[WIP] RC Off-roader w/ Dual Diagonal Drive

[Attika]

Just now, Didumos69 said:

Fixed that

And you've fixed the orientation of the tyres too. OCD, isn't it?

[Didumos69]

On 11/29/2018 at 1:29 PM, schraubedrin said:

On a completely unrelated note: could you maybe make a screen-recoding of you working in LDD? (e.g. with OBS)

I think digital examples are one off the best methods to exchange ideas. It's just that i'm so slow using it, that i normally don't bother.
Therefore i'm interested how you're building such complex, free floating structures.

I tried recording some design sessions, but the issue is that most of the time nothing happens, because I'm thinking. Also, I have surpassed the stage where things are really floating. However, here is a short impression of how I build in LDD. The most important trick I use is taking a few parts out and use them to rotate new parts and then put it all in place again. In this video I am working on the rear axles. The final design is quite different though.

[schraubedrin]

6 hours ago, Didumos69 said:

here is a short impression of how I build in LDD

Thank you, that was already interesting. I was surprised how confident you're building in this dense tangle of parts without using the "hide-parts-tool"

It's unfortunate that you're in the middle of the project, it's the beginning or changing big subsections that i have the most problems with.
If the oportunity arises, don't hesitate to upload a longer video, even if it's 80% static image. It's perfect to watch during building sessions.

Maybe you'll participate in the TC15, than there's an opportunity to record the beginning of a project

[Didumos69]

I ordered all the parts I need. I opted for black, because it looks less messy. I also found a way to firmly connect Porsche rims to the turn-tables (secured with 6L steering links sticking out the rims). So I'm a bit on a cross-road as to what kind of car this is going to be. Perhaps I should let the performance decide...

[pagicence]

5 hours ago, Didumos69 said:

I also found a way to firmly connect Porsche rims to the turn-tables (secured with 6L steering links sticking out the rims).

Can we see those particular connections? I'm very curious about what's going on inside the Porsche rim.

Edited December 19, 2018 by pagicence
typo

[schraubedrin]

Out of curiosity: did you try the Unimog Tires (Tyre 94.3 x 38 R) ?

They might fit the SUV-look

[Didumos69]

37 minutes ago, pagicence said:

Can we see those particular connections? I'm very curious about what going on inside the Porsche rim.

Here you go. It might need tweaking when I build it in real life, but I'm confident it will work out fine.

3 minutes ago, schraubedrin said:

Out of curiosity: did you try the Unimog Tires (Tyre 94.3 x 38 R) ?

They might fit the SUV-look

I'm going to try that. I will have to insert the race tires the way I do with the CLAAS tires though.

[Didumos69]

During the holidays I finally had time to build. First results are actually quite pleasing. I had to make a few tweaks to make it buildable and I skipped the turn-table-based wheel hubs for now (I used normal LEGO hubs), but so far I didn't need to change anything to the gearing. Here you see it accelerating from 1st to 4th gear. No slipping gears sofar.

EDIT: I did have to make one change: I changed the differential lock to lock the differentials individually, without linking them together. The drive trains are spinning in opposite direction to give correct input for the V8-differential. This doesn't allow them to be linked the way I had in mind. I don't see this as a big concession though.

The differential lock still needs tweaking, because the driving rings easily slip when the lock is engaged. Apart from the differential lock everything works as expected.

This is what it looks like right now:

Edited January 5, 2019 by Didumos69

[MultiDoc]

Well all I can say is that now I know what I’ll be building next. Waiting eagerly for the complete MOC.

[JTS]

It looks fantastic!

I do hope you stick with the Zarooq / offroader direction though. Will be keeping a keen eye on progress.

[brunojj1]

6 hours ago, Didumos69 said:

... so far I didn't need to change anything to the gearing. Here you see it accelerating from 1st to 4th gear. No slipping gears sofar.

...

I´m really impressed . Big applause for this fantastic achievement which I consider as a historical milestone you´ve set there !

[Attika]

I had doubts, you 've pooved me wrong. So business as usual.  Nicely done. 

[ArsMan064]

So, now it look really interesting. It going to be great model!

[Didumos69]

Thanks guys!

A little more info. It currently ways 1600+gr and consists of 1400+ parts. The track width and wheelbase are exactly the same as my rugged supercar.

14 hours ago, JTS said:

I do hope you stick with the Zarooq / offroader direction though. Will be keeping a keen eye on progress.

I think it will be more like a Subaru XV/Crosstrek, however it will probably be a beam-based open body. I also think I will skip all interior details, just like with real RC models.

14 hours ago, brunojj1 said:

I´m really impressed . Big applause for this fantastic achievement which I consider as a historical milestone you´ve set there !

I think the trick to avoid slipping gears in the differentials is 1) to have two separate drivetrains, so not all power flows through one differential and 2) to gear up instead of gear down , i.e. to have high spin / low torque in the gearboxes which include the differentials.

1 hour ago, Attika said:

I had doubts, you 've pooved me wrong. So business as usual.  Nicely done. 

I did skip the bad offset turn-table based wheelhubs. It also gives a better trackwidth.

Here's a short video in daylight showing some details:

 

Edited January 6, 2019 by Didumos69

[pagicence]

That suspension is so smooth. Since you'r going towards "regular" car body, what do you think about making the doors open like the rear doors on tesla model x? I think it's an interesting mechanism.

Edited January 6, 2019 by pagicence

[BusterHaus]

Are you lubricating the moving parts from the start? Or seeing how long they will last unlubricated? 

[Didumos69]

16 hours ago, pagicence said:

Since you'r going towards "regular" car body, what do you think about making the doors open like the rear doors on tesla model x? I think it's an interesting mechanism.

Thanks for the suggestion, I will take a look at those doors.

15 hours ago, BusterHaus said:

Are you lubricating the moving parts from the start? Or seeing how long they will last unlubricated? 

I didn't lubricate anything this time. Maybe I will eventually.

Btw, I had this kind of AWD diagonal test in mind when I started:

And this seems to work out fine too. This has nothing to do with the differential lock (which is not engaged in the video below), it is simply because of the dual diagonal drive as explained in the OP.

Edited January 7, 2019 by Didumos69

[Didumos69]

I shot one more (bad quality, sorry for that) video to show the gear shifts. This also shows it's top-speed in ludicrous mode. I might try to gear it up a little by changing the gear ratio in the toggle joints close to the wheels to 1:1 (this now is 5:3). Btw, I think I will rename it from RC Off-roader to RC Allrounder.

Edited January 7, 2019 by Didumos69

[ndm1306]

Hope you can make a very nice and realistic bodywork!

[Didumos69]

14 hours ago, ndm1306 said:

Hope you can make a very nice and realistic bodywork!

We'll see, I have no clue where this is going to end. At least not when it comes to bodywork. At this stage I'm mostly focused on it's driving characteristics. And to that end I'm actually quite content already, but there is one thing that bothers me a little. When it rides at full power in 4th gear, it sometimes has a hard time shifting back to 3rd gear. Shifting gears actually requires quite some power from the servo motor in general. The fact that shifting is most reliable in ludicrous mode subscribes that fact. So I will try to gear down the servo, and see if that makes shifting 100% reliable. The idea is to drop the differential locks and move the servo 2 studs backwards. Two studs space should be enough to gear down the servo with two 12:20 gear meshes, which makes a 9:25 ratio altogether. I only need about 28 degrees rotation for a shift, the servo gives me 90 degree and by gearing it down I will have about 32 degrees. That leaves some space for play.

I made a test setup, which works fine, see video below. Next step will be to redesign and rebuild the structure around the servo.

[Didumos69]

On 1/11/2019 at 8:16 PM, Didumos69 said:

Next step will be to redesign and rebuild the structure around the servo.

I redesigned the structure and was also able to hold on to the differential locks. However, in the first make, the differential locks slipped under higher torque. The driving rings are pushed out of the clutch gears, even though I use the white connectors with ridges. The problem is that these ridges allow too much movement of the driving rings. So in the refactoring I also had to address that problem, and I found a solution.

I built the idea in a separate assembly to check if it works, and it does. Here are two videos showing how I made sure the driving rings remain engaged better with less play. The biggest challenge was to make it such that it does not squeeze the driving rings against the clutch gears, which would cause friction. In other words, the auxiliary security - with two half pins and two cam-pieces as key players - should only reduce play, not eliminate play completely.

The first video shows the difference with and without the extra security.

Edited January 28, 2019 by Didumos69

[Didumos69]

Here's a little more info on the differential locks. The idea is to have a single lever for controlling two differential locks, one for each drive train. The whole setup works around the shifter-servo, which moved backwards by two studs to incorporate some down-gearing. Here are two cutaways showing the entire differential locking setup. Inbetween the two driving-rings you see the cam-pieces and half pin that together serve as a helper to keep the driving rings engaged. Btw, inside the differentials you also see the 1L beams that secure the bevel gears inside the differentials, as was suggested by @zux. So far they do an excellent job.

Edited January 28, 2019 by Didumos69

[Didumos69]

Update: The differential lock is working now and the gear shifter is also working better, but it still has a hard time shifting back from 4th to 3rd gear. So my plan is: I will drop 4th gear and add a 3rd-to-1st gear block instead. I will also drop the down-gearing in the toggle joints at the ends of the drive trains to somewhat compensate for the lost speed in 4th gear. Here are two short videos showing shifting and the differential lock (with some help from my daughter ).

Edited February 2, 2019 by Didumos69

[suffocation]

I'm still struggling to wrap my puny brain around the engineering of this masterpiece

[sirslayer]

@Didumos69thanks for the reply on youtube...   im still trying to understand the diagonal drive..  it looks good on paper but after watching your video , i didn't see the performance advantage after watching your video.. did i miss something?? seem to be running a bit slower compared to your last awesome model from last year ..