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Author Topic: Viko Fuel Shutoff  (Read 1629 times)

Offline Wayne Foster

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Viko Fuel Shutoff
« on: November 21, 2009, 11:27:18 AM »
Hi Guys,

Has anyone got any experience with the Viko Fuel Shutoff.  I got one to play with and have it mounted on one of Viko's planes.  This was easy to do since I had the covering off the outboard wing.

It seems to be very stiff to me and does not Arm and Disarm easily like they show on the website.  Maybe I'm doing something wrong, but if so, I don't know what.

Any help would be appreciated.  I'm using this in a Sped Limit plane.  Will post pictures if anyone is interested.


http://shop.viko-shop.com/product_info.php?cPath=45&products_id=76

Wayne
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Wayne Foster
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Offline Paul Smith

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Re: Viko Fuel Shutoff
« Reply #1 on: November 23, 2009, 07:48:25 AM »
I saw one usage of the Viko shutoff.  It's a powerful pinching device, but the hold open function seemed to be a just a bit over aggressive.

Using a shutoff on a Speed Limit plane is not necessary.  Due to the low speed there is NO DANGER of flyaway and no requirement for a shutoff, and this is the whole reason a lot of people fly the event.

Furthermore, quite a bit of speed and line pull is needed to make ANY shutoff work properly.  Fast Combat planes operate between 115 and 135 MPH.  F2D's go between 95 and 105 MPH (on SHORT lines).

Speed Limit planes fly under 75 MPH on long lines.  It is VERY possible these shutoff will NEVER work with so little speed and line pull.

If you complain to the manufacturer, his PROPER response would be, "I never said they would work under 75 MPH".
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Paul Smith

Offline Wayne Foster

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Re: Viko Fuel Shutoff
« Reply #2 on: November 23, 2009, 09:17:00 AM »
Hi Paul,

I just got this to play around with.  I think you are right that it probably would be flaky at best on the Speed Limit planes.  I hooked up my lines and was pulling much harder than the plane pulls and the device didn't seem to arm.

I really never intended to use it in Speed Limit, just wanted to see how it worked.  I did play around with it some more and found that you could get the binding out of it if you didn't tighten the bellcrank hold down bolt to tight.

Maybe someone has gotten it to work on slower planes.  If so, it would be nice to hear from them.

Wayne
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Wayne Foster
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Offline catdaddy

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Re: Viko Fuel Shutoff
« Reply #3 on: November 23, 2009, 12:09:13 PM »
Quote from: Paul Smith on November 23, 2009, 07:48:25 AM
I saw one usage of the Viko shutoff.  It's a powerful pinching device, but the hold open function seemed to be a just a bit over aggressive.

Using a shutoff on a Speed Limit plane is not necessary.  Due to the low speed there is NO DANGER of flyaway and no requirement for a shutoff, and this is the whole reason a lot of people fly the event.

Furthermore, quite a bit of speed and line pull is needed to make ANY shutoff work properly.  Fast Combat planes operate between 115 and 135 MPH.  F2D's go between 95 and 105 MPH (on SHORT lines).

Speed Limit planes fly under 75 MPH on long lines.  It is VERY possible these shutoff will NEVER work with so little speed and line pull.

If you complain to the manufacturer, his PROPER response would be, "I never said they would work under 75 MPH".


Did you not see the TWO fly aways at Brodaks this past June?
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regards,
Rick"catdaddy"Blankenship

Offline phil c

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Re: Viko Fuel Shutoff
« Reply #4 on: November 23, 2009, 03:16:31 PM »
Wayne, I think they probably used too strong a spring.  Most of the F2D guys are looking for the shutoff to open with 2 g's of force.  That has proven to be enough to shut off under most circumstances and still stay open during normal flight.  I don't have the exact figures, but 2 g's should be no problem for a speed limit plane.  I've used fast shutoffs on speed limit planes and it worked fine.  We don't use a latch mechanism though.  It's easier for the pitman to hold the shutoff open and launch with the pilot pulling hard enough on the lines to keep it open.
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phil Cartier

Offline Paul Smith

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Re: Viko Fuel Shutoff
« Reply #5 on: November 23, 2009, 04:10:14 PM »
Not to say CAN'T WORK on a super-slow plane, but,,,,,

This year I noticed that F2D planes (100 MPH nominal) when involved in a serious line tangle and an airplane got slowed to "maybe 70 MPH", the shutoff shut off, thereby minimizing the harm of the tangle.  So if the initial airspeed is 70-to-75 MPH and the manouvering speed is 50-60 MPH, you don't have much G force or line pull to work with to make an effective shutoff. 

ps:
The Mears shutoff (same principle as the Viko) does not have an arming device, but requires the mechanic to roast his thumb whilst holding the airplane and shutoff, works OK 100% of the time: launch, combat, and cutaway.

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Paul Smith

Offline Wayne Foster

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Re: Viko Fuel Shutoff
« Reply #6 on: November 24, 2009, 09:24:34 AM »
Hi Phil,

I think you may be right about the spring tension.  The fuel tubing that comes on the VIKO pre-made bladder is pretty heavy stuff.  It may take more pressure to close off than say some of the tubing that you sell.

I will play with it some more.  I would like to see a shutoff that incorporates a shutoff to the fuel flow, rather than a pinching of the fuel line.  This might be a little more difficult due to the pressure systems we use.

Wayne
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Offline Davidf2d

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Re: Viko Fuel Shutoff
« Reply #7 on: December 09, 2009, 10:35:06 AM »
If you look at the slot the bellcrank wire rides in, many of the VIKO shutoffs have it on an angle rather than perpendicular.  Just file the forward edge of the slot until the wire can go straight in and out and the force to open it drops a LOT.  The pinch force has nothing to do with the bladder tubing.  Actually, if you test it, it barely closes brand new Dubro neoprene which we usually use for F2D bladders.  I substituted some very soft Sullivan 1/2A tubing and it works perfectly.  At least it does on an F2D plane.
Dave Lovgren
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Offline Wayne Foster

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Re: Viko Fuel Shutoff
« Reply #8 on: December 09, 2009, 11:17:32 AM »
Hi Dave,

I see what you mean about the slot being on an angle.  I guess they were trying to have the slot follow the curvature of the spring.  I will open it up to see if that helps.

Thanks,

Wayne
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Wayne Foster
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