Highflight said:I see what you're doing, and I understand the philosophy.
I'd just like to suggest a consideration.
While resins in many respects are quite strong in many applications, impact resistance is not usually one of their strong suits. And we're talking BIG IMPACT here, not just a scuffing.
A properly bracketed, curved piece of steel might be better (if anything) because while steel may bend, it should still work as intended while a piece of catalysed resin will very possibly shatter. Even if the resin didn't shatter, I can imagine it being dislodged by the impact.
(To test my theory, mix up a big ball of material and let it cure. Then set it on the ground and whack it as hard as you can with the heaviest sledge hammer you can find. That will be only a fraction of the impact a nose gear might see if it drops into a hole.)
If that happens, you could then have either one big chunk, or a bunch of loose material (inside the fairing), jamming and deflecting the wheel itself and perhaps causing accelerated damage and subsequent flip where the standard arrangement might have been ok with just fairing damage.
Just thinkin' it through to a logical "conclusion".
This is one where I would definitely ask for Van's blessing before going with a chunk of resin in that area.
vlittle said:No skid plate design can solve the inherent problems with the nose gear design. My 'fix' is simply to provide a theoretical increase in the design margin that was relatively easy to implement.Vern Little
fodrv7 said:If the Nose STRUT bends back it must be because something besides the wheel is in contact with the ground. Whatever it is that is dragging on the ground, smoothing it or strengthening it is not going to reduce the friction and the more it bends the more it is loaded and the more it will continue to bend. We are not talking about snow skiing here.
I have been reading all of the threads that have started due to the most recent nose over. The trailing arm suspension nose wheel has always seemed to be the most logical design for ANY nose wheel airplane. I have never understood how the leading link could be anywhere near as strong.fodrv7 said:Vern, You are quite right. Reducing the friction (Resistance) of any fixed part of the nose wheel is going to improve things.
If however, the resistance is still sufficient- a largish hole for example- to bend the strut back, then as I have pointed out, the load on the Nose Gear and therefore the resistance will only increase.
After all that is the whole point of trailing arm suspension. Deflection decreases the load.
Pete.
I like the name "skid plate" better myself.GrayHawk said:"Friends of mine in Lockhart, TX. built what they call their "jock strap", a rounded steel plate covering the big nut holding the nosewheel fork on. Hopefully it will skid along the ground keeping the nut from digging in and prevent a tip over."
Highflight said:I see what you're doing, and I understand the philosophy.
I'd just like to suggest a consideration.
While resins in many respects are quite strong in many applications, impact resistance is not usually one of their strong suits. And we're talking BIG IMPACT here, not just a scuffing.
A properly bracketed, curved piece of steel might be better (if anything) because while steel may bend, it should still work as intended while a piece of catalysed resin will very possibly shatter. Even if the resin didn't shatter, I can imagine it being dislodged by the impact.
(To test my theory, mix up a big ball of material and let it cure. Then set it on the ground and whack it as hard as you can with the heaviest sledge hammer you can find. That will be only a fraction of the impact a nose gear might see if it drops into a hole.)
If that happens, you could then have either one big chunk, or a bunch of loose material (inside the fairing), jamming and deflecting the wheel itself and perhaps causing accelerated damage and subsequent flip where the standard arrangement might have been ok with just fairing damage.
Just thinkin' it through to a logical "conclusion".
This is one where I would definitely ask for Van's blessing before going with a chunk of resin in that area.
RVbySDI said:Why does Vans look at the leading link design as a good design for his aircraft
My only issue is this. Van has sold TONS of kits and a majority are now (sadly) nose-draggers. Hire on some outside help and fix the darn problem!Captain Avgas said:I suspect the answer to that question lies in the fact that the design of an aircraft requires an in-depth knowledge of a whole lot of different technologies. If the aircraft is designed by one man then it is reasonable to assume that he may have a stronger grip on some required technologies, and a lesser grip on others. That stands to reason.
In other words, aircraft landing gear systems may not be Richard VanG's strong point. That should not be surprising. Aircraft landing gear systems is a science in itself. The larger aircraft corporations probably subcontract out their design requirements to specialist mechanical engineering consultants (or have dedicated specialist in-house engineers).
On the RV12 nose gear Van initially attempted something different. It looked like an oleo strut but in fact it was nothing of the sort. It incorporated a spring and some people who saw it up close at Airventure 2006 described it as amateurish. In the end I believe Vans agreed because he seems to have dumped the new design and gone back to his stock configuration.
Van's nose gear design on the current 2 seat fleet is an over simplification of a complex structural requirement. Does that tend to indicate that the design has stretched Van's expertise in the area. Very possibly.
It may also explain why quantifiable improvement to the system are not forthcoming.
osxuser said:My only issue is this. Van has sold TONS of kits and a majority are now (sadly) nose-draggers. Hire on some outside help and fix the darn problem!
osxuser said:My only issue is this. Van has sold TONS of kits and a majority are now (sadly) nose-draggers......
It's not, because people buy RV-A's because they are fixed gear, nose draggers. They want the simplicity of FG and the familer wheel in the front. And with startling commonality, a percentage of them are getting bitten in the behind by a corner of the operational envelope that shouldn't be a problem at all.L.Adamson said:I wonder if this problem, is with any more frequency than mechanical failures of retractable landing gear.
It doesn't appear so; and believe this whole issue is getting rediculously overblown!
L.Adamson
osxuser said:If any certfied company made the -A models there would be an AD by now, but these are kits, so no AD. I am left to wonder, as word gets out about this little problem, if people won't start either building TW's or maybe just building something else?
Given the frequency we see these landing accidents, and my desire to land on grass, you couldn't pay me to put a nosewheel on my -7 build...
I talked via phone with the people at Lockhart who made the "jock strap"; but he actually called it the "knee cap" this time.the_other_dougreeves said:I like the name "skid plate" better myself.
Seriously, this sounds like just the thing.
Yes, it is the PlaneTalk hangar group. I'll post the photos when I get them, or if I'm down in Texas, may stop over at Lockhart.LifeofReiley said:Hi Bill,
I would like to see these pics too. (Planetalk?)
osxuser said:If any certfied company made the -A models there would be an AD by now, but these are kits, so no AD. I am left to wonder, as word gets out about this little problem, if people won't start either building TW's or maybe just building something else?
Given the frequency we see these landing accidents, and my desire to land on grass, you couldn't pay me to put a nosewheel on my -7 build...
osxuser said:Given the frequency we see these landing accidents, and my desire to land on grass, you couldn't pay me to put a nosewheel on my -7 build...
osxuser said:But this last video and pictures of the -7a accident prove that the guy did have the stick all the way back, and was doing everything right as far as we can tell.
osxuser said:The good looks and personal challege are bonuses if you want to look at it that way.
BrickPilot said:What about a beefier version of this trailing link design.... Sure, it's for an ultralight, but perhaps it could be adapted.
I would like to comment on this idea.rzbill said:There is another issue (other than leading/trailing link) that will make integration of your suggestion a challenge. The vertical pivot axis for a castering wheel needs to be well in front of the wheel contact patch. This restriction may result is much of the suggested trailing link mechanism residing in the same general area as the problematic caster nut.
The pictures posted appear to have some potential for application with castering RV gear. The Challenger gear is simply "stabbed" onto a straight tube running down from the fuselage. It is simply bolted onto that gear leg. The current RV gear leg has a curve pointing down at the end of the leg that would be very similar in design. The attach point for the pictured design would not be very far off. It would be high up from the ground and have much more bulk that would require some new fairing needs but I can see it still functioning in a leading link/trailing wheel arrangement.The pictures from your link appear to be from a steerable nosewheel arrangement. Of course.. If we went to a steerable system on the RV, the caster axis goes away completely..
No volunteers or plans to test. They are also hoping for no 'accidental' tests.dan said:Has anybody volunteered to test it out?
I like it! I was thinking of something a little larger and with a different curve, but this is exactly the concept.GrayHawk said:I got permission from the fine people at the "Plane Talk" hangar at Lockhart, TX, to post these photos of their steel "knee cap" design.
Don't blame him/her if they let up on the stick when it dug in, but is that to speed? It does look like they where going fast. The video last about 4 seconds before it digs in. My wild guess is 13-20 mph. Not really that fast, but my margin of error is +/- 100%osxuser said:http://www.youtube.com/v/NfaCGc16jQ0
There seems to be no poor piloting technique here, although it looks like the elevators might not have been full up until AFTER the nose-wheel started to dig. Hard to tell. Look at the background at some of the other aircraft that made it into that field with no problem. Bad luck? Maybe. I tried to embed the video, but I guess HTML is off.
I still draw the conclusion that these airplanes should be able to land anywhere a Grumman Tiger can. Just my opinion, and that doesn't seem to be the case.
Cannot speak for the Lockhart group; I am only posting the photos.vlittle said:I think the knee cap is a great idea. A couple of questions: Can it be made of aluminum instead of steel (weight), and what did you do with the zerk fitting for greasing the pivot?
One observation. My fiberglass design minimizes the collapse of the nose cone by transferring the load to the fork. With the knee cap, nose cone collapse is still possible. We don't want the nose cone jamming the tire.
Perhaps a combination of techniques would be usefull: the knee cap plus some fiberglass packing in the nose cone to give a tight fit.
If you know some handy mechanical types, it's possible to do a test when the gear is off the plane. You'd need a fixture to be able to provide force downward on the gear leg, and force backwards on the wheel axle (representing friction and pitching moment of the airplane during braking).
Finally, I think it's possible that a modified form of knee cap would work even better on the new fork design.
Great work, keep it up!
Vern
RVbySDI said:BrickPilot said:What about a beefier version of this trailing link design.... Sure, it's for an ultralight, but perhaps it could be adapted.
The pictures posted appear to have some potential for application with castering RV gear. The Challenger gear is simply "stabbed" onto a straight tube running down from the fuselage. It is simply bolted onto that gear leg. The current RV gear leg has a curve pointing down at the end of the leg that would be very similar in design. The attach point for the pictured design would not be very far off. It would be high up from the ground and have much more bulk that would require some new fairing needs but I can see it still functioning in a leading link/trailing wheel arrangement.
OK, I got another email from Lockhart & I have been giving this skid plate design the wrong name. It is not 'knee cap" and I quote:GrayHawk said:Cannot speak for the Lockhart group; I am only posting the photos.
But my guess is yes, it could be made of aluminum. The grease zerk hole is used for one of the 3 mounting holes.
Maybe someone from Lockhart will join in.