What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Nose gear Theory..

AlexPeterson

AlexPeterson

Well Known Member
As I've written in previous posts, I have concerns with the current nose wheel bearing/axle setup. My understanding of the current nose wheel setup is that there are two axle adapters, which are against the roller bearings. The bearing preload is determined by how tight the bolt is/isn't.

It would seem that this system is not overly rigid. Under loads, the bolt will attempt to flex somewhat. When this flexing occurs, there is an increase in the bearing load on the load side, and an unloading on the opposite side. The deflections could be very, very small, yet still have a large effect.

Is it possible that runaway bearing drag is contributing to the nose-over incidents? It is not hard to imagine that there is a whole range of states of bearing pre-load out there, from sloppy to tight.

There are two things which could contribute positive feedback (forces which feed on themselves) in this system. One is that as the nose wheel hits a bump, the axle bolt flexes, increasing the rolling drag of the bearings. This in turn pushes the nose gear aft, which tends to increase the load even more and so forth and so on (the pole vault). Of course, once into pole vault mode, it is up and over.

I will work on some range finding force estimates over the next days.

BTW, my nose wheel bearing setup seems to be an anomaly, received in about 1997 or so. Here is a picture of the basic components:

66AP%20front%20wheel%20bearing.jpg


Sorry about the crummy cell phone picture, but you can see that there is a large, about 1" diameter, hollow bar which goes all the way through. The bearing retainers are simply hollow cylinders. The lengths of the various parts needs to be correct for bearing preload, or shims need be used to set the preload. The important feature is that the bolt is torqued to nominal values, and the stack becomes very rigid compared to just a bolt. Does anyone else have this setup? It is simply what came from Van's with my kit.

I would welcome others' thoughts about this possible explanation for nose gear problems. Like many others, I was very, very humbled by that video of the 7A in England.

Something just does not make sense, perhaps this could explain it?

As an aside, I do not believe that a wheel fairing would have had any effect on the outcome, as once things have deflected enough for the nut to drag, it would seem to be all over.

Due to the serious nature of this, it would be very helpful to this thread if we could keep it on the engineering topic discussed above - thanks.
 
Last edited:
The nose wheel set up that came with my RV-6A quickbuilt in 1998 was as you orginally described with the axial bolt torgue setting the bearing pre-load. After 5-10 hours of flight I noticed that the bearing adapter/spacers (do not have my drawing here to have the part number) provided where rotating in the fork. I decided to modify the set-up to include a clamp up bushing I made so the bearing pre-load is set by the bushing length and the axial bolt can be torqued so nothing spins but the bearing in the bearing race. Took one or two tries to make the bushing the correct length but started long and trimmed until the bearing pre-load was what I wanted. This is how all bearing joints should be designed to use clamp-up to ensure the roatation is on the bearing.

I agree with you that there is still a lot unknow about why the flip over happened in England (along with others). I agree that the bearing load could contribute as it can create a drag force. I am also not convinced that the nose gear fearing has much effect (but that is another thread).
 
Philip,

Thanks for the reminder about the axle adapters rotating - that might be a very important piece of the puzzle. I recall another lengthy thread about that issue, but I don't think it was implicated as a possible cause of front wheel lockup.
 
Tightening the axle nut to the correct torque on the current style nose wheel bearing system to obtain the correct bearing preload seems to be a rather imprecise method to me. The legs on my nose fork (new style) had to be forcibly sprung open somewhat to allow the wheel assembly to slide into position. Due to the spring-back, clamping action of the fork, there was considerable rotational resistance on the wheel without the nut even installed. Tightening the nut up to the specified torque increased the rotational drag even more. Maybe this is how it was designed so that the wheel assembly becomes a more snug fit between the fork legs once the bearings bed in. What have others experienced here? Do the legs of the fork have to be forced apart to allow the wheel assembly to slide into place? :confused:

Fin 9A
 
Finley Atherton said:
Do the legs of the fork have to be forced apart to allow the wheel assembly to slide into place? :confused:
Fin 9A
Click to expand...


Mine had extra clearance (maybe 0.06") and therefore the axial had to be tightened just to spring them together. The fork is a weldment and therefore will never be very percise (that whole heat thing). That is why I made a clamp-up bushing to pull together the forks, torque the nut, and still not over load the bearings.
 
My Summary

Here is my nose gear summary list:

PREVENTATIVE:
1. Immediately upgrade to the new nose wheel fork (I already have it)
2. Pull Out set to 25#
3. Nose tire pressure at 35psi (set for pavement)
4. Stake 'biscuits' to nose wheel fork (ala Roberta & others)
5. Take off & land from smooth paved surfaces (my personal choice for now, as a low hours RV-A pilot)
6. Treat every takeoff & landing as soft field (nose on runway ONLY if there is not enough elevator authority & unless there is a good reason for otherwise)
7. Correctly preload the nose wheel bearings
8. Land as slow as I can without stalling
9. Minimize use of brakes
10. Any screw up like appreciable bounce on main gear is a GO AROUND
11. Make sure wheel pant is solidly mounted with thumb+ clearance all the wall around (fiberglass to tire)

CORRECTIVE:
1. Consider either a Vern Little or Jock Strap skid design. Right now the Vern Little looks easier to implement and may have the advantage of holding the nose cone together better. Possibly also do the modified clearance wheel pants at the same time.

PERSONAL:
If, after doing all of the above to the best of my ability, bad luck still hits; that's all it is, bad luck & an accident. It's no one elses fault & for that matter, not really my fault.
 
Last edited:
GrayHawk said:
8. Land as slow as I can
Click to expand...

Last Thanksgiving I landed too slow at an airport I was unfamiliar with. My -9A stalled a foot or so above the runway, hit hard on the mains, and then immediately banged the nosewheel so that it "twanged". My best landings are done coming over the fence at 60 knots and rounding out until the mains kiss the runway, holding the nose off until elevator authority is nearly gone, and then lowering it. Full stall landings are not the way to go here.
Leland
 
Last edited by a moderator:
Leland said:
GrayHawk said:
8. Land as slow as I can
QUOTE]

Last Thanksgiving I landed too slow at an airport I was unfamiliar with. My -9A stalled a foot or so above the runway, hit hard on the mains, and then immediately banged the nosewheel so that it "twanged". My best landings are done coming over the fence at 60 knots and rounding out until the mains kiss the runway, holding the nose off until elevator authority is nearly gone, and then lowering it. Full stall landings are not the way to go here.
Leland
Click to expand...
Agreed! I took no stalling as a given, but will modify the list. I usually am at 80 mph over the fence, 70 mph over the numbers, which is about the same as your 60 knots. (5040' elevation airport) Also good point on gently lowering nose before elevator authority is gone.
Click to expand...
 
Last edited:
Previous damage and fatigue

Here's another angle, illustrated by the fellow who stalled his airplane a foot off the ground.........Have the accident airplanes sustained unrecognized
damage in landing incidents previous to the nose gear collapse that has weakened them? Does nosewheel shimmy fatigue the nosewheel strut?
 
Same config

My nosewheel setup is the same as Alex's, solid bar through. It is a bit more difficult to set bearing play as it requires washer shims. The thicker the shim, the looser the bearings. It seems like a good system, however. Mine were originally on a 6A built in about '94 and i got it with a FWF package when the plane was destroyed by hurricane Charlie. Anyone know why this design ws dropped?

After over 100 landings, trying many different approaches, I believe the soft field approach is the way to go also. Full stall works well IF it is done perfectly. My flying isn't perfect, although I won't tell my wife that. The nose is easy to keep off the ground, even with some initial braking. On touchdown, I hit the flap switch (up) as I seem to be able to hold the nose off longer that way. With a FP, I am usually at idle on short final. A touch of power doesn't hurt, but that of course depends on the field/conditions. Haven't tried grass yet and think I'll wait until I have the new fork.

Bob Kelly
 
Why not go with a setup like certified airplanes have? Have a solid tube that the bearings fit over, then make a nosewheel fork that the tube fits through, and just torque the whole thing down with spacers... hmm, doens't sound as clear without a picture...
 
Powerful evidence:

Pete Howell sent me this link:

http://kitplanesmag.blogspot.com/2008/05/amys-rv-10-high-flight.html

This is powerful, even conclusive, evidence in support of the theory I put forward at the beginning of this thread. Specifically, that some sort of deflection in the fork/axle assembly is causing bearing drag to increase with a positive feedback cycle. It appears that the -10 can tolerate a locked nose wheel, thankfully for this -10.

Note that the nose wheel was heard to lock during takeoff also.

Smooth runway, can't blame that.

It is not clear to me if the -10 has gone through more than one nose wheel axle/bearing support design or not.

It would be very helpful if someone could post pictures of the components of a -10's axle setup.

I will try to find more details on this specific -10's axle arrangement.

My judgment is that this is a primary cause of many of the flip over accidents.
 
Any design where the outer spacers exert force on the bearings through the rubber seals is imprecise at best for establishing consistent preload.

The original RV10 parts used thin wall stainless tubing instead of aluminum outer spacers. This was a really bad design as there was a tiny contact area against the curved portion of the inner race. The tubing wore down a bit and started spinning against the fork, cutting into it. This ruined the fork and led to very loose assemblies with no preload. The good part was that the spacers did not press against the rubber seals.

Van's then went back to thick walled aluminum outer spacers which pressed against the rubber seals again. Arrgggh. Wheel bearing design is not one of their strong points.

There is plenty of discussion here: http://www.vansairforce.com/community/showthread.php?t=20851&highlight=rv10+front+wheel
 
Does this look right?

This is the picture from the Kitplanes blog the Alex linked to above...

DSC_0635.JPG


Something seems funny with the gear leg at the lower bend.... or am I just seeing things?....:)

Is it a welded repair?....:eek:

gil A
 
HERE IS A PICTURE.....

osxuser said:
Why not go with a setup like certified airplanes have? Have a solid tube that the bearings fit over, then make a nosewheel fork that the tube fits through, and just torque the whole thing down with spacers... hmm, doens't sound as clear without a picture...
Click to expand...
This is a picture from the service manual of my 76 piper.....
hpim1520tt9.jpg

The felt dust seal rides on the outside of the spacer.
hpim1520tt9.jpg

To install this, you place #25 spacers into the bearing dust seals and slide the wheel and spacers in between the fork. Then slide in the AXLE #26. It passes through the fork hole. Then install #28 the plugs and the rod #27. As you can see, there is NO LOAD ON THE BOLT (ROD) #27. And these nose wheels take a beating as Pipers only trainer...
 
Last edited:
Leland said:
Last Thanksgiving I landed too slow at an airport I was unfamiliar with. My -9A stalled a foot or so above the runway, hit hard on the mains, and then immediately banged the nosewheel so that it "twanged". My best landings are done coming over the fence at 60 knots and rounding out until the mains kiss the runway, holding the nose off until elevator authority is nearly gone, and then lowering it. Full stall landings are not the way to go here.
Leland
Click to expand...

Yup you are so right. I see all the time, RV's landing flat with a nose wheel, that is a definate no no. Heck I remember back when I was learning to fly, I thought I did a good landing, than the instructor said, " that was awful". I said what? he said you landed on the nose wheel. Oh, I said, your not suppose to do that, he said no way, try again. I made him happy by doing touch and goes without touching the nose wheel on the runway. It was actually fun and I felt it was a test of my ability to land correctly.
 
I think the best set up is what I'm using, the Grove front wheel, they use a spacer in between the bearings to set preload, then they stake the spacers so they don't move. Also uses a light weight wheel. I'm going to take all my wheels to a motorcycle shop and have them balanced as well. Main thing, no front wheel landings. If it doesn't go right, do a go around. And if you want to dispense of embarrasment, than call for an option, than if you do a good one, just say your full stop. At least that's what many of the pilots at my field do.
 
Group effort for a new Nose gear design and Nose gear theory

If anyone is familiar with the story of the Zenith 601XL, it had problems where the wings would fold in the middle of flight, killing all on board. Owners expressed concern on message boards for years and Zenith denied there was any kind of problem, they insisted it was pilot error. Even after the FAA basically grounded the entire fleet of 601XLs, the company still maintained that there is no problem, however they did come out with an ?upgrade kit? available as a retrofit to fix the non-problem.

Before the NTSB and FAA got involved, the owner and builder community began to do a grass roots fundraising effort to raise money for an independent engineer to do an analysis of the structure to find where the problem may be.

Would the owners or prospective owners of the ?A? models possibly be willing to put money into an escrow, or as a deposit (maybe a couple hundred dollars?) to an engineering company to design a new nose gear? It may be a risky thing to do and there may not be a solution found, but if as a group a trustworthy company is hired, we may get something. With all the work and analysis already completed, this company should have quite the head start.

I?m not trying to start a war here, and I have nothing but respect and admiration for the Van?s company and staff. Additionally, I have no idea who to hire, nor would I want to be the one to collect the funds, so I have nothing monetarily to gain by suggesting this. However I would like to see a more robust gear available to help create a safer airplane for pilots of all levels. If it saves just one life, wouldn?t it be worth it?
 
Hmmmm I guess I would agree with what you are saying. I just wish Van's would come forward and at least talk about it. What if anything are they thinking?

Those of us building A models are perceiving a problem. Where there is perception, there is usually some truth! For example, when Cessna came out with the 177 Cardinal, it was perceived to be dangerous. Sales evaporated overnight! Even after they fixed the "problem", sales never recovered. Van's needs to grab the bull by the horns and ........

Just my humble opinion, not even worth .02!
 
I'm in too, but....

before proceeding this way, what about sending to Van's a letter signed by all those -A model builders worried for the nose gear issue asking for an improvement on the nose gear? Or maybe, every single builder may send it's own message to Van's... I think if they receive 100...500...1000 or more requests they may consider to modify it (or offer a different nose gear as option) even if they think the nose gear is ok as is.

I can accept to pay a little more on the kit for more safety.

...just an idea...
 
Has anyone seriously contacted Van's?

I think it would be more productive to have a serious approach to Van's and their engineering department, specifically to their chief engineer Ken Krueger. Why don't you document all of the nose gear accidents to -A models, include the engineering analysis that Raiz is working on, summarize all of the suggestions that have been made in these forums (larger tires, better axle spacers, more wheel pant clearance), and formally ask this information to be reviewed and to give an official response.

As you know, the nose gear rod has already been redesigned once as a result of early problems. A torture test rig was built and an actual aircraft was instrumented to calibrate the torture test rig. Drop tests of the landing gear have also been made. Van himself wrote an article some years ago in the RVator soliciting field experience on the nose gear.

An independent engineer would not have the advantage of all this background data.
 
New Nose Gear Design

Count me OUT! A study was already made of the early accidents and it lead to a liability SB to satisfy a "no-size known" group of complaintants. The study listed all the early accidents and the overwhelming majority pointed at excess speed, porpoising on landing, loss of control after touchdown, and even excess speed while trying to taxi to parking.

Let's face it guys. An A model RV is NOT your daddy's Cessna. It WILL NOT take the abuse that a 150, 152, or 172 will take and you better fly it with respect or it WILL bite you.
 
Last edited:
I'm in too, but...

Let's approach this as a design improvement... in other words let's not say the original design is "defective"... let's just say that we want to make it better. And of course any design improvment we come up with may result in additional size, weight, cost, complexity, etc.

As service history builds on the nosegear RVs, it appears that there is evidence that the ability of the nose gear to handle rough terrain, etc. could be improved. This will make a great series of aircraft even beter.

It is a subtle difference in wording, but I suggest that if we approach the task this way, we may get more support from Vans.
 
Not a "problem"

Contacting Van's isn't likely to do any good. Questioning or critizing their designs in these forums isn't going to do much good either, and generates a lot of ill will, some of it fervent.

This does not have to be perceived as a "problem" or "defect". Every engineered component is a compromise to satisfy competing requirements as best as possible.

It appears the current nosegear design places the emphasis on light weight and simplicity, at the expense of margin for rough treatment.

Other designs, in particular certified designs using an oleo strut, provide more margin for rough treatment, at the expense of weight and complexity. I personally don't agree with the existing compromise and am building a taildragger to avoid the issue.

If there are those that would prefer a more robust nosegear, that can happen, perhaps as a collaborative effort, without having to have a "judgment" about the original design.

I would possibly be in, but I wouldn't contribute to any effort unless it were to include a steerable nosewheel. If you're going to have the weight and drag penalty of a nosewheel, you should have the full benefit it is supposed to provide.
 
Last edited:
Like Mike said..

mrreddick said:
Count me OUT! A study was already made of the early accidents and it lead to a liability SB to satisfy a "no-size known" group of complaintants. The study listed all the early accidents and the overwhelming majority pointed at excess speed, porpoising on landing, loss of control after touchdown, and even excess speed while trying to taxi to parking.

Let's face it guys. An A model RV is NOT your daddy's Cessna. It WILL NOT take the abuse that a 150, 152, or 172 will take and you better fly it with respect or it WILL bite you.
Click to expand...

Accidents do happen, but I think that most of the problem that have been experienced are do to not understanding how to land the plane.

I would suggest that the money could be better spent with a good flight instructor.

Not trying to be negative about this effort, but if you redesign the aircraft to be tolerant of poor landing skills, it won't fly the same.
I do enjoy the way my 9A flies.:)

Kent
 
I am ok with those semantics:

“We are not looking to replace a defective nosewheel design, or replace it for everyone, we are looking to provide a more robust option for less than ideal terrain for those that may wish to have it.”
 
Last edited:
I'm in

I will vote with my money if Vans will not take this on. I would prefer however that Vans take on the job and suspect that they may already be doing this. To be realistic how could Van's acknowledge a problem without risking liability? I would not expect them to do so. They may however come out with a new design as has been my past experience.

When I asked about the new gear leg on my 7-A, and if I could replace it with the new one with better ground clearance, I was told by Vans that this was not really a problem. The profile of the wheel and wheel pant remained the same. The new designed fork was only a weight saving improvement thing. Later they came out with the suggested fix.

The wheel pant profile argument is that the wheel pant has to be destroyed before the nut can dig into the ground and be a factor. But this is exactly what was, and still is happening, even with the new fork. To me it appears that the nose wheel is already starting to tuck under to allow the wheel pant to be destroyed and for the nut to start digging in. The gear at that point has flexed too far already. If you do not think this is a problem that is your prerogative. Have you not watched the post-game films? I think that the evidence is that the pole vault pilots were and are good pilots. It is not the case of botched landings or needing more training. I feel that I am susceptible to joining those of the pole vaulting club with the existing gear leg.

New builders deserve better. I do not consider myself a timid person, but like some others here, I will not land on grass in my RV-7A. I fly my Citabria in the mountains and land the back strips, but can not bring myself to land on a grass strip with the 7A without having walked it first. The trust is not there. I think I am being a smart pilot to follow my instincts. They have served me pretty well so far. Keep off the grass.

Count me in for support for a better design. I think we need it. Meanwhile expect me to only land on paved runways, or look for me to be converting to tail wheel after I get inverted oil installed, and a smoke system put in. I am catching up on my projects again.
 
Same here, I'll vote with my checkbook. I'm not looking for a "fix", I'm looking for an "unimproved runway nosegear option".
 
I dont really have a horse in this race as I'm building a -7. But as an Engineer, I think Van's designed the nose gear for the mission of the aircraft. (Keep in mind, I have not done any Engineering analysis of the design and my opinions are based on just visual inspection of the design) Its a cost effective, lightweight sport aircraft and is not specifically designed for operating out of rough strips. If I'm the design Engineer and I have that mission criteria I probably would have come up with something very similar to what Van's did. From the reports I have read, I dont think it is a problem for the mission it is intended for. No disrespect to those that do, thats just my .02

Keep in mind, with any design, there are trade-offs. You can beef up the nose gear--maybe with more expensive/exotic materials and/or adding weight. Whats the trade-off? Its more expensive and/or weighs more.

That leads to reduced performance and less useful load. Although I dont design aircraft I know that with aircraft design, the trade-offs are extremely important to accomplish the mission goals. Will you as the owner accept less useful load (less baggage? less fuel?) or a more expensive airframe for a stronger nose gear? Maybe this would be ok for some but certainly not for others. You cant make everyone happy, this aircraft may not be perfect but it fills most 'wants and desires' of its owners.

With all that being said, I havent seen a 'perfect' design yet...I always like to think there are ways to improve with enough imagination. Could someone come up with a stronger nose gear design without adding weight, complexity or cost? Maybe?...maybe not? Its not easy. Just understand what you're up against if you hire someone. An independent Engineer may come to the conclusion that he cant do it any better...thats a real possibility.
 
Last edited:
Perhaps another possible solution to this problem rather than a stronger gear would be one that fails in a safer mode. If when the nose gear collapses rather than acting as a spring board flipping the airplane over on its back, it would simply break off, that would be a much safer scenario. The plane in many instances would simply end up embarrassingly on its mains with its nose in the dirt, a bent prop and probably a damaged engine but at least the airplane would not be a total loss and the occupants would not be trapped in the wreckage, possibly requiring medical attention or worse.
 
Last edited:
RV7Ron said:
Its a cost effective, lightweight sport aircraft and is not specifically designed for operating out of rough strips.
Click to expand...
I would agree with this except Van designed it and demonstrated it many times on his home field, which I understand is a short, grass strip. It's even been said that the -A models are better short field performers because they can rotate to a higher AOA on landing without smacking the tail... Although I don't know if that was a Van's position or just some other person's opinion.
 
I have been keeping close attention to these threads, and was pretty interested.

Where I am building my -12, there is a -6A next door that i take a look pretty often. One of the things I noticed is that the RV-12 has a much more 'robust' nose gear/wheel.

Perhaps the -12 gear could be looked into as a low-cost alternative, or at least a situation where the engineering has already been done, and can be used to modify the A models?
 
I've heard that some people have solved the problem by taking the nose wheel and putting it on the tail of the airplane. Could you imagine? That's just CRAZINESS!!!

I'm so sorry! I just couldn't resist! It's my duty as a tailwheel driver... Can someone please forgive me?

- Peter
 
Snowflake said:
I would agree with this except Van designed it and demonstrated it many times on his home field, which I understand is a short, grass strip. It's even been said that the -A models are better short field performers because they can rotate to a higher AOA on landing without smacking the tail... Although I don't know if that was a Van's position or just some other person's opinion.
Click to expand...

I agree also... 10's of 1000's of landings with "A" models have been performed on grass strips, it happens everyday. And, no the "A" model RV's is not for just any flyer/pilot. And, yes if you make the decision to land on a very rough un-maintained grass strip well YOU made that decision. The gear as designed works and functions well. Can it be heavier and made super beefy? Well yes. Not for me.

I will also hint this... Jack your "A" model plane up and totally level the plane... all axis perfect level flight about 2 inches off the floor. Then with the nose fairing off the plane, take a digital level and check your nose wheel and fork dead straight and centered on both sides. I'm interested in hearing some results. Mine is fixed now. There may be an issue, but I not blaming it on the nose gear leg.
 
What Would I Do If I Were Van?

First, I'm not a mechanical or aeronautical engineer (lapsed metallurgist), and I'm only a part-time flight instructor, but if I were Van, these forums would cause me to take a different tack, especially when I've read posts asking:
Why am I having problems landing (I'm using 80-85 kts over the fence)?
Why am I having problems transitioning on a low ILS approach (I'm not quite stabilized at 120 kts inbound)?
What should my tire pressure be?
What's the problem with 1/4 inch clearance around my gear fairings?
What does soft field technique really mean?
Why am I replacing brake pads every "x" hours?
Soooo, if I were Van, I'd
1. Press the FAA to issue LODAs to about 50 instructors who would first be required pass a factory course and adhere to a factory syllabus.
2. Work with the FAA to restrict airworthiness certs to only those who have taken AND passed a factory transition course
3. Require recurrent training or at least the BFR be done by a factory cert instructor.
4. At a minimum, require purchasers of my aircraft to be able to hold +/- 2 knots all the way down final and be able to land within +/- 200 feet of a target-or go around. It really isn't that hard.
Would this eliminate all incidents? Nope. And this type of approach is a little extreme. Kind of like Cessna took after first selling Citations to pretty much any pilot with a checkbook.
Finally, I'll end with a couple of questions: How bad of technique should design allow for - Cessna 150? How bad a field should design allow for - Piper Cub?
Terry, CFI
RV-9A N323TP
 
terrykohler said:
restrict airworthiness certs to only those who have taken AND passed a factory transition course
Click to expand...



These two are completely unrelated to each other...how can you even relate them to each other via the FAA? What if the builder isn't the flyer? What about resale...revoke the airworthiness?

Also, what are the checkride standards for an ATP? I believe your +/-2 knots exceeds those standards.

Essentially, what you are suggesting is a type rating for a Van's RV. Let's not get carried away here.

Joe
 
N200PF said:
I've heard that some people have solved the problem by taking the nose wheel and putting it on the tail of the airplane. Could you imagine? That's just CRAZINESS!!!

I'm so sorry! I just couldn't resist! It's my duty as a tailwheel driver... Can someone please forgive me?

- Peter
Click to expand...



Peter--

We've got fellow RV pilots with some serious concerns here. While I appreciate the attempted humor, can we skip it just this one time, please?


Thanks,
Joe
 
NLG Working Group

Those interested in participating in a NLG working group to explore the -A failure modes and potentially come up with an engineering fix, please contact me. We need financial supporters as well as technicians and engineers.

Doug Kronemeyer
916.967.1639
 
NLG

ferret said:
Those interested in participating in a NLG working group to explore the -A failure modes and potentially come up with an engineering fix, please contact me. We need financial supporters as well as technicians and engineers.
Click to expand...

By NLG I hope you do not mean the National Lawyers Guild. All kidding aside, maybe you can set up a website or blog to show more about what you are working on and what you propose to do. Might make it easier for people to finanacially support the effort as well.

and remember, were not exploring the -A "failures" were simply looking for a tougher gear option for those that want more strength in the nosegear area.
 
Engineering Approach to NLG Issue

Great discussion going on here. All concerns and comments are note-worthy. Many I suggest a 6-Sigma engineering approach employed where I work to develop a ROBUST (already used by a member in here) design improvement. 6-Sigma DMAIC Robust design is data-driven and consists of:

1.) Defining the issue and developing critical customer requirements (performance, weight, cost, reliability, durability, etc)
2.) Measuring the available data (field population, accident rate, pilot experience, current design)
3.) Analysis of data and development of concepts
4.) Improvement on the original design based on the data (Development of the most promising design based on a Pugh analysis)
5.) Control phase of a sample population. (Piloting the new design)

It will take a team of many individuals to work this methodology, may prevent a confrontational approach, and might make Van's a willing team player.

Paul
LAF
N277PM
RV7A Fuselage
Just got an IO-360
 
Last edited:
WAM120RV This is constructive stuff.

WAM120RV - Obviously you have given this some thought.

I am sure we can find a NLG to put this on. I also would like to see a larger picture. I blew it up and think I may have the concept.

1. Are you going to just cut the leg off and put a pipe splice on it or what is the intent for attachment?
2. Is the bend in the gear leg where you think the problem originates? I sort of think so from looking at wreck pictures.
3. Is the splice going to run up some distance to stiffen and reinforce the lower part of the NGL?
4. Do I see the nut on top to keep the nut out of the dirt? I do not think that is the real problem, but you may be correct there also. Is the piece on the bottom just to rest the wheel on for a photo?
5. Is the part machined out of aluminum? I would worry about that. I have a lot of concerns and would like to see the calculations and drawings you have engineered up. For now a general explanation of your observations and thinking would be helpful to me.
 
TOAD said:
WAM120RV - Obviously you have given this some thought.

I am sure we can find a NLG to put this on. I also would like to see a larger picture. I blew it up and think I may have the concept.

1. Are you going to just cut the leg off and put a pipe splice on it or what is the intent for attachment?
2. Is the bend in the gear leg where you think the problem originates? I sort of think so from looking at wreck pictures.
3. Is the splice going to run up some distance to stiffen and reinforce the lower part of the NGL?
4. Do I see the nut on top to keep the nut out of the dirt? I do not think that is the real problem, but you may be correct there also. Is the piece on the bottom just to rest the wheel on for a photo?
5. Is the part machined out of aluminum? I would worry about that. I have a lot of concerns and would like to see the calculations and drawings you have engineered up. For now a general explanation of your observations and thinking would be helpful to me.
Click to expand...

Good design!
It looks as though it can be retrofit to any of the existin fleet and should pose very little weight penalty.
In looking at my gear leg, it doesn't appear to be straight and squar with the rest of the engine mount. I thought it may have been an optical illusion but when LifeofReilly "hinted" that it could be an issue and sure enough, it's not right. WAM120RV's design could be a "cure".
Many cite Cessna as having "bullet proof" gears but something you need to keep in mind is that on many of thier aircraft, most notably the 182, they offered a heavy duty gear option. If Cessna offered that on what was already considered a good design, why can't the same thing be had for an RV?
Count me in on this project.
 
A slightly different thought

I remember one case in particular where a pilot (one of the members of this group) landed and as crossing the intersecting runway, had the gear twist fold under and flip the plane. This happened on paved runway at a towered airport. This was not a case of landing too fast or dropping in a chuck hole. Having thought about this as I build my very very slow build -6A I have thought about this a while. In the old days, when I used to work on cars and trucks, they had helper springs. Many trucks still have leaf springs with progressive stiffness (K factor). I have wondered if a similar approach could be used on the nose gear. I have wondered if we could mount a single leaf spring over the top of the area that flexes when the nose gear starts to fold and clamped above and below that point. In normal situations the leaf would have no effect but when the leg starts to bend into the switch blade position, a hard rubber block would start to be compressed between the gear leg and the much higher stiffness leaf spring. This might be enough to keep the leg from folding farther but would probably sacrifice the vertical part at the fork. The loading on the mount would have to be analyzed in this case. Just a thought and perhaps my mechanical engineering colleagues with FEA could model something like this. Just the idle thoughts of an E.E. I would be interested in supporting a redesign.

Paul
N694BP reserved
 
You must log in or register to reply here.
Back
Top