Spring Landing Gear

[SWeidemann]

Spring gear questions:

On a technical matter, the Kitfox Model 5 Vixen I just bought is equipped with what I believe is a Grove main gear (on this tricycle gear only version). Upon closer inspection I discovered the main single leaf gear has somehow moved all the way to one side of the mounting blocks. I know the current model Kitfox has 2 pins inserted on the inside of each horizontal piece of the gear to keep the gear centered and prevent any shifting sideways (4 pins altogether).

I have loosened the mounting block bolts, moved and centered the gear (visually) followed by tightening the block bolts. In looking in the area where the pins should be there do not appear to be any holes for such pins.

Is this setup safe for operation as it is now, and if not, is there a way to either have the stop pins installed on this gear or is there another acceptable method to prevent the gear leaf from shifting sideways?

Thanks much,

Skot

[SkySteve]

Skot,
My Grove gear does not have the pin holes. When the attach side bars are tightened properly I have never had a problem with side movement (slippage) of the main gear.

[cubtractor]

My gear has roll pins on each side just inboard of the gear mounts.

[DesertFox4]

My gear has roll pins on each side just inboard of the gear mounts.

My model 4 also has these pins.

[Av8r3400]

The older gear springs do not have the roll pins. The newer springs do.

When speaking with Grove about retrofitting an older spring, they suggested that these (1/4" x 1" ?) be installed by drilling the spring and pressing in locally sourced pins.

If your gear is slipping again after this readjustment, this may be something you would want to do.

[SWeidemann]

In communicating with a young lady at Grove, she came up with the conclusion my gear was made by Hammerhead. She said all Grove gear has the pins. At any rate, my intent is to get my hands on a set of roll pins, drill the holes and put them in.

Skot

[SWeidemann]

After jacking up fuselage, loosening the gear blocks, centering the gear and tightening the blocks, I went for a ride. As before, the gear spring again shifted sideways.

My intent is to install the roll pins. My question is: Should I remove the gear and take it to a machine shop for drilling & install of the roll pins or can I use a hand drill to make the holes for the roll pins? I want to do it right. Any opinions?

Thanks much, Skot



The older gear springs do not have the roll pins. The newer springs do.

When speaking with Grove about retrofitting an older spring, they suggested that these (1/4" x 1" ?) be installed by drilling the spring and pressing in locally sourced pins.

If your gear is slipping again after this readjustment, this may be something you would want to do.

[SkyPirate]

If you have the gun drilled lines for your brakes, do it on the opposite side of the fittings for brake lines :)

[napierm]

At a minimum, I would support the gear in a drill vise and carefully mark and drill the holes that way. Start with a smaller pilot drill and work your way up. Don't do it by hand.

Having said that, I can also say that sometimes despite all my efforts a drill will still sometimes wander off center. Even a pilot hole may not be enough if the drill finds some "grain" in the metal. When I drilled the gear legs for my BD-4 I made a jig out of steel and then used the jig to drill the holes. Even then the holes needed some light reaming to get all four bolts through.

If you have any doubts, let a good shop do it.

FWIW,

Mark Napier

[SWeidemann]

I had thought about drilling into the gun drilled channel by mistake, but I notice that all the new gear (looked at several at Oshkosh) and found they have roll pins on both sides (front and back) of each side of the flat gear. So...I assume the drilled hole is not near the brake line hole, just how far away?


If you have the gun drilled lines for your brakes, do it on the opposite side of the fittings for brake lines :)

[SWeidemann]

I like the advice about taking the gear to a good machine shop to do a straight hole. Question is however, just how far away from the edge is the gun drilled brake line channel?


At a minimum, I would support the gear in a drill vise and carefully mark and drill the holes that way. Start with a smaller pilot drill and work your way up. Don't do it by hand.

Having said that, I can also say that sometimes despite all my efforts a drill will still sometimes wander off center. Even a pilot hole may not be enough if the drill finds some "grain" in the metal. When I drilled the gear legs for my BD-4 I made a jig out of steel and then used the jig to drill the holes. Even then the holes needed some light reaming to get all four bolts through.

If you have any doubts, let a good shop do it.

FWIW,

Mark Napier

[SkyPirate]

Without actually seeing it i would put them inboard close to the inboard side of gear bolt

[SkyPirate]

Center your gear, take a 5/16" center punch put it right up against the inboard side of bolt, center up and down an set a dimple, if you use a 1/4" center punch, i would think it would be too tight and flex in the gear would eventually bend the dowel pin and wear on the bolt

[SkyPirate]

Again without looking, if it is gundrilled, there should be a hex bung on the very bottom of the gear leg, check its orientaion if its centered or more toward front or back, the gear is tappered, evenly tappered bothe front and back or straight front and tappered back, if its evenly tappered, measure to center of hex bung plug, from the opposite side of brake lines, then measure width at bottom front to rear, then measure widest part of gear at fuselage front to back, check difference on opposite side of gun drill

[SkyPirate]

If your taking the gear completely off you can remove the brake fittings and check depth of holes under the fuselage, subtract that from width of gear, you should have plenty of room to put a 1/2 deep hole on the opposite side but better safe the sorry :)

[SWeidemann]

Excellent suggestion. Thanks


If your taking the gear completely off you can remove the brake fittings and check depth of holes under the fuselage, subtract that from width of gear, you should have plenty of room to put a 1/2 deep hole on the opposite side but better safe the sorry :)

[HighWing]

I had Hammerhead gear on my first Model IV. Check the bottom of the gear leg. there should be a fitting or plug where the drill entered. If the hole is centered on the bottom it should be centered through the leg. They are drilled in a fixture before bending much like center drilling on a lathe. After drilling for the brake line, the gear leg is bent and then heat treated.

Another thought. Where you will be drilling is a high stress area on the gear leg. Don't drill too deep.

[SWeidemann]

I was told by a staffer at Grove that my gear is a Hammerhead because all Grove gear has drilled holes with pins. Apparently Hammerhead was an earlier supplier.

Skot


I had Hammerhead gear on my first Model IV. Check the bottom of the gear leg. there should be a fitting or plug where the drill entered. If the hole is centered on the bottom it should be centered through the leg. They are drilled in a fixture before bending much like center drilling on a lathe. After drilling for the brake line, the gear leg is bent and then heat treated.

Another thought. Where you will be drilling is a high stress area on the gear leg. Don't drill too deep.

[Av8r3400]

I just sold my early, non drilled, Grove gear to another member on this board. They did make them that way.

[desertfox1]

I'm a little confused, are we talking about gun drilling for the
brake line or hole drilling for the locator roll pins?

Phil

[SkyPirate]

Drilling for the roll pins but avoiding the gun drilled part of the gear :)

[HighWing]

I was told by a staffer at Grove that my gear is a Hammerhead because all Grove gear has drilled holes with pins. Apparently Hammerhead was an earlier supplier.

My first Model IV changed over to Hammerhead gear in 2000 after about 200 hours from the original bungee gear. The gear did have the roll pins (See attachment).

A brief history as far as I recall. Two guys started Grove - much like the two guys who started Kitfox. Then much the same, the two guys decided they had different ideas as to which way the company should go - or something. The guy that split off (Hammerhead) was the developer of the gun drilling method and machinery. The reason I went with Hammerhead was that the gun drilling came standard with the gear whereas Grove charged extra. Again, much like Kitfox/Avid, Grove survived for the long term while Hammerhead ceased operations several years after the split.

Early on the alloys were different as well. Hammerhead used the 7075-T6 where Grove used a different alloy - not sure which one, but Grove would repair and re-heat treat the softer alloy at no charge for a while. That service was not provided by Hammerhead, but 7075-T6 is almost impossible to bend in the T6 condition. For some time now Grove has gone to the 7075-T6 exclusively.

[mr bill]

Aluminum alloys can be bent, using appropriate bend radii for that alloy, it's temper and it's thickness, without cracking, assuming all bends are across the grain of the metal and depending how new the metal is. Freshly quenched can be bent using a shorter bend radius, but as the metal ages, it hardens and requires a larger bend radius. 7075-T6 or 2024-T3 would require a very large bend radius (for a landing gear, it would be measured in many inches).

[SkyPirate]

I think grove manipulates the gear before heat treating to T-6 specs,..for spring gear it's a slower cooling process then for hardening, not sure on a quenching sequence,,it's been too long since I messed with that part of it..

if I remember right you can bend it prior to heat treat up to 80% of material thickness for Radius so minimum would be 1.25"R on anything from .375 .. to 1" I forget the formula for larger then 1" thick
.375x100/80%=1.25"
.875x100/80%=1.25"
less then 3/8" -.375 can be 100% thickness at Radius

or do I have that backwards bill?

ok I just remembered..it's been way too long since I messed with forming larger metals..you add 80% of the thickness to the length of the blank to get the right dimension after the bend..

proof that if you don't use it you loose it :)

[SWeidemann]

Another thing about my gear is that it is held in place with rectangular shaped blocks that do not look anything like the units in the build manual.(Drawing shows an assembly that includes round gear rocker disks...not mine.)

Skot


In communicating with a young lady at Grove, she came up with the conclusion my gear was made by Hammerhead. She said all Grove gear has the pins. At any rate, my intent is to get my hands on a set of roll pins, drill the holes and put them in.

St

[mr bill]

In the case of 7075 alloy, bent in the 0 condition 1/2" thick (90 degrees) requires a bend radius of 4 times thickness. In the T6 condition it requires 10 times the thickness. Heat treat after forming may not be practical for large parts like landing gears. Bend radius of 45 degree bends can be significantly smaller.

[SkyPirate]

yes that's it Bill,..I was figuring 45 degrees or less,..and using at least a 6" bottom die and a round nosed upper die at least 2" on upper