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Old Feb 07, 2009, 03:43 PM
sml
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Joined Jan 2007
340 Posts
Quote:
Originally Posted by dag214
What I did last night.
This is a rendering of the new motor mounts, My son got them cut out for me last night, will take pics soon.

DAG

Dag,

I really like the idea of using tubing to bring air to the motor to help cool it. That is such a simple but ingenious idea!! Kudos

Saul
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Old Feb 07, 2009, 04:00 PM
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Angelo's Avatar
Chicago, IL
Joined Nov 1999
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Most planes don't have this issue, since the motor's in the nose. Even most pushers are pretty well exposed. DAGs will be completely enclosed, so it's really necessary. I like the facts he's using the actual scale scoops and not some "cheater" holes near the motors.
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Old Feb 07, 2009, 04:41 PM
It only takes one good idea
dag214's Avatar
Fishers, Indiana
Joined Oct 2004
6,062 Posts
Just learned a few things about mock-ups. I ran a single servo to cycle the gear main pivot to make sure everything worked as planned, went perfect. Then added air to see how she worked, perfect. Then add the main gear strut, Kaboom! See I made this mock-up out of mostly phenolic that is 1/8" because it is cheaper than throwing away aluminum, I made my secondary pivot arm out of the stuff. When the main gear was about 1" from getting completely retracted the 2 arms snapped and the gear swung down. I know the gear will work as I tested this at 35 PSI. I will make new arms out of aluminum.

This kind of testing is very cool, I really see what things work and don't.

Rock ON!

DAG
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Old Feb 07, 2009, 06:45 PM
HAL... Open the damn doors!
jfetter's Avatar
Miramar, Florida
Joined Jul 2007
8,517 Posts
Quote:
Originally Posted by dag214
Just learned a few things about mock-ups. I ran a single servo to cycle the gear main pivot to make sure everything worked as planned, went perfect. Then added air to see how she worked, perfect. Then add the main gear strut, Kaboom! See I made this mock-up out of mostly phenolic that is 1/8" because it is cheaper than throwing away aluminum, I made my secondary pivot arm out of the stuff. When the main gear was about 1" from getting completely retracted the 2 arms snapped and the gear swung down. I know the gear will work as I tested this at 35 PSI. I will make new arms out of aluminum.

This kind of testing is very cool, I really see what things work and don't.

Rock ON!

DAG
Looking good! I see you've also modified the servo plate and made it much larger, I wasn't sure the older design with so much cut away was going to be strong enough, even when machined from aluminum...

Jack
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Old Feb 07, 2009, 11:24 PM
It only takes one good idea
dag214's Avatar
Fishers, Indiana
Joined Oct 2004
6,062 Posts
Here is my gear test. It was with 2 air cylinders, 1 servo, and the PSI was 60. After testing I believe I will ditch the idea of the servos. When the retract first comes down it puts a huge load on the servos. I believe I will add 1 more air cylinder and use it on a separate air system for my redundancy. This gear design is great, just need to make it as solid as I can.
2 7 09 B 36D main gear test (3 min 0 sec)


DAG
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Old Feb 07, 2009, 11:41 PM
r/c...the ultimate hobby!
redflyboy122's Avatar
washougal, WA
Joined Jan 2006
342 Posts
so awesome!!!
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Old Feb 07, 2009, 11:57 PM
sml
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Joined Jan 2007
340 Posts
Quote:
Originally Posted by dag214
Here is my gear test. It was with 2 air cylinders, 1 servo, and the PSI was 60. After testing I believe I will ditch the idea of the servos. When the retract first comes down it puts a huge load on the servos. I believe I will add 1 more air cylinder and use it on a separate air system for my redundancy. This gear design is great, just need to make it as solid as I can.
http://www.youtube.com/watch?v=ZOwq-SoqKeQ

DAG

Dag,

If you are going with all air cylinders you may want to add a feature that is available in all Robart retracts called "air up spring down" in case there is a loss of pressure, i.e. pin hole in one of the tubing lines. You may want to run a pressure loss test once you have included the "air up spring down" feature.

Saul
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Old Feb 08, 2009, 12:15 AM
Bi-Planes
Tim Farrar's Avatar
Houston Texas
Joined Apr 2006
1,589 Posts
Dag, I am speechless !!!!

I cant believe you made that !!!

That is so cool !!!

Just amazing !!


Seeya, Tim
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Old Feb 08, 2009, 07:02 AM
Old Submariner
United States, WI, Milton
Joined Dec 2007
596 Posts
Retract System

Dag:
Just saw your latest gear retraction system. Looks great but watching the cycle closely it it is obvious the load is variable depending on cycle point. With the investment in time and labor you have here (not to mention the cash) I would seriously consider a Acme Screw and Block with limit switch controls. The screw would provide serious "lock" capability in any position, reliability is unsurpassed.

Most of the damage I have seen to projects that did not begin to approach yours in beauty and complexity, has been from landing gear failure.

A side benefit of the screw/block would be very realistic cycle time which could be set to the rate you choose simply by gear size selection.

The whole gear package and conrtols could be fabricated on the bench, cycle tested and then simply bolted in.

Just a thought form the "Peanut Gallery".

Best,

E T
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Old Feb 08, 2009, 07:16 AM
It only takes one good idea
dag214's Avatar
Fishers, Indiana
Joined Oct 2004
6,062 Posts
Quote:
Originally Posted by teeceeveecee
Dag:
Just saw your latest gear retraction system. Looks great but watching the cycle closely it it is obvious the load is variable depending on cycle point. With the investment in time and labor you have here (not to mention the cash) I would seriously consider a Acme Screw and Block with limit switch controls. The screw would provide serious "lock" capability in any position, reliability is unsurpassed.

Most of the damage I have seen to projects that did not begin to approach yours in beauty and complexity, has been from landing gear failure.

A side benefit of the screw/block would be very realistic cycle time which could be set to the rate you choose simply by gear size selection.

The whole gear package and conrtols could be fabricated on the bench, cycle tested and then simply bolted in.

Just a thought form the "Peanut Gallery".

Best,

E T
Thanks,
I did a ton of research on jack-type screws and the problem is with the weight and the system that will activate it. I experimented with a 6" stroke jack-screw and it has a ton of power (150 pounds of static force in both directions). It is the system of limit switches and contactors that would be a problem in the long run. But the weight is the huge problem. The lightest one I could find was 2.8 pounds. And one other reason with a single jack-screw there is no redundancy, but if someone can find me one that weighs about 1 pound and has at least 75 pounds of force I would consider it.

I know that the air system will work once I get the right design. I figured out late last night that if I have 3 air cylinder with 2 off of one air tank and valve, and the other air cylinder on another air tank and valve the single air cylinder will still get the gear down and locked.

Thanks, DAG
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Old Feb 08, 2009, 07:44 AM
It only takes one good idea
dag214's Avatar
Fishers, Indiana
Joined Oct 2004
6,062 Posts
I just thought that I need to say something, the idea of having the second air system as back-up is not my idea, Century Jet Models has been doing that for a long time on there big projects. I got an e-mail saying that it was a great idea, I wish it was mine, but it has been done a bunch by Century Jet Models.

Thanks all,

DAG
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Old Feb 08, 2009, 07:46 AM
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N99JH's Avatar
Hartsville, SC
Joined Apr 2006
902 Posts
DAG
Have you talked to Hank Like of Like Design about his electric/screw landing gear?
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Old Feb 08, 2009, 08:08 AM
It only takes one good idea
dag214's Avatar
Fishers, Indiana
Joined Oct 2004
6,062 Posts
Quote:
Originally Posted by N99JH
DAG
Have you talked to Hank Like of Like Design about his electric/screw landing gear?
No I haven't but know of his gear, one thing to keep in mind is that it is taking over 75 pounds of force to get these wheel up. The strut weighs 1.2 pounds, the you put 4 wheels at the end of it weighing 10 ounces each, and you have a heck of a load. I may give him a call about how he controls his gear, but his equipment looks like it would not be strong enough to get the job done, and with a electric system only there is not backup. In the beginning I did not want air only because when they first plop down they may hit my gear doors, but I have found some cool electric sequencers on line and think I have that figured out. I won't say names but I have e-mailed 5 times a jet company in FL. that has a nice door sequencer and heard nothing. I know that JOMAR and wingspan has good ones, any other out there?

Thanks, DAG
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Old Feb 08, 2009, 09:26 AM
It only takes one good idea
dag214's Avatar
Fishers, Indiana
Joined Oct 2004
6,062 Posts
Here is version 5 of my main gear, I think (99.5%) that this will be it.

I am plotting out the side plates as I type this and will try to be testing this design later this afternoon.

This will be about 4 ounces lighter.

Thanks, DAG
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Old Feb 08, 2009, 02:35 PM
War Eagle!
sneasle's Avatar
United States, AL, Huntsville
Joined Sep 2006
2,923 Posts
http://www.servocity.com/html/linear_servos.html

They used to have more sizes then that available, may not be stocking them at this point in time.

Just an idea to consider, I have something similar bolted to the back of the 12' satellite dish in the yard to control it's direction, has been out in the weather for years and always worked.

edit:


Looking at their details, They are way to heavy and way to expensive for this... But they are nice to look at .
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