2-speed Automatic Gearbox
My first automatic gearbox, based on a design by Misha van Beek, but improved and simplified.
I always liked the idea of incorporating automatic gearboxes into large models, unfortunaltely such gearbox designs are unique and I only know two by Misha van Beek. While both are advanced and show great knowledge of the author, they are also large, complex and none changes gears smoothly. I thought that the new, small differential may give me a good opportunity to create a more useable design. I had three simple goals: to make a gearbox that is small, simple and above all capable of changing gears without jamming. The two first were easy, the third one took some time to work out, but eventually I got exactly what I wanted.
The basic idea of Misha’s design is to use a differential to transmit the drive in such a way, that if the resistance of the output grows, it will at certain point trigger the gearbox to switch to lower gear. Thus the motor will have a better chance to overcome the resistance, and once it’s done the gearbox will switch back to the higher gear. Whereas Misha has taken this idea further, and created gearboxes with more than just 2 speeds or with no fixed gear ratio at all, I considered two smoothly operating speeds a better option than three or more jamming ones. The lower gear has 2.77:1 gear ratio, and the higher one has 1:1 gear ratio. I have been experimenting with more different ratios, but as the difference increased so did the tendency to jam while changing gears. The 2.77:1 ratio difference should be sufficient in most cases, and it offers a reasonably smooth functioning of the gear change mechanism.
The construction of the gearbox is really simple. It fits into a 8×12 studs rectangle (plus the middle shaft protrudes out by 1 stud on higher gear), and axles of any length can be put into input and output without taking the gearbox apart. Moreover, the horizontal liftarm which servers as the gear change lever, provides a lot of space to adjust the tension of the rubber band accordingly to the weight the gearbox is supposed to handle (namely, the towballs it sits between can be put closer or further from each other).
You can see the smooth functioning of the gearbox in the video. I have also provided a parts list (just 45), an LDR model of the gearbox at lower gear and higher gear, plus an exact instruction which can be found below.
Photos:
Video:
Media reference:
blog.kockak.hu, Bricks ‘n’ Gears
@Chili
No idea, go ahead and give it a try.
@Sariel
How about 10-60n.cm-ish on my f1 race car im trying to build?
if i would adjust the rubber to so high it wouldnt trigger while pulling its weight(1kg?)
@Chili
It can be adjusted, but no, I don’t think it could handle the kind of torque you have in trial trucks.
Can the point of gear switch be adjusted with rubberband type/many bands?
If so would this work on trial trucks etc..?
@blarson
No, I don’t.
do you think this setup could be used with large wheels
and what is the name of the song that is played in 2-speed Automatic Gearbox
thanks
I built this with lift arms and found it worked exactly as described. The only problems I had were the two gears on the center axle would gradually creep forward, and occasionally both would engage and the system would bind. another half-stud in length would likely fix the binding issue, though high rpms do pretty much minimize the risk. I think I could have solved my problem with the gears sliding about with a better match between the gear and axle (searching for a tight fit).
I think more gears could be added by simply lengthening the input side of the mechanism and using a few more gear matchups, but this would negate reliability and smoothness.
Overall, lovely concept. I must make it a little more compact and put it in my mini trail truck that I am working on. (same idea as a trial truck, but something like half the size.)
sorry i found them
hi i dont no were the instructions are for the 2speed automatic gearbox could you help? thanks
@bobsurankle
Very interesting, thank you for bringing this to my attention. I’ll have to try something like that, but I’m afraid it doesn’t work well at low speeds.
I found this on couple of days ago…:
http://www.youtube.com/watch?v=LBIbMWq1ktI
http://www.youtube.com/watch?v=uqf4D5juBJs
http://www.youtube.com/watch?v=Q1G2SylEllg
…do you think that you could make it smaller in any way?
Thanks.
@wessel
I don’t think an automated gearbox would work in the Truck Trial. There are actually very few gearboxes that would do that. As for the shifting, I encountered no problems with that so I’m not sure how could I solve yours.
I think your main subject was to make a gearbox fit for a trucktrial?
So everyone, don’t make drag cars!
anyway, could you make the red shift part more horizontal, so that it matches with the gears? The shift connector keeps pulling at the wrong side (top left instead of left) and makes the gear shift piece bend a little where it should slide. This makes a lot of friction!
@RjbsNXT
I probably could, but it would be large.
i realise this is only effective for one direction, other wise there is no gear switching; i was wondering if you could use this is connection with your direction sensitive gearbox to create a 4 gear fully automatic gear box?
@jonas
In most cases it’s the fault of rubber band being too tight or too loose.
hi i can not get it to work
@Simon
MLCad.
Which program do you use when you animate the lego-ideas?
@crawlerdude
In my brain, very likely.
This is awesome where do think up ideas like this
@Sariel
ok thanks sariel.
@legobuilder
If you need a higher speed, some gears after the gearbox should do it.
You can also design a gearbox with a high speed switch?
@Sariel
yes, i think that will happen if you place them behind each other, but, I’m going to try out! first I’m going to get all the necessary parts from bricklink.
@max-o-l
This is possible, but it may be very unreliable. There is no way to make sure that the gearboxes will be triggered one by one. More likely they may start to trigger each other.
sariel, in theory, if you put like…3 or 4 of these automatic gearboxes
after each other, would it work then still too? becouse then you can have a 8 automatic gearbox, but is this even possible?
@Eugene
Since they’ve chosen to sell their ideas for money, that would be pretty much like stealing from them, don’t you think?
I’ve seen this automatic gearbox that LPE Power has made. Can you try to find out how it works. Here is the link: http://www.lpepower.com/content/heavy-duty-automatic-transmission-10
have you ever tested it on a real car, cause I have been working with previous models of you and it doesn really work that good. perhaps this model does work better, because it lookes pretty strong etc. Although the resistence necciserely to make it go faster isn’t that much. Right I just see that you have put it on a vehicle, so I did not really make a point, but I”m too lazy to delete everything xD
@Arnau
I’m sure there’s a FAQ on the LDraw’s or MLCad’s site somewhere. You may use Google too.
If I download the latest parts update, will I get all the parts, or do I have to do every update?@Sariel
@Arnau
Try updating your parts library from here: http://ldraw.org/
Pneumatic hoses are not modeled as far as I know, but the cylinders, valves and other stuff is.
I’ve downloaded MLCad, but I can’t find pneumatics in it. Do you know if you can use pneumatics with MLCad?
thank you very much, you have much attention for your fans!
i gonna try this immediatly!:D
@sergio
Here: http://www.brickshelf.com/cgi-bin/gallery.cgi?f=73968
About 10 seconds of using Google is all you needed.
ok thanks, but i don’t have the new differential but the old one, how i can make a automatic gearbox with that?
@sergio
Yes to both questions.
is it possibleto make a 3 speed automatic gearbox?
and works this for a 4×4?
@Jimbo
It can be done with any differential, it will just be larger and more complex.
with your 2 speed automatic gearbox, can you make one for the old diffs
but alsa a great idea ilke it!!!!!
While I haven’t obtained a differential I’ve found that the gears are to close together in your build and kept jamming. To compensate, I worked on elongating the design so that there is more room between gears to give space for the gears to not overlap. It’s a bit messy but I think it’s getting there. Thanks for sharing!
Just built this gear box to test the shifting. Worked OK, but I also found mine to struggle a bit with shifting to the lighter gear. I think the rubberband I have is a bit to strong. Gonna try with some other ones tomorrow.
Keep up the good work.
@Nicholas Carter
Perhaps you don’t drive the input fast enough? You have used double bevel gears in the changing mechanism, I guess? Aren’t they perhaps worn? I’ve heard from a number of people who have reconstructed this gearbox that it worked smoothly for them.
I built this just about exactly the same but with the older differential (because I dont have the new one). The problem was that it kept on getting jammed when I tried to change gear. Any suggestions?
Nice and compact. I have to try to build that today. Should fit fine for most cars.
Great work, I like the video!
Wow, I´m really amazed. That´s some great shit!
Can´t wait to try this out. Once again, great work!
@Agent567
There where you can get any other part: http://www.bricklink.com/
Where can you get the diferential?