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View Poll Results: What type of gear will (or would) you install
Featherlite Strut 47 45.19%
Infinity Retracts 43 41.35%
Aerocad fixed gear 2 1.92%
Other retract system 12 11.54%
Voters: 104. You may not vote on this poll

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  #61  
Old 06-24-2006, 12:49 PM
Lynn Erickson Lynn Erickson is offline
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Quote:
Originally Posted by JonC
I'll add to Lynn's bit here....

With Swing/Drybread gear they are held down by an overcenter clip and spring. There is no hydraulic pressure involved in holding the gear extended like Infinity and Berkut/ERacer style (Which can be landed on with no hydro pressure, but do not have 100% of the extension power they do with pressure so you should be gentle.)

If you dump the hydraulic pressure the gear extends just like it would if you used the pump to extend the cylinder and locks with the full strength that it always would.

So dumping the gear in one of these planes is not an Emergency procedure, it becomes an Abnormal procedure as there is no adverse effect or risk in doing the procedure.

I'm not berating the ERacer gear, nor the Infinity, just pointing out the strengths in having a very simple system.

100% gravity extension... as long as the pressure drops in the system it will come down and lock. No uplocks, no compression of struts, only gravity and time tested and proven springs.
Jonc, You are almost correct about the drybread gear. the gear is held down by an overcenter link between the gear leg arms and a spring that helps gravity as the link sometimes would not drop in place with gravity only, unless you rock the wings. However, wrong on the Eracer ( should be listed first as Shril Dickey is the designer of this gear )/ Berkut style as they do not rely on the hydraulic pressure to hold the gear down and are supported by an overcenter link when in the down position and will fall to this position by gravity if the up pressure is dumped by the emergency gear down valve. The aircraft can be landed and taxied as normal as there is a spring to hold the overcenter link in position as in the drybread system. the infinity is different in that the gear will not fall into place without the hydraulic or the CO2 cartage . the emergency co2 works some of the time and if the system has a leak as in a broken hose all the Co2 pressure goes out the leak and the gear does not extend. there is gas pressure that helps hold the wheels stuck in the wheel well.
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  #62  
Old 06-24-2006, 10:41 PM
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Quote:
Originally Posted by Lynn Erickson
Jonc, You are almost correct about the drybread gear. the gear is held down by an overcenter link between the gear leg arms and a spring that helps gravity as the link sometimes would not drop in place with gravity only, unless you rock the wings. However, wrong on the Eracer ( should be listed first as Shril Dickey is the designer of this gear )/ Berkut style as they do not rely on the hydraulic pressure to hold the gear down and are supported by an overcenter link when in the down position and will fall to this position by gravity if the up pressure is dumped by the emergency gear down valve. The aircraft can be landed and taxied as normal as there is a spring to hold the overcenter link in position as in the drybread system. the infinity is different in that the gear will not fall into place without the hydraulic or the CO2 cartage . the emergency co2 works some of the time and if the system has a leak as in a broken hose all the Co2 pressure goes out the leak and the gear does not extend. there is gas pressure that helps hold the wheels stuck in the wheel well.
Lynn,

I've always been informed that the ERacer/Berkut gear normally relys on the hydralics to hold the pivots in the overcenter position, unless there is no hydraulic then the pogo stick does all the holding. While it is improbable, it would be possible to knock the pivot arms out of the overcenter position as there is no positive downlock clip on them when they are extended. Just a thought
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  #63  
Old 06-24-2006, 10:52 PM
Lynn Erickson Lynn Erickson is offline
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Quote:
Originally Posted by JonC
Lynn,

I've always been informed that the ERacer/Berkut gear normally relys on the hydralics to hold the pivots in the overcenter position, unless there is no hydraulic then the pogo stick does all the holding. While it is improbable, it would be possible to knock the pivot arms out of the overcenter position as there is no positive downlock clip on them when they are extended. Just a thought
I have a 60 lbs spring that holds the overcenter in the down position if the hyd. fails and it takes a three foot long lever tool to move the links out of overcenter when on the stands. normal operation loads will not knock it out of overcenter
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  #64  
Old 06-25-2006, 04:32 PM
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Quote:
Originally Posted by Lynn Erickson
I have a 60 lbs spring that holds the overcenter in the down position if the hyd. fails and it takes a three foot long lever tool to move the links out of overcenter when on the stands. normal operation loads will not knock it out of overcenter
Hrmmm, yes I'd say there is little chance of it then. Everyone I have talked to has always told me that you have to be careful without pressure... guess its one of those rumors that is incorrect that gets passed around.
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  #65  
Old 06-25-2006, 07:50 PM
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The E Racer gear has pressure on retracted and extended positions. If the pump fails, there is a dump valve that will release the gear to the fully extended position. I added an overcenter spring to my system just in case the gear failed to go overcenter by itself. I believe the Berkut system is the same with a little different lockout system and hydraulic system that operates the outer gear doors. Since adopting all the modifications developed by Berkut, the gear system is very dependable.

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  #66  
Old 06-28-2006, 11:25 PM
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That reminds me... Lafluer, did the rest of your Infinity gear arrive yet? Just curious.

It's like de-ja-vu all over again.
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  #67  
Old 06-28-2006, 11:41 PM
eracer113 eracer113 is offline
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The over center spring that I have on my E Racer is my own design. The modifications from Berkut were the lower talons and the reinforcement caps on the top of the gear leg pivot point where the shaft runs through. I had several failures where the bolt goes through the top of the gear leg the carbon fiber would crack at the outside edges. The end caps work fine, I have not had a problem since. My only complaint about the gear system on the E Racer is the clearance Shirl had between the gear legs and the trough clearance in the strakes. The plans called for 1/8 inch clearance on each side which makes it impossible to install hydraulic outer doors as the Berkut has because there is not enough room. I still have not given up on my manual outer doors, I am close.

Jack
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  #68  
Old 06-29-2006, 03:16 AM
SteveWrightNZ SteveWrightNZ is offline
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I'm surprised the conventional power-steering hydraulic pump isnt used. Surely they are well proven in automotive service. Particularly appropriate on an automotive engine install.
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  #69  
Old 06-29-2006, 10:38 AM
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Steve parkins Steve parkins is offline
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Quote:
Originally Posted by SteveWrightNZ
I'm surprised the conventional power-steering hydraulic pump isnt used. Surely they are well proven in automotive service. Particularly appropriate on an automotive engine install.
if the engine stopped so would the pump, so you would need to put the landing on hold until you had the engine look @ and you may not have the time to have them look under ths hood
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  #70  
Old 06-29-2006, 01:56 PM
Leon Leon is offline
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as I'm about 10yrs away from starting this, let me plz ask a few very stupid questions. I've read through this whole thread here, but somehow can't really figure out what's going on. Might be partially because I don't know what oleo is (shockabsorbing gear i suppose?? as a motorcycle fork works??)

I've looked at the Infinity retract but I cant seem to find anything about featherlite or aerocad. But sofar here's my amateur opinion.

YES retracts are WAY cool and they do make sense in saving fuel and/or going faster with same fuel use. I also understand that most of you are "afraid" of the gear system failing, meaning you'd have to do a gear up landing, banging up the prop, maybe bending the crank or PSRU and scratching the main body.

IMHO I'd go with retracts as well, probably hydraulic, but for fail safe maybe better electric system.

HYDRAULIC:
+ faster actuation than electric (gear cycle time decrease) [i think ]

+ less load on the electrical system

+ manual override possibility, either by CO2 pressure bottle or manual pump override

- in case of leakage in the system, the gear won't work at all, so your only change would then be gravity pulling the gear out, but then, depending on the gear system, it might not "lock" in the down position. But the locking is a thing that can be overcome (maybe by spring acting as a "gear down" actuator anyway, and thus locking the gear in place by a "clip"style latch or something)

- weight (i figure hydraulic system is heavyer than electric system)

ELECTRIC:
+ less to go wrong because no leakage possibility

+ lighter than hydraulic system

+ easier "infrastructure" with cables being alot easier to work with than hydro lines.


- high electrical load (this is just a guess from my POV and expereience)

- slower actuation

- no emergeny actuating possibility (no way to "pump" the gear, but alot less to go wrong in the first case, cables don't tend to leak very much) but on the other hand it's a binary system. either it works or not, it cant work a little like hydro could (again guessing this fact)

I don't know how electrical actuation actually works, but I think it must be by some sort of sprocket system or similar, so it probably won't work on gravity.

FIXED GEAR:
+ nothing to go wrong (or very VERY little)

+ easier to build


- plane ugly

- more fuel consumption (talking about responsibly using resources)

- slower cruise (or more consumption)

my2cents, maybe someone can point me at a few links or something to read up on.
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  #71  
Old 06-29-2006, 02:23 PM
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Quote:
Originally Posted by Leon
FIXED GEAR:
+ nothing to go wrong (or very VERY little)

+ easier to build

- plane ugly

- more fuel consumption (talking about responsibly using resources)

- slower cruise (or more consumption)

my2cents, maybe someone can point me at a few links or something to read up on.
I dun think plane ugly
speed difference - can't wait to have some plane good numbers, i can believe 10 knots, can't believe more between PROPERLY dared and retracts
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  #72  
Old 06-29-2006, 02:59 PM
Leon Leon is offline
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it'd be hard to get exact numbers on that.

you'd need the exact same aircraft with the exact same engine flying at the same time both will full throttle.
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  #73  
Old 06-29-2006, 03:25 PM
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Quote:
Originally Posted by Leon
HYDRAULIC:
+ faster actuation than electric (gear cycle time decrease) [i think ]

+ less load on the electrical system

+ manual override possibility, either by CO2 pressure bottle or manual pump override

- in case of leakage in the system, the gear won't work at all, so your only change would then be gravity pulling the gear out, but then, depending on the gear system, it might not "lock" in the down position. But the locking is a thing that can be overcome (maybe by spring acting as a "gear down" actuator anyway, and thus locking the gear in place by a "clip"style latch or something)

- weight (i figure hydraulic system is heavyer than electric system)
All this depends on the application the system is in. Out of our 6 planes, 3 are electric retract, 3 are hydraulic (2 engine driven, 1 electro-hydraulic). The hydraulics on a whole are normally faster actuating than the electric ones, however that is not always true, it depends on how you size your pump and cylinders.

A big plus is that you dont have to do straight runs of the hydro lines, so you can run them around and through spaces that are already present.

Another big plus is that they are not totally interconnected. You can hang up one of the gear and the rest will come down normally. This doesnt really help you if you hang a main, but if you hang the nose it can be a lifesaver and money saver over interconnected electrics.

We will discuss weight under electric.

Quote:
ELECTRIC:
+ less to go wrong because no leakage possibility

+ lighter than hydraulic system

+ easier "infrastructure" with cables being alot easier to work with than hydro lines.


- high electrical load (this is just a guess from my POV and expereience)

- slower actuation

- no emergeny actuating possibility (no way to "pump" the gear, but alot less to go wrong in the first case, cables don't tend to leak very much) but on the other hand it's a binary system. either it works or not, it cant work a little like hydro could (again guessing this fact)

I don't know how electrical actuation actually works, but I think it must be by some sort of sprocket system or similar, so it probably won't work on gravity.
Weight: Can be false. In electric gear you have gear boxes, torque shafts, motors, gears, etc. One of our planes can be converted to hydraulic and it will actually be 25lbs lighter by doing so. I'd venture a guess to say that hydraulic fluid and line is lighter foot for foot than the torque tubes.

Electrical load can be an issue, however it is a short time that the load is present. The battery can easily absorb the load and recover.

Here is a huge disadvantage to electric systems.... They normally are totally interconnected. If you hang up one landing gear, nose, left main or right main it can hang the whole system and normally will break something.

Manual actuation is possible. If a plane has retract gear it has some form of manual actuation. In electric gear it is normally by means of a crank or a ratcheting crank which manually turns the torque shafts.

Quote:
FIXED GEAR:
+ nothing to go wrong (or very VERY little)

+ easier to build


- plane ugly

- more fuel consumption (talking about responsibly using resources)

- slower cruise (or more consumption)

my2cents, maybe someone can point me at a few links or something to read up on.
Ugly is subjective.

I wouldnt get into the more fuel consumption and cruise as the people here in the know say that well faired gear will be almost on par with retract gear.

When I make it home I'll post the gear diagram pages from the service manuals for our Merlin II (Electric Retract) and Merlin III (Hydraulic retract) so you can see what a certified retract system basically looks like.
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  #74  
Old 06-29-2006, 03:28 PM
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Quote:
between PROPERLY dared and retracts
PROPERLY fared

Lots of chatter about the pros and cons. My view - more complex for more build time, costs twice as much. Less range due to using fuel storage area. Put the hard points in the center spar when you build it. If you get bored of flying and want to change to retracts later it's easier.
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  #75  
Old 06-29-2006, 03:32 PM
Leon Leon is offline
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Thank you JohnC, very informative, as always! I'll be waiting for those pictures
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