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Obol guitar build

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7 minutes ago, Prostheta said:

No, aluminium is very difficult for a number of reasons including its tendency to dump heat as quickly as it takes it on.

Gold is so yesterday. Nobody has yet made a solid Rhodium guitar.

I research rhodium.  Bronze does plate well.

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That's a really nice casting, it really is. I've considered backyard casting brass into rough blanks for machining bridges, however I know that they tend to attract a lot of inclusions which isn't satisfactory. They'd need a lot of hammering to consolidate.

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Bronze is really friendly.  They make bronze rods for tig welding so you can virtually eliminate large blemishes.  Hammering does work well for small porosity.   Bronze also combines very well to stainless steel.  I have some stainless steel hardware welded to the back of the casting with bronze.

I have also used a large washer slightly offset on a mandrel in a drill.  The offset acts like a little repetitive hammer.

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It's becoming very slightly clearer what you're up to. Fascinating stuff

Is this intended to be a solid bronze cap on a wooden back, or will it be hollow? What sort of weight are you expecting?

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I haven't really done that great of a job describing this build.

There will be a wood back, and the top will be .125"/3.18mm thick - this is target thickness.

This bronze shell will be tapped and have the bridge bolted to it.  Ideally, I would want the bridge to be part of this casting.

I am treating this bronze shell as a large extension of the bridge.  The pickups are actually attached to the wood neck.  The strap buttons and mono cable are also mounted to the wood.  This bronze shell will only contact the wood body of the guitar in the four boss positions.  When the player is holding the guitar, whether standing or seated, the wood will prevent contact with the bronze.  The outer perimeter of the bronze should therefore vibrate freely.

 

At this moment my calculations are showing 6.155lbs for the bronze shell

I eliminated the material between the pickups that is shown on early renderings to further reduce wight.

Conservatively, my current estimate for guitar weight is 8 pounds.

 

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this thread is really interesting. very cool seeing the process/progress. 

I knew I had seen a bronze -or rather bronze dipped guitar previously but couldnt remember where. Then it just now dawned on me- Robbie Robertson of the Band played a bronze dipped strat  on the Last Waltz.

so-just googled to find a pic- and what do you know- fender made a replica- how fender of them. 

I dont really pay attention to the commercial guitar market (much) anymore- so- this was news to me- probably old news to most. 

 

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I have seen an image of the guitar when doing an image search for bronze guitar, but I was unaware of the video.  Who knew that dipping a guitar in molten metal wouldn't destroy it?  You would think the wood would move, or crack or split at glue joints.  The grain has obviously raised in the process.

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I haven't figured shrinkage into my pattern.  For this reason, I am not comfortable starting on the wood parts until after the bronze is cast.  Once I have the part cast I may have to move the mounting positions in the wood for the brass shell.

I know the shrink rate for aluminum, if I have to design tooling, it is normally for vacuum form tooling.  If I had added that shrink to this pattern, it would have been very small.  The other factor that I have not made adjustments for it wax shrink, as I am sure I will experience this as well.

Hopefully those decisions won't come back to bite me.

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I tried my hand at slush casting the wax this weekend.  I was hoping it would be warm enough to do this messy experiment out in the garage, but it just wasn't happening.  The wax didn't even want to melt in the crock pot.

I filled the mold with the molten wax, and then shortly afterwards, the hot wax was poured back out of the mold.  The wax that remained coating the walls of to mold was allowed to cool.  That process was repeated twice in the pursuit to achieve some sort of uniform thickness. 

This process was not as controllable as I was imagining.  I had trouble preventing the wax from pooling in the mold, and I also had a difficult time pouring the wax back out of the mold without spilling it everywhere.  Now, I am in the process of cleaning up the part and Identifying these pooled areas that need material reduction.  Wax will also need to be scraped off the basement concrete.

w0.jpg

w1.jpg

w2.jpg

w3.jpg

w5.jpg

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So how does the wax part of this work? I don't have direct experience myself, so all I can do is make educated stabs in the dark. I'm guessing that wax also contracts as it cools?

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The wax will contract a little.  This wax is, however, formulated for slush casting and has a low-shrink rating. 

Once I add the bosses and some other bits to the inside of the part, it will head over to the foundry.  At the foundry they will dunk the wax part into a ceramic slurry investment.  The first layer of the investment material is very liquid to prevent air from getting trapped in the details of the wax.  Thicker subsequent layers will be built up to form a mold to pour the bronze into.

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Wicked. I love how you're very deeply invested in this project (no joke intended), especially when it is one that few people would have the knowledge to handle. Very cool.

Do you have friends at the foundry or something? It sounds either very costly to contract out as a one-off job or "you have a guy".

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1 hour ago, Prostheta said:

Wicked. I love how you're very deeply invested in this project (no joke intended), especially when it is one that few people would have the knowledge to handle. Very cool.

Do you have friends at the foundry or something? It sounds either very costly to contract out as a one-off job or "you have a guy".

Thanks for the kind words. 

No, I don't have any foundry friends and I have only done the one other bronze project, so I am completely basing the cost off of that experience.

It is not a cheap job, but I soften the blow by doing all the other labor myself.  A lot of people would just take the master ( the primed part I used to make the silicone mold ) to the foundry and come back to pick up a finished gleaming bronze part.  I will do all the wax chasing, metal finishing and patina work myself.

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What sort of cost does this sort of service run at, whether you're taking in a master yourself or half and half? This is fascinating and a great window to peek through.

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55 minutes ago, Prostheta said:

What sort of cost does this sort of service run at, whether you're taking in a master yourself or half and half? This is fascinating and a great window to peek through.

I actually don't know what the breakdown of costs are.  This is a foundry run by artists who are flexible with working with the customer.  I would guess labor must be at least $60 an hour.  When I did my boar heads they gave me a price break over a certain quantity.  Having them cast me six boar heads cost almost the same as casting four.  For the heads- I did all the wax, metal and patina work.  I think the total cost was under $800 factoring in the cost of bronze at $6.00 a pound.  

The foundry will provide a quote to me before they go forward with the casting.  If I were to do a quantity, the price would most likely decrease.  I really hope it will cost me less than $500.

 

 

 

 

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Wow, that's super cool. Obviously this is a deeply satisfying form of art for you, and it's a pleasure that you are sharing the thought process through the project. Truly awesome.

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I dropped the wax part off at the foundry today.  I was spending too much time fiddling with it, now it it out of my hands.

pk.jpg

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The guy at the foundry seemed to completely understand what I was doing.  He did caution me that the piece will most likely distort some and will have to be reshaped.  It sounds like the piece may curl like a potato chip a little, but it is nothing a press can't solve.

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