Creating a 2 to 1 Gear Ratio

[TechnicBrickPower]

Hi Everyone,

Just made a video about a problem I had to solve: Trying to create a 2 to 1 gear ratio for a MOC project I was working on. These are just some of my solutions - I'd be interested in hearing about other people's solutions to this problem. I found one elegant solution that I show near the end of the video that surprised me to discover. Obviously I won't be the first to find this - but it's nice to re-invent things by yourself!

Let me know what you think.

My next project is to create a 7 to 1 gear ratio LOL.

Comments invited!

 

Rob

New Zealand.

 

 

 

[Ngoc Nguyen]

This is the standard 2:1 gear mesh setup.

[Captainowie]

2 hours ago, TechnicBrickPower said:

My next project is to create a 7 to 1 gear ratio LOL.

The old Technic Turntable Top (http://www.peeron.com/inv/parts/2855) has 56 teeth, and meshes nicely with an 8-tooth gear for a 1-7 ratio.

If that's too big, there are other gears with multiples of 7 teeth, including most of the various differentials, the old (and thin and frail) 14-tooth gears, and the newer small turntable.

Edited January 23, 2020 by Captainowie

[Philo]

41 minutes ago, Captainowie said:

If that's too big, there are other gears with multiples of 7 teeth, including most of the various differentials, the old (and thin and frail) 14-tooth gears, and the newer small turntable.

This year, a regular 28t gear was also introduced: https://brickset.com/parts/design-46372
 

[doug72]

I would recommend getting these books.

 Power functions ideas machines & mechanisms, which has a two sections on various gear ratios for step up *& step down.
There is also another book by same author for  Cars & Contraptions. Both books are very usefull.

https://www.amazon.co.uk/LEGO-Power-Functions-Idea-Book/dp/1593276885

https://www.amazon.co.uk/LEGO-Power-Functions-Idea-Book/dp/1593276893

Edited January 23, 2020 by Doug72

[suffocation]

The 12/24 combo can be tricky. Assuming you're using a double-bevel z12 as the smaller of the two, the larger can be any of the following:

• a standard z24 gear. They seem to produce quite a bit of friction unless you use the latest ones (maybe from 2016 onward? Not sure), which have ever-so-slightly shorter teeth.
• a white clutch gear. No issues encountered so far.
• an old crown gear. Can't figure out a pattern here - some offer a fairly smooth mesh while others hardly move, regardless of whether they're standard or reinforced.
• a second-gen differential. The ones I've tried, whether DBG or red, all seem to mesh fine.

 

Edited January 25, 2020 by suffocation

[TechnicBrickPower]

On 1/23/2020 at 7:49 PM, Captainowie said:

The old Technic Turntable Top (http://www.peeron.com/inv/parts/2855) has 56 teeth, and meshes nicely with an 8-tooth gear for a 1-7 ratio.

If that's too big, there are other gears with multiples of 7 teeth, including most of the various differentials, the old (and thin and frail) 14-tooth gears, and the newer small turntable.

 

On 1/23/2020 at 8:44 PM, Philo said:

This year, a regular 28t gear was also introduced: https://brickset.com/parts/design-46372
 

Hi Guys thanks that's good to know. I never knew there were any 7 multiple gears out there. Interesting that one has recently been introduced. Will put in a bricklink order now and get some. Will still try to create a 7 to 1 without using one of those. Otherwise I will try an 11 to 1.

 

[doug72]

Compact 7 to 1 gear ratio

Can be 1:7 or 7:1 depending on input.

Using z28 turntable

Using new z28 double bevel gear

 

11:1 difficult, the example in the Machines & Mechanisms book by Yoshihito Isogawa uses an old diff (24t & 16T) and a Z28 turntable but is not compact.

Edited January 25, 2020 by Doug72

[pleegwat]

I expect since there are no gears with multiple of 11 teeth 11:1 can only be done using a differential. Same for all other further primes - they'll all need at least one differential.

[Tazmancrash]

Any one have a good 4:1 set up?

[doug72]

4 hours ago, Tazmancrash said:

Any one have a good 4:1 set up?

Try this.

4:1 or 1:4 gears using 2 x 8T & 2 x16T gears.

Also possible using a planatry gear system but takes up a lot of space.

Edited January 26, 2020 by Doug72

[TechnicBrickPower]

On 1/26/2020 at 5:36 PM, Tazmancrash said:

Any one have a good 4:1 set up?

 

Here's a good 1:4 or 4:1 I created (between black and brown axles). Strong and smooth. Can attach directly to a liftarm. Hope you find it useful.

[doug72]

1:4 gear box using 12T double bevel gears and 24T spur gears mounted using LEGO V-engine Block Connector (28840 / 32333), which I used in a GBC Train module.

Edited January 27, 2020 by Doug72

[Jurss]

Both last 1:4 as concepts are good, but as they are, definately needs to be braced

[doug72]

50 minutes ago, Jurss said:

Both last 1:4 as concepts are good, but as they are, definately needs to be braced

The last one is braced by the baseplate but easy to add 8L axle with bushes to hold all in place and keep correct spacings between the V blocks, It is able to carry high loading on my GBC Train module.

[Jurss]

Not Yours, You were posting at the same time

[Thierry-GearsManiac]

A 1:4 ratio can also be done the planetary way, using either Z8 pinions and the Z24 inner gear from big turntables v.1 and 2, or Z16 wheels and the Z48 inner gear on the 64712 part (see https://www.bricklink.com/v2/catalog/catalogitem.page?P=64712#T=S&O={"iconly":0}), as shown on Yoshihito Isogawa's Power Functions Ideas book, idea #194.

When the planetary mechanism is built with an inner gear as the stationery one, the sun gear / planet carrier ratio equals the (sun gear / ring gear) ratio plus 1.

However, if the stationery gear is an outer one, then the sun gear / planet carrier ratio equals the (sun gear / ring gear) ratio minus 1.

For example, sun gear = Z24 ; planet = combo Z24/Z8 ; stationery gear = Z40 (but in this case, the planet carrier will be hard to interface with)

 

At last, some other possible 2:1 gear ratio solutions :

• Z20 to Z40 (http://www.planet-gbc.com/modulegbc-torso-cardanlift/)
• Z28 to Z56 (big turntable v.1 or 2)
• hidden in a longer gear train, by inserting an intermediate 2:1 combo gear (i.e. two gears on the same axle with LEGO) between two of the gears (see attached example, where the intermediate combo gear is the axle supporting the contrate Z24 and the single-beveled Z12, and the ends of the gear train are the two Z20 gears --the blue one rotates freely on the axle : https://www.bricklink.com/v2/catalog/catalogitem.page?P=35185)

 

Edited February 2, 2020 by Thierry-GearsManiac
replacing attachment with a link

[Thierry-GearsManiac]

A last thing about 2:1 gear ratios : have people already used the perpendicular solution between a Z24 contrate gear and a Z12 ?

One can see it my the above mechanism, if we only consider the meshing between the Z24 contrate gear and the Z12 idler gear.

Or in the sketches below, where several rigid stop solutions can be used to counter the axial force applied to the contrate gear :

• a pin with towball (black)
• two plates (red)
• an old Id=424 spacer (yellow), as discovered  here :

Edited February 2, 2020 by Thierry-GearsManiac
incomplete message

[pleegwat]

I just checked - crown gear to z12 can be done in a 5x7 frame if you space the crown gear with an old z14 bevel gear since those are a quarter stud thick. The z12 then needs a simple half-stud of padding. This runs very smooth for me in an unloaded test.

[Thierry-GearsManiac]

Clever idea for using the 5x7 frame : I didn't know any mean to create a 0.25L thickness before.

On my side, I've also tried to use the height of a stud (Id=4274 : stud-terminated half pin), which is 0.2L, for holding the crown gear (I used the general rule for gear meshing : +-0.05L tolerance around the desired nominal distance).

However, in this case, the meshing was so loose that it could easily skip teeth. Then, when mounting a tile (0.4L thickness) on the stud (or using a round 2x2 tile as a washer), the meshing became very tight, relying on the backlash of the axle of the Z12 gear in the frame's hole.

And, after trying your solution, I also discovered that the thickness of the old Z14T gears is in fact 0.375L = (3/8)L, i.e. 1/8th more than expected (if you stack four of them, then you'll obtain almost 1.5L), so that the interval between the nominal and the real distance is now 0.125L with a Z14T gear, and 0.15L with a tile = significantly beyond the +-0.05L tolerance.

Therefore we can conclude that the rule for proper gear meshing does remain valid only for spur gear meshing, and not for perpendicular meshing involving a crown gear.

 

 

[pleegwat]

I checked and see you are indeed right - 4 Z14s is significantly  more than a stud, though I don't think it's as much as 1.5. I don't know why I thought otherwise.

I still think you need a quarter stud in that configuration ideally, since that matches the known good meshes with z24 or z8 straight gears.