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RV-9A front gear folds

wingtime said:
...Now I'm learning of a gear failure on a paved runway? Say WHAT? An airplane LANDING gear should be able to handle a friggin bump on an open runway. Short of the "lip" being the size of a curb or a pothole as big as a bucket a proper gear should handle the occasional bump!...
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Don Jones said:
John, while I agree some have been pilot induced, an airplane at taxi speed should be able to take a lot more abuse than has been demonstrated by the nose gear failure being discussed here. Like has already been noted, there has to be some safety margin in the thing, after all NO pilot is perfect 100% of the time and the airplane should be able to stand the less than perfect technique or the un-seen pothole in the grass runway.
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N941WR said:
If a rabbit can flip an RV-A upside down, there has to be something wrong!...
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I agreed with all of the above posts and while I had to shake my head at some of the responses, because I don’t have a dog in this fight, I wasn’t going to comment. But after reading L.Adamson’s post, I have to respond as you seem to be comparing apples and oranges;

L.Adamson said:
...However, as I've mentioned previously, I do know of three taildraggers.................locally, that flipped!...
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I’ve yet to read about any RV-4 gear failures, or have I missed all those threads? Any plane, certified or not, can and do flip, but how many of these are the direct result of a gear failure? Not many I would think, or do you really believe each and every flip has been caused by poor piloting? I don’t doubt that some have, but surely that can’t be the cause of all of them.

If I were building a trike and heard Van’s response to Barry’s call, I’d be d_mn pissed. I concede to those who’ve pointed out that an RV is an experimental, but it’s also the most popular kit plane currently being sold.

Maybe because I bought a flying RV and haven’t spent countless hours building, I’ve got a little more objective viewpoint. My God, if the gear as designed, can’t make it across a rough, paved active runway under direct control by the FAA, what does that say about the chances of making a successful forced landing on anything worst?!?

So many of the posters in this thread have brought to mind that old Mark Twain quote, “Denial ain’t just a river in Egypt”.
 
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I'll take that back, you need to drill two holes for role pins that will hold the outside spacers. You will get a spacer that goes in between the bearings on the inside, they set preload. So the main bolt through the center gets tightened to hold things in place, it doesn't set preload.
 
Low n Slow said:
My God, if the gear as designed, can?t make it across a rough, paved active runway under direct control by the FAA, what does that say about the chances of making a successful forced landing on anything worst?!?
Click to expand...

Many here, are still awaiting, to see pics of the runway intersection. I suppose you already have?

BTW --- The flipped RV taildraggers I spoke of. Two were 6's landing in fields, and one was a 3 that drifted off the side of the paved runway. I haven't noticed many 6A flips either....

Personally, I don't feel that small diameter wheels and wheel pants, make for good off runway machines.

L.Adamson --- RV6A
 
Hello Steve.

allbee said:
I'll take that back, you need to drill two holes for role pins that will hold the outside spacers. You will get a spacer that goes in between the bearings on the inside, they set preload. So the main bolt through the center gets tightened to hold things in place, it doesn't set preload.
Click to expand...

How is the spacer adjusted for fit?

Kent
 
Forced landings

So you're flying along and the engine fails in an -A model. What is the likelyhood that you're going to try to stretch that glide to make smooth pavement and to avoid a landing on a dirt road or a field? We know that odds are you're going to be on you back with the unpaved choices.

Of course, the best choice for any airplane faced with a forced landing IS a smooth surface but if you can't hang your hat on the strength of the nose gear, you'll have one more thing to think about during a bad situation. As we know, stretching glides can lead to very unpleasant outcomes.

Kelly Johnson
 
Here we go again with people jumping to conclusions.

People have landed -A model RVs off field and kept the airplane upright.

Yes, I will definately agree that taildragger RVs stand a better chance of staying upright in this situation (although as already stated it's no guarantee as several taildraggers have in fact ended up on their backs...it's just gonna happen in either design if the wheelpants get jammed up with grass/weeds/mud).

Saying that landing an -A model off field is definately going to get you on your back is jumping to conclusions big time. Furthermore it is unwarranted and unproductive to improving the design.

office_space_kit_mat.jpg
 
kentb said:
How is the spacer adjusted for fit?

Kent
Click to expand...

With washers between the spacer bar and the side of the yoke. Even using thin washers, it is a fairly crude way of setting preload. Also difficult to get the washers into place. To cure these ills, I machined out a pocket (don't remember the diameter) into the end of the spacer and made some hat-shaped spacers, each a couple thousandths thicker than the last. The washers "nest" in the end of the spacer bar and don't move as the assembly is inserted. Keep using thinner spacers until you get the right preload. Thinner spacer equals tighter bearings, not exactly intuitive, but that is how it works. I went for a preload that didn't restrict tire rotation but also didn't allow any detectable side movement. I used brass for the washers.

Bob Kelly
 
L.Adamson said:
I haven't noticed many 6A flips either....
L.Adamson --- RV6A
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My thought here, as to why there seem to be more RV-7A,9A flips than the 6A is the length of the main landing gear. The 6As set lower down in back and thus the vertical position of the CG is lower. It would take more to flip one.

My guess at least...
6A is sort of half way to a tail dragger :p
 
Short Pole Vaulters

GrayHawk said:
... The 6As set lower down in back and thus the vertical position of the CG is lower. It would take more to flip one...
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I agree. The 6A's do sit at a lower angle. You don't see many short, SQUATTY pole-vaulters do you? Most of them have a high CG so it makes the pole (spring) work better! :eek:

Don
 
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GrayHawk said:
My thought here, as to why there seem to be more RV-7A,9A flips than the 6A is the length of the main landing gear...
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Has an -8A ever gone over because of the front gear leg?

I simply don't remember reading about this problem on the -8A and it makes me wonder what the difference is. It could be that there aren't that may -8A's out there.
 
Bill has an interesting point here.

N941WR said:
Has an -8A ever gone over because of the front gear leg?

I simply don't remember reading about this problem on the -8A and it makes me wonder what the difference is. It could be that there aren't that may -8A's out there.
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I wonder what the ratio of

RV6 to RV6A
RV7 to RV7A
RV8 to RV8A
RV9 to RV9A

My guess that the A dominate the -9 and -7 planes, but not -8 and -6.

Anyone know?

Kent
 
N941WR said:
Has an -8A ever gone over because of the front gear leg?

I simply don't remember reading about this problem on the -8A and it makes me wonder what the difference is. It could be that there aren't that may -8A's out there.
Click to expand...

At least one here off the top of my head. In this case though, there was apparently a hard landing with a bounce that may have precipitated the failure.
 
Short legs

I think there is something to this, dont recall hearing about flip overs until the tall legs came out. I still have the old nose gear on my 6A and have gone into a few grass strips. The last one was rougher than I would have liked and the nose bounced considerably. In all rights it should have gone over, bit my lip on the second nose wheel bounce , kept it light, stick all the way back, and no sign of digging in once we stopped. Was also using a fair amount of braking as the field was a bit short too. Thought it might have been me, bad technque but when taxing out later to leave I relized how rough it realy was.

My 6A is light, with wood prop, and O-320
 
Approaching 20,000 Views

Wow! Do you think very many people are interested in the nose gear topic? As of 21:25 UTC today, there have been 19,554 views of this thread. That's views, not people, as some folks may come back more than once. But that's a lot of interest in this topic. Not sure what the all time record is in this forum, but this one is HOT!!!

Don
 
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Ya

Makes me wish I built a taldragger...I mean all good acro pilots fly taildraggers right?..:)

Frank
 
L.Adamson said:
Many here, are still awaiting, to see pics of the runway intersection. I suppose you already have?

BTW --- The flipped RV taildraggers I spoke of. Two were 6's landing in fields, and one was a 3 that drifted off the side of the paved runway. I haven't noticed many 6A flips either....

Personally, I don't feel that small diameter wheels and wheel pants, make for good off runway machines.

L.Adamson --- RV6A
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Of course I have no idea about the particulars of this latest incident, but if the FAA doesn?t close or fix the runway after this, how bad can it be?

I certainly agree with you on our small tires and off runway landings.

Flipping is my biggest fear flying my RV-4, given its tiny cockpit I think getting out on my own would be near impossible compared to a -6. Do you know what the outcome of the -3 flip was?
 
OK, I will say it........

There is obviously a problem with these nose gears... Before the bashing begins, no, I don't have a tail-dragger nor an A-model completed. But still....what's up with this?

Sure, Van's has jillions of hours on their demo's, and I have racked up some of that time myself. But they have a really nice paved strip up there.

It seems to me that many people try to use pilot error / misjudment, bad field surfaces, etc. But why in the heck does this keep happening? The RV is an awesome aircraft and to have an issue such as this (being a frequent occurence) just amazes me that there isn't a svc bulletin for a very rugged solution?

There are a ton of people on this forum who regularly fly (flew) out of grass strips every single day (Roberta comes to mind). Why is it that some of these people have tremendous results but yet someone else hits a small rise in the pavement and everything folds up? I am no rocket scientist, but surely there is some type of material out there that simply won't fold up? Price? Sure, that's a factor. But so is a Lyc rebuild, a plane rebuild, a possible fatality, etc. At the end of the day, an expensive nosegear that won't collapse is a very cheap investment.

I just don't get it, with all the other wonderful technolgies built into these aircraft. Please don't hammer me as I am not trying to be controversial. I just don't understand the "what if" factor that keeps coming into these discussions about this design. And before someone bashes me on the T/D versus nosewheel debate- I don't have a dog in this hunt. I personally prefer the T/D, but also think the RV 'A' models are awesome too. I just think something needs to be done. And finally, I know these are not trainer aircraft. But someone with hundreds of hours of RV time, who is aware of the potential problem? And then the bad situation of a nose gear still folds up under them? Heck, can't we collectively find a solution to a material that won't collapse?

OK, let the bashing begin as I am sure it will.......
 
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Rocket Science

This is not Rocket Science. When you put a LONG - Skinny - Tubular piece of hardened spring steel on a nose wheel plane you must be ready to fly and land the plane. It will and can act like a polevault stick and ruin your day. That said, I've seen at a recent fly-in, an RV8A, (2) 6A's and (2) 7A land on a turf runway that I would'nt fly an ultralight off of. The nose wheel is for taxi and takeoff only... on Van's RV (A) model designs PERIOD! I watched how the pilots landed and handled their planes... it speaks for itself.

From what I read from the pilots first initial post and in his own words this Thread should be renamed as

RV9A Pilot folds the nose wheel
 
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THE SEAL..THE TORQUE.. AND THE FORK

IN 1998, Van?s changed from using a CLEVELAND wheel, to a MATCO wheel for the nose of the 6A. The Cleveland wheel uses a Timken bearing #LM67040 and a felt seal. In the picture below, you can see that the bearings ride on an one piece axle? U609.
6aconst013et8.jpg



In the next picture you can see the MATCO wheel that came in kits starting in 1998. Notice the change to a two piece axle.. There is no felt dust seal like on the Cleveland wheel. Matco uses a Timken bearing #LM67000L-A. This bearing has a rubber seal built on to the outer race of the bearing.
6aconst012hq3.jpg


THIS SEAL IS THE PROBLEM. It is not needed for this application. This seal makes contact with the inside of the wheel where the bearing is, and causes friction. If you torque the wheel bearing too much, it makes more friction. The felt seal is friction free. Van?s instructions say to torque this bearing to 7-10 FT LBS. This seal WILL NOT allow you to feel the set of the bearing. If you have never set the bearings on the front end of a car, then you don?t know what I mean.

IT GOES LIKE THIS?.. Snug up the nut as you rock the wheel to seat the bearing. Back off the wrench about a quarter of a turn and then with three fingers (two and a thumb) and the wrench at 3:00 if right handed, work the wrench up and down to just take ALL OF THE PLAY out of the bearing, PLUS just a little more. That?s it stop there your done. Now if you just greased the bearings, and have a felt seal, the drag that you feel will be from the grease. This procedure is hard to do with the rubber seal.

NOW GET YOUR TORQUE WRENCH and check the nut. You might see about 10 to 12 INCH POUNDS. Remember, it is a nylock so read the chart.


NOSE GEARS STARTED TO FAIL about 2000, and a change was made to correct the problem. The first legs were made to flex the most close to the socket. The NEW legs as of 2000 or so were made to flex the most about 7 inches up from the 45 bend. So now when the wheel slows down due to friction in the bearing, grass, wheel fairing dragging on the tire or a pot hole or an uneven surface, the wheel tucks under and causes the fork to tilt forward. If the nut hit?s the ground, then you might bend the leg , or go over!!! If the nut does not hit, then the wheel will spring back to it?s normal position.

WARNING LABEL on the bearing as it comes from TIMKEN??.
6aconst011wp0.jpg



THE FORK HAS A PROBLEM. All three of my forks (WD630) were under size between the forks. Once you pressed the wheel with the axle adapter in place, the bearings were already too tight.


SO WHAT TO DO IF YOU HAVE A MODEL ?A????


1. Trust Harmon to make you a good gear leg. That?s all we can do there for now.

2. Install the NEW FORK. More clearance is always a good thing.

3. Open up the fork so the wheel and axle adapter will just slip in between the fork with no load on the bearing.

4. Install a GROVE wheel & axle kit? part # 59-1ARV. And learn how to adjust the bearings. see image below.
The torque spec. of 90 in. lbs. is because the bearing play is fit with the center spacer, and the through bolt is not setting free play.

5. The bearing drag has been reduced by #3+4. Now work on INDUCED drag?.. The places you make the nose wheel go.

6. Keep the nose wheel properly inflated and the break out force set.

On take off, my nose wheel is off of the runway at 13 MPH at full gross.

PIPER NOSE WHEEL....
hpim1520dv3.jpg

CLEVELAND NOSE WHEEL...
6aconst013do8.jpg

GROVE NOSE WHEEL...
grovewheel002ti9.jpg

MATCO NOSE WHEEL...
6aconst012lw0.jpg

Note that MATCO is the only one that uses a two piece alxe, and also the only one that used a rubber dust seal.......

YOU BE THE JUDGE.
 
My inspection of runway 23

194WE said:
Did anyone get a look at the runway area that started all of this?
Click to expand...

Yes, I finally had a chance to check it out tonight.

I'd like to preface my post by expressing my sympathies to Barry. That sucks to have your airplane damaged, no matter what the circumstances. I'm just glad you were not seriously hurt, and that your airplane was not damaged beyond repair. Building a -7A myself, this latest nose gear incident is obviously disconcerting to me as well.

Now, I'm based at MYF, and I've used runway 23 plenty (with Cessnas and Pipers, not yet an RV). Yes, it is the crosswind runway, but it's actually used quite often. I've never thought of it as a rough runway. True, it's not quite as smooth as 28R & L. But it's no worse than half the runways in southern California.

Tonight I went out there and walked much of the length of runway 23. I couldn't find any defect in the pavement greater than about 1/4" in height/depth, including where runway 23 intersects 28R and 28L. It is possible to see and feel where the 28 runways have been paved over 23, but there's no sharp lip to speak of. It just smoothly rises approximately 1/4". Quite normal and reasonable in my opinion.

So is a runway like MYF's 23 really bad enough to bring down a tri-gear RV under otherwise normal conditions??? I sure hope not. If it was, then I'd think these A's would be dropping like flies all over the place (much more frequently than they actually are). There has to be more to this...

P.S. I have my own suspicions/opinions about the vulnerabilities of Van's nose gear design, and about Van's attitude on the matter, and about some of the attitudes expressed on this thread. But I'll save those for another post and another day. Expressing opinion is fine, but let's all please distinguish between speculation and fact.
 
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Gasman.....

Great Post. Very informative and to the point. One question I have regarding the Grove wheel and axle kit.....Is the axle all set up for the RV nosegear fork in regards to width? Can I assume that the part number "59-1ARV" with the "RV" suffix inicates it is designed specifically for RV's?

I have about 80 hrs on my 6A and my nosewheel is as stiff as all getout. It really has not "broken in" at all from what I have observed. I get a slight fore-aft oscillation betweern 39 and 30mph on rollout. This is with the new fork.

I too agree that this drag in the nosewheel is not good and I am seriously considering changing to the Grove.

Again, thanks for the post Gasman.
 
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painless said:
.......I get a slight fore-aft oscillation between 39 and 30mph on rollout. This is with the new fork.

I too agree that this drag in the nose wheel is not good and I am seriously considering changing to the Grove.......
Click to expand...
Jeff:

As a data point, consider this: My nose wheel did not spin freely either and like yours, my RV suffers from that fore-aft oscillation on the nose gear leg fitted with the new fork at high taxi speeds as I outlined in a previous post on this thread. A moment of firm braking is all that is required to stop the oscillation. Still, that shaking is a real nuisance and you shouldn't have to put up with it. Following through on the theory of a well-intentioned tip posted on the same thread, a few days ago I fabbed up a dirt simple axle spacer made with a combination of 1" thick walled PVC pipe over a length of steel tubing because that's the material I had on hand! Hardly precision work, but a heck of a lot cheaper than going Grove. Don't get me wrong. I'd spend the money if I thought it would do any good. :)

Nevertheless, my minimalist effort produced a nose wheel that does spin freely now. Still, I am sad to report that after a handful of flights, the "fix" has not made the problem go away and cannot report ANY improvement worth mentioning. I must conclude that an axle spacer may not necessarily be THE silver bullet fix many of us hope for.

It would be interesting to find out if anyone who has gone the spacer route (either by investing in the Grove design or some other method) STILL suffers the leg oscillation at any normal range of taxi speeds and would be willing to admit it.
 
Rick6a said:
Jeff:

As a data point, consider this: My nose wheel did not spin freely either and like yours, my RV suffers from that fore-aft oscillation on the nose gear leg fitted with the new fork at high taxi speeds as I outlined in a previous post on this thread. A moment of firm braking is all that is required to stop the oscillation. Still, that shaking is a real nuisance and you shouldn't have to put up with it. Following through on the theory of a well-intentioned tip posted on the same thread, a few days ago I fabbed up a dirt simple axle spacer made with a combination of 1" thick walled PVC pipe over a length of steel tubing because that's the material I had on hand! Hardly precision work, but a heck of a lot cheaper than going Grove. Don't get me wrong. I'd spend the money if I thought it would do any good. :)

Nevertheless, my minimalist effort produced a nose wheel that does spin freely now. Still, I am sad to report that after a handful of flights, the "fix" has not made the problem go away and cannot report ANY improvement worth mentioning. I must conclude that an axle spacer may not necessarily be THE silver bullet fix many of us hope for.

It would be interesting to find out if anyone who has gone the spacer route (either by investing in the Grove design or some other method) STILL suffers the leg oscillation at any normal range of taxi speeds and would be willing to admit it.
Click to expand...

Interesting, now have you taken the wheel and had it balanced. On my kitfox I had wheel shimmy on take off with the mains, this airplane is a tail wheel, when I put on new tread I spent the extra and balanced the wheels. Big improvement, no more shimmy. They put a bunch of weight on each tire to get them to balance.
 
painless said:
Gasman.....

Great Post. Very informative and to the point. One question I have regarding the Grove wheel and axle kit.....Is the axle all set up for the RV nosegear fork in regards to width? Can I assume that the part number "59-1ARV" with the "RV" suffix inicates it is designed specifically for RV's?

I have about 80 hrs on my 6A and my nosewheel is as stiff as all getout. It really has not "broken in" at all from what I have observed. I get a slight fore-aft oscillation betweern 39 and 30mph on rollout. This is with the new fork.

I too agree that this drag in the nosewheel is not good and I am seriously considering changing to the Grove.

Again, thanks for the post Gasman.
Click to expand...
CALL GROVE..... 619-562-1268

Yes this is the kit for a two place A's

Groves wheel solves the bearing free play problem, The seal drag problem and the axle problem.

You will still need to address the fork pinch problem, and also install the new type fork. And then keep the break-out force set, and tire pressure up. The wheel pant front cup should be altered so it won't get pushed back into the tire if it hits the ground. Do a search on this.... It was covered quite well in the past.

As you can see by now, IT IS NOT JUST PILOT ERROR.
 
Proper Torque

gasman said:
THIS SEAL IS THE PROBLEM. It is not needed for this application. This seal makes contact with the inside of the wheel where the bearing is, and causes friction. If you torque the wheel bearing too much, it makes more friction. The felt seal is friction free. Van?s instructions say to torque this bearing to 7-10 FT LBS. This seal WILL NOT allow you to feel the set of the bearing. If you have never set the bearings on the front end of a car, then you don?t know what I mean.

IT GOES LIKE THIS?.. Snug up the nut as you rock the wheel to seat the bearing. Back off the wrench about a quarter of a turn and then with three fingers (two and a thumb) and the wrench at 3:00 if right handed, work the wrench up and down to just take ALL OF THE PLAY out of the bearing, PLUS just a little more. That?s it stop there your done. Now if you just greased the bearings, and have a felt seal, the drag that you feel will be from the grease. This procedure is hard to do with the rubber seal.
Click to expand...

Having raced RWD sports cars in an earlier life, I have plenty of experience with installing hubs and taper bearings. I understand what you are saying about feel. Matco recommends a different procedure that does not include 'backing off' the way we all learned. Matco says to expect more drag than a freely spinning wheel. Details on this FAQ page.

gasman said:
NOW GET YOUR TORQUE WRENCH and check the nut. You might see about 10 to 12 INCH POUNDS. Remember, it is a nylock so read the chart.
Click to expand...

Matco says higher drag is normal for this type bearing. Its possible that Van's instructions were not updated with the change in bearing design -- a possible source of some problems if Van's instructions are not congruent with Matco's.

The higher NW drag certainly has an effect on the system. But I haven't seen an analysis that actually proves its undesirable. Since there is no other obvious/effective damping in the system, its possible that the higher drag serves that purpose.

There are dozens of variables to consider when designing a suspension system, even as one as simple as a nose wheel. One I'm particularly curious about the is rake of the nose leg. Its easy to imagine all sorts of consequential effects, good and bad, from different angles. I hope the angle in use was chosen with an eye toward dynamic performance in addition to other obvious design objectives like propeller clearance.

Any thoughts?
 
Rick6a said:
Jeff:

As a data point, consider this: My nose wheel did not spin freely either and like yours, my RV suffers from that fore-aft oscillation on the nose gear leg fitted with the new fork at high taxi speeds as I outlined in a previous post on this thread. A moment of firm braking is all that is required to stop the oscillation. Still, that shaking is a real nuisance and you shouldn't have to put up with it. Following through on the theory of a well-intentioned tip posted on the same thread, a few days ago I fabbed up a dirt simple axle spacer made with a combination of 1" thick walled PVC pipe over a length of steel tubing because that's the material I had on hand! Hardly precision work, but a heck of a lot cheaper than going Grove. Don't get me wrong. I'd spend the money if I thought it would do any good. :)

Nevertheless, my minimalist effort produced a nose wheel that does spin freely now. Still, I am sad to report that after a handful of flights, the "fix" has not made the problem go away and cannot report ANY improvement worth mentioning. I must conclude that an axle spacer may not necessarily be THE silver bullet fix many of us hope for.

It would be interesting to find out if anyone who has gone the spacer route (either by investing in the Grove design or some other method) STILL suffers the leg oscillation at any normal range of taxi speeds and would be willing to admit it.
Click to expand...


Thanks for the input Rick. I jacked up the 6A today and tried the spin-test on my nosewheel. Forget about it turning 1.5 turns after spinning it. It just stops dead in its tracks. Even with the axle nut off, I get the same affect. My fork is not so tight as to preload the mushrooms either. The wheel drops out from between the forks with ease.

A friend of mine, who is a racing parts manufacturer (Coleman Racing) came over and we took the wheel off the fork. Same thing occurs just holding the Mushrooms with zero preload. His thought is to slightly mill/hone (not sure of the term...I am not a machinist) the area where the sealed bearing inserts into the wheel. Basically accelerating the "break-in" period.

I do agree that the seal drag will not completely eliminate fore-aft oscillations. Once they get started, there is nothing in the design to dampen them. With the nosewheel off, you can see it by just pushing on the gearleg aft and then letting it go. Boing boing boing..... Its just the nature of the gear leg.

Rick, was your nosewheel really stiff...as in no free spinning at all like mine? Just curious.

Mr. Coleman is going to take my wheel to the shop and hone it down ever so slightly and we will see what results I get. Won't know until the weekend, so stay tuned.
 
painless said:
.......Rick, was your nosewheel really stiff...as in no free spinning at all like mine? Just curious.......
Click to expand...
Jeff, I don't know how to define "really stiff" but the nosewheel was stiff enough so that no matter how hard you tried to spin it by hand, it would not move very far.......but the friction preventing it from doing so seemed easy to overcome and did not feel all that bad to me, but then I'm no expert in such matters. Now with the spacer in place, I do get a revolution or slightly better when spinning it by hand....definitely less resistance than before.....but like I said.... it has done virtually nothing to reduce the forward/aft oscillations when the nose wheel finally settles upon the runway. Took the wife up this morning to tour the local flood waters and the flight was otherwise flawless...upon returning she barely felt the tires squeak upon contact with the runway surface until that @#$! nosewheel finally made contact and I had to apply a momentary dose of heavy braking to stop the oscillation which would otherwise have become increasingly severe. "Why'd you do that?" she wondered. "Don't ask" I said as we taxied back to the hangar. Next, I'm going to have the wheel and tire balanced and see if that helps any. Additional data point: I routinely try to maintain 33-35 lbs of air pressure in the nose tire and wonder if I should play around with that too.
 
painless said:
I jacked up the 6A today and tried the spin-test on my nosewheel. Forget about it turning 1.5 turns after spinning it. It just stops dead in its tracks. Even with the axle nut off, I get the same affect. My fork is not so tight as to preload the mushrooms either. The wheel drops out from between the forks with ease.

A friend of mine, who is a racing parts manufacturer (Coleman Racing) came over and we took the wheel off the fork. Same thing occurs just holding the Mushrooms with zero preload. His thought is to slightly mill/hone (not sure of the term...I am not a machinist) the area where the sealed bearing inserts into the wheel. Basically accelerating the "break-in" period.

Mr. Coleman is going to take my wheel to the shop and hone it down ever so slightly and we will see what results I get. Won't know until the weekend, so stay tuned.
Click to expand...

Take a razer blade and trim off the part of the seal that is close to the rollers, this will reduce the drag. And be sure to grease the area that the seal runs in the wheel. The seal stays still with the mushroom and the lower race, and the wheel has to spin around it. THAT IS WHERE THE DRAG IS....

THE PICTURE on the left is the bearing resting on the race. THE PICTURE on the right is with the bearing seated in the race. See how the seal is expanded near the race? Kind of like your gas cap.....:eek:
6aconst007ft7.jpg
6aconst008cy7.jpg
 
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Rick...I think I must have tighter seals than you, as I can't spin my wheel worth a hoot. As I said, there is no "free-wheel'n" at all even when the bearings are not loaded. So I don't think even a spacer would help in my case.

Gasman....That is an option to releave some of the bearing seal drag. My friend caters to big time racers from NASCAR and has the equipment to do a really accurate job. Plus it gave him something to do! ;) So I will see how things go. Like I said, I am not expecting my oscillations to be eliminated entirely. To be honest, mine are not as bad as yours, Rick. I may have a bit more luck with a more freely spinning nosewheel.
 
number of nose gear failures

Does anyone know the actual number of nose gear failures that have occurred as a result of the nut digging in or the gear bending back either of which damage the plane in some manner? Might be an interesting number.
 
I had an interesting thought, what if the wheel didn't pivot. Sounds like it might have tried to turn but sciffed sideways and caused it to bend and flip under. I had a simular type of thing with my tail wheel on my kitfox. I tried to make a turn and the tail wheel wouldn't turn, and then pop it would turn. I ended up taking the thing apart and greased the thing up real good, that did it, worked great afterwards. Oh and if I took the weight off the wheel it worked just fine.
 
RV9/A accidents/incidents

questair said:
Does anyone know the actual number of nose gear failures that have occurred as a result of the nut digging in or the gear bending back either of which damage the plane in some manner? Might be an interesting number.
Click to expand...

Following are what I could find on all RV9/A accidents/incidents. A good percent ended flip over. I am sure that I missed some.
--------------------------------------------------------------------------
4/2/2000 N96RV, Factory prototype 9 (RV-6T), crash in IMC, two killed.
09/05/2002 N945D, 9A, O320, Oxford, OH, Loss power during night flight. Faulty fuel gauge, no fuel in tank
10/19/2003 N786HL, 9A, Subie, Deshler, OH, Turf runway, too high a landing speed without flap, nose over, private TT 2618 hr (118 hr SEL), in type 86 hr.
06/06/2004 N369RV, 9A, Subie, Fort Scott, KS, Auto fuel, vapor lock, engine quite, private, TT 74 hr, in type 41 hr.
06/17/2004 N93AZ, 9A, O320, Sea Ranch, CA, Drift on go-around, hit tree on the side, private, TT 165 hr, in type 62 hr
08/07/2004 N3086J, 9A, O320, Westport, WA, Engine quite, one empty tank, TT 106 hr, in type 40 hr.
06/24/2005 9A, Salmon Arm, BC, Canada, Holding opened canopy during landing, hard bounce collapse nose gear and airplane flip over.
7/27/2005 N219CC, O360, Neednah, WI, during go-around left wing contacted ground, airplane wrecked, 2 minor injury, private, TT 2027 hr (227 hr SEL), in type 29 hr.
08/12/2005 N63EB, 9A, O360, Palmer, AK, Nose over on grass, commercial CFI, TT 2115 hr, in type 115 hr.
11/05/2005 N994W, 9A, O320, Hollister, CA, Hit tie down on grass, Nose gear bent.
04/08/2006 N339DL, 9A, O320, Venice, FL, Nose over, too fast and at nose low attitude during landing, commercial, TT 742 hr, in type 6 hr.
04/16/2006 G-CCZT, 9A, Bicester Airfield, Oxfordshire, UK, During landing flare passenger control stick disconnected, airplane nose down propeller hit the runway, no injury, private, TT 137 hr, in type 45 hr.
8/13/2006 N6699, 9A, O320, Rostraver, PA, Taxi from grass to asphalt nose gear fort hit asphalt, gear damage.
2/24/2007 G-CCZY, 9A, O320, Caernarfon Airfield, UK, bounced landing nose touch down collapse gear, 1 minor injury, private, TT 368 hr, in type 34 hr.
6/29/2007 N394RS, 9A, Tucson, AZ, Engine supercharge problem, off field forced landing, nose over, substantial damage to the airplane and minor injury to the pilot, private, TT 236 hr, in type 57 hr.
7/13/2007 BC, Canada, Engine quite, nose over during forced landing, pilot in serious condition, hit the head during flip over (pilot die in 2 wks)
9/2/2007 G-CDMF, 9A, O320, Oaksey Park Airfield, Wiltshire, UK, bounced landing during gust, nose over, no injury, private, TT 132 hr, in type 18 hr.
9/12/2007 N269RV, O320, Harvest, AL, 3-point landing, nose over, 1 minor injury, private, TT 365 hr, in type 80 hr.
9/20/2007 N3653, 9A, Barton City, MI, Took off from private grass strip. Due to gust (according to passenger) airplane crashed into trees. Two seriously injured.
10/10/2007 HB-YML, 9A, IO320 D1A, K�giswil, Switzerland, During initial climb engine run rough then quite, landed short on return to runway, airplane total, cause of the engine stoppage was the inproperly formed fuel line flaring. 1 minor injury, Private, TT 15,172 hr, in type 11 hr.
10/14/2007 N475TW, 9, Subie, Bigfork, MT, engine quit on downwind, not able to make the runway. 1 minor injury, private pilot: TT 354hr, in type 72 hr
2/21/2008 N159AS, 9A, Egg Subie H6, Princeton, New Jersey, engine quit on takeoff, tow injured.
5/17/2008 N486EM, 9A, Pacific City, OR, Loss power during landing, flip over, minor injury.
6/7/2008 N557BD, 9A, O360, San Diego, CA, hit uneven runway height at intersection during landing roll, nose gear leg bent backward, no injury.
 
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Which nose wheel manufacturer...

painless said:
Thanks for the input Rick. I jacked up the 6A today and tried the spin-test on my nosewheel. Forget about it turning 1.5 turns after spinning it. It just stops dead in its tracks. Even with the axle nut off, I get the same affect. My fork is not so tight as to preload the mushrooms either. The wheel drops out from between the forks with ease.
......
Click to expand...


Just to clarify.... was this an early RV-6A finish kit with the original Cleveland nose wheel, or a later finish kit with the Matco nose wheel?

My original RV-6A plans (sheet 62) don't show anything on the axle could be described as a "mushroom"...
 
az_gila said:
Just to clarify.... was this an early RV-6A finish kit with the original Cleveland nose wheel, or a later finish kit with the Matco nose wheel?

My original RV-6A plans (sheet 62) don't show anything on the axle could be described as a "mushroom"...
Click to expand...

Its a Matco Gil. The mushrooms I speak of are the inserts for the bearings.

To update, my friend did not bore out the wheel as I mentioned. We used Gasman's suggestion to trim the bearing seal. The wheel spins more freely, but still has some drag to it which is probably a good thing.

Flew the airplane and did not experience the fore-aft shimmy as much. I only noticed it decelerating from 39-30mph on rollout originally with full aft stick. Seems to be a bit less now. I will continue to monitor it.
 
More on crash...

I'm curious about the first crash you listed:

4/1999 Factory prototype 9, crash in IMC, two killed.


I could not find it in the ntsb database. Do you have anymore info?
 
I believe that was the accident that claimed Bill Bennedict and his son while they were on their way to Sun 'N Fun. As you noted, it occured in IMC in hilly country in Arkansas IIRC.
 
Folks...

Today I had an opportunity to make what may be a critical comparative observation. The three aircraft observed were a Grumman AA5 Cheetah, a Grumman AA1 Trainer, and a Whittman WH10 Tailwind. All three use a castoring nosewheel, and the Tailwind uses both main gear and nosegear from an RV6A (yes, purchased from Vans, including Vans wheelpants).

All three aircraft were witnessed taxiing on grass down "hangar row", past my hangar, transitioning to rough concrete running downsloap to sharp transition at the edge of the paved taxiway.

Observations:
1) The Grumman nosegear exhibits significantly different geometry than the Vans gear. The principal difference seems to be the longest portion of the nosegear "leg" is much closer to being horizontal than the Vans, which extends downward from the firewall at an angle perhaps between 30 & 45 degrees.

2) The Vans nosegear on the Tailwind very clearly was far more flexible than that of the Grummans. Not just by a little bit, but rather by a LOT.

3) When the Grumman gear flexed to suck up the bumps, the long "arm" of the gear appeared to flex in an up and down motion.

4) The Vans gear-equipped Tailwind exhibited significant fore/aft flexing of the nosewheel when sucking up the bumps, with the long "arm" of the gear appearing to move up and down very little. The angle between the bottom edge of the nosewheel pant and the ground changed quite significantly as the nosegear allowed the nosewheel to move aft when encountering a bump, then flexing forward again once the bump was overrun.

As a result of these observations, as well as the information shared on this and other similar threads here, I have advised the Tailwind owner to reduce his taxi speed to a crawl.

It is my hope that such beautiful airplanes as the RV series are not afflicted for long with what appears to be something less than an optimal nosegear design. Perhaps some of the observations made above will aid in driving the critical thinking necessary to make nosegear failures and tipovers a thing of the past.
 
Canadian_JOY said:
Folks...

Today I had an opportunity to make what may be a critical comparative observation. The three aircraft observed were a Grumman AA5 Cheetah, a Grumman AA1 Trainer, and a Whittman WH10 Tailwind. All three use a castoring nosewheel, and the Tailwind uses both main gear and nosegear from an RV6A (yes, purchased from Vans, including Vans wheelpants).

All three aircraft were witnessed taxiing on grass down "hangar row", past my hangar, transitioning to rough concrete running downsloap to sharp transition at the edge of the paved taxiway.

Observations:
1) The Grumman nosegear exhibits significantly different geometry than the Vans gear. The principal difference seems to be the longest portion of the nosegear "leg" is much closer to being horizontal than the Vans, which extends downward from the firewall at an angle perhaps between 30 & 45 degrees.

2) The Vans nosegear on the Tailwind very clearly was far more flexible than that of the Grummans. Not just by a little bit, but rather by a LOT.

3) When the Grumman gear flexed to suck up the bumps, the long "arm" of the gear appeared to flex in an up and down motion.

4) The Vans gear-equipped Tailwind exhibited significant fore/aft flexing of the nosewheel when sucking up the bumps, with the long "arm" of the gear appearing to move up and down very little. The angle between the bottom edge of the nosewheel pant and the ground changed quite significantly as the nosegear allowed the nosewheel to move aft when encountering a bump, then flexing forward again once the bump was overrun.

As a result of these observations, as well as the information shared on this and other similar threads here, I have advised the Tailwind owner to reduce his taxi speed to a crawl.

It is my hope that such beautiful airplanes as the RV series are not afflicted for long with what appears to be something less than an optimal nosegear design. Perhaps some of the observations made above will aid in driving the critical thinking necessary to make nosegear failures and tipovers a thing of the past.
Click to expand...

I think all you really observed is that two totally different nose gear designs act differently (probably to be expected).
At first blush the Grumman nose gear may look the same as an RV but the only real thing similar is that they have a free castoring nose wheel.
The Grummans use a tubular nose gear leg that is very stiff. The spring action is via a torsion bar that runs the full width of the bottom of the firewall.
With this design the nose gear is not intended to bend. It just hinges up and down with the torsion bar taking all of the spring load.

I guess you could say that the Grumman nose gear is similar to the RV-10 since it uses a stiff tubular leg also but it gets its spring action from two rubber load mount style dough nuts in compression.
 
THE MUSHROOM IS HERE....

az_gila said:
Just to clarify.... was this an early RV-6A finish kit with the original Cleveland nose wheel, or a later finish kit with the Matco nose wheel?

My original RV-6A plans (sheet 62) don't show anything on the axle could be described as a "mushroom"...
Click to expand...

GIL, GO BACK TO POST #176 or click here.... http://www.vansairforce.com/community/showpost.php?p=231999&postcount=176

On the second sketch, part #U623-1 (aka) AXLE ADAPTER is what they are calling the MUSHROOM.
I think your nose wheel is like the first sketch, as is mine. We DO NOT have that bearing with the built in seal.

I think packing the bearings with that seal there would be a problem.
 
Hummm... I got a chance to observe a 7A on the ground doing taxi... N2447RV It did beautifully. No wheel shimmy, the aircraft turned great, no sign of trouble at all. Yup, this was Robertas ex airplane. It was down in Richland when I was there, doing flights for the kids, did many flights and taxi, no problems.
 
Finish kits and wheels makes.

gasman said:
GIL, GO BACK TO POST #176 or click here.... http://www.vansairforce.com/community/showpost.php?p=231999&postcount=176

On the second sketch, part #U623-1 (aka) AXLE ADAPTER is what they are calling the MUSHROOM.
I think your nose wheel is like the first sketch, as is mine. We DO NOT have that bearing with the built in seal.

I think packing the bearings with that seal there would be a problem.
Click to expand...

Warren... I was trying to say the "RV-6A" was not a good description of the wheel axle.

The older -6A kits had Cleveland wheels, but the later -6A finish kits were shipped with Matco wheels.

I believe all -7A and -9A finish kits have Matcos. We should use the wheel make as a descriptor, not the type of kit...:)

I too believe the Cleveland is a much better design, and is similar to that used on certified planes.
 
Scott - I think I was trying in a very quiet way to point out that perhaps the Vans method of using the nosegear arm as the source of spring suspension is, at its core, sub-optimal, and that a suspension system similar to that of the Grumman or RV-10 would be a more appropriate approach to adopt. One doesn't find many Grumman's on their back, so perhaps there is merit to copying a system that works. Hmmm, seems that's what's happened with the RV-10, so I guess if Van is willing to use it on the "biggest and bestest RV" it's not such a bad idea after all...
 
Aftermarket front gear for A-model for sale?

Canadian Joy, I also believe that such a gear is a better system than what we have now. Maybe some genius entrepreneur could offer a sturdier, pivoting, aftermarket front gear for the A-models. I bet there will be a lot of people interested, already flying or still building. There is a couple of thousand potential customers, a lot of them ready to buy!

Regards, Tonny.
 
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