Originally Posted by Eflyer_75214

Dag, looks like you are still off on the pivot points a little which is changing the load as the gear moves or is it just me imagining it. Seems to stutter a little along the way. Course, that may have been low pressure tests also. But still very impressive.

Ron

I have to ask, and I may not understand this as well as you, but what does the pivot points have to do with how smooth the gear moves??? This is a mock-up with out any nylon washers, or bearings to keep the friction down. The reason for the stutter is that the main axle on the strut is just a grade 8 3/8 bolt with no nylon bearing. As the load increases so does the friction. I calculated the pivot points so the the lowest possible load would be on the gear strut from 60-90 degrees. Unless I have a pivot point conflicting (binding) it would have nothing to do with how smooth it operated. The load will always change on the pivot points, the hardest pull is 15%, then again from 75%-100% of it's travel.

And when you say pivot point you may be meaning their bearings, and not geometry.

Real ones are not 100% smooth (the last one is funny):

Landing gear retraction test 1 (0 min 27 sec)

http://www.youtube.com/watch?v=TZNjrQfTP5s

Boeing 767 landing gear failure, disaster averted at Canadian MRO (0 min 31 sec)

Thanks, DAG

Originally Posted by ska2000

Me, I don't give advice, I only TAKE! LOL

Dag, please share what you're using to cut out the phenolic? Man that's pretty work. Do you have your own laser? And I have to add serious kudos to your son. How cool is it to have a helper around who can cut out formers for you?

Tom

I use my little 9" band saw I got at Home Depot, I can cut for about 6 hours on phenolic before having to change the blade.

Thanks, DAG

Wow, interesting! I see what you mean about full-scale not being smooth either, I guess in the end physics is physics and the scale of the object doesn't change the rules. The "jerk" when the gear is both initially started moving down as well as initially started moving up seems more due to the pivot point rotating from neutral point and causing motion...

Jack

Originally Posted by jfetter

Wow, interesting! I see what you mean about full-scale not being smooth either, I guess in the end physics is physics and the scale of the object doesn't change the rules. The "jerk" when the gear is both initially started moving down as well as initially started moving up seems more due to the pivot point rotating from neutral point and causing motion...

Jack

The jerk that you are seeing is more likely caused buy the combination of sequence valves both hydraulic and electronic. As well as different sized actuators.
Smaller actuators are used to unlock the gear, so it can retract. you also don't want the gear retracting through closed gear doors. The jerky-ness that you are seeing occurs as hydraulic press is applied and removed from different actuators during the cycle. Remember that although all three landing gear are retracting simultaneity; they are not synchronized. to happen at exactly the same time.
Rick

Originally Posted by dag214

Very cool, but I was hoping to use the electronic ones. I may just have to go in that direction.
I really want one of these:
http://www.dreamworksrc.com/catalog/...oducts_id=1491

Just can't get them to respond to any of my 5 e-mails. Does anyone else know where I can get 3 of these???

Thanks, DAG

Dag, this might be the solution to your cycling problem with your gears:

http://www.wingspanmodels.com/Produc...ronics/LG.html

Saul

Originally Posted by sml

Dag, this might be the solution to your cycling problem with your gears:

http://www.wingspanmodels.com/Produc...ronics/LG.html

Saul

Thanks,
I was looking at that yesterday. I think I am going with the ultra precision valve system.

Thanks, DAG

Wow !!

Could you imagine the landing gear doing like that in the third video !!!!

Dag, your mockup is much smoother than those real ones !!

Great work Dag !!


Seeya, Tim

Originally Posted by RiBell

The jerk that you are seeing is more likely caused buy the combination of sequence valves both hydraulic and electronic. As well as different sized actuators.
Smaller actuators are used to unlock the gear, so it can retract. you also don't want the gear retracting through closed gear doors. The jerky-ness that you are seeing occurs as hydraulic press is applied and removed from different actuators during the cycle. Remember that although all three landing gear are retracting simultaneity; they are not synchronized. to happen at exactly the same time.
Rick

I really think it is caused by the cam rotating past TDC, or the equivalent. With the weight on it and the slight play between parts it seems likely when you add it all up along with the pendelum movement increasing as it moves past TDC that you would see a sudden jerk (or at least rapidly increasing movement which would appear "jerk"-ish at normal speed)...

Jack

Here is a small update,
Work has me slammed, but I did get my 3D drawing exported to see if it can be CNC. Gary at Morganmill is helping me with importing my 3D CAD into his CAM, if it work the parts will look like this. Also last night I test fitted my new firewall and it fit perfect.

DAG

If all goes as planned this is what version 7 will look like after the parts are CNC.

The reason for 4 air cylinders is that a great retract expert from up north said that if you can not cycle the gear at 50 psi keep adding air cylinders until you can. With 4 she goes up at 48 psi, with 3 it took 65 psi.

Rock On!
DAG

Originally Posted by Tim Farrar

Wow !!

Could you imagine the landing gear doing like that in the third video !!!!

Dag, your mockup is much smoother than those real ones !!

Great work Dag !!


Seeya, Tim

Thanks Tim,
Yes that 3rd one is wild, I guess they would just have to have some one fly up with a Stearman and pull the door out of the way

DAG

Interesting to follow along.

Now I have to ask, if you need 4 air cylinders per main gear (8) and 2 (?) for the nose (total 10?), how big is the air tank to power all this and how many cycles can you do before no air left?

I've never had the pleasure to play with air retracts.

Originally Posted by Hepdog

Interesting to follow along.

Now I have to ask, if you need 4 air cylinders per main gear (8) and 2 (?) for the nose (total 10?), how big is the air tank to power all this and how many cycles can you do before no air left?

I've never had the pleasure to play with air retracts.

I will have 8 air tanks for the left and right mains, and 3 for the nose gear, 2 as primary and 1 for reserve. The 8 for the mains will be split so that 6 are primary, and 2 are reserve. On the mains it only takes 1 cylinder to get it down and locked.

Thanks,

DAG

Originally Posted by dag214

I will have 8 air tanks for the left and right mains, and 3 for the nose gear, 2 as primary and 1 for reserve. The 8 for the mains will be split so that 6 are primary, and 2 are reserve. On the mains it only takes 1 cylinder to get it down and locked.

Thanks,

DAG

GEEZ

I guess there is no shortage of real estate to put all this stuff though eh

Originally Posted by Hepdog

GEEZ

I guess there is no shortage of real estate to put all this stuff though eh

The cubic inches in my wing is huge, and I have a ton of space in the front of the fuse just ahead of the bomb bay.

I will post a 3D of the air cylinder layout later tonight.

Thanks, DAG