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UP3 valve and large models

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Old 02-11-2011, 05:37 AM
  #1
butlern
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Default UP3 valve and large models

Need some advice on whether a UP3 valve will be suitable for my model (1/5 scale F7F Tigercat, robart gear designed for this model)

Now, in theory this valve should work for me; doors open, gear down (door stay open), gear up, doors close. Simple.

My concerns:

1) timing— what is the delay or time-interval between toggling to “gear up” and the doors closing, and is it adjustable? My worry is that wind-loading (or differences in air pressure within the system) might slow one or both main gear legs as they make their way back into the nacelles. If the doors close too soon, that’s going to potentially spell disaster if something jams, or if I don’t see it immediately and there’s a loss of pressure.
2) Air volume—I have 5 cylinders for the landing gear (2 for each main gear, 1 on the nose wheel, ~5/8 bore x 2.125” stroke) plus the additional 6 smaller air cylinders for the gear doors (5/16 bore x 1.5” stroke). Is the porting such that a single UP3 valve can handle the volume of air required to get the gear up and down at least 2-3 times?

I have also considered using an electronic sequencer and servos, but I would prefer not to have all the additional weight and potential drain (of 6 more servos, leads, hardware, etc…)

Any thoughts or input based on personal experience using an UP3 valve (on much larger models) is welcome.

Thanks

Noah
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Old 02-11-2011, 06:44 AM
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Default RE: UP3 valve and large models

What about this…

These “button switch” actuators?

For example: http://www.robart.com/products/gear-door-valve

I assume that by positioning this correctly within the nacelle, the gear leg (once fully retracted into the nacelle) would trip the valve and then the gear doors would close. Thus, it follows that when the gear legs starts it’s downward/outward travel, the button is released and the doors immediately open (hopefully opening before the gear crashes into the doors).

Any first-hand experience with these little units?

I also see that Sierra sells a similar version, too.

Thanks,

Noah
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Old 02-11-2011, 06:57 AM
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Default RE: UP3 valve and large models

Yes the timing is adjustable. But I have seen problems with this valve on a 1/5 scale F-86. It couldn't deliver the volume of air needed to pull the gear up before the doors close. However on my 94" corsair it works perfect and also on my Comp Arf UltraLightning (Heavy gear) it works perfect.
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Old 02-11-2011, 07:23 AM
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Default RE: UP3 valve and large models

I have the UP 3 valve in My Yellow Aircraft P-47. The door opens, the gear extends..  Raise the gear and the door closes.   From what I can determine in working with mine, The follow on action  doesn't take place until the first action is complete and air preseure then moves a shuttle valve that then moves the second action. IE:  On extension, the first action is the air is directed to the door cylinders. when they are down, the pressure is then shuttled to the gear cylinders. On raising the gear, the shuttle is already in the gear position, so the gear raises. When the pressure builds ( after the gear is all the way up) the shuttle valve moves and directs air to the door cylinders.

My only issue so far is everything has to be propperly lubed and free so the shuttle valve doesn't stick. If you had a sticky spot in one of the actions (sticking door or gear wants to hang in one spot for some reason) the pressure rise could possibly cause the shuttle valve to transfer and start the second action.    I have bought some silicon oil that should take care of that.

As for the timing delay, I can't see how that can be adjusted. The rate that the gear moves is adjustable if you want one side to move first or faster.

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Old 02-11-2011, 07:24 AM
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Default RE: UP3 valve and large models

Im using these valves for years. They are fully adjustable. If the gear are not retracting before the doors close then the needle valve on the block needs to be opened up allowing the gear to retract faster.
... When all else fails, read the directions.
They were actually designed for the larger airplanes.
Always use the largest air vessel possible or use multiple vessels with the larger systems with many or larger air cylinders.
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Old 02-11-2011, 07:31 AM
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Default RE: UP3 valve and large models

You are right to be concerned about the difference in operation between the ground and in the air. I used one of these on my P-51, and in the shop or at the field it worked perfectly - but once in the air the wind changed the dynamics and it never worked. I know many people have used this successfully, but I could not make it work.

Since then, for all my models, I have gone to the 4 way Century Jet valve (for the retracts) and any other standard valve (usually the one that comes with the retracts) for the doors. I use the Electro Dynamics sequencer and plug the two servos into it. The electronic sequencer is adjustable with a small pot to delay the gear door closing cycle.

If money is not a concern, you may want to consider the Jetronic valve. It is all electronic and requires no servos.

Good luck with your Tigercat - whose kit is it?
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Old 02-11-2011, 07:41 AM
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Default RE: UP3 valve and large models

Like quist just said, its adjustable, I have it on my Z P-38 and Yellow P-47. I have attached a the link of the video of it in operation on the Jug.


http://www.youtube.com/watch?v=1swbDRVIvNg
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Old 02-11-2011, 08:10 AM
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Default RE: UP3 valve and large models

Butlern - I made an error when I said I used the EDR sequencer. It is the Jomar model that I use. It has dip switches for use with P-51 style or P-47 style and has an adjustable delay up to 10 seconds for the door closing cycle. Sorry for any confusion.
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Old 02-11-2011, 08:13 AM
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Default RE: UP3 valve and large models

I like Dash's interpretation of how this device should work... pressure build-up triggers the next sequence (a pressure "build-up" that's only possible after the cylinders of the previous sequence come to a physical stop). If that's NOT how it works, then I need to do some careful thinking about whether I want to attempt to use the up3, especially given the failures that JPate147 has encountered.

Money is always a concern, but the health and safety of the model, as well as my time-investment, will ultimately dictate which direction I take for sequencing these doors.

here's the F7F build:

http://www.rcuniverse.com/forum/m_93..._1/key_/tm.htm

It's from Giant Scale Twins, located right here in Iowa!

Thanks for the comments thus far.

Those with personal experience using "fancy" electronic sequencers are welcome to chime-in, too!

Noah
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Old 02-11-2011, 11:48 AM
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Default RE: UP3 valve and large models

On my recent build I had the situation where the doors stay open when the gear is down and I decided to try something different. The Futaba 12FG has 3 postion switchs and I used that. When I go from down to middle position the gear retracts. When I go from middle to up position on the switch the doors close. There is also a timer in one of the programs with I think was a 4 second delay so I even use that. Dropping the gear everything works backwards. You just need 2 valves and 2 cheap servos and 2 channels to do this.
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Old 02-14-2011, 04:15 PM
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Default RE: UP3 valve and large models

What about Ultra Precision air cylinders versus the AirPower brand?

For example:

http://shulmanaviation.com/product_i...roducts_id=772

Anyone have any experience with these cyclinders? They're more than 20% less expensive than UP cylinders, which is essentially why I'm asking.

Better, worse, same quality as UP?

Noah
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Old 02-15-2011, 07:40 AM
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Default RE: UP3 valve and large models

thanks, jkeze.

I'm still considering all my options, including the use of simple mechanical actuation (servos), or maybe the use of an electronic sequencing valve (but those are pricey!).

No one with experience using AirPower equipment?
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