Automatic Transmission Model

by emmett, published

Automatic Transmission Model by emmett Nov 17, 2012

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583929Views 126742Downloads Found in Engineering


Have you ever wondered how an automatic transmission works? I did, so I looked it up and then designed this desktop model. It has six forward speeds and one reverse. Real automatic transmissions have a hydraulic or electrical system that engages different clutches and brakes to shift gears depending on the driving situation. With this model you control those simplified brakes and clutches yourself.

The clutch is actuated by sliding the drive shaft through to different positions (which each have two gear markings), while three separate brakes each also have two gear markings. You select a gear by engaging the brake and clutch position associated with your desired gear. See demonstration video: http://www.youtube.com/watch?v=-FyC3dn3HJY

I tried to design the gear ratios to be fairly close to what some real cars use, and this is the result, where the input is the crank and the output is the annulus:
1st gear: 1 : 4.29
2nd gear: 1 : 2.5, 71% increase
3rd gear: 1 : 1.67, 50% increase
4th gear: 1 : 1.3, 28% increase
5th gear: 1 : 1, 30% increase
6th gear: 1 : 0.8, 25% increase
Reverse: 1 : -3.93

The OpenSCAD file is included and is highly parametric in case you'd like to play with different gear ratios. If you select a different number of teeth, it will print out the resulting gear ratios at the beginning of the output. I also used Matlab to investigate more thoroughly how the gear sizes affected the various ratios. I used transmission.m as an aid in optimizing the ratios to be somewhat evenly spaced.

This was all printed in PLA at 120 mm/s on a Replicator 1 with Sailfish firmware, default layer height (0.27mm). Everything came out perfectly on the first print. I swear, complex models don't have to be difficult, and who needs glue when you can print snap-fits?


All the STLs are there if you want to print the pieces individually, but using the plates is quicker. Print one each of stand.stl, gears.stl, carrier.stl, shaft.stl, crank.stl, handle.stl, and three each of planets.stl and pins.stl. To make the labels more visible, you can pause and switch colors a couple layers into stand.stl.

Each of the stand pieces has a brake, which is a separate element that is permanently captured by the larger piece. Make sure these can rotate freely (they can require some force to free if your printer leaves any strings). Then assemble the stand as shown in the pictures (they're designed to press-fit, so no glue should be required).

The herringbone gears are tricky to assemble because they cannot slide past each other, but they run smoothly and don't require thrust bearings like the helical gears in real automatic transmissions. All these steps are shown in the photos above. Start with the planet carrier right-side-up and insert two medium-length pins into two inner holes and snap idlers (smallest planet) onto them. Then mesh an upside-down sun gear to both of them. Finally, mesh the last idler with the sun and push its pin down through from the top to secure it.

Next, mesh a medium planet with an idler and push a long pin through from the back of the carrier to secure it. Attach a large planet to the other side of this pin (on the back of the carrier). Next, set the assembly with the idlers down in the middle of the annulus. Mesh the other two medium planets with the idlers and annulus and make sure they line up with their holes. Set a large planet on top of one of those holes and clock it until the flat sides of the holes line up between the large and medium planet. Then push a long pin all the way through to lock them together. Mesh an upside-down sun gear with the two large planets, then attach the last large planet the same way (again, being careful with the clocking so that the pin will go through).

Now that assembly will hold itself together. Put it in the stand so that the annulus faces the side that says "1 3", then insert the drive shaft from that same side. You may have to rotate pieces to get the hexagonal part to slide through. Use the short pins to attach the crank and handle to the drive shaft, and you're done.

Mine started out pretty tight, but after greasing the pins and spinning it for awhile it loosened up. Mostly I think it had to grind off the tiny bumps and strings that form in the gear teeth.

UPDATE: I've added front_loose.stl and back_loose.stl for anyone who is having trouble getting the brakes to free up. They use the same tolerance (0.25mm), but I've opened up the rest of the space around them to make them easier to break free. Note the stand plate doesn't use these, so you may want to make your own printing plate.

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Can any one give me the parts size spec iam doing in cast iron I need those sizes plss it's urgent [email protected] contact to my mail or reply in comment frnds

Is it possible to know which 3d program was used to create the parts.

Tried to gave you proper credits on twitter for this model, but you are not there :(. Open a twitter account emmett!

90% size not infill.

I have also run into this problem, and I reprinted the idlers and planets, as well as the pins. This time, I set them to 90%, and I used some grease, and that did the trick. Good Luck!


I printed this and assembled it but it doesn't rotate. As far as I can tell the gears within the annulus are too tightly packed making it very stiff and hard to rotate. Has anyone else run into this problem?

Yes. Print everything with -0.2 offset (in simplify3d)

what if i m not using simplify 3d? what to do in cura? or what are offsets for.

Comments deleted.


Model is very good.
I need to file for drawing technical drawing.
Are SolidWorks drawing file is shared?

This is very impressive!!

The big gear first layer was great for fine tuning my leveling of the build plate. I think i have 0.14mm tuned in about right now.

Great model. Works Beautifully!

Best "how a/t works" example ever!!!

I think that this build is really cool!! Can't wait to get my 3D printer to attempt making this project. The design is interesting and I like how the model incorporates the ability to change gears and shift the transmission into reverse. Good stuff!

I am having trouble printing the carrier piece, when ever i try the extruder moves too far on the x axis and it slants the whole build. It is going up a layer and over to the right instead of building straight up. As far as i know its just the carrier piece, any suggestions??

Absolutely loved this build! Really is brilliant design. All the parts fitted together beautifully and it worked perfectly. I had no trouble with the original brake design, but they were a tricky to get moving the first time. Coolest build I've done yet. Thank you for the great design and for sharing it.

It's screwless after all, right?

Yes, it is.

This is a great model.
I tried to open it in OpenSCAD, but the libraries are missing,
or can i download those from an other location?

thanks in advance.

printed and assembled at .85 scale. Very cool model. Pics incoming.

Does anybody have clearer instructions? The pictures are not that clear, and the text instructions are not as well, can somebody help a noobie out? Thank you!

There is another video in YouTube

You happen to have a link?

can you make a smaller one so that it works on the m3d micro

It shouldn't be too hard to resize them yourself. Just make sure you use the same reduction factor. I'm printing mine at 85% of original size.

I'm new to the dual head printing, but i see that he has some of his gears printed so that the outer most layer is printed a different color. What setting do i need to use to accomplish that?

Actually the only part that's a different color is the bottom and top layer ;)

Mar 3, 2015 - Modified Mar 3, 2015

I made a loose fit brace. See http://www.thingiverse.com/thing:706291

Now to try to figure out how it goes together :)
Kevin B

Loose Fit Brace

Can someone explain the "loose" files?? Loose gets referred to a lot, but what's the difference from a regular stl file?

The loose files have more clearance in the break so it is easier to print.

Would it be possible to get a loose brace too?


I needed the same so I edited the file. Can you see if it works for you? Thanks

Loose Fit Brace

Thanks a lot!! Works great!

My little Simple can't print the shaft in one go, so I split it into two pieces, keyed to reassemble. Some sanding is needed. http://www.thingiverse.com/thing:616431

by ehud42

Very nice model! When I first printed it out and put it together (I used ABS), the parts fit was so tight I couldn't get the assembly to spin freely Gear positions 2 and 3 were especially hard to spin. My crank pin hole rounded out and I broke the frame stops - that's how tight it was. I spent a bit of time filing the gear teeth but that didn't seem to work. After messing around with the gears in various stages of disassembly I finally realized that the problem was not due to the gear teeth (which actually meshes together very nicely) - but primarily due to side loading on the pins (particularly the ones that go through the carrier) caused by the gears pressing against each other too tightly. This creates a lot of rotational friction on the pins. It didn't help that I printed the pins at 25% fill, making them somewhat flexible and probably creating even more friction. So I did the following:

  1. Printed the idler and planet gears at 98% scale. I retained the annulus and sun gears at 100% scale. My thinking was that this would create a bit of a gap between the gear teeth, greatly reducing the side loading on the pins.

  2. Printed the pins at 100% fill (solid), and also at 98% scale. This would make a very rigid pin, and slightly undersized so they spin freely within the carrier.

  3. Filed the edges of the 1st layer of the gears. On my printer I have it set so the 1st layer gets squooshed down a bit excessively onto the bed - this ensures good bed adhesion, but also creates a little flange on the edge. This could impede good gear mesh.

Now it seems to work well. I still had to do a little filing to get the parts to fit together, but new the model spins a LOT easier. I'm wondering if it would work even better if I printed the idlers, planets, and pins at 97%, but I'm satisfied with what I have now.

Hey Emmett

Amazing work! Can I ask a quick question? I can't get OpenSCAD to render anything other than one of the side supports. Any ideas why that may happen? All libraries are loaded and pins.scad too... no idea on my part why it doesn't work.


Hmm, good question; I haven't opened that in awhile. Probably an issue with the bevel gear library (since that's used for just about everything except the supports). Either it's not loaded, or you have a different version where something is incompatible.

I assume you noticed the various parts are commented out so I can just display the one I want to work on, right? You might just need to uncomment a different line...?

I'm a dummy :) I never picked up that you had commented out everything else. Very new to OpenSCAD


You wrote that we need 3x 3 pins.. those are only for gears... what about handle? there are needed 2 more, which one? those shortest are too short a bit, and the 'medium' ones are too long....

No, the short ones are for the handle and crank; they were the right length for me. You'll end up with one extra. You only need 6 pins for the gears.

Comments deleted.

Im having trouble printing. the gears keep splitting! help plz reply

How did you print the sides of the gear red with the body black?

he just paused the print after a fer layers and changed colors.

May 30, 2016 - Modified May 30, 2016
Gyorg - in reply to kris_vanocker

This is the "Pause" script for simplify3d:

{REPLACE "\n; layer 6, " "\n;PAUSE\nG1 Z180 F3000\nM300 S2900 P200\nM300 S3000 P200\nM300 S5000 P200\nM300 S1500 P400\nM25\nG91\nG92 E0\nG90\nM82\nM24\n; layer 6, "}

paste it in "Additional terminal commands

He used a dual extruded to print two colours

Soon to be leaving thingiverse because of Makerbot's behavior towards open source.
Details: http://www.fabbaloo.com/blog/2014/5/25/has-makerbot-crossed-the-line-for-some-yeshttp://www.fabbaloo.com/blog/2...

Does anyone have a video of the assembly or some easier instructions? I'm having trouble figuring out which pin goes where and which one rotates and which doesn't. Thanks

can any one tell me what's the benefit/use of using a second set of sun and planet gears...which are not even in contact with the annulus(ring gear).....ALSO PLZ LET ME KNOW THAT HOW TO CALCULATE THE GEAR RATIOS ...!!! plzz do comment ....

The two sets of planets are connected to each other, hence connecting everything to the annulus. As for how to calculate the ratios, you can download my matlab script and read that, but really you just have to sit down with a piece of paper and lot of equations about tangential velocity.

Wow! That's awesome! Can I see your script?

I'm very impressed. I've been "doing things" with the thingomatic/mk7 for a couple of years now, just recently picked up a replicator-2x which I used for this build: orange abs plastic from makerbot in my case which worked perfectly. (I did try some gold colored ABS from another supplier but it actually had more "curl" in it... so I just reprinted that in orange too without any issues.) I used wood glue on the kapton surface to make sure there was no edge effect driven curl for some of the larger base prints, used rafts and supports in Makerware software and used 0.2mm layers with 3 shells and 25% fill. Assembly took just a little thought, but got it done. The ONLY think I had problems with were the movable stops -- on the front and back stand parts they were pretty well attached and I needed to use a chalkboard knife to weedle them a little for release. Then they worked. Tight during assembly, but not so tight that it didn't work. I'm still running it to smooth it out a bit, but haven't taken a file to anything yet. Have PLA here but didn't use it. The ABS is fine.

I love this design. I am busy printing it at the moment, but have run into a few issues with pins being too large to fit the gears etc. I would love to play around with the SCAD files and would like to ask if you could please upload the involute_gears.scad, pins.scad, and Write.scad files that are referenced in your transmission.scad file that you have already uploaded. For the frame, I found that the locks were sticking together (even in the lose versions), and after tweaking the tolerance I got a nice functional print. I would like to do the same for the pins, etc.

Figured I'd drop a note here. Half way though printing it, but I failed the Brace.stl print 5 times now. after actually staring at the print I found the little island inside the "R" wasnt sticking.. So check your beds are adhering to your PLA.. or sit there with tweezers and pluck is out if it moves.

great work. fantastic video.

Are there more instructions on which pieces should be printed? Not sure if all the files were mentioned in the instructions, so far looking great and I can't wait to finish this!

Excellent! Really creative!

This came out beautifully on my UM1 with heated bed. Couple points for possible improvements: 1. the 5th gear is actually a neutral, ie you can hold the output rigid while turning the crank. I think to power it you could add a direct coupling - a 4th position for the sliding crank. 2. Its kind of hard to get the correct slide position, maybe a clicking type of mechanism to let you know its in place would help. 3. The clutches like to go in and out of position on the sun gears. 4. Would be nice to have an output and an input shaft that are held rotatable (cant slide). To get it to run smooth, had to do some drilling of the small pinions holes. 5. Really is a great design, very fun to print out and try.

Printed mine on Makerbot2X w/ ABS (that's what I get for not reading the info COMPLETELY!).
Put it together. "worked", but didn't want to work. Everything too tight.
Pulled it apart, hogged out the holes a bit, shaved down the shafts a bit, put it back together. Still too tight.
Ended up breaking off a gear tab and snapping the main crank shaft in half!
Maybe one day I'll reprint what needs to be reprinted...Scale down the planet gears by a fraction of a percent, leave everything else as is, and see what happens.
And maybe that day I'll use PLA! :)

Great model, worth the print time... Thanks!

For anyone using Slic3r - if you get errors opening carrier.stl, gears.stl, or planets.stl, Slic3r will try to correct the file and will do it WRONG (as of version 0.9.10b - Windows). You'll see a weird "straight" section of the gear teeth that should not be there. I imported the STLs into blender and simply re-exported them, and that fixed whatever the issue was - slic3r was able to process them with no errors. Odd issue, simple fix!

Very nice model. However, the faceted surfaces have rather low resolution. Is it possible to get access to the original solid geometries in som way?

It's beautiful. I'm getting my 3D printer in a few months. I think this will be my first Large build (after calibration and small shapes to learn the machine before i really mess something up. haha.)

That is really impressive. Is it possible to shift gears while it is loaded?

What's the likelihood of issuing "loose brace" files as you did for the front and back stand parts? The braces built as part of the stand plate are impossible to free up.

parts does not fit

Amazing i think this qualifies as a manual transmission lol

Great model and design! I found that it is very easy to free up the brakes in the triangle frame parts by driving a thin knife through the gap.

Printed at 0.2 layers, 0.25 infill. The gears are a little bit stiff to turn. It is not because of strings and blobs, but more like design. I think additional 0.5 mm of tolerance between gears would make the world of difference. Still runs great!

Wow! I can't wait to try this!

Just printed this out on our UPrint, with a layer thickness of 0.01 and it runs great. We are trying to think of a way to hook up a small motor so it spins by itself.

Thanks a lot for making this an open download, my only complaint is that the STLs were not saved at a very high resolution so the output ring looks a bit choppy on the out side.

Overall an awesome model!

Great model! I would be awesome to try and implement a microcontroller to control the brakes etc as speed of input increases/descrease. Moving the clutch would be a right pain though!

Amazing model.

Printed everything on a reprap mono mendel. Worked pretty great. But we ran into problems with the breaks of the smaller (side) stand pieces. Using a lot of force loosens the break, but also damages the small stand piece permanently, so the breaks there don't work anymore.

The loose model for the bigger stand parts were perfect to print and the breaks run freely. Could you maybe provide as well a loose version for the smaller stand part?

Wonderful. The model is a delight and the auto transmission itself seems almost magical. I made the shaft in white so that I could use a black fine tip marking pen to make the markings for the gears easier to see.

A complete list of the needed parts would be nice. The platers won't fit on most printers, and I'm trying to figure out how many of what part are needed.
I would like to give the set to a friend as a gift, and it would be sad if I missed a piece.

Well, doesn't really matter, it seems my mendel90 isn't accurate enough for this. Nothing really fits...

Very well done! Awesome! It would be so cool to see it being shifting automatically using by servos or so.

Hey under gear.stl has 3 pieces any way to get those individual? stl for each of the three?

I can print just as fast as my machine can move. (It's a cnc router/laser-thingy.)

I can run at 20mm/s max and I find with my latest hotend I can easily outperform that extruding. However, when printing the gears I find it slows it down a lot to go between all the parts on the plates. I print the gears much faster if I tick off the "complete individual objects" in Slic3r. However, it still has issues with the sun gears as they have this hollow start with the key. If I use too wide extrude setting the teeth are extruded seperate and small infills added for each space. Narrowing it down I can get it to do a full perimiter on both inner and outer. It then goes around and dots in the fill in the teeth causing excessive pullback/fast-forward that seems to cause sticking in the feed to the head. It also goes back and forth between very very small extrudes in a pontless manner.
Anyone else experience this?
Is Slic3r just stupid when it comes to path planning for all the tiny infills?
Wouldn't it be better if it did the inner perimiter and took detours out in middle of each tooth for the infills? It could even pause extrude without pulling back as it traveled between the infills as long as it followed the circular path of the neighbouring (inner) perimiter while doing so. It would be much faster and produce a much stronger part.

hey so Im having trouble with the gears being pretty hard to turn. What can I do to loosen em up a bit?

I had the same problem and it's fixed! turns soooo easily now! Every gear - just like Emmett's video First I had to file down every pin a bit with a file. You probably already did this. I tried silicon spray but no help. Everything seemed loose and fine until I would put it together and it was frustrating because every individual gear spun fine. After an hour of slowly turning and staring and eliminating possibilities I realized one idler was different than the rest. Before then I took off the idler pins and made them slightly straighter so the idlers couldn't move around too much (would stay in place) but still spun well. The final key solution is that the idlers need to spin so freely that they coast when you let go. They have to be so smooth that they continue spinning long enough to see - maybe 1/4 second. There is very very little friction anywhere in this design and most of it comes from those 3 idlers. The tiny friction would move the sun gear over and it would jam. I was tempted to reprint that sun gear 1mm larger but didn't need to.

So far, all good except the shaft. I had to cut it in half with netfabb to print, but I am having issues with it staying to soft and getting messed up. Anyone have any good ideas for temperature and speed that I can try, also what infill should I use for the shaft? I am trying a fan now also, to see if it helps. BTW, I am using 220 C for the head, and 90 C for the bed

Had the same problem. It ocurred because the slicer (Slicer3) found a hole in the top 10 layers, it will say "hole at xxx,yyy,zzz trying to fix" Skienforge didnt do that but would not position the part on the bed correctly. Moving the part around in Blender fixed that.
When that happens plastic "leaks" out of the hole and occupies the full surface of those layers. What should have been there is the tiny 'pip' that indicates movement, which is 10 layrers tall but only a small part if the last 10 layers

Made it in ABS on the solidoodle 2, very tight fit!

Thanks for sharing! I printed it to 50% scale and it worked fine with my UP! printer.

nice to know it works at 50%, I'm getting a relatively small printer, and it will only fit on 60% or smaller

You're welcome. 50% scale is pretty impressive. You should upload an I Made One; I'd like to see it.

Thank you for sharing this. I printed it to 50% scale with my UP! and it works fine.
A nice way to demonstrate 3D printing

Printed 'gears.stl' at 50% and 75% scale and the herringbone gears end up with the herringbone changing direction to standard spur direction (parrallel to shaft) for the last 10% or so of the print... Is this normal or a scaling issue?

I had the same problem with printing the planets using pronterface (100% scale). I tried printing the planets 3 times with the same problem: they were straight at the bottom and then started getting the herringbone pattern. I switched to repetier and it worked fine.

Now I printed the annulus overnight in repetier and the problem came back. Although this time it started perfect, but now the top of it is straight. The sun gears printed fine. I did get the error when slicing all of them, but I just ignored it. So I don’t know what now. Maybe I’ll just dremel off the straight part of the gears.

I'm not quite sure what you mean, but that sounds very odd. A bug of some kind perhaps?

Must be a slicing bug. Thanks.

I love it, but many of the STL files will not slice using Slic3r, even after cleaning up with NetFabb offline. Any idea why?

The all slice just fine for me with Slic3r 0.9.7. And I didn't need to clean up the files. Perhaps you need the latest version?

I'm scaling this down to 80% and trying a print. Just starting the first slice now... I'll post an update with how it turns out eventually

A little bummed, Printed this all up on my Rep2 using ReplicatorG and the default settings, it looks fantastic! but nothing will go together. Shaft too wide, Pins to big, brakes aren't loose.
Gears fit perfect. but that's about it. The pins have to go in with a hammer and the even printing the shaft at .20 it stil will not fit.
any suggestions?

Im having the exact same problem. Would anyone know if possibly dipping some gears in acetone would clean them up enough for smoother movement?

You need to remeasure your filament diameter. You probably have it set too low and so you're extruding too much filament, causing surface expansion. Try just turning it up by 0.02mm.

I agree, you need to be very accurate with everything to print things like this. I measure my filament in at least 10 places with a digital micrometer, then average all the readings. If you use a caliper, make sure you use the wider part of the jaws so you don't pinch into the filament and get a reading that is too small. Also you may need to calibrate your extruder steps per mm. I use a test cube with a thin wall, print It until it's tall enough to measure and adjust as needed.

I don't know about your particular machine, but I found that I got much more accurate dimensions by printing everything very slow. Fast is great for some things, but not really that great for printing accurate things that need to fit together. belts have a little bit of spring and stretch to them and it tend to get a slight amount of over travel when going fast, and that will cause holes to be too small and pins to be too big etc. I printed all the critical parts for this at 13mm/sec for perimeters and 30mm/sec for infill... so it took a long time to print, but things fit perfectly. I thought I could get away with printing the frame fast and sure enough I had to file down the hexs to get the shaft to fit, yet I didn't have to file down the gears which I ran slower. The tall thin shaft also must be printed slow as at fast speeds that shaft itself will deflect causing size issues. hope this helps

It sounds like a calibration problem, and there are lots of forums full of people to help you out. Also, PLA will tend to hold dimensionality better than ABS. To print parts that fit together requires your printer to be in tip-top calibration.

I've added Neutral and Part by installing an even longer shaft so I can pull the hex drive all the way out of the stand.  See my 'even longer shaft' derivitive

about how long does it take to print everything?

I've been printing it for about a week on and off... but I had some issues to work out printing the sun gears out of ABS.  I also had to re-plate just about everything because my of my table size.. I'm also printing it in 10 colors, so I'm not putting a lot on a a time. 

I'm just needing the massive shaft, I need to split it, and I have this extra short pin, so I'm trying to see if I can use the pin to hold the shaft together... I think I have it about worked out, and hopefully will have it done tomorrow.  

I'm happy to say I got all the gears together and they all rotate nicely.  It's great to see them mesh together so perfectly after spending so much time printing them and not having any real way to verify them until assembly.  I am actually surprised at the precision of this, gears move freely but have no slop, pins are tight where they need to be, yet rotate where they need to.. and actually getting into it and printing it you see these small precision details that are not obvious from the photos... like indents in the gears to match little spheres on the shaft to make it snap into specific locations, and captive brake tabs printed while printing the stand.  This is the coolest thing I've ever had the pleasure to print!  Excellent work on this Emmett!!!

That depends a lot on your print settings, especially things like firmware acceleration. It took me a couple of days to print it all.

WOW. I want to print this.
Can anyone advise if it will print on the Thing-O-Matic? or is a Replicator required?

 I designed it to fit on the Replicator. You could probably print everything on a ToM except the annulus, carrier, and maybe the stand and shaft. You could try scaling it down, but the teeth will start getting pretty small.

Scaled the objects to 0.75 - prints have been good. Output needs some work and cleanup - assembly being worked on. Mesh of gears appears good.

What an awesome model!  It makes one start thinking... how does a positraction differential work?

My scad knowledge is pretty limited, how do I set up the 3 libraries this model is derived from?

edit - shouldn't have bothered asking, figured it out myself. Can't wait to finish printing!

How did you get the two colors on the same piece? Which printer do you use?

 All that info is in the description and instructions.

How much material (PLA?) would I need for this?

 Mine weighs 253 grams, but your answer will depend on how you skein the model (fill %, number of loops, etc).

How are you attaching the crank to the shaft.  I am using the smallest pins as I see in the pictures, but the the pin turns freely inside the shaft.  I can use some epoxy, but I thought I must be missing something.

Incidentally, I too could not print the shaft as >134 mm is way outside my build envelope.  I just modified the scad file to create a shaft that prints in 3 pieces.  I was going to use more of your pins to connect the pieces together, but I just added square "keys" on the top of the two bottom pieces and square "holes" on the bottom of the two top pieces.  The pieces slid together and I used a little JB Weld epoxy to hold them together.  Works great and the lettering is still legible.  If there is interest, I can post the changes.

Did you regenerate the file from OpenSCAD? I'm guessing you might be using pins.scad V2 instead of V3 (see ancestry). I added the fixed hole option, so it's probably just ignoring it. Unfortunately OpenSCAD isn't too good with error messages yet.

What authoritative source (or best?) is the place to get pins.scad and gears.scad?

Pin Connectors V3
by emmett
Parametric Involute Bevel and Spur Gears

Thank you. I see how this has been done now.... also needed to ensure I updated my version of OpenScad.

 Emmett - it's a damned good point, if you use pins V2 you get no errors but "round" holes for the lock-holes in V3..

Yes that's what I did - since I had to segment the shaft.  I don't want to print it again, so I guess I'll use a bit of epoxy.

Wow, another impressive Emmett creation!  Thank you very much!

May I ask how long it took to design this?  And your workflow?  I think we could learn quite a lot from hearing how you did this! 

Thank you. I spent at least a week researching automatic transmissions and thinking about the design. Once I got to the point of actually drawing it up in OpenSCAD, I finished it in one weekend. OpenSCAD can be a really efficient design tool, as long as you think about modules and parametrization from the beginning.

It took me awhile to figure out the right gear ratios (that's what the Matlab script is about), but that was also the most interesting part to me.

The other challenging part was designing the system of brakes and clutches. I really wanted to reduce the part count and make it as simple as possible. It took several iterations before I had something I liked enough to try modeling it in OpenSCAD. I'd always wanted to incorporate a captured, moving part in a design, and when I realized the brakes would work that way, I knew that was the answer. I'm by no means to the first one to do that.

What % fill did you use?  Mine (printed in ABS) does not turn easily, so my 25%-infill pins are breaking where the handle attaches to the main shaft.  I'll try a solid pin next.  But for today, I'll just call it done for the night!

 I generally print the pins solid. Try turning it in first gear (where you have more leverage) until the gears loosen up a bit.

It turns out part of the problem is that the crank itself deformed from the pin heads failing and then rotating inside the socket of the crank.  I'll rebuild those pieces again.

This is a great creation with some amazingly tight tolerances.  The herringbone gears in particular are such fun to have lock so solidly together.

But my thumbs and forefingers are still pretty sore from the building.  Getting those gears together inside the anulus was a challenge.

I filed every pin and hole.  I didn't file down the inside of the teeth though.  Maybe that (along with the super tight tolerances) is why I've got such high friction that I can't effectively turn this with the handle at all.  Instead, I have to grab two gears and roll them with my thumbs and fingers to see it in action. 

Gotta figure out which lubricant will help here.

Nonetheless, a fun and educational project.  Thank you.

This is an incredible maker project - great design!
Yes, I had to stretch the annulus when trying to mesh the last two planets inside the annulus. And the last pin was particularly difficult - used a hammer and broke two pins but finally got it lined up and through on the third attempt. It is very tight and only can move it by getting gloves on moving the large planets. I will keep working on it and might try some silicon lubricant (for bikes).

I printed everything on high resolution on a Replicator 2 with PLA,

The idlers are key - get them to spin very very easily (by filing down pins) and everything else will be fine - see my comment above.

 If the pins are too tight, it's easy to just re-export them with a new tolerance. My pins were fine, but the gears started out very tight. However, after playing with it and forcing it to slowly spin, it loosened up a lot. After a few days of playing with it, it operated like you see in the video.

this just might be the coolest thing I have ever seen.  I can't wait to use if for something!

I've got the entire transmission printed, but I've had to reprint the front and back of the stand twice because I can't for the life of me get the brake free. 

The braces printed fine. Any suggestions? I knocked out all the other parts just fine on my Rep 1. 

 I've just uploaded new front and back pieces (see instructions above), hopefully these will making freeing the brakes easier.

 I just printed out the back_loose part on my Rostock.  Much better.  A few strings to cut away manually, a little bit of force and the brake popped free.  I thin machines with Bowden tube designs just need a bit more clearance to compensate for ooze and strings.


Printed one of these out on my Rostock.  The gears work great, needed very little cleaning up.  The locking tabs are fused solid - I think my printer has too much stringing, I can't get them to move even with force and carving at the grooves with an exacto knife.  I also sheared the small tab joining the crank to the shaft, though I think that part came out a bit too weak on my printer.

 Hey Ellindsey - I just posted a "less plastic & time" way to test the brakes here - http://www.thingiverse.com/thing:34935http://www.thingiverse.com/thi...

I also fell back from 0.9.5 Slic3r to Skeinforge, and got a much better fitting one - almost too loose now with tol = .06.  I think it's time to try and run a calibration test and see if Slic3r has another bug..

Emmett's Brake Check

 Hmm, I've been wondering how good the retraction is with the Bowden drive on a Rostock. Maybe there's some skeining configuration that would help. Otherwise just take the approach below and try upping the tolerance.

 It's actually only the brakes on the 'front' and 'back' pieces that are giving me problems, the brakes on the 'brace' pieces popped free with not much trouble.  I am using Slic3r 0.9.5, and although I've tuned it for retraction I still get some stringing from my Bowden setup, so that's probably the problem.  I'll try re-printing those parts tonight with a higher tolerance setting.

 Beautiful print though, congrats on being first.

Hey Emmett - what size nozzle are you printing with?  I'm printing my stand now, and with a .5mm, it looks like I'm gonna have a heck of a time with the brakes....

 Yeah, increasing tol is definitely the way to go, shouldn't make any problems, just loosen everything up. I'm using a 0.4mm nozzle and the brakes needed some force to break loose, but then the tolerance was great.

 Thanks - increasing it to .6 seemed to do the trick, but I still had to resort to the exacto to get the free, and then the cylinder component is almost too loose...

134.875000 is too high for my printer ... 
would this part still work if i tilt the print?

 You can try scaling all the parts down uniformly. I'm not sure what you mean by tilting the print, but go ahead and try.

Ah, I ment just laying the shaft on its side, and printing it supported. Guess i'll just try it :D

 My half-shafts are about 1/2 done, and seem to be working as far as looks go!  Just need to see if they will still fit! :-)


Emmett's Not-Quite-As-Large Shaft

 Hey Emmett - I'm running into the same sorta problem - your "shaft" is huge! :-)

At 134.88, it's a bit higher than I'm gonna squeeze outta my Prusa, and the Rostock's been cannibalized for a Kossel - so gonna have to think a bit on this one.

I could pretty easily slice it in half, and was thinking doing it at the seam of the nut to the shaft would be a decent place to do it - and then extend a smaller OD shaft off the "top" and cut a matching ID hole in the "bottom" of the piece left with a nut. 

Would mean offending your "NO GLUE" ethic, but might give me a working toy! :)

Oh goody that saves me a lot of work. One of the many mechanisms on the list checked off. Thankyou very much

Must.  Buy. More. Plastic!

Wow, just wow...

is there a difference between an automatic and manual transmission?

 Indeed there is. A manual transmission is primarily designed around the shift lever you hold interfacing with the spinning parts. Lego actually has a surprisingly accurate model they use in most of their big technic cars.

absolutely amazing! 

wow, thats amazing work!

Emmett is a clutch player.

good work, love seeing things (ouch) like this.

This model is just breathtaking! Thank you for sharing.

Funny, I was just wondering how a manual transmission works :P 

Jeez, dude.