Ok so the part vendor told me that they could send the parts via express delivery and it can  arrive on the 20th. I bought the parts, and according to the tracking app the part's estimated arrival is in the morning of Aug 21. Meanwhile I'll build the model from what I have and fix any problem that might appear.

I'm running low on creativity so I might need the inputs of the pros here.

I managed to fix a part of the steering function.

The lime 1x3 liftarm will connect to the inner pin hole of one of the two 3x3 T-shaped liftarms. That will select either the 4 wheel steering mode or crab steering mode.

 

There are two problems I need to fix:

1. Supposedly, the red pin with pin hole connector (15100) will rotate around the lime liftarm and will push or pull it. In reality, sometimes, due to fiction, the red connector does not rotate, and instead stay perpendicular to the liftarm. That causes the whole group of lime liftarm and red connector to rotate around the connection point with the T-shaped liftarm instead. I need something to block the lime liftarm from steering into the adjacent lines.

In bigger models the selector bar is at least 5L wide, so there can be blockers between 3 steering mode. In this case the selector bar is only 3L wide, so the 3 steering modes are right next to one another. The surrounding area is quite spacious so it can accommodate some bulky structure.

 

2. I'm unsure about how to design with the middle position. The preferred outcome is that the steering axle should be locked so that only the first axle is steerable.

 

Suggestions are welcomed.

This is why 42102 only had front steering!

Can you show a little more about the selector bar for the steering?

Can you just replace part 15100 with part 22961 to reduce the friction? Can 22961 will braced so it will not slide out of the 1x3 liftarm?

17 minutes ago, Thirdwigg said:

Can you show a little more about the selector bar for the steering?

It's the 3L part of the yellow 5L axle. The red connector slide between the two ends.

 

17 minutes ago, Thirdwigg said:

Can you just replace part 15100 with part 22961 to reduce the friction? Can 22961 will braced so it will not slide out of the 1x3 liftarm?

That works kinda well. I already tested this alternative. The lime liftarm is now 5L long, and one end is blocked by the turntable so it won't slide out. Sometimes the the liftarm still deviates to the adjacent line though. I feel like there might be another solution.

Edited August 18, 20231 yr by Ngoc Nguyen

9 minutes ago, Thirdwigg said:

Can you just replace part 15100 with part 22961 to reduce the friction? Can 22961 will braced so it will not slide out of the 1x3 liftarm?

That was also my initial thought, however, that doesn't really help. 

After building it, I've realized that the issue with rear axle's steering remains the same - instead of being locked in wanted position and being always parallel to the vehicle's frame, it slides on the axle and causes total chaos.

I've tried a different approach - instead of sliding the whole assembly from one side to another, place three of them next to each other and select steering mode by just inserting the axle to one of them. This had worked well for me.

5 minutes ago, MP LEGO Technic creations said:

I've tried a different approach - instead of sliding the whole assembly from one side to another, place three of them next to each other and select steering mode by just inserting the axle to one of them. This had worked well for me.

You mean, like this?

10 minutes ago, MP LEGO Technic creations said:

I've tried a different approach - instead of sliding the whole assembly from one side to another, place three of them next to each other and select steering mode by just inserting the axle to one of them. This had worked well for me.

This sounds like a good idea. Can you fit this @Ngoc Nguyen?

Maybe I'm still a little confused by the rear connection of the (now) 5L liftarm to the rear steering mech? Are you connecting it on the top to the tan 4 axle?

ed: I went back to the first photos (page 1). Are you still going to use part 98585?

Edited August 18, 20231 yr by Thirdwigg

2 minutes ago, Thirdwigg said:

Maybe I'm still a little confused by the rear connection of the (now) 5L liftarm to the rear steering mech?

4 wheel steering and crab steering are selected like this.

 

I still dont know how to design the middle one, which is the front axle steer only.

9 minutes ago, Ngoc Nguyen said:

4 wheel steering and crab steering are selected like this.

Well, are you sure that both aren't the same ones? To me it seems like that, though I could've overlooked something.

The original setup looks like this - steering liftarms aren't mirrored.

Edited August 18, 20231 yr by MP LEGO Technic creations

9 minutes ago, MP LEGO Technic creations said:

Well, are you sure that both aren't the same ones? To me it seems like that, though I could've overlooked something.

Oh wait you're right they both result in the same thing.

Back to the starting point I go..

Can you add part 98585 back on the tan axle then use axles (rather than the red pin with stop) to connect the single lime liftarm to Pinhole right, pinhole left and a center hole by above placed hole (sorry I can't render this right now)?

Then just remove the 3x3T liftarms.

Edited August 18, 20231 yr by Thirdwigg

5 minutes ago, Thirdwigg said:

Can you add part 98585 back on the tan axle then use axles (rather than the red pin with stop) to connect the single lime liftarm to Pinhole right, pinhole left and a center hole by above placed hole

You mean like in the initial idea? Then you would unfortunately get the same effect, only inverted (e.g. instead of two circle steering modes two crab modes).

Edited August 18, 20231 yr by MP LEGO Technic creations

One, eternity, lehter.

 

Left and right are for 4 wheel steering and crab steering. Bottom position locks rear axle's steering, which corresponds with front axle steering only.

IT WORKED! 

Video coming soon!!

I seriously respect the perseverance!

Great job!

Tadaaa

https://imgur.com/a/I1JbWyo

 

Great job!

Now hurry and finish the job 

I need a 3x5x1 substructure with 4 pin holes in the red holes below, and one pin hole go up in the middle like below.

 

I already came up with one solution, which is the design above, but in this design the middle pin hole can rotate, while I want it to be fixed.

 

That is another version but it doesnt look quite sturdy.

 

Any idea?

Edited August 20, 20231 yr by Ngoc Nguyen

Does it have to be rigid? does the sticking out pin hole need to be a pin hole, can't it be an axle? Is there any clearance around this sticking out pin hole? If that's supposed to be fixed, then I'd assume you could use at least one stud beside it to reinforce it.

Here are my attempts, I'd put a bet that the last one is something that could be useful, unless the other two pin holes in black connectors on the sides are important:

32 minutes ago, SaperPL said:

Does it have to be rigid?

Preferably rigid, yeah.

That structure is used for the steering mode switch. 

As you can see in the link https://imgur.com/a/I1JbWyo the bottom left corner pinhole is attached to the rear axle. The top two pin holes are for crab and 4 wheel, while the bottom right corner is for front wheel steering only.

The problem is that at any one time, only two holes are fixed. That means the steering structure can actually wobble and messes with the steering. I intend to make it slide along a vertical axle to prevent the wobble.

 

Therefore the sticking out pin hole should be a pin hole. 

Can't the last design, the one on the bottom, be used here though? It looks like you could have that LBG pin on the left side of that sticking out pin hole riding on the middle axle if you only have just one connector there on that yellow axle.

I’m happy you figured this out @Ngoc Nguyen, now I hope the parts can arrive. 

There is enough space for a 4x5 instead of 3x5