I've had this one in the building stages for quite a few weeks. I would have had it up sooner, but things come up. So here it is, my transmission/gearbox tutorial. I have built a couple of different transmissions here to show you different types that are out there. I also take very little to no credit for these designs. The only one I really "came up" with is the 5+R, but it was based on the 4 basic 4 speed.
Transmissions, or gearboxes give your creation the ability to change speed, and tourque ratios. The first thing I Should go over is gear ratios. Now if you are really lazy, or just short on time, I highly recommend Sairel's Gear Ratio calculator. Heck I recommend it even if you are good at calculating gear ratios. The main reason being that it allows you to enter a whole gear system, and then enter a motor, and it will calculate the theoretical RPMs (Rotations Per Minute) and torque. It also has a handy little gear coupler, which allows you to find where you can put gears realitive to one another.
Anyway, back to gear ratios. A gear ratio is the number of teeth of the drive gear to the follower gear. The drive gear is the gear that is being powered, and the follower gear is the gear that is connected directly to the drive gear. So if you have a drive gear with 24 teeth, and a follower gear with 8 teeth, the gear ratio would be 24:8 or when reduced, 3:1. When calculating a gear ratio, it's best to reduce the gear with the smallest amount of teeth to 1. Don't get overwhelmed with gear ratios, you can always use the previously mentioned calculator.
I have included 4 different types of transmissions in this tutorial. They are:
Linear 5 speed
Automatic Transmission
4 speed + Reverse
5 speed + Reverse
1) Linear 5 speed
This is basically a extended version of the linear 3 speed featured in Thomas Graafland's tutorial. I first found this on a youtube video. It is really simple, and has some good features that you can't get with the lego shifter collars (Those red pieces that allow you to shift gears). One being that you don't need shifter collars, all you need is gears. Another is that it is pretty thin, and can be put in smaller creations. A draw back is that you have to have a shaft to go through both ends of the transmission.
1st gear 1:3. The input shaft is the bottom shaft, and the output shaft is the top shaft.
2nd gear 1:1.667. Notice that the first number is still 1, this means that it is still the smaller gear.
3rd gear 1:1. When you have a gear ratio of 1:1, it means that the input shaft will turn at the same rate as the output shaft.
4th gear 1.667:1. This gear ratio has the 1 at the end, this means the smaller gear is the follower gear.
5th gear 3:1. As you might have seen, the 1 and second gear ratios are the inverse of 4th and 5th gears, This transmission has a fairly good range for it's size.
2) Automatic Transmission
An automatic transmission shifts automatically depending on the speed of the engine. This lego one shifts on the principle of drag, using a differential to move the shifter. This transmission came from Sariel. Sariel is a very good technic builder, and I often go to his website for building tips. He has a gear tutorial here which is really good, if you have the time I suggest you check it out.
This transmission has a rubberband that pulls the shifter to hi gear (1:1). The lower gear is (2.77:1). When the motor turns, the tire turns, but when the wheels encounter resistance, the differential starts to turn, and it turns the shifter forward.
When the shifter moves forward, it shifts into low gear, and the motor can turn faster, and the wheels can turn easier.
One advantage to this type of transmission is that it can change gears by it's self, and thus relieve stress on your drive motor.
Some disadvantages of this type of transmission is that some times, it doesn't shift right, and the gears grind, also it takes up more space than a manual transmission.
3) 4 speed + R
4speed + R, a fairly versatile transmission that is equipped with reverse, and a neutral. This transmission requires 3 shifter collars. It is based on a compact 4 speed which I also found here on Sariel's website. I have modified the 4speed to include a reverse. It is not necessary, but I think it makes it more realistic.
Top view with 3 shifter collars. The shift patteren is a standard H pattern.
1-3
2-4-R
The tan is the input shaft. The gear ratios are as follows, 1st 1:1.5001, 2nd 1:3, 3rd 1:1.667, 4th 1:1, Reverse 1:1.5001.
Red is the output shaft.
The three little 8 tooth gears are the reverser gears. To add a reverse to your transmission, you have to include 1 more or less gear than your main gears have. I simply added 1 more gear to achieve reverse.
4) 5 speed + R
After building the 4 speed + R, I realized that I had space on the reverse shifter rod for another gear, so I started out to make a 5 speed. It became clear that I had to move all the gears around. I first had 5th gear on the same shaft as reverse, but this made reverse the same gear ratio as 5th gear, which didn't fly for me.
I set out to put first gear and reverse on the same shaft. This was easy enough, but when it came time to move 2nd gear, I had to do some creative engineering.
Where third gear was already in the right spot, I didn't want to change it, so I came up with the solution of making 2nd gear, and 3rd gear both on the center shaft, but spliting the shaft in the middle. This allowed me to achieve the gear ratios I needed, with out making it too much bigger.
4th and 5th gear were fairly easy to build, after solving the problem of 2nd. The red is the output shaft. This transmission is a little bigger than I'd hoped it'd be, but it is still fairly small considering it has 5+R gears.
Yellow is the input shaft. This one also has a H pattern.
R-2-4
1-3-5
Gear ratios are as follows: 1st 1:5.001, 2nd 1:3, 3rd 1:1.667, 4th 1:1, 5th 1.8:1, Reverse 1:5.001.
Here is my video.
I know this one was quite wordy, and I didn't cover everything, but I try and keep things simple for the beginners. :) Thanks for looking!
Quoting Jon Treasure
yet again george i need your help. im building d10, everything going great, i take it outside for a test run, and all heck breaks loose. do you have any compact gear setups that might help me to change the direction of the axel 90 deg. so its facing out, and have no slipping (or clicking)?i tried the the latest horseshoe type holder that im looking for. it works perfect for low torque but i need some that can withstand lots of torque. Thanks george!
Superb excellence! I like the straight-forward explanations and such. And your more complex transmissions look nice. One thing I'd like to add is that in your linear transmission, the sliding axle must be inside both the brick liftarms at the end, otherwise it'll just click when you move it. Still a great guide, and I'm glad you've made these!
Yet again a great tutorial for beginners (like me). When I have my new computer I will definitly use one of these transmissions in one of the new creations I will build.
I like it
Chris Melby
May 25, 2012
I like this one, I really like how compact you got that last gear box, that gives it a lot of application ability. Very cool, BTW, let me know if you ever want to off-load those rare Modulars! Chris
yet again george i need your help. im building d10, everything going great, i take it outside for a test run, and all heck breaks loose. do you have any compact gear setups that might help me to change the direction of the axel 90 deg. so its facing out, and have no slipping (or clicking)?i tried the the latest horseshoe type holder that im looking for. it works perfect for low torque but i need some that can withstand lots of torque. Thanks george!
Quoting Chris Melby
I like this one, I really like how compact you got that last gear box, that gives it a lot of application ability. Very cool, BTW, let me know if you ever want to off-load those rare Modulars! Chris
Thanks Chris! Those Modulars are my mom's, and I don't think she wants me to sell them, sorry.
Quoting Fritz K
Whoa! This is so cool, George! It is very complicated, but still easy to understand when you say it. Maybe when I get home, I'll put this to good use, with a new technic vehicle from me!
Can't wait to see a technic vehicle from you fritz!
Excellent and most informative, and well written and with good visuals. Although I can viusalize the action in my head... seeing it in action in the video really did it for me! Now all you need is a minifig of appropriate scale to operate the stick-shift from inside the vehicle... hee, hee! :)
I can't say that I can completely understand how this works, (its really complicated looking!), but really nice tutorial! Can't wait to seen any of your future MOCs!
Whoa! This is so cool, George! It is very complicated, but still easy to understand when you say it. Maybe when I get home, I'll put this to good use, with a new technic vehicle from me!
