Larry S

My Feedback: (6)

What is the best way to bend 5/32 and 3/16 landing gear wire, with heat or cold bending. I have tried both on 5/32 wire and didn't see much difference but with 3/16 wire I heat the wire up to get a tight bend but not sure of the best way to let it cool to keep it's strength.

Dr1Driver

Landing gear wire is typically "music wire". This is hardened, tempered steel wire. If you heat it past around 500 degrees, you will draw the hardening out of it (called annealing), and you'll have a soft spot. You will NEVER be able to re-harden it in a home shop. Heat treating is a specialized process that involves much more than just heating the wire.

K&S makes The Mighty Wire Bender that is about the best I've seen for the hobby trade. If you work carefully, you can make a 90 degree bend with a 1/4" radius in up to 1/4" wire with it. If you plan to make many sets of gear, get one. Last time I looked, they were under $20. They also make a coil winder for sprung gear applications.

Bend cold wire slowly and allow it to stretch as you bend it. If you try to make a sharp bend too quickly, the wire may crack.

Dr.1

Larry S

My Feedback: (6)

Dr1,
That'e exactly what I wanted to know. Matter of fact, I ordered the K&S coil winder and it will be here today. I do bend a lot of gears so the coil winder should be a good tool to have. Lately I used a torch to get the wire cheery red and make my bends then after I bend the wire, I put it in water to cool it off fast.
I have a plane I want to switch from 5/32 to 3/16 wire and will try the bender when it gets here.
Thank you for your help.
Larry

Dr1Driver

Remember, Larry, DON'T heat the wire. That will soften it and you can't re-harden it just by heating and quenching. Cold-formed is tougher, anyway. As I suggested, bend the wire slowly, don't make the bends too sharp or too tight of a radius, and you'll have some good gear.

Let me know how the coil bender does for you.

Dr.1

Villa

I have been bending the hardened music wire sold at our hobby shops for some 30 years. I just use a strong vice that is firmly mounted. I always bend it cold. NO HEAT. There is one problem. Sometimes the wire breaks. When it does it is VERY jagged. It will cut you to pieces. So I always wear a heavy leather glove on the hand nearest the bend. I bend the wire by pulling it over the vice jaws rather than hammering it. I will hammer it slightly if I think it needs it.

I have now completely eliminate the wire breaking. I used a Dremel grinder to grind a groove in the jaw of the vice, so that the wire inside bend radius is about 1/4 inch or so. To make a 90 degree bend I usually over bend it (so the angle measures about 85 degrees) then I pull it back to 90 degrees. I think this way it will hold the 90 degrees longer. That hand bender described above sure sounds good.

Dr1Driver

Your technique is good, Villa. I'll add to ALWAYS wear safety glasses when bending wire.

Dr.1

Laird SS

You can anneal (remove the heat treatment) the wire by heating it to cherry red and cooling it slowly, make the bend, then reheat treat the wire by heating it again to cherry red and quenching it in either water or oil. Be sure to keep moving the wire until the steam stops rising. This gives a more even heat treatment and leaves the wire in a very hard, brittle state (Rockwell C-62). Now, you should not be able to cut the metal with a sharp file. It will just slide off. Polish off the coloring remaining on the wire with fine sandpaper or steel wool and heat the wire a third, only more slowly this time. You will see the color of the metal change from straw (light yellow) to dark blue to a lighter blue. Stop heating at this point and quech the wire cool again. You will now have tempered (reduced the hardness to Rockwell C-42-45) the wire which will leave it not quite as hard as after the quenching, but not brittle either. You should now be able to make marks on the metal with a sharp file.

There was a thread on this a short time ago. It probably did a better job of explaining things, but I don't have a link to it. You can also find more information on this process in a Machinery's Handbook under Heat Treatment of Steel.

Also, you create very high stresses when you make a bend over a sharp corner. As Villa noted, always make the bend with a radius on the inside of the bend.

MinnFlyer

My Feedback: (4)

As a former machinist for many years, I know enough about heat treating to know that unless I know the specifics about a piece of metal, I wouldn't attempt heat treating.

I'm not saying the above method is wrong, it may be dead accurate, but even if it is, it's just way more than I care to deal with.

I use the vise and hammer method, but rather than gringing a radius into the vise jaw, I just clamp the rod between two "Soft Jaws" that I made fron 3/16" plywood. The plywood will dent and allow for a softer radius.

It's worked well for me for many sets of gear.

PS, I agree with the theory of bending PAST the angle you want, and then bending back to the angle

Charlie P.

I have a variety of the Harry Higley benders.



Pretty simple to use. Clamp 'em in a vice and tug away. If you need a tighter radius . . . that's when the vice and casing hammer go to work.

Flyboy Dave

My Feedback: (21)

I bend my heavy wire cherry red, and have never bothered with it, other than letting
it cool by itself. The heavy wire is strong enough to hold up just fine, even though I may
have altered it with heat. The heavy wire usually breaks when I try to bend it cold. []



FBD.

Keith RCO 10/98

http://www.sailplanes.com/musicwire.htm

horace315

My Feedback: (15)

cold bending is the way to go,i have a 1/2 piece of steel plate i made me a bending jig out of,i welded bolts to the plate with my wire welder.i just clamp it in my vice and bend whatever radius i want to.you can re temper most metal, might not be as good a quality as original.

Dr1Driver

Thank you, MinnFlyer! Proper heat treating takes much more than Laird SS says. The specific type of steel needs to be known, and a book should be consulted for correcttimes and temperatuers. The metal needs to be heated to a specific temperture for a specific amount of time, then cooled in a specific manner. It then needs to be annealed in a certain way. All this takes more equipment than the average R/Cer has in his shop. A torch will not produce the proper amount of even heat for the proper time. You MAY succeed in re-hardening the metal, or you may soften it further. Your shade tree annealing process MAY temper it, or it may make it so brittle that it snaps on the first bounce. Landing gear that is too soft will bend easily at the slightest rough landing.

To prevent these uncertaincies, always COLD bend.

Dr.1

*JCB*

My Feedback: (9)

Cold bending is too much like work. [sm=tired.gif]

I just bent up some 5/32" music wire by heating with a torch, and after it cooled down it seems rock solid to me. After that, I couldn't bend it with my bare hands at all. I tried the cold method, and not only did it take a long time, but the wire kept breaking. Heat it up and it will bend like copper wire. It's not like you need the full strength of hardened music wire anyway

Larry S

My Feedback: (6)

The K & S wire bender worked great. Bent some 3/16 wire for a landing gear for my new Ultrasport 40. Easy tool to use. I had no problems using the tool right off the bad. Really don't know how I got by without it. It takes a little force to bend cold wire but I was amazed how nice it did bend and it did bend in a tight radius. Just make sure you're vise is bolted down really good.
By the way, reason for the heavier wire for the Ultrasport, I'm using an OS 70 4 stroke and had to have longer gears then what I got in the kit to clear for the prop. At first I used 5/32 wire, bent by heating and they just bent way to easily on landings and taxing. Looked like the plane had legs when taxing.
Larry

rambler53

My Feedback: (494)

Bending music wire cold causes microstructure cracks that will make it snap with the slightest impact. Heating it to bend is the correct thing to do but it softens the metal. The right way is to heat it but not to cool it in air. Buy a quart of the cheapest motor oil you can find and cool it by dipping the bend into the oil for a few seconds, pull it out, dip it again, pull it out ,dip it again (3-5 times until cool). The carbon in the oil will harden the surface of the metal again and it will be as strong as new.

Larry S

My Feedback: (6)

Be interesting if some company who makes landing gears for kits or a kit manufacuring complany would tell us how they bend them. Let's face it, somebody had to bend those gears you get in the kits.
We'll soon find out if my gears snap as noted when this darn rain in IL lets up.
Larry

Dr1Driver

Larry, it's done cold, with a automatic bending machine, in much the same way the K&S one works. Bending cold will NOT cause any type of cracking, unless the radius is too tight. Bending hot will destrot the hardening. Yes, it MIGHT still be strong enough, but it might bend at the slightest unusual force, too. Unless you're Superman, you can't successfully bend 5/32" music wire with your bare hands, and they're not calibrated to measure how much force you're having to use on heated or cold steel.

Dr.1

rambler53

My Feedback: (494)

Speculating and guessing sure can mislead a reader here, which seems to be common on these forums.

Cold bending wire is not the best way.

It's clearly an example of doing something faster and cheaper. Get an educated answer that correctly supports the proper method in heat bending and temper treating steel wire, I quote: (http://en.wikipedia.org/wiki/Blacksmith#Bending)

Other than to increase its malleability, another reason for heating the metal is for heat treatment purposes. The metal can be hardened, tempered, normalized, annealed, case hardened, and subjected to other processes that change the crystalline structure of the steel to give it specific characteristics required for different uses. Only steel, not iron, can be heat treated, and generally speaking, the higher the carbon content of the steel, the more it can be hardened.

When working with steels, a blacksmith will heat the metal and then quench it in various liquids such as water or oil. The purpose of quenching is to produce rapid cooling to generate specific microstructures in the metal. A quench from a bright red or orange heat generally results in steel that is hard and brittle, so a second process, called tempering, is usually done to increase the toughness of the piece and reduce its hardness.

Tempering involves heating the material to a specific temperature (lower than red heat) usually called "critical temperature" and judged for common steel by the temperature at which the metal looses its magnetic attraction. Sometimes it is quenched again after this heat.

With most tool steels, the degree of temper achieved can be gauged by the appearance of a colored oxidation tint on the metal surface. Different uses require different hardness and toughness combinations, and so receive different degrees of temper. It is possible to temper different parts of an object to different levels of hardness.

I don't know where those who disagree are getting their expert information. But it's clearly inconsistent with what people dealing in metals would practice, in a quality environment. [X(] It's not what seasoned builders would agree with to cold bend, as you can find them above.

While I'm ranting, read about all the Phoenix ARFs losing elevators on the first flight, or the Dazzler breaking in two on landings and you'll suddenly realize the garbage out there isn't built by any standard but giving you a kit for under $100.00. These include the cold bent landing gears. I shuddered just now. If it runs down the runway once, they feel they served your needs completely. The cheap hardware will cost you hundreds in good RC parts you will crash with it. Or the lousy labor of poorly pinning and gluing hinges, non-reinforced firewalls, etc. Reporting failures after you totalled your RC investment into the ground, are ignored too.

Bending cold certainly does cause stress cracks regardless of the radius, and it's confirmed. Heat Bending with tempering is the better way to do it.

Dr1Driver

You're right, Krosy, you're ranting. It seems your diatribe is directed more at the sometimes shoddy manufacturing processes used in some ARFs than at the process of bending landing gear. You talk about "seasoned builders, craftsmen, and direct experience". OK, I've been building from kits, plans, and scratch for over 20 years. I was a mechanical engineer in a past life, and I've had college courses in theory and practical experience in metals and heat treating. I'm not an amateur, nor do I pull this stuff out of my... I've actually done it.

True, only steel can be heat treated. Ah, Krosy, music wire IS steel. You make a lot of statements about what is "correct", but you cite no examples of what you have personally experienced. Cold bending causes stress cracks - prove it to me. Steel can be PROPERLY heat treated in a home shop - prove that one, too. Show me some real life Rockwell figures.

You fail to mention there are different grades and types of steel, some of which will heat treat very well and some of which will not. It you start with one that will not, it will always be easily bendable.

Assuming hot bending is more desireable, and that's NOT my assumption, but yours, it is only desireable IF the R/Cer can PROPERLY re-heat treat the metal.

I've cold bent landing gear for many years and never had a failure or unusual bending upon hard landings. I only use wire from K&S, I assume they know what they're doing. Of course, you can't just stick it in a vice and pound on it with a 5 pound sledge. There are protocols and proper procedures that should be followed. But what the heck do I know, I've only done it - a LOT!

Now that I've been arguing with a wall in this thread - I'm shut. [sm=47_47.gif]

Dr.1

rambler53

My Feedback: (494)

Dr. D,

If protocols and proper procedures are to be followed like you said, then he should heat it, dip it in oil/water to temper it. It's better than cold bending.

Villa

krosypal
You seem to be covering a great deal in your post of 12-23-06. I would not be surprised to read that the best way to bend music wire (carbon steel wire) to make our landing gear (springs) is to heat it metalurgically and then to quench and anneal it metallurgically. Unfortunately, I do not believe I have the equipment to do this properly. In my post above, under my pen name "villa" I describe my experience. I have been bending cold and been satisfied with the results. After 5-10 hard landings I may have to bend the gear I made back to the original position. This has never seemed much different to me than what I have had to do with gear from kits by manufacturers such as SIG over the past 35 years. You state "Cold bending doesn't work at all on steel wire, period." That is a harsh statement on your part. Mine is the experience you claim no one has offered.

rambler53

My Feedback: (494)

Ok, so the sum total of this thread is to bend it anyway you want to bend it.

Villa

krosypal,
The experience of others is what makes reading this forum worthwhile. Your statement "so the sum total of this thread is to bend it anyway you want to bend it" doesn't really add to this forum. I believe that your method of making the landing gear works. It will probably result in the best possible landing gear, and certainly better than mine. My cold bending method gives me the service I am looking for and is within the limits of my ability. I would not recommend bending it "any way you want" since there are certain dangers and performance limitations involved.

rambler53

My Feedback: (494)

I wasn't serious, to bend it anyway you want, it's just what I see from those like yourself, that recommend doing something the wrong way, and want to hear it's quite OK. No one likes to be told they are doing something wrong, especially after 20-35 years. Cold bending is not a good idea. It's not OK. (I'm trying not to be harsh for you.) Unless you're bending gold, lead, copper, tin, or other soft metal, you shouldn't risk injury and metal fatigue cold bending hard metals. ALWAYS use heat. Naturally there are a lot of grades of steel wire available with different carbon content, you just need to apply the principle accordingly, temper it after you heat it, but heat it to bend it. This record keeps playing over again.