Atkinson frustrations

Discussion in 'General Engine Discussion' started by Gordon, Jul 9, 2018.

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  1. Oct 24, 2018 #101

    Ramoye

    Ramoye

    Ramoye

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    Gordon,
    Had a good day today. The engine kicked over a few times on its own. It ran, with electric motor assist, more consistent than ever before. Cylinder got very hot. Switched to 1 7/16 links on both ends, and adjusted the piston rod lengths so that both pistons are nearly even with the ends of the cylinder. I had to play around some with the timing. I now have 15 hours on the new cylinder. I will run it some more tomorrow and see if it develops more power. How things going on your end? Ray
     
  2. Oct 26, 2018 #102

    Gordon

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    I am not making much progress. The engine fires but still not enough power to run on it's own. I am sure that the problem is that I now have a mix of two different designs so the position of the ports is wrong. I am making a new cylinder. I should not have slotted the intake port. That makes the intake stroke too long and the compression stroke too short.
    You said that you have made adjustable piston rod. I am curious as to how you did that. I have seen engines made with adjustable top linkage rods but not the connecting rods.
    Gordon
     
  3. Oct 26, 2018 #103

    Ramoye

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    Gordon,
    The last couple of days saw no improvement from the other day. The cylinder gets very hot and the engine can kick over 3 0r 4 times on its own. I now have 21 hours on the new cylinder. I have adjusted the pistons to various positions, adjusted the timing and carb., and achieved the same results. I am beginning to think the Gingery design has some flaws. Seems the compression needs to be higher for complete combustion. Still measuring about 8 psi at the spark port. Still got some leakage by the pistons at 90 psi (measured 1.125/1.124 diameter at all points along the cylinder, and could not get a .002 feeler gage (smallest size I have) between the ring and groove wall). Maybe it still needs more break-in?

    I made the variable piston rod by drilling a hole for a 10-28 thread between the fork toward the piston end (rod aligned vertical in the mill) to a certain depth for a bolt (depends on how much adjustment you want). I then cut the rod into two pieces, plus took a little material out for adjustment clearance (I choose 1/4 inch adjustment capability). I then tapped the two parts for a 10-28 thread (could use 10-24, but 10-28 gives a little finer adjustment). I cut the head off a 10-28 aircraft bolt I had (had to use a die to cut additional threads on the shank) and screwed it into the piston half of the rod, applying some epoxy on the threads to secure it. To use, just screw the fork end of the rod onto the bolt/stud and pin to oscillating arm. I used a small check nut to make the assembly a little stiffer, but I do not believe you really need it. I hope my description makes sense?

    Ray
     
  4. Oct 26, 2018 #104

    Gordon

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    That makes sense. I understand. I have also pretty much come to the conclusion that the Gingery design is marginal at best. I am still working on the new cylinder. I have at least enough extra parts to make most of another engine. I have built about 20+ engines in the last several years and I have never had one which gave me this much trouble. I have usually found that I have as much time in getting an engine to run as I have in making the engine in the first place. I see these other folks posting videos of a completed engine and showing it running the first try with just a few minor adjustments. I have never had that happen.

    Gordon
     
  5. Oct 27, 2018 #105

    Ramoye

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    If you look close on the videos, looks like some engines have been modified from the original. Starting to understand why. This is a tough engine to make run. I will run it some more (another 30 hours), but growing doubtful it will work. May have to redesign it by making new panels, oscillating arms, and links. I would like to see higher compression on the spark plug side. I believe mine is just burning gas vs. combustion.
     
  6. Nov 2, 2018 #106

    Ramoye

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    Gordon,
    How things going on your end?

    I have concluded that a design change is in order to make this engine run. Compression is very low on the spark side, but compression much higher on the valve side. This is due to the two pistons almost hitting on the valve side, but a piston gap on the spark side. This is also causing spitting through the carb., which I believe is causing some fuel starvation into the cylinder. Just can't produce enough power. I pressurized the cylinder with 90 psi through the spark plug port and it held, indicating to me that the pistons, rings and cylinder are good.

    I have an idea. What if an offset crank pin is used for the two oscillating arms. This would move the compression from the valve side to the spark side (pistons almost touching on spark side, but wider gap on valve side), which should greatly reduce carb. spitting (allowing better intake of the fuel charge). The offset crank pin could be made with a taper on the end to lock it into the crankshaft (the 3 inch plate on the end), allowing adjustability of the oscillating arms. Would require the four jaw chuck to make the offset crank pin. I am thinking a 1/8 inch offset, that could be adjusted to less if need be. May need a cup washer over the end of the crank pin to lock the taper end of the offset crank pin down with a bolt. What do you think about this? I ran this idea by a friend of mine and he thinks it might work and worth a try.

    Ray
     
  7. Nov 2, 2018 #107

    Gordon

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    Making an eccentric crank pin would indeed change the relative stroke distances. You could do the same by modifying the upper link length. If you look at some of the other videos and images some of them have an adjustable link with a threaded adjustable connection between the crank and the top of the crank arm. The original patent drawing had that. That should be fairly easy to make.

    So far I am not having much luck on my remake. I screwed up the cylinder by misreading the relief distance on the top of the cylinder so that I cannot move the cylinder to the right as far as it should go without getting leakage because the rings are actually coming out of the bore into the now too long relief area.

    So far no matter what I do on the original or the rework ends up pretty much the same result where I get a firing but not enough to actually power the engine. I am not sure what is happening but I get a loud firing when it fires and not a controlled firing.

    Gordon
     
  8. Nov 2, 2018 #108

    Ramoye

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    Gordon,

    Unless I am missing something, it looks like to me the eccentric pin has a different effect on the oscillating arms than changing link arm lengths. For example, a shorter link arm on the power stroke would put the right piston farther to the right of the spark plug hole, whereas an eccentric would put the right piston farther to the left (thus closing the gap, creating more compression). The left hand link arm length would remain the same via the eccentric pin. Could you look closer at this to see if I am missing something? Thanks. Ray
     
  9. Nov 3, 2018 #109

    Gordon

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    Perhaps I am not thinking right. I am wrong as often as I am right but if you put in an eccentric pin and added say 1/16 to the radius the c/c from the crank C/L to the pin C/L is now 1 3/16 (1 1/8 + 1/16). Picture the crank at 3 o'clock which would move the pivot point to the right by 1/16. Now picture the same thing with the C/C still at 1 1/8 but make the right link 1/16 longer and the left link 1/16 shorter. One link 1 9/16 + 1/16=1 5/8 and the other link 1 9/16-1/16=1 1/2. The result is the same. Also true at 9 o'clock. By making adjustable link or new links you could move one piston without affecting the other. For example keep one link at 1 9/16 and make the other 1 1/2 or 1 5/8. You would have to play around with it to determine which link or links to change to move the move one piston right or left. The advantage of adjustable or changing links C/C is that you can change one with out changing the other.

    As I said, I may be completely wrong.

    Gordon
     
  10. Nov 3, 2018 #110

    Ramoye

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    Gordon,

    Thanks for looking at this again. I may be wrong, but what I am seeing with an eccentric pin would produce the same results as swapping longer and shorter link arms on the right oscillating arm as it is running. Of course swapping longer and shorter arms as it is running would be impossible, but achieving the same results would be possible with the eccentric pin. I have tried every combination of link arm lengths and still end up with a gap at the spark plug port and pistons nearly hitting at the exhaust valve port (my pressure gage indicates this, 8 psi at the spark plug port, 30 psi at the exhaust port). I believe why the eccentric pin works is because the effect on the right piston is different as it rotates 180 degrees. At 3 o'clock the offset pushes the right piston further to the left (closing the gap between the two pistons at the spark plug port, creating greater compression). At the 9 o'clock position, the offset pulls the right piston further to the right (producing a greater gap between the pistons at the exhaust port). The net effect should be greater compression at the spark plug port and less compression at the exhaust port (which is what we want for better combustion and increased fuel charge (reduces carb. spitting)). I might be wrong, but I am going to try it (need the practice anyway on using the four jaw chuck to make an eccentric pin). I will let you know what the results are. Thanks Gordon. Ray
     
  11. Nov 3, 2018 #111

    Gordon

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    The more I look at this thing the more confused I get. Give it a try and see what happens. I am curious to see what the results will be.

    FYI: Using the three jaw chuck you get an offset of 2/3 of thickness of a shim on one jaw. In other words putting a 1/4" thick shim on one jaw creates a 3/16" offset.

    Another thought is that since you will have to make a new 3" dia cam disk you could just drill a series of holes around the disk in say 1/16" increments to get +/- 1/8" from center. Properly spaced at 45° it would look like it was planned.

    Good luck.

    Gordon
     
  12. Nov 3, 2018 #112

    Ramoye

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    Thanks Gordon for the tip on using the three jaw chuck for an offset. I will try it. On the 3 inch disk, I will need to cut the crank pin off (clean it up on the lathe) and drill a new hole. I would like to make a tapered hole (also a taper on the end of the eccentric pin) to make the eccentric crank pin adjustable by rotating it (also need to make it removable to install the oscillating arms). Good idea on drilling extra holes to make it look better.
     
  13. Nov 4, 2018 #113

    Ramoye

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    Gordon,

    I made a prototype eccentric pin from aluminum to prove the concept and to develop a manufacturing process. The concept worked as I envisioned. I was able to close the gap between the pistons at the spark plug port and widen the gap at the exhaust valve port (no more pistons hitting) by rotating the eccentric pin. This should flip the compression over to the spark plug side of the cylinder instead of the valve side, with the flywheel rotating clockwise (hopefully resulting in better combustion and fuel intake). I now feel comfortable in going ahead with modifying the crankshaft. Below is my plan:

    1) Cut the existing crankshaft pin back for installation of the eccentric crank pin. Drill a thru hole through the remaining length of the crankshaft pin and 3" disk for installation of the eccentric pin with a #10 bolt.
    2) Machine a eccentric pin that will fit over the existing remaining cut-off portion of the crankshaft pin (the eccentric pin will have a 1/2 " counterbore (1/4 " deep)) with a thru hole for mounting with a #10 bolt. I will use a 3/16 " shim in the three jaw chuck for creating the eccentric pin (your tip on this worked great when I made the prototype). The eccentric pin will also be machined as to replace the 1/2 " crankshaft spacer (called out in Gingery's book) between the oscillating arms.
    3) Mount the eccentric pin to the existing remaining cut-off portion of the crankshaft pin using a #10 bolt, washer, and nylon lock nut. Adjustment can be made by loosening the nut and rotating the eccentric pin, then retighten.
    4) Make two new piston rods per Gingery's book (will replace the adjustable piston rods I previously made, no longer need them).

    When I finish all this, I will try to run the engine again. Very curious as to how these modifications will change the engine performance.

    Ray
     
  14. Nov 4, 2018 #114

    Gordon

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    I am not too sure that I understand your process. Apparently you brazed the pin in the 3" disk. I made it 1/2" dia with a 3/8" dia shoulder to fit into a 3/8" hole reamed in the disk and held in place with a #10 machine screw. With that it would simply be a matter of making a new pin by offsetting the 3/8" shoulder and rotating it into the proper position. One of the drawings which I sent you shows how I did it. I do not have the book here now but I thought that was how Gingery made the pin as a shouldered piece. Not offset of course.

    Two thoughts: Could you determine the proper offset with your temporary set up, cut off the existing pin and just drill a new hole in the 3' disk at the new distance. ie: 1.125 +/- the offset? Would't it be easier to just make a pin with the offset shoulder?

    Carry on. Good luck.

    Gordon
     
  15. Nov 4, 2018 #115

    Ramoye

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    Gordon,
    Originally, I made the crank pin per the Gingery book (it was a press fit). But after much running, the pin started spinning in the hole. I repaired it by brazing it to the 3" disk.

    I thought about doing what you are describing, drilling a new hole in the 3" disk. With a press fit though (per Gingery's book), it would be difficult in removing the pin should I need to take the left oscillating arm off (with an offset shoulder in the pin, would not be able to slide the left oscillating arm onto the crank pin from the front). I thought about putting a taper on the pin and drilling a tapered hole in the crankshaft disk (would tighten a bolt to lock it down), but it would require me to set up the 4 jaw chuck to put the tapered hole into the crankshaft disk. The way I was planning on doing it is easier/faster, but maybe not as robust as a single pin with a tapered end (without the taper, it might start spinning in the hole). I may take the time to make the more robust design. I will give it some thought tonight. Just anxious to get it running to see how this concept works. I am moderately confident about the engine running using this concept (hopefully not another letdown though).

    Ray
     
  16. Nov 4, 2018 #116

    Ramoye

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    Gordon,
    I re-read your message. My concept would keep the left oscillating arm on the pin as originally designed, but the right oscillating arm would ride on an offset. If I did what you were describing about an offset shoulder in the disk (assuming I am understanding it as you described), it would move both pistons, which is not what we want.
     
  17. Nov 10, 2018 #117

    Ramoye

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    Hi Gordon,
    I made a test eccentric crank pin (that fit over the shortened crank pin) and spun the engine with the electric motor. The pressure at the spark plug went up from 8 psi to 12 psi, with only closing the gap between the pistons a little. I needed more of an offset to close the piston gap even further. I used an 1/8 inch shim on the lathe chuck jaw to make the test eccentric crank pin.

    I determined I needed a 1/4 inch shim on the lathe chuck jaw to make the eccentric crank pin. So I made another test eccentric crank pin and was able to close the gap between the pistons completely, but the thru bolt hole broke through the edge of the eccentric pin diameter. As a result, I made a full length crank pin with a shoulder that goes into the 3 inch disk, as you mentioned.

    I have now completed a full length crank pin. I still need to cut off the old shortened crank pin from the 3 inch disk, clean it up on the lathe, then move over and drill a new mount hole 1.125 inch from the center. I hope to attempt another run of the engine on Monday.

    One thing for sure, the eccentric crank pin is raising the compression on the spark plug side. It is also creating a greater gap between the pistons on the valve side. Will the engine run after these modifications, time will tell? I will let you know what the results are.

    How things going on your end?

    Thanks.

    Ray
     
  18. Nov 11, 2018 #118

    Gordon

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  19. Nov 11, 2018 #119

    Ramoye

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    Hi Gordon,

    Sorry to hear about your broken oscillating arm. I have broken parts too and have remade most of the parts two or three times. Encouraging that you are getting 30 psi compression.

    I finished all the new parts for the eccentric crank pin, and new piston rods, and started to put everything together. I had to sand the oscillating arms some on a belt sander to take care of some interference issues. I installed the 1 1/2 inch links and adjusted the eccentric crank pin. Pistons are almost touching at the spark plug and exhaust valve ports. I can actually rotate the flywheel by hand and make the intake valve open some (seems to have better suction), and getting much greater pressure at the spark plug port (just held my thumb over the spark plug boss). I may try to first run the engine at this setting. I may have to go to the 1 7/16 inch link on the right side if carb. spitting and fuel intake is still an issue. I will try to run it tomorrow. I need to go to the hardware store first thing in the morning to get a shorter 6-32 set screw for the right oscillating arm (the set screw I have is hitting the bottom of the cylinder when I adjust the eccentric crank arm). Excited to see what happens tomorrow.

    Best of luck Gordon.

    Ray
     
  20. Nov 12, 2018 #120

    Ramoye

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    Gordon,

    I ran the engine today with the eccentric crank pin. No real success. At one point, the engine did turn over a few times under its own power. I was not able to adjust it like I wanted, because at a certain point the right oscillating arm went over center (causing the two oscillating arms to hit when rotated). Seems like the right oscillating arm pivot point needs to move to a different location to give me the adjustment I need. This is becoming a science project. I will play with it some more tomorrow. Disappointing.

    Ray
     

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