Didumos69

I agree.

Cool contest ?. Would a kite be allowed.

Maybe try newer parts? Is it always the same side that comes loose or both sides? Don't use glue. As a last resort, do this, but you have to take the front apart up to the gear rack and make sure the screw does not stick out.

@MultiDoc, there is one more thing that could be the issue with the ticking of the steering. Underneath the headlights sits a light-bluish-gray dog-bone piece. The long axles inserted in this piece, which run all the way to the gear rack side of the module, should stick out half a stud. If the ones at the top side of the dog-bone piece are inserted deaper, they will interfere with the gear operating the gear rack. That could cause a rattling sound during steering.

Great images @MultiDoc! The steering links are indeed the weakest link, but they shouldn't come out that easy. I can do this without any problems: Are you sure you're having the parts in place that should lock the towballs? The parts that have half their pins sticking out. It should look like this (I left the suspension arm out): As for the clicking of the Servo. I don't have that. Isn't the gear slipping? That can happen when you forget to install the two thin 2L levers underneath the gearrack:

It's not visible in my renders, but the differential meshes with an 8t gear at its 24t side, just like in @KevinMoo's renders. Only in his renders the 8t gear sits on the same axle as the 16t clutch gear at the other end of the differential. In my case this axle is split into two, one for the 16t gear and one for the 8t gear, so no clutch gear. To lock the differential I make the axle with the 16t gear engage with one of the outputs of the differential. I can't do that by making the axle with 8t gear engage with the other outputs, because that axle rotates 3 times faster. EDIT: Added renders.

Thank you for your reply and your advice @KevinMoo. I will be carefull and I will testing stuff before finishing the whole design. I do see some difference between your approach and mine. You use a clutch gear to transfer drive on an axle that rotates at different speed. That gives a lot of friction, more than you would think, but it is of course not the cause of the differential problem. Another difference is the torque. I geared up the motor-output with 3:1 and 5:3. You geared the motor-output down with 3:5. Gearing down means more torque. I hope to tackle the differential problem with very smooth running gears (all axles supported at both ends, no chance of squeezed gears and no clutch gears on axles running at different speed) and high spin / low torque in the differentials.

I'm afraid not. The 8t and 16t gears along the sides of the differentials are on different axles. The differential locks need to make use of the axle with the 16t gear, otherwise the output of the differential would be forced in a speed different from the differential itself. So the gear locks need to sit at the 16t side of the differentials. I also tried with the locks in front of the diffs, but then the 90-degree stepper would have to move to the back side of the gearbox which causes all kind of problems. I think I will leave it as is. Yeh, it is the V8 input that makes the distance. Btw, I am not so much afraid of too much torque in the transmission. My approach is 1) to gear up the XL-motor output with 3:1 and 5:3 to get the inputs for the gearbox, and 2) to gear down the transmission output close to the wheels. This means the transmission (gearboxes) spins faster with less torque. The downside is that there will be more friction, but I'm putting in everything I know about getting gears and axles to run smooth. Really everything. Nice idea, I'll do that during my next session. Thanks! Actually, I have no clue on what kind of suspension I will put in. The u-joints are just place-holders for the axles. I also don't know if I will be using the standard LEGO wheel hub. As for making the bevel gear housing tilt; I could do that, but I'm afraid that when the housing is only supported by the drive train itself, I will get more friction. I think I will first try without suspension at all, just to see how it perfroms on a flat surface. I'm actually thinking of something like this (Zarooq SandRacer), but I really have to see how everything works out in real-life. I will certainly drive it on ice when I get the chance. No, I didn't count the idle gears ?. I'm putting in everything I know about getting gears and axles to run smooth, so I hope that will help. I also have no clutch gears transferring drive while not engaged with the axle they are attached to. Only where the drive trains cross, but there will minimal speed difference between the axle and the gear, especially when driving straight. I did think of all these options and it may very well be that I have to change my plan, but for now I will aim for a 4-speed model with high spin / low torque in the transmission. If this won't work, I can quite easily change the gearbox input ratios, for instance to 1:1 and 5:3. I might also add an M-motor for the v8. Thanks! I prefer to have the differentials open by default, so I will first try @zux's suggestion. Update: Yesterday evening I spent some time on the main structure. I worked my way from the area around the differential locks to the back and to the front. The main structure is 7 studs high, which allows me to make it really rigid. I'm following my standard layered approach: I work lengthwise on odd layers (counting from bottom to top) and transversal on even layers. By sticking to that guideline consistently, you end up with many opportunities to put long liftarms through the structure. I added attachment points for two BuWizzes to the sides (the studded plates and pins above).

Thanks! I appreciate it. Because I want the axles coming out of the differentials to be supported by a liftarm directly next to the differentials. This is to prevent slipping gears. You are guessing right. I get your point. Will take an other look, but in the current setup moving the gears to the front would make them interfere with the stepper. I think so too. It should be able to continue driving with one wheel off the ground, which won't even happen when it would have too much suspension travel.

Yes, bracing everything well will be the next hurdle. I left space for some transversal beams and all axles are 'in grid'. Hopefully that will help. That's a nice suggestion ?. I will ask my kids. I fear this is the most challenging build sofar. I really want a model that performs and can shift gears while driving. Yeh, the U-joints are probably the weakest link, but they only need to handle a quarter of all the power. Also in my Greyhound I used U-joints and bevel gears at the end of the drive train. The number of gears may seem overwhelming, but the number of gear meshes involved in each gear is 4, which is really the minimum in a 4-speed AWD model. I managed to make sure each gear uses the same number of gear meshes. I hope this model will be a good marriage between a crawler and a race buggy. Hence the gearbox. We'll see about the long axles. They are geared up, I hope they can handle the reduced torque. I will first try your suggestion, thanks! Thanks! I am probably going to learn a lot during this project ?.

RC Off-roader with Dual Diagonal Drive I think I'm onto something that will get me through the winter. Summary Dual diagonal drive means: 1) having two separate drive trains with equal torque while 2) preserving the advantage of having an open distribution for cornering and 3) passing diagonal tests without using differential locks. Background I have been playing with this idea for a while already, especially after seeing @KevinMoo's dual drive models (Mitsubishi Pajero and Dual-Driveshaft Pickup). @KevinMoo rightfully addressed the vulnerability of LEGO parts in RC models and the fact that using independent drive trains for the left and right sides, loses the benefit of differentials while cornering. This got me thinking. Using independent drive trains for left and right in a 4WD model does indeed drop the benefit of differentials while cornering, but what if we would pair the wheels diagonally, so pair the left front (LF) wheel with the right rear (RR) wheel, and pair the right front (RF) wheel with the left rear (LR) wheel? The resulting 'dual diagonal drive' (I borrowed the term from the electric skateboard scene) would serve two major benefits: While cornering, the LF and RR wheels will average to a speed that is very close to the average speed of the RF and LR wheels. So not having an open distribution by means of a differential between the two drive trains is much less of a problem as with separate drive trains for the left and right side wheels. On a very uneven surface, where one or two wheels may lose contact with the ground, the wheels that do have contact are typically lined up diagonally, see image. With dual diagonal drive, the vehicle would still have traction, even without locking any differentials. Only on slippery surfaces, there are chances of spinning wheels. So this is what I'm thinking of. We start with the basic dual diagonal drive setup: Two separate drive trains, one for the LF and RR wheels and one for the RF and LR wheels. The drive trains cross using two 24t gears and an auxiliary 16t gear that sits right underneath the auxiliary axle for the other drive train. So no clutch gears are involved in this crossing. I inserted a 1L Technic liftarm inside each differential - idea from @Madoca 1977's Toyota Land Cruiser 80 - to prevent the bevel gears from popping out. Next we add a manual locking feature, which closes the differentials with a single lever. This locking feature will force each pair of wheels involved in one of the drive trains to have equal speed. Now we connect each XL-motor to one of the differentials, using a small 4-speed gearbox. That means; two separate 4-speed gearboxes. This may be a bit ambitious, we'll have to see in real-life whether this is feasible or not. I might fall back to two 2-speed gearboxes. I did pay attention to the amount of torque in the transmission though. I geared up the XL-motor outputs and geared down the transmission output. That makes the transmission spin faster with less torque. The gearboxes are operated synchronously using a 90-degree stepper, which is controlled by a Servo-motor. Each gear shift axle has its own 90-degree limiter. And finally the outputs of the XL-motors are transferred to a fake V8-engine via a normal differential. The sole purpose of this differential is to combine the XL-motor outputs for the fake engine. For the steering I'm thinking of using a servo motor. I don't really like the directness of steering with a servo-motor, but the steering link attachment points are moved one stud backwards, which confines the steering angle. This adds to better handling and protects the CV-joints in the wheel hubs. I don't know where this is going to end. I'm not even sure about the exact kind of car I will be targeting, but it sure needs to be some kind of all-rounder. Comments and suggestions are welcome.

Nice read @brunojj1 ! This is how I experience building too, although I wouldn't want to compare my skills with yours, not when it comes to aesthetics.

Great! Did it meet your expectations? I also added the orange version to Rebrickable. Instructions are the same, but the parts list is different and I added a note on which parts to replace while building.

It does indeed not rotate freely when holding one side and flicking the other side, so I don't think you need to worry. For a good comparison between before and after lubricating, you would need to take into account the force applied by the weight of the finished model, which is about 500gr per turn-table. This force works orthogonal to the rotation plane. In my own build I started without lubricating the bigger turn-tables. But after some test-drives I noticed plastic dust and the black side of the turn-table would also not rotate as freely as it did when the parts were new. So I lubricated the the turn-tables, which was hard, because they were already assembled. The lubricant is not only to keep the turn-tables rotate smoothly, but also to protect them against wear. It is important though, to not apply too much lubricant, for it shouldn't pile up inside the turn-table. But the effect you are experiencing is perfectly normal.

Thanks for your interest! Yes, you need 2 Buwizzes. The instructions incorporate all latest changes. The preferred inner tires are the 44771 tires. The outer tires need to be the CLAAS tires. The way to install the tires is like this:

I started rebuilding using the instructions myself. In that process I also cleaned my 9.5L shockabsorbers. They still had silicon spray on them. On a funny side note, I made the photo sequence instructions in a more or less public space on the University of Twente. I took two days off last week. The space is quite big, there is a lot of light and there is a coffee-corner nearby. What I didn't know, was that on the second day the University had organized an 'open day' for future students. The space where I was gradually taking my Greyhound apart was crowded with youngsters and there parents all day. The general perception was that I was a planned exhibition, part of the 'open day'. I got a lot of questions and it turned out to be great fun to be a little bit part of the event.

In this case it is about lubricating individual parts (turn-table internals and shock-absorber internals), so I think doing it before assembly is better. The shock-absorbers have been designed in a way that the compression force is not completely longitudinal. The lubrication is only to make the shock itself compress and decompress more fluently.

I started off without lubrication and did indeed experience the smaller hubs to become looser. After installing new ones I lubricated them, but with silicon spray. This worked better, but silicon spray was not the right choice, even though I did not experience real problems. It is better to apply the lubricant before assembly. You don't want to spoil lubricant on any axles that are not supposed to slip out of any axle holes. The turn-table was very hard to lubricate, because I didn't want to dismantle it. I was affraid to damage it and introduce unintended friction.

I found these images from users Belair58 and GBCPeter on doctor-brick.de, which show a way to assemble cheap hard 9.5L springs:

Aha, I didn't read your first post correctly. Stalling while shifting gears is caused by the fact that in the original setup it may happen that two driving rings are engaged simultaneously: At the point where one driving ring engages, the one that was engaged is not yet fully released. The solution is to extend the catches as shown here. This also avoids the red clutch gears from being squeezed between liftarms and driving rings. EDIT: Also, the original model does not have a proper way to limit the shift-axle to 90-degree positions. This may cause half shifts, leaving the gearbox inbetween shifts, with the risk of having double engaged gears like I explained above.

I took the advice shared by @Berthil in this thread, but there are also other suggestions in that thread. Note that not all WD40 is PTFE spray. I forgot about that when I compiled the instructions, so I accidently put the wrong WD40 image in my instructions, the text was correct though. I've corrected the image. This is the corrected image:

See this post (also scroll up to @schraubedrin's post and down to his later post).

Good to know! Hope everything works out fine. Be sure not to confuse 99773 (Technic Beam Triangle Thin - Type 2) used inside the front suspension module with 2905 (Technic Beam Triangle Thin - Type 1).

Instructions are online. If there is anything unclear, please let me know.

I spent 6 hours on the instructions today. I'm halfway done. 350 photos sofar. Yes, I use Stud.io 2.0. I don't know. I made the LDraw file by exporting it to LDraw in Stud.io. I don't use LDraw myself. EDIT: I made a few small updates to the files, based on some differences with my real life build.