1/32 Wasp Junior engine

[daveculp]

I started work on a 3D printed Wasp Junior engine, and this topic will give me space to write about the challenges involved.  I've seen a lot of nicely done radial engines here, usually involving added wiring detail, so I started this project out of curiosity.  Could I 3D print the whole engine, including the wiring?

 

This engine project isn't designed to fit a particular airplane, which means the mounting system and exhaust system will need to be adjusted to fit.  My goal is to build the engine with "short stack" exhausts and no mounting ring.  Here are some repeat photos from the original Wasp Jr. thread.

 

 

First, a CAD rendering of the forward engine block.  I'm using AC3D for the CAD.

 

 

 

Next, a print of the block and one cylinder.  This was the first attempt.  I fixed a couple things and printed again.

 

 

 

Here is a screenshot of the slicing step, using Chitubox 1.91 for slicing.  I only had to design the cylinder once and after adding supports I cloned it eight more times.

 

 

 

 

Here is the support system I'm using for the ignition ring and wires.  This is by far the most fragile shape I've printed.  I ruined the first one while trying to remove the supports, so for this attempt I moved the supports a bit to make them easier to remove later.

 

 

 

Here is one of the ignition ring parts after printing.  I removed most of the supports while the part was still pliable, then I put them in the curing box for the final curing step.

 

 

 

 

 

Here's a recap of the equipment I'm using:

 

CAD:               AC3D

Slicer:             Chitubox 1.91

Printer:           Elegoo Mars 2 Pro

Resin:             Elegoo standard grey

 

-- Dave

[KiwiZac]

That's a fantastic idea Dave, bravo! Unfortunately none of the images are showing for me.

 

Would you consider doing an Allison V-1710 in 1/32? I've learned I'm not the only one wanting one for the P-40E and onward.

[denders]

Right click on the image name and open in another tab.

[daveculp]

Your browser is blocking them.  You could try a different browser - there are several that won't block them.  I have success with Brave, Dissenter and Firefox here.  Chromium (Chrome) blocks them.

 

Nobody makes an Allison V1710?  I'll take a look when I can.

 

 

1 hour ago, KiwiZac said:

That's a fantastic idea Dave, bravo! Unfortunately none of the images are showing for me.

 

Would you consider doing an Allison V-1710 in 1/32? I've learned I'm not the only one wanting one for the P-40E and onward.

 

[brahman104]

Cool project Dave! I tried printing Fancherello's incredible R-2800 and couldn't get the ignition ring to print successfully. Looks like yours has come out okay. I guess I've still got a lot to learn on the correct placement of supports.

 

Very nice work so far. I'd like to do a RR Griffon one day like this too.

 

Craig

[daveculp]

Craig, here's what worked for me:

 

1)  Only use small supports.

2)  Tilt the part 45 degrees and put the "ugly side down", i.e the side that will be less visible 

3)  Don't put supports inside the narrow crook (where the wire connects to the plug).  Support this from the side only.  There is not enough room there for the support, so it will fuse with the part and can't be removed later without breaking the part.

4)  Clean after printing with IPA.  Use swishing and soaking, no brushing.

5)  Snip off most of the supports while the part is still pliable.  Leave some support structure and base on for now so you'll have something to grab hold of.

6)  Cure normally.

7)  Do all the final snipping and sanding you can before removing remaining supports and base.  Then finish snipping and sanding.

 

[brahman104]

Thanks Dave! Always learning

 

Craig

[KiwiZac]

Thanks Maru! And all the best Dave, I'm very excited to see your progress (and will grab another browser do view it!). Your work so far looks fantastic!

Edited March 21, 2022 by KiwiZac

[JimRice]

I’m very interested in this.  I need a couple for Stearman dusters I’m wanting to build. 

[daveculp]

4 hours ago, JimRice said:

I’m very interested in this.  I need a couple for Stearman dusters I’m wanting to build. 

 

I've been thinking about the process of distributing these 3D printed parts.  The best way (I think) is for me to post the CAD files and let people print their own parts.  If I print the parts there is a problem.  First problem is that the post-printing steps are labor intensive - so much so that it really could never be viable to produce ready-to-assemble parts this way.  If I skip the post-processing steps and send the uncured parts, then the modeler will have to do the final curing, snipping and sanding, and he'll have to do this in the right order and probably without the benefit of a curing box.  I could cure the parts while still on the supports, but this just makes the snipping/sanding step harder for the modeler.  Either way if he breaks a part during this process, which in the case of this Wasp Jr. model is probable, then somebody's on the hook for a replacement part.

 

Of course providing the CAD files only comes with it's own problems.  It's up to the modeler then to place the supports in a slicer.  This takes some experience and trial-and-error.

 

I could provide an already sliced file, but then that's specific to a printer model and resin.

 

-- Dave

[daveculp]

All parts are printed and now is time for painting.  Here are the parts getting painted before final assembly.  I've attached the supercharger to the back of the crankcase, and I've attached the short stack exhausts to each cylinder (one shown).

 

 

 

 

I was planning on printing a collet to hold the prop shaft in place, but I found some styrene tubes with just the right size so I cut off a small piece.

 

The pushrod covers are slightly different for the exhaust side versus intake side.  I've printed them in two separate groups so I can keep them from mixing.  I also left them attached to the bottom supports and skate to make them easier to handle while I clean them up and paint them.

 

I realized (thankfully soon enough) that I'll have to place the rear ignition wires in position before I glue on the cylinders.  Disaster averted

 

 

[KiwiZac]

On 3/22/2022 at 7:45 AM, daveculp said:

 

I've been thinking about the process of distributing these 3D printed parts.  The best way (I think) is for me to post the CAD files and let people print their own parts.  If I print the parts there is a problem.  [...] Of course providing the CAD files only comes with it's own problems.  It's up to the modeler then to place the supports in a slicer.  This takes some experience and trial-and-error.

I'm fortunate to have several friends with CAD experience and access to printers, so I'd be very happy with the file-only option. You're doing wonderful work, Dave!

[KiwiZac]

On 3/24/2022 at 3:50 AM, MARU5137 said:

for KiwiZac....

http://www.daveshangar.org/photos/wasp-parts.jpg

 

In case you could not see the latest of Daves super stuff.

 

I've downloaded Firefox especially to follow along!

[daveculp]

The build is progressing.  Painting is not my forte, but it seems to be coming along OK.  I used MRP-104 Light Grey, FS 36622, which looks like beige to me, for the crank case color.  The rest is painted with Testors enamels and washed with Vallejo black model wash.

 

First I placed the rear ignition ring in place but didn't glue it.

 

 

 

 

... then glued on the top cylinder.

 

 

 

 

Hopefully the rest of the cylinders will fit without much bother - we'll see

 

 

An aside on printing the cylinders.  Because of all the surface detail on the part the best place to put the supports is on the bottom, which will never be seen.  Here's a screen shot from the slicer app showing some of the supports - in this case I'm showing just the bottom supports.  For clarity I've left off some light supports that I added elsewhere on the part because of some overhangs.

 

 

 

 

With resin printing the part is printed upside-down.  Because of this there will be some extra material at the base.  This is because liquid resin pools here among the forest of supports.  The extra material is located here:

 

 

 

 

This causes the base of the part to be a bit curved, so you need to manually shave/sand this extra material off to make the base flat.  Tilting the part before adding the supports can help with this, but can lead to other problems.  For instance it may require the addition of heavier side supports to keep the part in position during printing, and this will leave marks on the part.  It can also leave some concentric rings on the top of the curved surfaces (see my second photo of this thread - you can see that I printed the crank case at a 45 degree angle).

 

-- Dave

[denders]

Looks fantastic!