Thumper--a new 1 3/8" bore i.c. engine

[Brian Rupnow]

I have developed the concept and plans  for this engine over the last couple of days, under a thread titled "A different engine configuration".  Now that the plans are 95% blocked out, I am going to create this new thread dealing with the actual fabrication of the engine. You are all invited to follow along, and assuming this engine is a success, I will be selling the plans after I am finished.---Brian Rupnow

[Brian Rupnow]

Just so ya know----I'm going a bit beyond my comfort zone here. I haven't made an engine over 1" bore before. All rotating shafts will be on sealed ball bearings except the big and small end of the con rods (both of them).  I'm done with bronze bushings. The Rockerblock style is tried and proven on one of my previous builds. I will be using purchased cast iron rings (because I really suck at making them). My ignition will be the old tried and true Chrysler ignition points, and my CM6 sparkplug has a 10mm threaded end and can be purchased at an auto parts store. The cylinder will be made from grey cast iron, and virtually everything else except the shafts will be made from bar stock aluminum. The flywheels will be fabricated from mild steel, and I hope to make them using my new TIG welder that I bought this week. My ultimate goal is to build an engine powerful enough to drive my edger. A piston of 1 3/8" diameter has almost twice the surface area that a 1" diameter piston has.

[Art K]

Brian,
This should be an interesting build, I will be following along. This is looking to be a very different configuration and begs the question whats next after this? A deltic like Napier's
Art

[Brian Rupnow]

This morning's work was to add in all the other things you need to have with an i.c. engine, namely the gas tank and a way to support it, some shafts, and a whole bunch of drilled and tapped holes with matching counterbored holes. There are more elegant ways to support a gas tank, but this is simple and gives you the capability of raising or lowering the gas tank. (which can have an effect on the way the engine runs).

[cnr6400]

Just food for thought - if designing an IC engine for best power per cc, breathing and gas flow are very important. Small utility motorcycle makers have been optimizing power for years. There are some common elements in these types of 2 valve 4 stroke air cooled workhorse engines that deliver high power and extreme reliability, as follows:

1. biggest valves possible, inlet should be larger than exhaust if possible
2. hemispherical (or nearly hemispherical) cyl head and domed piston
3. inlet duct and carburetor are large and not restricted, and proportional to inlet valve
4. exhaust duct proportional to ex valve, and not restricted
5. electronic timing and high energy coil
6. sparkplug location in inlet flow's swirl path
7. compression ratio around 7:1 for pump gas

If you include some or all of these elements in your new engine design you will likely see a big power increase over hit and miss style engine designs. Pic of the head out of a hopped up utility motorbike engine is attached.

[Brian Rupnow]

Hi CNR6400--I am going to the larger cylinder. I am also going to a larger valve. I'm going up from 5/16" exhaust and inlet piping to 3/8". I'm going to stay with the same old combustion chamber shape in the cylinder head because with purely manual machines I can't do a hemi head.

[Jasonb]

Hemi head is doable on a manual machine, I did one about 3mths ago from barstock and have done another from castings. But then again the extra friction from the rocker beam and two conrods will likely suck up any gains in power.

The sharp elbow on the exhaust and the  relatively small bore of the muffler won't help and would be an easy mod to let the engine breathe more easily.

[Brian Rupnow]

Jason---While you were posting, I've been tweaking the models. I opened up all of the intake and exhaust pipes and elbows and took them from 5/16" to 3/8".  I could take the elbows out completely and go for a direct flow, but I like the look of it better the way it is.

[Brian Rupnow]

I've spent most of the afternoon making detail drawings of the new engine. It has snowed here for the last 48 hours and it's still snowing. It's the biggest snowstorm I've seen in years. There is a rather zen like peacefulness in making detail drawings. All of the heavy lifting gets done during the in initial design process. I have to go down street Monday and buy material. My new welder  hasn't showed up here yet, so I guess I won't see it until Monday. I've spoken to the people at Canadian Bearings in Barrie and the have the two sizes of sealed ball bearings that I need---Monday. I've spoken to the fellow who makes rings for model engines and he has the piston rings I need for $5 each, and I'll probably order them on Monday.---Monday may be a busy day!!!

[Brian Rupnow]

I just snapped this picture of my truck in the driveway--I'm waiting for the plow to come. They are calling for more snow tonight, tomorrow and tomorrow evening.

[crueby]

Gack. Close the garage door, back in the house, and stay warm!

[zeeprogrammer]

On one hand, I feel for you. On the other hand, we've had nothing here and I kind of miss it.
I was turning 7 when I experienced my first snow (we had been living in Hawaii and moved to Arkansas for a year).
I prefer the seasons rather than a season.
So far.

[Brian Rupnow]

Actually, we have had a fairly mild winter, with only about a 10" to 12" accumulation of snow on the ground for the entire year, which is below normal for Barrie. We are very much effected by the moisture coming in Of Georgian Bay, which is a very large body of water on the East side of Lake Huron, one of the great lakes. Yesterdays snowstorm dropped about a foot more of snow on us, so we just see it as a leap year dirty trick. March will hopefully get rid of it.

[Brian Rupnow]

The design is complete and the detail drawings are all finished. The only parts not shown on the drawing are the valve springs. I will root around in my stockpile of odds and ends to see what I actually have to start working on, knowing that I will buy the bulk of the material on Monday to really get into this.

[Ye-Ole Steam Dude]

Good morning Brian,

Another really neat design from you and an interesting project that I will be following.

Have a great day,
Thomas