Landing gear safety cables

[herman pahls 9]

Are the Kitfox and Avid landing Gear safety cables an asset or liability?

When metal hits metal things bend or break.

After 18 years of not having to weld on  my Kitfox,  I bent the bungee truss under the seat.

The gear legs and longerons were unharmed and I was able to fly it back.

Joey told me that he has removed the safety cables on his Avid for this very reason.

I mention this only for other Avid and Fox owners to consider to hopefully prevent what happened to me

I do not like flying without Safety cables even though I have not had a bungee fail.

If going with safety cables again, I would make them as long as possible to keep the airframe out of the dirt (maybe not the prop) or how about a second set of bungees wrapped loose over the primary bungees to act as a progressive suspension and act as a safety ?

 

TIME TO GET THE SAWZALL, TORCH, GRINDER AND WELDER OUT

 

 

Awhile back I asked about Grove gear. Is it time for grove gear?

Thanks Herman

 

 

 

[wypaul 448]

Herman I don't know if you noticed this on the Yahoo site but it looked interesting as an alternative to the cables.
This is message 36437 on the Yahoo site

Those comments on the wire as too hard a stop, the proposal of an additional bungee-cord loop with a stronger cord, that all is quite interesting An idea I am elaborating is to make an additional bungee loop but one that ties horizontally both landing legs just below the cockpit floor. The good thing about that is that with usual, not to big inflexions of the landing gear, that bungee loop nearly does not get extended atall, this, is, it makes almost no additional force even if that bungee cord is very strong. Only when the deflection is quite important the bungee starts to work but very progressively, linearly. I have written down the equations that describe the force delivered by this proposed bungee of mine and I am analyzing the way it works a bit closer and hope to be able to give a quantitaive description in two or three days. This notice today is just to hear if someone has implemented such an idea before and if yes, to hear what his
experiences have been with it.

Cheers Juan

 

Something to consider perhaps.  I am using the HighWing Bush Gear and am happy with that after a little work to the truss and fuselage sides to beef them up.

 

Here is a better explanation in message 36444:

 

In that question of protecting the fuselage of he Avid against damage at hard landings there has been made the proposal of replacing the security wire loop and also the proposal of substituting it by a loose loop of a much stronger bungee cord. This proposal makes at first sense but I fear that in reality it will be very difficult to find and install bungee material suitable for the task.
My proposal is a different one: remove that wire loops and add to the landing gear an additional "suspension mechanism" in this way: install loops of bungee cord placed horizontally below the cockpit floor, each loop passing through the space delimited by the horizontal tube of each landing leg and the stiffener running down, this is tying both landing legs together.
I have written down the equations describing the behavior of such a suspension. The results are described with the attached graphs. In those graphs the X coordinates is the deflection of the landing gear given in degrees. The Y ordinate is the vertical force ("weight") on the landing gear originating this amount of deflection. The redline is the relationship between force and deflection with the standard Avid landing gear installation. The black line is the additional effect of my proposed mechanism. The blue line gives the result of combining the two suspension loops.
There are two graphs the photos of them I have posted to the Group in a file "Ne Suspension mechanism". The one where the lines run more horizontal, this is, where the suspension is softer, corresponds to adding "my" loops having the same elastic values as the standard bungee cord loops. The other graph corresponds to adding "my" bungee loops with stiffness 3 times higher than that of the standard bungee cord.
The interesting thing is that "my loops" do not appreciably contribute to the suspension below 15° deflection. Beyond that point they progressively contribute to stiffening the suspension. A very positive point, I think, is that the elastic properties of "my loops" can easily be adapted by just adding loops as needed or considered convenient. Last not least is is a very positive point that the force created by "my loops" is a compression force on the stiffener of the cockpit floor. This means the bending forces on the stiffener remain as before, the new mechanism charges on the same stiffener but with forces running otherwise. In total the stiffener is charged in a more convenient way, less prone to damage it.

Edited 31 Oct 2013 by Paul S

[Av8r3400 1179]

When I had to fix my truss, I took the down time to switch to Grove, and never looked back. Far superior in every aspect. Overall weight gain was 12#. I took that as a hint to loose this weight off my fat ass.

I also upgraded to Grove wheels and brakes which are also head and shoulders better than the cobbled ATV wheel and Matco brake garbage that came on the plane. Now I even have brakes that will stop the plane!

[herman pahls 9]

Paul thanks for sharing the Yahoo messages regarding alternate bungee backups and 

Av8r3400 with the real world Grove weight increase.

I was told about Airdale's swept forward aluminum gear that is available for Avids that would work for a model 2 since I do not have the forward float attach points  for the grove gear like model 4's have.

Any body have experience with the Airdale swept forward gear?

I contacted Grove with measurements and they are working up a bid for a custom swept forward gear for my model 2.

Grove told me they are not excited about how much forward sweep is required and will the longerons handle the the loads.

Has any one on this forum welded on forward float attach points and the fuselage reinforcement bracing that would be required?

My stock model 2 gear places the axle 2.5 inches forward of the forward attach point as it is.

Herman

[EDMO 1078]

Paul,

Can you also post the drawings he referred to on the Yahoo site - My old mind tried its best to figure out what he was describing on the horizontal bungees, but the hookup remains a mystery to me.

Thanks,

EDMO

[wypaul 448]

Ed, not sure how to get the photo from the photo section on Yahoo.

]http://groups.yahoo.com/neo/groups/avid_flyer/photos/albums

This one works for me, hope it does the job for you Ed.

Edited 1 Nov 2013 by Paul S

[EDMO 1078]

Ed, not sure how to get the photo from the photo section on Yahoo.

file:///C:/neo/groups/avid_flyer/photos/albums/179580173/lightbox/382410459

 

This link is the best I can do but you will probably need to be a member of the Yahoo Avid site to follow the link.

 

 

Ok, that did not work but if you are a member over there you can go look in the photos section.  Maybe somebody knows how to get photos from the new Yahoo site but appears over my head.

 

One more try:

 

http://groups.yahoo.com/neo/groups/avid_flyer/photos/albums

 

This one works for me, hope it does the job for you Ed.

It sure didn't work for me - I am not a member - Just an old clutz on the puter - maybe some young mind can find it and post it. Been thru 32 oz of Michelob - out of Bud Lite - and still cant get beyond "horizontal", which I understand is not "vertical", but cant for the life of me, figure out how in hell he attaches these stronger bungees. I have the Grove gear, so don't really need it - but it is something that I don't understand, and that is frustrating - and I might want to pass it on someday.

Thanks,

EDMO

[Av8r3400 1179]

Ed - I prefer Kessler and diet Coke...

 

 

My buddy used the Grove gear on his C model Avid fuselage.

 

 

 

I don't know if this will work on you fuselage, but he sure loves it.  Far and away better than the oem or the Airdale "bush" gear that he bent.  This is a custom set from Grove, 3" taller.

 

[EDMO 1078]

Ed - I prefer Kessler and diet Coke...

 

 

My buddy used the Grove gear on his C model Avid fuselage.

 

IMG_0700.JPG

 

 

I don't know if this will work on you fuselage, but he sure loves it.  Far and away better than the oem or the Airdale "bush" gear that he bent.  This is a custom set from Grove, 3" taller.

My gear is no problem - Got Kitfox 7 Grove with nosegear - Just cant follow the attachment using the stronger bungees as a substitute for the cables on the regular gear - Just bugs me when I don't understand something - might even drive me to drink - or is that, drink to drive? No-No!

EDMO

[herman pahls 9]

Av8r3400

Would I be able to get contact info. for your friend with the Model C Avid to find out what he went thru to get Grove gear.

You friends swept forward gear looks like it would be what I need without having to weld on forward float fittings.

I am curious when Grove made that gear for him because  they act like this is a new idea, not usually done and I would have to manufacture my own attach brackets.

Thanks  Herman   Oregon   541 404 6464

[Av8r3400 1179]

He took delivery of the gear about 2 months ago.  It is brand new.

 

It is the Avid Mark IV gear with the extra height added.  Listed here.  He requested the additional length.  Not a big deal.

 

What model is your Kitfox?

[herman pahls 9]

I have a model 2 Kitfox.

I will refer to your friends Avid gear when I call Grove.

I was under the impression that the gear attach points on the early Avids and Fox's were the same.

If that is true, maybe Grove does not know that and that is why they say I need a custom gear and I need to make my own attachment blocks.

[Trackwelder 12]

The Kitfox and the Avid gear are not the same, but 5 minutes with a file will make that change, up until model % I believe they are almost identical fuselages, There are several ways to strengthen the seat truss that Steve Winder had described, the easiest is to use an Epoxy ( he used Hysol 4130 I believe as hat is what Kitfox sells) and glue little triangles into the seat truss. If I was doing a complete teardown I might think about welding in 4130 plate, nothing any bigger than .062.

[herman pahls 9]

I measured an Avid Mark 4 and an Avid Model C today and you are correct, the gear attach points on the longerons are almost Identical to within a 1/16" of my Model 2 Kitfox or less and could be adjusted with a file.

All 3 aircraft are within a 1/2" of axle placement in relation to the leading edge of the wing when the fuselage lower longerons are level as when doing C. of G. calculations.

Av8r3400 said his friend recently ordered a swept forward gear for his Model C Avid, which according to Trackwelder and my measurements should fit the early Kitfox's that do not have the forward float attach points.

According to Grove's website, their Avid Mark 4 TD gear costs $300. more and weighs 8 pounds more than a Model 3-4 gear.

The reason for the increased weight is the extra material needed for the forward swept feature of the gear and that it is 5" instead of 4" wide where it clamps to the attachment brackets.

Av8r3400 said the Grove gear on his Model 4 increase  his empty weight 12 pounds over the stock bungee gear which I could live with.

Since my Kitfox would require the swept forward gear, the weight increase would approach 20 pounds which I do not think I can live with.

Thanks for all the comments to help me come to a conclusion.

 

Where do I find Steve Winder's posts on how to reinforce the seat-bungee truss?

 

Thanks  Herman

Edited 4 Nov 2013 by herman pahls

[Av8r3400 1179]

There's nothing high tech about the reinforcement.

You just cut triangles from plywood and hysol them onto the openings in the truss. Make note of where the bungees pass through and don't fill in those openings.

[wypaul 448]

Another weak point that needs a triangle is horizontal on the lower longeron and just ahead of the seat truss under the floor boards. My MK IV has a triangle formed by tubes at that point that I filled with plywood after repairing the structure there.

Edited 5 Nov 2013 by Paul S

[Trackwelder 12]

Thanks for that bit of info Paul We as in those who actually have a plane flying are pushing the limits as to how far these planes were designed to ggo and how far they make it. For a design that was built 30 years ago and meant to get people flying cheap while landing on a grass strip, it is amazing how far we have taken them. I went through the other group and wrote down all of the modifications Steve Winder put down and with those I was able to upgrade my fuselage to Mark IV specifications with the B model width and then made my own copy of Merle Williams fuselage widening kit. I have been meaning to write them down here, At the same time I have been looking at the damage done to the planes and re-engineering a few things, I have an I dea on the bush gear to put the strength in that it needs, But I need to Know what size tubing the gear is made out of,and preferably how hard the landing was that caused the damage. I have priced out 18 inch travel Rok Shocks and have an idea there, but I need to know what the weight comes to, designing it as a bolt on could be a bear butsince there is no fabric around that area of the plane It should be do=able with minimal welding, Now I just have to look at Steve Winders Numbers again.

    The gear I dsigned for my own kept the same positioning back from the leading edge, but went out 14 inches wider and 8 inches taller, those he had put tubing specs down for, now its on to uncharted territory, and money, The one thing I Know is that up to the Highlander, they used the same 2 1/2 by .063 tubing for the spars and were willing to sell the inserts at a reasonable price. I used 1/4 inch plywood in mine figuring the original load test was done without anything in it. I should have kept building but at the time I was looking for a 2 place airplane and had some weight to lose, now 210 lbs lighter The Avid Became a 2 person plane even if I had not made any modifications.