Atkinson frustrations

Gordon said:

Thanks. Maybe I can get this figured our yet.

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I ordered some material to make an adjustable piston rods for both left and right pistons. Seems that may do the same thing as moving pivot points.

Hello Gordon I have left some information on your email you may have overlooked the importance
of the actual movements of these arms as the differential ratios of travel for the pistons are extremely important and I'm not sure you will fix it by just adjusting the position of the pistons. My engine is a long way from being perfect although I have had running for about three hours run time. I have found that the fuel mixture is critical this seems to be a very small difference between running rich and lean I must say the engine is extremely efficient would have not used any more
than approximately 80 mil for three hours run time.

Leith

Motorteb said:

Hello Gordon I have left some information on your email you may have overlooked the importance
of the actual movements of these arms as the differential ratios of travel for the pistons are extremely important and I'm not sure you will fix it by just adjusting the position of the pistons. My engine is a long way from being perfect although I have had running for about three hours run time. I have found that the fuel mixture is critical this seems to be a very small difference between running rich and lean I must say the engine is extremely efficient would have not used any more
than approximately 80 mil for three hours run time.

Leith

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Thank you. I will do some work on that. It is interesting because the left arm and the right arm are different. They are both the same on the Gingery plans. That may make the difference.

Gordon

Gordon said:

Thank you. I will do some work on that. It is interesting because the left arm and the right arm are different. They are both the same on the Gingery plans. That may make the difference.

Gordon

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I can see how different length pivot arms could make a difference. I have finished my new 100% machined cylinder. I have also finished making adjustable piston rods (not sure it will make a big difference, but does give me some more adjustability. Was so close to running before). Still need to machine new pistons (ordered some 1.125 rings that should be here in a few days). How things going on your end Gordon? Thanks to Mr. Leith for sharing his experience with this engine. Ray.

Ramoye said:

I can see how different length pivot arms could make a difference. I have finished my new 100% machined cylinder. I have also finished making adjustable piston rods (not sure it will make a big difference, but does give me some more adjustability. Was so close to running before). Still need to machine new pistons (ordered some 1.125 rings that should be here in a few days). How things going on your end Gordon? Thanks to Mr. Leith for sharing his experience with this engine. Ray.

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I just finished CAD drawings on this design. It looks good. I think that it could work. It will involve making new front and back panels and new arms. Right and left. If interested I can email you my rather crude CAD layout. I still have not mastered 3D so it is 2D.

Gordon,

Looks like it will work. Did you use the Gingery cylinder port locations for your CAD model? I assume the link arms and piston rods are the same length? In the bottom of the drawing, are the oscillating arms and panel a comparison to the Gingery parts?

Seems from your operation views (in the upper part of the drawing) that the compression would increase on the spark plug side of the cylinder. On the Gingery version, the pistons were hitting at the exhaust port and had a wider gap at the spark plug port. This may explain the higher compression on the valve side of the cylinder.

Thanks Gordon.

Ray

Ramoye said:

Gordon,

Looks like it will work. Did you use the Gingery cylinder port locations for your CAD model? I assume the link arms and piston rods are the same length? In the bottom of the drawing, are the oscillating arms and panel a comparison to the Gingery parts?

Seems from your operation views (in the upper part of the drawing) that the compression would increase on the spark plug side of the cylinder. On the Gingery version, the pistons were hitting at the exhaust port and had a wider gap at the spark plug port. This may explain the higher compression on the valve side of the cylinder.

Thanks Gordon.

Ray

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The linkages are from the Gingery plans. It looks like the left piston completes the travel to the end faster so that the right piston can compress the fuel mix. The original design has both pistons traveling in tandem at about the same speed so that the mix did not get compressed.
Gordon

Gordon said:

The linkages are from the Gingery plans. It looks like the left piston completes the travel to the end faster so that the right piston can compress the fuel mix. The original design has both pistons traveling in tandem at about the same speed so that the mix did not get compressed.
Gordon

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Thanks Gordon. I assume your CAD model used the Gingery port locations?
Are you planning on making new front and back panels, as well as new oscillating arms?
Ray

Ramoye said:

Thanks Gordon. I assume your CAD model used the Gingery port locations?
Are you planning on making new front and back panels, as well as new oscillating arms?
Ray

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It looks like the Gingery port locations will work if the cylinder assembly is moved about 1/16 to the right. I will probably make new panels and new arms. I have so much time in this thing at this point a few more hours is not a big deal. Hopefully the cylinder can be reused. I have done some more playing around with CAD to try to check things out. I have not checked the stroke length on the two designs and will check that tomorrow when I am back in the shop.

Obviously there are other designs out there.

Gordon

Thanks Gordon. I plan on drilling the 3/16 port holes in the new cylinder tomorrow. Like you, I have put a lot of hours into this project. Enjoyed it though.

Ray

For others who may be interested, this shows the difference with alternate arms and pivot points. In the top sequence the left piston is retracting faster than the right piston so that there is more time for a compression stroke.
Gordon

Thanks Gordon. This is awesome. Shows what is going on.

Ray

Ray:
If you would like I can send you all of my drawings showing all of the parts for making a bar stock engine. I can send them in PDF or DXF or DWG if you can read them in that format. This forum will only permit PDF so if you want send me your email and I can send them direct.

Have a look thru my build. You might see something that would help you out.---Brian
Apparently I can not post a link to my build here, so Google Brian Rupnow Atkinson engine and it will let you in thru the back door.---Brian

Brian Rupnow said:

Have a look thru my build. You might see something that would help you out.---Brian
Apparently I can not post a link to my build here, so Google Brian Rupnow Atkinson engine and it will let you in thru the back door.---Brian

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Thanks Brian. Really nice job on your engine! The engine Gordon and I are building is the Atkinson Differential Engine. I believe your engine is the Atkinson Cycle Engine. Ray

Gordon said:

Ray:
If you would like I can send you all of my drawings showing all of the parts for making a bar stock engine. I can send them in PDF or DXF or DWG if you can read them in that format. This forum will only permit PDF so if you want send me your email and I can send them direct.

[email protected]

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Thanks Gordon. Just sent you my email address. Ray

Gordon said:

This post is to vent my frustration but if someone has some insight it is certainly welcome. I am building the Atkinson Differential engine from the Gingery plans and I am not having any luck in getting to run. Gingery said that he had to turn the engine over with an electric motor and a belt to the flywheel for up to 40 hours to seat the rings before it would start dependably. I have been doing that for quite a few hours (25-30) but I am not seeing any improvement. I am sure that the problem is compression but a solution escapes me. Due to the unique design you can only feel the compression on the last portion of the compression stroke because the spark plug hole is covered until the last part of the stroke. There seems to be good suction at the spark plug hole on what would be the exhaust stroke.


At this point it kind of fires about 1/3 of the time and even that is intermittent. If fires for a while and then quits firing until something like carburetor adjustment or cool off occurs. I have tried different spark timing and different carburetors and carburetor adjustments but nothing seems to change. I am using the S&S ignition and there seems to be a good spark.


At this point I am reluctant to remove the pistons/rings for inspection because if they are actually seating the rings are going to be in a different rotation when it is reassembled which I assume would at least partially disturb the seating in process.


There seems to be a surprising lack of information and build logs on an engine which has been built by quite a few others. There are quite a few Youtube videos. There are several errors or at lest omissions on the drawings but I have not seen any reference to this by any others. I have been over by engine and checked it to the drawings many times and as far as I can tell it is made correctly.

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Gordon,

The problem with most hard starting home builds is not the piston and rings, it is the finish of the cylinder bore. I have found in the last few years of playing with model engines that this is the most often mis understood factor.

The remedy here is to finish the bore of the cylinder dead straight and perfectly round. This is only possible to achieve with a lap or hone. When I say hone I am NOT referring to the spring hones often used by model engine builders, I am talking about a precision hone like used in automotive machine shops. These generally use a single stone mounted on a mandrel with precision cut radius supports opposite it in the cylinder bore. This type of hone will routinely hold a +/- .0001" tolerance on roundness, straightness and diameter in the hands of a skilled operator.

I see two options for solving your problem...

First would be to read up on copper laps, perhaps you could build a simple copper lap on your lathe and then lap your cylinder straight and true. It takes a lot of time and you will learn something on the way.

Second option, take your cylinder to an auto repair shop that has a Sunnen rod hone and tell the machinist there to make the hole straight, round and true and finish as fine as possible. He will probably charge you $15.00 or so to do the job and then you can build new pistons and rings. Once you have the engine back together it should be running in no time, it will be necessary to seat the rings.

TIP!... get some super fine lapping compound and dope up the cylinder bore with a small amount of it mixed with light oil (3 in 1 works here) and dry run the engine for a few minutes with your electric motor. dismantle and clean out the abrasive compound, put the motor back together and it should be fairly easy to start. I use this method on my engines and if bore and piston fit is good the start very easy after lapping in.

In my shop, I have a Sunnen MBB hone and mandrels, most home shops do not have such a luxury. (my shop is a working machine shop and has been for almost 30 years).

Rod

Gordon said:

Ray:
If you would like I can send you all of my drawings showing all of the parts for making a bar stock engine. I can send them in PDF or DXF or DWG if you can read them in that format. This forum will only permit PDF so if you want send me your email and I can send them direct.

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Gordon,
Had any luck with your engine? I finished my new cylinder and pistons with new rings from Otto (everything fit nicely). Ran it a couple of hours with electric motor assist, but disappointed that I did not get any strong pops. Will run it some more to see if additional break-in makes it run. Beginning to think I will need to make new oscillating arms and panels. Ray

Ramoye said:

Gordon,
Had any luck with your engine? I finished my new cylinder and pistons with new rings from Otto (everything fit nicely). Ran it a couple of hours with electric motor assist, but disappointed that I did not get any strong pops. Will run it some more to see if additional break-in makes it run. Beginning to think I will need to make new oscillating arms and panels. Ray

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I made new arms and panels. It has much better compression but I still cannot get it to run on it's own. It fires every stroke but not enough to keep it going. Then the braze on the crank broke and I just got that back together yesterday and decided to try moving the cylinder to get a longer compression stroke and a shorter intake stroke. It is closer to running but there is still something not quite right. I slotted the hole on the intake port and that may be my problem. So far I have remade just about every part but the base and the side panels.

If you decide to remake the arms and front panel let me know and I will send you my revised as built drawings.

Gordon

Gordon said:

I made new arms and panels. It has much better compression but I still cannot get it to run on it's own. It fires every stroke but not enough to keep it going. Then the braze on the crank broke and I just got that back together yesterday and decided to try moving the cylinder to get a longer compression stroke and a shorter intake stroke. It is closer to running but there is still something not quite right. I slotted the hole on the intake port and that may be my problem. So far I have remade just about every part but the base and the side panels.

If you decide to remake the arms and front panel let me know and I will send you my revised as built drawings.

Gordon

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Looks like you are getting close. I slotted the intake hole in my old cylinder and it helped, maybe it will help you (puts more fuel in the cylinder, I believe). I have not done that on my new cylinder, YET. I had a much better day today. I was getting strong pops and the cylinder was getting very hot. Seems to be burning more fuel with the new cylinder (may indicate better suction). I plan on running it some more tomorrow with the electric motor. Total of 6 hours so far with the new cylinder. I now have the option to adjust the piston rod length if I have no success with additional break-in. If all fails, I will make new oscillating arms and plates. Good luck Gordon. Maybe we will beat this thing! Ray.