[MOC] Race/Trophy Truck (Not 100% LEGO)

[PorkyMonster]

Hey Guys,

In this thread I'll introduce my race/trophy truck

It features caster, kpi, long-travel suspension (front independent, rear fixed-axle) with damping, RWD, manually functional LED lights, hood, doors, extendable door steps, and moon-roof. Rather sizeable, at 4kg, and 65 (L) x 31 (W) x 30 (H) studs in dimension. Weight distribution is 50:50.

And here's how it looks underneath...

There was no modification to LEGO pieces, and no 3D printed parts were used. However, I've opted to use 3rd party components (mainly the electronics) because where I live, TLG does not deliver. There is a local shop selling LEGO stuff, but is often poorly stocked when it comes to Technic/PF components. While I do realise that these won't integrate readily with LEGO Technic pieces, and wiring will be messy, I was willing to give it a shot because they offer better performance and configurability.

I started off wanting to include a gearbox (at least semi-auto if possible), camber and ackermann, full independent suspension, 4WD, etc. But as you'll see in due course, I encountered challenges either directly or indirectly due to my use of 3rd party components . I will provide more details about these later on. For now, suffice to say that there is some sort of a dilemma here - With LEGO PF, I can probably incorporate all these features, but I'll end up with something that drives like a tortoise (which defeats the purpose of having these features in the first place). However, with 3rd party electronics, I'm able to drive much faster, but that also resulted in the need to build a stronger model to withstand occasional crashes, and stronger drive-train to handle greater torque, and all these bits and pieces add to the resulting weight and size (don't forget that I need additional pieces to act as 'bracing' for the 3rd party electronics too). More details later on...

For now, I've prepared a short video:

In subsequent posts (assuming that there is sufficient interests), I will describe the challenges that I've encountered, and how they contributed to my current design decisions. Roughly, I'm thinking of elaborating on these areas:

- Steering Axle/Hub Design (including how I incorporated a 3rd party servo)

- Drive-train Design (why and how I gear down the brushless motor way before the wheel portals)

- Suspension Design (why do i use this part, among other things)

- Any other areas that you guys want to know more about...

Edited June 8, 2016 by PorkyMonster

[arshiaIQ]

Hey Guys,

In this thread I'll introduce my race/trophy truck

It features caster, kpi, long-travel suspension (front independent, rear fixed-axle) with damping, RWD, manually functional LED lights, hood, doors, extendable door steps, and moon-roof. Rather sizeable, at 4kg, and 65 (L) x 31 (W) x 30 (H) studs in dimension. Weight distribution is 50:50.

And here's how it looks underneath...

There was no modification to LEGO pieces, and no 3D printed parts were used. However, I've opted to use 3rd party components (mainly the electronics) because where I live, TLG does not deliver. There is a local shop selling LEGO stuff, but is often poorly stocked when it comes to Technic/PF components. While I do realise that these won't integrate readily with LEGO Technic pieces, and wiring will be messy, I was willing to give it a shot because they offer better performance and configurability.

I started off wanting to include a gearbox (at least semi-auto if possible), camber and ackermann, full independent suspension, 4WD, etc. But as you'll see in due course, I encountered challenges either directly or indirectly due to my use of 3rd party components . I will provide more details about these later on. For now, suffice to say that there is some sort of a dilemma here - With LEGO PF, I can probably incorporate all these features, but I'll end up with something that drives like a tortoise (which defeats the purpose of having these features in the first place). However, with 3rd party electronics, I'm able to drive much faster, but that also resulted in the need to build a stronger model to withstand occasional crashes, and stronger drive-train to handle greater torque, and all these bits and pieces add to the resulting weight and size (don't forget that I need additional pieces to act as 'bracing' for the 3rd party electronics too). More details later on...

For now, I've prepared a short video:

In subsequent posts (assuming that there is sufficient interests), I will describe the challenges that I've encountered, and how they contributed to my current design decisions. Roughly, I'm thinking of elaborating on these areas:

- Steering Axle/Hub Design (including how I incorporated a 3rd party servo)

- Drive-train Design (why and how I gear down the brushless motor way before the wheel portals)

- Suspension Design (why do i use this part, among other things)

- Any other areas that you guys want to know more about...

Wow!! I love this sturdy car... everything seems robust, the diff, the cardan, steering and etc!

Looks is also great

Good luck

[PorkyMonster]

Wow!! I love this sturdy car... everything seems robust, the diff, the cardan, steering and etc!

Looks is also great

Good luck

Glad u like it

But I'm probably riding on an 'unfair advantage' here - because of the motor I used, I'm able to be less concerned with weight and size and thus am able to create something really sturdy and robust... But I see at least one downside - I tend to just use whatever pieces I have and 'wrap on' for the purpose of reinforcement, rather than choosing the best piece for every specific job for a more elegant design.

[JJ2]

Looks a lot better then mine! Have you had problems with parts melting or did you use grease?

My projects have been put to a halt since my motor I have been getting keeps destroying itself after 5-10min of use

Maybe brushless was the way to go.

[PorkyMonster]

Have you had problems with parts melting or did you use grease?

Of course - these are the casualties:

Axles and beams were twisted or melted due to friction and heat, gears slipped so badly that their teeth became blunt, and other gears/knobwheels and universal joints broke under insurmountable torque.

But that was back then when I just started... when I had no prior experience... Then I began to incorporate bearings and grease, like these

and

The bearings (MR85 - 5mm internal, 8mm external and 2.5mm thickness - and 3 of them will fit into 1 stud space) are absolutely necessary near the motor - where gearing down is done... I'll elaborate on this in my later posts on gearing down the motor. As for the grease, I've applied it to mainly to the gears to reduce noise and eliminate breakages.

My projects have been put to a halt since my motor I have been getting keeps destroying itself after 5-10min of use

Maybe brushless was the way to go.

sounds like u've worked your motor too hard... have u tried gearing it down further? I use Eneloop Nimh batteries instead of Lipo that most hobby-grade RCs use, primarily because I'm not familiar with Lipo, and also because I did not aim to create a super fast truck to compete with them, so I don't see the need to have that kind of 'exposive' power that Lipo supplies... and even with eneloop, I've only used 6s2p (i.e. ~7.2v), which is only 60% of the maximum voltage and current that the motor can take, and I'm already quite happy with its performance. (fyi, I DID hook up with 8s4p (~9.6v) earlier on, just for fun... and it was so fast (despite the additional weight) that I kept losing control and crashing into walls and furnitures :tongue: so I won't dare use Lipo :laugh: .)

Regardless, I think brushless is the way to go, because it is definitely more energy efficient and requires no maintenance (unlike brushed motor where the brushes are subject to wear and tear).

Edited June 9, 2016 by PorkyMonster

[MRP_]

This is really great! I know the purists won't like it, but it's nice to see someone using lego as a platform for other things! Very creative! Also thanks for taking one for the team to prove the whole "lego can't handle brushless" argument!

[Lego2016Lego]

I guess you could call me a "purist" but I guess I am one because I don't like breaking parts

[JJ2]

On 6/8/2016 at 10:49 PM, PorkyMonster said:

Of course - these are the casualties:

Axles and beams were twisted or melted due to friction and heat, gears slipped so badly that their teeth became blunt, and other gears/knobwheels and universal joints broke under insurmountable torque.

Dang! Now I feel better about melting 3 parts together after I saw this!

You never said but how big was the motor you were using? a 550.

For my next project I'll just use my 550 12T motor

On 6/8/2016 at 10:49 PM, PorkyMonster said:

I use Eneloop Nimh batteries instead of Lipo that most hobby-grade RCs use, primarily because I'm not familiar with Lipo, and also because I did not aim to create a super fast truck to compete with them, so I don't see the need to have that kind of 'exposive' power that Lipo supplies... and even with eneloop, I've only used 6s2p (i.e. ~7.2v), which is only 60% of the maximum voltage and current that the motor can take, and I'm already quite happy with its performance. (fyi, I DID hook up with 8s4p (~9.6v) earlier on, just for fun... and it was so fast (despite the additional weight) that I kept losing control and crashing into walls and furniture so I won't dare use Lipo .)

I think using a Nimh battery would be good for you this, also they don't turn into a angry fireball like LiPo's do so that a plus

Edited November 4, 2016 by JJ2

[z3_2drive]

In the future I plan to start a project similar to this, but more likely a lower, wider, road/rally car. Do you think that a light build (My last build was about 1.6 Kg) with a brushless motor and Li-ion batteries could survive without harming original parts? I have lithium grease and bearings are an easy find, and I will most likely get a 3D printed motor mount to merge the motor/servo to the Lego chassis. As for suspension I'll use effe's printed spherical gear adapters (CV joints) I have now - they seem to be very strong and I'm curious if they will survive a new level of crazy. If not, a simple live axle. A lot will have to be tested, for example if a differential is even possible to use without breaking it, or if the motor will have to be mounted on the axle, as well what ratios to use to get the max Rpm at a sensible level. I'm eager to read how you overcame the challenges in this model

[PorkyMonster]

This is really great! I know the purists won't like it, but it's nice to see someone using lego as a platform for other things! Very creative! Also thanks for taking one for the team to prove the whole "lego can't handle brushless" argument!

You never said but how big was the motor you were using? a 550.

For my next project I'll just use my 550 12T motor

In the future I plan to start a project similar to this, but more likely a lower, wider, road/rally car. Do you think that a light build (My last build was about 1.6 Kg) with a brushless motor and Li-ion batteries could survive without harming original parts? I have lithium grease and bearings are an easy find, and I will most likely get a 3D printed motor mount to merge the motor/servo to the Lego chassis. As for suspension I'll use effe's printed spherical gear adapters (CV joints) I have now - they seem to be very strong and I'm curious if they will survive a new level of crazy. If not, a simple live axle. A lot will have to be tested, for example if a differential is even possible to use without breaking it, or if the motor will have to be mounted on the axle, as well what ratios to use to get the max Rpm at a sensible level. I'm eager to read how you overcame the challenges in this model

IMO, LEGO can handle ALL kinds of motor ... the key is in how much and how we gear it down, the power we supply it with, and how we drive our models. For brushless, while I've tried with 9.6v nimh (and survived... with lots of crashes... haha), I've yet to try with max power (11.1v lipo) and drive with max 'punch' for my motor... but even if that works, there'll still be ever faster or stronger motors out there.

The motor I use is a 540, 3300KV motor. For brushless motors using the KV ratings, every volt u supply will increase its rpm by the KV value - so when I supplied 7.2v, my motor will rotate 3300x7.2 = 23760 rpm. Assuming 90% efficiency, that'll be roughly 21384 rpm. As I've also read somewhere that LEGO parts can only withstand 4000 rpm before it starts to melt, I decided to gear it down 5 times with bearings in place, to reduce rpm to about 4277 rpm before it reaches the cardan and differential and so on. I gear down even further at the differential (by 2.3) and at rear wheel portal (by 1.7) for good torque suitable for my truck's weight and wheel size. (btw, a 1:1 at the wheel portal worked too for my configuration, just that I preferred greater torque to overcome bigger obstacles ).

Just for fun, I've created another video that shows more driving around compared to the earlier one

Edited June 10, 2016 by PorkyMonster

[PorkyMonster]

In the future I plan to start a project similar to this, but more likely a lower, wider, road/rally car. Do you think that a light build (My last build was about 1.6 Kg) with a brushless motor and Li-ion batteries could survive without harming original parts? I have lithium grease and bearings are an easy find, and I will most likely get a 3D printed motor mount to merge the motor/servo to the Lego chassis. As for suspension I'll use effe's printed spherical gear adapters (CV joints) I have now - they seem to be very strong and I'm curious if they will survive a new level of crazy. If not, a simple live axle. A lot will have to be tested, for example if a differential is even possible to use without breaking it, or if the motor will have to be mounted on the axle, as well what ratios to use to get the max Rpm at a sensible level. I'm eager to read how you overcame the challenges in this model

I guess, regardless of weight, so long as the immediate output from the motor is geared down to around 4000, parts won't melt... what remains is to make sure the shafts, gears, etc. downstream are built to be strong (primarily, avoid using long axles, standard CV joint and standard Universal joint if possible), properly braced and lubricated to prevent high torque from breaking them (because, after gearing down a brushless motor, its torque is already much much higher than any PF motors... and a light car meeting obstruction can also result in extreme current draw and torque that will break parts).

Coincidentally, I'm also planning for my next build - also a road/rally car that is lower and wider, I'll use 3rd-party rims and wheels (because LEGO ones are too small proportionally for cars of this size)... again, it probably won't be lightweight, and I plan to make it an AWD with CVT :devil: :laugh: . Shall also have good steering angle, caster, progressive camber and kpi.

[PorkyMonster]

So this is my front axle with servo housing attached...

Any servo that looks like the following will fit into the housing (note that the silver adapter on top comes separately). Here's the ugly part: I stuffed cardboards all around between the servo and the housing to secure it in place . And it is simple to just attach (with screws) the silver adapter to the blue thin 1x5 liftarm.

If you're interested in the details, feel free to check this out http://bricksafe.com/files/PorkyMonster/rc-racetrophy-truck/RC%20Truck%20Front%20Axle.lxf

Both the yellow and white shocks are there just for show, because I couldn't find the air shock (this), which I'm using, in LDD. I've also left out how the entire structure is attached to the chassis as a 'tilted subframe' in order to create a caster angle... as that might not be interesting and this is also my first attempt at using LDD.

Notice that I'm using parallel steering link. This greatly reduced bump steer and play... especially for heavy models. Also, if there is only one link located toward the center of the model, the inner wheel tends to get 'locked up' when reversing and turning at the same time - something I noticed when I have caster... perhaps weight is also a contributing factor. I also noticed unnecessary toe out with only one link, and that can pose a problem driving forward. Downside with parallel links is that I cannot incorporate ackerman angle.

The red thin 3x3 liftarms are there to prevent the lower wishbone and both steering links from popping out during impact.

And the 3 wedge belt wheels attached to each rim simply attaches the rims tighter to the axles - and I no longer have wheels falling off ever since .

There is no camber, since I'm not planning to drive and steer my model at extreme speed (I always practice good driving - slow down before turns ).

Yup, this is all I have regarding my front axle .

[z3_2drive]

Can you show your use of bearings in gearing down the motor?

[PorkyMonster]

Can you show your use of bearings in gearing down the motor?

Sure.

(lxf file download)

All yellow half-bushes can be replaced with bearings - u'll need to use multiple bearings so that their combined thickness roughly equals the half-bushes.

Also note that the housing in my case is for motor size of 540. And the gearing down ratio in my case is 3 x 1.7 = 5.1. U'll have to change the structure if you want to gear down to other ratio - I'm sure you know what to do .