Main gear tab thickness

[Phil Kriley]

I just did the outside portion of the tabs, and I used 1/2" spacers before clamping a board across them. When I removed the clamps, I was surprised to find that the board did not touch the tabs...? On one tab, there is an area about the size of a quarter that is flat - it is apparently the only tab that actually touched the clamped board.

 

I searched the archives and found that one writer had calculated .485" as the thickness for the outside layup - and I'd have to say that that is almost exactly what I wound up with - just shy of 1/2". So - I guess I'm OK?

[steve]

i have the same thing going on, i had a 1/2" wide tab and i put the tube inside the two tabs getting ready to do the last 2 layups(2bidover washers)(2bidover the tube) but the tube was to long ??? so i when back to look for my sharpy dots in the reading and there where no dots put next to "now add 20 layers outside and 25 layers inside over the 50 you just did"

shoot, now the tube is fine and glassed in and main is back in the plane and is very close in toe (1/16" from Axel to tip-of bl -0) both sides.

i just got my studs in the mail and need to ask.....there is a space in the bulk head (1/8-1/4) where the gear fits in. do i shim with a washer or did i miss some layups in the landing-gear-bulkhead ?

[Big Steve]

Steve

 

Mine fit pretty darn tight without any shims. Just bushing against bushing. I got the feeling you missed some layups.

 

STeve building on

[Phil Kriley]

Steve

 

Mine fit pretty darn tight without any shims. Just bushing against bushing. I got the feeling you missed some layups.

 

STeve building on

I had to put in a washer on each side, and I did not miss any layups.

[argoldman]

I had to put in a washer on each side, and I did not miss any layups.

 

The gear tab layups are massive layups and their ultimate thickness is dependent on the glass to resin ratio. That ratio is, to a certain extent dependent on the lay-uppers skill and experience, however more important to the ratio, in this application, is how the tabs are pressed (by wood blocks covered with duct tape as a separator. These blocks are put in place to shape the tabs and are clamped together. The tighter the clamp the more goo that will ooze and get on the floor reducing the amount of epoxy in and thickness of the layup.

 

I found my tabs to be a little narrow also.

 

However, I did not want the lateral forces of landing to be transferred to the gear bulkheads through the ends of the tubular thingies through which the massive gear bolts go, (MKMGA for you purists) which would have been the case if I had just put some washers on each side, with the ID the size of the bolt, to fill the space. (I believe that there have been cases of these parts being broken from their epoxy bonds and shifting, because of this).

 

What I did was to bond washers, the IDs of which were the size of the MKMGA so that they butted against the tab, not the tube so as to transmit the lateral loads through the tabs, not the tube. It worked out well. I believe that I put one or more layers of BID over the washers, continuing to the tabs for further retention (cutting the center out, of course) to fill the gap that remained and to retain the washers.

 

The asembly, from the rear bulkhead to the bid overlay to the washer to the tab, through the tab assembly to the other tab through the washer through the other BID layer(s) to the front gear bulkhead (or the reverse, if you will), barring any looseness is essentially one piece. The bolts and tubes which go through the tabs serve to hold the gear in place and to transfer the torquing load of landing (or standing) to the the bulkheads through the tabs. (The bolts, of course put the whole mess in a compressive mode bulkhead to bulkhead which prevents movement of the tabs with respect to the bulkheads, thus transferring the stress directly.)

 

I do have some photos of that somewhere, if there is interest, I will try to find them and attach the (If I can figure out how to do it)

 

By the way, this is an armchair engineer's evaluation-I am not trained as a real engineer but I play one on the web....If anybody with the proper credentials want's to chime in, I would welcome it. ( I will try to suppress my feelings of hurt)

 

Disclaimer.. . The above is a description of what I did and my reasons for doing it. It does not, in any way represent anything other than that and is not a suggestion that you should do the same.

[Wayne Hicks]

Maybe I'm a little confused, being that I'm in the Mojave desert, it's 105 degrees, and my plans are back in Virginia 2768 miles away.

 

It's the tube and the bushings that set the distance between the landing gear bulkheads. The tabs do not do this. The only criteria for the tabs is to ensure they don't end up too thick. You don't want the overall width of the tabs to be wider than the tube + bushings.

 

Check the M-drawings. This relationship is shown very clearly there.

[Phil Kriley]

I'm trying to understand - are you saying that your tabs come into direct contact with your bulkheads?

[steve]

nope, the bushings stick out a 1/16" from the bulk heads.

the gear tabs are, at there widest point are glass

(because you covered them with glass when you installed the washers)

or you had wimpy tabs and the bushings at the end of the tubes stuck out past the washers/bid, i need to look at the m's i guess.

[Wayne Hicks]

On the Cozy IV, it's bushing to bushing contact. Again, going from memory:

 

1. There are bushings inserted inside the landing gear well into each set of small rectangular plates on each landing gear bulkhead.

 

2. There are bushings on each end of the tube going through the landing gear tab.

 

3. So it's bushing, bushing, tube, bushing, bushing

 

Something like that. I remember putting a large area washer that fit over the bushing. But I don't recall glassing over the face of the bushing.

[Wayne Hicks]

Go to this page and see the pictures under explanation #3. It shows the tube set between the landing gear tabs and the bushing sticking out from the tube.

 

This page, first picture shows the bushing/bushing/tube/bushing/bushing arrangement set between the landing gear bulkheads.

 

This page, very last picture shows the bushing sticking out from the rectangular plates on the landing gear bulkheads.

[argoldman]

Go to this page and see the pictures under explanation #3. It shows the tube set between the landing gear tabs and the bushing sticking out from the tube.

 

This page, first picture shows the bushing/bushing/tube/bushing/bushing arrangement set between the landing gear bulkheads.

 

This page, very last picture shows the bushing sticking out from the rectangular plates on the landing gear bulkheads.

 

Beautiful pictures, and nice work Wayne,

 

I guess that "I took the blows and did it My way"

 

I can't understand why one would want to prevent the forward and rearward movement of the entire main gear depending only on the relatively weak joint created by the bond of the MK?? tube (sanded steel with divots (or the cozy Girrrls modification), embedded in flox) to the gear and tabs.

 

Please convince me why one would want to do that (other than perhaps that that is the way that the plans were written, which of course have never been revised:rolleyes: ).

 

My readings in the various web pages has supported my contention that this weak bond does, in some, indeed, fracture yielding basically a flox bushing in which the mk??s can move forward and rearward with respect to the gear and tabs (actually they stay in the same position relative to the gear bulkheads and the fracture allows the gear leg to move forward and aft with respect to the bulkheads.)

 

The MK?? tube does not go through the bulkheads but buts against an aluminum plate the inside (between) the front and rear bulkheads and is captured there by tightening the main bolts. forward and aft forces on the gear thus are transferred to the bulkheads through the fragile interface of this cylindrical,sanded and divoted piece of steel embedded in flox. (but I repeat repeat myself myself)

 

It seems that these connections through the tabs are not subjected to much rotation or there would be significant wear on the bearing surfaces as well as the bolts. Is anybody seeing wear here?-- does anybody look at that in their conditionals??

 

When these tube-glass bonds break, if they do, and have, one might not notice it unless in its slight movement, one notices different tracking, vibration, different tire wear or creaking noises emanating from the hindquarters. If one doesn't lift the gear off of the ground by the fuselage or engine (mount) one will never be able to detect if this fracture has indeed happened.

 

Just out of curiosity, how many flying bird owners lift the plane off of the ground by the fuselage and give the gear a strong pull or hit to detect movement?

 

I will try to locate my pictures tonight and try to post them. (I'm jealous of your pictures:p )

 

In that location, I, personally want a broad bearing situation, not the potential massive stress transmitted through a weak joint.

 

One caveat, it has been a long time since I did this, and I may have forgotten some issues, but I don't think so.

 

Land safely with a strong gear:cool:

[Wayne Hicks]

I think I'm interpretting correctly what you're asking.

 

There have been a few longezs and at least one Cozy III that I know of that have had the main gear tabs break loose from the main gear landing tubes. By "break loose," the BID layup over the tube's dimpled section lets go. It debonds. The main gear tabs are then free to slide back and forth (mostly back) along the tubes and bushings.

 

This happened on the Cozy III that I was flying. One side broke loose, then the other. The gear moved rearward about 3/4"-1". It was enough to make the nose alot heavier.

 

I reset the gear into position, then insert some phenolic spacers that took up the gaps between the main gear tabs and the landing gear bulkheads. I did this at all four locations.

 

Now the landing gear was solid as a rock. Moving the landing gear forward to where it was supposed to be made the nose easier to pick up. The plane got airborne a little faster too.

 

I haven't heard of any landing gear of the IVs breaking loose. I'm sure there are some, but I'm assuming not as many as the Long-EZs. Our IV gear is beefier.

 

So, if you're asking, "Shouldn't we do something to take up the gaps?" My answer is "I think the Cozy IV gear is beefy enough. But I do have a backup plan."

[TMann]

.... I don't think I have those?

[argoldman]

I think I'm interpretting correctly what you're asking.

 

There have been a few longezs and at least one Cozy III that I know of that have had the main gear tabs break loose from the main gear landing tubes. By "break loose," the BID layup over the tube's dimpled section lets go. It debonds. The main gear tabs are then free to slide back and forth (mostly back) along the tubes and bushings.

 

This happened on the Cozy III that I was flying. One side broke loose, then the other. The gear moved rearward about 3/4"-1". It was enough to make the nose alot heavier.

 

I reset the gear into position, then insert some phenolic spacers that took up the gaps between the main gear tabs and the landing gear bulkheads. I did this at all four locations.

 

Now the landing gear was solid as a rock. Moving the landing gear forward to where it was supposed to be made the nose easier to pick up. The plane got airborne a little faster too.

 

I haven't heard of any landing gear of the IVs breaking loose. I'm sure there are some, but I'm assuming not as many as the Long-EZs. Our IV gear is beefier.

 

So, if you're asking, "Shouldn't we do something to take up the gaps?" My answer is "I think the Cozy IV gear is beefy enough. But I do have a backup plan."

 

Wayne, Good on ya!

 

Thanks for chiming in

 

Shortly after I made what I suggested in prior posts, I read of several incidences where there was this exact kind of slippage.

 

The "fix" that you made is similar in concept to the washers concept that I used.

 

Why not build that into the gear in the first place????

 

the cozy IV gear still relies on the tube/glass interface for for-aft strength (resistance), beefy or not.

 

Steady gears to you

[Wayne Hicks]

Why not build that into the gear in the first place????

Well, that a fabulous idea. It's been in my game plan since Chapter 9:

 

(1) Use large area washers that fit over the tube and bushings.

(2) Use one, two, three of them, whatever it takes, to take up the gaps.

[argoldman]

Why not build that into the gear in the first place????

Well, that a fabulous idea. It's been in my game plan since Chapter 9:

 

(1) Use large area washers that fit over the tube and bushings.

(2) Use one, two, three of them, whatever it takes, to take up the gaps.

ya ya ya:cool2:

[steve]

Go to this page and see the pictures under explanation #3. It shows the tube set between the landing gear tabs and the bushing sticking out from the tube.

 

This page, first picture shows the bushing/bushing/tube/bushing/bushing arrangement set between the landing gear bulkheads.

 

This page, very last picture shows the bushing sticking out from the rectangular plates on the landing gear bulkheads.

not to get off topic but this has been bugging me for over a year.. 2 things

i see from your web that you cut the rear of the main bow for caliper clearance

? matco's right ? i see in the plans it said in front and horizontal.

i missed it and cut the rear as well, it seemed the only way to fit it, your thoughts?

next is(dont get mad) the bow, you stated 2x8" and all would be in tow

last year i followed your thinking and set the bow up on a table with the ends lifted to the 8 deg so the squares would define the trailing edge. then i marked the full side,flipped it and did the leading edge, but i noted that the marks were tapered and it would take the full 8" to get a good wing shape as you stated. the leading and trailing edge looked so close i tried flopping it opposite and redoing the square's to find center and it all lined up, the 1/2 way point was dead on from top to bottom....add 1" for brake line and your done.

[steve]

not to get off topic but this has been bugging me for over a year.. 2 things

i see from your web that you cut the rear of the main bow for caliper clearance

? matco's right ? i see in the plans it said in front and horizontal.

i missed it and cut the rear as well, it seemed the only way to fit it, your thoughts?

next is(dont get mad) the bow, you stated 2x8" and all would be in tow

last year i followed your thinking and set the bow up on a table with the ends lifted to the 8 deg so the squares would define the trailing edge. then i marked the full side,flipped it and did the leading edge, but i noted that the marks were tapered and it would take the full 8" to get a good wing shape as you stated. the leading and trailing edge looked so close i tried flopping it opposite and redoing the square's to find center and it all lined up, the 1/2 way point was dead on from top to bottom....add 1" for brake line and your done.

here are my brakes,well the heat plate anyway

[argoldman]

as promised, I have attached some pictures of how I handled the landing gear tube situation

 

Pix are slightly out of order. The first (left) is the gear with finished washers and bid cover, before trimming. The second shows the extra length of the tube. the third shows how I indexed the washers in a bed of flox so as to keep them perpendicular to the bore of the tube. The last shows the washer floxed on, before some fill flox and the bid cover (sorry for the blurriness in this picture)

[steve]

That look good rich, mine looked just like that ! befor i found the missing 40 layers of bid. the plans have you do 2 big layups then you do 2 more the next day. i must have gotten that day off...lol

so i did the 20 and 20 and there was just bearly room for the washer

i see in your pic what looks like 2 colors of glass on you tab (not 4),

is that right ? i can show you mine after i get some light up in the hell hole but my tab is 1/4" bigger than my thumb:p

[argoldman]

That look good rich, mine looked just like that ! befor i found the missing 40 layers of bid. the plans have you do 2 big layups then you do 2 more the next day. i must have gotten that day off...lol

so i did the 20 and 20 and there was just bearly room for the washer

i see in your pic what looks like 2 colors of glass on you tab (not 4),

is that right ? i can show you mine after i get some light up in the hell hole but my tab is 1/4" bigger than my thumb:p

 

Yes, Steve,

 

There are only two big layups. All of these layups are continuous rather than being 1 continuous thin set of uni layups (on on the top and one on the bottom then to be reinforced by those extra bid partial layups. It is possible, that with the difference in the plans between the cozy and the aerocanard and the cozy necessity for the other plys that those additional plys make up the difference and give a flush surface at the MK-tube.

 

What have others noticed in terms of the overhang? The difference may be between the Cozy IV and Aerocanard plans.

 

In the Aerocanard we use 2 large multi-ply lay ups of Triaxial cloth (BID and UNI combined) (thus only the two colors) and no auxiliary layups as does the Cozy.

 

The outside width of the tabs, and thus the amount that the tube projects, is determined by a Jig (Probably in both plans as they are almost copies of each other)

 

The below pix show the way these are done.

 

 

thanks for your vigilance. Just for grins, however, I will recheck my instructions.

[argoldman]

Steve, I just reread my plans for the tabs. (in less of a sleep deprived state)

 

The aerocanard uses 16 plies of Triaxial cloth for each side of the tabs, 16 on the outside and 16 on the inside. I guess I can breathe easily now:cool2:

 

What appears to be only a few layers of glass in my picture of the inside glass is an illusion as the way I laid these up is with a number of smaller wetted out lay up packets. (looking at that picture initially gave me a start also-- which all goes to prove-- don't look back at the work that you have done and forgotten why you did it that way:o

 

My understanding is that knitted glass such as triaxial is approx 20% stronger than woven glass of the same weight (due to the fact that all of the fibers are essentially unidirectional (orientated as the equivalent of one 90 degree bidirectional with a single unidirectional layer at 45 degrees to the 90 degree angle formed by the two unis perpendicular to each other. ))Breathe.. this approximates a BID with a uni at 45 degrees. These fibers are laid on top of each other and stitched together rather than woven as the standard cloth that we use.

 

BID and standard UNI are woven. The weaving process demands that each fiber is not straight but must joggle around, either above or below intersecting fibers ( or every other intersecting fiber as in crowfoot weave )(even with Uni), thus decreasing their strength. (that's why in the spar we remove the crosswise fibers on that heavy material.

 

The triaxial cloth, I believe is somewhat heavier, per ply, than standard BID or UNI and thus has more strength.

 

If we calculate, at 20% greater, multiplying 32 (total layers per tab) by 120%, we arrive at about 38.4 plys, roughly equivalent to the 40 specified in the Cozy IV (not even taking into account the heavier fabric per ply

[Big Steve]

Steve:

 

I thought I would send you a couple of pictures of how my gear tabs look on my plane. They are not perfectly even on each side due to getting the gear legs lined up properly. Steve build on

 

[argoldman]

Nicely done.

 

Even with the extra plies on the outside, it seems like the tube sticks out the same amount that mine did. It is possible that the aerocanard plans changed the dimensions of the jig so that the OD came out the same.

[steve]

looking for a web that shows flairing for main gear.

what do i seal the fitting that fits into the brake caliper with ?

i am trying to flair mine today and redo the naca and gear cover.

here a some pic from today. ty in advance