Ragz

I am having issues with the nose door actuator switch on a BVM Ultra Bandit. I have installed the push button actuator in such a manner that when the nose gear goes up, it hits the push button and the nose door shuts. However, the stock push button (robart) is rather sensitive and it needs to be pressed exactly to a certain point, any more or less and it results in air leak. I had one gear up landing due to this and got out of jail free...Ever since then I have installed the dreamworks gear fail safe....however, I would like to do away with this push button. Are there any other alternatives?

David J Ruskin

Yep, use UP valves.
David

Bob_B

My Feedback: (11)

Mount the button adjacent to the retract servo, then have the arm press the button.

Ragz

Bob B, I thought of doing this but even this would not really be fool proof IMHO.  The arm needs to move to the exact mm for air NOT TO LEAK.  Sometimes servos tend or over drive or underdrive a hair and im afraid this may not be good enough.

FalconWings

My Feedback: (57)

Did a similar mod as Bob on my BARF. Basically placed the push botton switch next to the retract valve piston. When the servo pushes the piston in, the piston pushes the switch at max travel. Then I simply programed the servo speed for slow retraction. Works like a charm!!!

David

grbaker

My Feedback: (29)

Place some sort of spacer in between the valve and the button so that when is pressed all the way, it is in the ideal - no leaking position. Glue a small piece of foam on top of the button so that the gear will always push the button all the way to the stop (your spacer). You may need to reposition the switch/valve a little to avoid locking the gear in the retracted position.

Hope this make sense.

JackD

My Feedback: (4)

Anurag,

That is how they fail (become too sensitive to side loads). Get a new one, they should not be so sensitive to misalingment

Also, whenever I use a button for doors, I put separate bottle for the doors, because those buttons are your weak link in the system

Hope this helps

Jack

sc0tt

My Feedback: (61)

Push button relocation to BVM'sretractvalve is ok but you still have potential for leaks in my opinion.For perfect & consistent operation I wouldswitch to a Behotec Retract/Brake valve. TheBehotec valve has been flawless for me and is hi-flow to handle heavy gear.

Just use the Behotec valve in reverse to close the gear door(s) instead of brakes.
Here's my old threadhttp://www.rcuniverse.com/forum/fb.asp?m=10924042

<u1></u1>BVM's button valve infohttp://bvmjets.com/JetKits/MiGe/Addendum082611t.pdf

Hope this helps...Scott<o></o>

Harley Condra

My Feedback: (4)

And, the push button valve is from Clippard Instrument Laboratory, not Robart.
See page 113 http://www.clippard.com/downloads/PD...Page%20113.pdf

Andrew Bird

The UP3 valve has gear door actuation and is perfect. I've had the same trouble in the past and just went UP and never looked back.

Geoff White

Lots of options here but here is another one - operate the door using a servo and a conventional valve and then do the sequencing using the radio(in my case a 18mz). I have done this on my last two models and it works perfectly and is infinitely adjustable.

Geoff..

Airplanes400

My Feedback: (349)

I'd suggest that you use a servo for the door actuation and a sequencer for the time delay.

Ragz

Thanks for all the suggestions. Since the door already has a pneumatic valve I would prefer to stick with pneumatic. I will explore UP valves seems like the simplest retrofit for my situation. Other solutions are also workable but just a lot of extra work on an otherwise beautiful flying airplane. 

Area51.5

You could use the bvm push button version which has a built in arm. That way the gear hits the arm and the has mechanical advantage on the button.

Harley Condra

My Feedback: (4)

Why didn't I think of that?
Here's a photo of it: P/N BVM5253 price 32.00 USD.

JackD

My Feedback: (4)

Anurag,

Reading your post again, it seems like you are hiting the button with your landing gear. Is that correct?

If you are doing it with the gear, that might be your problem. That will be pretty erratic. the best way is to have the servo that moves the air valve, hit it with an extra travel. here is a video on how it is done with a DX18 on an UltraBandit

http://www.youtube.com/watch?v=YQphSWqKRtU go to minute 1:30

Even if you don't have a DX18, look at the video as you will see the servo geometry to accomplish this

hope this helps

jack

rcpete347

My Feedback: (251)

HI, do your self a favour, and throw the valve in the garbage, as the retract system gets older and more sloppy, it does not make proper contact, and you loose all air, ask me how I know, then you have the pleasant task of landing with gear up, and then you have lots of hours of repair.
Rcpete

sc0tt

My Feedback: (61)

The simplest solution is the Behotec valve - small installation area, only 4 air lines, bullet proof from my experiences and inexpensive.http://www.altecare.com/retairsysaccess.htm

JackD

My Feedback: (4)

THat is why I suggest to activate with the servo arm on the retract valve, not with the gear itself. Too much play on the gear to ensure a consistent actuation

Ragz

Here is a pic of my UB. Thanks for all the suggestions guys. Appreciate it.

CraigG

My Feedback: (40)

I'll go against the consensus here. I used the push button on my Ultra Bandit just as the instructions show and it worked fine. I like it because it is the simplest solution (KISS principle), it is easily adjusted and by having it actuated by the nose gear strut, it guarantees that the nose gear door will never actuate closed before the nose gear is retracted. None of the other methods can make that claim and it's almost a guarantee it will happen sooner or later for a variety of reasons.

I'm not sure why people are saying the nose strut retracted position is inconsistent....this is BVM stuff! Wherever it retracts to, mount the button firmly against it and you're good to go.

From your description, you have a bad switch. Get a new one and you will be fine.

Craig

Ragz

Craig, my install is an identical copy of yours.. and it leaks more often than not.  I have set it up in such a manner that the button is completely pressed when the gear is up...but every now and then I find that the gear has not reached the exact same place to compress the button.

CraigG

My Feedback: (40)

Ragz

In that case, I would try the mechanical arm like Harley suggested. I would also make sure you are positioning the button with the jet upright, such that whatever "droop" there is in the gear is accounted for (i.e. with negative G it just pushes against the button, rather than away from it with positive G), if that makes sense.

I also still believe you have a bad button. I would get a new one regardless because it should not leak air under any circumstance.

Craig

Harley Condra

My Feedback: (4)

Ragz,
You have a leaking button valve.
I have the same system as Craig's (but with the lever) in my FA-18F, on a main gear leg. It works perfectly, and the doors cannot close unless the gear is in the wells. I try to use the KISS principle. (Keep it Simple, Stupid).
Changing gear valves is a hassle, and many of us have found some of the electronic valves to be expensive junk.
Just install a new lever actuated valve in the same place, and the problem is solved.

ddennison

My Feedback: (15)

I have has similar issue with the lever activation on my nose gear for my A10. A little flex in the system caused the lever travel to vary and the valve to leak. It worked fine out or depressed, but partially it caused a problem.
I reworked mine by making sure the structure around it was solid and also used a softer endpoint.
I used two fuzzy sides of velcro(so they don't stick) so the the lever would be pushed firmly but could also not have too much push on it. This worked for my A10.
I had it hard mounted in my f18 on the nose gear and that worked fine too.
I did have one break (plastic arm) also.
My uB has the over travel trigger, this works well but also doesn't ensure that the gear are retracted before triggers the nose door.
I just have the gear servo slowed down so it works fine in the air.
Good luck
Dave