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Author Topic: Pull Test? How does your club handle this task?  (Read 2041 times)

Offline frank mccune

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Pull Test? How does your club handle this task?
« on: March 23, 2015, 06:47:59 AM »
     Hello All:

     As Safety Officer of our club, I am attempting to formulate a method to perform a pull test when we fly our airplanes.

     The most simple way to do this is to use the formula of pulling ten times the model's weight on all of the control elements.

     Any suggestions as to how to do this?

                                                              Tia,

                                                              Frank McCune
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Offline Bob Reeves

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Re: Pull Test? How does your club handle this task?
« Reply #1 on: March 23, 2015, 07:59:31 AM »
Well if you want the most sophisticated pull test machine in existence you can build one like we use in Tulsa. Just need someone that can weld and do a little machine work. We built 3 just so we would have one available for each pit area. Operation is as simple as it gets, pit boss straps the handle into the leather holder, asks the pilot what his airplane weighs, sets the counter weight to the airplanes weight and pilot pulls till the flag drops.

http://www.somethinxtra.com/Public/PullTestMachine.pdf

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Offline bruce finley

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Re: Pull Test? How does your club handle this task?
« Reply #2 on: March 23, 2015, 11:13:43 AM »
That is so cool bob
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Offline Motorman

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Re: Pull Test? How does your club handle this task?
« Reply #3 on: March 23, 2015, 05:31:44 PM »
Fish scale.


MM
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Offline Andre Ming

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Re: Pull Test? How does your club handle this task?
« Reply #4 on: March 24, 2015, 04:45:12 AM »
Re: Tulsa Gluedobbers' Pull Test Stands...

They are SOOOO easy to use and SOOOO cool and sophisticated.

Even a moron from eastern OK can do it.  LL~
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Offline john e. holliday

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Re: Pull Test? How does your club handle this task?
« Reply #5 on: March 24, 2015, 12:53:45 PM »
If the club could put price on them, they might sell a few.   I don't have the equipment or skills to make one.
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Offline Avaiojet

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Re: Pull Test? How does your club handle this task?
« Reply #6 on: March 24, 2015, 01:01:03 PM »
Calibration?
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Offline Tim Wescott

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Re: Pull Test? How does your club handle this task?
« Reply #7 on: March 24, 2015, 01:59:20 PM »
Quote from: Avaiojet on March 24, 2015, 01:01:03 PM
Calibration?

THIS IS A GUESS:

If the scale is placed so that the center of mass of the slider is 6.4" from the pivot when the pointer is at 17lb, then calibration should consist of pulling some test weights with a scale, and adjusting the weight of the "approximately 30 pounts" weight until things work right.

No one specifies an accuracy for pull testing: In my opinion if you're within a pound you're probably OK, but if you want to be picky you can make sure that all of the weights are "at least", and marginal planes need not apply.
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Offline Bob Reeves

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Re: Pull Test? How does your club handle this task?
« Reply #8 on: March 24, 2015, 02:29:16 PM »
Actually it's all pretty simple math once you know how much the weight weighs and know the ratio of the moment arms. A whole lot more accurate than a spring fish scale with someone trying to react at the exact microsecond the scale reaches the desired reading.

It is impossible to over pull an airplane with our machines, once the weight has been lifted off rest the amount of pull will actually decrease.

The only down side is the complexity and effort they take to build.
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Offline Steve Helmick

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Re: Pull Test? How does your club handle this task?
« Reply #9 on: March 25, 2015, 04:06:30 PM »
NW Skyraiders have settled on using Bow Scales (Cabela's). More portable, easy to adapt, easy to use with the pre-set arrow. We had one of the first of the "pull test machines", but it was a PITA to store and transport. The bow scales hang in our shed at the airport and don't take up much of any space. We could build one like Bob's, but there's no need or inclination.   H^^ Steve
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In 1944 18-20 year old's stormed beaches, and parachuted behind enemy lines to almost certain death.  In 2015 18-20 year old's need safe zones so people don't hurt their feelings.

Offline Tim Wescott

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Re: Pull Test? How does your club handle this task?
« Reply #10 on: March 25, 2015, 04:37:04 PM »
Quote from: frank mccune on March 23, 2015, 06:47:59 AM
     The most simple way to do this is to use the formula of pulling ten times the model's weight on all of the control elements.

Erm -- read the AMA Safety Code, which certainly ought to be the controlling document for a Safety Officer at an AMA sanctioned club?

D. CONTROL LINE
1. The complete control system (including the safety thong where applicable) must have an inspection and pull test prior to flying.
2. The pull test will be in accordance with the current Competition Regulations for the applicable model aircraft category.
3. Model aircraft not fitting a specific category shall use those pull-test requirements as indicated for Control Line Precision Aerobatics.

Short, simple, to the point, and it keeps a speed model from being pull tested at far below what it would be in competition.
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AMA 64232

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

Offline Steve Helmick

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Re: Pull Test? How does your club handle this task?
« Reply #11 on: March 25, 2015, 05:16:04 PM »
While Tim is correct, he's also assuming that Mr. McCune is somewhere in the USA, and we really don't know that. It doesn't really hurt anything to put that in your profile. Come to think of it, we're assuming that Tim lives someplace or other.  VD~ Steve
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"The United States has become a place where professional athletes and entertainers are mistaken for people of importance." - Robert Heinlein

In 1944 18-20 year old's stormed beaches, and parachuted behind enemy lines to almost certain death.  In 2015 18-20 year old's need safe zones so people don't hurt their feelings.

Offline Tim Wescott

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Re: Pull Test? How does your club handle this task?
« Reply #12 on: March 25, 2015, 08:41:15 PM »
Quote from: Steve Helmick on March 25, 2015, 05:16:04 PM
While Tim is correct, he's also assuming that Mr. McCune is somewhere in the USA, and we really don't know that. It doesn't really hurt anything to put that in your profile. Come to think of it, we're assuming that Tim lives someplace or other.  VD~ Steve

I have my location in my profile.  I'm right here!
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AMA 64232

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

Offline Tim Wescott

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Re: Pull Test? How does your club handle this task?
« Reply #13 on: March 25, 2015, 08:49:01 PM »
Quote from: Tim Wescott on March 25, 2015, 08:41:15 PM
I have my location in my profile.  I'm right here!

OK, "Right Here" is a bit misleading.  So, is it better now?
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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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