[MOC] Mercedes Zetros 2733 - 6x6 - Full RC

[nerdsforprez]

2 hours ago, kbalage said:

A very impressive MOC with amazing level of details, congratulations! I'm just curious - I saw your other video where you mentioned that using XL motors was not as effective as the buggies, did you use 4 XLs previously with the same drivetrain? It's hard to believe that the geard down buggy motors would provide better climbing abilities than the XLs.

As commented on YT, just a terrific moc.  Functions really stand out. I do happen to have similar questions as to those expressed here....buggy motors are atypical for large, heavy mocs such as this. Even if you gear them down a lot the output shaft is unlikely to have the torque of XL motors, which have planetary gears built in, which are typically going to be more efficient than using  technic gears.

[1gor]

20 hours ago, Leonardo da Bricki said:

Awesome!  I was considering making a Zetros.... But you just shot my idea down! incredible truck, it has so many functions....

Just one thing to say. Please clarify the suspension type, this is not independent suspension; I believe all three axles are multi-link live axle suspension.

It has leaf springs suspension like you can see when you search for images on google.com with key words Mercedes Benz Zetros suspension (when I post link to image here it looks more like sausage...)

Edited August 31, 2017 by I_Igor

[Aventador2004]

you might want to shorten your post i_igor

[1gor]

14 minutes ago, Aventador2004 said:

you might want to shorten your post i_igor

Thanks, I've correcred post. It should show image of Zetros axle with leaf spring suspension but some browsers could not display image, so I post a little help about how to find the answer...

[TechnicSummse]

Wow, this is simply nice. 

I love a lot of functions combined in one model, and this one also looks just beautiful .

 

But i also have a question... if i counted corectly, there are 14 motors, 4 sbricks, and a buwiz... where the hell did you hide all this stuff?

All i could find is a l-motor and 2 servos, but not one single m-motor, no buggy-motor, and just 1 sbrick+ buwizz. Where are all the other motors/sbricks?

[jrx]

Hi there!

@nerdsforprez Below you can see the whole drive train. At first I hard coupled two buggy motors and then connected both to the drive train. From the output of the connected four buggy motors to the wheels I geared it down by ~ 1:50 - if @Sariel's Gear Ratio Calculator is right ;) (I think it is.) So the torque is increased ~ 50 times. This way I managed to reduce the force on the gears dramatically. In one of the first versions I used two XL motors. With their high torque they destroyed repeatedly the gears and I didn't manage to bring all torque to the wheels. Now it works really reliable. The chassis without superstructural parts (weight around 3,0 kg) managed a slope of 100% (45°). Now as the model is 1,5 kg heavier that's impossible anymore.

@I_Igor Yes your right. the portal is only very small to get some more ground clearance and gear reduction. You mentioned the suspension: I tried to replicate the leaf springs suspension as used in the real Zetros but I wasn't satisfied with it. So I switched to my solution the live axle with multiple links.

@TechnicSummse Thx a lot! The four buggy motors are an integrated part of the chassis and are located beneath the cabin. In the cabin there are five servos hidden. The L motor for the winch is in the front behind the bumper. The second L motor for the compressor is on the right side behind the lower black panel. The M motor for the rotation of the crane is in the middle under the black beams beneath the crane. The second M motor is in the black box behind the cabin. The last motor, the servo, is in the middle of the chassis deep down below the crane just behind the buggy motors and is used for steering.
Each one SBrick is behind the steps to the cabin. One SBrick is sitting between the compressor L motor and the chassis. The BuWizz hides behind the lower grey door and the Pneumatic cylinder of the outrigger on the right side.
For completion: Two pairs each of PF LED are used for the head- and backlights, two on each side for the turn signals front and rear. Last but not least 2 pairs LED I'm using for the flood lights on the roof.
 

[1gor]

@jrx now you know why I've sticked to Unimog in 1:17.5 scale 

[brickless_kiwi]

Its not till you have a look at your flickr account and see the guts of your zetros and then you can certainly appreciate the amount of detail behind the lego

[iv-tecman]

wow amazing work, this is what TLG should have done for their 6x6 : - ) no but this is an amazing MOC

Love the functions, really is a good model.

[TechnicSummse]

22 hours ago, jrx said:

 

@TechnicSummse Thx a lot! The four buggy motors are an integrated part of the chassis and are located beneath the cabin. In the cabin there are five servos hidden. The L motor for the winch is in the front behind the bumper. The second L motor for the compressor is on the right side behind the lower black panel. The M motor for the rotation of the crane is in the middle under the black beams beneath the crane. The second M motor is in the black box behind the cabin. The last motor, the servo, is in the middle of the chassis deep down below the crane just behind the buggy motors and is used for steering.
Each one SBrick is behind the steps to the cabin. One SBrick is sitting between the compressor L motor and the chassis. The BuWizz hides behind the lower grey door and the Pneumatic cylinder of the outrigger on the right side.
For completion: Two pairs each of PF LED are used for the head- and backlights, two on each side for the turn signals front and rear. Last but not least 2 pairs LED I'm using for the flood lights on the roof.
 

Thank you for the explanation, now i can see all those motors :D

But i did not realise the model is high enough to use buggy-motors verticaly. Thank you for the drivetrain picture.

 

Do you really need 4 buggy-motors to power it? I don't own a buwizz, neither a sbrick, but to me it seems 2 buggy-motors could bring the truck to your current speed easy, with just enough power suply. If i compare it to my high-speed-cars... i can drive close to 40kph with a 1,2kg heavy model with also 4 motors. I think it should be possible to reach 5-8 kph with 4 motors on a 5kg-model like yours.

Do your lights become darker if you start moving the truck? Did you meassure the voltage the motors receive when driving the truck? 4 motors at 6,5-7 volts should bring the same result then 2 motors at real 9v.

I know the truck is not build for speed...but i think it should be way faster with 4 buggy-motors fully suplied with power.

Edited September 1, 2017 by TechnicSummse

[jrx]

29 minutes ago, TechnicSummse said:

Do you really need 4 buggy-motors to power it? I don't own a buwizz, neither a sbrick, but to me it seems 2 buggy-motors could bring the truck to your current speed easy, with just enough power suply. If i compare it to my high-speed-cars... i can drive close to 40kph with a 1,2kg heavy model with also 4 motors. I think it should be possible to reach 5-8 kph with 4 motors on a 5kg-model like yours.

Now, as the Zetros is finished, I think two buggy motors could be enough - maybe. When I was building and planning my goal was tho enable the Zetros to manage a slope of 100% (45°). The nearly naked chassis made it, but not the finished truck as it is to heavy. So it's not about the speed but for the force. The Zetros is still able to climb a little. And it can go faster. I used just the "Normal" Position of the BuWizz to preserve the gears a little. If I go for the "Fast" mode the Zetros is noticeable faster.

33 minutes ago, TechnicSummse said:

Do your lights become darker if you start moving the truck? Did you meassure the voltage the motors receive when driving the truck? 4 motors at 6,5-7 volts should bring the same result then 2 motors at real 9v.

No, the lights are showing the same brightness at whatever action the truck is performing. I didn't measure the voltage while driving. Can't tell you exactly, in how far the different connectors of the buwizz are independent. Each pair of motors is connected to another connector of the BuWizz (through SBrick).

36 minutes ago, TechnicSummse said:

I know the truck is not build for speed...but i think it should be way faster with 4 buggy-motors fully suplied with power.

I can't be much faster (only while switching the higher power mode of the BuWizz) as I geared it down by ~1:50 and as I'm using the slower output of the buggy motors.

[TechnicSummse]

2 minutes ago, jrx said:

Now, as the Zetros is finished, I think two buggy motors could be enough - maybe. When I was building and planning my goal was tho enable the Zetros to manage a slope of 100% (45°). The nearly naked chassis made it, but not the finished truck as it is to heavy. So it's not about the speed but for the force. The Zetros is still able to climb a little. And it can go faster. I used just the "Normal" Position of the BuWizz to preserve the gears a little. If I go for the "Fast" mode the Zetros is noticeable faster.

Oh... i thaught the speed in the video was top-speed, because it allways went really slow when coming to a little hill, and the motors sound pretty stressed.

By the way... speed=torque ;) ... just depends on gearing.

But that's what i mean... i think it should be faster(stronger), especially when climbing those small steps on the stones.

2 minutes ago, jrx said:

I can't be much faster (only while switching the higher power mode of the BuWizz) as I geared it down by ~1:50 and as I'm using the slower output of the buggy motors.

Well, if i saw it right in the video (1 wheel-rotation /4-5 sec), your motor output speed is about 600-700 rpm. No load speed is about 1300 on the low output (at 9v). 

But maybe it is also the planetary gearing wich produces tons of friction, and eating torque.

 

 

[jrx]

Yes, the gearing produces some more friction.  It seems, that the lenght of the drive train  is a further problem. But for the moment I‘m happy with the Zetros. I plan a „spin off“ as one of my next projects. It will be a Zetros 4x4 with motors directly connected to the axes. So it should be faster and stronger and will be able to crawl.

[TechnicSummse]

1 hour ago, jrx said:

Yes, the gearing produces some more friction.  It seems, that the lenght of the drive train  is a further problem. But for the moment I‘m happy with the Zetros. I plan a „spin off“ as one of my next projects. It will be a Zetros 4x4 with motors directly connected to the axes. So it should be faster and stronger and will be able to crawl.

Please dont understand me in a wrong way... i really love your zetros, i just thaught there is a lot of power missing, if i think about having 4 buggy-motors there.

 

[jrx]

Don't worry @TechnicSummse  I really like to get honest feedback from the AFOL community. About the power: I think some of it is lost in the drive train, but it's still powerful (but not fast). Maybe you'll have a look at the earlier video about the final track test. You'll see, 1,5 kg less weight will make a big difference at ascending slopes 

[suffocation]

The friction induced by planetary gears does indeed eat up a ton of torque. Your theoretical output is around 500 N/cm, which is roughly the equivalent of 34 XLs; of course, practice is quite a different kettle of fish. It'd be nice to measure the effective output at one of the axles to see how much torque is lost along the drivetrain.

[jrx]

The planetary gear are not the problem as the don't have so much friction. I used brand new and clean turntables and they rotate very smoothly. But I agree, it would be nice to measure the effective torque at the wheels. The next days I'll busy with work but then I may build up a little experiment set-up to determine the torque. 

[TechnicSummse]

8 hours ago, suffocation said:

The friction induced by planetary gears does indeed eat up a ton of torque. Your theoretical output is around 500 N/cm, which is roughly the equivalent of 34 XLs; of course, practice is quite a different kettle of fish. It'd be nice to measure the effective output at one of the axles to see how much torque is lost along the drivetrain.

Hmm how did you come to  500Ncm? Compared to philos website, 1 buggymotor produces 5,7 Ncm.

-> 5,7* 4(buggymotors)*50,4(gearing)= 1149 Ncm

Compared to this, the XL-motor produces 14,5 Ncm ... meaning theoreticaly the output should be as powerful as 79 ungeared XL-motors.

But the XL-motors would rotate faster :D

 

Well but all this is just theoereticaly....and looked from the wrong perspective.

 

The mechanical power of one buggymotor (4,61w) is 2,1 times higher, then the one of a XL-motor (2,21w).

So at the end, this should be REALLY as powerfull as 8,34 XL-motors

Edited September 2, 2017 by TechnicSummse

[jrx]

While looking at the picture of the drive train: What's missing there are the gears for the three diff locks at the axles. They are another (small) source of friction.

[suffocation]

6 hours ago, TechnicSummse said:

Hmm how did you come to  500Ncm? Compared to philos website, 1 buggymotor produces 5,7 Ncm.

 

I used the low-speed value from Sariel's gear ratio calculator, which gives me 2.48 N/cm. But yeah, it's just inconclusive theory

[jrx]

Today I thought a little about the words from @TechnicSummse :

On 1.9.2017 at 10:50 PM, TechnicSummse said:

Oh... i thaught the speed in the video was top-speed, because it allways went really slow when coming to a little hill, and the motors sound pretty stressed.

…

But that's what i mean... i think it should be faster(stronger), especially when climbing those small steps on the stones.

So I watched the video again and it came clear to me what the point was. The simple answer is: The Zetros didn't got stressed at the little hill, I took back some power to to prevent the axes and the gears from damage.

Besides from that I for myself was curious why the Zetros performed that bad the last time I tried to climb a slope. So I took a closer look on the front axle. There I found the problem. The differential is the weak point. One cross axle slipped out of a gear and so nothing was working anymore. I repaired it and started a new Track Test - now successful. The 4,5kg heavy Zetros managed a ascending slope of 25° without hesitation. You can see it in the following video plus some more insights into my MOC.

 

[TechnicSummse]

Ok... this looks more like it should look like with 4 buggy-motors :)

[jrx]

Absolutely  It just kept bothering me.

[Aleh]

Very good job on video! Interesting to watch!

[jrx]

Thanks @Aleh!