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Catalina Project

16 posts in this topic

Posted

Has anyone replaced the manual gear retraction mechanism with an electric linear actuator/ jack screw?  If so, did it work? What linear actuator did you use?

I'm having a hard time sorting out the forces it would be subject to. However it looks like it would be a relatively easy install and would be a lot nicer than the manual handle.

Mine, even though it moves freely requires more force that I want to apply every time I want to cycle the gear once I am flying this thing.

Chris Bolkan

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Posted

HEY CHRIS,

 

YES MINE IS MODIFIED TO ELECTRIC..WORKS GREAT

My actuator is a SKF CAT R 33x15/C12c

see this website page https://www.skf.com/binary/tcm:12-243108/index.html

 

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Posted (edited)

Sweet! I'm on it! Would you mind taking a couple photos of how you did the install from a couple different angles?

Thanks man!

Chris

Edited by ChrisBolkan

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Posted

I am having trouble finding the particular actuator you used. Can you re-check the number? The link leads to a blank page.

 

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Posted

Hey Chris, here a PDF version for you..on page 11 you will find the details. Today I will take some close-ups for you

actuator.pdf

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Posted

Thank you! I am sure from other posts I have been exposed to your name but I do not seem to know it. Since we are likely to be talking a bit and for a while, what's your name?

Thanks again!

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Posted

Hey Chris,, here some pictures of the install for you. When photos were taken the gear is in its "gear down" position. Also note the gear switch on the cockpit is a 3 way switch...switch in Gear up =-blue light on, gear up / switch in middle position=no power to system and all lights off / switch in gear down=gear down and green light on.

The switch mid position allows you to not have the bright gear up light on all the time. Also it allows you to partially extend the gear at any position between gear up and gear down. 

 

...my name, Laurent

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Posted

Thanks Laurent

It's crazy but my Catalina has gear up, down and "no mans land" indicator lights already in the instrument panel, but no wiring. They may have been intended for manual indication, but that seems unlikely. I think there was a future plan to go electric.

Does your actuator go through its complete end to end travel from gear up to gear down positions or do the microswitches limit the travel?

If it does go limit to limit is there internal protection inside the actuator to stop it and prevent damage to the actuator?

Or do the micro switches just turn on the position indicators?

I assume the gear up/down rocker is a cross wired DPDT switch?

Do you have a diagram of how you wired it?

I have a lot more questions but I don't want to overload you right off the bat!

Take care!

Chris

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Posted

Hey Chris,

the actuator travel is limited by the two end micro switches, they also switch the lights on the dash. The way I protected the actuator is by a 15A circuit breaker. That breaker will pop if the actuator hits it's end limits (limit micro switch not working) or if the actuator is energized gear down with aircraft on ground. Yes it is a DPDT crosswired switch plus a couple of relays, I'll get you the wiring next...have to do a bit of paper digging :)

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Posted

Thank you Laurent! Curious, do you remember approx what you paid for the actuator? I'm going to do the install but want to brace myself for the sticker shock! :-)

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Posted

Hey Chris, sorry I tend to forget the price of things....feel better that way. Also this actuator is quite old and i find a bit heavy. I am sure you can find a reasonably priced actuator with similar specs (boats have a wide selection, see trim tab actuator/engine lift actuator/hatch actuator etc....maybe you find a second hand one). The pull-push force to get the gear up/down is not much.....maybe 80-100Lbs. The strength needed from the actuator is mostly when landing at touch down...a bad hard landing will give you a static load of about 3600-4000Lbs. This number is what the actuator has to withstand in compression when retracted (gear down). Any 12v DC linear actuator able to handle 4000Lbs static load and a few hundred Lbs dynamic load will work just fine. You will need about 150mm / 5,9 inch travel. There are some with integral adjustable limit switches...less wiring and simpler installation than mine. If possible I would choose a waterproof one.

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Posted

That landing load number is the one I had no idea how to come up with. So thank you for that. I should be able to find an actuator. Also the travel number is very helpful. Thank you. I will also measure my actual travel. Don't forget your schematic! I am quite electrically inclined and can come up with a circuit myself, but I like getting and considering all ideas as that usually ends up with the best solution!

Thanks again

Chris

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Posted (edited)

I ended up not going with an electric jackscrew for the Catalina landing gear. After studying the manual I could not see how the helper spring was going to work very well with its weird angle change over the throw of the handle, and the builder never installed the spring plate to the floor of the plane so I did not have a mount for the other end of the assist spring. So I had an idea. I ended up using a used but not worn out landing gear bungie cord to provide the assistance. It works amazingly well! I am actually blown away. With the wheels off the ground, the lever is EASY to move from wheels down to retract and back. It will be no problem whatsoever in flight which was a big concern for me. It's so easy to move back and forth that I see no reason for electric retract. The assist is very strong and consistent because the percentage length change in the bungie is minimal so the assistance force throughout the range of motion is consistent and comes from the right angle throughout the range of motion. The bungie is completely out of the way when floor boards and seat panels are installed. A picture is attached.

I also completely rewired the Catalina and everything works except the tach which I need to sort out. Replumbed everything replacing all lines and leaky valves and primers. Started the engine for the first time since I have owned it and it runs beautifully (except for tach not working) And last but not least finally got the registration transferred to me and am in the process of getting the operating limitations updated for phase one fly off from my local airport.

So after years of inching along the ball is really starting to roll downhill towards the finish!

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Edited by ChrisBolkan
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Posted

Brilliant chris, keep at it and you will fly her soon:)

 

One question I have for you: why is your battery located that far back? The catalina is tail heavy and I found that the battery in the nose helps a lot on my Catalina.

 

L.

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Posted

Thanks! Yes the gear moves so easily from extended to retract it is amazing. I feel lucky that the idea to use a bungie came to me :-)

Regarding the battery, I don't know. I just took the fuse to the airport to put the wings on and I will do a W&B. and figure out if I need to move it or not. That's where it was. I'll move it if W&B says I should. Good call and thank you!

I have it all re wired and re plumbed, have run the engine so its pretty much ready to go. I just got an email from the FAA yesterday asking me what phase 1 fly-off radius I wanted! Can you imagine that? Since when do they ask? They have been wonderful to work with on this project.

 

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Posted

fantastic, I am excited to see/hear your cat in the air. Also I'd love to see your final W&B with the 582 engine fitted....see the difference with my 912 setup. Let me know if I can help you in any way for your 1st flight;)

P.s :phase 1 radius 500NM?

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