Lean Virtual Pivot steering system suitable for Creator Expert cars

[roeltheworld]

Hi all, 

I got the BMW E30 alternative model of the 10304 Camaro by Firas, which is a stunning rebuild and highly recommended. 

That model however does not have a steering mechanism due to parts available, so I wanted to create a suitable virtual pivot mechanism that would fit in that scale of cars.

https://rebrickable.com/mocs/MOC-196487/ysmajor/virtual-pivot-steering-15-stud-cars/#details

It could be that the position of the 1x2 thin liftarms right next to the 24-tooth cog is illegal, as there is a little pressure between the parts when attached.

Here it is in the E30. I have changed the wheel rims with something I had lying around, but the 10304 tires are the same size and work well with it.

Here is the steering in action (with HOG system going underneath to the backseat):

[tseary]

Nice work. Virtual pivot is definitely the way to go at this scale and smaller. This is the first time I've seen it driven by gears rather than a linkage, and it even has different steering angles between the inner and outer wheels.

A possible solution to the illegal fit would be to replace the white arm with a #1 connector, 3L axle and axle connector. It should be in compression so it won't pull apart, although it may not be suitable for a motorized model.

[pleegwat]

There may be a solution with this part, though that would mean a different gear ratio and possibly more slack. I thought there was a version based on a 24z gear but I can't find it offhand.

https://rebrickable.com/parts/24014/technic-arm-with-gear-8-tooth-and-15l-axle/#part_usage

[2GodBDGlory]

Another option that might have slightly less stress on those gears would be to build it such that the axlehole on the gear only goes to pinholes on the steering beam. Normally, that would make the gear do nothing, but if you left that 2L beam on the top, it would fit between two of the teeth and fix the gear to the arm. It would just then have the advantage that the beam isn't forcing the gear to rotate a half-tooth away from where the axle fits it. Nice work, though!

[roeltheworld]

Cheers for thinking along here fellas!

It's possible to use 2 flat 1x4's with a 1x2 pin/axle on the end. Just that it doesn't look great and requires the wheel wells to be spacious.

Perhaps Lego will be making those 1x3 flip flop beams that Cada has one day, as they would fix this issue:

 

[mpj]

4 hours ago, roeltheworld said:

Perhaps Lego will be making those 1x3 flip flop beams that Cada has one day, as they would fix this issue:

You can use this connector to act as a 3L flip flop beams.

[pleegwat]

17 hours ago, roeltheworld said:

It's possible to use 2 flat 1x4's with a 1x2 pin/axle on the end. Just that it doesn't look great and requires the wheel wells to be spacious.

You could also use a 1x4 half liftarm with axle holes at the ends in combination with a 1x5 half liftarm with pinholes throughout.

[roeltheworld]

That's a nice option too. I added that idea to the image below.

I was thinking of a 1x3 connector with a 1x2 connector, linked with 1x3 thin liftarms:

Edited October 2, 2024 by roeltheworld

[Zerobricks]

Use piece 2393 as a hub.

[roeltheworld]

I wanted to see if the system would fit in the 10295 Porsche. So I gave it a shot and I am quite pleased with the result:

This is the Targa version (modded a little spoiler with left over parts, and I think the black tires are cooler)

So first step was to remove the old system and put in the replacement pivot system. The steering axis had to be moved up one stud, so I made a modified version which is actually better than my original above. I'll add the update to my rebrickable later on.

The thin pivot system fits perfectly: 

I used the 1x4 thin liftarm with wide axle hole together with a 1x5 pinhole thin liftarm. That 1x5 beam holds the gears together to avoid slippage.

As you can see below, I used a larger cog together with the 8-tooth and this works really well.

The movement of the wheels is now quite good, and definitely better than the original.

I'm sure some of you can mod the steering linkage more efficiently, but for a proof of concept first draft I am quite happy with this experiment.

 

Edited October 3, 2024 by roeltheworld

[gyenesvi]

This is a really nice solution and good to see it being polished and improved step by step!

The only thing I'm curious about is the improvement over the original solution. I only have the Mustang, and in those rims, the wheel hub fits inside a bit, so the steering pivot point is quite okay to start with. Do you have some comparison shots with how the original one pivots?

Also, can you tell where the pivot point falls more or less? It seems to me that it is quite a bit on the outer edge of the wheel (is that realistic?), and so the inner edge gets really close to the fenders.

[Stereo]

1 hour ago, gyenesvi said:

Also, can you tell where the pivot point falls more or less? It seems to me that it is quite a bit on the outer edge of the wheel (is that realistic?), and so the inner edge gets really close to the fenders.

If you extend the converging links to the point where they connect, that's the instant pivot point.  With this type of geometry it does move front to back as you steer, it's not always above/below the axle.

[Mikdun]

On 10/3/2024 at 5:45 PM, gyenesvi said:

It seems to me that it is quite a bit on the outer edge of the wheel (is that realistic?), and so the inner edge gets really close to the fenders.

It does indeed, but this is way more realistic than original geometry.

Looks much better, this is how it should come from Lego.

 

[roeltheworld]

I've been playing around with the system, and figured out a tighter mechanism. The Porsche has smaller wheel wells than the Camaro so there should be less forward and backward movement of the axle. This movement is affected not by the moving 'arms' or beams, but by the connector that holds the wheel axle. With a 3-stud length connector, the movement is about 1 stud forwards and backwards. 

The original design has another problem, which is that the wheel connector is 3x3 in size, and this is too large to fit inside the 49.5x20 wheel rims. That forces the wheels out, which makes the movement much worse. You can use the 49.5x14 wheels of the Camaro, but they don't look as good.

So, I made a two stud axle connector, and this has a forward a backward motion of about half a stud either way. Also it fits better in the wheel rims. Sadly, the rotation is a little less pronounced, and the rear arms/beams are weaker than the front ones that have the gears attached.

You can adjust the length of the outward arms between 4 and 6 studs. It won't matter. The new axle connector can have either axles or pins through them.

The gears need to be changed from 24-8-24 tooth, to a 20-12-20 combination, due to the degree rotation of the arms.

Above shows an early prototype.

Here it is in the Porsche. As you can see they still touch the edges, but as my Porsche is a shelf queen anyway it will do just fine.

[steph77]

hello!

 

This system works well in technic models too ;)

impossible to steer such shortened wheelarches without virtual pivot (or proper rims, but that's another story)

 

 

Edited October 10, 2024 by steph77