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Questions tagged [gears]

Gears transmit rotary motion and are commonly found in Technic sets.

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18 votes
2 answers
3k views

Are Samsonite gears compatible with modern Technic gears?

Do the old Samsonite gears (above) work with current Technic gears (below) LEGO bricks tend to be backward compatible with older bricks, but since I don't own any Samsonite gears I cannot tell. ...
Ambo100's user avatar
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17 votes
1 answer
3k views

How can I make a precise one-way clutch using Technic elements?

I need a mechanism so that if a (NXT) motor rotates forward, it moves one gear, but the other stays still, but if it rotates backwards, the first gear does not move, but the second one does. I found ...
Ari Porad's user avatar
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16 votes
2 answers
2k views

How can I place a motor in the middle of a Technic beam with an odd number of holes?

Can you give me some advice how to make it so motor will be in the middle, but at the same time keep the functionality of the 2 axles on the sides? It can go further up if necessary.
Neikar's user avatar
  • 163
16 votes
4 answers
556 views

How can I fix a flattened gear?

I have an old small gear that somehow got flattened to an oval shape. The axle hole is too narrow to slide a bar through, although it is not completely closed shut. How can I repair this gear?
Pubby's user avatar
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14 votes
1 answer
1k views

Part identification: 40 tooth gear from The LEGO Movie

While watching clip of the LEGO Movie, I found a strange part: Slightly earlier in the video, its part number is shown as 3649. But it doesn't match the 40t gear I know nor the pictures on bricklink....
phi's user avatar
  • 143
14 votes
1 answer
1k views

What is the difference between these hole shapes?

I purchased an assorted bag of LEGO Technic pieces. There are pieces with axle holes, but what puzzles me is that the holes are different from what I am familiar with. There's a piece with an ...
Torben Gundtofte-Bruun's user avatar
13 votes
4 answers
2k views

2:1 gear ratio in stud-less Lego Technic

Is there a recognised technique to create a 2:1 gear ratio in stud-less Lego Technic? Neither of the two methods suggested here (studded though) work. 24T/12T with a 2L x 1L axle offset does rotate, ...
Peregrine's user avatar
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13 votes
1 answer
3k views

What's the purpose of the clutch gear in Power Functions set?

I have just bought this set and wonder the purpose of the white gear in the middle: How can you use it in your Lego Technic projects? Is it available in other sets?
Sergei Basharov's user avatar
12 votes
4 answers
10k views

How to make a conveyor belt with LEGO parts?

I am making a small robot with an Arduino and Technic LEGO powered by stepper motors. I am planning on moving small rocks throughout my machine. Does anyone have an idea of what kind of Technic LEGO ...
bogen's user avatar
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12 votes
1 answer
22k views

What are the dimensions of a technic axle?

I'm working on a LEGO compatible motor system that will be largely 3D printed. I want the connectors to fit standard LEGO axles, but I haven't been able to find the dimensions online, and I don't ...
BillThePlatypus's user avatar
11 votes
3 answers
4k views

What are the torque limits of gears?

I am using Lego in the classroom to introduce students to geared machines. As part of this I am asking them to design a winch, using a small 1.5V DC motor and a collection of the common Lego gears, i....
Li-aung Yip's user avatar
10 votes
4 answers
2k views

How can I assemble 2 opposing gears so that the axle rotations are perfectly parallel?

Due to the way all the modern LEGO gears are perfectly quarter-turn symmetrical, there doesn't appear to be any way to assembly 2 opposing gears such that I get a 2 perfectly parallel axles. This ...
Alexander O'Mara's user avatar
10 votes
1 answer
9k views

9398 4x4 Crawler front wheels rotate in the opposite direction to the rear wheel

We've just finished 9398 4x4 Crawler. Everything looks good, the motors work but the front wheels rotate in the opposite direction to the rear wheels, they also turn in opposite directions. What could ...
Belle's user avatar
  • 103
10 votes
1 answer
514 views

High Torque Subtractors

I would like to use a subtractor in my next RC LEGO tank, as it enables the vehicle to turn on the move, as opposed to stopping and then turning. Unfortunately, the subtractors I have tested so far ...
Nick Barham's user avatar
9 votes
3 answers
350 views

What's this round blue gear piece from set 76911?

This piece was in with all of set 76911's spare pieces in a separate bag. 76911 is the only Speed Champions set I have so I don't know if the piece comes in any others. I looked at the inventory for ...
Toomany Bees's user avatar
9 votes
1 answer
2k views

Pre-Technic gears?

I have this set of LEGO gears. I remember seeing them first at my grandparents in the mid 80's. They predate my first Technic sets (~84 or 85). I have fond memories of my dad building a 3-speed ...
Stephane Delcroix's user avatar
9 votes
1 answer
2k views

Strongest gear configuration

I'm building a (what I hope to be) high-speed car using two PF-XL motors together and some gearing up. However, there's a point where I have to rotate the axle with power (that comes from the 3 speed ...
Alex's user avatar
  • 191
8 votes
2 answers
16k views

How can I transmit horizontal torque to vertical?

I have a setup where I have a step motor which I am attaching a gear onto. The motor will make the gear stand horizontal in a small vehicle. Is there any good gear combinations of LEGO gears that can ...
bogen's user avatar
  • 825
8 votes
2 answers
2k views

Insert a gear into a turntable?

Is there a way to insert a 24 tooth gear into a turntable of the 48452cx1 type? --> Is there any model to feature any tooth gear (even smaller) used inside this turntable? This specific ...
mike's user avatar
  • 503
8 votes
1 answer
1k views

What is the purpose of the 8 tooth timing gear?

I recently ran across the 32060 Technic Gear Timing Wheel 8 Tooth element when sorting a mixed bag of parts. This element doesn't appear in many sets as a functional element. Here's one example from ...
jncraton's user avatar
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8 votes
1 answer
8k views

What is the "Module" of a LEGO gear?

Module, m this indicates the tooth size and is the number of mm of pitch circle diameter (p.c.d.) per tooth. For gears to mesh, their modules must be equal. Gear ISO standards and design methods ...
user2813274's user avatar
  • 1,156
8 votes
2 answers
1k views

Any way to create a gear+chain, like for a bike?

I would like to create a LEGO bike. I can imagine how most of it would work, but i'm stuck at the chain. I need a way for the turning pedals (at one spot) to cause the wheel (in the back) to spin ...
Scimonster's user avatar
8 votes
2 answers
4k views

How to build a limited slip differential?

Lego provides a couple of ways for building a differential, such as this: and also provides a limited-slip gear like this: http://www.brickowl.com/catalog/lego-technic-differential-with-one-gear-28-...
user2813274's user avatar
  • 1,156
8 votes
1 answer
3k views

Any tips for aligning gears in LDD?

I'm trying to create the 42052 (Heavy Lift Helicopter), and other Technic sets. Aligning gears' teeth is relatively difficult, and the 'Hinge Align' tool rarely works. Please help!
LenTheSpaceWolf's user avatar
7 votes
2 answers
2k views

How much torque can a lego axle handle?

from to this question, it seems that the gears are stronger than the axles, which begs the question of how strong are the axles? if you connect one of the stronger motors, such as say the buggy motor: ...
user2813274's user avatar
  • 1,156
7 votes
2 answers
532 views

Non-working technic system

Recently I've been working on a car which when going forward is fast, and when going backward automatically goes slowly. Here are two photos of it: (Just replace the text by "input") As you can see, ...
Kimatuy's user avatar
  • 203
7 votes
2 answers
243 views

9398 reduction change

I am studying implementation of 9398 crawler reduction. Here is the stripped part, in order to see the gears and their relation - the image is made with the excellent tool which is LDCad. My idea is ...
mike's user avatar
  • 503
6 votes
1 answer
3k views

Grand piano page 269 of instructions - are the gears suppose to stop after a quarter turn or keep going when reversing directions

The directions show the gears are suppose to move counter clockwise. When I follow the directions on page 268-269, and push the reverse button on the Lego power-up app for the Grand Piano, the gears ...
David Sparks's user avatar
6 votes
2 answers
536 views

How can I connect a 4mm Stepper motor shaft to a technic gear?

How can I connect a 4mm or 6mm stepper motor D shaft to an old Technic gear? I would like to mount an old 8-tooth gear to a 4-6 mm diameter stepper motor shaft. Lego part: 3647: Stepper motor: ...
Gary Kindel's user avatar
6 votes
1 answer
685 views

Which combination has a lower gear friction?

I need roughly a 1:3 reduction and I see a couple of ways to achieve it: using a 8t gear and a 24t gear (1:3) using 2x 12t gears and 2x 20t gears (1:2.779) using a 16t gear and a 40t gear (1:2.5) ...
user2813274's user avatar
  • 1,156
6 votes
2 answers
946 views

How much energy do LEGO Technic gears lose to friction?

So, I recently watched a video by the Brick Experiment Channel about building a 1 Googol:1 reduction gearbox, which at the time of writing this question, is at #44 on Youtube Trending. At the end of ...
nick012000's user avatar
6 votes
2 answers
840 views

Gearing down a PF XL

I'm looking for the best way to gear down a Power Function XL. I need to achieve a very slow output RPM (less than 1-2 RPM). I've tried a 625:1 gear (trough 40:8 gear). Can someone link to a well ...
Imlach's user avatar
  • 61
6 votes
2 answers
2k views

Error correction after building the D11

I just finished the D11 bulldozer. The last LEGO set I built was 55 years ago, now I got this big machine and I really enjoy it! But I have troubles with the the calibration and I think the failure is ...
Jeeplego's user avatar
  • 141
5 votes
2 answers
5k views

Lego Digital Designer: Having Gears Interact with Toothed Bar

I just started using LDD, and I have been trying out a few things that I couldn't do with the limitations of my Lego collection. One thing that has me caught up is that I can't seem to get the ...
Jedi_Maseter_Sam's user avatar
5 votes
2 answers
2k views

What is the difference between 8T gears "Type 1" (3647) and "Type 2" (10928)?

On Bricklink I can see that there are two types of 8-toothed gear - a "Type 1" (3647) and a "Type 2" (10928). It's obvious these parts are not the same, but what is the functional difference between ...
Li-aung Yip's user avatar
5 votes
1 answer
545 views

Does LEGO Digital Designer include part 4539880?

Does anyone know if LEGO Digital Designer includes the part 4539880 (often used for housing differentials) ?
Nick's user avatar
  • 51
5 votes
2 answers
6k views

How important is a center differential on a 4WD model?

I am looking to make a 4WD, single-engine powered vehicle, and I have seen others such as this which use three differentials to distribute the power to all 4 wheels: http://www.eurobricks.com/forum/...
user2813274's user avatar
  • 1,156
5 votes
2 answers
3k views

How to best transfer power at 90 degrees for high torque applications

So, I am building a tank model and this is the transmission I have been working on: Description: There are two gear pairs for gearing up (16t to 8t gears) and one gear pair for gearing down (worm ...
general molotof's user avatar
5 votes
0 answers
804 views

LEGO Bugatti Issues

This is my first post and my first LEGO set. I recently built LEGO Bugatti Chiron with all the features working. I am however having an issue with the rear axle/wheels. The rear brake calipers fall ...
Simba's user avatar
  • 51
4 votes
3 answers
492 views

Extra Pieces for Lego Gadgets Book

My son is having a lot of fun with the Lego Gadget set (book and bricks), but he can only build one thing at a time, and would love to have a lot more of the types of Lego bricks that came with the ...
Tiffany Fletcher's user avatar
4 votes
1 answer
2k views

I am building the LEGO 42131 D11 dozer and some of the parts are moving in reverse when testing

I am building the D11 dozer and some of the tests like 2 and 4 are moving the parts in the opposite direction that they are supposed to be going. I took apart the entire build and rebuilt it and the ...
Aidan's user avatar
  • 41
4 votes
2 answers
816 views

Can you use a beveled gear as a pinion?

I would like to use the PF servo motor for steering, however it is very large - I was playing with the idea of having it mounted vertically, and then using bevel gears to change the direction of the ...
user2813274's user avatar
  • 1,156
4 votes
1 answer
476 views

What does "No Friction" mean in Parts "Gear with 8 Teeth Wide, Notched and No Friction"

http://www.brickowl.com/catalog/lego-gear-with-8-teeth-wide-notched-and-no-friction-11955 As title, what does "No Friction" mean in the part "Gear with 8 Teeth Wide, Notched and No Friction" ?
Recca Chao's user avatar
4 votes
1 answer
527 views

Are DUPLO gears compatible with LEGO gears?

Can I make a transmission from DUPLO gear (Early Simple Machines Set 9656) to regular-sized gear?
yshilov's user avatar
  • 143
4 votes
1 answer
450 views

How would one parametrically create a LEGO-compatible gear?

If a gear was intended to smoothly mesh with standard LEGO gears, how should it be defined? While I know that the mean diameter (average of inner and outer diameters) of a LEGO gear should be 1mm/...
Mark's user avatar
  • 141
4 votes
1 answer
274 views

How to debug gears in the Bucket Wheel Excavator?

My 8 year old is just finishing the Bucket Wheel Excavator. He turned the motor on and there is a significant clicking noise. It looks as though the top gear noted in the picture gets stuck. Not sure ...
LittleBoyBuilder's user avatar
4 votes
1 answer
519 views

Any issues with this non-standard gear combination of 12t gears?

I don't see any "accepted" gear ratios for a stud-less direct-diagonal gear combination on sariel's excellent gear coupler but by shifting 12t gears such that they mesh off-center, it seems to work (...
user2813274's user avatar
  • 1,156
4 votes
1 answer
5k views

How can I controll the speed of motor using gears?

Can anyone tell me how to use gear wheels to modify the speed of the motor in the Power Functions set 8293? I know I could use the remote control unit, but I need to have a fixed slow speed on a ...
user3469's user avatar
3 votes
1 answer
126 views

Create a gimbal like structure with Technic gears

I would like to attach a sensor to a plate, and tilt that plate slightly in the XY direction respectively, without moving the plate itself. Similar to this (force feedback joystick concept) like this ...
user3607022's user avatar
3 votes
1 answer
538 views

Gearbox doesn’t move when it’s in neutral - Is that normal?

I’m not sure if the gearbox is supposed to move when it’s in neutral but the gearbox only moves when it’s in drive or rear. If I made an error can someone please tell me if there is a way to fix it?
nando gomez's user avatar