Orlik PBJ-1H Mitchell

Discussion in 'Aircraft & Aviation' started by Bomarc, Jan 26, 2010.

  1. -Jim G

    -Jim G Member

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    This just keeps getting better all of the time! I just love to see this Mitchell going together!
  2. Elliott

    Elliott Senior Member

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    Goodness!, that's beautiful work Mike! What do you use to polish the mold before the superglue coat?
  3. Bomarc

    Bomarc Member

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    Elliot, just because it's handy in my garage, lately I've been using just plane old "Turtle Wax" car wax (the green paste). By the time I sand it down with 600 wet/dry sandpaper, the mold is almost polished already, so the car wax is more than sufficient to put a quick gloss on it with an old T-shirt. Really shows up the defects, which was quite a few with the Milliput, no doubt due to that fact that it has to be kneaded to death to make it work, which probably introduces pockets of air. With fimo (or Scullpey), you can start shaping the stuff right out of the package, less chance of creating air bubbles.

    When it comes time to clean up the clear pieces after final trimming and before I dunk them in Future floor wax, I'll polish them up with this stuff:

    http://bluemagicusa.com/index.php/blue_magic/products/102/plastic_plexiglass_cleaner/

    Stuff works better than anything else I've tried.

    Mike
  4. Elliott

    Elliott Senior Member

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    Thanks Mike! I have read of modelers using toothpaste as a microfine polishing agent, hadn't heard of this one before.
  5. Bomarc

    Bomarc Member

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    I've tried the tooth paste as polish trick too Elliot. That works well in a pinch.

    Last night was spent on the final fitting/cutting of the plastic. In prepping the fuselage opening to receive the canopy, I modified the rear portion where the flat armored glass sits. The model was flat in this area, but there’s a bit of a curve:

    [​IMG] [​IMG]

    Would have been nice if I had noticed this when I was making that tail cone and before I attached it, but what are you gonna do? Added a crescent shaped piece of mat board underneath the lip and built it up with card, using super-glue to join and harden the edge and also to fill in the joint:

    [​IMG]

    Next, using the kit’s pattern for a guide, staked out the lines to cut the canopy with electricians tape:

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    Several light passes with the knife yields a clean separation:

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    Fits OK:

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    Satisfied that’s all I can do with fit, last task for the night was dunk the parts in Future then go to bed (that way I’m not tempted to touch them before they fully dry). How it looks this morning:

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    Don’t know if the improved clarity shows up in the photos, but the Future really makes the parts look transparent. Now it’s framing and mounting for good.

    Mike
  6. Bomarc

    Bomarc Member

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    Work on the gunner's canopy contiues. Framed out the inside using printed sticker paper (red arrows) and doubled up 65lb paper (blue arrows), both printed with the interior green color. Fairly basic, and due to the canopy’s smaller size, pretty quick:

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    Prepped and rehabbed the fuselage opening, reinstalled the side armor, and, as the final gesture before canopy attachment, added the gun sight with reflector (made up mostly of kit parts). From what I can tell, only the reflector was visible to the gunner behind the armor plate. I suppose that’s all you would need really:

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    Using Gator Grip glue, on with the canopy:

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    I like this shot, looks like you’re standing beneath it on the ramp:

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    Fairly easy peasy. Still liking the Gator glue, stuff grabs pretty good. Flat armored glass and external framing tonight, and then it’s on to the last major assemblies of this trek, landing gear! Whoo-hoo!

    Some useful links:

    http://www.gatorsmask.com/gatorglueorder.html

    http://www.ipmsusa2.org/reviews/Products/gator-hobby_glue/gator-hobby_glue.htm

    Mike
  7. Bomarc

    Bomarc Member

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    Amazingly, I actually finished something on time. I hinted before in the preceding post that I would try to wrap up this canopy tonight. Well, lo and behold, I succeeded!

    To begin, I took some 0.030” thick Vivak (thicker stuff that what I use to vacu-form) and shaped a rear armored glass panel:

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    The next few moves were seen on the main canopy work earlier in this thread. Used the sticky back stuff (printed with the appropriate colors) to make the framing for this piece. I double up the stickers so when I cut one, I cut the other to make them identical. This stuff is nothing more than the label material Avery makes for floppy discs (remember those?):

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    Once that was glued in place, started to frame the outer canopy surface as before (strip the paper to make it thin a la Major D's technique, coat the edges, glue in place):

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    Where all this deviated was in the type of glue used. Yes! You guessed it: Gator Grip Glue. Turns out this stuff works well in this application, but I came to see the differences in using it over using the Elmer’s as I did before. Here’s what I think works (but your mileage may vary). Glue in the strips by applying a coat to the back side, and in applying, totally ignore the excess that weeps out the sides:

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    Don’t touch any of it until it dries! Once all the framing is in place, take a piece of wood (toothpicks are good, but I also made a chisel out of 3/32 inch dowel) and scrape the residual Gator glue off:

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    The Gator Glue is brittle, not like the pliable remains of Elmer’s or Aleene’s. It shatters when you scrape it, leaving this “dandruff” behind:

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    But that actually is a plus, since it leaves a clean surface behind. Dust off the remains, and coat the whole with some water to set the edges (Gator Grip Glue is still water soluble). Looks good:

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    Some touch up paint, the final deal:

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    Not too bad. For fun I took a couple of shots of the whole fuselage to date (over the mess of the work bench):

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    Looking more Mitchell like every day, if I do say so myself. Time to clear the decks, there be landing gear to make…….

    Mike
  8. Elliott

    Elliott Senior Member

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    At the moment I can't even come up with anything to say that hasn't already been said. Whatever Peter Taft and Gixergs say goes for me too. You are one talented dude, dude! The open rear canopy makes the interior seem more real to me somehow. It's not a stuffy museum piece locked away; instead it's accessible, as if it's inviting me in to take a look around. Great, great work, my friend!

    Obviously I managed to find a few words to say. :oops:
  9. Bomarc

    Bomarc Member

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    Thanks Elliot. It's all your fault that I opened this canopy in the first place! :p

    But it was a good call. You're right, nothing to hide here, I want it all out in the open. I made this stuff, why wouldn't I want it show it (within reason)? I still get flack to this day for not opening up the cowlings to display the engines. I counter that unless they were being worked on, the cowlings wouldn't be opened! Besides, you see enough through the regular openings anyway. Feh!

    I actually will have to make a new "bubble" for the removable portion of this canopy. The dimensions changed enough after mounting that the piece cut from the base canopy doesn't match anymore. I can use one of the left over canopies to make one more "fitting", as it were.

    Mike
  10. Bomarc

    Bomarc Member

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    Wheel Work.....

    Cleaned off the work space, and printed out a couple of sheets of the replacement wheels and rims I drew up awhile ago in preparation of this event on card and sealed with mat fixative:

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    Glued lighter paper versions on some 0.5mm card for some templates I'll need. Once I'm satisfied that these new wheels go together well, I'll post the PDF up in the downloads section. I guess I'm my own "beta" builder.

    Finally will get to use that fancy circle cutter to the right. I'm liking it! Started to cut discs out of mat board for the core of the wheels, and the cutter makes pretty easy work of it:

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    One thing I like is the ability to cut discs close together, thereby saving me from wasting any more material than I need to. A good thing, as I'm running low on mat board. Just take a previously cut disc, and use it to spot the next one:

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    I've been clamping one end of the board down to keep it from moving as I cut. To cut concentric circles, start with the smaller diameter one and leave it in place as the center for the larger one:

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    For this operation I almost want to have two of these cutters, each set to the different diameters. It slows things down a bit resetting the bade. I guess the answer is to cut a row of the small circles first, then reset and cut all the big ones next. If you take the little red cap off the end of the blade (exposing the other sharp end, careful!), you can squeeze out a 9/16" diameter hole as the smallest it will go. Not bad. I was able to churn out a few dozen discs in no time:

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    Still on my first blade, and even though it's taking a beating cutting this thick stuff, has held up fairly well. The cutter comes with extra blade, and I suppose I can order replacements, but it looks to me that I can use snapped off Tajima* 30 degree blades in it in a pinch. Haven't tried that yet, but could be handy if it works.

    Mike

    *Since starting this build, based on the recommendations of some fellow modelers, the Tajima 30 degree stainless steel knife is my "go to" knife now. I really like this knife. Sorry X-Acto (which had been my old faithful since I was eight years old)!
  11. Bomarc

    Bomarc Member

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    Now that I have enough discs cut in the varying thickness’ and sizes:

    [​IMG]

    I can start stacking and gluing. TIP: Save the cut center discs for smaller wheels on future projects!

    Since the main wheels are rather large in this scale, I decided to assemble them in steps: Two outer assemblies (foreground in the top pic), and a central core. A bolt, nut, and two fender washers makes an excellent press for the center core:

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    Once everything’s dried, added the two outer assemblies. I made one extra (just in case, knock on wood):

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    Same deal for the nose wheel:

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    Nut and bolted the “drive shaft” and created a template to aid in shaping:

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    Started small and shaped the nose tire first using the Dremel tool:

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    Template tells the tale:

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    The bolt I used on the mains was too big for the largest collet of the Dremel, so I had to go to a power drill, set in reverse to spin in the direction that tightens the nut on the “Shaft”. Template checks OK:

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    Before and after pic:

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    Once done with all three, coated the whole with super glue to harden the mat board and help keep it from de-laminating. Gave them a final “spin” with wet/dry paper to make them really smooth:

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    Hopefully, I’ll be spared from having to shape the reserve parts (Ah-Choo!)

    Mike
  12. Bomarc

    Bomarc Member

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    Treads are tough!

    Title says it all.

    So I had some ideas rolling around in my head about how best to cut in the diamond crisscross tread pattern into these wheels. One thing I knew, I would make a computer drawn template to mark the interval of tread, since CAD does such an easy job of dividing (a lost art in machine work actually):

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    The template is included in my wheel update sheet for both nose and main wheel. That was the easy part, now how to actually cut in the treads? My first go around was to make this fixture. This is the “Cutter, Wheel Treads, Model M-1”:

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    This was made from 0.080” (2.0mm) styrene, glued with Testors liquid cement. Makes for a pretty rigid structure, and seemed like it should work. Used it first to draw in the lines to aid in cutting:

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    Then using a razor saw, tried to cut in the groves with the fixture as the guide:

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    Took awhile to get the technique down, which I figured is always the way. The first one of anything is always the trail blazer, and then it gets better. So I painted the wheel up to see how I did:

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    Not as good as I thought. Passable at best, but as can be seen, there were double cuts, off-interval cuts, etc. etc. I could see I had to iron out some issues with the fixture if I was to make a better tread. So, noodling it through last night and this morning, I cannibalized the first fixture to come up with a second generation one. Behold the “Cutter, Wheel Treads, Model M-1-A1”:

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    Easily the most elaborate and over engineered thing I’ve done for this project, but I figured if I can net all the errors from the first attempt, this will be a useful tool for many a future project. Some of the things this rig incorporates to overcome the problems I found in the first: Plate steel saw guide to keep the saw aligned and square, rubber pad at the base of the wheel mount to hold it firm when cutting, and the ability to shift the plane of the saw to the opposite angle using cradles:

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    I tried it on the first wheel and after a few messing around cuts, achieved a pretty straight cut:

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    The test is to see if that’s repeatable. The two pins in the foreground of the pics resulted in those first tentative trials. The metal saw guide wanted to jump out of its cradles as I sawed, so now I pin it into place at the sides.

    Well it looks like I will have to sand/shape that third wheel, but I guess my sinuses will just have to suffer a bit more. Some more trials tonight with any last minute tweaking as required, then I should be able to crank out some treaded wheels…..yeah right!

    Mike
  13. Elliott

    Elliott Senior Member

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    Reminds me of one of those infernal contraptions dentists use. I'll bet that wheel was terrified once it was strapped down. "Now you'll just feel a little sting......" :p

    Actually a clever device. Are you a machinist by trade with lots of cool things that cut, bend, burn and such?
  14. Bomarc

    Bomarc Member

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    No, but I did spend some time in a radiation physics lab as an undergraduate lab assistant. Got to make a lot of test rigs, fixtures, and what not. Those were the days! Sadly, these days, it's nothing more than a work bench, vise, and hand tools in my garage. :(

    Not much progress to report as I spent most of the time cleaning up the resultant mess from making fixtures. I did find time to spin up the third tire (center, shown while the coat of superglue hardens):

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    So I’m pretty much ready to try cutting in tread again. I did take the (now) test wheel and assembled the hub parts to see how it all works. A couple of glitches (nice gap there eh?) but it actually fits together:

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    Compare and contrast:

    [​IMG] [​IMG]

    Close enough. I don’t know where I got the picture on the right, so if anyone recognizes it give me a holler and I’ll credit or delete as required. I’ve since tweaked the drawing sheet and think it’s as ready as it will ever be, so one more test fit tonight, and in the download section it goes.

    Mike
  15. Bomarc

    Bomarc Member

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    Worked the kinks out of the wheel parts:

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    Darken the gray a bit, lighten some of the line weights, and some general tweaking of the parts sheet. Looks like it will fit with the rest of the model (just imagine a strut there holding up the wheel instead of those fat fingers):

    [​IMG]

    PDF is in the Military:Aviation-WWII section of the Downloads area. Enjoy!

    Dress rehearsal is over, time to make some final wheel assemblies....fat fingers crossed!

    Mike
  16. Bomarc

    Bomarc Member

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    I think this new tool’s a keeper. Started slow, but the technique was mastered fairly quickly. The trick was to saw like you mean it, not take little tentative strokes (the tool probably senses fear in those wimpy moves). Here some pics of it in action:

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    Pretty much freed me up to concentrate on spacing. By using a light color piece of card down the exact center, I had a built in center line, which was a blessing as the pencil marks were obliterated in the first pass. I need some work keeping the spacing right, but still infinitely better than the first attempt. The new on the left, the old on the right:

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    So I’m likin’ it. Two more tires to go, then something else, always something else….

    Mike
  17. peter taft

    peter taft Senior Member

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    Hey Mike. The Jigs 'n' Rigs are superb :thumb: You certainly don't cut corners my friend, and with this beauty near to finished, i wonder " what next ? " but then again.....:twisted: :wave:
  18. Bomarc

    Bomarc Member

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    Prototyping is over, time to make some keepers.

    I wanted to make the hubs silver, and I realized earlier in the week, the only way to do that was to print on metallic colored paper. Towards that end, I've added an uncolored version of the rims to my parts sheet. The new, updated PDF has been uploaded to the downloads area

    I didn’t have any metallic silver paper on hand and didn’t want to wait on an order from Red River, but I remembered hearing from someone somewhere that the local craft chains carries some kind of metallic printable paper for scrap booking. At my local A.C. Moore I found this stuff, and it was the last one in silver too! 8 ½ x 11, and about the weight of 110lb card:

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    Here’ the label, that all the info I have:

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    Prints fairly well. All I really wanted was the main hub parts anyway as I figured I could paint the rest with Model Master Aluminum (enamel) and get a fairly good match. So the assembly went pretty straight forward. I’ll just throw the pics out there, should tell the tale:

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    The finished set:

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    I’ve since flattened the bottoms of all the wheels. I don’t like the bulging “flat tire” that seems popular in the plastic model world, but I do like a little “sit” in the tires. Also, I haven’t write much about the nose wheel. Pretty much everything I did on it was the same what was done on the mains, only smaller scale. I did have to make an adapter for the thread cutter to take the smaller wheel, but that was about all that was different.

    A couple of more views, plus some of the ref’s I used to prove I’m not making this stuff up (no, really, I’m not ):

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    Struts and such next, I guess….

    Mike
  19. Elliott

    Elliott Senior Member

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    Really looking good Mike!! Those wheels and tires would make a Mitchell maintenance crew proud! :thumb::thumb:

    I didn't know Elvis assembled landing gear struts before he became famous...:p

    Any idea what the U-shaped metal clip in the middle of the wheel (last picture) was for?
  20. peter taft

    peter taft Senior Member

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    You can't say enough about this build... but wheels that are GORGEOUS in the extreme says a lot for the rest... Cool Mike... Very cool :twisted: