Oscillating I.C. Engine

[RonGinger]

For the small size engines we are talking about here just about any metal ought to work. Nothing gets heavily loaded. We dont run them long enough to do any real wear. If you make an aluminum cylinder and pivot how many hours do you expect it to run? Ill be most models dont run more than a few dozen hours in their lifetime. Has anyone ever taken a model apart and noticed major wear?

I am sure neither Phil Duclos or Bob Shores ever did any calculation to determine the metal type- they just specified what they liked to work with.

 

[Brian Rupnow]

If I make the cylinder from cast iron, it will be fairly easy stuff to work with. The only issue I see with cast iron is that the bosses on the sides will be fairly delicate---will need to use a very sharp tool when machining them or they will pop right off of the main cylinder block.--(Don't ask me how I know this!!) However, the bore and fins are pretty easy to machine in cast iron. If I make the cylinder from aluminum it will be super easy to machine, and will be very "flashy", but I don't think the pivot bosses would last very long, and I don't know how the bore would stand up to interaction with a sharp edged cast iron ring on the piston.--Would probably be okay with a Viton ring and a bit of oil mixed with the fuel for lubrication. --Could possibly press fit a thin bronze bushing over the cylinder bosses to take the "wear factor" from oscillating. Steel would definitely be the material of choice in regards to strength and wear factor of the pivot bosses, and it wouldn't be too bad to machine the bore and the outer shape and the bosses.--Could however, be a real "bear" to machine the fins into. I plan on using an HSS slitting saw to cut the fins.--Decisions, decisions--

 

[Barnbikes]

Could you make an aluminum cylinder and press fit steel pins into it for pivot points?

How about making the head out of steel and .750 deeper and put the pivots on it?

 

[Brian Rupnow]

Could you make an aluminum cylinder and press fit steel pins into it for pivot points?

How about making the head out of steel and .750 deeper and put the pivots on it?

Barnbikes--I thought about making the head from steel and doing as you suggest.. It poses a problem though, since the intake/exhaust hole goes thru the pivot on one side. If I did that, then I would have to seal between the head and the cylinder on the side as well as on the top.---Brian

 

[Brian Rupnow]

The cylinder is pretty simple. The slots which create the fins are the scary part. I know my small mill does a great job cutting .094" wide x 3/8" deep in aluminum. Probably it wouldn't grunt at cast iron. Steel though---Ah, Jeez, I'm not sure about that.

 

[Swifty]

How about making it out of aluminium and making the pivot bosses larger in diameter, and also shrink fitting a brass or bronze sleeve on each side. As drawn, the walls of the boss are only 1/16" thick, a bit thin for aluminium.

Another idea, make the main piece straight sided, machine a counterbore in where the pivots are, and loctite a bronze boss in place. The boss could have a large head on it that fits in the counterbore, allowing more area for loctite.

Paul.

 

[Brian Rupnow]

Another idea, make the main piece straight sided, machine a counterbore in where the pivots are, and loctite a bronze boss in place. The boss could have a large head on it that fits in the counterbore, allowing more area for loctite.

Paul.

Paul--I like that idea. but--air cooled engine--gets hot--Loctite releases when hot.

 

[Swifty]

I just checked the highest temp handling loctite, only 180 C, not a lot. Could you make the area around the pivots wider and use small fasteners to hold the pivots in.

Paul.

 

[Brian Rupnow]

Paul--I really like the idea of aluminum. It has a far higher "bling" rating than either cast iron or steel, doesn't rust, and best of all is really easy to machine. I don't think my small mill would have enough power to cut the fin-grooves into steel. I could indeed make the area around the pivots wider, and use small fasteners. It would require blind tapped holes so as not to break through into the combustion chamber---or---move the fasteners so they are either above or below the cylinder bore.--I will think on this----I've still got a ton of bronze here.--Thinking--Thinking---

 

[Jasonb]

CI will polish up to a high "bling" if you want it to.

Why not do a practice cut in a scrap of the same grade steel to see if your mill is upto it before you decide

 

[Charles Lamont]

You could make steel pivots rather like two-bolt pipe flanges with fixings above and below the cylinder centre line to give more depth to the blind holes. A short shoulder on the back would locate in the cylinder, and if you wanted, the whole asssembly could be put between centres for a final light cut to ensure the bearing surfaces of the pins were absolutely in line.

 

[Charles Lamont]

Oh, and another thing. All that air being pumped in and out of the bottom of the cylinder is a criminal waste. How about designing it to at least allow the option of fitting some valves at this end? You could have a very compact little compressor! The maximum output pressure the engine would comfortably drive against could be increased experimentally by increasing the diameter of the piston rod. Worth a bit of thinking time, surely?

 

[Brian Rupnow]

Or---How about an alternate design--aluminum cylinder with radial grooves (easier to make on a lathe), thicker cylinder wall, and hard press fitted steel pivots?

 

[nemoc]

I like it! Looks great and solves all the problems.

 

[vascon2196]

Or---How about an alternate design--aluminum cylinder with radial grooves (easier to make on a lathe), thicker cylinder wall, and hard press fitted steel pivots?

Looks like that design will work out sweet.

 

[Brian Rupnow]

Without getting too far into fixing up the other bits--it would look like this.--Kinda cool, I think!!

 

[Brian Rupnow]

That cylinder reminds me of the bee-hive that used to be on the old Bee-Hive Cornsyrup cans. Of course, you have to be a long ways on the wrong side of 50 to remember them cans.

 

[Barnbikes]

Looks great. Need to make a round connecting rod guide though.

I started building one of these last year but talked to a guy at a local show who could never make his run and stopped mine. He claimed the flywheel in the plans is way to small.

As far as the spark plug you might have to make a plug with the old style screw on cap and have a eyelet on your wire so it does not fall off.

 

[canadianhorsepower]

Without getting too far into fixing up the other bits--it would look like this.--Kinda cool, I think!!

Hi Brian
nice project, but the rotating mass transfer is so big it will be worst then a
grasshopper.:hDe: engine vibration goes 90 degree forward to the power stroke in your case all the power would hit the ground and jump all over the place. I told you the same thing about your own design:fan: but you told me no it would be fine..........when I started working on your design after my cancer fight you told me "it's jumping all over the place change the crank balance" this is the same case

cheers
Luc

 

[Brian Rupnow]

Luc--You may well be right. Almost all of the i.c. engines I have built will "jump all over the place" if they are not bolted down to a table. I'm not too concerned if it tries to jump around, as long as it runs. Many single cylinder engines used on lawnmowers, weed-eaters, chainsaws, and cement mixers would "jump all over the place" if you set them on a tabletop with out bolting them down and tried to run them.