Daniel-99

Here is final V2 of my Unimog U4000. From the previous update I have changed: A-pillar design Front fenders Raised the cabin and the flat bed over the chassis by 1 stud Raised mounting points of the springs by 1 stud This changes solved all problems with the front axle, and now truck is ready for serious off-road actions! V2 has a chassis similar the chassis from my previous MOC Pathfinder, but with several changes: planetary wheel hubs locked rear differential different gear combination in the transmission Softer spring setup relocated battery box and RC controller As a result, Unimog perform better in trial than my Pathfinder! I will make a video soon!

Very smooth body shapes! O love C-pillars and a cheating A-pillar design!

Great progress! I love the new motor placement a lot! Now they dont stick out from the sides of a car. I still not understand why one need so much reduction in the transmission ;-) 8:40 reduction in portal axles seems to be enough for me. Moreover I would use planetary hubs instead of brick build portal hubs to keep the transmission from unwanted mud and dust, simplify the build, avoid any potential problems with gear skipping! Brick built portal hubs looks like an interesting development \ theoretical project rather than practical solution for outdoor RC driving.

Piece of technical art, and that is it!

I would prefer OPTION 2 as well. Moreover I am interested to see how you adapted Attika`s design to defender rims in more details! Currently the steering rack has not been fixed in place properly. I would attack some sort of "slider axle" to prevent unwanted wobbling.

Hello Eurobricks! I am back with improved version of Unimog U4000, currently it is a WIP! List of changes: redesigned live-axles new suspension raised body by 1 stud new RC tires 95 mm (instead of 85 mm) Front fender lowered by 1 stud thickened cab roof flat-bed and rear lights added Well, now I want to widen the whole body by 2 studs to fit the reference even closer. Also I made a driving test and found a technical issue with the new chassis. To fix it I have to make the front driveshaft longer by 1-2 studs.

I like the clean bodywork and the steering wheel choice! Suspension seems to be too hard. It will be great if you would add several photos of the chassis to your presentation!

Thank you! It took me a week to make a EB post, there are plenty things that could be done better (written better), but I was not able to work on the presentation another week or two ;-) My cars are mad and fast, but there are very few people who would use a variety of custom parts as I do. I really love your building style, @gyenesvi! I appreciate your attention to the mechanical aspects and the way you build your cars under the limitation of a single Lego set. With your RC cars you give more to the community than me ;-)

I used to read to my favourite EB topics twice, so I did with FJ40 . I have a question about the suspension geometry this time. I wonder why front and rear axles differs so much in the number of links. At the front you have 4-link setup with additional Panhard rods, while at the rear only 2 links with a Panhard rod. Does an additional Panhard rod limits the suspension flex at the front? Does the rear axle have any unwanted side-to-side wobbling?

Thank you! You get it right, this project means to me a lot, and I am glad that you like it! There is a video about the gearbox made by its designer: I bought cheapest RC lights in a local RC store, so I can not give you any link here. I guess any lights will be OK if the lams fit technic pinholes (I tool a beam and checked lights before purchasing). I tested myself 96, 98, 100 and 120 mm wheels from this shop. All of them "fits" Lego rims though 98 mm tires are visibly tighter than the Lego rims. 100 mm wheels fits greatly, but they seems to be softer than 98 mm one. Pathfinder has 98 mm wheels with original RC rims. I would say, this are not the best RC wheels on market (in terms of grip) but they have a good proportions and a perfect side support, so they fit a speedy SUV. Currently I am working on my Master Diploma in mathematics, so I have not started any fresh project yet. This summer I was going to build a proper RC version of Ford GT, and something with planetary hubs...

I respect your position here! Yep, RC technic makes a big step from the mechanical technic, as well as real Lego builds differ from 3D models (made in Studio.io). Personally for me, mechanical lego is more about details, scale modelling, clever gear mechanisms and so on... While RC technic is more about performance and optimisation of a technical solutions adapted from real cars. It is hard to swap from mechanical models to RC one due to the following arguments: completely redesign the chassis to fit electric components buy expensive motors & hubs keep the batteries alive (buy rechargeable batteries \ Li-Po) with a chargers Reinforce both steering system and suspension (Lego sets usually have unacceptable wobbling of suspension arms etc...) Simplify the transmission (not 8+R gearboxes) to minimise losses avoid extra details to achieve a better power to weight ratio deal with plastic dust and dirt in the transmission deal with broken plastic gears and other plastic parts etc.. Thank you! I drive it outdoors regularly and every time my car catches peoples eyes ;-) To be honest, speed really affects the overall driving experience. Same conclusion made @2GodBDGlory with his Toyota Land Cruiser 79.

Hey! Just a quick update here. I made a car jack! This allows me to visualise the weight distribution of a Pathfinder. Once I have a car in my garage, I always made different technical upgrades for it. This time I made a trial version of my car with planetary wheel hubs and aggressive wheel pattern. What do you think about it, guys?

Greetings, Eurobricks! I am proud to introduce you my longest and most complicated project! It took me over 2 months to fix all the technical problems revealed in driving tests. Pathfinder is the universal off-roader built for regular outdoor driving. Features: all wheel drive with remote-control 2-speed gearbox Triangulated 4-link live-axle suspension both at the rear and front Brushless motor 1000 kv, 3S Li-Po, GeekServo, RC LEDs Strong transmission: carbon-fiber axes, metal bearing all around, metal U-joints. Realistic 98 mm RC wheels Underbody protection and custom mudguards Every Boy Dream I guess every Lego boy dreams about technic RC car to play with, at least I did. Since 2014 with a release of a legendary set 9398 Rock Crawler, I wanted to build myself a working and "playable" RC Lego off-roader. I was only fourteen at those days, so it took me a while to save money for a 9398 set. The day of joy turned for me to be the first regret in Lego... I was not satisfied with 9398 performance. I spent a lot of time trying to improve the set, but nether succeeded. Every time I felt the lack of power in my car. At the same time the Lego technic community has been growing in numbers, and many RC Lego off-roaders were shown by technic pioneers. I was inspired the most by Sheepo`s Land rover Defender and RM8`s Toyota Hilux. I decided to build Sheepo`s Defender chassis due to the strict limitation of parts available. Well, that car never moved even with wheels attached. Every time i pushed the gas U-joints in the driveshafts got broken. I guess it was caused by some mistakes I made in the chassis. Anyway, the second regret in RC Lego technic caused me to abandon Lego for 3 years. Time passed and Buwizz brick was presented to the community. It provided more power than the PF battery unit. This bring back my hopes of building and RC car with Lego bricks. My first successful project with a BW2 brick was an RC mod of Chevrolet Corvette. Through the couple of years I upgraded my technic parts collection, which allowed me to try bigger and more ambitious projects. With my RC version Jeep Wrangler the dream come true... A true RC off-roader driven by 4x PF L-motors and powered by BW3 unit provided a good speed and torque. Well, if my goals were achieved with jeep Wrangler, than I should stop my story here... The increased power and speed, revealed another problem: the transmission was struggling from plastic dust and hard outdoor conditions... With my next three project I ensured that there is no pure-Lego solution for this problem. Before going further let me explain the goals I wanted to achieve: Performance over details Efficient and durable transmission protected from dust and axle-wearing Max speed over 8 km/h Rigid chassis, capable to survive big bumps Precise handling (caster angle, proportional steering, physical control) Ground clearance over 3.5 studs, off-road geometric passibility 2-speed remote-control gearbox RC setup adapted to Lego and custom parts It was clear to me that plastic Lego parts would not allow to achieve my goals. The key components that required an upgrade were the wheel hubs and the 5x7 frames which hold differentials. Luckily to me I was not the only person on Earth who had this problems. Few AFOLS in Russia developed their custom wheel hubs and 5x7 frames with metal bearings! I ordered them without asking a price! These parts reinforced the weakest components of Lego cars, which allowed me to build several RC projects, such as: Blue Mamba V2, Wilde Beast and Falcon. This project used not only an improved transmission but also a new RC power and control system, which was able to feed PF motors with a constant stream of power. In fact, the system was so powerful, that PF motors started struggling from over-heating. Since I was in a mood of using custom parts, I get myself a Brushless motor setup adapted to Lego. It was designed by another Russian AFOL: a brushless motor A2212 1000-1200 kv placed in a custom Lego-compatible planetary housing. With a new purely RC electronics I started a new phase of advanced Lego technic engineering. Before challenging myself with a big project I decided to test Brushless motor to see its capabilities. I built a Dragonfly buggy V2 with brushless motor and a Unimog trial truck. Both projects proved the power of a Brushless motor. General layout By gaining experience with a Brushless motor in the Unimog project I decided to build a proper off-roader, which I was dreaming off for many years. Since the brushless motor has the dimensions similar to PF XL motor, I decided to use a classical chassis layout with a steering motor attached to the front axle, Brushless motor placed right behind the dashboard and a battery box in the trunk compartment. My Unimog had a similar layout, so I used it as a reference, though some changes were required. The first and most important change I had in mind was the scale. Since I wanted to drive my SUV outdoors, It should be capable to deal with natural terrain, so It should have a decent ground clearance. This can be achieved with bigger wheels and as a result a bigger scale. The choice of wheels As all of you know, the development of a new car starts with a choice of the wheels, which I have a plenty of. You will joke on me, but a plenty does not mean I have the one I need! Let me explain why. Lego has two most common rim diameters: 1.7 and 2.2 inches in diameter. Unimog used 85 mm RC tires placed onto 1.7 inches rims. Such wheels has a great proportions but they was not big enough for my new project. All bigger wheels were based on 1.7 inch rims. As a result they were disproportionally wide. The two sets of 95 mm RC wheels did not fit the future project as well. I surfed trough the net and found a great set of RC wheels, which you can see now on my Pathfinder. It was another win for me! Transmission Since I wanted to use an RC wheels I had to swap the planetary hubs to to the custom hubs with metal bearings. This swap changed the driving characteristics of a car dramatically as well as caused several crucial problems in transmission. Indeed, planetary hubs took a lot of stress from the transmission away, so I had to reinforce the whole transmission in all possible ways. Firstly, I used the reinforced differentials with 12:28 gear reduction. Further I used carbon fiber axles and metal U-joints. Finally, I used custom parts with metal bearings to divide the transmission from the other car components. This prevent any gear skipping and axle melting. Since I wanted to build a fast SUV but not another crawler, I decided to use open differentials both at the front and rear axles. However, I added an auto-lock system to the rear axle at the beginning of the project, which were removed later for practical purposes. Two drive shafts meet together in the middle transfer box. On the upper end transfer box is connected to the motor through the custom planetary gearbox. Gearbox is remotely controlled and has 1:1 and 1:4 ratios. Transfer box had 24:24 gear combination at first, but after driving tests I decided to slower the car down by putting 20:28 gear reduction instead. It turns out that both planetary gears in the motor and in the gear box require lubrications, otherwise the fast spinning satellites get melted. I learned this lesson in a hard way by having two serious breaks during driving tests. I had to order new parts, that costed me both money and time... Front axle The overall geometry of a front axle was taken from Unimog. I kept the upper suspension 6L links, but changed the lower suspension arms to the brick built one. I still do not understand why, but such combination of links provide a great geometry allowing decent flex angles and a slight positive caster angle (then the suspension get loaded by the weight of a car). At the same time the front axle is well protected from side-to-side wobbling. Reinforced lower suspension links provide a great protection for the front driveshaft. In an unfortunate scenario when springs can not absorb all bump energy, lower links prevent the front axle from being pushed backwards, which saves the driveshaft. The wheel hubs were made specifically for live-axle suspension. In combination with inverted 6L suspension arms they allowed me to build a sturdy and compact front axle. Luckily for me, they fit into the rims of my new wheels perfectly: the pivot point of the wheel sits inside the wheel contact patch. Rear axle Unlike the front axle, the final version of the rear axle differs a lot from the one used in the Unimog. Unimog has a 3-link free-swing rear live-axle, which would not fit a faster SUV with the gravity center moved closer to the rear axle. This was easy to fix by attaching springs to the live-axle itself. The real challenge for me caused the geometry of a rear live-axle. Similar to front axle I wanted to use brick built lower suspension links. I made them few studs longer but the 3-link set up did not work at all! Even without the springs rear axle refused to flex normally. I changed the lower links to the 9L Lego links, which gave me a normal flex angles, but this only revealed another problem. I found that with a 3-link setup the driveshaft moves significantly from side to side as well as changes it`s lengh. This might work for crawlers, but it was totally unacceptible for a fast car, so I had to redesign the rear suspension from scrach. In order to keep the driveshaft from unwanted movements, I made it parallel to the lower suspension links. From one side links have a ball joint and from the other just a regular pin connection. Such construction resists the side-to-side wobbling quite nicely, but uses an admissible plastic deformations to flex (since one end of lower links has a pin connection). The single upper arm was changed to a pair of triangulated links. As a result I achieved a decent geometry of the rear axle. Probably one may ask me why I did not use classical solution for the rear axle, given in Toyota Hilux by RM8? Well, because of scale and my main goals of rigidity. That solution worked greatly for 1:14 scale cars built for indoor trial. As long I was building a bigger car which supposed to achieve higher speeds, I had dial with much higher kinetic energy and thus potential load on suspension and transmission. Thus I had to reinforce the suspension as much as possible as well as reduce any unwanted wobbling. The resulting rear live-axle securely hold the drive shaft and does not cause any load on it. Speed VS off-road capabilities After I finished front and rear axles, I had to choose the spring setup. Lego has a very limited springs variation both in length and hardness. The common solution of this problem is to play with the mounting points. One principle I understood very clearly: the closer springs are attached to the wheels, the better responsibility is achieved. Further, the responsibility of suspension fall down significantly if the springs get attached incorrectly, so they bend with the suspension flex. Further I had to decide how soft I want the spring setup to be. The softer it is the better off-road capabilities, but it does negatively affect overall control and stability on high speed. Since the real SUVs are oriented on the speed and control, I decided to do the same choice. My favourite hard 9.5 L springs come very handy for that. Do not get me wrong, with a proper geometry of the suspension, Pathfinder has a great suspension flex (comparing to the real cars), but it clearly can not compare with mad Rock crawlers. To be honest, I would prefer the springs to be a bit softer (0.8 x current hardness) but Lego does not bother about making good suspension kits. Bodywork My favourite real-live off-roaders are Toyota Land Cruiser Prado and Mitsubishi Pajero sport, but I did not build their replicas due to the low skills in modelling. The shapes of the car appeared naturally for me. Firstly I found that 15L wheel arches perfectly fit to 98 mm wheels. The only 15L wheel arches I had came from Lego set 42069 Extreme adventurer. One of my old projects came in my mind shortly. Once I tried to build a Purple Pickup with parts from 42069 set. Well, I was not happy enough with the overlook of Purple Pickup, but I modified the front part of it to use if the next project, namely Wilde Beast. Now I wanted to modify the front part once more to fit my current project. I wanted to build the car in purple colour once again, but Lego does not produce many parts in purple. I found a great 3-d party set containing a plenty of purple! Namely this was a Sembo Technique 701028 set. Summary Before saying my verdict I want to mention the driving tests I made for Pathfinder. All the following tests are presented in the video. Max speed test: max speed is about 10.5 km/h Turning radius test: 0.86 m Stability and handling test: I tried to dive between cones in Zig-Zag trajectory on max possible speed. After 10 minutes training I was able to drive it with average speed over 5 km/h. Low speed suspension test: The car did not performed good here, to pass it a softer springs required. High speed suspension test: Suspension absorb high speed bumps greatly. High stair test: Due to off-road geometric passibility and high torque Pathfinder passed the test even with open differentials. Almighty hill test: I tested the maximal backward roll-over angle, and car was capable to climb into 60 degree hill. You might say that crawlers can do better, but come on guys, this not a crawler, but a short wheel base SUV! Multiple driving tests showed that such placement of a motor protects it from dirt and dust. However I made an underbody protection and custom mudguards to protect the transmission and the cockpit of the car. Now I can give you the conclusion: This project costed me a lot of money and time to finish, but at the end I get myself a robust RC Lego car, which is very fun to drive around. With this project I showed to the community what is not possible to achieve with pure Lego bricks.

A great model indeed! I personally prefer PF version since It uses the benefit of motor shapes! The body seems to fit the chassis very nicely without causing extreme load on it! Well done!

The bodywork is coming nicely! Have you tried to implement the positive caster angle to the front axle?

Indeed! I was going to suggest the same idea here, but you made it quicker! ;-) First time I saw this design in Attikas pickup:

Hey! Welcome to our small Brushless club ;-)

By the way, Nivas are well known for their Low-power engines, moreover, the whole transmission does not allow to overcome an increased torque of a boosted motor! A agree with you that 4 XL motors seems to be very unusual solution here, especially in combination with 5:1 portal reduction. I would use again 2 BM and reinforced open diff at the front with gear combination 12:28 and permanently locked gearing 12:28 at the rear. This would give me a plenty torque without any load on transmission (even Lego U-joints will work here)

Oh man! you made another topic I can not miss! 8 Studs of ground clearance seems to be an overkill to me ;-) I guess such a crazy off-road tuning was inspired by this guys:

You made a great investigation here! That was a pleasure to read through. I have 2 C+ hubs, Mindstorms 51515 set and a bunch of C+ motors, but have not interest in using them, cause I have a plenty of PF stuff: from almighty XL to the fast BM ;-)

Spoilers, spoilers, spoilers ;-) Cant wait for it! Does it relate somehow with the new chassis you have posted today? The discussion about row-bar usage is a small part of the car stability problem. With the Supercar it is well known that the suspension needs to be stiff and responsive. Road cars are build for medium speed, safety and comfort, so they need to have a soft suspension to deal with bumps, but at the same time they need an anti-rowbar for "fast" driving on the Highway for the safety reasons (in order not to fall off the road on speedy corners). Crawlers does not need an anti-rowbar for the maximal flexibility, but they are not pretending for the fast driving. The stability of SUVs is somewhat questionable to me, because SUVs should go both fast on- and off-road. This problem is not widely-presented in Lego builds because most of Lego Technic RC SUVs are remarkably slow (under 9 km/h). On such speeds any spring suspension will work (especially if the springs are mounted to the live-axles directly). Currently I am working on a presentation of my new RC SUV and I will try to mention the stability VS off-rad performance topic there. As far as I am concerned, modern SUVs widely use electronics to have both stability and off-road capabilities. A smart independent suspension (with pneumatic setup), ABS and several other electronic assistants replaced classic solid axles and mechanically lockable differentials. Sadly I can not use this Ideas in my Lego cars...

There is no easy answer to your question. It depends a lot on the traction of each wheel, wheel profile, wheel base, weight distribution, steering angles of a front wheels and the overall speed and other things. If I would build a new car, I would test it with both open and locked differentials to see the difference in your particular case.

Oh man... I am speechless! Thank you for a nice presentation and a great truck to look at! I found your post in the morning and it basically made my day! A few days ago there was a conversation on EB why Western Europe technic guys prefer SUVs to Supercars. I found a reasonable argument that time, but now I understand, how madly I am in love with SUVs! I was scrolling the EB forum for the couple weeks, skipping most of Supercar topics. Indeed they a very technical and has breathtaking look, but my heart does not stick to them. I am a performance-over-the-look guy, and you truck have healed my heart! Another fun fact is that I build my own SUV lately and currently I am working on the presentation. It has the similar scale to yours as well as the same philosophy behind the build. I wish we could drive our SUVs side by side one day!... Now I want to speak about technical stuff. Bodywork. Well done, the car is recognisable! Also I love the bed-design. I do understand what it takes to squeeze a rear axle under a flat bed without limiting its articulation. As I understand, your truck has no openable doors, and I am totally ok with it as long as It decreases the weight and add the rigidity to the chassis. Drive and steering. I appreciate the efforts you put into V2 of a chassis. The SIMPLICITY ARGUMENT really works here! 2 Buggy motors works greatly here. Your words "I think the truck was fast enough to be fun, and had very responsive suspension, making rough terrain a lot of fun." was proved in the video! Not many people are honest in their presentations! An outdoor RC car should have enough speed (at least 5 km/h) to be "fun to play with", and your truck is even faster! Speaking of the steering... I am not pleased with it, to be honest. Are you planning to use GeekServo in the future (cause you already have RC controller on-board)? I will improve the steering of your truck a lot! At the same time you will not need a MK 6.0 which add its weight. Finally you will fully enjoy a responsive RC transmitter both with Drive and Steering. Suspension. 4-link suspension is totally avoided in Lego sets, and I am so bored with both standard independent suspension and Live-axles using ball-connector as in 9398 set! Without the doubt, your truck has a great articulation, though it is too soft in my opinion. I am not a fun of rubber bands and prefer shocks! Due to my researches, the best way to make a responsive suspension with shocks is my mounting them as close to wheels as possible. There is a whole big deal to set the shocks correctly, keeping both articulation and stability on high speeds. As you have shown, anti-rowbar helps a lot, I used a carbon fibre anti-rowbar in my Buggy HORNET to achive high-speed cornering. I wonder why you put an anti-rowbar at the rear axle, but not to the front? It is well-known that front outer wheel has the most load in the fast corners, so there is a deep reason for placing ant-rowbar at the front. Finally, I am worrying about the front axle. It looks very compact and realistic, but it does not look strong enough to survive any bump on a high speed. I would use a classic solution with 5x7 frame. Also the front axle has negative caster angle, which is causes problems to the high speed stability. Transmission. As I said, I love the simplicity of V2 transmission! The whole setup with planetary hubs, reinforced differentials works greatly! It is great to see how planetary hubs fit into rims! This should decrease the turning radius of a wheel a lot! The weakest part of your truck are the drive shafts! Legois U-joints are strond enough for this truck, since it has planetary hubs, but the geometry of a front shaft is wrong. It needs to be 3 studs longer (9 studs instead of 6) to mach the length of suspension arms. Otherwise you should use make a length-varying shaft. Moreover, it is bent too much on my opinion, this increases the stress on it, and reduces efficiency. Especially, if you would put a front axle at a positive caster angle, you will need to redesign the front driveshaft. I saw in the video that the front driveshaft fell apart couple of times. I guess, it is caused by its wrong geometry. If the car meet a serious bump with the front wheels, the front drive-shaft faces the destruction wave because it is not well-secured by the lower links of the front suspension. To make a proper protection you should follow three steps: make the driveshaft parallel to the lower links of the suspension make sure, that the front axle does not wobble from front to back with the driveshaft removed (this will convince us that the drive-shaft does not carry any load from the front axle) reinforce the lower links by using brick build one. The summary. I really appreciate the efforts you put in this car. It is an eye-catching piece of technicality! The whole chassis is very fresh comparing to the standard Lego solutions, but it has several problems, which require fixing. Hope to see more progress on this car soon! P.S. Some photos of the chassis will be appreciated!

Hey! That will be another project for me to follow! Keep Up! I appreciate your goals, especially, the first one. This is actually my main principle of engineering ;-) Though I would not use legoish portal hubs with a long wheel base to keep "decent" manoeuvrability.

Hey! That is a really cool footage and we wish to see your BATPOD in more details!