[MOC] The Wannabe Tatra

[Attika]

Good people of Eurobricks,

let me give you my first take on the planetary hubs:

Please excuse me for the lenght of the video, it's meant to show the developement stage by stage.

I had big expectations towards the new hubs, since they've been announced. I realised, these hubs will solve the problem of the stress on drivetrains, yet will raise a new challenge. Due to the increased torque on the wheels, the frame (chassis) and the bracing of the suspension will be the new weak link. A wanted to have a finalized rig to the date of the release of the hubs. The backbone of the design came from a five years old chassis concept, it was a non motorized chassis:

To mimic the geometry of the new hub, I've used the old ones with some extension, so it can be easily swapped, when time comes:

The concept of the chassis came together quite well, thanks to using techniques well practiced in my early years. But there was still a long time till the release of the new hubs. Driven by curiosity, I've planted two PF XL motors in the middle of the chassis, making them drive two axles each. One for the front axles, one for the rear ones. No additional gearing has been added, the motors were connected straight to the differentials. 

Of course it had to be tested, hat's the part around one minute into the video:

https://youtu.be/PGQpUrOS-NQ?t=59

Came with a surprisingly satisfying result, despite the usage of the old cv's and hubs, yet it was understandably far from being a "crawler" it meant to be. Also at this point I was short of claas tyres, so I've used some similar size rc tyres on the front 4.

Got the  tyres eventually, still a lot of time till the hubs coming though. As the final design was gonna use 4 buggy motors, time came to make the change:

Same principals, like with the XL motors: No gearing added (slow output used), 2 motors drive the front, other 2 for the rear axles. Now feeding that much buggy motors would require 4 buwizzes. Or one well sized rc lipo that can comfortably supply 2 sbricks. 4 buwizzes cost about 400-450 pounds, while the lipo comes for 30 pounds. Any question? 

At this stage (still no new hubs) it was an obvious, yet pretty crazy idea to hit the tarmac. So I did. That's what you see at 2:16 in the video: https://youtu.be/PGQpUrOS-NQ?t=136

I had a lot of trouble that day with the bluetooth connection, brought a head on crash int o a container. It was heart-, but no plastic breaking.

Finally the hubs came by the post and the picture got full. I've also planted another servo for steering (2 in total now)

Indoor durability test at 3:27  https://youtu.be/PGQpUrOS-NQ?t=207

Climbing test (60 degrees) at 4:18 https://youtu.be/PGQpUrOS-NQ?t=257 Hereby I apologize for the dark enviroment at this recording

 

Peek on the suspension at 3:12 https://youtu.be/PGQpUrOS-NQ?t=191

 

 

Lego should not be used outdoors... ahm, okay... 

Outdoor test from 4:55 in the video. https://youtu.be/PGQpUrOS-NQ?t=295

 

I came to the verdict, that the new hubs worth their money. In a usage that abusive, you see in the video the hub-cv connection definitelly require some lubrication. I've been using silicone oil and no downside appeared so far. Here is the difference it makes:

That's it so far, a little spoiler at the end of the video. Hope it's gonna catch some expert eyes... 

 

 

 

[jorgeopesi]

IMO Lego is good to learn, teach or simulate moves but never for hard playing. I have done a lot of machinery and always more stronger than necessay even losing aesthetics but I already knew that it would be for just imitate the real machine or play carefully, even RC metal toys get damaged, what we expect from plastic ones?.Anyway I have to get those hubs because I will can build more stronger plastic toys. 

 

Edited September 15, 2019 by jorgeopesi

[Attika]

3 hours ago, jorgeopesi said:

IMO Lego is good to learn, teach or simulate moves but never for hard playing.

I guess that is the very essence of this hub. Somewhat a gamechanger. Surprisingly No part has been damaged in the process. I lost one ball joint pin though , but that happened earlier, came out from the old hub.  

 

It seems to be a very chatty topic. 

 

 

[jorgeopesi]

2 hours ago, Attika said:

It seems to be a very chatty topic. 

It is a shame because I love the Tatras, an obsolete suspension concept that I still like. Eurobricks is less and less chatty and even more on Sundays  .

[suffocation]

Your "wannabe" models are light-years ahead of my "serious" attempts at anything

Great no-frills truck. Got a couple of questions about the 60° slope test:

- What was the gearing?

- I know it's hard to tell but did it sound like the hubs were under any unreasonable strain? It'd be nice to compare max torque / max effort / max speed / max whatever experiences with these hubs. For what it's worth, I spent an hour driving a 4.5 kg model around today (flat surface only) and the hubs and joints still look pristine. The gearing going into the hubs (4x4) was 1.68:1 from four L motors.

[Attika]

15 hours ago, jorgeopesi said:

It is a shame because I love the Tatras, an obsolete suspension concept that I still like. 

 It's just a wannabe. This truck is just as much a tatra, like I am an NFL star....

15 hours ago, jorgeopesi said:

 Eurobricks is less and less chatty and even more on Sundays  .

Let's see, if monday is any better. 

 

14 hours ago, suffocation said:

- What was the gearing?

I should say, there wasn't any. I've been trying to keep the drivetrain as simple as possible. Every additional gear connection would eat up efficiency, so both, the XL and the buggy motors were connected straight to the differencials (buggy motors with the slow output)

Bottom line is: motors- differential (a 20/28 ratio) - wheelhubs 1/ 5.4. that's it. There is one thing I forgot to mention above. I've locked the diffs for the outdoor runs and for the slope test too. With open diffs, the max angle it climbed was 52 degrees With locked diffs, of course the crawling ability goes up, but the manoeuvrability goes down. I mean the turning circle grows. Just a a pro vehicle, requires (and offers) the right setup for the given task.

15 hours ago, suffocation said:

 I know it's hard to tell but did it sound like the hubs were under any unreasonable strain? It'd be nice to compare max torque / max effort / max speed / max whatever experiences with these hubs. For what it's worth, I spent an hour driving a 4.5 kg model around today (flat surface only) and the hubs and joints still look pristine. The gearing going into the hubs (4x4) was 1.68:1 from four L motors.

The hubs did not show any sign of being on the edge of their capabilities. The model is close to 3 kg, I was frequently checking the hubs an the cv heads inserted. After quite extensive and- let say- intense usage there is some sign of wear, (check the left one on the picture in the original post) but knowing what they took, the lack of these signs would be more surprising. Let me highlight, the sign of wear I'm talking about is a hardly visible line in the groove of the cv head. It still works as good as new. Personally I'm very happy with these hubs. They didn't just brought me back from a longer dark age period, but in the meantime prooved themselfs very well crafted. I would say, a sensible outdoor usage does not mean any problem. Where sensible means, not to dip it into mud or sand.  I've yet to find out what is their limit regarding the weight and torque they willing to take.

[ArsMan064]

Really good model) As I see, new planetary hubs really useful here. 60 degrees is very strong :)

[dpi2000]

Nice to see you share the building process,great,new planetary hubs seem to work well.；）

[Attika]

On 9/16/2019 at 4:06 PM, ArsMan064 said:

Really good model) As I see, new planetary hubs really useful here. 60 degrees is very strong :)

 

On 9/24/2019 at 12:07 PM, dpi2000 said:

Nice to see you share the building process,great,new planetary hubs seem to work well.；）

Thank you guys, sorry for the delay, had the pickup to focus on. So yes, the hubs I couldn't even dream of. And it's here. Don't forget to give it some lub. Extends the lifespan.