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Mazda RX7 Wankel Rotary Engine 13B-REW - Working Model

by ericthepoolboy Jul 30, 2018
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I am having lots and lots of issues making the coils. Are they absolutely necessary, or can they be ignored?

hey i printed this engine and i look for the electric motor.

what king of motor RPM? gear? center holes? size?

Would you consider doing a Volvo 5 cylinder? More specifically the B5254T4 it is the best 5 they made and it's seen versions in multiple cars such as Mazda and Ford also

I would like to see a 5 cylinder also. VW has a VR5 engine they used in the late 90's and early 2000's. The first iteration (AGZ) was a ten valve cylinder head and the second release ( AQN/AZX) featured a 20 valve head. But any 5 cylinder engine would be cool.

Hi, Eric. Ive started the assembly process of the model. Ive made the TX and RX coils. Studying the wiring diagram and your video on the smart rotor assembly. In the hardware list you state "diode". Ive gotten colored diodes. Do you have the specs for those black diodes you use in the video? Also, the mylar cap in the video is green. Ive gotten some brown yellowis on 0.1uf. Will this be useable?

Where is the pdf for instructions I can't find it?

It is in the list of files.

It wasn't enought that you simply modeled the engine, but you went and made it so that it can be used as a teaching tool and that's what I find way more amazing.

Hi. I am very new in 3D printing. Eric Can you or anyone guide me or send me some links related to basic concept and it's commercial application. I am looking at it as a profession. Please guide me from business point of view.
Email sumitrban@gmail.com

hello that could maybe help some one the electrical motor he is using is DFGA32RI-13.8I A608

Hi, Eric. Since Im done with the LS3 engine, I want to start a new project. I looked at the boxer engine, but couldnt figure out how many of each part to print in what color, so i landed on the wankel. What dimension are the barrel hinges, please?

This is a awesome design! I must build on of these!

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Is there a part number for the addressable LEDs ? I'm having trouble sourcing the right ones

Hello.eric!Excuse me, what specifications are the wires used in RX and TX?

Hello Cbpejj,
It is 30 AWG (0.254mm diameter) enamelled copper wire.

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Het I have printed all the parts and have almost all the non printed stuff. But I don't know what exact motor to get? Do you have the dimensions for the one you used?

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hey did you print the compressor wheel with or without support?

compressor wheel without supports. if printing in PLA you need you part cooling fan turned all the way up and sometimes that's not even enough. I've had to add a desk fan to cool the part on some of my printers.

Hello. I work on advertising for Mazda. Would love to get my hands on an unassembled kit. When and where will it be available? cost?

Shoot me an email at harrell.eric@gmail.com. I have been selling un-assembled kits, just havenb't posted them yet.

Hi what size bearings do I need for a full size engine? and do i need to drill out holes for metal insert for full size??

hey, i was wondering what extruder mm, infill, and xyz demensions you used for this print. i couldnt find it on the front page. im planning on printing it myself.

You are the best, Thank you for sharing your work. I am a passionate about engines, but I do not understand anything and with your work I have the possibility of being able to understand better how this engine works.
Best Regards

What do i have to do to order this complete so i
can put together i love wankels and would die to get this.

Hi, really impressed by the engine but in the images the turbo snail housing plate has some rings for the screws but in the file they do not appear. Is that a bug or something else?

You're probably seeing some brass inserts from a previous iteration. I used them all over the turbo assembly but they were completely unnecessary and just wasted a lot of time installing them during assembly.

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Hi, I just finished putting everything together and followed everything as in the videos. I have two problems. one is that the smart rotor turns counter clockwise instead of clockwise. not sure why if I connected everything as you did in the video. I think this my might be a simply fix of just changing the cables on the motor itself. Another problem I have is that when I installed the smart motor into the housing, the LEDs did not light up. when I finished making the smart rotor and tested it by connecting it to a power source not connected to the computer it worked fine. not sure what is wrong with the TX and RX coils. is there any way to test if there's anything wrong with the coils? I did clean the coating off the copper wire so I know its getting connection.

I need to make a troubleshooting guide for this, but until then. Can you measure the resistance of the coils at the solder points to the board or the screw terminals? Does the light on the arduino turn on when you plug power into it? If so, does the light on the MOSFET module turn on shortly after? If so, try measuring the current at the 12v in on the MOSFET before and after the light turns on.

The resistance at the screw terminals came out to 1.4 ohms. When I plug the power I do see the Arduino light come on, then after about 5 seconds I see the light on the mosfet turn on. I measured the voltage on the mosfet and it read .011 as soon as I plugged it in, then when the light came on, the voltage went up to .333 volts. I had the meter on auto range, so I hope that range is correct. one thing I forgot to mention on my first post is that when I had finished assembling everything and was testing it, there was a small short. One wire strand (positive) from the 12v power supply made contact with the negative wire and made a clicking noise. after that all the LEDs turned off and motor did not turned. after disconnecting the power, and fixing the cable, I plugged it back in and everything worked again. not sure if that burnt something on the board. I didn't put the smart motor before that, so i'm not sure if it worked before that wire short.

i'm editing this post because when I touch the mosfet with just one lead from the multimeter I get around 4.2 volts.

Sorry for the delayed reply. Use the AC voltage setting on your multi meter to check the voltage on the output to the Tx coil. Most multi meters will display some voltage reading even though it might not be accurate. If you're getting a voltage reading when the LED on the mosfet is on and no reading when it's off, the problem is most likely with the rotor electronics. If you're still getting no voltage when the LED turns on, it could be a bad mosfet.

If you are getting voltage on the Tx coil, install the rotor assembly into the housing with the oil pan electronics on. Test for voltage using the AC setting on your DMM on the coil terminals. Next use the DC voltage setting on your DMM and check for voltage on Vin and ground. If you are getting a reading on the Rx coil terminals but nothing on Vin, you likely have the bridge rectifier configured wrong.

Hi, thanks for the reply. I checked the TX coil and I was getting current. when I placed the rotor assembly into the housing with the power on I did get voltage on the RX coil terminals but not on the vin and ground. when I was checking the coil terminals, one tip of the meter made contact with the switch and noticed the light in the arduinos turned on, then off. When I made contact again and hold it for a bit longer, the LED light turned on but then it turned off. then the light in the arduinos only turned on very dim. i took pictures of my wiring but not sure if you can tell whats wrong. The only thing i can tell you is that the middle top and bottom diode bridge connections, the Mylar cap, and the RX coil terminals are all twisted together and soldered together. not sure if the Malar cap had to be separated from the diode bridge. is there any way to show me your set up? I think this is where the problem is as you suggested.

Not sure what I did wrong, but I just finished the smart rotor wiring and got the board programmed, but the LED's don't work.. I've plugged it in to a usb power supply and at first nothing happens. I move a magnet near the reed switch and the LED1 lights up and cycles through the colors. LED2 and LED3 don't light up at all. I've tried it wired up 2 different ways, as according to the schematic, the reed switch red plugs in to the 5v, but in the video it's wired in to the VIN. Maybe I just don't understand that part, but wired up both ways gives me the same result of only LED1.. Not sure if I cooked the leds soldering them up? And yes, I made sure the switch was on...

It sounds like you’re half way there. The program is loaded and working fine. So you problem is mostl likely in a connection or component. When plugging into usb power make sure you use a power only usb outlet. The arduino shares the tax/RC pins with other I/o pins. The reed switch is supposed to go to the 5v on the board. The video is a little confusing at that part and I need to correct it. Do you have 5v going to LED 2 and 3? The slide switch turns off led 2 and 3. So it might be a easy as that. But check for power and make sure that the digital in on each led is going the right direction. The arrows should point down the length of the strip. I’ve soldered a few of these LEDs and have never cooked one.

Hi There,
Once again, a fantastic engine. I have built everything, but am having issues with the Smart Roto Program. Everything is wired correctly but the program will not work as in the Video. ive tested the ATTiny85 board with the test program and this works fine. Ive also built a second bench circuit and again no LEDs run.
Any Ideas would be great!!
Thanks in advance.

Couple things to check. After uploading the RX code to the ATTiny85 board, does the light on the board come on when powered by the coil or by usb power? Does the light on the board turn on when you put a magnet next to the reed switch?

Hi Eric,
Yes, as soon as the board is powered up the LED on the board comes on. When a magnet is put next to the reed switch the second LED on the boards come on, and when removed the LED goes off.

And you have the polarity right going in to the addressable LEDs? As well as the signal wire? Do the LEDs do anything at all when uploading the code? When testing the board, are you powering it with usb power only, not a usb cable that's hooked up to the computer? If you can send me a picture of your assembled circuit, that might help,

Is the drill stop available somewhere? I've had to reprint two items already, because I'm klutzy with the drill freehanded.

Next design a v twin?? hmmm

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Hello, it's perfect for this design, but due to the regional restrictions, lead to can't broadcast on youtube video, I want to ask in an assembly of electronic components is on the engine which position, because in the PDF, I saw the assembly of electronic components, but didn't find the electronic components in the engine which position. Maybe you mentioned it in video, but China is not able to see it on the Internet. I hope you can solve this problem for me, because it is really a masterpiece and I really want to make one myself. thank you

There is a schematic for electronics in the oil pan in the instructions.

Amazing design. I already have my hardware kit and most of the parts printed.

A previous comment requested instructions for the transmission coil assembly, and it was indicated that there was a video listed in the beginning of the description. I don't see any videos other than the one showcasing the final product. Does anyone have a link to the transmission coil assembly video?

[edit] Found them, they are on page 3 of the PDF

Does anyone know what size the barrel hinges are?

The hinges in the kit are labeled "5 x 25mm Barrel Hinges", they are 5mm in diameter, and 25mm in total length.

Need to print one of these out to put next to my FD model at work. Particularly useful on days when I drive the FD to work. :)


What's the size of the Barrel Hinge? I found in Ali 1.8 x 0.5cm (0.7'' x 0.2'') version, but I'm not sure if it's the correct size.

I belive it is 5mm x 25mm

Do you have any suggestions for print settings on esun bronze? I am finding it darn near impossible to print with this stuff. If not, can you recommend the bronze filament you used for this?

I use hatchbox bronze. Haven't had any problems with it. When I used to print with eSun, I had nothing but problems.

Great design! I'm about to start on making my own, but was wondering if there is a way to create a magnetic cover to the front housing in order to peak in while it is running. Such as in this model, https://www.thingiverse.com/thing:3053520

Wankel Rotary Engine Mazda RX-7 13B Working Model

Where can i buy those barrel hinges? I cant find them anywhere in the right size and i cant buy the kit because they dont ship to germany.

They are difficult to find, but they are most commonly used in wood working for small jewelry boxes, etc. I can ship a hardware kit directly if you want. International shipping would an additional $25

Thanks for the answer I‘ll try to find them because i‘ve already bought everything else

Hi Eric. Amazing work with this design. The way the 3 piece eccentric shaft comes together is pure genius!

I'm nearing completion of the model and just wondered if there was a trick to the polarity of the magnets inside the rotors? Are they supposed to pull against the magnets/hardware in the eccentric shaft? I am not using the smart rotor.

P.S. the little visual coolant blocks are a good test of bed adhesion haha. Another note, is I rotated the lower intake manifold 90 degrees, more akin to the orientation of the upper manifold. If you have your support settings dialled in (to avoid untidiness) I think it's a safer option than relying on a brim to hold the piece upright.

The magnets inside the rotor are meant to stick to the two larger bearings on the eccentric shaft. They don't need to be in contact with the bearing. The slight magnetic force just keeps the rotor from wondering out of the housing when it's open. As for the visual coolant blocks, I like to print them with the first layer really smooshed so that the "elephant foot" of the first layer allows you to just press them in with out glue.

WOW!! Amazing good work, impressive!

I love your designs. Maybe one day I will print one. What is the chance on designing a ducsti motorcycle teststreta engine? That would be amazing.

you should print out a nissan RB26 engine

"All three of them." Ha!

Great model, the LEDs are an awesome touch!

I LOVE thats. One question is possible tour upload one 2jzgte or s2000 engine? (F20c) please.
Thanks for your Jobs.

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Moving along nicely. Waiting for the non printed kit to arrive. Thanks for designing this and sharing it online.

I would love to see a 2JZ next! All of your engine models are spot on!!

How much material did this require? Thinking about making one.

I'm guessing a 1kg roll total

Absolutely awesome design. Adding it to my list until I have some free time to make this! Great job!


Thank you for this thing! Thumbs up to you!

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Awesome engine and going to print it. Do you have links to buy the non-printed parts? Specially the barrel hinge & motor.

There's a link to buy the complete hardware kit in the summary.

I understand but I have all the other parts already laying around except the motor and hinges. I can totally understand that you want to earn some cash from your exeptional models that you give out for free but for me it would be a bit strange to shell out $80 just for a motor that is probably just a few bucks.
I will figure it out myself and find something suitable. Thank you again for sharing these awesome projects!

do you need supports for this?

all notes about printing the parts are listed on the printed parts list.

Thank you eric for the awesome design. In the process of sizing everything down to a working 1/10 scale. This one is a little more difficult then the other motors. Here is a teaser. The turbo is fully functioning.

Are you going to share the files when you are done scaling it down b/c that would be awesome in a rc car.
Thank you

What Apple Green filament did you use? I hope I'm correct in assuming this is all PLA.

I'm printing this right now. Do you have a link for the engine stand?

I updated the engine stand recently. Right now only the files are uploaded. Working on getting the instructions up. Hardware kits for the stand should be available soon too.

Also dose it come with the light kit? That is just amazing!!!!!!!!!!!!

what is all included in the hardware kit the site dose not really say?
Thank you

Sorry, I found it. :)

Nice job as usual.But the compressor wheel modell seems to be broken ,slic3r dont print it at all and simplify3d does miss some part of it.

I updated the file. See if that works

Where can i get the motor and speed controller? Thanks

This is absolutely amazing. I'm gearing up to make this but in reviewing the assembly instructions I see that the coil winding section is unfinished. Will you be providing instructions for that part of the build? Thank you so much!

The coil winding instructions as well as the assembly of the electronics are in the form of a video. The links are at the beginning of the instructions.

Fantastic. I saw this in a background video with you at makerfaire and couldn't wait for it. All bits are now ordered for it and start printing.

Eric, another beautiful model, thank you. I see that you use SolidWorks, when you do your SaveAs STL if you change your Angle Tolerance to 2 deg, it eliminates almost all faceting on curved surfaces. I think the default is 5 or 10 degrees and these parts look like they used the default export setting. Once changed, SW will remember that setting for all future STL exports. Going down further to 1 deg doubles file sizes and doesn't seem to yield a quality improvement. FWIW. Cheers, c.

Another great piece of work, cheers

Incredible! Thank you for sharing.

Mastery. This and the 22RE, you definitely have good taste in vehicles.

Just saw the video on Youtube, thought I'd come over and, Freaking nice touch, with the LED's simulating the processes.
You know this is a product I'll have to do, at some point.

Thank You, Awesome work.