Napier Deltic Engine Model

by zefram, published

Napier Deltic Engine Model by zefram Feb 16, 2013

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Model of the cylinder layout of the Napier Deltic engine found in the Deltic class of British diesel locomotives. 3D printed in 46 parts and assembled into a working model. A stop motion video is available in the downloads.


Print all the parts and assemble, PDF instructions with pictures are provided in the downloads.

A STEP file and movie are also available in the downloads.

Part List

Stage 1

      1 x Base 1

      1 x Base 2

      1 x Base 3

Stage 2

      5 x Plain Gear

      1 x Cam Gear 1

      1 x Cam Gear 2

      1 x Cam Gear 3

      3 x Cam Gear Pin

      5 x Plain Gear Pin

      3 x Cam

Stage 3

      6 x Piston

      6 x Gudgeon Pin

      3 x Single Con Rod

      3 x Dual Con Rod

      1 x Cylinder 1-2 (I found it best to print cylinders vertically)

      1 x Cylinder 2-3

      1 x Cylinder 1-3

      3 x Cylinder Links

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Good model.

I have made a movie of this engine with 3D software CINEMA 4D.

And this is the project file including expressions to work it.

You can test it with Demo version of CINEMA 4D from MAXON website.

Good video, thanks for sharing

can u give me prt file ?thx

The STEP file is in the downloads, that is the only CAD available.


ok.thx,very like this things。

Jul 4, 2015 - Modified Jul 4, 2015

Volume in cm3 as reported by netfab for all parts here.
Some parts required repair.

File Volume Repair

Deltic_Engine_Rev_6_Cam.STL 9.12

Deltic_Engine_Rev_6_Cam_Gear_1.STL 9.93 Yes

Deltic_Engine_Rev_6_Cam_Gear_2.STL 9.92

Deltic_Engine_Rev_6_Cam_Gear_3.STL 9.9 Yes

Deltic_Engine_Rev_6_Cam_Pin.STL 2.11

Deltic_Engine_Rev_6_ConRod-_Dual.STL 3.15

Deltic_Engine_Rev_6_ConRod-_Single.STL 2.2

Deltic_Engine_Rev_6_Cylinder_1-2.STL 25.3

Deltic_Engine_Rev_6_Cylinder_1-3.STL 25.3 Yes

Deltic_Engine_Rev_6_Cylinder_2-3.STL 25.28 Yes

Deltic_Engine_Rev_6_Cylinder_Link.STL 3.14

Deltic_Engine_Rev_6_Gudgeon_Pin.STL 0.22

Deltic_Engine_Rev_6_Piston.STL 4.66

Deltic_Engine_Rev_6_Plain_Gear.STL 7.22 Yes

Deltic_Engine_Rev_6_Plain_Gear_Pin.STL 0.78

Deltic_Engine_Rev_6_Base_1.STL 57.51

Deltic_Engine_Rev_6_Base_2.STL 59.78

Deltic_Engine_Rev_6_Base_3.STL 61.1

Total Volume 316.62

I think this is just amazing! Have work to do on my printer but then...this WILL be printed. Im thinking red and white ;)

Jul 3, 2015 - Modified Jul 4, 2015

Not any smaller but mov converted to gif is here.


What would it take to get it running on compressed air?

Sealed cylinders !

really nice! i made it , i am trying to find a beautiful combination of colors.

At .47 inch (or 12mm) the repulsion force for the magnet below is only .03 lb. This force is unlikely to keep the engine rotating.

1/2" dia. x 1/16" thick
Nickel Plated
Axially Magnetized
Would one magnet (above) or thicker magnet with this diameter, glued to each piston head run the engine? Would two or more magnets glued on one piston head be needed to run the engine? How much did this engine model cost to make? Would you sell it?

We printed this on an Ultimaker 2, using CURA for slicing and Ultimaker's PLA/PHA. Worked fine - beautiful design!


  • we had to take care to reorientate the cylinders and pistons - far better to print them sitting on their ends, otherwise they don't come out very circular.

  • we printed the bases with 10% fill to save plastic - seemed fine.

  • cogs printed without a brim curled up on the cog teeth a bit - better with a brim. Definitely don't use a raft - it's hard to remove without making a mess.

  • cams needed a "support to base", which worked well. Same with cylinders, to make the protrusion work.

  • double con-rods needed a support everywhere, and were printed flat. They are pretty rough on the undersides - high friction, and need sanding down.

  • the cylinder links were best printed the other way up, so the little lugs weren't printed over space. This made them more accurate and fitted better into the cylinders.

We haven't glued any of it together because it works well without, although you have to be careful not to let the cam pins fall out! Otherwise, all settings were on CURA's defaults for Ultimaker/PLA.


I must print this, my place of work reconditions the cylinder liners for these engines.

Thank you for uploading the stop-motion video too, seeing it in motion really helps explain it.

Great model. Thanks for posting it. I can attest to the soundness of your advice that the cylinder are best printed vertically!

I've made a time lapse video and posted it on YouTube. I hope that you are happy with the attributions. If not, please let me know.


Good job, thanks for sharing the video, if you print and fit the cylinder links, they firm up the assembly and stop the cylinders wobbling. Mark

Done. To do proper justice to your design I've made another video. Available here: http://youtu.be/bYZdIxZPZ1Qhttp://youtu.be/bYZdIxZPZ1Q

Forgot all about them in the excitement of putting 99% of it together. I have already printed them so will fit today.

New video looks fantastic, good job.

Can a crank be put on to turn it?

The two gears that hang over the base work pretty well as thumbwheels

Never heard of this type of engine. Looks amazing.
great work... thanks