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Thread: Herreshoff Steam Engine Fabrication @MIT

  1. #36
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    Default Re: Herreshoff Steam Engine Fabrication @MIT

    Quote Originally Posted by kbowen View Post
    Years ago I read in a biography that Herreshoff was already inventing his own valve opening curves before going to MIT and astounded his classmates by commenting that he had already used one of the curves that the Professor was discussing. True / False?
    I also have a question, we're these splash pan lubrication on the cranks, or pressure with reuse, or pressure one-shot? I remember as late as the early 60's the Kahlenberg diesels on the Great Lakes were one-shot systems and left an oil slick whenever they pumped the bilge.
    Ken
    Regarding the valves and MIT, I asked Kurt (Hart Nautical Museum) and this was his reply:
    Like many times, story is partially true.

    A detailed handwritten account of this is in the minutes of the MIT Society for the Arts in MIT archives. The minutes recount that NGH demonstrated some sort of rotary valve at a formal presentation of a Society meeting. This was a sort of adult education forum early in MIT history. They had some very big names and it seems quite unusual for a student to be a presenter. Story L.F. Herreshoff tells in his book is that N.G. showed his professor a curve he had used to design a valve for an engine (LFH says curve used for valve settings for a rotary engine somewhat like small model airplane engines much later and that he was 16 at the time). Apparently, the analytical geometry professor was somewhat amazed because curves were not used for that purpose then and invited NGH to bring the engine and demonstrate for MIT Society of Arts meeting, which was attended by President Barton Rogers!

    Kurt has the written meeting minutes, and when I have time I may try to decipher the technical information.

    Re: lubrication. I have been a little perplexed by this myself. The base of this particular engine has an open bottom, so no sump or splash. The upper halves of the main journals do seem to have a built in reservoir with holes through the shell to the babbitt. It looks like it would make a mess, and I'm not convinced my understanding is correct.

  2. #37
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    Default Re: Herreshoff Steam Engine Fabrication @MIT

    Quote Originally Posted by DoctorB View Post
    Re: lubrication. I have been a little perplexed by this myself. The base of this particular engine has an open bottom, so no sump or splash. The upper halves of the main journals do seem to have a built in reservoir with holes through the shell to the babbitt. It looks like it would make a mess, and I'm not convinced my understanding is correct.
    [/FONT]
    The engines with unenclosed cranks always seem to have open base bottoms. Drip pans are installed separately beneath the engines. There's a reason the lowest rate in the engine room just below the "oiler" is the "wiper," or so it would seem.

  3. #38
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    Default Re: Herreshoff Steam Engine Fabrication @MIT

    Thanks Bob - great piece of information. Funny you mention the oiler. One of our techs was just talking about the oiler position at the MIT power plant.

  4. #39
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    Default Re: Herreshoff Steam Engine Fabrication @MIT

    Now that I have photobucket out of my life, I can start getting caught up on posting. Here's a photo-synopsis of the cylinder:

    CAD was shown from post 24, and I'm reposting the cylinder patterns and core boxes:

    Patterns being CNC'd. This is the first adaptive tool path for fast material removal.


    After a few more toolpaths, the final result:



    Coreboxes using the same CNC method:


    I'm particularly fond of the way Colleen jigsaw puzzled the core box for the cavity that connects the valve cylinder to the power cylinder


    Last edited by DoctorB; 09-23-2017 at 07:16 PM.

  5. #40
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    Default Re: Herreshoff Steam Engine Fabrication @MIT

    more...





  6. #41
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    Default Re: Herreshoff Steam Engine Fabrication @MIT

    packing the flask and placing the core:






    and voila:


    We only run the program in the spring, but I have to complete this engine by end of May, so some the staff here and I are going to do work on it ourselves along with one of my students. There will be plenty for the students to do once the course starts up again. I'll take some pics of the machined cylinder later this week. There are some defects on the the flange, and other places here and there, but they seem mainly cosmetic and some grinding and brazing will clean things up. We already bored the two cylinders and faced the top and bottom. There were no voids to speak of. So far so good.
    Last edited by DoctorB; 09-23-2017 at 06:18 PM.

  7. #42
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    Default Re: Herreshoff Steam Engine Fabrication @MIT

    Before one of fall classes gets into full swing, we thought we'd take a stab at finishing some parts. The cylinder is now "done", awaiting honing, filling some areas, and grinding and filing casting artifacts.
    After facing and boring most of the way, Bill made a fixture to locate the bores. Then he flipped the part over and completed them from the other side. check out the tap handle for the 1" NPT steam inlet.
    Notice the chatter marks from the long boring bar. We'll address that later.





  8. #43
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    Default Re: Herreshoff Steam Engine Fabrication @MIT

    DoctorB, how do you get started with the facing on a rough casting? I've always been curious how that works, without any clean datum points to begin with.

    Pete
    Don't underestimate the power of stupid people in large numbers!

  9. #44
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    Default Re: Herreshoff Steam Engine Fabrication @MIT

    Quote Originally Posted by epoxyboy View Post
    DoctorB, how do you get started with the facing on a rough casting? I've always been curious how that works, without any clean datum points to begin with.

    Pete
    Figuring out "where to start" is sometimes a head-scratcher. The decision largely depends on the relationship among the machined features. In our case, the relative location of the bores was important, as was perpendicularity with the flange and position of the bolt pattern. We simply hand ground enough of the flash and crap on one face - enough for the cylinder to stand upright without wobbling and pointing vertically (measured with a square) - and clamped it to the mill. Then we faced the top, removing a minimum amount of material, establishing a datum. Once we had this datum, the part was flipped over again, and fully faced the flange, bored the cylinders, and drilled the bolt pattern. Flip and repeat.

    No doubt, raw castings start as blobs. For a one-off like this, we don't worry about fixtures. We size it up, shrug our shoulders, and go for it.

  10. #45
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    Default Re: Herreshoff Steam Engine Fabrication @MIT

    Anyone have any great ideas or experience related to forging connecting rods? Our hammer isn't large enough to die forge the whole rod.

  11. #46
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    Default Re: Herreshoff Steam Engine Fabrication @MIT

    Herreshoff had the advantage of having his laptop located between his ears! The man was amazing in his ability to visualize that which was needed without a calculator or drafting table. When we first started working on "Vapor", LFH was still alive. He confessed to me, during a phone conversation, that his father was the only person who could answer some of the questions we had about the valving. What an amazing project you people at MIT have taken on! Bravo! "Vapors" crank is splash lubed.
    jay
    Last edited by Jay Greer; 10-12-2017 at 12:13 PM.

  12. #47
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    Default Re: Herreshoff Steam Engine Fabrication @MIT

    Core box and patterns for the exhaust cylinder are ready. We might pour tomorrow.






    Using removable end plates makes removal of the core easier. I ran the piece through the table saw with a 1 1/2 degree blade angle to get the necessary draft. It also, of course, matches the draft of the pattern's core print. The are MDO - super smooth and flat.

  13. #48
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    Default Re: Herreshoff Steam Engine Fabrication @MIT

    Here's our first attempt at packing the flask for the exhaust cylinder. I like how the runners connect to the flanges, but realized that it would be hard to vent the core because the sprue is too close to the core print at the steam exhaust flange. So rather than continue, executive decision was made to repack and move the sprue to other side of the cylinder.


    Second packing. The sprue was moved to the far side of the cylinder (bottom right), to permit venting of all three core prints. Notice the tiny vent holes on the cope. We've learned that this is essential and have developed this habit (we do it with welding rod) - no reason not to vent. Our friends at Lunenburg Foundry turned us on to generous venting.








    Notice the "S" mark for sprue. Do this to avoid pouring into the core vents - don't ask how I know.

  14. #49
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    Default Re: Herreshoff Steam Engine Fabrication @MIT

    Fascinating to watch you progress!
    Jay

  15. #50
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    Default Re: Herreshoff Steam Engine Fabrication @MIT

    Quote Originally Posted by Jay Greer View Post
    Fascinating to watch you progress!
    Jay
    Yes, indeed!
    There is nothing quite as permanent as a good temporary repair.

  16. #51
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    Default Re: Herreshoff Steam Engine Fabrication @MIT

    Thank you for posting...fascinating stuff!

  17. #52
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    Default Re: Herreshoff Steam Engine Fabrication @MIT

    I busted out the exhaust cylinder from the flask and ran it over to our friends at MIT Central Machine to clean it up and fill some voids at the flanges. It seems that the lowest part of the mold is a great collector of crap, creating pits and voids. Instead of recasting the part, central machine welded in some filler, ground the excess, and generally cleaned things up. Moving forward, we're going to make better wells near the sprue and runners and may even add wells at the lowest-most areas of the molds, in the areas near flanges, for instance.

    One awesome artifact is that the core print leaked and iron filled the core vent, hence that weird internal tee thing - the part that makes the cylinder look like it's throwing up (or worse). I hate to cut it out because it's such a great teaching piece. Notice the machining marks from the pattern - those are residual marks from a scalloping operation using a 3/16 ball end mill. We'll finish machine the part in the lab - facing the flanges and adding a bolt pattern to the exhaust port...and cutting out that tongue thing.







    Here's a money shot of the cleaned up main cylinder. Notice the oops on the bottom threaded hole. No big deal.


  18. #53
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    Default Re: Herreshoff Steam Engine Fabrication @MIT

    Next up: One of our rising seniors makes the column and I'll make the bed plate.

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