LEGO vs Tyco - double-sided plate comparison
I have received some Tyco parts so now I can compare the LEGO prototype with the Tyco double-sided plate.
In this image the blue parts on the left are LEGO. The black and grey parts are Tyco. The grey plate has hollow studs on the opposite side (this prevents moulding problems).
The top right assembly is made with LEGO parts. LEGO plates are 1/3 brick height. The green brick and the red, white and blue plates show this height ratio. LEGO is very, very careful to maintain system compatibility between all its parts, and they have implemented that in the design of their double sided plates. The female-female plate (anti-studs) is two plates high and the male-male plate (studs) is one plate high. Together they are exactly one brick high. Because of these strict design rules there is no height difference when you use a double-sided plate and start building in an opposite direction. The yellow and black plates in this photo are on exactly the same height and align perfectly.
The bottom right assembly is made with Tyco parts. Tyco plates are 1/2 brick height. The black brick and the yellow and blue plates show this height ratio. Tyco is not so strict in maintaining the exact part compatibility. (I suspect that production is the first design priority and size compatibility comes second, while LEGO usually rejects any design that is not fully compatible.) The female-female plate (black) is exactly one plate high, but the male-male plate (grey) is much thinner. As a result there is a height difference when you use one of these plates to start building in the opposite direction. The two yellow plates at the bottom do not align.
The yellow turntable assembly has a similar problem. The bottom part is exactly one plate high, but the top part is thinner. The thinner male-male plate and turntable-top-plate have different heights, there does not seem to be a standard system. On the hinge assembly both parts are one plate thick.
These mixed sizes severely limit how you can build with them, because many combinations will lead to gaps, improper connections or other alignment problems.
It would have been possible to design both the male-male and female-female plate to be one plate high, the studs are less than 1/2 plate in height and they would not have caused an interference problem. I suspect they have chosen to use a thinner plate to make the design more suitable for injection moulding.
The LEGO solutions to the Tyco design problems
LEGO made some prototype plates with a constant thickness and some plates which are thinner in the center. We do not know which version was made first, but it seems reasonable to assume that the constant thickness plate was made first. I do not know what was wrong with that design, but maybe the constant-thickness-plates had too many moulding problems. They are relatively thick and the studs cause a large increase in local part thickness. I suspect the thinner-center-plates did not comply to LEGO's quality standards. If you attach a 1x1 brick to one of the studs, it will not be properly supported on all sides. On the outside it will be limited by the rim on the plate, but in the center it will be "floating" so the 1x1 brick can be pushed into the plate too far. As a result there will be additional stresses on the plate which could lead to permanent damage. This must have been unacceptable for LEGO. If LEGO ever releases a part like this, it will need to have a constant thickness (and that design was probably also rejected for a good reason).
This issue is a bit similar to the problem that caused the redesign on the 1x1 cone bricks. Initially the cones had a smooth slope (BrickLink 4589), but those parts could be pushed into other parts too deep causing damage, they were redesigned with a groove that prevents this problem (BrickLink 4589b). Possible alignment problems lead to a redesign or rejection of the part.
LEGO vs Tyco - double-sided plate comparison
I have received some Tyco parts so now I can compare the LEGO prototype with the Tyco double-sided plate.
In this image the blue parts on the left are LEGO. The black and grey parts are Tyco. The grey plate has hollow studs on the opposite side (this prevents moulding problems).
The top right assembly is made with LEGO parts. LEGO plates are 1/3 brick height. The green brick and the red, white and blue plates show this height ratio. LEGO is very, very careful to maintain system compatibility between all its parts, and they have implemented that in the design of their double sided plates. The female-female plate (anti-studs) is two plates high and the male-male plate (studs) is one plate high. Together they are exactly one brick high. Because of these strict design rules there is no height difference when you use a double-sided plate and start building in an opposite direction. The yellow and black plates in this photo are on exactly the same height and align perfectly.
The bottom right assembly is made with Tyco parts. Tyco plates are 1/2 brick height. The black brick and the yellow and blue plates show this height ratio. Tyco is not so strict in maintaining the exact part compatibility. (I suspect that production is the first design priority and size compatibility comes second, while LEGO usually rejects any design that is not fully compatible.) The female-female plate (black) is exactly one plate high, but the male-male plate (grey) is much thinner. As a result there is a height difference when you use one of these plates to start building in the opposite direction. The two yellow plates at the bottom do not align.
The yellow turntable assembly has a similar problem. The bottom part is exactly one plate high, but the top part is thinner. The thinner male-male plate and turntable-top-plate have different heights, there does not seem to be a standard system. On the hinge assembly both parts are one plate thick.
These mixed sizes severely limit how you can build with them, because many combinations will lead to gaps, improper connections or other alignment problems.
It would have been possible to design both the male-male and female-female plate to be one plate high, the studs are less than 1/2 plate in height and they would not have caused an interference problem. I suspect they have chosen to use a thinner plate to make the design more suitable for injection moulding.
The LEGO solutions to the Tyco design problems
LEGO made some prototype plates with a constant thickness and some plates which are thinner in the center. We do not know which version was made first, but it seems reasonable to assume that the constant thickness plate was made first. I do not know what was wrong with that design, but maybe the constant-thickness-plates had too many moulding problems. They are relatively thick and the studs cause a large increase in local part thickness. I suspect the thinner-center-plates did not comply to LEGO's quality standards. If you attach a 1x1 brick to one of the studs, it will not be properly supported on all sides. On the outside it will be limited by the rim on the plate, but in the center it will be "floating" so the 1x1 brick can be pushed into the plate too far. As a result there will be additional stresses on the plate which could lead to permanent damage. This must have been unacceptable for LEGO. If LEGO ever releases a part like this, it will need to have a constant thickness (and that design was probably also rejected for a good reason).
This issue is a bit similar to the problem that caused the redesign on the 1x1 cone bricks. Initially the cones had a smooth slope (BrickLink 4589), but those parts could be pushed into other parts too deep causing damage, they were redesigned with a groove that prevents this problem (BrickLink 4589b). Possible alignment problems lead to a redesign or rejection of the part.