Truman Thomas 4-In-1 Engine

 Finished my first model engine!

Attached are photos of my 4 in 1 vacuum engine. Runs great and learned an incredible amount in the process. Probably going for a Stirling next.

3PI-X High Voltage Protection Capacitors

As mentioned in a prior 3PI-X post, the addition of two capacitors help stabilize the 555 IC from any coil high voltage feedback.  

1)  Add a .01uF capacitor (10nJ100) at I11-I14 right behind block B2 (pointed to by the longer red line in the photo).  There is barely enough space and this must be installed before block B2. If B2 is already installed, try installing it on the bottom side of the PCB (but beware the "letter" coordinates are different on the bottom side of the PCB, B11-B14 to be exact)

2) Add a .1uF capacitor (.1J63) to block B1 positions 1 and 2 (pointed to by the shorter red line in the photo).  See the original instructions of you are not sure of the location of the two positions.

As a side benefit, I have discovered that the 3PI-X will operate at 12 volts with the addition of these capacitors.  I have not tested the longevity of the module at 12 volts, so proceed at your own risk!  Overheating is much less likely if the auto-timeout jumper is enabled (attached), but regardless, check if any components are getting warm or hot every minute until you're confident it's running cool.

Jeff Smith's Farmboy #1099 (so far)

 

3PI-X Improvement Tip

Since I developed the 3PI ignition module in 2024, I have sold 2 or 3 dozen kits and have not had any reports of any issues until I received the following e-mail from Justin Snyder on Jan 25, 2026.  I have not had a chance to test his changes (but will soon) but I have no reason to doubt his results.  See his email is below:

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Hello,

I purchased the 3PI-X ignition module awhile back. I had a few issues getting it working reliably. It really messed with me debugging my new hit and miss model engine. I went through several 555 ICs and a couple 2N4124 transistors.

I was about to email you for troubleshooting tips but after a lot of research and reading about similar circuits, I believe the issue was stray voltage created by the coil. Adding extra grounding was not enough.  To fix the issue, I added the optional 0.01uF cap to pin 5 of the 555 chip as well as adding a 0.1uF bypass capacitor between pin 8 (VCC) of the 555 and ground. So far no more blown 555 chips and reliable performance. These should be part of the circuit as added protections.

I hope this helps others so they don't have to go through what I did to get it working reliably.

Thank you,

Justin Snyder

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Thanks for sharing Justin!

Richard Daoust's Farmboy# 1063

Dan Allen's Farmboy #818

 

John Laudano's Carburetor

 Thank you again. I built one. Next will be the rest of the engine.

A few photos are attached.

John

On Monday, October 7, 2024 at 09:01:57 AM EDT, John Laudano <john.laudano@att.net> wrote:

Thank you Allen. 

the world misses guys like your dad.

John