pants or spats?

just want to say.... the pants are thin shells of fibreglas to direct AIR around the wheel in a smooth manner, right?
I think we are expecting a bit much when we think this largely unsupported wafer will affect the direction or path of almost a ton of metal in motion.
in some cases, the pant has delayed or let the gear nut slide aways along the grass before digging in. Okay.
Sure, I put aluminum skid plates in mine too, but don't expect much.
 
I've always thought a gear leg shaped more like the grumman would be what the -A needs. The 'S' shape of the grumman leg allows the gear to flex in the upward direction better than the straight leg design.
 
flyboy1963 said:
just want to say.... the pants are thin shells of fibreglas to direct AIR around the wheel in a smooth manner, right?
I think we are expecting a bit much when we think this largely unsupported wafer will affect the direction or path of almost a ton of metal in motion.
in some cases, the pant has delayed or let the gear nut slide aways along the grass before digging in. Okay.
Sure, I put aluminum skid plates in mine too, but don't expect much.
Click to expand...

Could you post some pics (or point me to some pics) of what the aluminium skid plates look like?

Thanks,

Tom
 
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Sorry, no quick or cheap fix.

Many builders are desperate for a quick and cheap third-party fix for the nosegear problem (in reality it is not so much a "problem" as a matter of a very slender safety margin).

But I doubt that any meaningful third-party "fix" will be forthcoming. Any meaningful improvement to the safety margin can only come from a complete redesign of the nosegear and that can only be done by Vans... because it is a huge undertaking involving not only changes to the nose gear but to the engine mount, to the re-routing of fuel lines and other components, and possibly changes to the lower cowl.

The Vans two-place nose gear is a solid bar that is fixed at the engine mount and relies on flexing of the gear leg to accomodate undulations in the airstrip surface. One of its major weaknesses is that it has no shock absorption per se. It is effectively like a car with springs but no shock absorbers. The energy from a load is simply stored in the spring steel and is free to rebound...this can induce wild oscillations that can diminish ground clearance.

The second weakness is that because it relies on flexing of the nose leg to function it is slender and thus particularly prone to twisting as a result of torsional forces. And there are a lot of torsional forces because the wheel is dramatically offset to the axis of the nose gear leg.

Many builders think that the nose gear effectively fails in bending (after the nose wheel nut bottoms out) but that is an oversimplified view of what will be a very complex failure mode involving compression forces, bending forces and torsional forces. Only a seriously modelled (and expensive) non-linear finite element analysis is likely to throw more light on the failure mode.

The RV10 design works completely differently. Instead of encouraging flexing in the nose leg it resists it by the adoption of a lightweight but larger diameter circular hollow section. The leg (and thus the wheel) is then allowed to move up and down because it is hinged and thus pivots at the engine mount. Kinetic energy is then dissipated by the incorporation of two dampening devices (crude shock absorbers if you like) at the engine mount.

Of course the circular hollow section with its increased OD also has significantly higher resistance to torsional loads. As I've said previously I suspect Vans lifted the design from the Cirrus nosegear which is VERY similar.

I've noticed in recent years that more flying RV7A builders with relatively low hours are starting to complain about looseness of the nose gear leg due to distortion of metal at the leg-to-engine-mount interface where there is only one bolt. They typically report on bruising of the bolt and elongation of the adjacent hole. I take this as further indication that the nose gear design is struggling to cope with the increased loads that the new models with higher gross weights are placing on it.

The VansAirforce nosegear saga has been raging continuously now for over 6 years. No other topic has generated anywhere near as many threads or as many posts. Funnily enough I don't see too many RV10 flyers buying into the argument. They all seem to be quite happy chappies. Hmmmmm
 
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Just a larger fork and wheel is not the cure!

Av8torTom said:
I think this guy is on the right track...

http://mesawood.info/myrv7a/building/newgear.htm
Click to expand...

Yes but what about the longer arm of the fork, putting more force on the thinnest part of the gear leg (the bend). I think that may well make things worse. also any side loads are going to be much higher.

Just try to wiggle the plane about, at the front, and see how that leg bends in any driection! And that is when the plane is just sitting there!

Regards, Tonny.
 
Gear leg stiffener may help?

Captain Avgas said:
The Vans two-place nose gear is a solid bar that is fixed at the engine mount and relies on flexing of the gear leg to accomodate undulations in the airstrip surface. One of its major weaknesses is that it has no shock absorption per se. It is effectively like a car with springs but no shock absorbers. The energy from a load is simply stored in the spring steel and is free to rebound...this can induce wild oscillations that can diminish ground clearance.

The second weakness is that because it relies on flexing of the nose leg to function it is slender and thus particularly prone to twisting as a result of torsional forces. And there are a lot of torsional forces because the wheel is dramatically offset to the axis of the nose gear leg.
Click to expand...

A wooden gear leg stiffener is not the cure but it would help, I suppose?

One other thing that I was thinking about, was to beef up the inside of the fairing. Just a strip a few inches wide, all the way around the top and install some sort of stopper, on the rearside of the gearleg, just above the fairing (approx. where the gear leg fairing ends, sort of in the middle of the wheel fairing). So in case the leg bends at the "bend" with the fork bending upwards, the stopper will hit the top of the fairing, not allowing it to bend any further. OK, if it hits realy hard it will probbaly stil break the fairing, but it may help in some less sever cases.

Regards, Tonny.
 
Pilottonny said:
Yes but what about the longer arm of the fork, putting more force on the thinnest part of the gear leg (the bend). I think that may well make things worse. also any side loads are going to be much higher.

Just try to wiggle the plane about, at the front, and see how that leg bends in any driection! And that is when the plane is just sitting there!

Regards, Tonny.
Click to expand...

Tonny,

I agree - as I said, I think he is on the right track, not that he had solved the problem. He mentions that a redesigned gear leg is probably required. The more I think about it, the more I wonder if somehow using the RV-10 design isn't the best solution. I am however sympathetic to the fact that any solution needs to be easy (and cheap) to retrofit to existing XAs.

Tom
 
Here's a photo that will break your heart!!

Av8torTom said:
MrNomad, I'm not sure I understand how having had the wheel pant on would have prevented the wheel from turning sideways.Thanks,Tom
Click to expand...

Tom: You're right. The wheel pant would not have stopped the wheel from turning sideways, but when the front wheel buckled under bending the nose gear under the airplane, the wheel pant might have provided a relatively smooth surface to slide on versus the fork which dug into the asphalt, bent the gear leg further, lowered the nose causing the prop to strike, thereby bending the crankshaft even though the engine was at idle.

bentgear.jpg


In addition to the damage in this photo, my brand new Superior engine with 64 hours had to be torn apart and a new crank, bearings, etc., installed.

wornfork.jpg


The solution indicates an improved nose gear but that's above my pay grade. In the 120 hours of flight since I repaired this, I have done all I can to prevent a reoccurrence and urge others to pay heed to breakout, inflation, pants, spacers, avoiding rough surfaces, and of course, perfecting your landings.
 
Pilottonny said:
A wooden gear leg stiffener is not the cure but it would help, I suppose?

Regards, Tonny.
Click to expand...

Tonny, I don't think so. The gear leg in the current design is supposed to flex along its entire length. That's the underlying structural principle. By stiffening up the leg with additional reinforcement you simply concentrate bending forces in the vicinity of the upper connection to the engine mount thus greatly increasing stresses in that area which will ultimately lead to other problems.
 
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No, not reinforce...... dampen !

Bob,

As I understand it, the wooden gear leg stiffener is not to reinforce the gearleg, but to give it a different flexing caracteristic i.e. take a bit of the "springy effect" out of it, or in other words, dampen it, so it does not bounce. Maybe it can be done with other materials as well.

Regards, Tonny.
 
On most (ok, all) of the old -6As I have seen, the nose gear fairing has been filled with some some sort of goblygook....not sure what it is. I'm wondering if that filled fairing had the same effect as a gear leg stiffener.
 
Jamie said:
On most (ok, all) of the old -6As I have seen, the nose gear fairing has been filled with some some sort of goblygook....not sure what it is. I'm wondering if that filled fairing had the same effect as a gear leg stiffener.
Click to expand...

In the old days, the RV6A leg consisted of notched wood stiffeners wrapped and fiberglassed to the gear leg. The fiberglass was then finished smooth and painted.

Even though my kit was a 96', I have the new preformed fiberglass fairings and no wood stiffener.

L.Adamson --- RV6A
 
Pilottonny said:
Bob,

As I understand it, the wooden gear leg stiffener is not to reinforce the gearleg, but to give it a different flexing caracteristic i.e. take a bit of the "springy effect" out of it, or in other words, dampen it, so it does not bounce. Maybe it can be done with other materials as well.

Regards, Tonny.
Click to expand...

Tonny, the Vans two-seat nose gear leg is designed using a grade 6150 tapered spring steel solid bar that is fairly elastic and allows for a large amount of deflection under load. This deflection under load allows the nose leg to absorb quite a lot of energy which would otherwise be transmitted as bending moments into the engine mount connection.

When you stiffen up the gear leg by adding ANY additional reinforcement (timber, composite, whatever) you reduce the amount of deflection (flex) in the gear leg and increase the bending moment at the engine mount correspondingly.

The problem with most of the builder mods that have been regularly put forward over the years on Vans Airforce forum to "improve" the current Vans nose gear (gear stiffeners, larger wheels etc) is that in a structural sense they mostly tend to rob Peter to pay Paul.

Having said that I would suggest that there is one third-party retrofit mod that is truly worthy of consideration. That would be the installation of the Grove (or the new Matco) axle spacers that allow for a precisely set bearing preload. These would reduce wheel friction and hence reduce nose gear loads. I'll certainly be installing one of those.

After that it's a matter of recognising the deficiencies in the current mechanism and flying accordingly.
 
Spelling police.

Dr. and James !

Next time I want to see your posts in Dutch.......and no spelling mistakes! Right?:p

BTW, wash their anyboody that dit not understoed what we wass al talkinc aboot? :confused:

Regards, Tonny.

PS: Half of Belgium speaks Dutch, Half speaks French and a handfull even speak German!
 
RTV?

I like the idea of "gluing" a wooden stiffener on the gearleg with RTV. If the wood is not to thick, it will not ad additional strength, but might sure help to (how do I say this in correct english?) damp.

A good bead of RTV may be heavy though. If the RTV is to thin, it will just shear off, I suppose.

Regards.
 
Pilottonny said:
Dr. and James !

Next time I want to see your posts in Dutch.......and no spelling mistakes! Right?:p

(snip)
Regards, Tonny.

PS: Half of Belgium speaks Dutch, Half speaks French and a handfull even speak German!
Click to expand...

Ik zal mijn best doen, maar ik maak geen beloften ;)
 
Why optional axle spacer??

I do not understand what the benefit of the spacer is. The drag is caused by the bearing seals! What is the spacer going to do about that? I did what the manufacturer recommends and cut one of the two seal lips off. The wheel is now running as free as I would expect it to, but still seals well enough to keep dirt out.

I also “staked” and “notched” the mushrooms to make sure the bearing races are not turning on the axle. As far as I can determine now, the assembly runs pretty free and the bearings are doing what they are supposed to.

As for dirt: do not forget that the wheels are only running for a few minutes for every hour of flight. I bet that if you add up all the taxi time, you will only come to something like 50 to 100 hrs for 2.000 hrs. total time on your aircraft. The bearings on my car are holding up approx. 3.900 hrs without maintenance so far (290.000 km at av.75 km/hr). But we will probably disassemble, inspect, clean, re-grease and reassemble the bearings every couple of hours of actual running time!

Regards, Tonny.
 
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Why a steel spacer?

Tonny:

You said: "I do not understand what the benefit of the spacer is. The drag is caused by the bearing seals".

We agree, the drag is caused by the seals. But, depending upon how tight you make the nut on the long shaft that runs thru the wheel, you vary the amount of drag caused by the seals.

A properly sized steel spacer permits the nut to be torqued to achieve a specific amount of drag from the seals, and it won't change over time.

My front wheel spins freely and the seals do their job. It's been 120 hours since I added the spacer. The spacer cost less than a dollar and it works perfectly.

Barry
Tucson
 
Nose gear redesign

Hi Guys

The news from the UK is that the prototype of our new nose gear design will be made this winter and we hope to have it fitted to our 9A for testing in the new year. I will keep this thread updated on progress.
 
Av8torTom said:
I think this guy is on the right track...

http://mesawood.info/myrv7a/building/newgear.htm
Click to expand...

I agree wholeheartedly. Even though the RV10 fork increased the bending moment on the gear leg, it is far less likely that the nosegear would bend simply because the larger tire rolls over holes and obstacles with less effort. I have the same main tires on my rocket and am soon going to be changing over to the 380 tires on my -6.

I have done many formation landings with A-models and one thing's for sure...I've never seen one NOT shimmy like its about to fall off. The cure for that would be to add more caster to the nose gear fork.

Ultimately the best solution would be a combination of this genteman's mods, a redesigned fork with more caster angle, and a slightly shortened nosegear leg to accomodate the increased caster angle.
 
Not the "S" shape...

Walt said:
I've always thought a gear leg shaped more like the grumman would be what the -A needs. The 'S' shape of the grumman leg allows the gear to flex in the upward direction better than the straight leg design.
Click to expand...

...but the torque tube (24 below) that goes across the entire width of the fuselage is the "spring/flex" item on a Grumman.

AA1-5-nose-leg-boot.jpg
 
Apologies?

Thanks Gil !

I hate it when people tell me I make mistakes, so I am very glad I had it right after all. Do you think I am entitled to get apologies? :p

Anyway, Marry Christmas and a Happy New Year to everybody.

Tonny.
 
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