Webster Engine Works Single Cylinder 4 Stroke Gas Engine

Introduction / Background:

I am a mechanical designer / 3D CAD operator by trade and used to design parts and assemblies for a shop ran by some of the nation's best machinists and metalworkers. Since I'm generally a hands-on, do-it-yourselfer, gear-head kinda guy, I've always wanted to try my hand at metalworking, and more specifically, the building of model internal combustion engines. Through a discussion with one of the guys in the shop, I learned of the annual Cabin Fever Expo in York, PA. I attended the expo in January 2003 and even though I was still in the information gathering stage, I picked up a set of plans for Jerry Howell's "Powerhouse" gas engine because I liked the way it sounded when running, and it was relatively simple for the beginner to build. Shortly after I learned of Hamilton Upshur's wonderfully simplistic "Farm Engine" in Strictly IC magazine and ordered the plans. I also spent a lot if time at Ron's Model Engineering and Model IC Engine Projects and ordered plans for "Midge" - a small diesel model airplane engine. I used Solidworks 3D modeling software to model nearly every plan I came across, and let me tell you, between the internet, books, and magazines, I found multitudes of them!

It's pretty hard to be a machinist without any machine tools, so in April, 2003 I purchased a Smithy Granite 1324 3-in-1 lathe-mill-drill. (The purists frown on these types of 3-in-1 machines, but I felt it was justifiable for my soon to be small shop.) I spent many hours making chips and even made a few working steam and stirling engines to get my feet wet.

Although the designs that I had acquired were well executed examples of model IC engines, I felt that I needed something simpler. "Borrowing" ideas from the above mentioned engines, and also Philip Duclos' Odds-n-Ends, I designed an engine which, even I - a complete novice, could build with the tools and most of the materials that I had on hand.

(Clicking on any photo will bring up a larger version.)

Specifications:

Displacement: .75 c.i. / 12 cc
Bore: 7/8" / 22.2 mm
Stroke: 1 1/4" / 31.8 mm
RPM: 1000 - 5000 RPM (measured)
Spark ignition w/ 12 V high tension coil, points and condenser.
Atmospheric intake valve (poppet valve), and cam/rocker operated exhaust valve.
Throttle governed with an O.S. radio control car engine carburetor (.12 c.i. size).

Some of the main design considerations were:

General ease of construction with minimal tooling (basic lathe and mill work).
No fancy radiuses, spokes or bolt patterns requiring the use of a rotary table.
"Smallish" proportions to limit material costs.
Limited number of parts for speed of construction.
Availability of gears, bearings and other components.

Design of this engine was started around the middle of May '03 and it was only a couple of weeks before I was making chips. There were a few bumps in the road along the way, mostly because of intimidation (which of course caused me to loose momentum), but in January '04 I fired 'er for the first time. Since then, I have run nearly a gallon of fuel through it and it's still going strong. It usually starts on the first flip and has a very pleasing sound. For fun, I sometimes hook a small generator to it to power a few Christmas tree lights. I won't bore you with the laying out, set-up and machining operations (not that I really knew what I was doing), but I'll be happy to share some pictures, sounds, and videos taken along the way.


This shot shows the valve block, head, and venturi / needle valve. I later went with a carburetor from a radio control car engine because it gave me much better speed and mixture control. The spark plug hole was tapped 1/4" X 32 tpi so that I could use either glow or more traditionally, spark ignition. The valve blocks and engine frame were made from 6061-T6 aluminum, the valve guides and venturi from brass (although bronze would have been a better choice for the valve guides).		Here we see a completed piston, rocker arm, and the start of the cylinder. Boring and honing the cylinder was one of my major stumbling blocks, but it turned out to be not much of an issue. I used 12L14 leaded steel for the cylinder (which cut like butter) and 6061-T6 for the piston. The piston rings came from Otto Gas Engine Works, and the ball bearings & gears from Stock Drive Products. Hidden behind the large brass gear is the exhaust cam.


Just a close-up of the piston showing the rod cut out and the two 4-40 tapped holes for the wrist pin set screws. Notice the small brass tube? At the end of the piston's stroke, this tube aligns with the cylinder oiler and supplies lubrication to the wrist pin - this was done on full-size, antique, gas engines, and it works in smaller scale too.		This picture kind of gives you a sense of scale. The rod, made from more 6061-T6, is 3.063" between centers. Profiling of the rod ends was done without the aid of a rotary table. Basically the end to be profiled was attached to a snug fitting, vertical pivot on the milling machine and the rod swung by hand against the side of a running end mill. (Needless to say, this is rod #2.) Check this link for a better explanation and even a nice photo. The wrist pin is .188", drilled through .094" and both ends of the rod are bronze bushed.


Here's a 3D rendering that I did in Solidworks showing the valve-train detail. As mentioned earlier, the intake valve (on top) is actuated by the vacuum created by the piston on it's outward stroke. Compression, combustion, and subsequent exhaust pressure keeps the valve closed during their respective cycles. The exhaust valve is operated by the steel cam attached to the brass gear and is timed to open on the exhaust about 15 degrees before BDC and to close the exhaust valve a few degrees before TDC.		OK, here's a semi-exploded view of all of the parts. Just where do you get a chunk of cast iron large and cheap enough to make a flywheel this size (3.75" dia.)? Well Walmart of course... in the sporting goods section, disguised as a dumbbell. One word of caution though, it's a pretty cheap casting that has a few voids - luckily none of them caused any problems though. The crankshaft started out as a piece of CRS flatbar 1.5" X .5" X 5" and both shaft and crank pin were turned as one piece, between centers.


"It lives, I have created life!" What you see here is the engine just after it's first run on model airplane fuel (10% nitromethane, 18% oil, balance methanol) and glow ignition. The first few runs were pretty short as the piston to cylinder fit was still fairly tight, and the engine would slow to a stop as the aluminum piston heated and expanded in the bore. Check out the oily mess that glow-fuel leaves behind... great for breaking-in a new engine, but quite the chore to clean up. The date was January 3rd, 2004.		Another shot, taken the same day. Notice the small pits in the depressed section of the flywheel, these are some of the voids that I mentioned above. Also notice the small section of broken roll pin in the right foreground. This was the roll pin that held the flywheel to the crankshaft, but it had sheared while running. Even though I had planned on using two 3/32" cross-drilled roll pins to attach the flywheel, in my haste to get the engine running, I only took the time to affix one. Lesson learned. The engine now uses two roll pins (one each on opposite sides of the flywheel) and they have held up fine.


Here were are running on gas and spark ignition. Originally, I was using a 1/4" X 32 tpi spark plug, but it was too easy to foul, too hard to get, and too darned expensive (~$15) to replace. I've drilled and retapped the head for a 10mm NGK CM-6 spark plug. With it's larger electrode and insulator it's pretty hard to foul and only $3 to replace at my local Honda motorcycle dealer. Photo was taken on July 12th, 2004 and at that time, nearly a gallon of fuel has been through the engine. (At an average of 14 minutes per ounce, that's about 28 hours of run time.)		In this photo you can see the RC carb retrofit and the NGK CM-6 spark plug (10mm X 1mm pitch). I run this engine on straight Ozark Trails lantern fuel, which is the Walmart brand of the popular Coleman fuel - only a dollar a gallon cheaper. I use regular 5w-30 motor oil in the cylinder oiler. I have also tried running the engine on straight gasoline, but since it is less refined than the lantern fuel, it just plain stinks when running - the lantern fuel almost has a pleasing smell. Anyone who has been to Cabin Fever knows what I'm talking about. (Or is that just me?)


Just a right side view showing the general arrangement and the spot where I ran an end mill into the cylinder as I was spot-facing for the oiler threads. (D-Oh!) The base plate was sawed out of 3/8" thick plate of anodized aluminum - not pretty, but it works. (I picked up close to 150 lbs of aluminum plate and bar from a farm auction for $15 - just one of those rare days when I was in the right place at the right time). Oh yea, the fuel tank was soldered up from brass tube and bar stock, holds about an ounce, and I'm kinda happy with the way it turned out.		Left side view showing the purchased grease cup for crank pin lubrication. You unscrew the knurled cap, pack it full of grease, then screw it back onto the "cup", forcing grease through a small hole in the crank pin, lubricating the pin and bearing. Just give it a quarter turn or so before each time you start it. (Hey, it's how they used to do it in the good ole days.) See the curved slot on the lower right of the engine frame? That was to be used for the adjustable electronic ignition, but I decided it was easier to stick on a set of old fashioned ignition points than to fuss with hall effect ICs and driver circuits. Breaker points are much more forgiving of "user error" than ICs!


Here's a close-up of the valve block showing the springs, valves, valve guides, rocker arm, and the RC carb adapter. The valves are mild steel, with .093" stems and .250" heads. The valve stems are cross-drilled .040 for the spring retainer pins. The intake and exhaust ports are .188". Also, the carb has a rather diminutive bore of about .166", which is fine for an engine such as this. Oh, I almost forgot to mention, the intake valve spring is relatively light to allow it to be self-operating. When you crank the engine over by hand, you should hear a "snort" as the intake valve opens and draws air through the carb.		Anybody recognize these? I had read that points for any early Mopar product would work nicely for model engines, so I walked into my local auto parts store and asked for a set of points and condenser for a 1969 Dodge Charger, 383, 4 bbl... It wouldn't have been too cool to ask for something from a Dodge Volare'! The kid behind the counter looked at me kinda funny and said, "Oh, I won't have anything like that." I pressured him to look anyway, and whattaya know... he had 'em in stock. (The cost for both were around $10 US.)


Just a rear view to show the cam gears. So what lubricates these babies? Mostly unburned oil from the exhaust - you know, whatever blows by the rings coming from the cylinder lubricator. If the gears look a little dry, I'll put a drop or two of oil on 'em. Yea, I know, it's crude, but it works... (Looks like it's time to fill the grease cup again, too.)		And a view to show the back of the cylinder - I kinda like the perspective of this shot. If you look closely at the end of the rod, you can see the hole in the rod that receives oil from the cylinder lubricator above it. That's grease splattered onto the back of the piston from the crank pin grease cup.

Finally, here is a video and a few sounds of the engine running:

Start-Up (VIDEO)

Idle

Revving

Driving a load

Update! 02/02/05 Another Webster Runs! I received the following video from a builder in California who has just fired his engine for the first time. (This would be the second running "Webster" known to exist). Click here to see his engine in action. Way to go Rich!

Update! 03/02/05 Another Webster Runs - also in California! Phil started building his "Webster" the day after Christmas 2004, and had it running three weeks ago (that's an amazing build time of 5-6 weeks folks). He has also added a slick adjustable breaker plate and counterbalanced crankshaft. Click here for a video of his engine, and check out that looooow idle speed. Here's to a job well done!

Update! 04/22/05 - No one else has come forward with a completed engine (but I know of a few that are nearing completion). So while I have your attention, I'd like to share one of my other designs with you - it's a .056 cubic inch, compression ignition, 2-cycle, model airplane engine. Details can be found here, on the "The Next Generation EZE" page. If you're not ready to take on a project the size of the Webster 4-cycle, maybe a smaller, simpler engine is right up your alley - check it out. (Don't get your hopes up though, I'm not offering free plans for this one!) Oh, while I'm thinking of it, if you maintain a list of links on your web page, feel free to add either of my pages!

Update! 10/23/05 - Another Webster Runs - this one in the UK! How's this for inspiration - Warren built his Webster in an incredible two weeks! OK, so he "cheated" and used his home shop CNC, but this still warrants big praise. Currently he's running his engine on glow fuel but plans to switch it over to gas soon. Here's a short video clip. Congratulations Warren!

Update! 11/21/05 - Bob P. checks in with his running Webster. Unfortunately I don't have any pictures or video to share - Bob, if you're reading this, send a few pics or a video so we can brag about it here!

Update! 01/01/06 - Peter from Slovakia proudly writes to say that he's completed and ran his Webster at 11:44 pm on New Years Eve! Peter has done a fantastic job on his engine with neat additions such as a ball bearing supported cam, a ball bearing on the big end of the cod rod, a roller tipped rocker arm, large-press-on cooling fins, a larger flywheel, an adjustable breaker plate, a removable carb adapter, AND on top of this, he cut his own gears. He also reports that his engine is a "smooth runner" and with the aforementioned mods it's no wonder! Also, Peter frequently displays his engine at antique steam and gas engine shows and always draws quite a crowd!

Update! 03/04/06 - Eric in Canada has completed his Webster and it's truly unique. Sporting mods like a curved spoke flywheel, fully radiused corners, counterweighted crank, oversized ball bearings, shop-made gears and a Viton O-ring installed on the piston instead of cast iron rings, Eric's engine is a real beauty. One thing though - Eric must have been looking at the plans from the wrong side because his version is a mirror image of all the other Websters out there (don't worry Eric, your secret's safe with me)! Have a look at this "one of a kind" here then come back and check out his video (9 Mb offsite).

Update! 06/02/06 - John from western Australia writes with details on his engine. Let me just say that this one's built like a tank! With 12mm thick marine grade aluminum alloy frame pieces, stainless steel valves, sealed ball bearings on every rotating bit, a fabricated / silver soldered crankshaft, and a shop-cast bronze flywheel, this one should last a lifetime. Some other interesting (if not clever) details are the bronze crank gear (sourced from a photocopier) mated to the plastic cam gear which John bought from his local hobby shop. While John was perusing the store, he picked up a piston / ring / wrist pin combo (from a .60-.90 size RC aero engine presumably) and is using them in his engine. Now that's thinking! You can have a peek at John's engine here.

Update! 01/01/07 - Julian from the UK checks in with another New Years Day Baby. Like many of us with "household duties" Julian didn't have a whole lot of time to build his engine, but with with a few spare evenings and time around the holidays, he managed to turn out a fine example of the engine. Some modifications & deviations worth noting are the built-up spoked flywheel, two-piece valve block, silver soldered crankshaft, lapped cast iron cylinder/piston combo (no rings), stainless steel valves, micro-switch ignition, and ball bearings used throughout (most of which were sourced from old hard drives). Oh, and I almost forgot to mention Julian made his own throttling carburetor by using Nemett's design in a recent Model Engineer article. The engine starts and throttles well, but as Julian reports he'll need to install a muffler of sorts if he wishes to keep the peace around the house. Don't worry Julian, you're not the only one with that problem!

Update! 01/06/07 - Due to popular request, I've updated the plans link to include fuel tank fabrication details.

Update! 05/26/08 - We have two new engines to report: The first is from Bill H. in MI, USA. Bill had little trouble with the build of his engine and turned out a beautiful example of The Webster, complete with a real honest-to-goodness spoked flywheel. The "running" part of the build however, was a bit elusive. Bill and I shared many e-mails back and forth and although everything appeared to check out, we couldn't get it to run for much more than a couple of short bursts. Sadly Bill ran out of time and patience for his project and shelved it for nearly two years, but in February of this year Bill excitedly checked in with good news - his Webster now runs! It turns out that the intake valve wasn't sealing as good as it could have, and after recutting and lapping the valve seat all is good. Persistence pays off and Bill has a runner -way to go!

The second Webster to surface this year is a little unique as it's the first water cooled Webster known to exist. That's right, Jens S. from Norway added a water jacket, a wick lubricator, a balanced crankshaft, a massive brass flywheel and a carburetor of his own design. He also made his own piston rings using Professor Chaddock's method and even went as far as to intentionally produce a slightly tapered piston to reduce running friction. Wow, talk about taking a scientific approach to engine building! Video of Jens' engine can be found here. (A water cooled Webster... how cool is that?)

Conclusion:

I'm sure a lot of people reading this right now are cringing at the way I did some things. Remember, I wanted an easy and quick to build engine requiring minimal tooling and materials. I think anyone who has built a couple of successful steam / stirling engines and has an idea of which fits are important could build one.

Pros:

Quick, inexpensive, and relatively easy to build.
No castings required.
Minimal tooling required.
Uses many easy to find items ie: gears, bearing and ignition parts.
Very forgiving design - no super-critical dimensions.
Can actually drive a useful load.
Easy speed control, no small and finicky governor parts to be made.

Cons:

Limited run time due to inadequate cooling, but I kinda figured this going into it. This engine was never meant to run 24/7, just the occasional smoke, fire, and noise show for friends and family... well, OK, me. Needs more and / or larger cooling fins, a fan, or possibly a water jacket on the cylinder. Not a major issue, and certainly one that's easily resolved by thermally isolating the carb.
Possibly needs thinner piston rings to reduce drag and friction (1/16" -vs- 3/32").
Messy (but effective) lubrication scheme.

This has been a very fun and ultimately a very satisfying project for me. I get the biggest kick out of it every time I fire it up. Sure it's ugly and has a few bugs, but for a first I.C. engine project, I don't think it's so bad. If someone were interested in building one, I'd have a few suggestions and changes to make, but even "as is", it has satisfied all of my design goals perfectly.

OK, if you've made it this far, (obviously I haven't bored you to death), and would like to discuss this project in more detail, drop me a line at: "webster_engines -at- comcast.net" and by all means, if you download plans and decide to build one - let me know!!!!

For PDF plans, click here!
(DXF or DWG plans available upon request.)

Thanks for stopping by!

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