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Author Topic: Fuel shut off  (Read 440 times)
Dwayne Donnelly
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« on: March 19, 2017, 07:26:17 PM »

The Balsa Beavers Club in Toronto are starting a new event, LA 15 sport scale racing using either a Sig Buster or Shoestring, sounds like fun so I'm going to give it a go, I've chosen the Shoestring. There will be 2 prelims off 100 laps with two pit stops and the final will be 200 laps and 4 pit stops. I'm going to need a shutoff and from what I've been told the one from Brodak would be to big and heavy for a 15, anyone have one for a 15 size plane?
Thanks
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bill bischoff
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« Reply #1 on: March 19, 2017, 09:37:18 PM »

A piece of music wire and a 1/2 A control horn. Light, simple, bullet proof.  Hoff


* shutoff 1.JPG (140.6 KB, 800x600 - viewed 45 times.)

* shutoff 2.JPG (174.74 KB, 800x600 - viewed 51 times.)

* open.JPG (105.17 KB, 640x480 - viewed 44 times.)

* closed.JPG (150.01 KB, 750x563 - viewed 49 times.)
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Paul Smith
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« Reply #2 on: March 20, 2017, 06:03:39 AM »

Right.  Easy enough to make one.  The Brodak unit wasn't all the reliable from what I saw.   Just about anybody can make a contraption with piano wire, wheel collars and a compression spring.


* 20150915_46.jpg (64.12 KB, 555x402 - viewed 45 times.)
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Dwayne Donnelly
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« Reply #3 on: March 20, 2017, 07:01:48 AM »

A piece of music wire and a 1/2 A control horn. Light, simple, bullet proof.  Hoff

So you make a spring doohickey from piano wire and then connect a wire to the pushrod at the bellcrank? So when you give full up it pulls the doohickey out of the 1/2a horn and pinches the fuel line. Genius.  y1 Hoff 
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« Reply #4 on: March 20, 2017, 07:52:51 AM »

No, you pull full down.

MM
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Dwayne Donnelly
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« Reply #5 on: March 20, 2017, 07:59:29 AM »

No, you pull full down.

MM

Right, down, please where did you hook up the trip wire?
Thanks
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bob whitney
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« Reply #6 on: March 20, 2017, 08:02:17 AM »


  shut off on the up line is an accident looking for a place to happen, flew a Barten B tr and as hard as I tried I continuously hit the shut off on take off. not fun
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bob whitney
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« Reply #7 on: March 20, 2017, 08:06:58 AM »



  if u have your control horn on to of the elav u can attatch shut off wire to the push rod ,or add another small control horn to the elav
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Paul Smith
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« Reply #8 on: March 20, 2017, 12:31:32 PM »

Here's the one I was looking for.  Simple, reliable.  About an hour's work.

The only thing a little tricky is grinding a square-edge notch in the plunger wire.  You need to cut the plunger about half way through to give the trigger enough bite.

Also, be sure to have the control horn on top.  That way the pushrod will buckle a little and not have the nose move much when you trigger it.


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* 20170320_6.JPG (310.76 KB, 1901x1340 - viewed 44 times.)
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Paul Smith
bill bischoff
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« Reply #9 on: March 20, 2017, 03:51:13 PM »

Here's a picture showing the installation. If you build your Shoestring with the bellcrank on the inboard side (per the plans) just install a control horn on the top side of the outboard elevator, and run a cable to the shutoff. Small cotter pins stuck into the fuselage make good cable guides as required.

I recommend you check out my Sportsman Goodyear construction article "Margaret June" on modelaircraft.org. For space reasons, only the introductory paragraphs made it into the print magazine, but the entire construction article is available on line. You might be able to get some ideas.

Bill Bischoff


* P1070317a.JPG (521.76 KB, 1280x960 - viewed 56 times.)
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Dwayne Donnelly
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« Reply #10 on: March 20, 2017, 07:03:17 PM »

Thank you so much for all the help, I'll be sure to post pics when i build it, I ordered the kit through my LHS should be here next week.
 y1 Hoff Grin ; Roll
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Mark Knight
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« Reply #11 on: March 21, 2017, 07:43:32 PM »

I've used the 1/16th music wire and 1/2 A control horn for 3 of my Sportsman Goodyear racers like Bill is showing in his plans.  They are very effective and easy to make and easy to adjust.
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« Reply #12 on: March 22, 2017, 10:35:34 AM »

Dwayne, Make sure you put a little shape on the bottom of the wing if not almost symmetrical. The Shoe has a big wing and you don't need all that lift. Flat bottom wing Shoestrings fly nose down and they hunt.

One thing about the "L" slot shut off in the pic above. In the pits, get into the habit of shutting it off by pulling the down line at the wing tip or pushing the elevator down. And when you reset do it from the side. DO NOT get in the habit of reaching under the plane because, one day you will automatically reach for it with the engine running and put your hand right in the prop and a heavy leather glove will not save you. I've seen it happen to some very astute racers. 

Hope that helps,
MM
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Paul Smith
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« Reply #13 on: March 22, 2017, 12:02:14 PM »

True.

And the reset procedure of a simple shutoff may not be optimum is a race.
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Paul Smith
bill bischoff
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« Reply #14 on: March 22, 2017, 02:28:06 PM »

They say you can never make something foolproof... Anyway, we've had no problems or incidents locally. I suppose it's all a matter of what you're used to.
« Last Edit: Yesterday at 10:45:13 AM by bill bischoff » Logged

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