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Old Jan 22, 2009, 05:10 PM
It only takes one good idea
dag214's Avatar
Fishers, Indiana
Joined Oct 2004
5,869 Posts
Quote:
Originally Posted by redflyboy122
what is the main gear shaft made of? it looks black in the pics and video. aluminum? looks pretty cool!
The struts and push rod is 6061 T6 shimmed with nylon 6, the axles are 1/4" landing gear wire.

Thanks, DAG
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Old Jan 22, 2009, 05:13 PM
It only takes one good idea
dag214's Avatar
Fishers, Indiana
Joined Oct 2004
5,869 Posts
Quote:
Originally Posted by dag214
Here is a video demo that shows the strut working. There is at this time a 5 pound compression spring, the actual flight spring will be a 35 pounds with a total max load compression of 60 pounds.
http://www.youtube.com/watch?v=sxV2KuAjxII
DAG
Just wanted to add a note.

The main CF strut has 6061 t-6 inserts that will hold the attachment points in place when attached to the gear actuator.

DAG
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Old Jan 22, 2009, 05:37 PM
It only takes one good idea
dag214's Avatar
Fishers, Indiana
Joined Oct 2004
5,869 Posts
Quote:
Originally Posted by gtfreeflyer
It would probably be hard to get all those wheels spinning at the same rate before dropping it, so perhaps the treadmill will work (or your belt sander, just turn the sandpaper around so you get the smoother side. That probably goes more than 12 MPH). To answer you above, yes you would spin up the wheels backwards, and then drop the entire loaded gear. When the wheels contact the ground, they won't stop immediately because they have some inertia going. The slipping on the wheel will cause a drag force on the strut and you can see if the strut bends during that moment. With the treadmill, once the wheels spin up to the treadmill speed, all you are testing is high speed taxi loads, not landing loads. If you want to do some math, you can figure out that 40 pounds on each strut, landing at 10 ft/sec (just a number a picked), will create a 200 pound landing load on the strut (also a number i just picked out of thin air). For that, you can then load 200 pounds onto the strut and run it on the treadmill (without dropping the gear) to create a landing condition, but this condition lasts only for a fraction of a second, so running it longer than that would be unnecessary.
I get it, I will try both the belt sander and the 200 pound load test, but I want to do some math first to see if 200 pounds is correct. If the max weight of the plane is 75 pounds and she will hopefully aways be hitting on the mains first then I should look at 37.5 as a even load, but if I were to land hard on just one then that could be most the 75 pound load, and if I remember correct about a 6"-12" free fall would equal just about the worst landing, because in real flight the wings are still flying some.

Sooo,
If I take 75 pounds and free fall it 12" I need to calc what that load would be, right????

Thanks a ton,

DAG
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Old Jan 22, 2009, 05:38 PM
I fly, therefore, I crash!!!
SteveT.'s Avatar
San Jose, CA
Joined Jan 2008
26,374 Posts
Hi Dag...

Great job on the gear...as usual!!

Quote:
At lunch today I found some 3.5" wheels. I think I will test with these. Not getting much done this week, work has me hammered

You seem to get more done in one evening than I do in a week or more.. I have and Acromaster that has been sitting on my work bench for a month (or more) and still not finished. Of course I also had shoulder surgery during that period of time.

SteveT
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Old Jan 22, 2009, 06:17 PM
Vintage Flyer
Indiana
Joined Jan 2005
1,674 Posts
Quote:
Originally Posted by Draknkep
Hi Dag...

Great job on the gear...as usual!!




You seem to get more done in one evening than I do in a week or more.. I have and Acromaster that has been sitting on my work bench for a month (or more) and still not finished. Of course I also had shoulder surgery during that period of time.

SteveT
I see I'm not the only one with this problem!
My 1/4 scale Lanier Laser has been setting a long time too!

Hey Dag, those gear tests are impressive!
Yessir, Harrison Storms was quite a guy!
There's in an interview with him in the video,"The Rocket Pilots"
He spoke about the Russians putting up Sputnik, and he said "We could hear it beep as it went over,of course there wasn't anything we could do about it but we didn't like it one damn bit!"
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Old Jan 22, 2009, 06:37 PM
It only takes one good idea
dag214's Avatar
Fishers, Indiana
Joined Oct 2004
5,869 Posts
Quote:
Originally Posted by Ercoupe Ed
I see I'm not the only one with this problem!
My 1/4 scale Lanier Laser has been setting a long time too!

Hey Dag, those gear tests are impressive!
Yessir, Harrison Storms was quite a guy!
There's in an interview with him in the video,"The Rocket Pilots"
He spoke about the Russians putting up Sputnik, and he said "We could hear it beep as it went over,of course there wasn't anything we could do about it but we didn't like it one damn bit!"
Ed,
The best book ever written about how a engineer gets thing done is a book about Harrison Storms called Angle of Attack.

He was the engineer on the X-15, X-b70, AGM-28 Hound Dog, F-86 and I think the F-100, but don't quote me on that.

To help pay for college, he worked nights at the Caltech wind tunnel. There he performed work for the various Los Angeles aviation companies. His dedication in solving an aerodynamic problem with the engine cooling intake for the P-51 Mustang caught the attention of an engineer at North American Aviation. Storms joined North American. Dutch Kindelberger and Lee Atwood ( no relation to me), the team that ran North American, were impressed with him, and his engineering skills.

DAG
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Old Jan 22, 2009, 08:42 PM
Registered User
USA, WA, Edmonds
Joined Aug 2008
1,883 Posts
Do these wheels have much inertia? I don't know if its too necessary to do the drop test with spinning wheels. If there isn't much rotational inertia then there shouldn't be too much drag or springback loads. But, if you have the equipment then why not.

I'm guessing we won't be seeing this with your aircraft.

F-18 Drop Test (0 min 13 sec)


Here's another angle:

F-18 Drop Test (Slow Motion) (0 min 23 sec)
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Old Jan 22, 2009, 11:37 PM
Vintage Flyer
Indiana
Joined Jan 2005
1,674 Posts
Quote:
Originally Posted by dag214
Ed,
The best book ever written about how a engineer gets thing done is a book about Harrison Storms called Angle of Attack.

He was the engineer on the X-15, X-b70, AGM-28 Hound Dog, F-86 and I think the F-100, but don't quote me on that.

To help pay for college, he worked nights at the Caltech wind tunnel. There he performed work for the various Los Angeles aviation companies. His dedication in solving an aerodynamic problem with the engine cooling intake for the P-51 Mustang caught the attention of an engineer at North American Aviation. Storms joined North American. Dutch Kindelberger and Lee Atwood ( no relation to me), the team that ran North American, were impressed with him, and his engineering skills.

DAG
Hi Dag,
I think I have that book and have read it.
Good book!
Both Lee Atwood and Harrison Storms are portrayed in Tom Hanks mini -series "From The Earth to the Moon"
I have it on DVD, great program!
I've got to get down there and see this balsa monster you're building!
I love your T6 video.
Did I ever tell you that my best buddy up here, Tim used to be on the Ft Wayne Air Racing Team, when they competed at Reno in 1985 , 1986, and 1987.
Tim drove the semi out with all the extra equipment, tools, etc.
While out there at Reno, Bob Hoover used to hang out with them, and took Tim up as his passenger during one of his performances.
Tim has a picture of him and Bob Hoover on his bar in his basement, and told me, you can take my models, you can take my dogs, you can take my wife, but if you take that picture of Hoover and I, you'll never get to the top of the stairway alive!! LOL!
John Dilley, a local P-51 pilot and the chief pilot on the Ft Wayne air racing team designed a special P-51 known as "VENDETTA", half P-51, half Learjet!
But fate played it a strange hand.
Had it survived and been totally engineered out, there was no doubt in anyones mind that it would have been the "FASTEST" internal combustion propeller driven airplane that ever flew.
Itdid make a local flight at 80% manifold pressure and an airspeed of 540 mph in straight and level flight.
During it's first trip to Reno it suffered some technical issues and never raced again at Reno.
John was confident that it would break 600 mph, but fate dealt Vendetta a bad hand of cards one day and John put it down in a soybean field just north of my house, and it never flew again as Vendetta. John walked away from it though.
It was later resurrected by Gary Levitz under the name of Miss AshleyII but Gary put a Griffon engine with contra-rotating props and it was MUCH HEAVIER than John had built it as Vendetta.John had a Rolls Royce Merlin it.
Unfortunately Gary died in it when it crashed at Reno after he overstressed it during the start of the Gold Cup unlimited race in I think it was 1998.
The landing gear and was custom built for it, as the wing was from a Learjet model 23 I believe.
I've got a video of Vendetta's first flight somewhere.
When John quit flying P-51s, he was the highest flight time P-51 pilot in the world.
He flew LOU IV for awhile until they sold it.
Nowadays John manages Ft Wayne Air Service and enjoys flying electric RC helicopters and small indoor electric airplanes.
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Old Jan 23, 2009, 01:18 AM
"NAVY CHIEFS"
rc_man1's Avatar
NAF Atsugi, Japan
Joined Jul 2005
628 Posts
F/A-18E Drop

I have actually seen that for real. I work on the F/A-18E and one day on the Carrier deck one of our pilots caught the arresting gear but pu;;ed up and he was about 15 feet off the deck when he was put to a complete stop in the air and well the Drop test was performed HEHE. We had alot of work as Maintenance guys due to that drop.

Mike
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Old Jan 23, 2009, 06:54 AM
It only takes one good idea
dag214's Avatar
Fishers, Indiana
Joined Oct 2004
5,869 Posts
Well it was a late night.
My landing gear looks like it will work, I will start testing this weekend.
The motor placement issue is still a huge concern for me. I have had a offer to have my shafts machined for me, and I am sure they would be a 1000 times better than I could make, but in the back of my mind I still wonder about that bearings, and the way they will be supported. I made a small test mock-up of a motor/bearing/ bearing layout and with the mid bearing moved all over the place the mid bearing housing still showed where it was taking a beating. The housing wants to separate from the wood rib.

So I am still up in the air about the mounting of the Hackers, and I need to keep moving forward if I am to go to the SEFF now that my San Fran trip was canceled .

I am now about a week behind because of the re-design of the gear, and the motor placement. And with work taking so much time (which is good, got pay the bills) I just want to stay as much on schedule as possible.

DAG
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Old Jan 23, 2009, 07:53 AM
I can fly anything..... Once!
FL62's Avatar
United States, AZ, Queen Creek
Joined Feb 2004
1,132 Posts
Damon - if you DO decide to mount the motors at the back, directly to the firewall, I would strongly recommend using the rear bearing support on the motor, since the prop's axial loads would be 100% on the motor. We could also get you some of our Aluminium cage-mounts with the bearing support integrated.


Mike
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Old Jan 23, 2009, 08:08 AM
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Angelo's Avatar
Chicago, IL
Joined Nov 1999
2,049 Posts
Quote:
Originally Posted by dag214
I made a small test mock-up of a motor/bearing/ bearing layout and with the mid bearing moved all over the place the mid bearing housing still showed where it was taking a beating. The housing wants to separate from the wood rib.
So you are only using one mid-bearing? I read of a model sailplane designed a few years ago. It was a pusher, prop mounted in the tail, with the motor in the front. It used seven bearings to support the drive shaft.

My guess is that you are still having resonance problems, even with the one mid bearing mounted off center. Can you adding a couple more bearings? Maybe that will fix it.
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Old Jan 23, 2009, 09:40 AM
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Joined Dec 2008
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I don't know if I'm thinking about this correctly Dag, but the shaft question seems like an easy one to answer to me. If it's possible to leave out a part of system that you know might cause problems (e.g. a shaft failing and destroying a nacelle/wing) and still achieve overall design goals in terms of thrust, wing loading, scale appearance, then leave out that part. So, I'd ditch the shafts for sure if it was me, but I'm not an engineer, so I may not be looking at this correctly.
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Old Jan 23, 2009, 10:07 AM
Old Submariner
United States, WI, Milton
Joined Dec 2007
577 Posts
Motor Bearing Support

DAG:

After following your build for many months to say I am in awe is a terrible understatement. I have been building and flying aircraft for over 60 years ( I am 73 ) and flying RC for over 30 years, 1/2-A to 50cc.

I had the extreme pleasure of seeing and HEARING a B-36, the A-model I assume when I was 10 or eleven years old at the air races in Miami, FL.
It was in 1947 or`1948 I believe, it has been a long time. Anyway at the close of the days flying there was a USAF fly over. Several B-17's, a short pause to clear the airspace then a single B-29 another pause a little longer and then this really strange fluttering sound that grew louder and louder and the B-36 came into sight, was probably about 2000 feet horizontal distance and very low maybe 500 feet. I will never forget the feel & sound, that low rumble and sort of fluttering. This was followed by a longer airspace clearing and then a low pass of four P-80 Shooting Star's ( Still "P" in those days) very low and very fast by comparison. I am really just guessing at the year but it was several years after the war.

About your motor shaft bearing problem. As I am sure you know, a long shaft tends to "whip" which is why you have mid-shaft support. Have you considered using a torque tube for bearing support ? This would not onlly stabilize the whipping forces but would also provide more surface area for the entire power train to be supported. A aluminum tube and sleeve cut to proper lengths could position the bearing (or bearings) with set screws to keep everything tight and prevent the bearing outer race rotation. You are probably too young to remember but Ford addressed these considerations for the drive shaft to the differential on their Ford, Mercury and Lincoln automobiles in the 1940's and 1950's.

Anyway just a thought, keep up the fantastic work and thank you so much for sharing with all of us, and your patience with all of our tool shed engineering thoughts. Even though I am a retired engineer I still like to mentally address design problems.

Best regards,

E T

Milton,WI
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Old Jan 23, 2009, 10:15 AM
Übung macht den Meister..
Deuce's Avatar
United States, OR, Fairview
Joined Jul 2006
2,996 Posts
Quote:
Originally Posted by dag214
... The motor placement issue is still a huge concern for me. I have had a offer to have my shafts machined for me, and I am sure they would be a 1000 times better than I could make, but in the back of my mind I still wonder about that bearings, and the way they will be supported. I made a small test mock-up of a motor/bearing/ bearing layout and with the mid bearing moved all over the place the mid bearing housing still showed where it was taking a beating. The housing wants to separate from the wood rib.

So I am still up in the air about the mounting of the Hackers, and I need to keep moving forward ...
Quote:
Originally Posted by FL62
Damon - if you DO decide to mount the motors at the back, directly to the firewall, I would strongly recommend using the rear bearing support on the motor, since the prop's axial loads would be 100% on the motor. We could also get you some of our Aluminium cage-mounts with the bearing support integrated.


Mike
I like your original idea of the rear shaft bearing taking the thrust load (echoing Mike's additional concern about thrust loads!), but also share your concern about possible whipping. How a bout a shorter shaft, say about 3"-4", so you can incorporate that rear "thrust/shaft" bearing without the whipping concerns?

Just my 2 cents...

James
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