Oberursel 100 HP Engine

Discussion in 'Gallery & Designs' started by Gil, Mar 2, 2004.

  1. Gil

    Gil Active Member

    Joined:
    Jan 25, 2004
    Messages:
    1,981
    Likes Received:
    0
    All Paper Cylinder Oberursel U1 100 HP Rotary Engine

    Hi All,

    One last post for the evening. Line widths were varied and tested on an HP 870Cse inkjet printer. Widths of .005" gave the best resolution without loosing the scale fin count. Background fill is medium gray with all lines (0,0,0) black. Cutout edges were tinted with 70% gray artists felt tip ink pen (tends to show purple/blue in the photo). Top valve cover piece needs to be a adjusted to a deeper gray fill.

    That's it for this evening. Still have one last experiment now that this is done. Pictures if successful, words if it's another learning experience.

    Best regards, Gil

    P.S. Please excuse the fuzzy focus..., it looks better than it does in this picture. A 1:33 J5 is now within this technique as are R2800s....,
  2. rkelterer

    rkelterer Member

    Joined:
    Jan 16, 2004
    Messages:
    250
    Likes Received:
    0
    hi gil,

    to avoid glowing I try to color the white edges always darker than the part's color.

    the cylinders look very good !

    cheers,
    raimund
  3. wunwinglow

    wunwinglow Active Member

    Joined:
    Jan 18, 2004
    Messages:
    1,093
    Likes Received:
    1
    Glowing?!! That's one FAT spark! Remember the high tension leads on these aircraft were usually bare! And no WD40 in those days, either.....

    Tim

    PS Gil, it looks great, can't wait to see a finished engine. I was pondering a P & W for Digital Navys P26, but the shaped cylinder heads over the valve rockers might be a bit tricky.
  4. Texman

    Texman Guest

    Gil,

    Now for the designer challenged amongst us, are you/will you make the files/plans available for others to make their own engines? I think the work you've done is outstanding!

    Texman
  5. Gil

    Gil Active Member

    Joined:
    Jan 25, 2004
    Messages:
    1,981
    Likes Received:
    0
    Texman,

    The complete engine will be deposited in the parts bin when complete. Note that something like a cylinder can be adapted to many other uses, such as Peters' desire to adapt it to an old Henderson motorcycle design. I intend to also include at the very least a Wright J5 for all those fans of the Golden Age. I already have some ideas of how to build the rocker pans and even the head cooling fin arrangements for other more complex radials like the Pratt & Whitney R2800 series. It's really a blast to finally roll one of these things up and it have it look like the real thing in under 2 minutes!

    Thanks! Best regards, Gil

    P.S. Tried steel airbrushed paper tonight. It came out looking incredibly real even if the ink didn't penetrate well. Will have another go at it tomorrow. One other thing before I sign off, the crankcase was begun today...., at least the idea of how the design should go. It will also be "tinker toy" easy to assemble.
  6. Gil

    Gil Active Member

    Joined:
    Jan 25, 2004
    Messages:
    1,981
    Likes Received:
    0
    Hi All,

    Finished all 9 cylinders tonight (bet some of you are as tired as I am hearing about Cylinders. Reminds me of Jim Nunn and tank treads).

    The cooling fin lines are 0.0067 " in thickness exactly! The explanation isn't very long..., that's the way it all worked out after much experimentation. Actually the explanation is fairly technical and has a lot to do with how lucky you can get with Print Drivers. Printout was sprayed with acrylic sealer, cutout and washed with a thin flat black wash to tone down white edges and adjust color and texture. Cylinders were rolled and capped with 4.5 mm leather hole punchouts and allowed to dry. Each cylinder was then mounted onto a tapered Dremel tool mandrel, the top sanded with a very fine nail file, then washed with a flat black acrylic paint and left to dry before being photographed (they were placed on the white card randomly with no posing). When mounted on the engine the seams will be hidden by being positioned on the side. Work on the crankcase, valves and pushrods, spark plugs, propeller hub and propeller can now proceed.

    Best regards, Gil
  7. Sticky Fingers

    Sticky Fingers Member

    Joined:
    Jan 18, 2004
    Messages:
    272
    Likes Received:
    0
    Gil, just a thought, and if this has come up I will retire to the corner like a good boy. What if you would try stacking mutiple dics of idderent size on a mandrel like a paper straw? Of course that is assuming paper straws are still available any where. Doing this would reqiure the making of different size punches and dies and probably be maddening as all get out but like I said "just a thought"
  8. Gil

    Gil Active Member

    Joined:
    Jan 25, 2004
    Messages:
    1,981
    Likes Received:
    0
    Mark,

    Not a bad idea..., and I've tried it. Paper at this scale just doesn't have the rigidity and texture required to look realistic in the application (it also requires a superhuman level of patience). Applyng the idea it at a larger scale where thicker paper can be used does work however. One issue with cooling fins is that most have a varying vertical contour requiring each fin slice to be a different diameter. The simple solution is to cut all to the largest diameter, assemble with spacer disks into the required stack and then sand to final shape on a drill press or lathe (9 more to go and if your entertaining a B-17 with R1820s that's 35 more to go, just kidding). This is where "paper casting" begins to hold its own as a viable alternate.

    If you look at plastic injected molded scale cylinders under 1:24 you'll notice that even the best model kits use several thousandths of an inch recess to simulate the fin contour. The paper technique of printing, sealing with a matte spray followed by a darkening wash after cutting the parts out makes a very realistic cylinder comparable to injected molded plastic. I've been through about 30 to 40 different test subjects and finally came to the conclusion that for the scale involved the above detailed solution is about as good as you'll find. It meets several design requirement criteria; it can be printed on just about any home PC printer, rolled on an easily available bamboo skewer mandrel (3 mm in diameter), and doesn't require any further sophistication in either tool or technique. KISS at it's best!

    Best regards, Gil
  9. Sticky Fingers

    Sticky Fingers Member

    Joined:
    Jan 18, 2004
    Messages:
    272
    Likes Received:
    0
    Gil, I was thinking primarily in larger scales. A 1/4 scale R2800 perhaps. I've always has a soft spot for those since at one time they where built in the facility I work at. 2800 cubc inches, 122 ci per cylinder, pistons like coffee cans. Looked at the book "The R2800, Pratt & Whitney's Reliable Masterpiece" on the SAE web site, 69 bucks :shock:. The idea of turning the cylinders on a mandrel in a lathe is of course an natural. A friend of mine at work is currently working on a 7 cylinder radial as a practice engine with the goal of building a running 1/5 scale R2800.
  10. Gil

    Gil Active Member

    Joined:
    Jan 25, 2004
    Messages:
    1,981
    Likes Received:
    0
    Mark,

    7 Cylinders as practice huh! 1:5 Scale R2800 is huge! 1:4 scale unbeliveable! There's a guy who makes 1:4 scale engines and only manufacturers runs of 1 to 2 thousand and that's it. He always sells out...., you have to plunk down several hundred bucks just to get an order number! Are we missing something here?

    Best regards, Gil
  11. Sticky Fingers

    Sticky Fingers Member

    Joined:
    Jan 18, 2004
    Messages:
    272
    Likes Received:
    0
    Gil, I talked to him about it today and he told me again it is 1/6th as if that makes it any easier. The whole secret to making one of these things is of course fixturing. And careful research. And really knowing what you are doing in a machine shop. And being a wiz at cad. And having a good grounding in metalurgy. And a lot of other things that one never thinks of till they come up. At work things will go in kind of a sine wave of activity. One week things will be a little slow and the next the bovine waste matter will strike the air moving appuratus with a vengence. When things are a little slack the boss may "allow" him to spend some time on this kind of stuff because it keeps his mind sharp and it never interfers with jobs that absolutley have to get done. Right now he is making his own spark plugs. Sure he can buy them but he would rather make his own.
  12. Gil

    Gil Active Member

    Joined:
    Jan 25, 2004
    Messages:
    1,981
    Likes Received:
    0
    Hi Mark,

    That's why some have machine shops at home...., for those projects where nothing but hogging out metal will suffice! NC machining is now cheap enough for homeshops to afford!

    After deliberating with several different design approaches one really took on "a life of its own" and fell naturally into place. It solves many of the problems associated with rolled cylinder type designs and assures exact cylinder orientation, essential for all "round" type engines. The atttached photo shows a trial fit of the cylinders on the main crakcase assembly. Twin rows will be a snap with this method as will inline "V" types. I'm now happy that I took the time to address this area..., it's proved to be very rewarding both in technique and effect.

    Best regards, Gil
  13. Sticky Fingers

    Sticky Fingers Member

    Joined:
    Jan 18, 2004
    Messages:
    272
    Likes Received:
    0
    Gil, what did you use for the crank case? Is it a casting? As far as mandrels go for rolling paper tubes one idea to look into is blank drill bits. Basically steel pins the length and diameter of regular jobbers length drills but with out the flutes. Available in number, letter, fractional amd metric sizes
  14. Gil

    Gil Active Member

    Joined:
    Jan 25, 2004
    Messages:
    1,981
    Likes Received:
    0
    Hi Mark,

    It's made from layers of 1.1 mm illustrator board. I'll post the whole design in a few days which will clarify the construction methods. One thing though, it does simplify the construction such that it's within the reach of every builder.

    Drill stock is great for a set of "sized" diameters..., a letter and numbered drill set makes a wonderful mandrel set. For the Oberurusel though I used simple bamboo skewers which are around 3 mm in diamter and are readily available at low cost (a design requirement).

    Time has been devoted to "messing about" in an effort to develop the type of detail required to complete the engine. A combination of techniques, split between paint and printer, has achieved it. This is an interesting and somewhat involved story unto itself. See how distracting these "little" investigations can be....,

    Best regards, Gil

    P.S. Couldn't leave you guys in the lurch..., the attached photo shows several of the Print/Paint parts work in progress.
  15. Gil

    Gil Active Member

    Joined:
    Jan 25, 2004
    Messages:
    1,981
    Likes Received:
    0
    Hello All,

    Had to rebuild the crankcase assembly as the scale size would not fit under cowl when valve asemblies are installed. The following photographs are self explanatory as regards building steps and actions.

    Several more detail Print/Paint iterations have taken time to obtain just the right look for the forward part of the crakcase which can now be built (spark plugs on this thing are really small!).

    Best regards, Gil
  16. wunwinglow

    wunwinglow Active Member

    Joined:
    Jan 18, 2004
    Messages:
    1,093
    Likes Received:
    1
    Drill blanks make excellent punches too. They usually have one end ground square, so provided you can drill an appropriately sized hole through two registered pieces of rigid material (acrylic and steel is good, as per Mike Holloways Reheat Models punch and die sets) you can make holes and discs whatever size you want. Put your material between the registered plates, line up throught the acrylic, put the punch in the top hole, tap with a light hammer. Job done.

    Tim
  17. Gil

    Gil Active Member

    Joined:
    Jan 25, 2004
    Messages:
    1,981
    Likes Received:
    0
    Tim,

    I've come to the conclusion that die sets are undoubtedly the best tool for small diameter holes. They are expensinve though and generally don't come any larger than 5-6 mm. I have two sets from Waldron Products that cost nearly $100 U.S. which is out of reach for most modelers. I've investigated using brass tubing sharpened on both ends. One end is for ID cuts the other is for OD cuts. These can be used in a small drill press directly or can be mounted on a 1/8" shaft by using the rubber drum mounts for sanding drums. This allows free hand use of a Dremel tool to make holes which is really handy. The total bill for all the brass tubing came to around $26 U.S. I now have a lifetime supply of shortened telescoping brass thin wall tubing and a complete set of hole drills. Keeping the edges sharp is key to clean paper cuts. This was yet another distraction (yad) in the development of the Oberursel which is coming along nicely now.

    Best regards, Gil
  18. Gil

    Gil Active Member

    Joined:
    Jan 25, 2004
    Messages:
    1,981
    Likes Received:
    0
    Crankcase is Fine, Finit, Finumed!

    Hi All,

    Crankcase is now complete. Valves, Plugs, Prop and Hub to go. Has anyone executed a good LMG-08?

    Best regards, Gil
  19. Peter H

    Peter H Member

    Joined:
    Jan 22, 2004
    Messages:
    62
    Likes Received:
    0
    It's impressive Gil
  20. barry

    barry Active Member

    Joined:
    Jan 28, 2004
    Messages:
    2,369
    Likes Received:
    0