Leif

Well, it seems like an idea down the drain... rack and pinion is not part of the solution since they need to be of different length, ackerman vs parallell. something with LA but how the heck gear them for different speeds and different direction. anything is possible but it would take a huge amount of motors to administer the settings. anyway, a 4x4x4 where Ackerman may be disregarded could have crabbing, just reverse second axel. could be good enough for a smaller crane!

Yeah I know! I have 5 XL motors on the shelf som I am ready to add Naturally I will also sooner or later build a larger superstructure, to match scale!

thanks a lot! Can you point out where to reinfoce drivetrain? first pic of drivetrain is old, first version, and not is use, 2 last pics are current and it feels quite strong? The truck is still a skeleton so reinforcements will be done, for example around worm gear for steering. funny thing is clutch wheel disengage long before any beam pushing so no dealbreaker... I would like to clarify that I meant gear ratio to 2nd and 3rd axle steering, rack and pinion - not the drivetrain if anyone thought so

The batterybox is basically just a container with a power and direction switch, along with some overload protection. it will not lower the volts from 12 to 9V. remember, normally you put 6x1.5V batteries in the box = 9V... do not try anything with 12V, it is over the top! Also, make really sure you get a 9V DC (not AC) transformer...If you are uncertain about power, volts and electricity, do not take any chances, it can only lead to expenses and burnt equipment!

oh yeah, a drilled hole and a chipped corner is the only "damage" you do to the batterybox. remove wooden staffs and you are back to normal.

That is a very compact solution, may be the best so far. I cannot see if you are using double U-joints or u-joint + cv-joint? good job, now if only the steering geometry...

Thank you Balrog for the good design. yeah I am on the same track. there are unfortunately no way to build any more compact than this. The red circle area is of course a problem if the angle of wishbone is to steep, so that has to be calibrated so to speak. I also had a beam connecting upper and lower wishbone in order to keep them together at all time! If I may hijack my own thread, what would be the best build for driven, steered, independent suspension and the Unimon tires - without any wobble? the portal hubs can reduce wobble since they also have an axle through the wheel, not only the three pins. they also make stronger drive train since you can have proper axle and U-joints, rather than the CV-joints which surely are quite fragile.

If you have the time to build a mockup I would greatly appreciate this. My build was a quick & dirty mockup so suspension and some more things are really just thrown upon the build, there are some things to optimize if I shall go forward with the build. the pivot point of the steering, too far away from the wheel is the biggest issue for me and I cannot really decide whether to go forward with a portal hub project or look into another solution altogether. To get Ackerman as well would of course really push the solution forward!

thank you for a very good answer. It may turn out as I suspected, portal hubs are not the proper component for driven, steered, suspended. too bad, I like how stable they are, no wobble or anything!

A really good idea but can I still have the axel driven in that case, cardan positions?

yes that is correct but I think my original message and question maybe got lost on the way - steering geometry with portal hubs; good or bad? compared to real trucks?

Maybe nitpicking but isn't it true that for a proper drivetrain a differential between each pair of wheels is needed? Just like you need a center diff on 4wd.

Yeah I know, Quick and dirty is nothing to take lightly... However, it turned and worked and is now teared apart, the build was just for confirmation of steering issues, and I am do not like the hubs steering qualities, am I wrong?

Some more pics of strong boom. Driving second boom. two worm gears directly on the racked gear. sturdy and simple, the cord for retracting third boom is attached under u-joint but you see the leftovers of the cord as well going out in the air. I haven't got the courage to cut it yet... Here you see cord coming up and going over the racked gear. this cord is for retraction of third boom. via pulley of course. Top of second boom with hook cord guidance as well Lower end of second boom with pulley for cord for the third boom. White panels on purpose! dont go any further... Third boom layed out Third boom dissected and in detail I am not sure the diagonal beams in the third boom are 100% "Lego Legal". It may be 1 micrometer or similar misfit but for the time being...nothing forced I can promise!

Yeah I've been stocking up om technic flagships and such for the last few months, got out of the dark ages this summer so it's been hectic... The counterweight is mandatory so it is quite high part count on this MOC the boom is really sturdy. Yesterday, without extending the boom but fully raised I was able to lift approx 1.2 Kilogram. extended boom, the numbers will drop of course and I will try to build some kind of bucket that I can fill with coins or similar to be able to measure exact performance of different boom lengths. I also need a better scale, has to measure below 1 kilogram. or just lift water, then I can do the math... Sure, I will take some more, and better pics this (Swedish) night for details!

Dear all, Based on the Ultimate 42009 and afol1969 extended and improved boom. I wanted to create a boom that was strong for real, to be able to lift something. Studded beams are of course part of the solution and after I bought the 8421 and the 8053 I was stocked up on these. I also bought some extra curved 11x3 from bricklink to be able to build at least a bit colorcoded! I dare to say this is a strong boom! 5 panels long main boom. 5 panels long secondary boom. 4 panels can and should at most be extended. 2 layers of studded beams, fixed with diagonally unstudded, and another 2 layers of studded beams for the third boom. the wire for third boom return is fed over the second boom racked gear, I find this a good solution for this wire. the second boom has small wheels at both ends for wire to run smoothly. I can post a pic of this tomorrow if someone is interested. I actually used the 42009 cord as boom driver. strong and not elastic. Reinforcements at the base of the boom, a lot of pressure here. The boom is the one from afol1969 that we all know a lot about, but I have added one layer of beams to primary and seconday boom in order to fit the enforced third boom. The lifting angle is quite good, the boom actually can touch the superstructure at max height. At the same time the boom can rest horizontally as well. I think this is close to max what a boom of this length can achieve. The next model would probably need 3-4 LA for lifting and so much reinforcements so it would soon be too heavy for its own good! more pics upon request and I now see that some of the pics have too much light, sorry for that! Lifting the Unimog cabin, my benchmark! Thin thread but strong. Still some color mixing on third boom.. A new idea for the propulsion of second boom, two worm gears directly on the racked gear. stable and simple. Reinforcements, reinforcements! the diagonal 11 beam is moved to the outside of the triangle after this test. My counterweight Budging but holding..

Thank you for the welcomes! Yes Eigenbrothel, I look into Swebrick from time to time as well. Good site and forum, no question about it!

I have searched the net a bit but I haven't been able to find exactly how a boom extends in real life. it can't be a "thread" in real life maybe chain or similar. I think, but I'm guessing that each section is extended using internal hydraulic actuator, most of the time, rather than racked gears. there are hydraulic actuators that can be compressed into themselves for several steps. most tipped beds have this solution. at the same time I have actually not found any proof that a real crane extends one section at a time, or all sections simultaneously. I really can't tell yet! I will continue to explore different setups and the final result will be true to real cranes! I will also only build a boom that actually works together with turntable and counterweight (batterybox or better) so my goal is not to reach for the sky but to have a realistic experience when it comes to actually lift something! At the same time I have also found that I think the outriggers actually can lift the 42009 ultimate off the ground. It is just a matter of engine power. One medium motor and a lot of gears is probably not enough to be able to lift the machine, but there is nothing wrong with the outriggers themselves although they can be redesigned not to bend so much! That being said, I am not in any way unhappy with the ultimate 42009 or the extended boom design that our fellow forum friends so nicely have given us for free! I am just trying to build something with my own flavour and style

Dear all, Long time lurker, first time poster first things first, my homework, here is my presentation: http://www.eurobrick...showtopic=99069 Even though this thread recently has been the subject of Gerger's mods and the work around this, I hope that my try of modification fits here as well. Bear with me, this is my first Lego in 30 years, and my first ever with studless pieces! My builds are so far not really MOCs, more "mockups" or "POC (Proof of Concept". Having said that, my build is not a beauty, nor a finished model. My first purchase since I became an Afol was the 42009. after that I, of course, built the Ultimate 42009 and after that added the Extended Boom as well. I am following Gergers work and I hope to build a 6 axle or even more in the future as well. I have never really liked the extension of the third part of the boom, using the thread. First of all, you don't wanna extend the third, and weakest boom at all times, second, the thread thinking is, at least for me, not really technic..! So, having said that, I have built a boom, based on the Extended boom we have seen here before, where the third part of the boom extends individually using worm gear and rack gear, just like second part. The clever thing - at least for me - was to use the spare part in the set, the read 8 tooth sliding gear, together with the 32L axle in order to have a sliding assembly following the second boom. I had to add a layer of beams to first and second part of the boom in order to fit rack gear. some things need more reinforcement, but as I wrote, POC - not MOC Anyhow, I am interested in you opinion about this approach. Not using thread for extending boom, not auto-extend third part and so on. Furthermore, it would be really a challenge to build a boom - and a crane that actually could lift some real weight, it is still way too weak for anything more than, for example 2 8043 buckets some pics, take it for what it is... (I hope I am following forum rules in regards of sizing and such, please let me know otherwise!)