SaperPL

Custom 2 studs wide differential frame

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Posted (edited)

I've got the idea to make a 2 studs wide differential from someone on our local Lego fans forum.

The challenge is that the gears inside the differential take up whole 2 studs of space already.

I think the only way it can be done is making a differential frame with open sides.

You can download the STL file for 3d print here: https://www.thingiverse.com/thing:4860328

I thought this deserved a separate topic as this might be game changing for some model team builds.

Edited by SaperPL

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Interesting concept, albeit if we're going to such a small width, I'd think that the diameter of the carrier-mounted gear is too big, since it is likely that the potential model using this would have 30.4 x 14 VR wheels. Probably something like this might be preferrable.

Nonetheless, never seen something similar in regards of open side walls, ingenious solution.

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9 minutes ago, syclone said:

Interesting concept, albeit if we're going to such a small width, I'd think that the diameter of the carrier-mounted gear is too big, since it is likely that the potential model using this would have 30.4 x 14 VR wheels. Probably something like this might be preferrable.

Nonetheless, never seen something similar in regards of open side walls, ingenious solution.

That's a fair point and I'm also always agonising about the fat that this diff is just so close to the 30.4 wheels. Check out my models with those wheels, the diff always has to go up because of that. But you can't do much about it if you want to use original lego gears inside unless you want to cheat a bit by having less contact with the corresponding gear just to shave off those 2 mm of diameter, but that's still not that much of a clearance.

I don't like the solution that uses custom made gears inside diff IF you are going to print that on FDM printer. Printing small gears for a diff looks like a risk of something cracking under load, so I prefer using those existing 12 tooth gears.

I'm thinking about designing with a different approach though - I want to make a two piece that will resemble the new grey and red differential frame - this will make it so that the gears will be held in place and I want it to be more lego like.

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Posted (edited)

IMHO your solution is better than one in shapeways. :thumbup:

Edited by I_Igor

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Indeed! Much easier to Install, but ist doesnt fit into a actuator holder.

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How about this?

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I don't have light grey filament to match the original diff colour though. It works the same as the original one - there's that bit of resistance/slowing the rotation when the one is new and it slowly gets faster.

Not an easy piece to print so I made custom supports. Need a bit of cleaning the strings inside. I'm still not sure whether this should be the final design or not - the latches aren't perfect and depending on the print they may get hard to detach.

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