles here, with different challenges

One option is building with pure Lego, with the challenge of overcoming the limitations of the system

Another option, like seen here, is the challenge of designing the chassis and suspension of a high-performance RC car, which is something that really can't be done with such ease in the hobby RC world, and the Lego parts are more of a means to an end than the whole challenge in themselves

[Daniel-99]

On 9/14/2023 at 5:58 PM, 2GodBDGlory said:

Impressive engineering as usual! That rear differential is quite interesting, too

I also like the way the front wheel arch curves, so it's not just technical things on here that impress me!

On 9/15/2023 at 1:38 AM, gyenesvi said:

Your builds are getting technically really deep, and at the same time the looks are also improving :) I like this one, looks badass! Curious how it drives, waiting for the video!

On 9/15/2023 at 1:38 AM, gyenesvi said:

I like the rear axle and the triangulation there, nice solution, and that differential is pretty cool too. Pity that I don't understand anything about these websites and cannot get my hands on this kind of stuff..

Thank you all, guys, for your kind worlds. This really encourages me to for the future technical researches in Lego.

 

On 9/15/2023 at 1:38 AM, gyenesvi said:

Lately, I bought myself an RC pistol transmitter and an ESC to be able to control GeekServos. First I want to try it with PF and Buwizz motors (maybe test MouldKing ones, they seem to be more powerful). I'd love to get one of those motor housings for the brushless one as well, do you know where I could reach the guy? Do you know if he sells to other countries?

I also wonder if there are smaller variants of those brushless motors that are not that crazy powerful, somewhere in the middle. It would be great to have something like the power of a Buwizz motor in the housing of an M or L motor for example..

To be honest, I am a nub in the RC world, so could not consult you on the various components and configurations. Though I saw few examples of people been using BR motors in M-motor-scale housing. 

I am glad for your new transmitter purchase, hope It will serve you well! I am in contact with the Designer of the Custom motor housings, so I will ask him if he is planing to sell in Europe. 

 

On 9/15/2023 at 12:30 AM, 2GodBDGlory said:

In fairness, though, alongside the huge numbers of new panels, there has been a lot of new technical parts this year, from the HD non-geared hub, the shorter HD CV-joints, the GT's double-ended CV joint, and the Yamaha's gearbox system, including the long-coveted 24T clutch gear

On 9/15/2023 at 1:38 AM, gyenesvi said:

I agree with you that unfortunately, lately more focus has been on new panels than technical parts, though it's also true that this year brought us some nice positive surprises. But yeah, the selection of links and towball sockets for suspension and steering geometries is quite lacking, I always run into that while building..

Yes, guys, thanks for mentioning thous parts! I truly appreciate Yamaha's gearbox system, though I can not afford myself such an expensive set, to test the gearbox by myself.

 

13 hours ago, Timewhatistime said:

Without any doubt I really appreciate your engineering skills! It's likely that the way you have chosen, i.e. the combination of both, might be even harder than "pure" Lego or "pure" custom modelling.

Furthermore, many of us consent to the opinion that Lego Technic's quality (including their management's decisions) is rather going downwards than going upwards.

However, I don't get the point in combining high-end custom parts (like cv-joints, brushless motors, axles, hubs, wheels etc.) with the somewhat limited Lego parts (especially with the rather boring parts like beams and panels); the Lego parts don't increase the quality and could easily replaced by even more custom parts.

For me, the fascination of building PURELY with Lego lies in these very limitations that are provided by the fact that NOT every Lego part we would dream of exists. The challenge for us is to overcome the limitations - for which here, in the eurobricks forum, are plenty, plenty, plenty fascinating examples.

Thank you for your comment here! I can understand your position and I appreciate Pure-Lego engineers. I started myself with all limitations, which provide a purely Lego setup, so I now the difficulty of problems and the beauty of results. 

I switched from Pure-Lego in order to achieve more power and durability (i.e. overall performance of RC car). I am sure that nobody would argue, that Pure-Lego RC cars can not compete with mine in terms of transmission efficiency and wear resistance.  

[Krxlion]

I've been waiting for a new project from you, Daniel, and it's here! Clever usage of steering rack with perpendicular beams in rear axle arms. You built something similar that I recently have, but it didn't yet see the light on forum yet! A great display of clever engineering and I am waiting for video describing them even closer (something similar to Pathfinder video, it was very informative). I have some questions if I may:
1. You switched to 1200kv motor from 1000kv. Why is that? Was previous one too slow or something?
2. Are you planning on leaving completely Lego hubs, because the custom ones are so good? Have you tried the new ones from Lego Audi set?
3. I would like to see how rear suspension works if you "squezze" it, is that something you can add to your future video?
4. I can see that you are using 1500mah battery, instead of 1800mah. Have you found any good "housing" to it, so it can fit for example 5x7 frame like in the 1800mah battery?
5. I think I remember front axle usage in different project. Was it in your old but great Dragonflay or in one of Андрей Цапенко projects?

Once again, great showcase of your skills, I will probably find more great inputs in your model once I will dig deeper into the topic.

[Daniel-99]

On 9/16/2023 at 1:09 PM, Krxlion said:

I've been waiting for a new project from you, Daniel, and it's here! Clever usage of steering rack with perpendicular beams in rear axle arms. You built something similar that I recently have, but it didn't yet see the light on forum yet! A great display of clever engineering and I am waiting for video describing them even closer (something similar to Pathfinder video, it was very informative).

Hey! Thank you for your comment! I am glad that you have noticed reinforced rear axle arms, cause I found it very interesting as well. I will definitely make a detailed introductory video, but I do not promise on any date yet. Let me answer your questions

1. I have 2x 1000 kv motors and 1x 1200 kv motor, both motors works greatly, but I wanter a bit more power to the fast car, and the difference is visible here. On contrary, 1000 kv and 1200 kv motors feels exactly the same it the trial truck, since there is a plenty of gear reduction.
2. Custom hubs has has metal bearings and metal U-joints, so they significantly improve the transmission efficiency. I will not use "old" Lego hubs any longer, but I will keep using planetary hubs in trial trucks. It would be interesting to me to test the new Audi hubs, but I will not pay for C+ electronics and bunch of black panels. I guess, I will wait for good replicas or borrow origonal parts on the secondary market later. 
3. I will definitely review the geometry of the rear axle in the video, since it really affects the overall performance 
4. Yes, I have two Li-Po batteries with capacities: 2600 mAh and 1500 mAh. First one is big and heavy and it fit the 5x7 frame very nicely. The second one is 11 studs long, 4.2 studs wide and 2.5 studs high, so it is a bit of a challenge to fix it in place. I have not seen the 1800 mAh battery in my local RC store, but I guess different manufacturers make batteries with different dimensions, so it is always good to take some Lego parts in the local RC store to make some measurements there.
5. This is a new design, but it share the same general principles with the designs from my older projects (see the links in the "Experience and Inspiration" section). 

[dustblue]

On 9/14/2023 at 9:31 PM, Daniel-99 said:

Hey, guys! 

After a 3-month brake from Lego, I am glad to show you my new RC trophy truck, called Eagle. I apologise for the quality of photos and I will try to improve them later after I will get myself a studio light. I will also make a proper introductory video when I will get enough outdoor footage.

  Hide contents

Features

• Responsive long-travel suspension with 4-link live-axle at the rear and double wishbone at the front
• Brushless motor A2212 1200 kv for propulsion, Geek Servo for steering, 1500 mAh 3S Li-Po for power
• Strong and efficient transmission with metal U-joints and metal bearings.
• Great ground clearance for outdoor use, 95 mm RC wheels
• Light-weight bodywork

 

Experience and Inspiration

I guess that nobody will be surprised If I would make a confession that I have a deep passion for Trophy trucks. This type of vehicle suits the best for the role of a fast RC Lego cars which are build for outdoors. Indeed, outdoor environment is always rough and "bumpy" for Lego cars. I took my inspiration and first experience form several well-known Lego builders, such as:

• Sariel
• RM8
• ZeroBricks
• GooberReboot

Through the last 3 years of intensive engineering I made a few attempts in building myself a "proper" trophy truck. Each of them had it`s own features and technical problems:

• Heavy-duty Trophy Truck: RWD, 2x BM, 2x Buwizz 3.0 units, 95mm wheels. Problems: "big scale" which caused a serious load for motors, over-tilted front caster.
• Phantom: RWD, 2x BM, Leshy control unit, 85mm wheels, mid scale. Problems: lack of power from Leshy unit, lack of articulation at the rear, plastic wearing in the wheel hubs.
• Wilde Beast: 4WD, 4x BM, Wixy RC control + 3S Lipo, 95mm wheels. Problems: "big scale" which caused a serious load for motors, indep. susp. with a questionable geometry.
• Falcon: 4WD, 4x BM, Wixy RC control + 3S Lipo, 75mm wheels. Problems: indep. susp. with a questionable geometry, overheating of motors at the maximal RPM.

About a year ago I switched from Lego Buggy motors to a Brushless motor (for the reasons which will be covered later). This was not an easy switch for me and I had to learn some RC electronics theory and find the proper ways of using brushless motors with Lego. My latest RC cars with Brushless motors was:

• Unimog trial truck
• Pathfinder SUV
• Hornet 4x4 buggy

With pathfinder and Unimog projects I studied the 4-link live-axle suspension geometry, while with Hornet project I found the way to achieve a proper suspension and steering geometry with my custom wheel hubs. With this projects completed I get myself all cars I need.

- What should I build next?

With such question in mind, I faced a deep burnout from Lego, so I decided to take a summer brake. Hot summer days returned me my passion for Lego, and I had a plenty of time to plan a new project. I felt myself ready to make another attempt in building myself a "proper" trophy truck. That is how the story begins. 

 

Electronics

With my latest truck Falcon I reached the limit of what Buwizz motors could handle. Some time ago there was a discussion about efficiency and power-to-weight ratio. I would not resist that with the growing number of motors and Buwizz units, one could get a better power-to-weight ratio, though such a way faces the problem of plastic-weariness quite soon. With the growth of the number of motors, also grows the size of the car and it`s total weight, which get distributed to the four Lego plastic wheel hubs! I faced the plastic-weariness problem of Lego hubs with my Phantom truck, and solved it by purchasing custom wheel hubs with metal bearings, which I were used in the Falcon truck. Moreover, there was no gearing in the transmission of the Falcon truck: each wheel was connected to it`s own motor via driveshaft with metal bearings. With 4x Buwizz motors on board, powered by strong 3S Li-Po battery, Falcon had a great power-to-weight ratio. Through multiple tests I found that It can not handle full throttle for more than 45 seconds due to the rear motor overheating. It was pretty clear to me that RC Li-Po could easily overfeed 8 or even 12 motors with power, so there was no sense in adding more BM motors. 

Likely to me, one Russian AFOL developed a 3D-printed housing for Brushless A2212 motor which allowed to use it with Lego. I purchased two sets from him, and mot I have 100% RC setup. There was no problem with the lack of power or motor overheating anymore, but it was a real challenge for me to overcome this energy!

 

Transmission

With BM motors it is very natural to distribute the torque among axles \ wheels, by having separate transmissions to each axle \ wheel. But with Brushless motor I had to use "realistic" transmission, since there is only one output with a plenty of speed and torque. Despite the fact this motor is a baby-motor in the world of RC cars, It has enough power to twist Lego axles   with instant reaction to the throttle. Custom 3D-printed housing has a 4:1 planetary reduction, but the speed of the output is enough to cause gear-melting. That is why the following decisions were made:

• use metal U-joints all around, most of them have a 3L lego axle glued from one side to prevent them from falling off. 
• use silicone grease to lubricate the planetary gear in the motor housing and some external gearings.
• use custom parts with metal bearings to separate the transmission from the car frame.
• use carbon-fiber axles in the central driveshafts. 

The new Eagle truck has a very simple RWD transmission with a single "external" 14:23 gearing in the differential. Recall, that the 3D-printed motor housing has a 4:1 gear reduction. So the motor is connected to the differential via carbon-fiber driveshaft. From the differential power translates to the 95 mm RC wheels via half-axles with metal U-joints. The whole transmission sit on the metal bearings (custom wheel hubs with metal bearings, custom 5x7 frame with metal bearings for differential housing, motor output passes through the connector with the metal bearing). Surely you have noticed that I lifted the central differential by one stud over the wheel axle in order to achieve a higher ground clearance! 

Which differential to use RED or YELLOW?

RED differential has a 28:12 reduction which reduces the load from the driveshaft and the motor. Moreover, such gear ratio is more realistic. On the other hand, YELLOW differential has bigger teeth so it is stronger. But more importantly, is that YELLOW differential is 125% more efficient than the RED one, since it has bigger gears and does not scratch the 5x7 frame under the load. In fact, I am using a custom torsen differential with 23-tooth gear. It also does not scratch the 5x7 frame and hold half-axles much stronger than the original YELLOW diff.

 

Suspension

Trophy truck is all about suspension, and it was the most challenging part for me! Non of my previous trophy trucks has a proper suspension: it was either rear live-axle without articulation (Phantom, heavy-duty trophy truck) or independed rear suspension (Wilde Beast, Falcon). As I found from multiple driving tests of Phantom, rear axle need an articulation, cause otherwise RWD car loose the speed on bumps. IRS give the desired articulation and stability, moreover it is very simple to build and it has a low unsprung mass. Despite that IRS has a limited articulation and it is not presented in real Trophy Trucks either! Lego engineers designed a ball-joint connection, which is used in many Trophy trucks. It gives a single-lever suspension (with it`s simplicity and stiffness) and desirable articulation. Well, I did not use it, since it has no metal bearings for the U-joint inside the ball. So I had to replicate the 4-link live axle.

• 12-long reinforced suspension arms, 
• invested upper triangle,
• 9.5 L springs, attached to the mid of lower suspension arms,
• Anti row-bar with a carbon-fiber axle,

Now let`s move the the front suspension. Surely, real Trophy Truck has a complex front suspension, which is impossible to replicate with lego bricks. Though lego-ish version share important principles with real prototypes: 

• double wishbone with 8L suspension arms (9L was too wide here)
• Positive caster angle
• Reinforced lower arms
• Shock is attached to the lower arm closer to the center of the car
• Steering rack is located in the front of the car

Again I use custom wheel hubs with metal bearings. They have an inverted lower arm mounting point, though it is possible to use Lego hubs instead. With hart 9.5 L springs the front suspension has a long travel, moreover it has a great balance btw softness and responsiveness + side-way support. 

 

Bodywork & Frame

In order to achieve a positive caster angle I tilted the lower part of the frame. At the same time, the upper part of the frame. At the very front of the car upper and lower parts of the frame meets together which form the "almost right-angle" triangle with lengths: 13+1, 14+1 and 5+1. (right-angle triangle has the following lengths: 12+1, 13+1 and 5+1). Second time I use the Pythagoras theorem to make a force triangle for the rear springs attachment points. I tried to keep the frame of the truck in 13-15 studs wide, to use 15L liftarms for cross braces. I was Luckily to me I was able to squeeze all electronics into cockpit. This give the model 50:50 weight distribution and a "low" (for such high car) gravity center. Well, one would prefer to obtain 35:65 weight distribution for the RWD truck, but It would raise the gravity center and would require extra structure over the rear axle. 

The whole bodywork consist of 24 panels and a few bricks, so it does not cause much weight to the truck. 

Nice job done! I use metal u joints and carbon axles myself too, also rc tyers, but didn't go all the way to metal bearings and custom parts. Buggy motors are powerful enough for lego builds, so I didn't try brushless either. Do you have videos? 

[Daniel-99]

33 minutes ago, dustblue said:

Nice job done! I use metal u joints and carbon axles myself too, also rc tyers, but didn't go all the way to metal bearings and custom parts. Buggy motors are powerful enough for lego builds, so I didn't try brushless either. Do you have videos? 

Thanks! I am in the progress of making a video. Just need to film enough footage to share with you.

[rinatfruggi]

The rear suspension is looking awesome! Will wait fo the video to get more details about it!

[Daniel-99]

I made another outdoor test and want to share with you the results.

As I mentioned in the main post, I have chosen the YELLOW differential since it gives more speed and efficiency to the chassis. In the driving test I made a series of accelerations, which revealed a serious problem: max throttle in combination with a high grip cause twist-load to the rear axel, which detaches the upper suspension arms.

Well, I did not expect that, since non of Lego motors has enough power for such action. To fix it I should either reinforce the rear axle, or to swap back to the RED differential. I have chosen the second option, since with YELLOW I felt that the truck does not have enough "low-speed", which is needed for precise manoeuvres at home or in the crowd. To reduce the friction, I cut the crown gear from the outer side of the differential. Luckily, I had a second-party red differential in stock. 

Also I found that with a sharp acceleration, the front left wheel get lifted from the ground. This is a natural effect for the live-axle suspension. Though I was able to balance the twisting force by swapping the Li-Po battery and a RC controller (initially, Li-Po battery located at the right side of the cockpit, while the controller at the left).

With the RED diff in place, I made another run. This time Truck had a desirable speed limits:

• with a little throttle (~20%) truck has a speed of 5 km/h
• with the full throttle truck has a speed ~18 km/h

One more issue was found during the drive: front shocks get detached form the ball-connection in the jumps. Clearly, this was caused by significant mass of wheels and wheel hubs. I will fix this issue by attaching the rubber band. 

 

I will made another test run asap, at the same time I will order the studio light to make a detailed review for you guys!

 

[Krxlion]

When you pushed the throttle to full with A2212 aboard I was like: "Sheeeeesh! :O". It really couldn't end better than twisting axles, melting or something popping out :D. For me, speed like 12-18km/h is fine and desirable. I also prefer to have an option to go slow with the model for some precise manouvers. Great showcase and keep us posted. Little off-topic, but an informatioo for Daniel -  my Frontliner progress will be showed later as I found my current method of meshing Lego Technic with BM, to be too messy.

[dustblue]

10 hours ago, Daniel-99 said:

I made another outdoor test and want to share with you the results.

As I mentioned in the main post, I have chosen the YELLOW differential since it gives more speed and efficiency to the chassis. In the driving test I made a series of accelerations, which revealed a serious problem: max throttle in combination with a high grip cause twist-load to the rear axel, which detaches the upper suspension arms.

Well, I did not expect that, since non of Lego motors has enough power for such action. To fix it I should either reinforce the rear axle, or to swap back to the RED differential. I have chosen the second option, since with YELLOW I felt that the truck does not have enough "low-speed", which is needed for precise manoeuvres at home or in the crowd. To reduce the friction, I cut the crown gear from the outer side of the differential. Luckily, I had a second-party red differential in stock. 

Also I found that with a sharp acceleration, the front left wheel get lifted from the ground. This is a natural effect for the live-axle suspension. Though I was able to balance the twisting force by swapping the Li-Po battery and a RC controller (initially, Li-Po battery located at the right side of the cockpit, while the controller at the left).

With the RED diff in place, I made another run. This time Truck had a desirable speed limits:

• with a little throttle (~20%) truck has a speed of 5 km/h
• with the full throttle truck has a speed ~18 km/h

One more issue was found during the drive: front shocks get detached form the ball-connection in the jumps. Clearly, this was caused by significant mass of wheels and wheel hubs. I will fix this issue by attaching the rubber band. 

 

I will made another test run asap, at the same time I will order the studio light to make a detailed review for you guys!

 

impressive! thanks for sharing, I see you cant keep up with your truck hahaha:)

[Krzychups]

For me, a speed of less than 20 kph is low. I much prefer playing with lego cars at higher speeds. I currently have an A2212 2200kv brushless motor and it's perfect for me (I'm in the process of building my car, I think the speed will be around 30-40 kph). 

[Daniel-99]

23 minutes ago, Krzychups said:

For me, a speed of less than 20 kph is low. I much prefer playing with lego cars at higher speeds. I currently have an A2212 2200kv brushless motor and it's perfect for me (I'm in the process of building my car, I think the speed will be around 30-40 kph). 

Welcome to our small Brushless motor community here on EB! It will be interesting to see how does the A2212 2200kv work with Lego. 

[Krzychups]

Thanks!

As I wrote, I'm working with my rc car so... I will show you my creations :)

Edited September 22, 2023 by Krzychups
Improving expression

[Daniel-99]

Hey guys, some of you might wonder why I am not posting a final video about my Trophy Truck. Well... I feel, that the project is not finished yet, and there are many things to improve. Currently I am redesigning the rear axel in order to make it more compact. Also I decided to use a custom central gearing hub (big black box in the left-side assembly). This will move the center of gravity backwards, and allows me to connect the lower links of the susp. as low as possible.

 

Edited October 18, 2023 by Daniel-99

[Krxlion]

No worries Daniel, take your time to finish the MOC. I am looking forward to find out how this "black box" contributes to the whole build.

[Daniel-99]

Hello guys! As I am in the process of designing V2 of my Eagle, I made an introductory video the the current version of the trophy truck. 

 

[Krxlion]

Like I said under your YT post: "The suspension feels so smooth :D I wonder if those two links on the rear axle don't pop off during riding on heavy off-roads? I love how you hide all those RC electric components and the body looks great as well! I can see a real improvement since your latest models, great job!"

[Daniel-99]

On 10/31/2023 at 5:17 PM, Krxlion said:

 I wonder if those two links on the rear axle don't pop off during riding on heavy off-roads?

Thank you for your comment! The two links at the rear were not tempted to fall off.

On 10/31/2023 at 5:17 PM, Krxlion said:

I love how you hide all those RC electric components and the body looks great as well! I can see a real improvement since your latest models, great job!"

I am glad you liked it! It was a tough choice to put all the electronics in the cockpit, cause it really affected the weight distribution. It is very important to load the rear axle of a Trophy Truck, and I failed with Eagle here. That was the main reason for me to build the second version of the Truck from scratch. I have already tested the V2 outside, so I will make a separate EB post soon (as Zerobricks did with his Universal off-roader).