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Author Topic: Cadmium Free Silver Brazing Material Question  (Read 7374 times)

Online Brent Williams

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Cadmium Free Silver Brazing Material Question
« on: October 23, 2016, 12:24:49 PM »
In reading Derek Moran's epistle on control horn construction, he mentions using a silver solder/brazing material that contains cadmium.
    (Silver brazing alloy, 45%Ag 15%Cu 16%Zn 24%Cd, 1400°F, 3/34 dia: McMaster-Carr 7676A7)

http://www.clstunt.com/htdocs/dc/dcboard.php?az=show_topic&forum=103&topic_id=331672&mesg_id=331672

There are similar cad-free brazing materials available.  Will they do the job just as well, minus the cad poisoning risk?

Harris makes a Cad free, 1/16" 45% silver brazing material: Harris,  45 AG 30 CU 25 ZN

Derek's nice work:




« Last Edit: March 15, 2020, 08:25:20 PM by Brent Williams »
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Online Brett Buck

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Re: Cadmium Free Silver Brazing Material Question
« Reply #1 on: October 23, 2016, 12:48:48 PM »
In reading Derek Moran's epistle on control horn construction, he mentions using a silver solder/brazing material that contains cadmium.
    (Silver brazing alloy, 45%Ag 15%Cu 16%Zn 24%Cd, 1400°F, 3/34 dia: McMaster-Carr 7676A7)

http://www.clstunt.com/htdocs/dc/dcboard.php?az=show_topic&forum=103&topic_id=331672&mesg_id=331672

There are similar cad-free brazing materials available.  Will they do the job just as well, minus the cad poisoning risk?

Harris makes a Cad free, 1/16" 45% silver brazing material: Harris,  45 AG 30 CU 25 ZN

Derek's nice work:




   Don't worry too much about cadmium poisoning. Work outside, and it takes about 15 seconds of applied heat, during which negligible amounts of cadmium vapor will be generated. Cadmium and other heavy-metal toxicity takes extensive industrial exposure to cause any significant problem.

    Brett

Online Brent Williams

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Re: Cadmium Free Silver Brazing Material Question
« Reply #2 on: October 23, 2016, 09:59:09 PM »
If one were to have the cad-free material on hand already, would it be generally ok for this application? 

Does the cad' impart something particularly vital to the properties of the brazed joint?
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Offline Motorman

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Re: Cadmium Free Silver Brazing Material Question
« Reply #3 on: October 24, 2016, 09:24:07 AM »
Cadmium lowers the brazing temperature and improves handling characteristics slightly so, without it you're going to need a higher temp and it might not flow as well. I would try it and see if the music wire retains it's strength with the higher temp.

Looking at those horns, fine craftsmanship but, why do you need that bend on the elevator horn? The angle on the flap horn looks too much unless the bellcrank is 1" away.

MM  

Online Brett Buck

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Re: Cadmium Free Silver Brazing Material Question
« Reply #4 on: October 24, 2016, 10:26:57 AM »
If one were to have the cad-free material on hand already, would it be generally ok for this application? 

Does the cad' impart something particularly vital to the properties of the brazed joint?

   Not really, just slightly improves the flow-out, so I am told. I merely noted above that the exposure is not worth worrying about, not that cadmium in the alloy adds anything important.

     Brett

Offline proparc

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Re: Cadmium Free Silver Brazing Material Question
« Reply #5 on: October 25, 2016, 09:13:03 AM »
Harris Safety-Silv 56% high strength.

Cost more but it is not worth losing your plane. No cadmium.
Milton "Proparc" Graham

Offline Motorman

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Re: Cadmium Free Silver Brazing Material Question
« Reply #6 on: October 25, 2016, 11:07:24 AM »
WWTMD what would Tom Morris do?

$110 for that solder, anyone sitting on a life time supply they might want to sell a small amount?


MM

Offline Igor Burger

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Re: Cadmium Free Silver Brazing Material Question
« Reply #7 on: October 25, 2016, 11:19:36 AM »
Maybe better to learn soldering with tin solder, it will leave horn wire without softening. ... just idea, not the answer  S?P

Online Brett Buck

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Re: Cadmium Free Silver Brazing Material Question
« Reply #8 on: October 25, 2016, 11:28:19 AM »
Harris Safety-Silv 56% high strength.

Cost more but it is not worth losing your plane. No cadmium.

   I found perfectly acceptable silver braze at the local hardware store, a lifetime supply for about $12. It is also 56% silver.

    Alpha Fry 53500 Specialty Brazing kit:

http://www.acehardware.com/product/index.jsp?productId=1290591 (up to $19)

    This has about the right diameter of wire, .029. Make a ring of it that fits around the wire of the horn. Clamp it so the wire is vertical and the upright is held in place where you want it.  Put flux on both sides, put the ring of material around the wire on the top. Hit it with a MAPP gas torch for about 10-15 seconds. It will melt, and form perfect fillets on both sides. Let it air dry, then put it in the oven at 500 degrees for about 2 hours. Done.


      Brett
« Last Edit: October 25, 2016, 12:11:05 PM by Brett Buck »

Offline Steve Helmick

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Re: Cadmium Free Silver Brazing Material Question
« Reply #9 on: October 30, 2016, 05:19:19 PM »

Looking at those horns, fine craftsmanship but, why do you need that bend on the elevator horn? The angle on the flap horn looks too much unless the bellcrank is 1" away.

MM  

The fancy curves are to get the flap/elevator pushrod attachment holes over the respective hingelines without cutting a bigger notch out of the TE's of the wing and stab. Some folks also seem to think 45* up & 45* down is what you need, which is just not the case (even on a Nobler). Also, photo angle and/or short lens distortion may make the angles look more severe than actual.  D>K Steve
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Offline Motorman

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Re: Cadmium Free Silver Brazing Material Question
« Reply #10 on: October 30, 2016, 10:58:09 PM »
 

    Alpha Fry 53500 Specialty Brazing kit:

http://www.acehardware.com/product/index.jsp?productId=1290591 (up to $19)

     Brett

Good find.

MM

Online Brent Williams

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Re: Cadmium Free Silver Brazing Material Question
« Reply #11 on: November 27, 2016, 04:35:44 PM »
Brett,  

I have two MAPP torch setups.  A Bernzomatic TS4000KC and a Bernzomatic Mapp/Oxy WK5500.

Will my Bernzomatic TS4000 be suitable for use as you describe it?  
Is the 2 hour, 500°F annealing period a must?
I purchased the Alpha Fry 53500 56% silver brazing kit on your recommendation as well.


Thanks for the info!




  I found perfectly acceptable silver braze at the local hardware store, a lifetime supply for about $12. It is also 56% silver.

    Alpha Fry 53500 Specialty Brazing kit:

http://www.acehardware.com/product/index.jsp?productId=1290591 (up to $19)

    This has about the right diameter of wire, .029. Make a ring of it that fits around the wire of the horn. Clamp it so the wire is vertical and the upright is held in place where you want it.  Put flux on both sides, put the ring of material around the wire on the top. Hit it with a MAPP gas torch for about 10-15 seconds. It will melt, and form perfect fillets on both sides. Let it air dry, then put it in the oven at 500 degrees for about 2 hours. Done.


      Brett
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Online Brett Buck

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Re: Cadmium Free Silver Brazing Material Question
« Reply #12 on: November 27, 2016, 06:35:28 PM »
Brett,  

I have two MAPP torch setups.  A Bernzomatic TS4000KC and a Bernzomatic Mapp/Oxy WK5500.

Will my Bernzomatic TS4000 be suitable for use as you describe it?  
Is the 2 hour, 500°F annealing period a must?
I purchased the Alpha Fry 53500 56% silver brazing kit on your recommendation as well.

  Either will work. Even a conventional propane torch will work but it will take an inordinate amount of time.

   I have no idea whether the annealing/tempering is necessary or not.  I attempted to test a horn to destruction by flexing it back and forth and my hand got tired first. The drill rod is very, very tough when treated this way.

     Brett

Offline Motorman

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Re: Cadmium Free Silver Brazing Material Question
« Reply #13 on: November 27, 2016, 08:37:04 PM »
You could do an experiment. Next time you're brazing a horn see if it's still magnetic at the point the silver solder melts. If not then you didn't harden it.

MM

Offline Motorman

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Re: Cadmium Free Silver Brazing Material Question
« Reply #14 on: December 19, 2016, 12:32:13 PM »
Brett, I used the Alpha Fry 53500 Specialty Brazing kit for the first time today. Propane torch was just fine. Rod was 1/8 music wire and 1/16 mild steel plate. Heated from the bottom. The solder melted and went through the joint but didn't form a fillet on the bottom side. I only used one loop of solder, should I use more to get a fillet on both sides?

Destructive testing to follow.

Thanks,
MM

Offline Tim Wescott

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Re: Cadmium Free Silver Brazing Material Question
« Reply #15 on: December 19, 2016, 02:21:34 PM »
I just use plain old brass brazing rod and an oxy-acetelyne torch.  The first couple of times was a combination of slothfulness and the knowledge that it was going onto a plane that I'd probably crash soon.  For the last five years or so it's been because it works.

Whatever is coming out of K&S these days re-hardens nicely just from air cooling after brazing.  I'm sure it's not ideal, but one of my planes has over 500 flights on it with no sign of problems.

My work isn't nearly as pretty as Derick's, but it works.
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The problem with electric is that once you get the smoke generator and sound system installed, the plane is too heavy.

Offline Motorman

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Re: Cadmium Free Silver Brazing Material Question
« Reply #16 on: December 19, 2016, 08:04:01 PM »
Destructive testing complete.

I clamped the sheet metal part in a vise and grabbed the music wire with vise grips and twisted. On the side where I applied the heat the wire near the joint twisted like it had been softened by the heat. I turned everything around and twisted the other end of the wire. The same thing happened only not as much and then the joint failed. The solder cracked all the way around.

I'm thinking the force I was using would never be seen in the model. Anyone know how many pounds the push rod sees in flight?


MM

Offline Motorman

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Re: Cadmium Free Silver Brazing Material Question
« Reply #17 on: December 21, 2016, 05:23:05 PM »
Did another test. Just heated a piece of 1/8 music wire until it was red hot then let it cool to room temp. About a 6" long piece. I put the twist to it and yes it twisted right where I heated it and eventually snapped off right there. It's official, heating music wire enough to silver solder weakens it.


MM

Online Brett Buck

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Re: Cadmium Free Silver Brazing Material Question
« Reply #18 on: December 21, 2016, 07:14:09 PM »
Did another test. Just heated a piece of 1/8 music wire until it was red hot then let it cool to room temp. About a 6" long piece. I put the twist to it and yes it twisted right where I heated it and eventually snapped off right there. It's official, heating music wire enough to silver solder weakens it.

   Which is why we use drill rod and not music wire. If you want the music wire to work, you have to temper it afterwards, which is a tricky process - which, again, is why we switched to drill rod.


     Brett

Online Dan McEntee

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Re: Cadmium Free Silver Brazing Material Question
« Reply #19 on: December 21, 2016, 08:15:08 PM »
Did another test. Just heated a piece of 1/8 music wire until it was red hot then let it cool to room temp. About a 6" long piece. I put the twist to it and yes it twisted right where I heated it and eventually snapped off right there. It's official, heating music wire enough to silver solder weakens it.


MM


     Nope, not really official. Just calling it "red hot", depending on the lighting in the room here you were, can be 500 degrees or more off on critical temperature. What you are calling "red hot" may actually have been closer to an orange color. 1/8" music wire will start to get a dull red that you could see in a dark room. In a well lit room you might night see the color change and really exceed the temp you need by going by that. Depending on the silver content in the solder, you don't need to get the parent material to "red hot" as you would see it in normal lighting. That would be too hot as to cause the material to oxidize. I don't apply soldering material by what the metal looks like, I apply it when I think it will flow, and always keep the torch moving. And you didn't weaken the music wire, you just changed it and annealed it. And how many twists constitutes "eventually?" If you twisted it 90 degrees or more 15 or 20 times before it broke, that is way more twist than your average large stunt model would ever apply to a horn. Music wire is more or less spring steel, and once annealed, it requires proper heat treating process to put the "spring" back in it. Applying silver solder and silver brazing alloys is something that does take some study and practice. Hot hot you get it, how fast you get it to that temperature, how big the solder is, and how you apply flux and filler material all affect the joint. Most people don't learn this process in one or two joints. And in all of these discussions about soldering horns, the joint design doesn't get discussed much, and is probably as important or more maybe, as what kind of solder or how good the joint is. So you may call it official, but in my 1700 some odd hours of training and 40 some odd years if practice, I might not even call it correct.
     Type at you later and HAPPY HOLIDAYS!
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Online Brett Buck

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Re: Cadmium Free Silver Brazing Material Question
« Reply #20 on: December 21, 2016, 09:47:41 PM »
t. Applying silver solder and silver brazing alloys is something that does take some study and practice. Hot hot you get it, how fast you get it to that temperature, how big the solder is, and how you apply flux and filler material all affect the joint. Most people don't learn this process in one or two joints. And in all of these discussions about soldering horns, the joint design doesn't get discussed much, and is probably as important or more maybe, as what kind of solder or how good the joint is. So you may call it official, but in my 1700 some odd hours of training and 40 some odd years if practice, I might not even call it correct.

    And it's far from a surprise that if you heat music wire sufficiently, then let it cool slowly, that it become soft and breaks with fatique in the transition from soft to hard. This has always been the iffy thing about using music wire for this. The alternate plan, heat it, then water or oil=-quench it, and you get the opposite issue where the heated zone is excessively hard/brittle, and must be re-tempered. That's always been the issue.

    The alternative is to use soft solder, which is far too weak for this application without other measures.

     Ron Burn and Derek Moran figured out the real solution -  that is to not use music wire, use A2 air-hardening drill rod. That's *much* tougher than music wire in this application.

     Brett

   

Online Dan McEntee

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Re: Cadmium Free Silver Brazing Material Question
« Reply #21 on: December 21, 2016, 10:14:32 PM »
    Hi Brett;
    I have never tried drill rod, have never had the need. I have always had good results with music wire, but I have the ability and knowledge to do it correctly. I can get music wire at the hobby shop, drill rod has to be ordered. I don't know of anywhere in my area where I can get drill rod over the counter. I have no doubt that it can be very useful for our control horns, and again if one is careful with the torch, you can control the temps and keep the rod at the stage you want. But even that takes practice. Your average Joe bell crank doing it for the first time should experiment and test a couple of samples first. The critical thing with whatever one uses is getting the material too hot, which oxidizes things and makes them brittle, or not hot enough and you get a weak, cold solder joint. If you do it enough, you can recognize the subtle little differences. If you aren't comfortable with doing it and fear risking your latest world beater, front row machine, better get something from one of the vendors. Otherwise, practice, practice practice and test, test,test. Doing one or two joints might not tell you everything you need to know, which ever material you are using.
    HAPPY HOLIDAYS!
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Online Brent Williams

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Re: Cadmium Free Silver Brazing Material Question
« Reply #22 on: December 21, 2016, 10:54:16 PM »
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Offline Motorman

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Re: Cadmium Free Silver Brazing Material Question
« Reply #23 on: December 22, 2016, 08:10:27 AM »
Dan, tell us more about joint design. I use a #31 drill then a 1/8" reamer and leave the edges of the hole square. It's a light tap fit with a hammer on 1/8" music wire. Should I chamfer the hole, should it be a sliding fit?

For the flux, I put flux on the wire, flux in the hole, tap the horn into place then flux all around. Should I try to minimize the flux?

You mentioned speed, is it better to heat it faster or slower, I would imagine faster? I was using propane and solder melted in about 15 sec when heated from below.

On the one joint I made I tried to use a minimum of heat and the music wire still got soft. Maybe I should heat it from above so the solder melts without getting the wire as hot then switch the heat to the bottom to pull it through the joint?

I don't know how you would heat the assembly to a critical temp and quench it with out disturbing the solder joint. But like it's been said before it's still strong enough for a model plane even when annealed.

WWTMD (what would Tom Morris do) I'm still gonna get some drill rod.

Thanks,
MM

Online Brett Buck

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Re: Cadmium Free Silver Brazing Material Question
« Reply #24 on: December 22, 2016, 11:22:22 AM »
    Hi Brett;
    I have never tried drill rod, have never had the need. I have always had good results with music wire, but I have the ability and knowledge to do it correctly. I can get music wire at the hobby shop, drill rod has to be ordered. I don't know of anywhere in my area where I can get drill rod over the counter.

   Don't misunderstand, I was merely elaborating on the issue you noted. My current airplane has horns made of music wire, and it has held together long enough for everything else to get worn out.

    But, while Motorman seems to have jumped to a conclusion, I had found similar issues before, which is why it was always nerve-racking to do the silver solder, have a bunch of hard spots, then have to count on eyeballing the tempering process with a propane torch and a positive mental outlook. I tried the same tests to destruction for the drill rod and my wrist got tired before I got it to break.

   You can get the drill rod from McMaster in a day or two. Just use what is says to in the Derek Moran post from SSW, A2 air-hardening drill rod.

    What I *would* be upset about is people going back to soft solder like StaBrite and having it fail on them - which is a near certainty unless you do something to relieve the stress. The simple joint requires real silver solder or brazing, soft solder (basically, anything you can melt with a soldering iron) will not cut it. I think that is a far bigger problem than the tempering issue with music wire.

      Brett

Online Brett Buck

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Re: Cadmium Free Silver Brazing Material Question
« Reply #25 on: December 22, 2016, 11:32:43 AM »
Dan, tell us more about joint design. I use a #31 drill then a 1/8" reamer and leave the edges of the hole square. It's a light tap fit with a hammer on 1/8" music wire. Should I chamfer the hole, should it be a sliding fit?

    I just use a 1/8" drill. It will slide on the wire without driving it, but it has to be perpendicular or it gets stuck.

Quote
For the flux, I put flux on the wire, flux in the hole, tap the horn into place then flux all around. Should I try to minimize the flux?

    No, glob it on everywhere.

Quote
On the one joint I made I tried to use a minimum of heat and the music wire still got soft. Maybe I should heat it from above so the solder melts without getting the wire as hot then switch the heat to the bottom to pull it through the joint?

I don't know how you would heat the assembly to a critical temp and quench it with out disturbing the solder joint. But like it's been said before it's still strong enough for a model plane even when annealed.

     Don't use minimum heat. Anything hot enough to melt the solder properly will also cause the temper of the music wire to be lost. That's a given, so there's no point in attempting to avoid that and get an improperly-heated braze, as you apparently did.  If you wait until it cools enough that the solder is solid, then stick it under the faucet, it will harden itself dramatically. That's an even bigger issue than it getting soft, so you have to re-temper it by reheating the entire thing to the barest visible red, then letting it cool off. I then put it into the oven at 525 for 4+ hours. The end result, which is iffy, is supposed to be a single hardness throughout, or at least, relief from the hard spots. Usually, if you mess up. it will break or not bend properly when you bend the ends, and it work-hardens as you bend it.

   This issue mostly goes away with the drill rod, it won't get soft, it hardens slightly, but nothing that causes an issue. It's overall softer and less springy than music wire and might have more propensity of tweaking itself unintentionally.  I still heat-treat the completed part in the oven but I can't see that it does anything aside from leaving a nice "straw" discoloration. It is much, much tougher than the music wire.

   Brett

     

Offline Igor Burger

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Re: Cadmium Free Silver Brazing Material Question
« Reply #26 on: December 22, 2016, 11:35:30 AM »
What I *would* be upset about is people going back to soft solder like StaBrite and having it fail on them - which is a near certainty unless you do something to relieve the stress.

I do  VD~

Online Brett Buck

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Re: Cadmium Free Silver Brazing Material Question
« Reply #27 on: December 22, 2016, 12:27:02 PM »
I do  VD~

   If I had to use soft solder, that's what I would do. I don't know if he invented it, but I got that particular method from Keith Trostle.

   I actually liked Sergey Belko's method better, and it reduces the load on the joint much more than the "key" method,  but I was not able to jig up my attempt to replicate it accurately enough to keep the two legs aligned.

    Brett

Offline Motorman

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Re: Cadmium Free Silver Brazing Material Question
« Reply #28 on: December 22, 2016, 03:29:54 PM »
This might be helpful.  https://www.mcmaster.com/#catalog/122/3753/=15l1hxi

Click on heat treating guidelines for tool steel.


MM

Offline Istvan Travnik

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Re: Cadmium Free Silver Brazing Material Question
« Reply #29 on: December 22, 2016, 04:38:31 PM »
dear Friends,
It is not forbidden to build the control horn of two pieces (plus some brass tube), see it:

https://plus.google.com/photos/117790355930193335731/albums/5715088163776972593/5731000107701851922?pid=5731000107701851922&oid=117790355930193335731

(and next 8 pictures)
It made of spoke of some small motorcycle (dia. 2.6 mm or 1/9" ), a little bit softer material than a music wire. Soft soldered, to avoid metallurgic problems, appearing above 500° Centigrades.
I use this arrangement since the early '70s and never broke it, despite to frequent trimming, which makes torsion load.
I could never understand, how can you trust in a soldering, right in that point which can be twisted...


Online Brent Williams

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Re: Cadmium Free Silver Brazing Material Question
« Reply #30 on: March 19, 2018, 10:44:55 PM »
   I found perfectly acceptable silver braze at the local hardware store, a lifetime supply for about $12. It is also 56% silver.

    Alpha Fry 53500 Specialty Brazing kit:  http://www.acehardware.com/product/index.jsp?productId=1290591 (up to $19)

    This has about the right diameter of wire, .029. Make a ring of it that fits around the wire of the horn. Clamp it so the wire is vertical and the upright is held in place where you want it.  Put flux on both sides, put the ring of material around the wire on the top. Hit it with a MAPP gas torch for about 10-15 seconds. It will melt, and form perfect fillets on both sides. Let it air dry, then put it in the oven at 500 degrees for about 2 hours. Done.

      Brett

As a follow up to the earlier posts, I followed Brett's instructions and purchased the Alpha Fry 53500 kit and built my first flap horn assembly this weekend.   
I am using a 4" bellcrank and this flap horn is 1" x 1.25" with a ~12° compensation.

I used 1/16" cold rolled steel, 3/32" A2 drill rod, 1/8" brass tube, 1/2" brass strip and Alpha Fry 53500 silver braze.  I laid out the angles with a protractor first and drilled it with a fresh 3/32 bit.   I used a bench grinder and a hand file for the rest of the shaping.  I made up some round washers out of the same 16g steel to bolster the horn on either side.  I roughed up the drill rod around the area to be brazed and then slathered the assembly with the kit's flux.  I hit it with my Bernzomatic Mapp torch.  20 seconds later or less, the parts turned dull red, the flux and solder flowed and the parts were secured.  The heated flux ran a bit onto the horn and some of the excess solder flowed onto the horn, but I have filed most of that away.  I also made a crude version of Derek Moran's bending jig and used that to bend the arms. 

Overall, I'm quite pleased with my first attempt.  The A2 drill rod and the Alpha Fry silver braze worked just like Brett indicated it would. 
« Last Edit: March 20, 2018, 03:07:34 AM by Brent Williams »
Laser-cut, "Ted Fancher Precision-Pro" Hard Point Handle Kits are available again.  PM for info.
https://stunthanger.com/smf/brent-williams'-fancher-handles-and-cl-parts/ted-fancher's-precision-pro-handle-kit-by-brent-williams-information/

Online Dan McEntee

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Re: Cadmium Free Silver Brazing Material Question
« Reply #31 on: March 20, 2018, 09:53:37 PM »
  Hi Brent;
   Looks pretty good. Want to give yourself some extra confidence?  Make yourself a duplicate control horn, but without all all the hole drilling and such, just the basic parts. Then try to tear it apart! That will really show you where the strength is. As you do more of these, you will get better at the silver soldering (or silver brazing) part. Just be careful to not get hings too hot and oxidize it. You know you are there when things start fizzling and burning and you get some white fuzzy stuff left over.
   Type at you later,
    Dan McEntee
AMA 28784
EAA  1038824
AMA 480405 (American Motorcyclist Association)


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