Bending Bronze

[KAIROS]

I have a pair of bronze, bottom-action Lewmar 'Emsworth' (1960) sheet winches. Sometime before we owned the boat, someone jumped on, or fell on, one of the winch handles while the 16" long handle was in place in the winch handle socket (see photo below). Whatever happened, it bent the bronze downward, so that the handle is angled a few degrees lower than it's twin.

This didn't effect performance originally. But now we've modified the cockpit area, unfortunately using the winch with no bend as a guide (never realized they were different before) and this slight downward bend in the one, becomes an issue. The photo indicates where the bend is.

Should I risk bending this bit of 5/16 bronze bar back to it's original angle? If so, how? I envision heating it with a torch like I might do if it were steel......but I don't know bronze well, and I don't want to risk breaking or significantly weakening the mechanism at this key point.

Thank You,

Jack

(for scale, the winch base is 6" in diameter. also, the part is easily removed from the rest of the winch guts)

http://www.yachtflyers.com/forum_images/winch.jpg

[ssor]

You can further dismantle the winch and gently apply heat to the bend and coax it back. Be very careful to avoid over heating because some bronze is hot short.

[KAIROS]

......some bronze is hot short.

What's 'hot short' mean?

[Falcon500]

I believe that means it hardens and will crack rather than bend, soft metals have this problem, like aluminum, brass, and copper. They get too hot, get really hard and crack.

and if you heat it in place, put a fire stop behind whatever your heating, the torch is still hot behind the work piece. ;-)

[ssor]

Hot short means that the metal is not malleable but will break like stale bread. 1020 Steel is not hot short and when heated to a yellow heat you can tie it in a knot. but some steel alloys with a high sulphur or phosphorus content when you heat the red hot will simply fracture along the grain boundries. Some bronzes are hot short and you should heat them very carefully and coax them to move before you approach even a dull red in a dark building.

[PeterSibley]

I would be very very gentle about bending that section .It could easily be manganese bronze , (Murray bottom handles winches are made from it ) and it does NOT like being bent .

[KAIROS]

These winches are so valuable to us, and not replaceable, that I think I'll pester a local bronze sculptor.....see if he understands this well and has experience with heating bronze like this. Besides, then I can blame him if it breaks.

[S B]

You have a pair of winches, see what it would cost to have the part, from the good one, cast. Sometimes what seems as the expensive way is the cheapest in the long run.

[paladin]

a very wise move in hiring someone else to do the work.

[KAIROS]

You have a pair of winches, see what it would cost to have the part, from the good one, cast. Sometimes what seems as the expensive way is the cheapest in the long run.

Thanks all. Glad I didn't jump into it. I think I'll let an expert try to bend it back, then if it breaks I can have a new one cast.

I'm assuming that brazing/welding it back together if it breaks would not work well....?

[Tom Robb]

My meager experience w/ bronze is that the hot-short thing happens rather suddenly. I'd follow Paladin or SB's advice or re-do the cockpit before wrecking the winch. I don't suppose Lewmar has parts?

[donald branscom]

You will have to take it apart.
I would clamp it in a vice with the bend close to the vice jaws and try to bend it cold with a long lever.

Measure the angle of the other winch handle socket plate and use that as a guide.

Don't worry about the overheating too much if you do decide to heat it. Just a dull red will do at the most. Bronze will hold its heat for a long time. The color of the metal will change but you cn just give it a quick dip in muratic acid to make the coloring uniform.

You may be able to bend it cold just a little.
But do not worry. Even if it breaks off it can be TIG welded with silicon bronze welding filler wire and be as good as new.

[donald branscom]

My meager experience w/ bronze is that the hot-short thing happens rather suddenly. I'd follow Paladin or SB's advice or re-do the cockpit before wrecking the winch. I don't suppose Lewmar has parts?

Forget all this "hot short" business.
Just a little heat will do no harm.

[donald branscom]

My meager experience w/ bronze is that the hot-short thing happens rather suddenly. I'd follow Paladin or SB's advice or re-do the cockpit before wrecking the winch. I don't suppose Lewmar has parts?

I have repaired many bronze parts. It is not a problem.
"hot short" makes it sound like some trick metal terminology, but just forget that.
I have been a welder most of my life. Never heard the phrase "hot short"- sounds good though, should scare someone.
It will take longer to heat a bronze part than a steel part.

[donald branscom]

Thanks all. Glad I didn't jump into it. I think I'll let an expert try to bend it back, then if it breaks I can have a new one cast.

I'm assuming that brazing/welding it back together if it breaks would not work well....?

If it did break, have it TIG welded with silicon bronze filler wire NOT brazed.
Brazing will not be as strong. No big deal.

[donald branscom]

These winches are so valuable to us, and not replaceable, that I think I'll pester a local bronze sculptor.....see if he understands this well and has experience with heating bronze like this. Besides, then I can blame him if it breaks.

Most sculptors are not that stupid.

Matter of fact a sculptor that works in bronze may know more than the local welder. " Blame the sculptor" I would tell you to get out of my shop.

[ssor]

I have repaired many bronze parts. It is not a problem.
"hot short" makes it sound like some trick metal terminology, but just forget that.
I have been a welder most of my life. Never heard the phrase "hot short"- sounds good though, should scare someone.
It will take longer to heat a bronze part than a steel part.

Welders and blacksmiths often have different experiences with hot working metal.

Brass: C854 Leaded Yellow



Leaded yellow brass has good castability, moderate strength, and a pleasing yellow color that polishes well. It machines well with a machinability index of 80 (Compared to "free machining brass" of 100). It is used in furniture fittings, musical instruments and decorative ornamental fittings. It is the brass of choice for marine brightwork. For marine structural applications I'm told that C873 (Everdure) is a better choice because of its higher long term strength in a salt water environment. Leaded yellow brass contains approx. 67% Copper, 29% Zinc, 3% Lead, and 1% Tin. 2050 F is a good starting point for pouring.

Although the lead content makes this an easy alloy to machine it is recommended that the material not be used in any application where the lead might pose a hazard. This brass can be joined by soldering or brazing. Brazing temperatures will approach that of the "hot short" temperature for this material, so it needs to be fixtured carefully to prevent movement or stress during brazing. (The hot short point of a material is that at which the metal will easily fracture or crumble).

http://www.budgetcastingsupply.com/Metals.php

[Concordia...41]

The shipwright that did most of the work on SARAH was a welder in another life. He was also a steel-boat owner with his own welding rig.

Damn handy guy :D

He successfully bent and/or unbent quite a few of SARAH's bronze bits. Never had a break.

That being said, we all know that the potential for ruin rises in proportion to the preciousness of the piece - and your piece looks pretty precious ;)

Keep up the hard work!

- M

[Vinny&Shawn]

I agree with Dbranscom, I have been around metal my whole life, metal has a memory to some extent. If you put a long bar on that piece clamp it in a vise with protection from the vise teeth. Put gentle heat and gentle persuasion it will go back no problem. Fact is I bent my goose neck last year and bent it back with no harm and no heat.
Just did some bronze bending in a vise and the method was to clamp it, put pressure with a long arm, hold that pressure and then apply heat,it moves back slowly on its own. Don't rush, stop and check your progress with a known angle as you proceed.

[D Happ]

I think I would have it welded up to start with and take it to a machine shop and have it milled parallel again.

[donald branscom]

Welders and blacksmiths often have different experiences with hot working metal.

Brass: C854 Leaded Yellow



Leaded yellow brass has good castability, moderate strength, and a pleasing yellow color that polishes well. It machines well with a machinability index of 80 (Compared to "free machining brass" of 100). It is used in furniture fittings, musical instruments and decorative ornamental fittings. It is the brass of choice for marine brightwork. For marine structural applications I'm told that C873 (Everdure) is a better choice because of its higher long term strength in a salt water environment. Leaded yellow brass contains approx. 67% Copper, 29% Zinc, 3% Lead, and 1% Tin. 2050 F is a good starting point for pouring.

Although the lead content makes this an easy alloy to machine it is recommended that the material not be used in any application where the lead might pose a hazard. This brass can be joined by soldering or brazing. Brazing temperatures will approach that of the "hot short" temperature for this material, so it needs to be fixtured carefully to prevent movement or stress during brazing. (The hot short point of a material is that at which the metal will easily fracture or crumble).

http://www.budgetcastingsupply.com/Metals.php

I have been a welder most of my life. Never heard this phrase "hot short temperature"

I have worked with all metals. Worked in many shops and many projects.

[KAIROS]

..... " Blame the sculptor" I would tell you to get out of my shop.

I usually tell people without a sense of humor to get out of my shop. But, I'd thank them for their input first. ;)

[ssor]

I have been a welder most of my life. Never heard this phrase "hot short temperature"

I have worked with all metals. Worked in many shops and many projects.

Live and learn.

[donald branscom]

I think I would have it welded up to start with and take it to a machine shop and have it milled parallel again.

You could just weld it and finish it with a flap wheel sanding disk.
Machine shop sounds like over kill for a single short weld.

This is a simple project NOT a project for a metallurgist.
Lead in brass,yes that is a consideration if it is for casting a sink fixture you would drink water out of.
We are are just talking about re-bending a marine bronze winch part. Thats all. If you have so much money that you want a machinest to machine a weld which may not even be necessary, maybe you should just take it to a welding shop and get it bent and then take it to a machinest and machine the weld. Then take it to a polishing shop and have it buffed. Oh then the other one will need to be machined to so they match.

[ssor]

This has really gotten out of hand. I said early on to be careful when heating this part to straighten it because some bronze alloys are hot short. You should never try to cold bend a part to straighten it but care should be taken to not over heat it.
The characteristic of hot short or red short is not common but is disconcerting when encountered because we expect that heating a piece to a dull red will make it quite plastic and some alloys just break like Styrofoam.

[jonathanjoseph]

Hot short, red short, what?


I'm with Donald. Bronze is a little tricky, but having fabricated it under xray inspection and lots of empirical, under service evidence, it doesn't take a NASA scientist to make a good part. (Actually I think the NASA guys defer to the tradesmen quite often)
I think we need a slightly better picture and explanation of what needs to be done before saying "Sure, just cold bend it back" but I think this is getting a little over thought for a simple thing like a winch.

Jonathan

[S B]

Old school; You bent it the outside"convex side" is weakened, bend it back and both sides have been compromised. It may fail at the worst possible time.

[jonathanjoseph]

Convex ,concave...it's a winch handle socket, being driven by a winch handle, driven by a human being. If it breaks under load and the operator doesn't realize it's happening, oopps the line stops being hauled. I think he'll be ok bending it back where it started. But for liability's sake he should probably have it magnafluxed,dye penetrant, xray, and destructively tested, just to be sure.
Then he can buy a new winch because no one is going to do those tests and say it's safe. No one.

Jonathan

[KAIROS]

Old school; You bent it the outside"convex side" is weakened, bend it back and both sides have been compromised. It may fail at the worst possible time.

I think I understand the range of options pretty well now. This re-bending and the resulting hardening/breaking is my main concern, and the reason for the post. As I expected, bronze is not like steel in yet another way, but I'm sure it can be bent back with care, whether I or someone with more specific knowledge does it.

And, it will be degraded somewhat by this fix, and may be more prone to breaking next time somebody falls on the handle. But, I'll just route the sheet to it's twin and sail on. Then get it welded OR cast new. There are 4 winches capable of doing this winch's work, so if it breaks it will not be the end of me.

Thanks for the passionate interest though. Really. I get all worked up too when a thread here ventures into my areas of expertise.

[Vinny&Shawn]

This piece has not been extremely misalligned, it has not been compromised or weakened. Bending bronze is not rocket science. A slight twitch and it will be back to normal. I don't believe it will be degraded, again I just spent a month fabricating, heating and bending a complex bend in a bronze flat stock that shows no signs of weakness.
What is the actual differance between normal and the bent piece?

[Cuyahoga Chuck]

Bronze, basically, is copper alloyed with tin. If you heat it up too much you can vaporize the tin. And modern bronzes come in a gazillion different types where a lot of other alloys are present.
In the industrial world there are specialists who do nothing but straighten things. One of their common cold straighteneing methods is to strike the bend a sharp concentrated blow on the high spot. There are machines designed to do this which feature various kinds of striking points and the ability to regulate the force of the blow. Beyond that these outfits have wide ranging experience straightening things so consutlting one of them might bring an easy but somewhat expensive resolution to the problem.

[donald branscom]

I think I understand the range of options pretty well now. This re-bending and the resulting hardening/breaking is my main concern, and the reason for the post. As I expected, bronze is not like steel in yet another way, but I'm sure it can be bent back with care, whether I or someone with more specific knowledge does it.

And, it will be degraded somewhat by this fix, and may be more prone to breaking next time somebody falls on the handle. But, I'll just route the sheet to it's twin and sail on. Then get it welded OR cast new. There are 4 winches capable of doing this winch's work, so if it breaks it will not be the end of me.

Thanks for the passionate interest though. Really. I get all worked up too when a thread here ventures into my areas of expertise.

When a piece of metal gets bent what happens is the the metal gets "work hardened" That means the metal is harder than it was prior to bending.
If you had a 100X power microscope the metal looks like little oval sphere's and after bending, there are less spheres/platelets and are larger.

Breakage could occur if you kept bending it back and forth .
Like if you bent a metal coat hanger back and forth it will finally break.

If you do the bending you will see how much force it will take to bend the metal and you start to get a feel for what it will take.
After you bend many pieces of metal you start to get a better idea over time.
Heating does help to bend metal. If you weld metal(much greater heat), the heat is so intense that on each side of the weld the metal is somewhat degraded (larger platelets) and then a fracture can occur on each side of the weld, and that is called the HAZ (heat affected zone) Many times when someone says " the weld broke" and you ask them was the WELD cracked or the metal next to it? Most of the time the untrained person does not know.

If the actual weld is cracked that means there was a mismatch of chemistry of filler material and or parent material, OR a poor fit up of materials.

If the fracture occurs in the HAZ then other reasons come into play.
Time can take its toll on metal also.

Inspection by x-ray or other methods can also be used but are very expensive and you must decide if it is worthwhile to to that.
Dye penetrant and magna flux only show surface cracks, so x-ray ,ultrasound or other methods may have to be used to find deeper flaws. But every inspection starts with a good visual inspection with a magnifying glass and the human eye.

[KAIROS]

....I just spent a moth fabricating, heating and bending a complex bend it a bronze flat stock that shows no signs of weakness. What is the actual differance between noemal and the bent piece?

Bending once is one thing. Back and forth can lead to 'work hardening' and then breaking. Bent bronze can not be as durable as it was as cast. The difference may be trivial or not. Unknown in this case without ridiculous investment for post-testing. I'll live with the difference, and if it ever breaks I'll do something else with it.

It's a small angle to correct.

Thanks, Chuck, for yet another perspective. Although I probably won't go that route, I'm having fun imagining under what heading in the yellow pages I might find these 'metal straightener' tradesmen (?).

I remember Uncle Bob, between a spit and fart, mentioning that he could fix anything on the farm with a hammer and a blow torch. Thirty years later I used a sledge hammer to fix a computer in his honor. The recalcitrant computer is now on the bottom at 8400 meters, in the Puerto Rico Trench. Fixed it good. Supremely satisfying. But, I want to actually fix this winch and then reinstall it.

(my computer is trembling....)

[donald branscom]

Bending once is one thing. Back and forth can lead to 'work hardening' and then breaking. Bent bronze can not be as durable as it was as cast. The difference may be trivial or not. Unknown in this case without ridiculous investment for post-testing. I'll live with the difference, and if it ever breaks I'll do something else with it.

It's a small angle to correct.

Thanks, Chuck, for yet another perspective. Although I probably won't go that route, I'm having fun imagining under what heading in the yellow pages I might find these 'metal straightener' tradesmen (?).

I remember Uncle Bob, between a spit and fart, mentioning that he could fix anything on the farm with a hammer and a blow torch. Thirty years later I used a sledge hammer to fix a computer in his honor. The recalcitrant computer is now on the bottom at 8400 meters, in the Puerto Rico Trench. Fixed it good. Supremely satisfying. But, I want to actually fix this winch and then reinstall it.

(my computer is trembling....)



Probably will not find them in the Yellow pages.
Just visit a local welding shop.

[ssor]

The science of metal processing is so large that many universities have entire departments devouted to the study of metallurgy and all that is involved in the refining, production, assembly and treatment of metals and their alloys. Some very accurate information has been evident in this thread and some misconceptions have been expounded.

[KAIROS]

After dismantling the winches, turns out both handle sockets have been bent down....just that the one with the least bend was used to configure the cockpit. And the bends are not as localized as I though. Obvious when you set them next to a straight edge. Here's photos.

I'm going to go talk with a wonderfully crusty old blacksmith about straightening these. He won't lead me on. He'll tell me right to my face if I'm a stupid SOB for trying to straighten them, or not. He's been doing this kind of thing for about 60 years! He's in the dictionary next to the word.

The more bent one, then the bent one, then top view.



http://www.yachtflyers.com/forum_images/winch_bend_3.jpg


http://www.yachtflyers.com/forum_images/winch_bend_1.jpg

http://www.yachtflyers.com/forum_images/winch_bend_2.jpg

[KAIROS]

Here's the windup:

Ernest the blacksmith (do not call him Erny), below, prodded and heated those bent parts a bit and immediately quit. "They're made of brass", he says......"I'm not going to heat and bend them".

Probably why they bent originally. So, I'll have the winch handle tubes (stainless steel) bent slightly to give the clearance I need. There's a guy here with stainless tube bending capabilities.

Ernest is less than 5' tall, is on his 4th (young) wife, and he has a whole bunch of kids. A likable character, regardless of what those first 3 wives think.....

http://www.yachtflyers.com/forum_images/ernest_pugh.jpg

[gibetheridge]

Sounds like bending the stainless is the way to go. Perhaps it would be easier to shim up the winch with a nice piece of (tapered) hardwood. Looks like it wouldn't hurt that the hardwood, if bedded in epoxy, would help keep the water out of those checks in the top of the pillar at the same time.

Another thought....Perhaps you could replace the handle with an appropriately shaped wooden handle that would break instead of bending the casting next time someone steps on it, or, better yet, with a shaped slightly flexible handle. HDPE?

[KAIROS]

The winches were mounted in a different location on new teak pads last year. The pads would have to change shape to allow the bolts to slant down through them.......but this gets me thinking I ought to loosen the bolts on one and see how much I could get away with shimming them without redrilling....how much play? The shim would only need to bring up the inboard edge 5+ degrees to achieve the clearance I need. It all depends on how much bigger the winch base holes are than the 3/8 bolts.

Making partial use of your suggestion in the bending scenario, I think I would get new SS tubing and have it bent......keep the originals that go with the winches. Once bent there is a torque issue which we might not like.

Thanks.

[gibetheridge]

Perhaps you could apply the shims to the bottom of the pads, or bevel the the bottoms, in which case you would not have to make the drilled holes in the deck and framing much larger at all. If the holes need redrilling the slack could be taken up with epoxy, or first fill the old holes with epoxy, then redrill?

It must be a concern that someone will eventually land too hard on the handle again. Could you replace them with spring stainless steel in some way, or make them fold up out of the way?