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hydraulically actuated nose gear


Steve Innova

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I recently purchased a set of Infinity main gear retracts, which I will be installing on my modified Cozy MkIV.

 

I also have a Steve Wright's electric nose gear retract system, which weighs about 15 lbs.

 

I'm considering using a hydraulic actuator to raise the nose-gear, replacing the Wright electric lift. This should [theoretically] save me about 10 lbs, as I'd be using the Infinity hydraulic pump, for which I've already paid the weight penalty.

 

I seem to remember the SQ-2000 went this route, but some builders have opted for electric nose retracts instead.

 

Is the 10lb weight savings worth the added complexity of additional hydraulic lines/valves? What are people's thoughts?

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I thought about doing this, but decided against it;

 

It would be possible to use a single pump (the Infinity pump) to drive both the mains and the nose. In order to retract/extend the nose separately from the mains, you would need at minimum two additional solenoid valves. These valves would isolate (shut off flow) to the main UP and DOWN circuits that go to the main gear actuators.

 

I decided not to do this because of the risks associated if either of these valves failed.

 

1) If the UP valve failed, you would pressurize the mains UP cylinder, but they won't go up because the fluid on the down side is locked by the DOWN valve.

 

2) If the DOWN valve failed, the mains DOWN pressure would vent to the reservoir, but the UP valve prevents the nose up pressure from pressurizing the UP side of the main cylinders.

 

3) If both valves failed, (or leaked) it would be conceivable that the mains could retract while the nose is retracting.

 

 

My biggest concern would be a small leak in the DOWN valve. If there were any trapped air in the MAIN's side of the valve , the fluid could leak through the DOWN valve and pressurize the DOWN lines going to the nose. This could result in the nose gear extending slowly over a period of hours, days, or weeks, and the plane ultimately falling back on it tail.

 

I'm not sure about any weight savings. Compared to the electric actuator, the hydraulic system would include the additional weight of plumbing and fittings, actuator, valves, fluid, and maybe an external fluid reservoir (The internal resevoir on the Infinity pump may not have enough capacity to provide three actuators with fluid).

 

 

The electric nose gear provide total isolation of these components and is a drop in solution.

 

Waiter

F16 performance on a Piper Cub budget

LongEZ, 160hp, MT CS Prop, Downdraft cooling, Full retract

visit: www.iflyez.com

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I recently purchased a set of Infinity main gear retracts, which I will be installing on my modified Cozy MkIV.

 

I also have a Steve Wright's electric nose gear retract system, which weighs about 15 lbs.

 

I'm considering using a hydraulic actuator to raise the nose-gear, replacing the Wright electric lift. This should [theoretically] save me about 10 lbs, as I'd be using the Infinity hydraulic pump, for which I've already paid the weight penalty.

 

I seem to remember the SQ-2000 went this route, but some builders have opted for electric nose retracts instead.

 

Is the 10lb weight savings worth the added complexity of additional hydraulic lines/valves? What are people's thoughts?

I have an hyd. nose gear system in my plane designed by Shril Dickey. the components weight about 5 lbs. the cylinder is from a Cessna 210 gear door. the biggest problem is that you can not drop the nose for parking and my system will not lift the weight of the nose even it was actuated separately. a cylinder that would lift the nose will weigh well over ten lbs.. My plane does not park nose down so this is not a problem for me but would be for a Cozy IV. the lift system that can lift the nose with pilot and copilot is worth the weight. put the pump in the nose a cozy IV needs the ballast there anyway. the main retracts may get you 10 MPH on top end but the weight penalty is high and will take away from usefull load. not the best trade off since you will loose more in gas milage during climb the you will make up for in cruse. the retract gear makes no difference in milage during a 170 Kts. cruse. we have tested this during many flights. my plane with full retracts against a stock cozy IV with the same engine and same prop and we use the exact same amount of fuel on every trip.

Evolultion Eze RG -a two place side by side-200 Knots on 200 HP. A&P / pilot for over 30 years

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I'm all for the experimental in experimental airplanes but would not opt for a hydraulic nose retract unless the mains were hydraulic. All of my EZ projects have electric lifts and would never go back to the plans gear box. I strained my back once while lifting the nose on my Cozy. I scuffed the underside of the nose when the cast gear sheared some teeth on a bumpy runway (embarrassing). The retract that Jack Wilhemsen sells is excellent and compact. My Cozy always got a reaction when I taxied in and lowered the nose. I have my Long EZ set up so that I can overextend the nose gear just a little to get a positive angle of attack on takeoff and retract it just a bit for the landing to reduce landing roll. Can you do that with a hydraulic system?:bad:

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Not to get to far off subject and just thinking out loud, is there any reason the mains and front gear can't be air operated as air is used for the blow down system? I'm building my own retracts, (not started yet) and am looking at all possibilities. I'm thinking hydraulics can apply more pressure size for size than air and is not used for that reason? :feedback:

Press on

T

"Time flys when your building"

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Not to get to far off subject and just thinking out loud, is there any reason the mains and front gear can't be air operated as air is used for the blow down system? I'm building my own retracts, (not started yet) and am looking at all possibilities. I'm thinking hydraulics can apply more pressure size for size than air and is not used for that reason? :feedback:

Press on

T

Pnumatics can be used, some British airplanes have used pnumatics. There are some advantages. If there's a small leak, you don't care. You don't have to have a return line.

 

On the other hand, if a line ruptures its' MUCH more exciting. Small high pressure air pumps are much harder to find. And there's all the stored up energy that you have to get rid of. If you have 3000 psi in a hydraulic line and you come to the end of the piston gear stroke, the pump turns off, the piston stops. If an air valve turns off, you still have 3000 pst trying to move the piston.

 

So it's POSSIBLE, but it puts you into more basic design.

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Not to get to far off subject and just thinking out loud, is there any reason the mains and front gear can't be air operated as air is used for the blow down system? I'm building my own retracts, (not started yet) and am looking at all possibilities. I'm thinking hydraulics can apply more pressure size for size than air and is not used for that reason? :feedback:

Press on

T

Hydraulic is used so you can use higher pressures. High pressure air pumps use a lot of power. the higher the pressure the smaller the cylinders. it saves weight and space. most of the systems use about 1600 PSI to raise the gear and hold it up and about 750 PSI to lower and lock the gear down. air is used for blow down on some of the systems as a emergency backup. the Eracer/berkut and the velo gear do not use the air. the system is designed to fall down by gravity when the pressure is released from the up or retract cylinders.

Evolultion Eze RG -a two place side by side-200 Knots on 200 HP. A&P / pilot for over 30 years

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Thanks for the response guy's. I'm going to look into it further when I get closer to the gear portion of my build. Any further info from all else is appreciated! :thumbsup:

Press on!

Tom

"Time flys when your building"

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