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Thread: Atlantic Make and Break Fabrication Project @MIT

  1. #36
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    Default Re: Atlantic Make and Break Fabrication Project @MIT





    Let me know if you would like any other pictures. As you can see, it's quite the technically advanced little thing. lol. Good luck!

  2. #37
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    Default Re: Atlantic Make and Break Fabrication Project @MIT

    Love watching this materialize, and this is actually relevant to me (my dad). He has an old pump motor (an Aeromotor) that's been converted to spark plug, with a model T coil, but seeing how simple these are, we might be able to re-create the original make and break points and coil.

    His is not a good candidate for a boat (air cooled, pump driven off flywheel with a rod, no rotational motion to tap into easily for a prop shaft), but the techniques you guys are inventing are directly applicable to our needs.

    Currently, he's having a new piston machined by some old guy out your way somewhere who makes new Aeromotor parts.

    We are watching, please share more, you might have a solution we could use.

    Thanks!!!
    Chris
    ____________________________
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    Tern, a William Atkins Pixie. Builder: Jeff Stobbe, 1997. Completed restoration 2016
    Sparkle, not a Herreshoff 12-1/2, same but stretched to 14-1/2. Builder: Jeff S, 2013.

    Previous: Ydun, Folkboat US 88, owned 1997-2000 ish, Berkeley, CA Sailed her one weekend, worked on her the next. Builder: Borresen, 1950 (Denmark)

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  3. #38
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    Default Re: Atlantic Make and Break Fabrication Project @MIT

    Quote Originally Posted by nedL View Post
    Let me know if you would like any other pictures. As you can see, it's quite the technically advanced little thing. lol. Good luck!
    Perfect - Thanks. I think that will get us most, if not all, of the way. Very helpful.

    Chris,
    Here's the 3D printed pattern and core mold for the piston (Sam's work). Wood may have been a more suitable choice for the pattern on this part. We can turn wood...but hey, it's all an experiment!
    Last edited by DoctorB; 03-19-2016 at 10:10 PM.

  4. #39
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    Default Re: Atlantic Make and Break Fabrication Project @MIT

    Here is Meaghan's beautiful eccentric (3" OD) and less beautiful, but equally cool, eccentric strap. The strap will be machined after spring break. We bought a new 7/16 D size broach for the eccentric keyway. The little marks are witness lines Meaghan used for aligning the bushing. The broach is a monster. We may repour because of some sinks on the far side & will move the sprue halfway along the part where the arm meets the strap.


    In other news, Sam had an awesome failed pour of the piston - the core disintegrated during the pour - but Sam and Foundryman Mike have a plan. Maybe she'll post some pictures. This afternoon, Sam stood wistfully over her cast mess of an iron pile, saying "you will be a piston one day..." You gotta love 'em.
    Last edited by DoctorB; 03-19-2016 at 10:11 PM.

  5. #40
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    Default Re: Atlantic Make and Break Fabrication Project @MIT

    Ok - Here's old school. Apprentice Eric making the flywheel pattern out of maple - see, it ain't all 3D printing!

    Last edited by DoctorB; 03-19-2016 at 10:12 PM.

  6. #41
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    Default Re: Atlantic Make and Break Fabrication Project @MIT

    Looking really good on both accounts! I like that eccentric.

  7. #42
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    Default Re: Atlantic Make and Break Fabrication Project @MIT

    Hey all! It's Sally, one of the original students from the Universal project.

    We've all been busy beavers 3D modeling the engine--not an easy task when most dimensions aren't called out in the original drawings. I guess that was unnecessary since they just had patterns at the Lunenburg Foundry that they made all the engines with! I assembled all the parts that the other apprentices helped model and created an animation:



    I'm happy to show different views if anyone has requests. Making the model was very helpful for me to understand better how the engine works.

    One of the parts that I'm working on is the cylinder. This is turning out to be a very tricky cast because of the water jacket. Anyone have an idea about how I could cast the cylinder and make the water jacket?

    The core for the piston is pretty easy: I'm currently in the process of making a plaster mold so I can slipcast it.


    Making a box in which to pour plaster for a core mold.

    This week is MIT's spring break, but the lab will be open Tuesday-Thursday and I hope to finish the core mold and start machining the connecting rod.

  8. #43
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    Default Re: Atlantic Make and Break Fabrication Project @MIT

    Quote Originally Posted by Sally Ann View Post
    Hey all! It's Sally, one of the original students from the Universal project.


    I'm happy to show different views if anyone has requests. Making the model was very helpful for me to understand better how the engine works.

    One of the parts that I'm working on is the cylinder. This is turning out to be a very tricky cast because of the water jacket. Anyone have an idea about how I could cast the cylinder and make the water jacket?

    .
    I suspect that there would have been a core for the cylinder bore, and another core for the water ways. The water inlet and outlet will probably have supported the water way core with one or two additional core stubs. Look for core plugs on the original cylinder if you can.
    It really is quite difficult to build an ugly wooden boat.

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  9. #44
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    Default Re: Atlantic Make and Break Fabrication Project @MIT

    On "modern engines" this is the real purpose of what people refer to a "freeze plugs" on engine blocks (they are really core plugs as Nick pointed out. There is a separate sand core that represents the shape of the water jacket. the sand core is placed in the sand mold and supported by the water inlet and outlet during the pour. Afterwards the sand has to be broken up and gotten out of the water jacket.

  10. #45
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    Default Re: Atlantic Make and Break Fabrication Project @MIT

    They'd get pretty creative with their part lines and supports; I really enjoy the puzzle of figuring out how any molded part must have been created. Keep looking at it and imagining possible solutions; it's sitting in front of you, so it's possible. You can reverse engineer it, if you're tenacious enough, and believe you can do it.
    Chris
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    Sparkle, not a Herreshoff 12-1/2, same but stretched to 14-1/2. Builder: Jeff S, 2013.

    Previous: Ydun, Folkboat US 88, owned 1997-2000 ish, Berkeley, CA Sailed her one weekend, worked on her the next. Builder: Borresen, 1950 (Denmark)

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  11. #46
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    Default Re: Atlantic Make and Break Fabrication Project @MIT

    Quote Originally Posted by Sally Ann View Post

    One of the parts that I'm working on is the cylinder. This is turning out to be a very tricky cast because of the water jacket. Anyone have an idea about how I could cast the cylinder and make the water jacket?
    It is not uncommon for automotive engines to have 'wet liners'. This is where the cylinder liner is a separate part that is pressed into the block in which the water jacket is open until the liner is pressed in. The four cylinder Peugeot engines of the sixties and seventies are the ones I was familiar with.
    There is nothing quite as permanent as a good temporary repair.

  12. #47
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    Default Re: Atlantic Make and Break Fabrication Project @MIT

    Here in the states liners (wet or dry) are very unusual on gasoline engines ( though I suppose aluminum blocks may utilize liners fairly commonly -a guess on my part). They are fairly common on diesel engines.

  13. #48
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    Default Re: Atlantic Make and Break Fabrication Project @MIT

    "Wet liners" require a more robust engine block/cylinder-head assy that can comfortably withstand the loads of the combustion process.
    Often older small marine engines use the "liner" itself as the tension member. (I suspect by design this one does). Some modern designs will use studs or cap screws from the crankcase to the head to do that.

  14. #49
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    Default Re: Atlantic Make and Break Fabrication Project @MIT

    Josh and Jarrod have been making progress with the crankshaft (1018 steel). They had an interesting setup on the lathe using 4-jaw chuck, live center, and counterweights for turning the throw. Then they cut material for the shaft, knocked off the corners and will be turning it within the next few days. They center-drilled the shaft and throw locations before removing any material and are really careful about indicating everything.



    Emma and Eric continued with the flywheel pattern. They have to part the pattern (there is a paper layer at the parting plane) and add the iconic heart cutouts.



    Sally is preparing the connecting rod pattern



    Brady is going to cast the water pump and retaining/piston nut



    Meaghan continues to work on the eccentric strap, and Sam and Sally are working on the cylinder and piston. Sam had another disintegrating piston core today using the resin-based sand. Something ain't behaving right, but I'm sure they will figure it out. The cylinder and base are the big bugaboos. Three weeks to go and counting. Give 'em hell.

  15. #50
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    Default Re: Atlantic Make and Break Fabrication Project @MIT

    Isn't that your job?

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    Default Re: Atlantic Make and Break Fabrication Project @MIT

    Hey All,

    Long overdue story update from the cooling system:

    I left off struggling to make my insert for the water pump body. I had 3D printed a core mold but the sand I was using would not solidify enough to retain it's shape once the mold was broken. I took a break from that part and made the piston that goes inside the water pump.


    After completing the piston, I used a different method for making the insert out of a resin based solidifying sand. The sand is made using a resin binder and catalyst mix.



    Once mulled together the sand turns green and begins to harden. I then had five minutes to pack my mold as the sand began to turn dark green and then black. Once hardened, I opened the mold and retrieved my insert.



    Success!! It took me a few tries to come up with the right mixing times and catalyst amounts. I ended up using less catalyst in order to allow myself more time to pack the mold.

    Next step was to pack the flasks with sand around my pattern. This was a straightforward process which smelled like baby powder and reminded me of playing in sandboxes in my backyard when I was 5.




    Continued...

  17. #52
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    Default Re: Atlantic Make and Break Fabrication Project @MIT

    I then placed the insert onto the sand mold and made the first pour. It's pretty cool to see brass melt like butter in the loudest induction cooker I've ever seen.




    This pour wasn't fluid and resulted in a part with welding seams and incomplete filling of the mold.



    Continued...

  18. #53
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    Default Re: Atlantic Make and Break Fabrication Project @MIT

    So I went through the process again, made an insert and packed the mold. Here's what the flask looked like before the poubr />


    The pour went much better the second time



    And the part turned out pretty nice



    That's all I have for now. I have one more part to pour and a lot of machining to do!

    Until next time!
    Brady

  19. #54
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    Default Re: Atlantic Make and Break Fabrication Project @MIT

    Wow. Nice. You guys have all that in your shop, or is that somewhere else?

    Love the apparent absurdity of this project. Reminds me of my dad's sculptures, some of which have and will use similar engines. He struggles to keep his running. Having a new piston made right now in fact.
    Chris
    ____________________________
    Current:
    Tern, a William Atkins Pixie. Builder: Jeff Stobbe, 1997. Completed restoration 2016
    Sparkle, not a Herreshoff 12-1/2, same but stretched to 14-1/2. Builder: Jeff S, 2013.

    Previous: Ydun, Folkboat US 88, owned 1997-2000 ish, Berkeley, CA Sailed her one weekend, worked on her the next. Builder: Borresen, 1950 (Denmark)

    Spokane, WA.
    Row, sail and sleep on the beach around Lake Pend Oreille, usually near Garfield Bay, Idaho.

  20. #55
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    Default Re: Atlantic Make and Break Fabrication Project @MIT

    Quote Originally Posted by csoxford View Post
    You guys have all that in your shop, or is that somewhere else?
    Fortunately, our place and the foundry down the hall.

  21. #56
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    Default Re: Atlantic Make and Break Fabrication Project @MIT

    Another Water System update:

    I started machining my first casting. It was a huge puzzle trying to figure out how to make parallel and orthogonal surfaces, but with some help from the shop guys I was able to figure it out.







    Unfortunately when I was plunging into the center hole, I didn't line it up quite well, which will lead me to problems later on






    I finished machining the part anyway, hoping that it would turn out okay, and for the experience in case I needed to make it again.





    I didn't have a 1 inch SPT die so I ordered one online and began casting the nut while I waited.

    Continued...

  22. #57
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    Default Re: Atlantic Make and Break Fabrication Project @MIT

    I set up another pattern, this time with the nut and an elbow piece from one of Megan's parts. We cast a leaded bronze this time (Hooray for machining with dust masks)





    After knocking off some burs I put the nut in the lathe and began turing it down



    By this time the tap and die set had come in. We didn't have a tap wrench big enough for this operation, so I got to do it the old fashioned way with a normal wrench



    Next step was to thread the body, I put it in the bridgeport and used a chuck to keep myself level.



    I was unsuccessful, there wasn't enough material to complete the thread.



    Two steps forward, one step back. At least the nut is done. Going to recast another body tomorrow morning, hopefully this one goes better!

    That's all for now! Stay tuned
    Brady

  23. #58
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    Default Re: Atlantic Make and Break Fabrication Project @MIT

    Looks very nice! (Other than that little "live and learn" bit there. lol)

    Hmmm, .... Here's a thought. .. Is there enough wall thickness to the body of the housing to cut the threaded portion off flush at the shoulder where the threads meet the main part of the pump body. Then bore the pump body maybe a 1/4" - 3/8" deep at the major diameter of the threads and press/solder in a piece of bronze round stock that you could then bore to match the pump bore and thread the outside of? If you like the casting other than this 'oops' that could well be easier than starting from scratch. Mechanically it would work fine. Just another .002.
    Last edited by nedL; 04-21-2016 at 11:18 AM.

  24. #59
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    Arrow Re: Atlantic Make and Break Fabrication Project @MIT

    Eccentric Update:


    The eccentric strap has been finished (at least so I hope!) The hole for the eccentric was machined yesterday and after some fine tuning (adding a chamfer in the corner and lapping the surface to be smooth) the eccentric actually spins in the strap!


    I realize there haven’t been many updates on the eccentric strap up this point so here’s a quick list of the post processing steps taken after the initial casting:
    - Used band saw and file to trim the flashing around the outer edges.
    - Clamped in the mill and faced top surface and sides of the top in order to zero in the mill later
    - Flipped part over and faced other side to the proper thickness (roughly 0.002” under size of the eccentric to fit nicely), ended up only taking off 0.02” total so not too much room for error! Some of the casting imperfections are still showing but should still work nicely to hold the eccentric
    - Held in the vertical position and three holes were drilled in the mill (required some tricky holding in the vice, but managed to figure out an orientation with the help of shop staff!)
    - Used a slitting saw in the mill to chop the eccentric in half with a clean cut
    - Tapped holes for strap and redrilled through hole on top piece
    - Added 0.02” shims between the pieces and bolted back together
    - Machined the hole using a circular pattern in the mill. Made hole 0.002” larger than the eccentric to keep a close fit. (Used micrometers to measure the eccentric and turns out it’s actually 2.762” instead of the 2.75” called out in the specs… so close!)
    - Eccentric didn’t spin nicely in the strap :( so…. I added a small chamfer on the hole in the strap and now it spins! Still pretty tight, but with a little lapping and some oil added it should work smoothly!


    Wohooo eccentric pieces are almost there! More updates on ignition and eccentric system to come…..

    Facing the strap with a flycutter (fairly tight tolerances here), hold in the vice is slightly sketchy but barely any material was being removed so it worked fine!



    Tragedy of cutting the beautiful piece in half:



    Machining the hole in the eccentric strap:





    Three eccentric parts nearing completion! You can see the eccentric strap has a slight divot from the casting, but it shouldn’t be a huge issue. (The faint vertical scratch was used to align the piece when clamped vertically)


    Here she is all together:





  25. #60
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    Default Re: Atlantic Make and Break Fabrication Project @MIT

    Nice work!

  26. #61
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    Default Re: Atlantic Make and Break Fabrication Project @MIT

    One of my favorite threads on here, love seeing all your progress, thanks!
    Chris
    ____________________________
    Current:
    Tern, a William Atkins Pixie. Builder: Jeff Stobbe, 1997. Completed restoration 2016
    Sparkle, not a Herreshoff 12-1/2, same but stretched to 14-1/2. Builder: Jeff S, 2013.

    Previous: Ydun, Folkboat US 88, owned 1997-2000 ish, Berkeley, CA Sailed her one weekend, worked on her the next. Builder: Borresen, 1950 (Denmark)

    Spokane, WA.
    Row, sail and sleep on the beach around Lake Pend Oreille, usually near Garfield Bay, Idaho.

  27. #62
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    Default Re: Atlantic Make and Break Fabrication Project @MIT

    Hello everyone! Sorry I haven't posted in a while. I wanted to have the piston successfully cast and it took quiteeeeeeee a long time. There was so much to learn and I'm still learning. It's a burdensome but extremely rewarding process. Anyone on the team can vouch for my beaming smile when I finally got a good cast. So here goes.

    To say the least, the piston is not an easy cast (even though it may seem like it), and it is just the beginning. The cylinder beats the piston in terms of volume, complexity, and number of cores, so getting the piston to be cast correctly is vital to the understanding and success of the cylinder cast. The first attempt to create the piston was a failure, and so was the second and third. The piston was to be cast without a parting line, placing the sprue directly on the center of the top surface. The pattern and core mold for the piston were 3D printed. Each was split in half and each half took two days to print, so do not underestimate the amount of time it takes to print parts. The two halves of the piston pattern then needed to be epoxied together and clamped overnight. The core mold had alignment pins on both halves that allowed the mold to be put together easily and accurately, and also helped the halves from bursting open when being packed with sand.


    Mold for piston core with an alignment feature.


    Pattern for the piston.

    First piston attempt:
    First, a flask was created to accommodate the size of the piston and a lip was used in order to help keep the sand in the flask. The flask was a 13” cube, so that at least two inches of sand would exist between the pattern and the flask in any given spot. The flask was made of ½” plywood and did not need any reinforcements, but handles were added later to make carrying the flask easier. For a flask of a larger size, reinforcements must be made in order to keep the sides of the flask from bowing because that movement could ruin the cast.

    The core print was originally attempted using CO2 sand, but it was not strong enough and easily broke. The decision was made to use no bake resin sand that solidifies much harder than CO2 sand. The resin sand was created in 2 kg batches. For each batch of sand, the resin and catalyst consists of 3% of the weight of sand – in this case 60 grams. The formula calls for 2/3rds resin, which is mixed in first, and 1/3 catalyst, which gives 40g of resin and 20g of catalyst. Less catalyst can be used in order to slow the curing time of the sand. There were about 7-10 minutes of working time after the catalyst was mixed in and separate batches of sand don’t necessarily bind together if too much time separates them. Remember that with resin sand, time is always against you. The resin sand was patted down on the inside of the core mold as to leave the core print hollow to allow for venting. After letting the core print cure, the mold was opened – however the core broke at the interface with the aligning feature, which made it impossible to cantilever the core into the flask and thus more difficult to align the core print properly. The core print might’ve broke because no powder was applied prior to filling it with sand – this is a very important step and must not ever be overlooked.


    The resin sand was pressed along the inner walls of the core mold in order to make the core hollow.




    Some of the core broke off but it was glued back on with core paste.

    While the core print cured, the flask was prepared. Note that a 13” cube takes quite a bit of time to fill with sand. Green sand was used and put down in layers and rammed until the flask was full. The sprue was then cut in using a copper tube.



    [to be continued]

  28. #63
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    Default Re: Atlantic Make and Break Fabrication Project @MIT

    [continued]

    A vent was then cut in that connected the center of the core print to the top surface of the flask. A base flask (about 13”x13”x5”) was also prepared with green sand and the core print was placed on the center of it. The pattern was removed from the main flask and then the flask was carefully lowered onto the base flask, making sure that the core properly aligned – this was difficult because the flask was very heavy, and it was difficult to see and move the core print while simultaneously lowering the heavy flask. That is why cantilevering the core into the flask was desired.





    Now that the flask was fully prepared, iron was melted and poured into the mold. It was instantly known that the cast failed as all of the iron was consumed. The core was not strong enough and imploded, leaving behind a lump of iron on the base flask. No piston this round.





    [to be continued]

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    Default Re: Atlantic Make and Break Fabrication Project @MIT

    [continued]

    Second attempt:


    Given that the core imploded the last time, the core was filled solid with resin sand using a copper tube to create a vent in its center. The aligning feature now had substantial support, enough to hold up the core print to the weight of the iron being poured. The copper tube was removed once the mold was filled and packed. Since the mold was again not powdered, the core print broke at the interface of the aligning feature and glued back together.





    The pattern for the piston was also cleaned before the 2nd attempt. Plaster was applied and sanded at the seams in order to make it smoother and easier to remove from the flask. Resin sand was applied to the outside of the pattern, after coating it with powder, in an attempt to complete a shell casting of the piston. However, the vertical nature of the piston and the fact that the resin sand begins to cure so quickly made it impossible to create a full shell of the pattern. Once the catalyst is added to the resin sand, it needs to be thoroughly mixed to ensure proper bonding. When the sand turns a light, moss, green it is ready to be packed, but once it reaches a dark green it becomes less workable and won’t bond to new resin sand, and there are only a few minutes in between shades depending on how much catalyst was added. So in the end, instead of a full shell cast, a shell of the aligning feature was created – which was all that was really necessary. It makes it easier to align the core properly and also keeps the green sand from being bumped and destroyed when inserting the core, since the resin sand shell is much more bonded and hard than the green sand.







    [to be continued]

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    Default Re: Atlantic Make and Break Fabrication Project @MIT

    [continued]

    The pattern with the resin sand shell still attached was then packed with green sand in the flask, just like first attempt. The main and base flask were packed and the pattern was removed. The core print was vented through the base flask, unlike the first attempt. Since the core print was broken, the main flask was again lowered on to it. Iron was melted and poured, but again, the cast appeared to not be fully filled.











    Turns out, there was not enough metal poured to compensate for the flash, the sprue, and the spillage! A mistake that won’t be made again. The core did work well however, and the surface finish was good. The surface finish on the outside of the piston was poor, but it was not critical since the piston is turned down.


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    Default Re: Atlantic Make and Break Fabrication Project @MIT

    [continued]

    Third and a half attempt:

    A full shell casting was attempted during this round by creating a small box to fill with resin sand, since patting down sand onto the pattern was unsuccessful. A full shell cast of the piston would create a better surface finish on the outside. However, the full shell was unsuccessful again, but a lot was learned about the resin sand during this process. The resin sand shrinks as it cures, so it if is surrounding a pattern, it will be almost impossible to remove the pattern from the mold. Even after excessive hammering on the copper tube that created the sprue, the pattern would not budge. The box was dismantled and more hammering commenced with no luck. A small hole on the top edge of the pattern was created and hammered and still the pattern would not release. The decision was made to cut half of the top shell off in order to hammer the pattern out more easily, but the entire top layer of the shell broke off. This finally released the pattern, but it was also broken. The mustache shaped feature on the piston was stuck in the resin sand.







    Since the pattern was broken, it needed to be fixed before another pour could occur. The moustache was salvaged and re-epoxied to the pattern. Plaster was then added to smooth out the interface between the moustache and the top surface and dents that were created during hammering were filled in. The top of the pattern was sanded down until smooth, and the pattern was ready to go once again. Upon returning to the shell mold, more cracks had developed and the shell split at the layers. Since the shell mold was still extremely tight on the pattern, the top two layers that broke off were not glued back together to the rest of the shell and this eased some of the friction that was keeping the pattern stuck. In the end, the shell only covered the aligning feature.







    Like during the other attempts, the core print was created using the resin sand. Powder was coating the mold and the print released whole – the first perfect core. This was ideal because the core could then be cantilevered into the flask.

    [to be continued]

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    Default Re: Atlantic Make and Break Fabrication Project @MIT

    [continued]

    Twenty-four pounds of iron were melted to ensure that there would be a sufficient amount, and there was plenty left over. Finally a completed cast of the piston! There is an air bubble on the side of the piston, but it is in the location of the piston rings – the bubble should not hurt the efficiency of the piston since the compression rings should seal around the length of the piston.






    A void had formed from trapped air, which is why venting the casts are important - that was not done for this cast.


    The core came out amazing!


    The differences in surface finish from the green sand (top) and resin sand (bottom).

    Finally a successful cast!
    Most important things learned:
    · Resin sand has a short period of workability
    · Resin sand shrinks
    · Separate resin sand layers usually do not bind well
    · Cores must be hollow and vented but sturdy
    · Resin sand creates a much better surface finish than green sand
    · Coating patterns with talc powder is a vital step towards a successful cast
    · Proper draft is critical and all angles should be filleted if possible
    · Vent your parts! (so that bubbles do not form)

    [to be continued]

  33. #68
    Join Date
    Sep 2015
    Location
    Cambridge, MA
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    18

    Default Re: Atlantic Make and Break Fabrication Project @MIT

    [continued]

    Now machining of the piston begins. The piston was secured to the lathe using the core. It took a long time to center it on the lathe, but it was finally successful. Only 1/8" was added to the diameter of the pattern, so there was not that much extra material to work with, which we why we spent some extra time centering it on the lathe. The farther away from the top, the more material there is since draft was added to the pattern to ease its removal from the flask.

    As the piston was turned down, it came to our attention that venting is absolutely necessary. But that's how we learn things! The surface has some pits in it, we are not sure whether this will be detrimental to the efficiency of the piston yet. But this is the piston we have now, maybe if there's time I can make another, but I need to focus on the manifold now.

    The piston was also sanded down to smooth out the surface. And now we are up to date on the piston progress!

    Does anyone have suggestions for piston ring manufacturers? The atlantic piston calls for rings that are 13/32" which I know is absurdly thick for modern times, but we will just stack thinner rings. They are 7/32" deep and have to fit in a 4.5" cylinder bore.







    Over and out,
    Sam

  34. #69
    Join Date
    Sep 2010
    Location
    Melbourne mostly, Australia
    Posts
    2,514

    Default Re: Atlantic Make and Break Fabrication Project @MIT

    just discovered this thread ...... fantastic

    please keep up the documenting

  35. #70
    Join Date
    Jun 2003
    Location
    Central Coast, Ca
    Posts
    32,308

    Default Re: Atlantic Make and Break Fabrication Project @MIT

    Piston rings...
    You may be able to find some (obsolete) thicker rings in the exact size that you want, but I haven't had much luck. I had a source about 30 years ago, an engineer at Grant piston rings and they had very limited old stock, but I think any ring Manufacturers in the US are long gone.

    You may have to make them. Usually the rings in a two stroke cycle engine like that have an interference problem with the ports and the ends of the rings. To prevent rotation, rings are pinned to the piston at the end gap in each ring, which might even be a diagonal cut. That sort of demands a slightly thicker ring than normal. It might be easier to make your piston fit the rings than making rings to fit your piston, but either way I think they will have to be pinned.

    (I like making piston rings, usually they can be made from section of cast iron pipe or a fitting. There are some subtle little details with piston rings, those big thick ones are sometimes od-id eccentric)

    edit to add;
    I am working on similar vintage engine. A bit smaller than yours, 4"x4" - this is sitting on my workbench...

    Last edited by Canoeyawl; 04-23-2016 at 11:08 PM.

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