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Wheel penetration skiis

RF ski update. Parts received from Europe. More bent rod ends found on a Cub, after previously replacing bent rod ends.

Right now, we are stuck at step one of the recognized ten step process for solving these sort of problems.
 
George,

I have never seen these skis in life, nor have I watched them work... but I thought of this looking at the pics you sent:

First: are you or anyone putting skis down while on the ground, thereby stressing the little hydraulic ram? (it may say it can do it, but that ram is little).

Second: the connection between the ram and the black mount has a slide slot cut in it... my guess is it needs that for an 'over cam' situation. If so I would take a guess that you might have a couple of issues happening- the slot if warm will build ice inside, restricting movement, (pull out of hanger, fly in warm weather, low alt warm to glacier landing) or flying in overflow you can build ice inside; the other would be building snow/ice under or around the ram so it's movement is restricted.

Third: the slit/bolt set up if not connected with a really good bearing surface will tend to bind, even if you think you have grease (grease collects water-see above) If it were my set up I would want some sort of UHMW bushing that would be slippery no matter what, and change it out every 100 hours... That slot is very small for the conditions you are asking it to work in...

Again, I am just looking and thinking about some of the machine issues I have had with hydraulics over stressing the equipment around it, or destroying itself.

One quick check is to see if the slot is bearing surface smooth and flat or has gouges or bumps. If not smooth and flat that would indicate a problem

Good luck, and keep us informed.
 
Ok, looked again...

Are the rod ends torquing up and down?

These look just like the ones we use on sleds for steering... POS!

My bet you could go to the sled shop and get new ones today....

But,

It is a weak link, do they need to have a complete swivel? I would think that it only needs to rotate around the fittings, making the whole rod end idea obsolete...

But if you must use them, build a block to thread the rod end through and contacts tightly to both the arm and around the circular part of the rod end. Doing adjustments suck, (bench grinder) but it supports the ends.

a 1/2" or even 9/16" bolt was not made to take a 2,000 lb plane laying on the end with 2-3" arm out!

I would build a torque block with a bushing that bolts to the arm...

I can build you some this week if you send size.
 
Aktango, the molded carbon fiber retract arms on those skis are a thing of intense beauty. It's not likely that George or these other guys will bolt up an Alaskan-rigged solution to their very nice and expensive skis, unless it is condoned by the ski manufacturer.

The rod-ends are an Airbus part, so they oughtta have some QC in place and the system should be designed so they are able to take the loads.

My guess at the failure mode is this: When the wheel retracts, the tire is being pressed against the retract arm, actually it is being squeezed, HARD. This is a fact from my observation of the skis in operation. I can imagine that the force of the tire pressure, which in the geometry of this system INCREASES when you land and put weight on the skis..............the force of the tire is caused by the retract arm and is 90 degrees to the rod-end shank. I can see this force breaking the rod-ends. I can see this as the cause. However, I did not inspect the broken rod-ends, and don't know the actual failure "direction". I am not involved in installing or rigging these skis, but was present at various stages of the installation on an A-1B.

Maybe George M. will let us in on the direction of rod-end failure. Bummer for sure, as good ski-flying is to be had if the temp's here raise another 10 or 20 or 30 degrees F.

DAVE
 
We have three different maintenance guys working on this, and bent rod ends on each of the three planes with the skis, including repeated failures on the same plane. This is with just a few hours, flown light, and in very benign snow conditions. There is no one thing we can identify as causing the problem -- basically the rigging right now isn't strong enough to stand-up to long term use.

The skis are absolutely beautiful, have fantastic wheel clearance, are lightweight, and as Mike V reported previously, perform great. That said, the rigging is more like what you would expect on an experimental, and since a product is only as good as its weakest part, we need to get support from the manufacturer to redesign the rigging. That is what I was referring to as hung up at step one in the ten step process -- and step one is admit we have a problem. If we can resolve this, and we certainly want to, this will be a fantastic ski that will be very successful in Alaska.
 
Dave,

I will bet that the rod ends, airbus or Polaris, are made the same, with same QC. Bottom line is that they were never designed to hold 1,000 each 90 degrees in shear, then have them sticking out for a lever to bend!


As far as an "Alaskan-rigged solution", seems most of the planes people on this site own have thoes: removable seat bar, extended baggage, HD gear, Extended Gear, boer prop....

But because I suspect that you are referring to a cut to shape, beat to size, shim to fit.... check out my photo album and see my project I just finished- a tool specifically made for producing some parts I need!

George,

If you have one good rod end, mount it in a steel block and do a pull/push test in a press and see just how much pressure the thing will hold in truth :oops:

my bet if you tied a Husky down with the plane's weight in shear on these' they would bend in a wind storm...

But I am far away and taking wild guesses.

Keep us informed!
 
George,

Sorry, but there is nothing wrong with the SKI rigging that I ever saw. As I noted earlier, I put a lot of hours on a set of these skis in northern Alaska, and in VERY deep snow at times. We also had the airplane on McKinley with the skis. Those skis have been beat around a good bit, and they have not had problems with them at all. They work.

Furthermore, there are a number of sets of these skis flying regularly, for several years, in Europe, on Huskys, Super Cubs and other aircraft.

When we put the skis on our Husky, we changed to the Aviat "ski landing gear", which was designed for the Aero 2800 skis. That's what Thomas is using in Europe as well. Have you considered that the reason you folks are experiencing failures is the attach hardware you're using?

It seems the only failures on these skis noted to date is where they are being mounted to aircraft with ATTACH fittings made and installed locally in your part of the world. What you have described SOUNDS like an alignment problem to me. That is, alignment of the attach points, not the ski actuators.

But, I may be waaaayyyy off. It's hard to visualize these mechanisms remotely.

In any case, I can tell you that while the attach mechanism on those skis does LOOK a little light, it can and will take a beating. I've turned those things around in very deep snow really tight, and nary a whimper.

I hope you get this figured out soon. Good luck.

MTV
 
All good points Mike,

Did your skis use the same rod ends? If so, I want some for my sled's steering!

I would bet with all of us where the planes are, and three cases of beer, a bunch of stakes on the Barby we could get this sorted out after the third beer run! :wink:
 
Tango, I meant no intent against your jury-rigging skills :D

What I meant is that we are talking about a very expensive European-manufactured product, the designer of which is unlikely to 'approve' what the best engineers on the West coast or "North coast" of america (lower-case 'A' for european-snobbery-effect) are able to conjure. Notice that George M. said that first we have to admit there is a problem? I'm sure the manufacturer is as bummed as George that all is not in gleaming perfection. I hope this is quickly resolved.

Mike V., were you guys running the carbon-fiber arms?
 
No offence taken Dave! :drinking:


usually I defer to the guys that really know what is going on in my plane. But when it comes to hydraulics and linkage breaking, I take great glee in finding the trouble, call it a mental defect! :p

If the units are the same as Mike used, I would guess that alignment is the problem. If ANYTHING has changed.... you know the drill.

I do have a hard time believing that those little rod ends hold a plane!

Another thought- could the tires have a different depth of tread causing more pressure?

well, off to the shop now, have more parts to build.... Need anyting? :lol:
 
I was wrong about the failure mode having anything to do with the squishing of the tire.

Apparently the failure is occurring as the a/c is being raised from wheel to ski. At that point the weight of the a/c is supported on the shank of the rod-end at about a 90 degree angle and the rod-ends aren't up to it. One of the failures occurred in the hangar during a retract test. Yikes!

Mike, one of these sets is on an A-1B with an "Aero-gear" as manufactured by F.Atlee Dodge. I'd be surprised if Atlee's screwed up all the bracket/tab/stub fabrication. Mystery's!

DAVE
 
Landis Airglass was sold a few months back to the "son" of Northrim Bank.

I've talked to the new owner and he is moving forward as fast as he can with an LW-3000 version (for Cubs and Huskys) of their Cessna 180/185 LW-4000.

Hands down, the LW-4000 is THE ski to have on a C180/185 or Found Bush Hawk.

In the future I feel the LW-3000 will do the same thing to the Cub/Husky ski market.

Talk is of the ram being electric, so no hydraulic pump and plumbing.... wouldn't that be nice.

Crash
 
Dave Calkins said:
I was wrong about the failure mode having anything to do with the squishing of the tire.

Apparently the failure is occurring as the a/c is being raised from wheel to ski. At that point the weight of the a/c is supported on the shank of the rod-end at about a 90 degree angle and the rod-ends aren't up to it. One of the failures occurred in the hangar during a retract test. Yikes!

Mike, one of these sets is on an A-1B with an "Aero-gear" as manufactured by F.Atlee Dodge. I'd be surprised if Atlee's screwed up all the bracket/tab/stub fabrication. Mystery's!

DAVE

This would suggest to me that the skis where designed to be re-postioned in flight only !! ??
 
irishfield said:
This would suggest to me that the skis where designed to be re-postioned in flight only !! ??

Apparently these same a/c have not had failures when retracting/extending in the air only. D
 
Have a bad feeling that's the intent. So many figure the guy wants to leave pavement.. go play in the snow and come back to pavement.

Not the real world of wanting to roll out of the hangar to snow... reposition.. up over the snow bank and go play. Come back.. slide over the snow bank and reposition wheels down.

I don't think you're supposed to repositon AWB's on the ground either are you?
 
Dave, we only cycled our skis in the air, and ended up with a bent rod end.

Mike, Atlee Dodge welded the tabs on one Cub and the Husky, and our installer did our tabs on Cub/AO gear. He is the same person that did STC one of the AO gear on the Husky, and absolutely knows what he is doing. Out of curiosity, did you ever pull your rod ends and check them to see if they were bent? Are those skis still flying? Are you aware of any other sets of those skis flying in Alaska that would represent another data point on durability?

We love the skis and hope to resolve this soon. We are working with the manufacturer on a fix.

Crash, compared to the LH-4000 skis, these have MUCH more ground clearance when taxiing -- important on rough gravel strips.
 
George,

I'll call my previous cohorts in crime fighting who are still flying the skis today. We did inspect the rod ends pretty closely, at re-installation time, and of course, at least "casually" during preflights. This airplane lived in a heated, well lighted hangar, so pre-flights were pretty thorough.

I never cycled the skis on the ground. Never needed to, and I've always felt that doing so on ANY set of skis imparts a lot of stress, so generally avoid it, approved or not.

There is another set of these skis operating on a Cessna 180 in the ANC or MatSu area. This set was field approved on an airplane owned by a FSDO inspector, but I don't know his name. If there were ever a test for those skis, the much heavier 180 would offer it, so I'd try to track that airplane down. I vaguely recall someone saying that airplane was either for sale or had been sold recently.

I'd check with the ANC FSDO, and see if they know who that Inspector is. As I said, I don't know who that was, so have no idea if they had any problems or if they ever actually used the skis....

Thomas can give you the name of the fellow who did the certification tests in the US on the Husky. He's in Wisconson, and I'm told has a set of the skis on his airplane now. I'm guessing he used the Aviat ski gear as well.

This is a real bummer. These are such great skis, I really hope there isn't some sort of unresolvable problem here.

Crash, its good to hear that Landes is in the hands of someone who cares about skis. I was really afraid that the company would go to some big outfit that just wanted the military contracts, and would tube the GA stuff.

No doubt, Landes makes great stuff. I hope they get the Cub ski going.

MTV
 
RF8001 Skis

Hi, for those of you, who do not know me, I am Thomas and I designed the RF8001 Skis.

We have been producing these skis since 1994. Never had a problem with the rodends. After hearing about the problem, we could identify, that all the rods in question were form the same batch. My guess was, maybe a soft batch, but the rod end manufacturer looked at the rodends in Question and said" everything normal ".

I then hat to analize why the rods fail or bend, when the aircraft is just pumped once or twice on the ground. With the statement of the manufacturer to have" ok Rodends", we had to look for another reason.
I successfully could damage a rodend by pulling the skis way to high when hooking up the bungees.

But some after market Brackets did not have the stop, that is needed to restrict the travel of the rodend, and these gears still had failures.

I still was sure to have a batch of soft rodends.
We had to build a test rig to test the rodend ourselves. The batch in question met the specs of the manufacturer, but other batches were 30% and more stronger that the specs called out.

To have the airplanes flying again, we shipped from the stronger batch ends out. In the meantime a solution got developed that cold be retrofit on the existing carbon yolkes.

These tests were finished on Jan 9th with the questioned batch of rodends. Even with these rodends the required forces could be now far exceeded.. Lifting of a 2700 lbs load creates no problem. On a single rodend. Beforethe mod, bending happened at around 800 lbs.

Parts for this mod will be shipped Jan 14th. Installation of the mod takes 12 minutes.
Cycling a Turbine Bird Dog ( SM1019A) fully tanked at 3700 lbs for 100 cycles showed no bends at all.

We will supply all our customers with a free set of parts , regardless how old the skis are.

I am sure that this problem is solved now and for the future.


TomD :D
 
Wow.
Now that's customer service/care.

Good on you, TomD, I'm sure your biz will thrive (IF you survive this rod replacement) :)

Good to see some caring in biz.
 
GeorgeMandes said:
Crash, compared to the LH-4000 skis, these have MUCH more ground clearance when taxiing -- important on rough gravel strips.

George, where are you landing on rough gravel strips in the dead of winter?

I log 100+ hours each year, flying the Iditarod using a set of LH-4000's. We land on all kinds of terrain during the race including gravel strips. I've yet to replace the ski tail wear strips. I don't see it as an issue unless you're landing on real rough gravel and most of that is buried under snow or should be....

Take care.

Crash
 
Crash - - the issue on gravel is the ski tailwheel throws rocks into the tail feathers. If you're not having that problem, I dunno.

RK
 
Not really having tail feather problems from the skis throwing rocks. I guess we're operating in different areas of the state. From Willow to the Yukon you can operate pretty well with just straight skis.

The coast (Unalakleet and up) is another story. I would guess about 80% of the ops are done on gravel strips with 1 1/2" and under rocks. They (LH-4000's) make a lot of noise but after the end of the season I'm always surprised when I take the skis off that there is very little damage to the tails.

I go skis to wheels, wheels to skis all day long on the ground, no problem! Even go one wheel down, one wheel up to turn around on the ground. I usually never even get out when I blow it and end up off the runway, out in the bushes. Just drop a wheel, roll the trim forward and put the pedal to the metal....

Take care.

Crash
 
We have LH-4000 skis on our 185, and Landes wheel penetration skis on a Husky. Fine products from a fine company. We hope they get their LH-3000 completed for the Cub/Husky soon as more choices is a good thing.

When you taxi on the RF skis, there is so much ground clearance that you would never know you are on skis. On both types of Landes skis, we clatter around, even on pavement. I can't imagine that anyone designing skis on a "clean sheet of paper" would prefer the ground clearance of the Landes skis over the RF?
 
George,

Tried to get in touch with my former cohorts yesterday. No luck. Cold in FAI, and I'm guessing they're all kegged up at home.

I'll keep trying to get in touch.

MTV
 
Gravel / skisGeorge

George,

if gravel pickup is an issue with RF skis, there is a simple solution to it.
A rubber guard can be mounted just behind the wheel opening. It is a rubber as used on engine bafflings.

I have such a rubber integrated in my mudguards/ wheel pants for the Rfs.

This rubber extends downwards to the ground. On gravel it will get used and needs replacement from time to time.

On snow it will fold back from the friction. Weight increase on both skis less than 1 lb.

TomD

 
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