RC Monster Truck [MOC]

[Daniel-99]

Hello everyone!
I want to share with you my Monster truck that I build for an outdoor winter driving. It has a lot things to improve, but even this imperfect build gives a lot of fun! Yes, this post is mostly not about technical aspects, but about the whole concept and the driving experience it gives!

Some highlights: 

• All wheel drive and steering 
• Solid axle suspension with permanently locked differentials
• Planetary wheel hubs
• Strong transmission with metal U-joints and metal bearings 
• Brushless motor 1000 kv
• 3S Li-Po for power
• 2 GeekServo for steering
• 120 mm RC wheels with great grip
• Removable body

Together big wheels and powerful motor makes this Monster Truck a real beast. It has both torque and a decent speed. Planetary wheel hubs give enough reduction to obtain the precise control of torque (that is rather unusual for Brushless motors). All wheel steering with deferent steering modes (made as an option of my RC transmitter) bring more fun to the driving. It also increases the climbing abilities of the Truck (as it is shown in the video). 

 

[FriedlS]

Great work again! 👍😊

[Daniel-99]

13 hours ago, FriedlS said:

Great work again! 👍😊

Thank you! It seems to me that there is only a small group among AFOLs that enjoy brushless motors.

Do you have any new projects with you brushless motor, by the way?

[FriedlS]

11 hours ago, Daniel-99 said:

Thank you! It seems to me that there is only a small group among AFOLs that enjoy brushless motors.

Do you have any new projects with you brushless motor, by the way?

Yes it seems so, but it is ok! I like the combination of brushless motor and Lego 😊

At the moment i still try to improve my Trophy Truck and i hope the weather will be better soon to test it outside….

[Krxlion]

Hi guys,

For the last few months I've been trying to implement brushless motors into our bricks. I have a few questions and if you would answer them I will appreciate that a lot! :)
1. I am struggling with melting axles, this is probably because of high RPM motor. I am using 2838 bl motor, 4500kv right now and if I would choose different one, do you recommend A2212 1000KV for lets say 1-1,5kg models or should I go with different one?
2. What pinion gear are you using to match lego gears? I am using 10T Bullet Flux Pinion but I find it just slightly to small, it rotates with for example 20T lego gear and there is small space between those two gears.

Just to sum it up, I am using DumboRC 6r with gyro receiver, I have 35A ESC and one geek-servo. Currently I am working on baja truck, actually I have one now but during some recent tests I still believe this model is not yet ready to be showed on forum. :)

PS Daniel, your model is great I am looking always forward to see more of your models since you release Dragonfly! :)

[Daniel-99]

3 hours ago, Krxlion said:

For the last few months I've been trying to implement brushless motors into our bricks. I have a few questions and if you would answer them I will appreciate that a lot! :)
1. I am struggling with melting axles, this is probably because of high RPM motor. I am using 2838 bl motor, 4500kv right now and if I would choose different one, do you recommend A2212 1000KV for lets say 1-1,5kg models or should I go with different one?
2. What pinion gear are you using to match lego gears? I am using 10T Bullet Flux Pinion but I find it just slightly to small, it rotates with for example 20T lego gear and there is small space between those two gears.

Just to sum it up, I am using DumboRC 6r with gyro receiver, I have 35A ESC and one geek-servo. Currently I am working on baja truck, actually I have one now but during some recent tests I still believe this model is not yet ready to be showed on forum. :)

PS Daniel, your model is great I am looking always forward to see more of your models since you release Dragonfly! :)

Hi, @Krxlion!

I have neither a qualification of an electrician nor any experience with RC cars world, and I started using brushless motors in Lego builds just 3-4 months ago, so do not judge me strictly if I am mistaken ;-) Melting axles is the first potential problem on a list. These problems usually happens one after another, so you will not face problem 5 on a least before you have not solved problems 1-4:

1. Problem: melting axles. Solution: lubricate the transmission with a silicone grease.
2. Problem: axle twisting. Solution: Build the drive shaft with axle connectors
3. Problem: CV-joints and U-joints breaking. Solution: Use metal U-joints compatible with lego
4. Problem: Gear cracking (especially an angular gear to the differential). Solution: tighten the connection with plastic or metal washers 
5. Problem: braking of gear connection points. Solution: unload the transmission 1) use planetary hubs (for 4x4 cars is the best solution) 2) Use 28:12 gearing in differential 3) Use smaller (and lighter) wheels 4) use a weaker motor

The motor you use is way overpowered! One AFOL in Russia tested motors with similar strength in his Lego cars and it was impossible to overcome its power! Plastic transmission could not basically handle such power. I am using A2212 1000-1200 KV motors. They have enough strength to overcome 3 Buwizz motors. I mostly build fast cars with a total weight under 2 kilos, and this motors bright them to live easily, though I have to deal with problems 1-4. 

I can not tell you anything about Pinions, since I bought the whole RC setup from another Russian AFOL. He develops custom 3D printed parts for Lego cars. Here is a link to his original video: 

As you can see, he printed a planetary gear similar to one used in XL motors. So I dont have to deal with Pinions at all. Instead of that I have to lubricate gears regularly. If you will need some details from the video you could ask me for translation and explanation!

 

After we get ourselves a right motor and solves all problems from the list, we should figure out our goals: what do we want from our Lego car with RC motor? My answer is the following: brushless setup beats all existing PF and C+ systems, the best ways to build cars with brushless system are presented by RC cars industry, but we will never achieve the same level of performance with Lego. 

My technical requests for Lego RC cars are the following: speed of 10-15 km/h for fast cars (like trophy trucks) and 3-8 km/h for 4x4 off-roaders. Faster cars will not survive crashes, and it will be very hard to control even with physical proportional control provided by GeekServo (due to the wobbling in the steering system). Slower cars are too boring to play with. Further, I wish to make my cars as durable as it possible. Here I mean not the durability of the chassis and body, but the wear resistance of transmission and Lego parts during regular driving sessions.

To achieve the goal, I use custom parts with metal bearing made by few AFOLS from Russia. Also I lubricate all the gears which spin fast. Most important parts here are the wheel hubs with metal bearing since the whole weight of the car sits of this fast-spinning parts. I was lucky enough to buy a few sets of custom hubs both with metal bearing and metal U-joints adapted to them, so I can build FWD and AWD fast cars with them. For off-roaders, I am using planetary hubs from AliExpress, because they are not glued from the fabrics and can be easily taken apart, lubricated and glued into a single piece. Also they are wide-spread and cheap. For the next level of improvements, I use metal U-joints and carbon axles in the transmission, 5x7 frames with metal bearings (to install differentials), which avoid any cracking in the transmission.

 

To sum up, extra power and extra speed requires many NON-Lego-ish solutions and it will cost you a lot. So if you want yourself a fast and durable RC car for every day, you would better by an RC car. But if you are looking for a serious development process, if you like test your cars and improve them to the max level, then this is for you! 

I wish a good luck to every person who is building Lego cars with Brushless motors!

 

 

 

 

[Krxlion]

Many thanks Daniel!

I must say your list regarding gears problems is interesting, I will keep it in mind. I started lubricating lego gears but due to high rpm of my current brushless motor the lubricant simply go away few seconds after revving the engine. :D
I have watched the video with some subtitles and ordered right away the A2212 1000KV just to have it in stock for future MOCs or to replace the current one :) The casing showed in the video is marvelous, I believe it would not have a problem with escaping lubricant like I have due to closed case. All in all I am aiming at something that @FriedlS created, baja truck but in a bigger scale, something 1:10 or 1:12, 10-15km/h speed and decent climbing ability (35-45 degree angle). Maybe if you are interested I could film my current model and upload it in a new post, so you could help me with solving my issues. In the end I want to use as less as possible non-lego parts. My initial thoughts was to create a MOC that is simply delivered with more power. I bought two BW 3.0 in the past 1-2 years but even implementing those two in a single model is not enough if you use BW Motors or Buggy motors, shutdown, bluetooth lag, etc.

[Daniel-99]

19 hours ago, Krxlion said:

My initial thoughts was to create a MOC that is simply delivered with more power. I bought two BW 3.0 in the past 1-2 years but even implementing those two in a single model is not enough if you use BW Motors or Buggy motors, shutdown, bluetooth lag, etc.

I came to Brushless motors in the same way. Firstly I tried to power my creations with 2x Buwizz 3.0 units. They offer the best solution for Lego purists, and yes, Buwizz bricks (v. 3.0) are way more powerful than lego. But I was unlucky to drive into a garden pool, so both Buwizz units drowned. After an accident decided to experiment with custom Electronics, since It was way cheaper, more affordable in Russia and has an RC control system instead of Buwizz. I teated two different systems. First one is called "Leshy" it was not strong enough to power 2 Buwizz motors: batteries start degenerate quickly after I apply full gas (single Buwizz 3.0 unit has the same problem). Second system is called "WIxy" and they play a role of a RC controller for Brush motors (PF motors). This mighty units together with 3S Li-Po can give a plenty of power, but PF motors can not handle than much, so they start overheating of a full gas after 2 mins. This gives me the understanding that I should use a 100% RC setup to avoid any losses of power.

 

19 hours ago, Krxlion said:

All in all I am aiming at something that @FriedlS created, baja truck but in a bigger scale, something 1:10 or 1:12, 10-15km/h speed and decent climbing ability (35-45 degree angle). In the end I want to use as less as possible non-lego parts.

I see. A baja truck made by @FriedlS is a very special one. It is rather small and light, so there is not much load in the transmission, not much load to the wheel hubs, so Lego parts could work here. If you are willing to build a bigger truck, you will have to deal with extra weight, and the weakest point here are the wheel hubs. I am sure you will build the car that drives good mostly with Lego parts, even in 1:10 scale, but you should be ready to swap some parts of transmission in between each ride. That is why I use metal parts (cause I am lazy) ;-)

 

19 hours ago, Krxlion said:

Maybe if you are interested I could film my current model and upload it in a new post, so you could help me with solving my issues.

I think we should start a new topic all together with @FriedlS to discuss Brushless motor usage and related stuff. This way some other people might join our discussion!

[FriedlS]

56 minutes ago, Daniel-99 said:

I came to Brushless motors in the same way. Firstly I tried to power my creations with 2x Buwizz 3.0 units. They offer the best solution for Lego purists, and yes, Buwizz bricks (v. 3.0) are way more powerful than lego. But I was unlucky to drive into a garden pool, so both Buwizz units drowned. After an accident decided to experiment with custom Electronics, since It was way cheaper, more affordable in Russia and has an RC control system instead of Buwizz. I teated two different systems. First one is called "Leshy" it was not strong enough to power 2 Buwizz motors: batteries start degenerate quickly after I apply full gas (single Buwizz 3.0 unit has the same problem). Second system is called "WIxy" and they play a role of a RC controller for Brush motors (PF motors). This mighty units together with 3S Li-Po can give a plenty of power, but PF motors can not handle than much, so they start overheating of a full gas after 2 mins. This gives me the understanding that I should use a 100% RC setup to avoid any losses of power.

 

I see. A baja truck made by @FriedlS is a very special one. It is rather small and light, so there is not much load in the transmission, not much load to the wheel hubs, so Lego parts could work here. If you are willing to build a bigger truck, you will have to deal with extra weight, and the weakest point here are the wheel hubs. I am sure you will build the car that drives good mostly with Lego parts, even in 1:10 scale, but you should be ready to swap some parts of transmission in between each ride. That is why I use metal parts (cause I am lazy) ;-)

 

I think we should start a new topic all together with @FriedlS to discuss Brushless motor usage and related stuff. This way some other people might join our discussion!

Hello,

@Daniel-99is absolutely right with these 5 issues. My trophy truck is really light, it has got about 0.83kg. When you look at my post about this truck, you can see that i use ballbearings for the driven axle. And i also you use carbon axles. In this configuration there is no problem with melting parts etc. To be honest i don’t know how fast it can go, but i guess it is above 15km/h (1000kv with 2s lipo, 12:36 gear ratio and 75mm wheel diameter). 
In this building i avoid u-joints and when i would build a bigger car would do either. 
I will looking forward to a new topic about brushless motor usage! 😊

c u Friedl