Wayne22

My Feedback: (2)

Somewhere on this forum I came across a picture where someone cleverly used a single servo to operate two airvalves...one for retracts and one for the doors. I have spent several hours combing through results using the SEARCH function, but cannot find the picture.......

Can anyone help??

cactusflyer

My Feedback: (4)

Tam uses a set-up on the 1/12 F-16 EDF like that. I don't have a picture, but i can get you one. Basically, the servo arm has two legs on it. One is connected to the retract valve and the other is 90° to it. This leg will push on a trigger valve that is rigged on the DOOR CLOSE side of the airlines. The doors are hooked up in parallel with the retracts. So. when the gear is retracted, the pressure goes to the trigger valve and when the trigger valve is made, the doors close. You must set-up the linkage so that it goes over center on the retract valve when the trigger valve is activated. This is all activated with a three-position switch on the TX. You have to be careful and first retract the gear, wait and then hit the switch all the way to close things up. For extension, everything blows open at the same time. It is a very ingenious and light weight solution to the problem.

Tailwinds,

John

Countryboy

My Feedback: (25)

Wayne22,

Is this by chance the picture you were looking for?

http://www.rcuniverse.com/forum/m_68.../tm.htm#687412

Or perhaps these pictures....

Vincent

My Feedback: (61)

I would mount that trigger valve in where the gear are and have the strut actuate it. That way you are sure the gear are up and tucked away before the doors close. All gear dont close at the same speed depending on their direction size and shape.

V..

Countryboy

My Feedback: (25)

Vincent,

Your last sentence there pretty much sums up as to why it is setup the way that it is. Unless you are absolutely sure that the gear you choose to actuate the trigger valve is the last gear up & the first to extend each & every time, you run a risk of interference. With the setup shown, the shuttle valve for the retract sequence has already went completely through it's travel and all gear are tucked away before the servo arm hits the trigger valve for the doors to close.

MaJ. Woody

My Feedback: (28)

Ingenious for sure.
Dom

Tom Antlfinger

My Feedback: (24)

John's description covers it......actually this system has appeared in BVM manuals dating back at least to the Maverick days of the mid-90's....

On my Kingcat, I use the method that Vin mentioned where the button valve is closed by the nose gear strut which closes the nose gear door....not pictured....

On my UltraBandit, I just use the original BVM setup which he still describes in the UB manual......just slow down the gear servo and put Robart restrictors in the door close line.......not critical at all....see photos 1 & 4

On my Bobcat, got fancier......took a round output arm and carved it to the shape seen and rather than using just the plain button, used BVM actuating arm on the button as it moves more smoothly over the output arm.....now I have the door close both up and down, once again controlled by retract servo speed and restrictors........see photos 2 & 3

Rather than having everything come down when you select gear down simultaneously, you can use a third tank for the down door command rather than the gear down line off the retract valve....you just keep pressure in that tank well below the gear up pressure, about 100 psi to the gear, say about 25-40 psi to the door tank.....that way the doors open independent of the gear down pressure line, if that makes sense.....that's the way I have it set up on the Bobcat......overkill and really not necessary....

And if you really want to get fancy, you can actually work in the brakes, still using one servo as Tom Dodgen has described for the factory Bobcat ......then you use the button for on/off brakes by going over center on the retract servo with a mix off the snap roll button....but then, you can't do a gear door.....

The air system is described on BVM Air System Schematic #6308.......photos in the gear up/gear down positions

mr_matt

My Feedback: (10)

I still don't understand how these single action valves (contacted by one of the gear struts to actuate) can be set up to keep pressure actively holding the door open while the gear is retracting? Maybe I have been unlucky, but I find that when the gear starts to retract there is only the friction of the gear door cylinder to hold them open. Too easy for the airloads to push the door into the path of a retracting gear.

Am I missing something? I usually break down and use a UP 2 and you have it all in one shot, and you can still us a button for brakes

Wayne22

My Feedback: (2)

Thanks for all the ideas, guys... I will have to go through and analyze and digest each one..... (it is too early in the day yet, and I haven't even had my coffee yet..... )

Meanwhile, if there are any other ideas, please post them...I'm all for choices.....

Vincent

My Feedback: (61)

Countryboy,
I have a 5sec delay on my JMP sequencer in my AD F-16 and i need all of it to get the forward retracting mains in there before the doors close. No way could you get that type of delay with the setup pictured. Strut actuation in this case is the only way to go. Each setup is different and most standard retracting inward type gear would probably work with the servo actuation moving slow. I like the JMP sequencer with two valves if i had the choice.

V..

Tom Antlfinger

My Feedback: (24)

Actually Vin, I have about a 4 second delay on my UltraBandit between nose gear up and gear closing and could increase that.........all depends on the servo speed setting(Menu 24/10X) and the overcenter geometry...

I am running my servo speed at 20.......I have gone down to 10, but then the delay of door closing is excessive, about 7-8 seconds......

I am using a JR 341 which tolerates very slow servo speed settings without getting jittery like 2721 or 8411's do.....

Only reason I posted a couple of my setups is for Wayne to see other systems that work with one servo......the way BV recommends locating all the air stuff on my big Saber made much more sense to use 2 valves with a JMP sequencer which is the way I have it set up......UP 2's and 3's have also served me well........my buddy
Dave won't use anything else....I have a UP-3 on my SJ-16

Plus more than 1 guy has asked me how in the heck my UltraBandit door works.....gotta keep em guessing....

T

CARS II

My Feedback: (7)

mr matt

When the gear comes up and it compresses the mini air valve arm this allows air from the up gear lines to past through the mini airvalve then through a restrictor to activate the air cylinder to close the doors by then the retracts are at home. [8D]

hope this helps.

CraigG

My Feedback: (40)

Matt,

I've used the single button system successfully on several jets and the situation you describe (gear door is not held open with pressure during the retract cycle) can be a problem. It helps to tighten cylinder attach rod (usually just a small machine screw) to create additional friction to hold the door open but still allow the door to close under pressure.

If that doesn't work, the UP or Mini Hobby cycler is the answer.

Craig

Tom Antlfinger

My Feedback: (24)

Like I mentioned in my original post, the easiest way to get rid of the floppy door problem on Gear Up is to add another air tank to keep the door open.....I use one of the small on-board Powermax tanks that you can stick almost anywhere, rather than getting door-open line air from the retract tank......then pressurize that one to 25-40 psi which will keep the door open until overcome by the door close pressure of 100-120 psi.....that's the way the Bobcat is set up.....

Adding a little friction by tightening the attach screw and adding a locking nut like Craig noted has worked on my KC and UB.....

Peter A

My Feedback: (34)

Wayne
Why don't use a UP2 or UP3 from Precision? A much more precise solution and you only need one servo.

http://www.altecare.com/ultraprecision.htm

Regards
Peter

Vincent

My Feedback: (61)

Tom wrote: Like I mentioned in my original post, the easiest way to get rid of the floppy door problem on Gear Up is to add another air tank to keep the door open.....

Tom,
On my Tams A-4 which only has a nose door, the button switch is activated by the nose strut. One side of the door piston is tapped into the down side of the gear and the other end of the piston is tapped into the button switch which is being fed from the up side of the gear plumbing. The door stay firmly open with the down gear pressure.

V..

CraigG

My Feedback: (40)

Tom,

From your previous post I couldn't figure out how that extra tank worked but now I understand....very ingenious! Did you figure that out yourself? I suppose a guy who is smart enough to re-order RCJI can do almost anything.

Craig

mr_matt

My Feedback: (10)

sounds great

Tom Antlfinger

My Feedback: (24)

Hi Craig:

Picked up the tip from Florida Pro builder, Barry West......not sure if he is the originator......he has worked at times for BV and I know Bob and Tommy were fiddling with keeping things as light and simple as possible when they first introduced the BARF/P-60 a couple of years ago.....they started with using over center on the retract line for on/off brakes which they currently show in the BARF manual.....

If you just use the button to close the door with retraction, then adding the friction works fine, but to get the pressures and timing right with both open and close using the button was tedious and became easy using the extra(spring) tank....

The button system is ideal for tinkerers as UP's or even double servo, double valve systems work fine with a JMP or JetCat sequencer and are very simple, but the buttons still might have some life in the new small jets that are becoming so popular.....I stuck mine in the UB cuz I used up so much of the space with my Emcotec Power Box with dual RX and dual batteries and smoke system(decided to not use smoke)......I don't like sticking things with velcro to the sides of fuse and really ran out of room for a servo and UP-3 on the radio board.....

By now, Wayne should be thoroughly confused....

Tom

mr_matt

My Feedback: (10)

Hi Vin,

Sent you a PM

Regards,

Wayne22

My Feedback: (2)

[sm=spinnyeyes.gif][sm=spinnyeyes.gif][sm=spinnyeyes.gif]

heh heh heh...you are not far off there..... Sure is more than one way to skin a cat!!

Can someone clarify something for me.... I can see how a strut activated button would close the doors....do you guys use on one each strut, or guess which is the slowest strut and use that for the trigger? Secondly, going down....how is the gear door ram pressurize to open the door prior to the strut (or wheel) hitting it???

...that UP-3 valve is looking like the simplest way to go... (thanks, Peter....)

CraigG

My Feedback: (40)

Thanks for the explanation Tom. Super nice and clean install on that UB!

Craig

CraigG

My Feedback: (40)

My experience with multiple doors is to use the retract valve servo at the end of it's throw to activate the button/switch as Tom and others have described in this thread. You set the speed of the servo as slow as you need to allow plenty of time for all the gear to retract. The other option is to restrict the nose gear air, insuring it will be last to retract, and activate the button when the nose strut is fully retracted. Never heard of using a button for each door but I suppose you could.

As far as opening, it's pretty much simultaneous. Since the doors require less air they tend to open a little quicker and even if the wheels or stut happen to move first and contact the door it will just push them open.

Craig

Tom Antlfinger

My Feedback: (24)

Good question Wayne....On the UB, without the extra spring air tank, the wheel actually does start the door open, but as soon as there is any air pressure going in to down line, the door cylinder actuates actually faster than the big fat cylinder on the gear, thereby getting out of the way....of course, this is no problem if you use the spring tank, since then, as soon as the servo arm comes off the button, the door crisply opens, long before the gear starts to extend.....

I put some aeropoxy on the inside of nose gear door on the UB where the wheel contacts it during initial opening.....probably overkill.....since as soon as the servo arm comes off the button, even without the spring tank, the pressure holding the door closed dissipates almost instantly.....

This methodology is somewhat archaic, but got to remember, BV started using this system for gear doors long time ago, before the UP's and electronic sequencers were readily available.....and when most of the current Asian splash-masters were still in poopy nappies......

Terry Holston

My Feedback: (1)

On my Panthers I use the UPC-3 valve for the doors and retracts......Plus a button valve on the nose gear doors So they stay open when the UPC-3 valve closes the inner main doors when the gear is down. I also have a small spring I wound myself on each door holding them open naturaly, the cylinder closes the nose doors against the spring pressure. simple......