Announcement

Collapse
No announcement yet.

ASH-31 Retract Repair

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • ASH-31 Retract Repair

    I've been flying my H Model 40% ASH-31 for about 4 years now. At close to 50 lbs the retract takes a lot of force on take-offs and particularly on the landings.

    The airframe has a very robust retract unit with a friction brake as well. 2 servos are used for this, one for the retract mechanism and the other for the brake. These are mounted onto the sides of the retract plates using carbon fiber/fiberglass/resin servo mounts. The one for the brake is not put under a great amount of stress, but the retract servo and its mount do take quite a bit of force.

    The resin mount for the retract servo gave way while I was in Cumberland, giving me a great opportunity to make a new one. The forward arm of the mount failed where the screws that hold the servo go through. Please note this is not due to any issue with the workmanship of the airframe or the servo frame, but rather my use and wear due to 4 years of take-offs and landings.

    Here are a couple pictures of the resin mount (you can see the cracks on the second picture on the arm on the left):

    Click image for larger version  Name:	02.jpg Views:	1 Size:	144.5 KB ID:	18482

    Click image for larger version  Name:	01.jpg Views:	1 Size:	107.5 KB ID:	18483

    I picked up some right angle aluminum stock from Online Metals:



    They sell stock in small to large sizes, making it easy to get pieces that are only 12" in length. The angle stock I purchased is 2" x 2" x 0.1875" thickness:

    Click image for larger version  Name:	03.jpg Views:	1 Size:	127.5 KB ID:	18484

    I was very fortunate a year or so ago to have a friend offer me a Sherline metal lathe and metal mill. This was a perfect time to get them out to create a new mount for the retract servo:

    Click image for larger version  Name:	04.jpg Views:	1 Size:	67.2 KB ID:	18485

    I used an end mill to create the open space for the servo in the frame. I did take out excess aluminum with a bandsaw prior to milling the final frame, making completion take less time. In addition to milling the width and depth of the servo space I also milled the width of each long edge/side. It is amazing how precise the mill is, allowing the creation of parts that have very close tolerances and fit.

    After the correct milling for the width and depth of the servo was completed I then used the servo to mark the correct placement of the servo mounting screws. I changed the end mill cutter over to a chuck and drill bit and was able to drill out the initial holes very precisely. These were then tapped for cap head bolts for the servo to be held in by.

    Two holes were also drilled into the side plate where it is attached to the retract frame. These are the countersunk for the mounting screws to be flush with the servo frame and not interfere with the servo.

    The servo was then mounted and I put it in place with 4 cap head bolts, using nylon insert lock nuts underneath to make sure it won't come loose:

    Click image for larger version  Name:	06.jpg Views:	1 Size:	86.1 KB ID:	18486

    Click image for larger version  Name:	05.jpg Views:	1 Size:	114.0 KB ID:	18487

    Click image for larger version  Name:	07.jpg Views:	1 Size:	82.2 KB ID:	18488

    Click image for larger version  Name:	09.jpg Views:	1 Size:	100.2 KB ID:	18489

    Click image for larger version  Name:	08.jpg Views:	1 Size:	104.0 KB ID:	18490

    After this was completed I then bolted it to the side frame of the retract and then re-attached the servo arm and link for the retract. A few minor adjustments to the servo throws and it works perfectly:

    Click image for larger version  Name:	10.jpg Views:	1 Size:	39.7 KB ID:	18491

    Click image for larger version  Name:	12.jpg Views:	1 Size:	116.9 KB ID:	18494

    Click image for larger version  Name:	13.jpg Views:	1 Size:	111.2 KB ID:	18493

    Click image for larger version  Name:	11.jpg Views:	1 Size:	138.3 KB ID:	18492

    Tomorrow I'll reinstall the retract unit back into the fuselage and complete the work on putting the gear doors back in place. Waiting on a couple springs that should be here tomorrow or Wednesday and then it will be ready to fly again.
    Last edited by BobM; 08-01-2017, 03:09 AM.

  • #2
    looking good there Bob...very solid going that route. The spring company you mentioned in other post looks great...I poked around the link for a while...always hard to find the exact spring and size needed...maybe not anymore!

    ....what tire company is that?

    see ya next meet....

    Matt

    Comment


    • #3
      Hi Matt,

      The tire and hub is original from H Model that is specific for their 40% sailplanes.

      I was looking at it today while getting everything back in place and it looks like it would be possible to find the right kind of rubber/dense foam and then turn a new tire to fit the hub correctly if needed. I'll have to do a little research and find a foam supplier that I can show the tire to, then pick up some similar density foam/rubber and turn a couple replacement tires in case I need one.

      The hub is another story. There are several companies out there that make various aluminum hubs, but I'm not certain of the source for H Model. I would guess H Model can sell replacement tires and hubs directly if contacted (I have been able to contact Radim through email and get some of the small replacement parts as needed over the past couple years), but the shipping costs from Europe can be a little expensive.

      Comment


      • #4
        thanks for the info Bob....might try to get a FEMA wheel that Len mentioned....need a 4.5inch one if anyone has one to sell by chance...

        Comment


        • #5
          Matt........the website for FEMA is:



          You can look through their catalog and see if you can find the wheels and other parts you might need.

          Comment


          • #6
            retract is 9813A
            Len Buffinton
            Team Horizon Hobby

            Comment


            • #7
              That's a nice repair! Wonder where the next 'weak link' will be?

              Comment


              • #8
                Thanks Mike.....looks like the problem may have been the brake cable hanging up on the retract former when the gear cycles from the up position to the down position.

                I hadn't noticed this until I finished up the repair and reinstalled the gear....when I was cycling the wheel the cable caught the former and stalled out the gear...luckily the OCP circuit stopped the power to the servo quickly and I was able to figure out a way to guide the cable effectively, keeping it from catching on the former now (a couple large zip ties strategically placed worked wonders).

                The doors and springs are set, everything is back together and working great....looking forward to getting back in the air and trying the short tips a bit more.

                The weak link seems to be me.........most of the time !

                Comment


                • #9
                  glad you figured out the main issue with the hanging up cable...thanks for the info guys on the wheels

                  Matt

                  Comment


                  • #10
                    'The weak link seems to be me.........most of the time !' That's funny! Anyway... glad it's fixed. I love watching those big glass slippers fly. Can't wait until my skill set is up to flying one!

                    Comment

                    Working...
                    X