Compact wormgear gearbox?

[Mechbuilds]

Anyone know a compact gearbox that uses XL motor to have 2 imputs: 
Worm gear drive for crawling and regular 1:1 with no wormgear for drive? 

That way you'd have fast moving gear for driving around and then use worm gear for crawling. 

Why? 
Because worm gear is pretty much instant brakes once you let off the throttle. 

[Mechbuilds]

Oh.. I guess it's never been done before. 

[RocketPuppy]

Lego worm gear doesn't handle torque well at all. It's been tried, but it is one of the worst Lego gears at handling torque. 

 

You get better results with standard gear reduction. 

 

The idea makes sense mechanically, but doesn't transfer into lego well. The Lego worm gear is made of softer plastic and has some pretty loose tolerances. 

 

[BusterHaus]

You will need to unlock the output of the worm gear to make it work, hence the second gear selector.

• Red = input
• Green = output
• Gear selectors need to be synchronized, but work in opposite directions

Here's the LDR file if you're interested. Bracing not included.

Spoiler

 

0 FILE main.ldr
0 Name: Worm Gearbox
0 Author: BusterHaus
1 4 -20 0 0 1 0 0 0 1 0 0 0 1 3705.dat
1 69 -30 80 0 0 1 0 0 0 -1 -1 0 0 32526.dat
1 1 -10 0 0 0 0 -1 0.707 0.707 0 0.707 -0.707 0 35185.dat
1 0 70 40 0 0 0 1 0 1 0 -1 0 0 32270.dat
1 4 30 0 0 0 0 1 -1 0 0 0 -1 0 26287.dat
1 2 80 40 0 1 0 0 0 1 0 0 0 1 50451.dat
1 4 100 0 0 1 0 0 0 1 0 0 0 1 3706.dat
1 1 70 0 0 0 0 -1 -0.707 0.707 0 0.707 0.707 0 35185.dat
1 69 90 20 0 0 -1 0 0 0 1 -1 0 0 32523.dat
1 72 20 0 0 0 0 -1 -1 0 0 0 1 0 18947.dat
1 4 -90 40 0 0 0 1 -1 0 0 0 -1 0 26287.dat
1 1 -50 40 0 0 0 -1 0 1 0 1 0 0 35185.dat
1 2 -160 40 0 1 0 0 0 1 0 0 0 1 3706.dat
1 72 -80 40 0 0 0 -1 -1 0 0 0 1 0 18947.dat
1 72 -30 20 -80 -1 0 0 0 1 0 0 0 -1 Reducer 24z.ldr
1 19 -70 40 -27 0 -1 0 1 0 0 0 0 1 6589.dat
1 71 -10 0 -40 -1 0 0 0 1 0 0 0 -1 4519.dat
1 0 -10 0 -40 0 0 1 0 1 0 -1 0 0 32270.dat
1 19 -10 0 -80 0 0 -1 -0.707 0.707 0 0.707 0.707 0 32269.dat
1 71 -70 40 -70 0 0 1 0 -1 0 1 0 0 32073.dat
1 69 10 0 -60 0 1 0 -1 0 0 0 0 1 32523.dat
0 FILE Reducer 24z.ldr
1 25 0 0 0 0 0 1 0 -1 0 1 0 0 6536.dat
1 71 40 -20 0 0 0 -1 -0.866 -0.5 0 -0.5 0.866 0 4716.dat
1 72 40 20 5 -1 0 0 0 1 0 0 0 -1 3648b.dat
1 14 15 -20 0 0 0 -1 0 -1 0 -1 0 0 32123a.dat
1 14 65 -20 0 0 0 -1 0 -1 0 -1 0 0 32123a.dat
1 25 80 0 0 0 0 1 0 -1 0 1 0 0 6536.dat
1 4 0 0 0 0 0 1 0 1 0 -1 0 0 32062.dat
1 4 80 0 0 0 0 1 0 1 0 -1 0 0 32062.dat
1 71 40 0 15 1 0 0 0 0 1 0 -1 0 99773.dat
1 71 40 0 -15 1 0 0 0 0 1 0 -1 0 99773.dat
1 0 30 -20 0 -1 0 0 0 1 0 0 0 -1 3707.dat

 

 

 

 

[Didumos69]

1 hour ago, RocketPuppy said:

Lego worm gear doesn't handle torque well at all. It's been tried, but it is one of the worst Lego gears at handling torque. 

 

You get better results with standard gear reduction. 

 

The idea makes sense mechanically, but doesn't transfer into lego well. The Lego worm gear is made of softer plastic and has some pretty loose tolerances. 

 

You're quite right. The issue with high torque and LEGO worm gears is that you will have to lock the worm gear to avoid it from getting displaced. The worm gear will push itself against the locking parts with practically the same force as the force the worm gear applies to the gear it meshes with. This will cause a lot of friction between the worm gear and (one of) its locking parts.

The worm gear also slides along the teeth of the gear it meshes with. Under high torque, this sliding will cause friction too.

Edited August 22, 2020 by Didumos69

[RocketPuppy]

4 hours ago, Didumos69 said:

You're quite right. The issue with high torque and LEGO worm gears is that you will have to lock the worm gear to avoid it from getting displaced. The worm gear will push itself against the locking parts with practically the same force as the force the worm gear applies to the gear it meshes with. This will cause a lot of friction between the worm gear and (one of) its locking parts.

The worm gear also slides along the teeth of the gear it meshes with. Under high torque, this sliding will cause friction too.

Yeah, I broke a few beams, axles, and worm gears this way experimenting a few years ago.  The worm gears want to travel, you lose a lot of energy through friction locking them in place. Longer axles can warp under the friction. 

It doesn't take much power before you realize worm gears aren't ideal when used with motors. 

With the newly produced gears being softer overall I wonder if the chances for backlash are higher, possibly causing damage to the gears driving the worm gear. 

[Mechbuilds]

21 hours ago, BusterHaus said:

You will need to unlock the output of the worm gear to make it work, hence the second gear selector.

• Red = input
• Green = output
• Gear selectors need to be synchronized, but work in opposite directions

Here's the LDR file if you're interested. Bracing not included.

  Reveal hidden contents

 

0 FILE main.ldr
0 Name: Worm Gearbox
0 Author: BusterHaus
1 4 -20 0 0 1 0 0 0 1 0 0 0 1 3705.dat
1 69 -30 80 0 0 1 0 0 0 -1 -1 0 0 32526.dat
1 1 -10 0 0 0 0 -1 0.707 0.707 0 0.707 -0.707 0 35185.dat
1 0 70 40 0 0 0 1 0 1 0 -1 0 0 32270.dat
1 4 30 0 0 0 0 1 -1 0 0 0 -1 0 26287.dat
1 2 80 40 0 1 0 0 0 1 0 0 0 1 50451.dat
1 4 100 0 0 1 0 0 0 1 0 0 0 1 3706.dat
1 1 70 0 0 0 0 -1 -0.707 0.707 0 0.707 0.707 0 35185.dat
1 69 90 20 0 0 -1 0 0 0 1 -1 0 0 32523.dat
1 72 20 0 0 0 0 -1 -1 0 0 0 1 0 18947.dat
1 4 -90 40 0 0 0 1 -1 0 0 0 -1 0 26287.dat
1 1 -50 40 0 0 0 -1 0 1 0 1 0 0 35185.dat
1 2 -160 40 0 1 0 0 0 1 0 0 0 1 3706.dat
1 72 -80 40 0 0 0 -1 -1 0 0 0 1 0 18947.dat
1 72 -30 20 -80 -1 0 0 0 1 0 0 0 -1 Reducer 24z.ldr
1 19 -70 40 -27 0 -1 0 1 0 0 0 0 1 6589.dat
1 71 -10 0 -40 -1 0 0 0 1 0 0 0 -1 4519.dat
1 0 -10 0 -40 0 0 1 0 1 0 -1 0 0 32270.dat
1 19 -10 0 -80 0 0 -1 -0.707 0.707 0 0.707 0.707 0 32269.dat
1 71 -70 40 -70 0 0 1 0 -1 0 1 0 0 32073.dat
1 69 10 0 -60 0 1 0 -1 0 0 0 0 1 32523.dat
0 FILE Reducer 24z.ldr
1 25 0 0 0 0 0 1 0 -1 0 1 0 0 6536.dat
1 71 40 -20 0 0 0 -1 -0.866 -0.5 0 -0.5 0.866 0 4716.dat
1 72 40 20 5 -1 0 0 0 1 0 0 0 -1 3648b.dat
1 14 15 -20 0 0 0 -1 0 -1 0 -1 0 0 32123a.dat
1 14 65 -20 0 0 0 -1 0 -1 0 -1 0 0 32123a.dat
1 25 80 0 0 0 0 1 0 -1 0 1 0 0 6536.dat
1 4 0 0 0 0 0 1 0 1 0 -1 0 0 32062.dat
1 4 80 0 0 0 0 1 0 1 0 -1 0 0 32062.dat
1 71 40 0 15 1 0 0 0 0 1 0 -1 0 99773.dat
1 71 40 0 -15 1 0 0 0 0 1 0 -1 0 99773.dat
1 0 30 -20 0 -1 0 0 0 1 0 0 0 -1 3707.dat

 

 

 

 

Interesting solution! You can also have a fake engine spin while it's on neutral. 

[BusterHaus]

By the way @RocketPuppy and @Didumos69 brought up a very good point - this is a very inefficient way to transfer power.  I would suggest using a very high reduction instead of a worm gear, it should help stop the car in place without power.

[Mechbuilds]

Yeah i think the force of the gear meshing with the wormgear trying to push it will stall the motor. Good idea in paper but bad in practise.