S-3 Viking Landing Gear hydraulics question

[eflight]

Can anyone here describe how the Landing gear on the S-3 Viking is actuated?  I'm tying to build an RC model of the Viking and am stuck on the gear design. 

 

I'm trying to figure out how the gear is actually rotated.   I only see the one hydraulic cylinder on the bracing strut and that does not appear to have enough throw to retract the gear fully.  I modeled it in fusion 360 and its not enough to move it.

 

The main strut and shock absorber are hinged to the bulkhead but do not appear, at least  to me, to have any hydraulics that would rotate them.

 

What am I missing

 

Thanks

 

 

[habu2]

As you probably know, the S-3 landing gear was designed by LTV so it strongly resembles both the A-7 and F-8 gear design. Not near my references ATM...

[Tailspin Turtle]

I'm pretty sure that the "small hydraulic cylinder" both unlocks the "locking brace" and causes it to double up, pulling the main strut into the wheel well, along with closing the doors.

[AV O]

Here's a not so complicated one :

https://www.youtube.com/watch?v=vwK5SDyKL98

 

Edited March 3 by AV O

[eflight]

18 minutes ago, Tailspin Turtle said:

I'm pretty sure that the "small hydraulic cylinder" both unlocks the "locking brace" and causes it to double up, pulling the main strut into the wheel well, along with closing the doors.

 

I modeled it as best I could in Fusion 360 and the hydraulic cylinder does not appear to have enough throw to move the gear into the gear bay.   That swing 90 deg aft has to come from somewhere else.

 

 

[habu2]

The locking strut retraction cylinder, when retracting, turns a bellcrank which unlocks the locking strut and then folds the locking strut in an upward direction. I think by playing with the mechanical advantage of both the upper and lower bellcranks you can get the range of motion you need. I'm basing this on my background in kinematics and mechanical engineering. 

 

The gear doors are operated by a separate cylinder in the upper/inner corner of the gear bay. This cylinder rotates a common shaft with rods attached to the gear doors. You can see the door actuation cylinder and shaft in the pics in this walk-around:

 

https://inchhighguy.wordpress.com/2021/08/01/lockheed-s-3-viking-walk-around-part-iv-main-gear-wheel-wells/

 

.

Edited March 3 by habu2
added link

[BillS]

Habu nailed it. I pulled the attached from NATOPS. Though not real detailed, it gives a good explanation of gear actuation. The one actuator in your images does the work. Springs and air loads assist with alternate extension.

[habu2]

Nice view of the underside of the linkage

 

http://nabe3saviation.web.fc2.com/images3/twas3-65.jpg

 

[Collin]

16 hours ago, BillS said:

Habu nailed it. I pulled the attached from NATOPS. Though not real detailed, it gives a good explanation of gear actuation. The one actuator in your images does the work. Springs and air loads assist with alternate extension.

OMG......major flashback....and I fell asleep.

 

Cheers

Collin

[eflight]

Thanks all for the help with this.

 

After more hours than I care to admit I finally got the gear to work in Fusion 360.   One of the big issues I had was that the gear resting position is not when its sitting on the ground , but when its flying.  The shock absorber needs to be fully extended for the gear to swing back all the way.  And I also found that the linkage on that locking knuckle is very sensitive to ratios between pivot points.

 

Much respect to the guys that did the original design using slide rulers and paper blueprints.

 

Now comes the really hard part, trying to make a working model of it.

 

Again, thanks all for the help

 

Edited March 4 by eflight

[Tailspin Turtle]

My favorite is this one: https://tailhooktopics.blogspot.com/2019/09/douglas-xb-4243-main-landing-gear.html. It's amazing what you can visualize with things like a paper clip and an eraser: https://www.historynet.com/tough-turkey-why-grummans-tbf-avenger-was-the-ultimate-torpedo-bomber/