Gears-efficient gearbox

[technicmath]

The idea of @nicjasno in

for a gearbox can be improved as follows.

1. There is no need for a 24 or 28 gear with clutch: the setup can be built as (two axles)
   28-24-(20 with clutch)-clutch-(16 with clutch)
   (16 with clutch)-clutch-(20 with clutch)-24-28.
2. For these gear combinations, a distance of 44/16=2.75 studs is desired. By using the above configuration, there is a distance of sqrt(2^2+2^2) or approximately 2.828 studs. This can be improved by
   xx    -> 1 x 2 technic brick with 2 holes with axle at the left
   xxxx -> 1 x 4 technic brick with axle at the right.
   Then the distance is sqrt((3*2/5)^2+2.5^2) or approximately 2.773 studs, which is much closer to the desired 2.75 studs and then the gears run much smoother.

[nicjasno]

Essentially making it even more compact than i planned. That is brilliant.

[aeh5040]

A picture would be nice!

[MangaNOID]

Hey @technicmath Gentle reminder that your supposed to post in English 

[Gray Gear]

Can you please post some pictures? I dont seem to be able to imagine what you are describing, but I am always intrested in Gearbox/transmission stuff 

[nicjasno]

I'll build it in the afternoon.

[technicmath]

Thank you nicjasno!

Here is a picture of the concept:

The old driving ring needs to be replaced by the new driving ring and the two 28 tooth gears are missing.

In this 4 speed gearbox the gears are
16/28 approx 0.57
20/24 approx 0.83
24/20=1.2
28/16=1.75.
Thus the ratios between the gears are
0.83/0.57 approx 1.46
1.2/0.83 approx 1.44
1.75/1.2 approx 1.46.
Since sqrt(1.44)=1.2, a gearing of 1.2 will give intermediate gears to obtain an 8 speed gearbox. Thus the 4 gears of the above 4 speed gearbox are gears 1, 3, 5 and 7. By using the gearing of 1.2 in combination with this 4 speed gearbox you obtain gears 2, 4, 6 and 8. Then a 2 speed gearbox with a ratio of 1.2 between the 2 gears is needed. This can be done for example by
(16 with clutch/16)x(12/24) and (20 with clutch/16)x(8/24)
or (16 with clutch/20)x(24/8) and (16 with clutch/16)x(24/12)
or (16 with clutch/20)x(12/24) and (16 with clutch/16)x(8/24)
https://bricksafe.com/files/technicmath/gearbox/Gearbox2.png
or other similar combinations.

Then the 8 speed gearbox has approx these gears:
gear 1: 0.57
gear 2: 0.57*1.2=0.684
gear 3: 0.83
gear 4: 0.83*1.2=0.996
gear 5: 1.2
gear 6: 1.2*1.2=1.44
gear 7: 1.75
gear 8: 1.75*1.2=2.1.
In this 8 speed gearbox, the average ratio between successive gears is approx 1.2 and the ratio between the highest and lowest gear is 2.1/0.57 approx 3.68.

This gives smaller gaps than in for example
set 42110: 4 gears 1:5 ; 1:3 ; 1:1,67, 1:1 (according to techlug review) => average ratio between successive gears is 1.71 and ratio between highest and lowest gear is 5
set 42083: 8 gears 1:1,67 ; 1:1,25 ; 1:1 ; 1:0,8 ; 1:0,6 ; 1:0,45 ; 1:0,36 ; 1:0,29 (according to techlug review) => average ratio between successive gears is 1.28 and ratio between highest and lowest gear is 5.76.

[Attika]

You did the math, for sure.  Sounds very promising, great concept. 

[Gray Gear]

Wow, I dont know about the math, but is there a better way to get this distance between the gears? Using Technic Bricks, ones with different hole placements as well, does not seem very practical to me.

[Touc4nx]

@Gray Gear You could do that:

And you don't have to do it sideways, you can make it horizontal.

 

[pleegwat]

@Touc4nxThat's just the 2*sqrt(2) distance.

[technicmath]

Thank you Attika.

@Gray Gear As described in the first post, the desired distance between the gears is 2.75 studs. On a studless grid, even with considering half-stud lengths, the closest approximation that fits is a distance of 2 studs in one direction and 2 studs in a perpendicular direction as in nicjasno's original design (see link in the first post). This gives a distance of sqrt(2^2+2^2) or approximately 2.828 studs. As described in the first post, using the design with technic bricks gives a distance of sqrt((3*2/5)^2+2.5^2) or approximately 2.773 studs, which is much closer to the desired 2.75 studs. This is really worth it. You can align the 1 x 4 technic brick with a studless liftarm, then the axle going through this 1 x 4 technic brick fits in the studless grid. The axle going through the 1 x 2 technic brick with 2 holes is not aligned with the studless grid, but using for example a gear combination 20/24 you can with the same design land in the studless grid again.

@Touc4nx The construction with the red perpendicular connectors gives the distance of sqrt(2^2+2^2) studs, which pleegwat already answered.

[nicjasno]

There need to be 3 shafts. 2 with gears and 1 with the rotational sequential switches.

The 2 variants. One without modified gears and one with modified gears:

[TheHypaaa]

1 hour ago, nicjasno said:

There need to be 3 shafts. 2 with gears and 1 with the rotational sequential switches.

The 2 variants. One without modified gears and one with modified gears:

Wouldn't the odd and even gears need to be seperated in order to be able to switch gears using the Bugatti shifter? Right now the sequence would be 1-3-2-4 or not?

[nicjasno]

13 minutes ago, TheHypaaa said:

Wouldn't the odd and even gears need to be seperated in order to be able to switch gears using the Bugatti shifter? Right now the sequence would be 1-3-2-4 or not?

Need to get the orange shifting gears first to see how this would work. But the order can ofc be shuffeled around to get the desired order.

[pleegwat]

When using rotary catches, the two sides of one selector are by necessity 180° apart, so you'd want 1 and 3 on one catch and 2 and 4 on the other.

The pairing used here would be suitable if you wanted to make an 'H-shaped' manual gearbox, rather than a sequential one.

[Jeroen Ottens]

2 hours ago, TheHypaaa said:

Wouldn't the odd and even gears need to be seperated in order to be able to switch gears using the Bugatti shifter? Right now the sequence would be 1-3-2-4 or not?

Yes they would, but if you combine this with the idea of making a 8 speed gearbox you can maybe use the other side to engage when this side is at the 'wrong' gear? I haven't tried to think it through, but there is something like half of the settings are not used on either side.

BTW: A very original and smart idea to begin with!

Edited September 30, 2019 by Jeroen Ottens

[Gray Gear]

12 hours ago, pleegwat said:

@Touc4nx

How do I remove a quote on mobile? 

 

Well, I am looking forward to a build utilizing this gearbox. It would find this pretty hard to incorporate in a Sportscar, as this design takes up quite a lot of vertical and horizontal space. But might be able to handle more torque than other gearboxes, so it might be good for Trucks?

[LegoTT]

My 2 cent there, for a 4gearboxe in a rc moc there is 300% between min and max there. By using the big side of an old diff we have a 4gearbox with 500%

[technicmath]

On 9/30/2019 at 11:14 PM, pleegwat said:

When using rotary catches, the two sides of one selector are by necessity 180° apart, so you'd want 1 and 3 on one catch and 2 and 4 on the other.

The pairing used here would be suitable if you wanted to make an 'H-shaped' manual gearbox, rather than a sequential one.

Indeed.

@LegoTT What exactly do you mean with 300% and 500% with the 24 tooth gear of an old diff?

I built a sequential version of the above 4 speed gearbox.

1. There need to be 2 additional orange changeover catches, 2 driving rings and 2 blue 20 tooth idler gears (instead of the tan 20 tooth gear in the picture).
2. The two grey angle #2 connectors need to be replaced by the smooth axle connector for the driving ring.
3. The distance between the two drive axles is 7*2/5=2.8 studs, which is better than the 2.828 studs, but not as good as the 2.773 studs.
4. Note the usage of 5.5 axles.

[nicjasno]

I am waiting for the changeover plates before i can make my version.

But just a comment... i'd use the old 2 stud driving rings, just to decrease overall length by 2 studs. Also, there's only 3 axles needed. The changeover axle being directly operated by the switching mechanism, like this:

 

[LegoTT]

On 10/2/2019 at 3:14 AM, technicmath said:

What exactly do you mean with 300% and 500% with the 24 tooth gear of an old diff ?

I mean if you use the new gear with a 16t like on the picture, the hight speed will be 3 time faster than the low speed.

But since the topic is about low-friction gearbox, which could be useful for cars with motor, it would be better to keep the old configuration because the hight speed is 5 time faster than the low in it, it has more application.

 

However, the old configuration is longer.

 

Shaft 1 : 20t with driving ring, driving ring, 16t with driving ring, 12t, 8t

Shaft 2 : 12t, 16t, 20t with driving ring, driving ring, 24t side of differential.

The low ratio is 8/24=0.33, the hight ratio is 20/12=1.66 which is 5 time more.

[Zerobricks]

How about this design I came up a week ago, but forgot to post it:

I simply offset the driveshafts allowing for more gear combinations without need for new clutch gears.

The pulley wheels with ball pins are there to transfer power over the slight offset.

The 4 gear ratios achieved are:

• 20:12 = 1,67
• 20:16 = 1,25
• 16:16 = 1
• 16:20 = 0,8 (overdrive)

Because you can switch the order of gears as much as you want to, you can easily use the wave selectors. I think you can even upgrade the gearbox to work with 6 gears.

Edited October 5, 2019 by Zerobricks

[LegoTT]

Thank you for this post

[TechnicRCRacer]

On 10/5/2019 at 9:52 AM, Zerobricks said:

The pulley wheels with ball pins are there to transfer power over the slight offset.

Does it work well? It doesn’t look like it will run very smooth.