Hi all,

I have a 2M Jekyll pattern plane with 5/32" wire retract struts and I am in the process of learning pattern flying. It seems I have to replace the struts after each day of flying off of our grass field. The struts wire bends at the exit of the retract linkage support. I roll out probably longer on my take off and landings more than average, but do not land it hard. I am finally getting so frustrated with them that I want to either replace the plane with a new plane or replace the landing gear with fixed gear. I was hoping I might get some opinions from the pattern folks out there in these forums.

1) Would replacing the wire struts with the Titanium struts from Central Hobbies help my bending problem?
2) Installing Carbon Fiber fixed gear forward of the wing. Anything I need to be aware of if I go this route? Just add sheeting to the wing to fill the old retract holes?

One other item and sorry it is off topic, are there any links to 401 sportsman videos that would have a narrative of the sequence and description of the box? I have looked at the NSRCA site and it lacks a video.

Thanks for all advice,
Mitch

Mitch,

I'm assuming you are using mechanical retracts.. but even if they are pneumatic it doesn't really matter. Question is.. do you have any type of shock absorbtion in the strut leg? As in a coil in the strut leg like on most main gears on a tricycle gear plane. If you don't have anything that will let it absorb some shock.. it will bend it. Also.. music wire comes in various hardness and you may want to check out what type you are using.. I'm not into metalurgy so perhaps some of the other gurus here can help with that. Whenever you bend music wire some temper will go out of it and perhaps it may need to be retempered.. as in reheated and cooled. That's about all I can think of... as I said.. I'm sure some other person here will have a better idea as to the metal strength issues...


Deadstik....[8D]

When I was flying retracts, I also had some similar problems. I don't know about the Titanium struts, but I bought some retract struts from Bob Violett Models. They are very stiff and didn't need to be bent very often. Also, you might want to buy one of the bending tools so that you don't have to take the struts out to bend them.

Emory.

Dont use titanium. There worse, and they will snap on you because they are brittle. Just get use to the fact that you wil need to rebend your struts after each landing.

Thanks for all the replys,

Deadstick, I have mechanical retracts with a 360 degree loop in the wire. I have purchased struts pre-made and bend my own with music wire with the same results. Wheel always bends back.

Patternflyer, The bending tool is capable of straightening the wire while it is still in the retract housing? That will be worth looking into. If possible can you send the link to the tool or refer me to the manufacture. One concern is I am never sure if the bend is occuring on take off and if I can safely retract once in the air. I do not want to drain my batteries with a retract servo stalled out.

Maybe I just need to get the field guys to cut the grass shorter! The other pattern flier at my field does not have the same problem and he has the same plane and the same retracts. He takes off very quickly (he has a YS 140L and I have YS120) and kills his engine on landing so he spends very little time rolling through the grass.

I will conduct some tests on strut wires with annealing and tempering the wire after the loop is made. I believe the correct way to do this is heat the wire at the bend to relieve the stress in the metal then quench in water. Any metalurgist out there to confirm this is the way to go?

Thanks again,
Mitch

Mahoo
Try using 3/16 spring wire. You will have to drill out the retract hole from 5/32 to 3/16 Keep the 360 loop. Use "lite" wheels. Dave Brown or Great planes . Fixed gear is the other option of course and it will mean filling in holes and making new ones.
Kiwipaul

Mitch,....

You never mentioned which brand of retracts you have? I've used the Great Planes retracts in a .40 size Kaos and have NEVER had them bend back so that they wouldn't retract the wheel back up into the wheel wells. I'm very delighted with the strength and durability of the Great Planes struts, but then again it is only a five pound .40 size plane!

On the other side of the coin,.... I've had a Ditry Birdy which required the gear struts to be bent back forward after each landing (different brand of retracts and different struts). I got into the habit of carring a pair of vice grips in my flight box to facilitate the rebending procedureafter each flight. Currently I have a Boxer 120 with the same problem!!

I have ordered a replacement a set of left and right gear struts for the Great Planes 60 size retracts which I'm planning on using in my Boxer. I have yet to replace them or try them out, but they seem as strong and durable as the forty size struts, only thicker!! Don't know if they'll hold up upon landing a ten pound plane?

Just a suggestion, let me know if it helps.

Signed,
Steve T.
Monson, Massachusetts

I do not know what brand of retracts they are. There is not a marking on the exterior of retracts. It looks like a standard 60 size mechanical retract. Perhaps too small.

One other item has got me thinking. The other pattern flier does not have these problems. As already mentioned he does not roll in the grass as long as I do, but he has different wheels as well. I do not know the manufacture of them but they have a polished metal hub and a foam tire which has a flat contact area, ie. looking at the tire from the front it is square. I wonder if this tire shape is less draggy though the grass. Hmm.

I do like the idea of oversizing the struts by 1/32" It has to be stronger with minimal weight penalty.

Mitch

Mahoo:
I made a tool for my own retracts with the same problem that might help. Take a piece of scrap flat steel bar about a foot long, 1/4 in. thick and 3/4 to 1 in. wide. About 1/2 in. from the end cut a slot across the 1/4 in. edge, a 1/4 in deep, the thickness of the wire. Slide the gear wire into the slot. Now you have a handle. Bend the wheel end with one hand and the steel bar with the wire in it with the other hand. Works for me. Hopes this helps. If I didn't explain it very well, let me know. Puts no strain on the gear mechanism or wing.

Mitch,

I think it is made by CRC, but if you ask them at Central Hobbies or Radio South for the strut bending tool, they should know what you are talking about.

Emory.

Maybe this is a stupid question but do you have the retract strut turned around the right way? That is to say is the 360 loop is properly absorbing the shock? If the strut is turned 180 degrees opposite of what it should be it will bend badly every time. Im trying to state my question clearly. Ok, how bout this. The spring loop should be closer to the trailing edge of the wing than the vertical shaft that is attached to the retract mechanism and the wheel. If the spring is in front of the shaft (closer to the leading edge) it is backwards, the spring action wont work and it will bend every time..... Just a thought.

All that being said I do have to straighten mine a little after a landing in grass, but I use small foam wheels so I dont bounce on touchdown. I think rubber wheels would help but they are way too heavy so I just hit the runway every chance I get!

Mike

I had the MK mechanical unit on my ZN Alliance but I found like you that flying from grass I was continually having to re-bend the wire and even had some cumulative damage to the wing as a result. The strut bending tool works well but in the end I removed the retracts and fitted a carbon fixed u/c to the fuz in front of the wing.

Now I can fly all summer long without having to worry at all about the u/c, and I actually have come to prefer the look of the model with the fixed u/c, it seems to suit the modern style of airframe.

I also noticed no difference to the flying performance with the fixed u/c.

James

I had the same problem - If I hit a bump on takeoff I could bend the struts I had so much they wouldn't retract properly. The original struts in the plane were fairly soft steel, and 5/32 diameter.

I replaced them with 3/16 Spring Air struts. The increase in stiffness was much greater than you would expect from the increase in diameter. I went from having to bend them back every time to never at all, even with some rather harsh landings.

I though that I would have problems with the wings or retract units, but they seem to have held up. The plane in question weights 13 lb dry. I mostly fly from tarmac, but I've been caught short a few times and had to land on grass runoff areas without any problems.

Mitch
I recently went thru this transition. Even considered fixed gear, but I would have to get Bolly swept gear to keep the wheels from being too far forward (expensive and god bit of work involved)
I have a JR Explorer with what I beleive to be Great Planes mechanical retracts with 5/32 music wire.
I replaced them with the 3/16 titanium struts from Central.(still expensive but just ran a 3/16 drill bit through the mount & dropped them in)
Made all the difference. They are not only stronger but lighter than the original struts.
This past Saturday I made a rather hard landing in the wind - it would've bent the original wire badly. The titanium struts flexed quite a bit, but there was no damage & nothing bent. Eureka !!

Eddie

swlacham,
Ray and I JUST discussed this the other day and he has recently switched to titanium struts and I plan to soon if I dont convert to fixed gear. I seem to break a lot of props with retracts which is a result of some crappy landings.
What I wanted to interject was that if you go titanium you may consider keeping a spare set. According to him IF by chance the titanium bends you cant bend it back or it will snap off because its so rigid its brittle.

Just a thought.

Thanks everbody for the replys. It makes me feel better knowing others have had the similar troubles with the struts.

I had a conversation with the other pattern flier at my field and he asked if I had too much toe in. I just checked my wheels and they are indeed toed in excessively now after the struts were bent last weekend. I will be sure to check this more closely with my next strut install. I plan to put a level on the wheel and align with the wing sitting on the wing root on level ground. Is this accurate enough?

The loop is on the aft side of the strut, but it only has one loop. I have noticed some struts have two loops. The total length of the strut is only 6-3/4".

Thanks again for all the info in this thread, the suggestions will keep me in experiments for a while.

Mitch

Mitch
the toe-in is TRULY very important.
During my trial & troubles with the original 5/32 struts, I had toe-in & toe-out. Both caused problems. When hte wheel was toed-out, the strut would bend outward as the wheel tried to roll in that direction, until enough force was generated to jerk the wheel back in -talk about a funnny looking taxi.

I paid close attention to getting the flat spot on the strut, for the set screws to the retract unit and the axle, ground at right angles to each other. Then installing the axle and having the toe-in straight is easier. I just aligned on the mounting screws for the retract unit into the wing and that seems close enough.

Eddie

Reading through these posts I noticed that your retract legs appear to be bending in the same place. This is a sign that the hard skin of the gear leg has gone "soft".

I would replace them with Bob Violet legs or retreat them with heat.

Strip the legs of all attachments, wheels axels etc. and put then in an oven at 550F for 45 minutes. Using gloves and tongs, drop the legs into cold water or oil. This will re-temper the metal and make them less likely to bend. You can do this about two times with u/c legs before the metal will not respond.

Take care when opening the oven. There will be a blast of very hot air that will hurt you if you lean over the door while opening it. And please do remember to turn it off!

Eric,
I like your sense of humor! Maybe I should stick my head in the oven! I called BVM today and they use spring steel for their struts. They are not too expensive so I might give them a try. I am still considering buying the titanium strut too.

The struts are bending in the same spot every time. The bend is between the loop and the retact mechanism.

I have some of my bent struts in my box , I will straighten them and try the temper process you describe with the used and some new struts. It is worth a try.

Mitch

FYI - My Titaniums were no good at all.

I used carbon fiber rod inside a brass tube. The brass is needed for the contact point on the retracts as well as the axles. The carbon fiber of course has 100% memory.

Never had to replace a strut again, very lightweight and also had the benfit of not making the retract servo work so hard.

Hey Ozone,
Tell us more about this composite retract strut! What weight plane, what size brass tube/carbon rod; any epoxy in the tube? etc....

Thanks,

Sorry I forgot to check back..I'll post some building info soon..

Im SOOO pumped.. I flew my plane several times today and never had to straighten my retracts after landing!! WOHOOO!!hehehehe

One other item I noticed on my strut replacements over this weekend. The strut wire extends down past the wheel collar approximately 3/8". I am going to center my wheels in the hole, then cut/file the struts off flush with the bottom of the wheel collar. In this way, the grass will just "hopefully" slip on by.

I took the time to doube check the wheel toe in also. The wheel is straight with no stress on the wheel. But I can twist the wheel (toe in or out) so far that the bubble on my level goes past the centering lines of the level. It appears I have sloppy retracts. I did readjust the adjust set screws for when the retract is extended and did not seam to help the sloppyness of toe in or out.

Congratulations Big Ned, Hopefully I'm right behind you in the celebration.

Ozone, thanks for checking back. We are patiently waiting to hear how this is done.

Mitch