One-piece Grove Gear - Page 2

billdianne · #11 08-05-2011, 07:46 AM

This was the answer I received in 2007 from Gail at Grove aircraft about a one piece gear. They do require removing the intercostals and the airfoil shape wasn't available then (2007). And I'm sure the price has changed since then.

Hi Bill,
Thanks for your interest in Grove Aircraft landing gear. Yes, we can build
you a one piece RV8 gear. Typically, one piece landing gear are used to
replace a landing gear in an aircraft that has been ground-looped. This
damages the gear towers and the fuselage floor between the towers. We have
had a few people install them as original equipment. The weight is 31 lbs
for the one piece gear. The original steel two-piece gear weighs 44 lbs.
Your cost would be $1,800.00.

The pros are: it saves you 13 lbs in weight and the one piece design does
not put bending loads into the fuselage structure.
The cons are: you have to remove a section of the intercostal bulkhead to
allow the gear to pass across the fuselage. It's not available in an
airfoiled shape. You will need to use the F1 rocket gear leg fairings.

Our lead time is 6-7 weeks after you place your order.

Let us know if you have any other questions.

Sincerely,
Gail B. Austin
Grove Aircraft

Neal@F14 · #12 08-05-2011, 12:42 PM

Quote:

Originally Posted by Toobuilder

Aside from possible protection against ground loop damage, what is the benefit of the single piece? It's more weight, plus you are still stuck with the towers intruding into the cockpit.

A one-piece main gear eliminates having to having to deal with the toe-in/toe-out alignment issues of dual gear legs on the -8. We painstakingly measured, re-measured, and measured again repeated times before drilling, and still were off a bit on the wheel alignment, and had to use various taper shims on the axle mounts to get the wheel alignment straight. It was a pain.

Also it *does* save weight over the stock Vans steel gear legs, since the Grove gear is aluminum.

The towers are still necessary to spread the landing loads around as a taildragger. If you've ever bounced an -8 as badly as I have when learning to land the thing, you're grateful for the towers being part of the airframe

Propilot · #13 08-06-2011, 02:20 PM

]I'm a long way from that stage, but Grove gear is already one of my planned modifications to stock standard kit. Yes, I'd definitely be interested, if the modifications were not too extensive and the people at Van's had no valid objections.

scsmith · #14 08-06-2011, 03:15 PM

One thing you have to remember with one-piece gear is that the center part has to be able to flex up and down a fair bit. I'm not sure if the 1/4" wear plates are thick enough to create enough of a gap between the gear and the inner belly skin? Maybe. I'd ask Grove how much clearance will be needed.
If thicker wear plates are needed, then there is a chance that the gear would extend below the outer belly skin, requiring a bulge in the belly.

Another approach to get some, perhaps enough of the same benefit as the one-piece gear is to make thicker 802-L and 802K Zchannels that span across, connecting the bottoms of the towers.

I brought this subject up a couple of years ago and caused a bit of a stir with a long thread discussion.
I think the thread is called "a tale of two airplanes" and it recounts two real experiences. The RV-8 story is Randy Lervold's, and he was actually lucky that the gear loads in his situation were applied differently and the gear attach bolts failed before the gear tower tore out. So it was relatively easy repair to the longeron area and some new bolts and I think a new skin. Many others are not so lucky.

When I analyzed the gear tower bottom attachment to the fuselage, I found that the bolt pattern through the weldments and into the floor structure will tear through the inner floor and all of the stiffening angles and Zchannels before any other thing fails, so this is the weakest link. IF the Z-channels were made out of 1/8" aluminum, and generously bolted through to the steel weldments, then the Z-channels would pick up the load and carry it across to the other side (similar to what a one-piece gear does, but not as strong obviously). I would also make the fore and aft stiffeners (ribs) at the inboard base of the gear tower thicker, or reinforced with angles so they too could distribute the load better without just tearing out.

I forget the number now, but I calculated the weight addition from these simple reinforcements and it was something like one pound.

This is certainly not as strong as the one-piece gear, but it is a whole lot stronger than the stock structure, and would probably be enough to protect from all but the most violent ground incidents.

billdianne · #15 08-07-2011, 11:24 AM

Steve is correct about the flexing of the center part of the gear. Go to
http://groveaircraft.com/droptest.html#
to see a drop test of a one piece gear.

Also to see the results of a gear crow hopping sideways go to Matt Dralles site.
http://www.mattsrv8.com/Rebuild

Danny7 · #16 08-07-2011, 11:59 AM

i wonder what the weight of Matt dralles plane was at the time of the accident?

the thread Steve Smith mentions above: http://www.vansairforce.com/communit...ad.php?t=42689

SHIPCHIEF · #17 08-07-2011, 12:02 PM

Yikes! Matt's 'crow hop' looks like the fuel tank rib got pulled open at the top.
He didn't mention spilled fuel, but I do wonder about it.

About that Grove Gear Drop Test: The downward deflection of the center section is considerable.
has anyone made a drawing set for this proposed installation on an RV-8 (even as simple as 'pencilled in' on Van's plans?)
Could a flexible bottom cover be attached to allow downward movement at the back when the gear flex pushes on it? Is the monocoque construction of the fuselage going to prevent this?

DanH · #18 08-07-2011, 02:50 PM

The gear in the drop test video is for a side-by side fuselage; long center span, large deflection. A gear for a narrow fuselage would have less deflection. The RV8 application wouldn't have any significant center span deflection.

The typical spring gear is mounted to the longerons only....there's no internal box structures to support the gear, thus only two mount points. We have the boxes and we should use them, meaning four mount points. Given a drop load the gear itself acts the same as with the original two-piece scheme, but side loads are shared across the fuselage.

Alan Carroll · #19 08-07-2011, 05:58 PM

Quote:

Originally Posted by DanH

Many (or most) RV8 ground loop incidents result in damage to the gear tower structures and forward fuselage skins.

I'm curious, does anyone know how many such accidents there have been that ended in fuselage damage? I'm not finding many on the NTSB database when searching RV-8 and either "landing gear" or "ground loop". Matt's and maybe one or two others. Matt's description sounds a bit more energetic than your run-of-the-mill ground loop.

Ironflight · #20 08-07-2011, 08:50 PM

Quote:

Originally Posted by Alan Carroll

I'm curious, does anyone know how many such accidents there have been that ended in fuselage damage? I'm not finding many on the NTSB database when searching RV-8 and either "landing gear" or "ground loop". Matt's and maybe one or two others. Matt's description sounds a bit more energetic than your run-of-the-mill ground loop.

It's not that it is common at all, but there have been a number of them - I can think of Randy Lervold's incident, and Senator Inhofe's. If you let the little wheel try to get out ahead of the big wheels while going fast, you might just start a slide - at least that is how I read it.

Good news isn't news - you only hear of the bad landings!

Paul