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Author Topic: Gift Card Bell Cranks  (Read 2538 times)

Offline goozgog

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Gift Card Bell Cranks
« on: April 26, 2018, 09:49:51 AM »
  There has been some interest in the bell cranks
I make for my 1/2A planes out of plastic "Gift Cards",
so here are a few details to make them easier and
better.
   I make these just because I'm too impatient or lazy
to drive to the hobby shop that really doesn't carry
C/L stuff.
  These cranks are good for planes of about 10oz,
maybe 14 oz with the extra bushing(s) depending
on how they are mounted.
Two layers of card are enough for most 1/2A planes.

  The hard part of making these cranks is scraping
the graphics off of the cards. I've tried sanding and
solvents but the easiest way is to scrape with a
sharp knife. This needs to be done on the surfaces
that will be Cyano'd together but the rest can be
left with the printing.
   The plastic the Gift Cards are made from is resistant
to Acetone and Lacquer Thinner and that helps to get
the surfaces clean before bonding the laminations.

The pictures say it all.

   I cut out one lamination with scissors and drill
the holes. Radius's can be accurate if you use a
washer as a guide centered over the holes.
De- burr everything then use CyA to bond it
to another scraped card. Drill through the second
layer using the existing holes as a guide.
Scissor and sand until it's pretty.

  The picture shows a disk of card plastic bonded
to act as a bushing. This isn't necessary for most
1/2A's but it's easy to do for added strength.
  I use a 4-40 bolt with a smooth shank as the axle.

Metal lead outs don't  seem to saw through the
plastic and Spectra lines aren't cut if they're just
tied through the holes.
Smooth everything and use your judgement.

Cheers! - K.




 
Keith Morgan

Offline goozgog

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Re: Gift Card Bell Cranks
« Reply #1 on: April 26, 2018, 10:57:26 AM »
I forgot to say that this bell crank is

1-1/2" wide x 1/2" arm. ( 38mm x 13 mm)

  It weighs 0.1 oz with the bolt and nut (2.5 gm)
but without the pivot metal, it is so light my
scale can't register it.
Keith Morgan

Offline Chancey Chorney

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Re: Gift Card Bell Cranks
« Reply #2 on: April 26, 2018, 09:18:16 PM »
Nice Keith. Thanks for taking the time to do a 'tutorial' of how you make your 1/2a bellcranks. Will be trying one out next build! Just one question regarding the laminating process. Do you clamp the two pieces between something for a bit till it dries? Have you ever tried or used epoxy?

Offline 944_Jim

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Re: Gift Card Bell Cranks
« Reply #3 on: April 26, 2018, 09:31:45 PM »
"Impressive," in a Darth Vader voice. I wish I'd learned this one a year ago. It just obsoleted my stash of vintage aluminum 1/2A bellcranks!

Offline goozgog

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Re: Gift Card Bell Cranks
« Reply #4 on: April 27, 2018, 02:45:46 AM »
Good morning Chancey,

   Nope. I have never tried epoxy. I use
the cheap cyano I buy at Dollarama.
  After I have made one side I make sure
it doesn't have any burrs sticking up then
wipe both surfaces with acetone or lacquer
thinner.  I use a good amount of CyA
because it gives me a few seconds to float
into position.  The layers bond before I
would ever have a chance to clamp it. ( Jed ! )
  Loved your air car BTW.

   Jim. If you have a stash of the aluminum
cranks from Scientific or Perfect, polish them
and BS about " I only fly with silver controls".   <=

Cheers! - K.

Keith Morgan

Offline Paul Smith

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Re: Gift Card Bell Cranks
« Reply #5 on: April 27, 2018, 04:57:53 PM »
The trash bin at any trips F2d event is a good source of bellcranks, leadouts included.
Paul Smith

Offline James Holford

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Re: Gift Card Bell Cranks
« Reply #6 on: April 28, 2018, 11:05:01 PM »
And here I went and bought 2new in the pack Carl Goldberg plastic 1/2a bellcranks for like 5 bucks on ebay......

Really cool!

Sent from my SAMSUNG-SM-G891A using Tapatalk

Jamie Holford
Baton Rouge Bi-Liners
Lafayette, La
AMA #1126767

Offline goozgog

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Re: Gift Card Bell Cranks ( add Jan 2019)
« Reply #7 on: January 24, 2019, 09:09:34 AM »
  The picture shows the "Gift Card" bell crank
I made for the FW190.
   It's 2-7/8" x 0.5" between holes mostly because
that span fits in the wing.
  I didn't scrape the graphics off the card this time
and I just sandwiched it between the two layers.
I did a test with CyA and it bonds the plastic well.
  These cranks are decently stiff and strong but
because this will be buried in the plane I took the
time to add bushings made from some K&S
aluminum tube. Probably wasn't necessary.
  The entire assembly with the axle and spacers
weights 2 gm - 0.1 oz.
Keith Morgan

Offline Skip Chernoff

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Re: Gift Card Bell Cranks
« Reply #8 on: January 24, 2019, 11:19:44 AM »
Very resourceful,they look just fine!

Offline goozgog

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Re: Gift Card Bell Cranks
« Reply #9 on: January 24, 2019, 03:17:55 PM »
They are better than anything else that  I have
found that size Skip.

 The bushings were very easy to make..  I just
cut short lengths of aluminum tube and "riveted"
them on using a center punch.
The K&S tubing comes annealed so it is very soft.

  I have a sailor's distrust of dissimilar metals,
so time will tell if the aluminum will bind on the
polished steel axle. I gave it a tiny smear of
silicone grease.

-K.
Keith Morgan

Offline Tim Wescott

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Re: Gift Card Bell Cranks
« Reply #10 on: January 24, 2019, 03:26:19 PM »
Unless you're flying in salt spray it'll probably be fine.  I've been bushing my big-plane bellcranks with aluminum running on music wire, and haven't had a problem.  Except for my longest-lasting "big-plane" bellcrank, which is 1/8" thick phenolic with a 5/32" hole drilled in it, riding on the smooth shank of an 8-32 machine screw.  600 flights, no sign of trouble with the control system.
AMA 64232

The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.


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