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Conventional Gear Configuration

M

mmcdonald

Active Member
RV-3,4,6... have gear legs attached at engine mount (fwd cg) and slope aft.

The RV-8 legs are attached close to cg and slope forward.

Curious, if one could choose, which configuration would you prefer?

Which configuration is more stable or forgiving during takeoff and landing?
 
I am gonna out on a limb here and say the 8 is more stable--------but not due to the mounting position, but due to the flat stock it is made from.
 
I agree with Mike. RV8 gear is more forgiving and less "springy" but pilot error is not going to be overcome with this alone and I would not make my buying decision on that. There have been some issues with tracking that don't seem to plague the other models, but that can be worked out.
I personally feel the gear location on the 8 is the least attractive feature of this super nice looking airplane, but that is just me.... I prefer the look of the gear on the other models better, and they obviously work.
 
The RV-8 gear is probably more stable, but it also more complex, more difficult to build, and requires more maintenance. AND; It just doesn't look like an RV!

OK Guys; Pile on!
 
Mellllll, Mel, Mel, Mel, Mel. You are quite incorrect sir. The RV-8 gear is rather the MOST attractive of the line! They don't have that "gee, I'll tack them on here because it's the easiest spot" look to them! :D
 
Veetail88 said:
Mellllll, Mel, Mel, Mel, Mel. You are quite incorrect sir. The RV-8 gear is rather the MOST attractive of the line! They don't have that "gee, I'll tack them on here because it's the easiest spot" look to them! :D
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And just WHERE did I say they were not attractive? I said "They don't look like RV landing gear!" as in the RV-3, -4, -6, -7, and -9.

I still stand behind my statement.

But even though I didn't say it, IMO, the "RV' gear IS more attractive. And attractiveness IS opinion. You have the right to yours, even when it is wrong.
 
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Landing Gear

The Wittman round gear is only in perfect alignment for one load/cg condition. As the airplane is loaded the gear will bend in multiple directions, most important is that the gear will toe out more and more as the airplane is loaded. This includes not only static conditions but hard landings. In the real world this is not really a problem.
The plus of the Wittman gear is that much of the load of the firewall forward (engine, prop etc.) on landing is not transferred into the fuselage structure. Also the steel tube mounting assembly is inherently stronger than the flat gear mounting. Wittman stated that a properly installed round gear, in an extremely hard landing, would remain intact and absorb energy until some part of the airplane touched the ground.
Steve Wittman designed and patented the flat spring gear in the mid thirties, he sold the design to Cessna at the end of WWII. he designed and patented the round gear sometime in the late 40's early 50's.
 
In the eye of the beholder

When I first saw the RV-8 I wasn't sure how I felt about the gear. It was just so different than what I was use to. Now....seventeen years later, I think the RV-8 is the most handsome RV of the fleet, and the pick of the RV litter!
 
mmcdonald said:
Which configuration is more stable or forgiving during takeoff and landing?
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Hard to imagine anything more stable or forgiving on the ground than the rod gear. If by "stable" you mean mechanically stable, the leaf spring RV-8 gear wins, since it does not easily flex in as many axes as the rod gear. But I think you're splitting hairs wondering which is more stable or forgiving from a practical standpoint. Both are very easy to manage...as tailwheel airplanes go.
 
Conventional Gear

I used to think that the gear on the RV-8 must be better functionally than the rod gear on the RV-4, as well as more attractive, however I saw an interesting video at Oshkosh presented by Van's. They tested the rod gear on the new RV-14 by loading up a -14 fuselage to max weight with lead and then dropping it from height ( 6 ft or so?) to simulate a hard landing. The video shows the gear flexing and resuming its normal shape as if nothing had happened - very impressive. They should post the video on their website, it would certainly convert some of the doubters about rod gear.
 
Gear

t4tango said:
I used to think that the gear on the RV-8 must be better functionally than the rod gear on the RV-4, as well as more attractive, however I saw an interesting video at Oshkosh presented by Van's. They tested the rod gear on the new RV-14 by loading up a -14 fuselage to max weight with lead and then dropping it from height ( 6 ft or so?) to simulate a hard landing. The video shows the gear flexing and resuming its normal shape as if nothing had happened - very impressive. They should post the video on their website, it would certainly convert some of the doubters about rod gear.
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If the RV8 were tested side by side with a rod gear airplane and the drop test height was incrementally increased to failure, the flat gear attach structure would ultimately fail well before the rod gear structure.
 
jrs14855 said:
If the RV8 were tested side by side with a rod gear airplane and the drop test height was incrementally increased to failure, the flat gear attach structure would ultimately fail well before the rod gear structure.
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I don't think that is necessarily a valid statement.
I say not necessarily, because actually doing the test would be the only way to know for sure.
I have participated in gear drop tests for the RV-8 and it met the requirements for the calculated limit and ultimate loads. Actual drop tests have never been done on the RV-7 gear. The design was done by extrapolation based on the long service history of the RV-6.
Both gear styles on the conventional gear RV-8 and RV-7 impose huge loads on the fuselage. Just not in the same ways.
 
The 8 is a like Cindy Crawford, a supermodel. The gear is like her mole. A bit awkward, but the rest makes up for it :D

I have seen a 7 collapse the gear to the point of a prop strike. The gear was not reusable and had to be replaced. So, I wouldn't say either set up can survive a severe hard landing.
 
I remember reading Clarence ?Kelly? Johnsons? biography years ago, the designer of the SR-71 and a multitude of other unparalleled aircraft. One statement he made to young engineers involved with his designs was to ?Think like an air molecule, how you would like to go around that structure that is fast coming your way??. The KISS principle is also one he adhered to ?keep it simple, stupid?.

My first close look at an RV4 in 1985 encompassed at least those two Kelly statements. The flight following that inspection merited that ?if it looks good it probably flies good?. Good is an understatement for Van?s second design off the drawing board. I?m pretty sure Van read those design philosophies before designing the -4.

A picture is worth a thousand words.
Cheers, Hans


292bk3q.jpg
 
Why is the 8 different from the 4? Would it be so that it is easier to change from traditional to nosewheel configuration?
 
Yen said:
Why is the 8 different from the 4? Would it be so that it is easier to change from traditional to nosewheel configuration?
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Nope, there is much internal structure differences from nose to tail wheel on the 8. I think the gear location is dictated by the lengthened fuselage and getting the CG in the right location for ground handling.
 
Conventional gear

I would say that the Whitman style gear on an RV is the most sexiest, sleekest thing on the plane. With the gear properly aligned and faired it flies great and looks even better then the -8 gear. Sitting on the ground, it looks fast.
It's also the lightest.
I have seen lot's of RV's with conventional Whitman style gear wheel landed, ROCKETS TOO!
The RV-8 just does not seem to look right to me. Also, remember all of the tail buffeting issues and fences that come with it. In my mind, Van's kind of screwed up on this. When they wanted something bigger than an RV-4 and tandem seating, they had the chance to aquire the Rocket design. One of the things was a wider fuselage and keeping the trailing gear legs. They thought there was going to be handling issues due to the distance the wheel center was away from the CG. The airplane was flying and already existed. But Van's being Van's, they did not want to incorporate another person's design into their line. So they designed a whole new airplane. With a heavier gear, more parts to manufacture, more complex to build and took up a lot of cockpit space they were after. You look at a Rocket and then an -8 and wonder what someone was thinking. Nothing got solved by building and -8 with straight gear.
I would say they are more stable to land and you can shim the gear/axle if there is alignment issues. But at what cost of the all the other issues the straight gear created.......
 
I like it just the way it is!

I haven't landed or finished my -8 yet, but from an aesthetic perspective, I prefer the -8 gear. The swept back gear legs look like they're trying too hard to tell you that, "this is a fast airplane". The straightforward, no nonsense legs of the -8 seem to say, "I don't care whether you think I look fast or not, I'm going to eat you like a grape!"

Plus, the Grove Airfoil legs are the dead sexiest pieces of metal I've ever seen. Sure, I'd rather not deal with the gear towers, but if the wings and tail aren't swept back, the landing gear shouldn't be either.
 
Saber25 said:
I remember reading Clarence “Kelly” Johnsons’ biography years ago, the designer of the SR-71 and a multitude of other unparalleled aircraft. One statement he made to young engineers involved with his designs was to “Think like an air molecule, how you would like to go around that structure that is fast coming your way?”. The KISS principle is also one he adhered to “keep it simple, stupid”.

My first close look at an RV4 in 1985 encompassed at least those two Kelly statements. The flight following that inspection merited that “if it looks good it probably flies good”. Good is an understatement for Van’s second design off the drawing board. I’m pretty sure Van read those design philosophies before designing the -4.

A picture is worth a thousand words.
Cheers, Hans


292bk3q.jpg
Click to expand...

It would be worth the same amount of words if it was sized according to VAF instructions........

"One such place is www.TinyPic.com. Another site is www.Photobucket.com (select the 800x600 option for your picture for best forum results)."
Find it here....http://www.vansairforce.net/articles/ImagesInForums/images.htm
 
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Thanks Gasman,

I wondered why that came out so large. Not into posting pictures often enough to stay current.
 
Saber25 said:
A picture is worth a thousand words.
Click to expand...

Having learned certain details with trial designs like the -4, the -8 was created to be twice as good. As proof, I offer the opinion of this expert, chosen at random last week during a few hours of horizontal snow in Chattanooga.

All the ugly airplanes were left out to freeze ;)

 
You can say all you want about the -8, at least it is not an -8A which is the Piper Tri-Pacer of the RV fleet!
 
RV-3 Gear

Thank you for all your replies, was seriously considering making some major changes to my 3 build.

Great to learn about Steve Wittman design contributions to aircraft landing gear.

Ordered chrome moly from Aircraft Spruce, for engine mount, this morning and will go with Vans original rod gear design.

Since I will use fuselage fuel tank, did not think it was wise to add stresses to fuselage sides where the tank is supported.
 
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