I am concerned about my pushrods on my Chrysalis 2 electric. I have not
installed them yet but I am about 90% done with my sailplane.
When I connect the parts together ...the clevis ect. and hold the elevons
flat or parallel with the stabilizer... the push rod is exposed
2 inches from the end of the pushrod guide and where it enters the clevis
rod to be soldiered. Should I put some extra push rod guide tubing
between the end of the pushrod guide where it comes out of the side of the
plane and where it enters the rod that screws into the clevis?
It seems like maybe an inch of extra tubing would help but I'm not sure if I
should anchor it with epoxy.
I am concerned about there being too much sloppyness in the pushrod. The
clevis connectors that came with the kit seem to be a bit shorter than
the diagrams on the plans. Also, how much pushrod should be exposed back at
the servos. I haven't soldiered or crimped anything yet so I wanted to get
your input first. It says in the directions with the pushrods that they
shouldn't be exposed more than 3/4 inch at the fully extended servo.
From : Don Stackhouse
All good concerns. Yes, you need to make sure the pushrods are properly supported, and the unsupported portions at both ends should be no longer than what's require to allow for pushrod travel (so the pushrod ends don't jam into the ends of the casing).
There are a variety of ways to accomplish this. One is to run the casings all the way out to where they have to end in order to clear the pushrod ends, which means they will then be hanging out in space. To fix that problem, you fill in between the loose end of the casing and the fuselage side with scrap balsa, and if you really want to lock things down, you can put a strap of glass tape over top of all that to anchor it to the fuselage,
Another easier option is to tin the cable in the unsupported region, which makes it stiffer. Leave the pushrod unhooked at both ends, pull it aft as far as it will go and tin the aft end, then pull it forward as far as possible and tin the forward end. This is not as good as having properly anchored casing supporting the pushrod in those areas, but in most cases it's enough to get the job done. Another similar option is to get some 1/16" o.d. brass tubing and slip that over the outside of the pushrod to stiffen the unsupported portion. This is a bit heavier and bulkier than just tinning the cable, but the extra stiffness is a good idea.
You could also use some casing glued to the cable to stiffen it. This is lighter, but not as stiff as tinning or using brass tube. Of course you could both tin the cable and use a stiffening sleeve over the outside of it.
Lastly, I am installing the servos with servo tape and following the
instructions in the plans.
Hint: Servo tape generally sticks pretty well to the smooth plastic case of the servo, but not so well to the wood of the fuselage. There are a couple different ways to help that situation. The easiest is to put the servo tape on the servo, remove the backing from the tape on the side that goes against the wood, but just before sticking the servo in position, put dots of medium or thick cyanoacrylate all over the sticky surface of the tape. This will glue the tape firmly to the wood.
Another technique that's a bit slower and messier but works well is to coat the sticky side of the tape with 5-minute epoxy, then stick the servo in place and hold it there until the epoxy starts to set up. The epoxy will end up firmly bonded to the wood on one side of the interface, but the other side will form a smooth surface for the tape's adhesive to grab. Multiplex uses this method for sticking servos to foam surfaces in styrofoam planes like their Twinstar, and it works great on wood surfaces as well.
What's commonly called "V**cro". Unfortunately the folks who own the trademark for the name V**cro (you can fill in the two ** yourself) are rather prickly about folks using that name without proper licensing, so all us folks who have a bad taste in our mouths about trademark lawyers try to use the generic term "hook and loop fasteners".
and where
I can purchase some. Would I glue part of it to the plane and then use the
remaining strapping to secure the different items in the electrical system.
I think I would like to be able to take out the individual batteries etc.
when I needed to. It seems like servo mounting tape would not work as well
if you are going to be taking the different items out of the plane at times.
I've seen strapping that works great for this at places like K-mart. It's about 3/4" wide or so and comes in a roll of about 10 feet. It's a nylon webbing, with the "hooks" on one side, and the soft, fuzzy "loops" portion on the other side. Just cut off a length of it, wrap it around something (like a battery), and where it overlaps itself the hooks will grab the loops and hold firm. Cut two straps long enough to overlap about an inch when you wrap it around the battery. Wrap it with the fuzzy "loops" side out, and wrap it so the overlap is centered on the top of the battery as it will sit in the fuselage, with the straps located along the length of the battery as shown in the plans. Now, mix up some epoxy (5 or 15 minute is fine) and work it into the "loops" of the straps on the bottom and maybe a little bit up onto the sides of the battery. Make sure you don't have epoxy oozing out around the sides of the battery (in fact it's probably a good idea to wrap the battery in plastic wrap before wrapping the straps around it, just in case any epoxy squeezes out into places it isn't supposed to). Stick the battery in place in the fuselage and let the epoxy cure. To remove the battery, just peel apart the overlapped straps and lift the battery out.
One other thing - it's generally possible to slip the battery back in into a slightly different fore-and-aft location than where you put it the first time. Once you have your C/G set properly, use a permanent felt marker to put some reference marks on the floor of the fuselage at the front and back ends of the battery, so you can be sure of getting it back in the same place every time.
Don Stackhouse
DJ Aerotech
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May 17, 2008
