[WIP] [MOC] Rocker-Bogie suspension

[roppie11]

Hello guys, I was just scrolling through the 'uncommon-suspensions'-topic when i stubled upon a picture of the rocker-bogie suspension. I don't know what happend but i was immidiatly fascinated and i iam thinking about building it in lego. Right now, i'm just in the phase of orientation and research so have the feeling i'm a little bit early with my topic

anyways, i am just really fascinated by how it works and i have googled a bit. I'm a really unexperienced builder so it may turn out into a fail. To be honest i never finished a MOC but i hope this will give me a push to finish it.

it would of course be nice if it is remote controlled driven and steered. I have no recievers by now. But when i need them (i promiss ) a lot of time will have passed by and in the mean time i have already bought a few new ones. I am wondering really hard if i will come into that stage but that's another topic.

the most difficult thing will not be to build the structure i think but i need axle 1&3 to be steered and the middel one to be driven and that all in such a way that it is not a pain to look at. I don't think that it is really needed to drive the 1st and 3rd axle to be drive because all wheels are touching the ground always.

then there is another problem. the left and right side must have the option to move relative to each other, so where should i put the connection and how do i made the connection sturdy without limiting the movement to much?

do you guys have any ideas and tips? they can be about above problem or just general biulding tips. they are really, really welcome, especially the beginner tips

I don't know when i will start building on this moc, there are a few more creations? at my working table and i have to do some research first.

Let me know what you think!

[andrewganschow]

It might make the build harder, but have you considered the rocky boggie suspension, but in an articulated setup so the axles don't need to be steered?

[Buddy010702]

Possibly try putting the weight beneath the rocker/articulation point of each side. If I am correct, it should keep it somewhat stable. Try that, although I can't guarantee it.

[JGW3000]

Check out both the official Mars Rover set, 21104, and the original IDEAS submission for LEGO rocker-boogies - neither of these can accommodate PF's, however. I believe that there are some larger scale technic-based builds in which PF's are employed, I'd suggest searching this forum, for example here or this EV3 version.

[PeterF]

Hi roppie,

I actually started building this a while ago.

the most difficult thing will not be to build the structure i think but i need axle 1&3 to be steered

I solved this with turn tables above the wheels, with motors in the legs, but it becomes clunky very quickly.

I don't think that it is really needed to drive the 1st and 3rd axle to be drive because all wheels are touching the ground always.

That's what I thought as well, but performance was horrible. Because the wheels move up and down so easily, they easily lose traction as well. Having only the front wheels with drive works better. However, for good climbing (which is what you want with this suspension) all wheel drive would be the best by far.

then there is another problem. the left and right side must have the option to move relative to each other, so where should i put the connection

Well, you can only connect them through the main pivot point that goes through the body.

and how do i made the connection sturdy without limiting the movement to much?

The connection can be made quite sturdy. Again with turn tables and two axles in the middle (one per side) which are linked with four bevel gears inside a technic frame. However, since you need 4-6 steered wheels and 6 driven wheels (or at least I did), the whole thing becomes quite large. Which means that the legs become long, and get a lot of play. This is why I abandoned the project in the end. It became very ungainly.

do you guys have any ideas and tips?

Yes, go for an unsteered version first, to get a feel for the suspension. It is great fun already!

Then build a version without suspension (4 or 6 wheels), only drive and steer. That is also great fun! I used mindstorms to get the steering to work accurately. But I think servo motors would work fine too. I implemented counter steering, crab steering and 'turn on spot'.

Good luck!

I hope you get further than I did

Edited May 10, 2016 by PeterF

[JJ2]

Sounds interesting, I might make a LDD of an idea I have if you need help.

[deehtha]

I made a similar setup for one of the contests here. The easiest way to keep the sides even is to think of the whole thing as a differential. The body is the differential housing, and the sides are connected to the output axles. Connect the sides with a trio of knob wheels. The center knob wheel should be stationary in regards to the body. The knobs gears are essentially the spider gears inside the differential housing.

[Imanol BB]

Hi Roppie, i saw this suspension in the uncommon suspension tread, and like you, i found it very interesting, now, if you are going to build it, how big do you think it would be? or at least, which wheels would you use?, because i think i could help you with all the transmission system, i think that the best solution, if the model is enough big, is to make an strong structure for the suspension system, and put axles thru it, the wheels would turn with turntables, and it is possible to make it all wheel drive.

[roppie11]

Check out both the official Mars Rover set, 21104, and the original IDEAS submissionfor LEGO rocker-boogies - neither of these can accommodate PF's, however. I believe that there are some larger scale technic-based builds in which PF's are employed, I'd suggest searching this forum, for example here or this EV3 version.

Like you said, the first two are useless for me. The others however are interesting. I want to take a look at the mars rover itself aswell. thanks for the suggestions!

Possibly try putting the weight beneath the rocker/articulation point of each side. If I am correct, it should keep it somewhat stable. Try that, although I can't guarantee it.

yes, it should be stable because the point of gravity is lower. It must not be too low otherwise it will slew over the ground all the time. but thanks, i'll keep that in mind.

Hi roppie,

I actually started building this a while ago.

I solved this with turn tables above the wheels, with motors in the legs, but it becomes clunky very quickly.

That's what I thought as well, but performance was horrible. Because the wheels move up and down so easily, they easily lose traction as well. Having only the front wheels with drive works better. However, for good climbing (which is what you want with this suspension) all wheel drive would be the best by far.

Well, you can only connect them through the main pivot point that goes through the body.

The connection can be made quite sturdy. Again with turn tables and two axles in the middle (one per side) which are linked with four bevel gears inside a technic frame. However, since you need 4-6 steered wheels and 6 driven wheels (or at least I did), the whole thing becomes quite large. Which means that the legs become long, and get a lot of play. This is why I abandoned the project in the end. It became very ungainly.

Yes, go for an unsteered version first, to get a feel for the suspension. It is great fun already!

Then build a version without suspension (4 or 6 wheels), only drive and steer. That is also great fun! I used mindstorms to get the steering to work accurately. But I think servo motors would work fine too. I implemented counter steering, crab steering and 'turn on spot'.

Good luck!

I hope you get further than I did

thanks for all your tips. It is a very good idea to build an unsteered version first!

I have no nxt's and servo's so we will see how the steering will work out. I'll remember to put drive on all 6 wheels. a pity that you're project never got finished and i am suspecting the same is going to happen with me. I will give it a serious try at least.

I made a similar setup for one of the contests here. The easiest way to keep the sides even is to think of the whole thing as a differential. The body is the differential housing, and the sides are connected to the output axles. Connect the sides with a trio of knob wheels. The center knob wheel should be stationary in regards to the body. The knobs gears are essentially the spider gears inside the differential housing.

oh, that's interesting. can you please tell me what contest it was?

Hi Roppie, i saw this suspension in the uncommon suspension tread, and like you, i found it very interesting, now, if you are going to build it, how big do you think it would be? or at least, which wheels would you use?, because i think i could help you with all the transmission system, i think that the best solution, if the model is enough big, is to make an strong structure for the suspension system, and put axles thru it, the wheels would turn with turntables, and it is possible to make it all wheel drive.

i have no idea how big it is gonna get. but i think i'm gonna use the arocs wheels. It are my biggest. I can use turntables but i have only 2 small and 3 big ones (1 modern one) so it's not possible to use that on all wheels. thanks for your reply.

also thanks to everyone who i didn't quote

[deehtha]

It was TC5.

http://www.eurobricks.com/forum/index.php?showtopic=102965&hl=

The 4th post has a shot of the mechanism. I had to use 3 12 tooth bevel gears instead of knob wheels. The only problem is routing drive and steering. On the real rovers, there are electric motors and steering servos at each wheel.

[roppie11]

thanks! I will try to put the motors close to the wheel indeed.

added later: That's a neat way of doing it! But i want my model to be a bit bigger.

[Imanol BB]

Hi again, i was also thinking to make a really big model (in LDD), using unimog´s wheels, and 1 motor on each wheel, it would use planetary rims, so it would be strong enough and wouldnt need too much space on the structure, the steering would be done by motors inside the robot, which would be connected to the wheels platforms by U-joints, i will make an small test, an if it is enough good i will post it.