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Regular Polygons with Technic  How many can You build?
technicmath replied to DrJB's topic in LEGO Technic, Mindstorms, Model Team and Scale Modeling
In https://webspace.science.uu.nl/~hooft101/lectures/meccano.pdf by Gerard ’t Hooft the following is stated: "For a multigon of n edges, 10n27 strips are required, using this method. With a bit more sophistication, I found heptagons made out of 35 pieces, 27 pieces, and any ngon out of 7n20 integral strips (assuming n to be odd; if n is even, a slightly different algorithm is needed). A bit of serendipity led to a heptagon of only 15 pieces (see Fig. 9)." "Figure 8: The rigid regular heptagon, using the method of equalizing angles as explained in Section 5. It is built out of 43 integral strips. This algorithm can be extended to any muligon." 
[TIP] A perfect fit
technicmath replied to Didumos69's topic in LEGO Technic, Mindstorms, Model Team and Scale Modeling
Thank you! First, the mathematical formula for such a configuration was derived. Then a java program was written to find solutions where all lengths are natural numbers. These solutions were given to a drawing program. 
[TIP] A perfect fit
technicmath replied to Didumos69's topic in LEGO Technic, Mindstorms, Model Team and Scale Modeling
Below are some more examples of a perfect fit: More examples of such configurations can be found at https://bricksafe.com/pages/technicmath/liftarm_geometry_triangle. 
New Elementary contest Make a Wishbrick
technicmath replied to technicmath's topic in LEGO Technic, Mindstorms, Model Team and Scale Modeling
Thank you @gyenesvi, @howitzer and @astyanax! Those parts would indeed be very useful! 
New Elementary contest Make a Wishbrick
technicmath posted a topic in LEGO Technic, Mindstorms, Model Team and Scale Modeling
Below are my designs for the contest "Make a Wishbrick" from New Elementary from JulyAugust 2022. The first design is a Plate, Modified 1 x 2 with Pin Holes on Bottom. Its design is a hybrid of the following parts: The second design is a Technic, Liftarm, Modified Perpendicular Holes Bent Thick LShape 5 x 7. The enlarged build consists of 3 units. The first unit is only used once in the corner. The second unit is only used twice at the ends. The third unit is used for all other enlarged pinholes. This third unit is positioned in different orientations in order to obtain the perpendicular pinholes. Each of these 3 units is a separate and solid build on its own. These 3 units can be joined together with technic pins. Hence also other configurations of liftarms can be build such as other nonexisting parts: Technic, Liftarm, Modified Perpendicular Holes Bent Thick LShape 3 x 5 Technic, Liftarm, Modified Perpendicular Holes Bent Thick LShape 5 x 5 existing parts: 39794 Technic, Liftarm, Modified Frame Thick 7 x 11 Open Center 71710 Technic, Liftarm, Modified Perpendicular Holes Thick 1 x 15 Each of the 3 units has a dimension of 8 x 8 x 8 studs. These 3 units mainly use the following parts: 35044 Plate, Modified 4 x 4 with 3 x 3 Curved Cutout 80015 Plate, Round Corner 5 x 5 with 4 x 4 Curved Cutout 27507 Tile, Round Corner 4 x 4 Macaroni Wide The enlarged build is built in the same scale as the Plate, Modified 1 x 2 with Pin Holes on Bottom above. The total number of parts in the enlarged build of the Technic, Liftarm, Modified Perpendicular Holes Bent Thick LShape 5 x 7 is 986. Congratulations to the winners! 
Technic Tessellations
technicmath replied to DrJB's topic in LEGO Technic, Mindstorms, Model Team and Scale Modeling
As previously mentioned by Erik Leppen, the length of some parts is mathematically too long: Below I made another version of this. In fact, this is an example of the Cairo pentagonal tiling: see https://en.wikipedia.org/wiki/Cairo_pentagonal_tiling. Four sides of the pentagon have length 1 and one side of the pentagon has length sqrt(3)1=0.732... In the example above this is scaled by 4 thus one side of the pentagon has length 4(sqrt(3)1)=2.928... but the parts used give a length of 3. Below I scaled by 7. Then one side of the pentagon has length 7(sqrt(3)1)=5.124... thus parts giving a length of 5 will not bend the structure but some space needs to be given. Here are 2 examples: The .ldr file can be found at https://bricksafe.com/files/technicmath/cairopentagonaltiling/Cairo pentagonal tiling.ldr I also made a Penrose tiling: see https://en.wikipedia.org/wiki/Penrose_tiling There are 2 tiles, see below: These use a rectangular triangle with side 2 and hypotenuse 7 thus the third side is 3*sqrt(5) by the Pythagoras theorem. Thus for example in the last tile, the length between the lowest and upper point is 6*sqrt(5)+6 which is 12 times the golden ratio and the length of the red sides is 12. Below is an svg picture: The .ldr file can be found at https://bricksafe.com/files/technicmath/penrosetilings/Penrose tilings.ldr 
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General Part Discussion
technicmath replied to PoloFreak's topic in LEGO Technic, Mindstorms, Model Team and Scale Modeling
There is a strange difference for the part Technic, Liftarm, Modified LShape Quarter Ellipse Thick 2 x 5 (80286). The shape between the 2 last pin holes is different: see the images below. The image on BrickLink is this: This is the same as the image on Bricks and Pieces which is this: But the image from ldraw is this: This is the same as the image from the review of 42137 from @Jim which is this: Is the shape from the images on BrickLink and Bricks and Pieces a preproduction shape? 4008 replies

 Bionicle Technic
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[WIP] Aston Martin Valkyrie
technicmath replied to Jeroen Ottens's topic in LEGO Technic, Mindstorms, Model Team and Scale Modeling
Another possible solution for the rear lights is this: The .ldr file can be found in the same folder: https://bricksafe.com/files/technicmath/astonmartinvalkyrierearlights/Rear lights_B.ldr 
[WIP] Aston Martin Valkyrie
technicmath replied to Jeroen Ottens's topic in LEGO Technic, Mindstorms, Model Team and Scale Modeling
@Jeroen Ottens A possible solution for the rear lights is this: The .ldr file can be found in the same folder: https://bricksafe.com/files/technicmath/astonmartinvalkyrierearlights/Rear lights.ldr 
[VIDEO REVIEW] 42131 CAT D11T Bulldozer + Control+ profile test
technicmath replied to kbalage's topic in LEGO Technic, Mindstorms, Model Team and Scale Modeling
Thank you @kbalage for this review! At 4:32, you mention "It is not highlighted in the manual but make sure to pay attention to the position of these gears: if you add one of them the other way around, the linear actuators will work in the opposite direction.". I think that the actuators will turn in the same direction, independent of the positioning of the 20 tooth idler gears. However, at that place in this set, the same mistake is made as in set 42082, which is demonstrated in this video from @Jim: This mistake was already made in set 8043 from 2010! See this post from @Blakbird 
42131  CAT D11 Bulldozer
technicmath replied to Maaboo35's topic in LEGO Technic, Mindstorms, Model Team and Scale Modeling
Is this a new liftarm with alternating pin holes? This part is new in yellow: 
Future Set Wishes and Speculation
technicmath replied to SheepEater's topic in LEGO Technic, Mindstorms, Model Team and Scale Modeling
I made a realistic gearbox here: This gearbox has 4 gears, has a realistic setup, can handle very high torque, fits in the studless grid construction and runs with very low friction. It would be even better if Lego made a 24 tooth clutch gear, which is in my opinion actually more useful than the 20 tooth clutch gear. 
Front live axle with kingpin inclination, diff lock, portal axles, constant velocity joints, Ackermann steering
technicmath replied to technicmath's topic in LEGO Technic, Mindstorms, Model Team and Scale Modeling
Thank you! Yes, indeed, the bar at the front controls the steering, there is indeed no rack and pinion. The steering arm has two of this part at the ends:. This steering arm is moved by moving the black arm with the 1 x 9 liftarm on top. This black arm moves together with the suspension and is controlled directly from the chassis of the vehicle. Thank you! The .ldr file contains building steps. At some points, the order of these building steps needs to be followed precisely because some parts can only be placed before other parts. Also, in some building steps, multiple parts are inserted in the same step. In this case, it is sometimes necessary to build some of these parts together before mounting it to the main build. I also made a corresponding rear axle with a diff lock, portal axles and the same width as the front axle: The following picture shows the very high ground clearance: A .ldr file can be found on bricksafe. This .ldr file includes building steps. The links: Front axle: https://bricksafe.com/files/technicmath/frontliveaxlewithkingpininclinationdifflockportalaxlesconstantvelocityjointsackermannsteering/axle.ldr Rear axle: https://bricksafe.com/files/technicmath/frontliveaxlewithkingpininclinationdifflockportalaxlesconstantvelocityjointsackermannsteering/axle_rear.ldr 9 replies

 live axle
 kingpin inclination

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Front live axle with kingpin inclination, diff lock, portal axles, constant velocity joints, Ackermann steering
technicmath replied to technicmath's topic in LEGO Technic, Mindstorms, Model Team and Scale Modeling
Thank you! Yes, I have built it in real bricks (except for some parts such as the differential which I don't own) and the construction is very strong. Simplified in which way? For example, the design can be enormously simplified by omitting the kingpin inclination and diff lock and then also the part count will be much lower. But these are the main features of the design. 9 replies

 live axle
 kingpin inclination

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This is a front live axle with kingpin inclination with angle atan(1/4)=14.036... degrees diff lock portal axles with 8/24 gear reduction constant velocity joints Ackermann steering The following picture shows the very high ground clearance and highlighted kingpin axis (in red): A .ldr file can be found on bricksafe. This .ldr file includes building steps. There are 2 black steering links on top and 2 grey links at the bottom. These create a 4bar linkage. A caster angle can be obtained by angling the whole axle by setting up the 4bar linkage properly.
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 live axle
 kingpin inclination

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