Wind shield in Lego 8868

[Yevhen]

After looking at screenshots I  was surprised how easily a Lego designer set a wind shield in 8868 truck!

But when I was trying to replicate the wind shield, I found that the 7 studs beams (or 8 studs bricks) don't fit the distance between the hood and roof! There is 0.1mm backlash!

Also I have tried different schemes with use of combinations of bricks and plates to create a triangle with 7 studs hypotenuse, but no one of them works well.

To make the long story short, I think the Lego designer used a cheap trick to build the cabin!

 

Correct me, if I'm wrong.

 

P.S.Looks like 8872 and 8280 have the same problem.

Edited May 26, 2019 by Yevhen

[allanp]

There are a few things going on here. Firstly, the height of the hood (and conversely the lower mounting point for the A pillars (the 1x8 technic bricks that make up the wind shield)) are higher by 2 plate thicknesses relative to the chassis than what you would normally expect, when thinking of the classic beam, plate, plate, beam approach of stacking Technic bricks. But also, the cab is lowered by 1 plate thickness relative to the chassis. This results in an offset of 1 plate thickness in height than what is the norm, and also a kinda weird but totally legal construction of the chassis. This must have taken the designer a while to figure out and it's quite hard to get your head round but it seems the only reason they did that was to get the proportions of the big beefy looking truck just right.

Secondly, there is the use of grey pin connectors and axles to connect the top and bottom of the A pillars. The use of a grey (non friction) connector peg here is quite telling as it has some slop in it, meaning it will allow for a little bit of misalignment. This is really the only reason I can think of for using that part as opposed to the black friction connector peg.

Thirdly, there is also the fact that the roof isn't fixed to the horizontal, 90 degrees to the rear upright supports, which means the top mounting point of the A pillars can be moved up or down slightly to fit the A pillars. Yes, there is an axle going through the roof for the hoG steering, however there is some slop in the axle through the black 2x8 plate with holes which will allow for a small angular discrepancy without causing damage to pieces, or making it too difficult to assemble or disassemble, making it legal.

[Yevhen]

45 minutes ago, allanp said:

There are a few things going on here. Firstly, the height of the hood (and conversely the lower mounting point for the A pillars (the 1x8 technic bricks that make up the wind shield)) are higher by 2 plate thicknesses relative to the chassis than what you would normally expect, when thinking of the classic beam, plate, plate, beam approach of stacking Technic bricks. But also, the cab is lowered by 1 plate thickness relative to the chassis. This results in an offset of 1 plate thickness in height than what is the norm, and also a kinda weird but totally legal construction of the chassis. This must have taken the designer a while to figure out and it's quite hard to get your head round but it seems the only reason they did that was to get the proportions of the big beefy looking truck just right.

Secondly, there is the use of grey pin connectors and axles to connect the top and bottom of the A pillars. The use of a grey (non friction) connector peg here is quite telling as it has some slop in it, meaning it will allow for a little bit of misalignment. This is really the only reason I can think of for using that part as opposed to the black friction connector peg.

Thirdly, there is also the fact that the roof isn't fixed to the horizontal, 90 degrees to the rear upright supports, which means the top mounting point of the A pillars can be moved up or down slightly to fit the A pillars. Yes, there is an axle going through the roof for the hoG steering, however there is some slop in the axle through the black 2x8 plate with holes which will allow for a small angular discrepancy without causing damage to pieces, or making it too difficult to assemble or disassemble, making it legal.

There are also two trumpets that are fixed to the slope and horizontal parts of the entire roof simultaneously!

Edited May 26, 2019 by Yevhen

[howitzer]

5 hours ago, Yevhen said:

There are also two trumpets that are fixed to the slope and horizontal parts of the entire roof simultaneously!

I have the model built, right here in front of me. The trumpets are fixed on level with the roof, and the roof has no angles, it's assembled on top of two 8 stud bricks. The trumpets are attached to the same 4 long liftarm (BL item no. 2825) as the exhaust stacks. The liftarms connect to the roof between 4 studs (same as the axle and pin connectors at the front end of the horn), and there's no other connection, so if the roof was sloped more than insignificant amount, the liftarms couldn't be attached on it as the placement between studs wouldn't stick. Behind the exhaust stacks is the battery box, which isn't connected to the roof at all.

[Yevhen]

54 minutes ago, howitzer said:

I have the model built, right here in front of me. The trumpets are fixed on level with the roof, and the roof has no angles, it's assembled on top of two 8 stud bricks. The trumpets are attached to the same 4 long liftarm (BL item no. 2825) as the exhaust stacks. The liftarms connect to the roof between 4 studs (same as the axle and pin connectors at the front end of the horn), and there's no other connection, so if the roof was sloped more than insignificant amount, the liftarms couldn't be attached on it as the placement between studs wouldn't stick. Behind the exhaust stacks is the battery box, which isn't connected to the roof at all.

Build the triangle by yourself and you'll see there is no 90° between the legs of the right-angled triangle!

[pleegwat]

The A pillar is 6 studs long between the pivots. The horizontal component would be 2 studs if the other angles were straight. That means the vertical component should be sqrt(6*6-2*2)=5.6568, which obviously won't match up.

Vertically the distance is 10 studs minus 11 plates. A plate is 0.4 stud (since 5 plates makes 2 studs), so that makes 5.6 studs, or an error of about 1/20 of a stud vertically. And if I look closely it does indeed look like the roof angles very slightly upward.

[allanp]

For sure the angle is barely noticeable. Small enough that the looseness of the non friction pins used to connect the A pillars, and also the looseness of the axle that goes through the 2x8 plate with holes in the roof is enough to avoid stressing any elements, so I would say it's perfectly legal.