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+--- Thread: Turntable 2855 accuracy (/thread-13410.html)
Turntable 2855 accuracy - Stephen - 2014-07-09
Is the 2855 "Technic Turntable Type 1 Top" known to be inaccurate at all?
I originally abandoned my attempt to position a gear to drive this turntable because it looked like what I was attempting was illegal, but now I think my desired position is fine and it's just an inaccurately defined 2855 part.
The enclosed MLCad screenshot shows the simplest example of the problem. All parts are correctly stud-aligned. But I've raised the red gears to highlight the problem. As you can see, the red gears actually cut into the body of the yellow turntable. I've included close-ups of how much the overlap occurs. I also added the grey gears just to show that no such problem exists between the grey and red gears. The problem is only with the turntable.
Can I safely assume that 8 and 24 tooth gears *can* be positioned as shown?
Re: Turntable 2855 accuracy - Philippe Hurbain - 2014-07-10
Yes it works in physical world -> turntable model is slightly off!
Rule of thumb: if the sum of tooth count of both gears you want to mesh is a multiple of 16, gears will mesh when placed on grid.
Here: (56+24)/16=5 studs, and (56+8)/16=4 studs, it's OK...
Re: Turntable 2855 accuracy - Stephen - 2014-07-10
Yes, I figured it would probably work. Certainly makes life a lot easier! I'm just rather used to (over)relying on MLCad zooms to test for part clashes on oddly positioned parts, because it's usually pretty accurate for most parts.
In the (probably) unlikely event that anyone feels like fixing this ;-) here is an image of the part. I don't have a real part, but it appears that the corner of the upright section should pretty much meet the edge of the main body of the turntable. As you can see from the MLCad insert, there's an erroneous gap. If both the inner and outer tooth radius (of the exterior teeth) were fixed to remove this gap, the part would probably work correctly.
Re: Turntable 2855 accuracy - Travis Cobbs - 2014-07-10
Actually, it may be that the circle actually cuts into the corner of the uprights, because parts in the real world have a small amount of rounding on their edges. I can't tell by the picture if the idealized corner of the uprights meets the circle, or if the rounded corner meets the circle.