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

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Brian Rupnow

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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

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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.
 

Brian Rupnow

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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).
 

Brian Rupnow

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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!!!
 

CFLBob

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Count me following, too, Brian. The way I figure it, that's 2.0 cubic inches, and I think that should be able to do useful work.

It seems that getting above 1 HP is where that becomes realistic.

EDIT to add: Will the flywheels be set up to blow air across the engine? Will they both have to move air in the same direction?
 

Brian Rupnow

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Yes, they will both be set up to flow air in the same direction. If they blew air towards each other or away from each other, I don't really know what the air flow would be like. If they both blow air the same direction, then I can be sure that they push/pull the air in the same direction, over the cylinder.
 

Brian Rupnow

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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.
 

a41capt

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Brian,
Another beautiful design, and I will be following and looking forward to the first run!

Since you announced that you’ve purchased a TIG machine, I thought it would be used to weld the aluminum engine components (such as the frame) rather than bolt them together. Is there a reason for not welding in your design? As a budding model engineer, this concept is of interest to me.

Thanks so much for your contributions. To a relative newbie such as myself, they’re very inspirational and get my own creative juices flowing!

John W
Camp Verde, AZ USA
 

Brian Rupnow

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Yes, there is very good reason for not welding the frame together. I build these engines and then sell the plans all over the world. Most of the people who buy my plans have a small lathe and mill, and not much else in the line of fabrication equipment. Even the flywheels, which I will fabricate with the tig welder can be made from simple discs of steel or brass.If you need a tig welder to make my engines, nobody would buy the plans.
 

a41capt

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Yes, there is very good reason for not welding the frame together. I build these engines and then sell the plans all over the world. Most of the people who buy my plans have a small lathe and mill, and not much else in the line of fabrication equipment. Even the flywheels, which I will fabricate with the tig welder can be made from simple discs of steel or brass.If you need a tig welder to make my engines, nobody would buy the plans.
Ahh, excellent reason indeed! As a fairly accomplished TIG welder, I was thinking too small!

Now, if I could be a “fairly accomplished” machinist as well...

Thanks again, and I can’t wait to see the work progress on yet another masterpiece!

John W
Camp Verde, AZ. USA
 

LorenOtto

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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

 

LorenOtto

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I will take much pleasure in watching you develop this unique design.
 

Brian Rupnow

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So what do you do when it's the middle of winter and you don't want to go and play outside?--Well of course, you make parts!!! I've rootled thru all of my scraps and came up with enough material to make the main rocker, the two cross pins for the ends of it, and the two spacers that keep the rocker centered in the frame. I have to buy a bunch of aluminum plate, but I've got enough odds and ends of material here to keep me busy over the weekend.
 

Brian Rupnow

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Today was connecting rod day at my house. My, but there is a lot of work in one lousy connecting rod---and it isn't finished yet. I still have to turn 0.031" off each side and leave a boss at both ends. Also, I've added a shot of the biggest icicle in the world. It's hanging off the eves over my back deck. I don't think I have ever seen an icicle this big. It's over six foot long!!!

 

Ghosty

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Brian,
A tad cool at your place, opposite here today, it was 25deg C(77 F) at 5:30 this morning, almost 30deg C(86 F) @ 9:30am
20200302_092924[1].jpg
 

werowance

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just subscribing to the thread so I can follow along. looking good Brian.
 

Brian Rupnow

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Just got back from running around town. In one picture you see all of the material and bearings for Thumper ($98.00) in the other you see my new TIG welder, so new I haven't got it out of the box yet.

 
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