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500 size OH-58D Kiowa Build

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  • 500 size OH-58D Kiowa Build

    A few months ago, I put in an order with PKM for one of their OH-58D Fuselages. I ordered the basic fuselage and cockpit kit, with the tail opening on the left side. I was quite impressed by how it came out of the box. All doors are functional, and it came with a pre-wired nav light on the tail:

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    There are a few geometry corrections that I will be making it this build though. The back of the engine doghouse should be flat, and is rounded off on the model. I will also remove the front doors, since they were almost never attached on operational birds in Iraq and Afghanistan.

    For the mechanics, I will be using a Trex 500ESP with a Hirobo 4 blade articulated rotor head. The biggest challenge on this end will be integrating one of the most distinctive features of the 58D, the Mast Mounted Sight (MMS):


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    The Mast Mounted Sight sits above the rotor head and provides imaging and target designation capabilities to the pilots. Since this is standard equipment, I wanted to incorporate it into my build. After seeing what Steve Hodges did with his Apache, I wondered if the same technique could be scaled down to work on a 500.

  • #2
    There are a few geometry corrections that I will be making it this build though. The back of the engine doghouse should be flat, and is rounded off on the model. I will also remove the front doors, since they were almost never attached on operational birds in Iraq and Afghanistan.
    Why are the back side doors on this thing? got to be hot as @#$@^ looking forward to this build.

    Comment


    • #3
      Originally posted by JFandL View Post

      Why are the back side doors on this thing? got to be hot as @#$@^ looking forward to this build.
      Luckily there is nobody back there to cook in the D model! The back is just a big avionics bay. In this model, I’ll be using those doors to access batteries.

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      • #4
        In order to start getting things ready for the support shaft for the Mast Mounted Sight, 2 bolts had to be relocated. The top bolt (Jesus bolt) that secured the heads, and the lower bolt that secures the main gear. Both of these had to be separated into 2 sets of smaller bolts to let the shaft pass through.

        The stock main shaft is hollow, but certainly doesn’t leave much room to work with. The upper section is 8mm, and the lower section that secures the main gear steps down to 6mm. Both the bolt holes are sized for 2.5mm bolts, and it has a 4mm hollow center:

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        Since the shaft for the MMS has to be bearing supported, that meant it had to be of a 2mm diameter. I found a company in the UK that had the tiny 4mm OD, 2mm ID bearings, and sure enough, they fit perfectly. I then tapped the bolt holes for M3 threads and attached the gear and head with some shorter 3mm bolts. Sure enough, the support shaft now passes through without any issues:

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        • #5
          Ya I guess they need all that for the
          Mast Mounted Sight. All this stuff is way a head of my time. Analog everything in my day.
          nice fit. also learned something.

          Comment


          • #6
            Originally posted by JFandL View Post
            Ya I guess they need all that for the
            Mast Mounted Sight. All this stuff is way a head of my time. Analog everything in my day.
            nice fit. also learned something.
            Thanks, It’s complicated, but definitely cool stuff. Finished up the support shaft for the MMS today by machining a bearing mount in the top of the head. Next step will be a 3D printed MMS and a test flight of the mechanics.

            Also, while doing some research I came across this paint scheme. Definitely going to be my scheme of choice for the complete aircraft. Needs to have “never tell me the odds” painted somewhere!

            Comment


            • #7
              How much power does the OH-58 have today, I seen a OH-58 flying years ago when they were still new. I don't know much about this helicopter but the one I did see only had two pilots in it and looked way under powered.

              Comment


              • #8
                Originally posted by JFandL View Post
                How much power does the OH-58 have today, I seen a OH-58 flying years ago when they were still new. I don't know much about this helicopter but the one I did see only had two pilots in it and looked way under powered.
                The Kiowa was retired in 2017, so not much power any more unfortunately. It did start to get bogged down by the weight of all the equipment and weapons in the last ten years, and was on the ragged edge of power in the hot and high conditions of Afghanistan and Iraq. It was enough that in the early 2000s, The Army contracted Bell to build the ARH-70, essentially a super-Kiowa. Unfortunately, the Bell representative promised the Army it at a price less than we sell commercial 407s for, which was completely unrealistic. It ended up being cancelled, and they retired the 58 with no replacement, saying the Apache could cover for its absence.

                Now, they are asking for a new scout chopper under the Future Attack Reconnaissance program (FARA). They have set some pretty demanding requirements, including up to 200 knot dash speeds. Bell has proposed the Model 360 Invictus to be a contender in the competition. Hopefully, whatever they do pick will have plenty of excess power this time!

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                • #9
                  Wow 200 Knot's the old Super C Ch-47 top speed 187Knot and could push if need be 198Knot but not for long.. Times sure have changed. Lol the UH-1 could only do 68 knots with a load out.

                  Comment


                  • #10
                    Originally posted by JFandL View Post
                    Wow 200 Knot's the old Super C Ch-47 top speed 187Knot and could push if need be 198Knot but not for long.. Times sure have changed. Lol the UH-1 could only do 68 knots with a load out.
                    No doubt, the Chinook was/is certainly a speedy machine! Still making slow progress on the Kiowa, just finished painting the pilot figures today.

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                    • #11
                      Very nice work.

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                      • #12
                        More progress today, mechanics are now converted to CCW rotation and tail flipped to the LH side. Also, just finished up 3D modeling the Mast Mounted Sight, will be printing it out overnight. For the FBL, I put in an order for Spektrum’s new FC6250HX and a Smart ESC. Will be interesting to see how the full integration works with the new system.

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                        • #13
                          Finished printing the Mast Mounted Sight today, and it fits great on the mechanics. Very happy with how it came out, especially after some very lengthy CAD struggles this weekend trying to finish the model. Next, I’m planning to add a servo under the main shaft that will be able to pan the sight right/left in flight. After that, it will just be waiting on electronics for the maiden flight of the mechanics.

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                          • #14
                            Excellent work !

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                            • #15
                              Awesome sauce!
                              TiredIron Aviation
                              Tired Iron Military Vehicles

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                              • #16
                                Originally posted by F106DeltaDart View Post
                                Finished printing the Mast Mounted Sight today.
                                FDD, Just ran across this forum. WOW, is all I have. Beautiful work, Sir. Best, LB
                                Captain: Got any ideas?
                                F/O: Actually not.
                                — Captain Chesley B 'Sully' Sullenberger III and F/O Jeff Skiles—

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                                • #17
                                  Looking really good Michael! This is really shaping up into a nice build.

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                                  • #18
                                    Thanks all, It's getting there! I saw Spektrum changed the ship date of my FBL to TBD now. I'll give them a week, otherwise I may just go with something else and save the FC6250 for another project. In the mean time, I'm debating how many corrections I want to fiddle with on the doghouse. The more I look at it, the more scale issues that I find.

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