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 (eXperimental version) 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

Jon Zwicker's Farmboy

 Hello Allen

I just wanted to let you know that I finished my Farm Boy No. 1019 , this is the first engine I’ve ever built and I really enjoyed it.  Your prints are excellent.  I was a pattern maker for 30 years and it seems that there were always a few missing dimensions.  Your prints were very complete !

I thought you might like to see some pictures.  I haven’t painted it yet and maybe I won’t, having too much fun just watching it run!

I see in one of the photos of someone else’s engine that they built they had an oval Farm Boy plate made for the side of it.  Any idea where it could possibly get something similar ?

Thanks Again

Jon

Alan Gorlick's Farmboy (and plan changes/corrections)

 Hello Allen,

Just a note to let you know that my FarmBoy engine, Serial # 1033 is finished and running well. I downloaded the plans in March this year and worked on it steadily since then. I used the buzz coil ignition with spark saver option, a standard length Rexcel plug and a 4 AA battery pack. I did depart from the plans a bit to build it as a six bolt head instead of four, just to put my own mark on the model.

The plans are excellent but I can confirm there are two errors on sheet 3. As identified by Andrew Whales in his build series on YouTube, the horizontal spacing between the crankshaft and cam shaft is 1.031" for 48DP gears, not 1.026" shown on the drawing. The other error is that the 0.325" dimension for the cam mounting pad thickness on the Rearward View should be 0.355" as confirmed by the correct  0.105" (plus 0.25") dimension for the pad shown on the Bottom View.

The engine started and ran on the very first attempt, startling me completely! The only adjustments I made was experimenting with governor spring force, initially using a rubber band to get a feel for the right tension and then making the light spring shown in the attached video link which is a short clip of the fourth run. I've raised the speed slightly with the adjusting screw in the catch lever and finished the mounting bolts with nyloc nuts etc since that clip was filmed. The only things left are the crank bearing oil cups and deciding on a paint scheme or maybe leaving it natural.

Thanks again for the quality products,

Regards

Alan Gorlick

Qld, Australia

https://www.icloud.com/photos/#/icloudlinks/09eIMdROuPz9pF8GblRNJj0Og/0

Indiana Engine Show - Oct 12-13, 2024

 

V4 Construction Links and Parts List

 

PowerHouse - Page 5 Correction

It has come to my attention that there appears to be a dimensional error on page 5 of the Powerhouse plans. On "Frame Side View" (upper left), the dimension of .281 for the distance from the edge of the frame to the location of the push rod bracket holes, should be ~ .210 to .213 instead.  If .281 is used, then the leftmost pushrod bracket located 2.156" away will be too close to the cam gear.

Many thanks to Jay Bolyard and his son Erik who caught this.  

I'm very surprised that this has not been brought to my (or Dad's) attention until now as the plans have been around since 2001!

Regards,

Allen

Kees Bijker's 3-D Printed V4 Update

Hello Allen,

I wish you and all your loved ones a Merry Christmas and a Happy New Year. This is the last update of 2023 of my 3d printable Howell V four. Nearly done and still so much to do. Got 99% of the parts printed now and just need to figure out some minor improvements for printing and fitting. Then it is back to the printer and printing all the final versions and creating a bom list and build instructions. This will be 2024 I am sure. The camshafts prove difficult and I have printed 4 different iterations without luck so far. This last one has to be the one. Going to print it with a much smaller nozzle and lower speeds for high definition. Should do the trick. Enjoy the festivities and hope to hear from you either this year, if not next.

Kind regards, 

Kees.

Jan 10, 2024: Here's a link to the completed project:
https://www.printables.com/model/714791-working-model-of-the-howell-v-four-engine

Alan Gorlick's BuzzCoil Review and Comments

 Hi

Just a note to let you know the "buzz coil" ignition module kit, spark plug & hall effect sensor are installed and working well on a hit & miss engine that I have just finished, it's based on a David Kerzel design. 

I am using a 2mm x 1mm magnet set in the cam gear at 0.5" radius which works very well at the low speed of this engine. The hall effect sensor is epoxied onto an arm that can pivot around the cam gear shaft as suggested in your notes. That change to Mr Kerzel's design made setting the ignition timing extremely simple and precise. The coil is a universal ATV coil and is the only thing in the ignition system that has caused any problems. The first one had a loose primary terminal.

I did successfully bench test the spark saver circuit with a second hall effect sensor but have only installed the single sensor circuit as battery capacity has not been an issue. I am using a 6V 4.5ah rechargeable lead acid battery (AGM type) which I haven't had to recharge yet and cost very little more than a pack of 4 AA energisers and case.

One low cost change that I suggest you could make to your kit is to use an 8 pin IC socket that is soldered onto the PCB first and the 555 Timer IC just clips into that socket after everything else is installed. It removes any risk of exposing the 555 to the heat of soldering and allows easy replacement of the timer if ever required.

Thanks for the quality product,

Regards

Alan Gorlick

Bundaberg, Queensland, Australia

https://share.icloud.com/photos/0d5FHJTjAPdnaYQS7rdgz797A
https://share.icloud.com/photos/0b5nNV26JYIzEbaKk6JayRknw

New show near Ft Wayne on Oct 14th!

 

Anthony Holden's Farmboy #673

 

Mark Journee's Farmboy #995

 Hello Allen 

Thanks again for the drawings i have finished the engine. it was a great project to make here are some pictures of the farmboy #995.

kind regards.

mark journee from the netherlands

Mark Journee's Farmboy #995 (so far)

 Hello Allen 

First of all thank you very much for the plans!   I'm almost in love with making the parts.  I've made some progress since I have some free time at the moment. I make the farm boy a little bit different from the original but here are some pictures of the engine:

Kees Bijker's Flathead V8 vs Howell V4

 Hi Allen,

A "little" comparison with my previous Ford V8 flathead 1:3 model I made.

Your father's V4 is really tiny.

I am hoping that the Howell Vfour will end up looking just as nice. (Don't look at the engine stand yet, that was a fail to be rectified soon).

Take care.

Kees

Kees Bijker's 3D printed V4

 Kornelis Bijker from The Netherlands is building a 3D printed version of Dad's V4 engine.  Here's his latest update:

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"Hello Allen,

It is quite the trip I have to say. I think I have 95%+ of all the parts modeled by now, and started modifying the fits, fasteners and certain details for 3d printing.

Things like the con rods I cannot print in one piece, so I had to modify them to have a bearing cap, a very small bearing cap. The miniature bearings are 2.5 mm wide so the bolts holding them on will be just M1.4, the tiniest I have ever used.

Most of the original designs I try to keep, but some parts are simply to difficult to print like that.

The guts of the engine will have all working mechanics, like crank, pistons, cams and timing gears, lifters and moving pulleys.

But internals of pumps and ignition will not have moving mechanics. Simply too small and too detailed for FDM printing to work well. And in a plastic model without petrol combustion, I do not need cooling or oil anyway.

Still not sure where I will build in the electrical motor. If not inside the crank case I might have to "invent" some fictional starter motor. Maybe a bell-house with a large gear instead of the flywheel. Not decided yet.

But as of now the fasteners have been modified to metric, so have most of the bearings. They are easier to find here then the ANSI style and imperial bearings.

I also have started printing things, mostly as a test to help decide tolerances and such.

I was quite happy that the fan shroud printed as well as it did. Also happy how the radiator insert came out, you can actually see through it.

Some things still to do are the throttle linkages, and yes the distributor will advance as well. I also will attempt to connect the speed potentiometer with the throttle link so that the engine will respond to the throttle. The sound is another story."

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The first 4 images are the 3D software renditions of the V4, and the last three are actual 3D printed radiator parts.  Nice job Kees!  Looking forward to seeing this to completion!

March 21st Update:

Hi Allen,

Plodding on with modifications and printing and now also building.

The engine casing still needs cleaning up but I have started with the heads now. Some photos showing the tiny parts on a background of my notes for printing.

In view also the hand tools for this minuscule work. M2 hand-tap in a tap spinner and the M2 Allen key. Some photos show how the parts come off the printer. Looks a bit like an air-fix kit when they are all attached to each other. Right now printing the rocker arms and other small parts to complete the heads. I keep saying "other small parts", but to be honest all of it is small. Anyway next week I will be on holiday so no work on the engine for 2 weeks.

So far I have modified the valves to take a M3 bolt as a stem and the push rods with valve lifter to be made from a ground to shape M3 bolt as well. I am printing the clevis, as this is a really neat part that needs to look right.

Long way to go still.

Second email with more pictures and a section view of the engine to show the new valve and push-rod. setup. I have had to do away with the valve lifters and the ground down bolt head will take its place. The next email with the section view will show this