6 Cycle Internal Combustion Engine

[Rdean33422]

I have seen engines where there is one cylinder and one piston but each end of the cylinder is a combustion chamber. The engine fires on both sides of the piston. This interested me so I looked deeper into the design and found there are several engines using this system and at first glance I thought I can make this. No problem.
Boy was I wrong as this design brings up several major problems. At first I thought I could just treat each end of the cylinder as a separate 4 cycle engine and use a distributor to control the spark. Use a side shaft with two cams at a 2 to 1 ratio of the crank shaft for the exhaust valves. What I found was that no mater how you configured the valve timing there would be a cycle when one side had fired and the other side was starting into compression. Most of the power from the first side would be lost.
Back for more research and found that several of these engines use 6 cycles.

Power
Exhaust
Exhaust
Exhaust
Intake
Compression

Yes the exhaust valve is held open for 1 1/2 revolutions or 3 strokes but you have to remember that there are two combustion chambers and as they overlap so the idle time is not too long. There are other ways of making a 6 cycle engine also but this is the way I'm going to attempt to do it. Attempt is right as there are many different operations I have never done before such as the valve timing for the 6 cycles.
The cam shaft now will make one revolution for every three revolutions of the crank shaft.

I'm just going to jump right in and see how it goes.

I salvaged a nice 10mm shaft from a hydro window opener or supporter.


I turned a piston from a piece of aluminum and with a light press and some red loctite positioned it in the center of the rod.


I bored 2" aluminum cylinder to 1.250 inside diameter for a nice piston fit.

I did make a rudimentary drawing of what it might look like.

Thanks for looking
Ray

 

[Rdean33422]

The picture shows the piston and two cylinder heads. The cylinder heads have an o-ring inside the extension part to seal the piston rod but still allow it to slide back and forth.


I have never done an internal o-ring groove before so i made a new tool.
It is just mild steel with about half the diameter milled off and a relief groove turned behind it.


It worked just fine once the height of the tool holder was adjusted.

Thanks for looking
Ray

 

[TonyM]

Looking forward to this one.

 

[Rdean33422]

Great to have you along Tony.
Much of this design is new to me so it will be a learning experience.

Ray

 

[JimSvarv]

Double acting engines exist for sure.
But I'm not sure how much it matter that a power stroke is at a compression stroke.
The power would be taken from the flywheel anyway.

It would be like a 180 degree crank inline twin which works for sure.

Your engine will be a bit like a hit and miss, maybe it runs a bit cooler with the gas cycling back and forth a bit.

Anyway always fun to see what you come up with!

Here is a kinda funny engine which is like the lower half of a double acting engine.
https://www.pattakon.com/pattakonPPE.htm

 

[Sprocket]

Ray,
I've been working on my interpretation of Phil Duclos' 6-cycle "Oddball". He used a 3:1 gear ratio and a long duration exhaust cam. The exhaust valve stays open for about 1/2 of the gear rotation, or 1-1/2 full crank rotations. It fires only every third rotation instead of every other.
It is a single cylinder, but I'm sure you can make it work for two with the side shaft fairly easily.
Also, for double acting cylinders, think of Doug Kelley's "Snow" engine. Your start looks a lot like half a "Snow". It is also a side shaft.
I enjoy your builds, can't believe how fast you work,
Doug

 

[Rdean33422]

Double acting engines exist for sure.
But I'm not sure how much it matter that a power stroke is at a compression stroke.
The power would be taken from the flywheel anyway.

It would be like a 180 degree crank inline twin which works for sure.

Jim I stand corrected you are right but it just seems that on this engine if the entire force of the power stroke is directed to just the flywheel it would be better but I could be wrong.

Your engine will be a bit like a hit and miss, maybe it runs a bit cooler with the gas cycling back and forth a bit.

During my research of this engine I found it is supposed to be 25% more efficient and run much cooler from the three cycles of the exhaust gases. That's not why I am building this engine. It just seems like a fun project.

Here is a kinda funny engine which is like the lower half of a double acting engine.
https://www.pattakon.com/pattakonPPE.htm

Now you've done it another odd ball engine for me to think on.
Thanks Jim for your comments

I've been working on my interpretation of Phil Duclos' 6-cycle "Oddball". He used a 3:1 gear ratio and a long duration exhaust cam. The exhaust valve stays open for about 1/2 of the gear rotation, or 1-1/2 full crank rotations. It fires only every third rotation instead of every other.
It is a single cylinder, but I'm sure you can make it work for two with the side shaft fairly easily.
Also, for double acting cylinders, think of Doug Kelley's "Snow" engine. Your start looks a lot like half a "Snow". It is also a side shaft.
I enjoy your builds, can't believe how fast you work,
Doug

That engine is very similar to this one except it will fire on each side of the piston.
I am not familiar with Doug Kelly's "Snow" engine I will have to look it up but I have seen the full sized "Snow" engine running here in Florida. That engine is a four stroke.
Thanks Doug this engine will be a slower build for me as there are many new issues to overcome like the one below.

I wanted the bolt holes on each end of the cylinder to be clocked the same. Using the bolt circle program on the mill I spotted the holes for one end. I then attached a small machinist clamp to the cylinder before removing the cylinder from the vise. The arms of the clamp were aligned with the jaws of the vise so when I turned the cylinder over to do the other end I just a lined the clamp up with the vise jaws, re indicated the part and did another bolt circle.


Drilled 24 holes and taped 12 in the cylinder and this is the result.


Thanks for looking
Ray

 

[Rdean33422]

I looks like the location of the piston on the piston rod was dead on so I installed a tapered pin to lock it in place.


The next issue was how I was going to hold the cylinder up and also secure it in place. I decided on a couple of 1/2" thick aluminum plates one added to each end of the cylinder. They will be bolted to some future frame from below. Not sure on the frame yet.




That brings up the next problem. The piston rod is only supported by the o-rings on either end of the cylinder. I could build a cross head and the associated mounts and fittings and it may be all right like that but that is a lot of extra work if it's not needed.
I am thinking of adding a brass bushings to each end of the supports to take up any side forces.
Any thoughts on that arrangement? 2" stroke 10mm shaft

Thanks for looking
Ray

 

[Sprocket]

Ray,
I think you will need guide bushings, and probably some form of a cross head. I don't know how you plan to connect the piston rod to a flywheel,
but if you allow for a wrist pin, and prevent rotation, it sounds a lot like a cross head.

https://www.homemodelenginemachinist.com/threads/the-snow-a-tandem-double-acting-engine.33305/

this is one way around it.

Doug

 

[Rdean33422]

this is one way around it.

Thanks Doug that is a possibility.

Ray

 

[Rdean33422]

I went ahead and installed a brass bushing in each end plate anyway to reduce any side loads but I still may make a cross head of some kind.



I drilled and taped holes for 2 intake valves, 2 exhaust valves , and 2 spark plugs.
Over to the lathe for some cooling fins.


Result so far.


Thanks for looking
Ray

 

[Rdean33422]

Busy day
I honed the cylinder to get rid of the ridges from drilling the intake, exhaust, and spark plug holes.
Cut out some head gaskets and a couple of spares. I have found that if I make some spare gaskets then I won't need them but if I make just enough I will mess one of them up.
Installed the piston o-ring and shined everything up some.

A couple of photos.







Thanks for looking
Ray