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02-23-2011, 08:17 PM
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Join Date: Jun 2005
Posts: 3,275
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I will give you a solution that will result in an immediate reduction in these events of perhaps over 90%:
Operate off of well-maintained paved surfaces.
Throw in converting to the newer gear leg/fork that provides 1" more clearance of the bottom of the gear leg, perhaps reinforcing the lower part of the front lower wheel pant to aid as a skid and recommended landing techniques and the reduction in these events could be over 95%.
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02-23-2011, 11:47 PM
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Join Date: Oct 2009
Location: Victoria, BC, Canada
Posts: 3,932
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Quote:
Originally Posted by Ron Lee
I will give you a solution that will result in an immediate reduction in these events of perhaps over 90%:
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Learn to fly with a tailwheel?
Just kidding, really... But I couldn't resist throwing it in... 
__________________
Rob Prior
1996 RV-6 "Tweety" C-FRBP (formerly N196RV)
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02-24-2011, 02:54 AM
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Join Date: Oct 2009
Location: Fort Myers
Posts: 370
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Quote:
Originally Posted by Ron Lee
I will give you a solution that will result in an immediate reduction in these events of perhaps over 90%:
Operate off of well-maintained paved surfaces.
Throw in converting to the newer gear leg/fork that provides 1" more clearance of the bottom of the gear leg, perhaps reinforcing the lower part of the front lower wheel pant to aid as a skid and recommended landing techniques and the reduction in these events could be over 95%.
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I can offer a solution that will result in a 100% reduction:
DON'T FLY AT ALL
Seriously though, neither "solution" is going to happen. We like flying and many folks don't have the nice runway option. Not logical to operate an aircraft that is "safe, as long as you restrict normal operations". It behooves us all to support nose leg design improvements.
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02-24-2011, 04:11 AM
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Join Date: Feb 2006
Location: Valley Forge, Pa
Posts: 636
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Paypal Fund
HI Barry & Chet,
Outstanding!!! Disregard all criticism and plow ahead ,Any effort will help the cause and the rig looks great,its a start as time gos by you can make changes and include more accurate simulations but you have to start some where. I suggest a I beem with two posts to hold bar bell weights side by side of 45 pounds each till you reach desired weights for testing.A papal account is in order,a request to Vans for the donation of gear legs is in order,Fun n Sun is right around the corner and they are our captive audience if 100 customers request their help,it will put this effort on the map.Best of luck and here is my $20 and Thanks.
Bob
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02-24-2011, 05:05 AM
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Join Date: Jan 2005
Location: Louisville, Ga
Posts: 7,840
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This rig has so many options...
...that allow tests to destruction...exactly the physical proof-of-concept beginnings.
Leland Snow at Air Tractor did landing gear drop tests on the new Air Tractor 1002...a thousand gallon airplane (1,000 gallons in the hopper!) and dropped the whole landing gear assembly until the spring gear buckled inward and the wheels leaned in at more than 45 deg at impact. Everything survived and was analized (sp) for structural damage.
Seemingly Rube Goldberg devices are often very valuable!
Best,
__________________
Pierre Smith
RV-10, 510 TT
RV6A (Sojourner) 180 HP, Catto 3 Bl (502Hrs), gone...and already missed
Air Tractor AT 502B PT 6-15 Sold
Air Tractor 402 PT-6-20 Sold
EAA Flight Advisor/CFI/Tech Counselor
Louisville, Ga
It's never skill or craftsmanship that completes airplanes, it's the will to do so,
Patrick Kenny, EAA 275132
Dues gladly paid!
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02-24-2011, 11:11 AM
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Join Date: Mar 2007
Location: 45G, Brighton, MI
Posts: 1,867
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Quote:
Originally Posted by pierre smith
... Everything survived and was analized (sp) for structural damage...
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I think that "analyzed" is the word (a verb) you were looking for Pierre, but you may have just invented an adjective that best describes some of the discussion that goes on here... 
__________________
Miles (VAF# 1238, Paid up as of 2018)
RV-7 TU 904KM (reserved)
Wings Fitted and Finish Kit on site
Construction Log
Picasa: Empennage Album, Wings Album, Fuselage Album
1955 Cessna 170B flying since 1982
'To get something you never had, you have to do something you never did.' -Unk.
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02-24-2011, 11:37 AM
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Join Date: Mar 2006
Location: Tucson, AZ
Posts: 823
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PROGRESS REPORT ON FRONT GEAR TEST
Thanks to (almost) all for your comments. Given that my nose gear folded on a “well maintained” paved runway in San Diego, avoidance of grass fields is not an adequate solution.
PROGRESS REPORT: This week we welded additional steel onto the jig, mounted 5 Chevy cylinder heads adding 210 lbs, and towed it for test #2.
In total, using my wife’s bathroom scale (she was none too happy), the nose gear weight including the front wheel is 252 lbs. However, as one of the engineers in this thread pointed out, the see-saw inertia caused by an airplane as the mains bound over bumps, changes the amplitude of the load on the nose gear. I am not a mechanical engineer so I apologize if my terms are not exactly perfect but we think we need to change the configuration of the jig so that more of the static weight is in front of the attachment point which will (hopefully) induce the see-saw effect and increase the bending of the gear leg. Thus far, all we are observing is the tire with 38lbs of pressure compressing as it hits small bumps. We have not created any simulated bumps yet. Yes, we will vary tire pressure once we accurately simulate the action of an A model.
How can people help? Given that we are type-A old men and there are only 27 hours in every day, here’s what we need. First, we could use some engineering to tell us how to induce the see-saw and side loads. My catastrophe occurred when my front wheel followed an intersecting runway and bent over sideways. If you have the engineering skills we need, send us some design considerations otherwise we will simply waste time and steel with experiments.
Second, if someone wants to set up a PayPal account and collect $$ to be used towards the steel and other equipment we need, please set it up and hang onto the proceeds to be used for that equipment beyond our social security funded budget. We think we need D/A equipment so that we can get precise measurements but haven’t a clue where to get it. If you have other ideas or measurement jigs we can attach, please send photos and/or the actual devices.
Third, remote cameras are not my forte so if you have access to photo equipment we can use to record the effects of engineered designed bumps, please loan it to us. If we destroy it during the tests, we will ask the PayPal teammate to send the $$ and offset your contribution. Right now, a senior citizen is sitting on the trailer taking pictures while it’s towed down the road. Obviously, that’s not a good idea.
Thanks again.
__________________
Barry - Tucson
RV9A Superior O-360 (an amazing experience)
Dynon AP Garmin Sensenich F/P
2020 Dues paid. Thank u DR!
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02-24-2011, 11:39 AM
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Join Date: Nov 2009
Location: Yardley, PA
Posts: 1,334
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Bravo
you guys - this is great. The only thing I would suggest is to formulate as many hypotheses as you can to test. For example, what is the effect of weight?, or what is the effect of pot hole depth on failure. It may sound silly, but in the end you will have a list of specific hypothesis that you tested, and the results. Maybe others here can suggest some. Other than that, duplicating as closely as possible the RV-XA landing gear as possible I think is critical. For example - here's a hypothesis... At or above gross, when the main gear hit a pot hole the increase in downward force on the nose wheel will cause a failure. To test that hypothesis you'll obviously need actual main gear and wheels. Also, I feel that some of the failures are due to the airplane "pole vaulting" over the nose wheel, placing the entire airplane weight on it with additional force (F=M*A, remember) and causing it to fold under. Your rig may not be able to duplicate that scenario.
You get the point... good luck!
Tom
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02-24-2011, 12:15 PM
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Join Date: May 2005
Location: Canby, Oregon
Posts: 1,786
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Another thought has just made it way through....
I know, at my age it can be a shock, but it does happen from time to time.
I also may have missed it in the proceeding messages, but....
With increased speed the weight on the wheel will be lessened (IE we are holding the stick back). How much effect does that have on the nose wheel weight?
Will this be accounted for with math or will your remove some of the weight when you try higher speed runs with the 'rig'?
Kent
__________________
Kent Byerley
RV9A N94KJ - IO320, CS, tipup
AFS 3500, TT AP, FLYING....
Canby, Or
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02-24-2011, 06:53 PM
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Join Date: Aug 2006
Location: Battle Ground, WA
Posts: 426
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Run over a "calibrated bump" ...
Quote:
Originally Posted by MrNomad
Thanks to (almost) all for your comments. Given that my nose gear folded on a ?well maintained? paved runway in San Diego, avoidance of grass fields is not an adequate solution.
PROGRESS REPORT: This week we welded additional steel onto the jig, mounted 5 Chevy cylinder heads adding 210 lbs, and towed it for test #2.
In total, using my wife?s bathroom scale (she was none too happy), the nose gear weight including the front wheel is 252 lbs. However, as one of the engineers in this thread pointed out, the see-saw inertia caused by an airplane as the mains bound over bumps, changes the amplitude of the load on the nose gear. I am not a mechanical engineer so I apologize if my terms are not exactly perfect but we think we need to change the configuration of the jig so that more of the static weight is in front of the attachment point which will (hopefully) induce the see-saw effect and increase the bending of the gear leg. Thus far, all we are observing is the tire with 38lbs of pressure compressing as it hits small bumps. We have not created any simulated bumps yet. Yes, we will vary tire pressure once we accurately simulate the action of an A model.
How can people help? Given that we are type-A old men and there are only 27 hours in every day, here?s what we need. First, we could use some engineering to tell us how to induce the see-saw and side loads. My catastrophe occurred when my front wheel followed an intersecting runway and bent over sideways. If you have the engineering skills we need, send us some design considerations otherwise we will simply waste time and steel with experiments.
Second, if someone wants to set up a PayPal account and collect $$ to be used towards the steel and other equipment we need, please set it up and hang onto the proceeds to be used for that equipment beyond our social security funded budget. We think we need D/A equipment so that we can get precise measurements but haven?t a clue where to get it. If you have other ideas or measurement jigs we can attach, please send photos and/or the actual devices.
Third, remote cameras are not my forte so if you have access to photo equipment we can use to record the effects of engineered designed bumps, please loan it to us. If we destroy it during the tests, we will ask the PayPal teammate to send the $$ and offset your contribution. Right now, a senior citizen is sitting on the trailer taking pictures while it?s towed down the road. Obviously, that?s not a good idea.
Thanks again.
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... at an angle. This is would be very similar to your mishap in San Diego. Please, please avoid designing a test with too many variables (refer to my previous post re simple tests). The calibrated bump can be as simple as a strip of 1/2" plywood secured to the pavement that engages only the nose wheel. By varying weight, tire pressure, approach speed and approach angle w/ multiple runs at each configuration, you are going to have a lot of data to analyze. Once you accomplish all of the above, you can change the height of the bump to 1", etc. etc. That is a lot of testing. If possible, I would consider one camera at a fixed location on the ground ("global reference") and one camera on the trailer ("Local reference")
LarryT
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