Alloy rocker cover

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mite5255
Posts: 1746
Joined: Thu Jun 02, 2011 1:11 am
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Alloy rocker cover

Post by mite5255 »

I've been asked if I can make a alloy rocker cover like the one in the first photo, the 2nd is the original rocker cover. The cover is 600mm(23.62 inch) long, if i get say 2% shrinkage that means the pattern will need to be 612mm(24.09 inch) long, my question is would the alloy cover tear its self apart as it cool the 12mm (1/2 inch)

Mike
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When life gets tough, remember: You were the strongest sperm :)
F.C.
Posts: 560
Joined: Sat Jun 04, 2011 10:28 am

Re: Alloy rocker cover

Post by F.C. »

Proper gating... PROPER GATING!!! That, AND adequate RESERVOIRS!! You can use the provided originals and make a duplicate that WILL fall into tollerance. You also need to cast with an appropriate alloy of aluminum. A356.

What you need to focus on is ability to cast the appropriate quantity of melt. What is your limit? You may have to upgrade your furnace and crucible, possibly your sand a bit... I don 't know what your limitations are.

A356 melts and pours like butter... it's sweeeeeet. ;) I can direct you where to find scrap of that alloy you can acquire for little to nothing. Very little issue in degassing with that alloy, primarily accommodated by proper furnace control. I have taken original case covers with blown out sections of it and sculpted in the missing pieces with wax and used the repaired component and cast workable duplicates in aluminum (identical to the original component) that mated up perfectly with the case it was supposed to. Shrink WILL happen when there is no metal to continue to fill the mold void as the part you cast continues to chill. Proper gating and reservoir accommodation will counter that. Those pieces you show as potential patterns I'd jump on in a heartbeat and go for the glory. If you want to give it a try, I'm in your corner Mite. :D :D Plan on revising and upgrading some of what you have as sand and/or equipment because I do not know what you have in ability with regard to volume of melt, how your furnace works, and mold flask size. I can direct you how to accommodate any deficiency you have.... just ask. I'm here for you. Promise the client nothing with a generous time frame for proof of delivery, then when you deliver a product and he determines it works, charge appropriately. YOU WILL DESERVE IT.
mite5255
Posts: 1746
Joined: Thu Jun 02, 2011 1:11 am
Location: Caboolture Qld Australia

Re: Alloy rocker cover

Post by mite5255 »

Thanks Frank I just KNEW I could depend on you ;) . Time frame is not an issues, the first one is a love job and I get to keep the pattern, I took this on mainly to get the pattern and then sell what ever I make after

I already use 356 (scrap alloy wheels)
My fulness has about a 10 inch bore, with the tuyere about 1 1/2 inches off the floor, my current crucible only hold 1.4 liters(.36 US gallons) to the brim, depending on how much metal I need, for now I may use a steel crucible

This photo is how I envisage the sprue and gating at three points with shrink bobs, I would use much larger bob's theses are just to show placement, how does that look ;)
IMG_0906_zps5068f6fd.jpg
To get the depth of aluminum I was thinking of gluing strips of timber about the cover to act ans a depth gage and then fill with bog ( body filler) for the fins on top I was thinking maybe a peice of timber say MDF glued to the top and the run it through a mill with a ball conical end mill ( i think thats what they are called )

Mike
When life gets tough, remember: You were the strongest sperm :)
mite5255
Posts: 1746
Joined: Thu Jun 02, 2011 1:11 am
Location: Caboolture Qld Australia

Re: Alloy rocker cover

Post by mite5255 »

Or just line the whole thing on the outside in MDF and go from there,

Mike
When life gets tough, remember: You were the strongest sperm :)
mite5255
Posts: 1746
Joined: Thu Jun 02, 2011 1:11 am
Location: Caboolture Qld Australia

Re: Alloy rocker cover

Post by mite5255 »

With regards to flask size, I 'll make what ever is required
20.00 hrs here and we've just had a BBq dinner, a few cold soothing ales and I'm very very relaxed right at this present moment :D :D ;)

Mike
When life gets tough, remember: You were the strongest sperm :)
F.C.
Posts: 560
Joined: Sat Jun 04, 2011 10:28 am

Re: Alloy rocker cover

Post by F.C. »

Mite,

.36 gallon of melt I doubt seriously will suffice the capacity needed to fill all bobs, gating, and cast product. How deep is your furnace from the lip where the lid sits atop the furnace wall, inside, to the top of your crucible base? Whatever that distance is, subtract 1 inch. Also, what is the diameter of the inside of your furnace wall (in inches, please :lol: ). Whatever the diameter is subtract one inch. The maximum you'll be able to melt in that cavity will be whatever those dimensions are minus the circumference of the inside wall of the pipe you decide to use as a crucible. An ideal furnace will allow 1 inch clearance between the crucible and the inner wall of your furnace, and 1 inch clearance between the top of your crucible and the bottom of the furnace lid.

Using steel pipe for crucibles, generally, is not a good idea as the melt within them will absorb contaminants of the steel and cause a certain amount of gas issue if not fired carefully during the melt process. What is required is a very slllloooooowwww heat build up and never allowing your crucible to get beyond a minimal cherry glow. You do not want the steel to blister and scale. Too hot (bright cherry glow) will begin to cause the steel to off gas some of its properties and thus your melt will begin to absorb it. The meltdown needs to be done at a very sloooooow controlled pace. When you see the metal begin to (ever soooo slightly) develop a barely noticeable pink-ish hue, and your crucible is not much brighter than a very dull (minimal) cherry glow, THAT is when the melt is properly up to temp and will be ready for furnace shut down, purging, and then pouring. I would also highly recommend using the blue cake (tidy bowl product) I recommended Dallen use on his cast. This stuff will work very aggressively at removing trapped soluable hydrogen gas that those scrap rims, pistons, and engine case components are historically known for when remelted.

Further, to help shield your melt from being contaminated with a steel crucible's use, do a healthy pre-spray lining inside the pipe crucible with automotive primer paint. Any rattle-can product available to you in stores will work as long as it's intended as an automotive primer. A stove black spray paint, or exhaust manifold primer paint will also work. As the primer heats beyond its ability to withstand it will lose its color but still remain on the surface of the metal. Aluminum will not stick to it, and it will help keep the steel contact away from your aluminum melt.

If you cannot find any blue toilet bowl chemical cake in your stores, then I'll send you one. One cake will handle a multitude of casts, all it takes is just a pinch of it, about a thumbnail size chunk, inserted into a perforated thin walled steel tube (fixed to a length of solid rod stock as a handle) and just plunge the tube and chemical chunk into the melt and stir till the boiling ceases. The slag developed will be a host of crap the alloy has in it you don't need in your product... and it flares off the hydrogen gas bubbles as well. And yes.... you would paint the rod and perforated tube with the primer paint as well before insertion into the melt.

I'll have to mull over your thoughts and photo regarding the gating and reservoir configuration this weekend to effectively give you my opinion as to whether your intent will work or if it needs some modification.

Frank
Rocco
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Joined: Thu Jun 02, 2011 8:35 am

Re: Alloy rocker cover

Post by Rocco »

mite5255
Posts: 1746
Joined: Thu Jun 02, 2011 1:11 am
Location: Caboolture Qld Australia

Re: Alloy rocker cover

Post by mite5255 »

F.C. wrote:Mite,

.36 gallon of melt I doubt seriously will suffice the capacity needed to fill all bobs, gating, and cast product. How deep is your furnace from the lip where the lid sits atop the furnace wall, inside, to the top of your crucible base? Whatever that distance is, subtract 1 inch. Also, what is the diameter of the inside of your furnace wall (in inches, please :lol: ). Whatever the diameter is subtract one inch. The maximum you'll be able to melt in that cavity will be whatever those dimensions are minus the circumference of the inside wall of the pipe you decide to use as a crucible. An ideal furnace will allow 1 inch clearance between the crucible and the inner wall of your furnace, and 1 inch clearance between the top of your crucible and the bottom of the furnace lid.

Using steel pipe for crucibles, generally, is not a good idea as the melt within them will absorb contaminants of the steel and cause a certain amount of gas issue if not fired carefully during the melt process. What is required is a very slllloooooowwww heat build up and never allowing your crucible to get beyond a minimal cherry glow. You do not want the steel to blister and scale. Too hot (bright cherry glow) will begin to cause the steel to off gas some of its properties and thus your melt will begin to absorb it. The meltdown needs to be done at a very sloooooow controlled pace. When you see the metal begin to (ever soooo slightly) develop a barely noticeable pink-ish hue, and your crucible is not much brighter than a very dull (minimal) cherry glow, THAT is when the melt is properly up to temp and will be ready for furnace shut down, purging, and then pouring. I would also highly recommend using the blue cake (tidy bowl product) I recommended Dallen use on his cast. This stuff will work very aggressively at removing trapped soluable hydrogen gas that those scrap rims, pistons, and engine case components are historically known for when remelted.

Further, to help shield your melt from being contaminated with a steel crucible's use, do a healthy pre-spray lining inside the pipe crucible with automotive primer paint. Any rattle-can product available to you in stores will work as long as it's intended as an automotive primer. A stove black spray paint, or exhaust manifold primer paint will also work. As the primer heats beyond its ability to withstand it will lose its color but still remain on the surface of the metal. Aluminum will not stick to it, and it will help keep the steel contact away from your aluminum melt.

If you cannot find any blue toilet bowl chemical cake in your stores, then I'll send you one. One cake will handle a multitude of casts, all it takes is just a pinch of it, about a thumbnail size chunk, inserted into a perforated thin walled steel tube (fixed to a length of solid rod stock as a handle) and just plunge the tube and chemical chunk into the melt and stir till the boiling ceases. The slag developed will be a host of crap the alloy has in it you don't need in your product... and it flares off the hydrogen gas bubbles as well. And yes.... you would paint the rod and perforated tube with the primer paint as well before insertion into the melt.

I'll have to mull over your thoughts and photo regarding the gating and reservoir configuration this weekend to effectively give you my opinion as to whether your intent will work or if it needs some modification.

Frank
wall height is 6 inch, dia is 10 inch, when I made the furness I stuffed up and put the Tuyere to high off the floor its 2 inches, so I'm losing capacity there, that is why I suggested steel crucible, I'll give your suggestions on using steel a try
When I'm at the supermarket next I get some toilet tablets

frank Metric is soooooooooooooo much easier then imperial measurement you should learn it :lol: :lol: :lol:

Thanks Mate

@ rocco... I've seen them before, he does a fantastic job
When life gets tough, remember: You were the strongest sperm :)
F.C.
Posts: 560
Joined: Sat Jun 04, 2011 10:28 am

Re: Alloy rocker cover

Post by F.C. »

That furnace of yours sounds to me like either I'm not understanding what you're telling me or I do understand and can't believe what I'm hearing. A 6" tall, 10" diameter furnace??????? I need to see a picture of it, inside and out, including how your air/fuel mixture enters the chamber. I'm going out on a limb here thinking there's an easy way to expand your furnace to achieve 20 lbs of aluminum melt and up to 80 lbs of bronze with very little cost and effort. But definately, you WILL need more capacity (if 6"x10" dia.) is all your furnace has in blast chamber capacity. Chances are your fuel and regulator are adequate.

Frank
mite5255
Posts: 1746
Joined: Thu Jun 02, 2011 1:11 am
Location: Caboolture Qld Australia

Re: Alloy rocker cover

Post by mite5255 »

F.C. wrote:That furnace of yours sounds to me like either I'm not understanding what you're telling me or I do understand and can't believe what I'm hearing. A 6" tall, 10" diameter furnace??????? I need to see a picture of it, inside and out, including how your air/fuel mixture enters the chamber. I'm going out on a limb here thinking there's an easy way to expand your furnace to achieve 20 lbs of aluminum melt and up to 80 lbs of bronze with very little cost and effort. But definately, you WILL need more capacity (if 6"x10" dia.) is all your furnace has in blast chamber capacity. Chances are your fuel and regulator are adequate.

Frank
When I built it it was poorly designed, plus at the time I was only using a steel crucible, so now that I use clay graphite I need a 4 inch plinth block to keep the crucible up out of harms way so yes 6 x 10 inch, it does need rebuilding but for the moment its all holding together structure wise, just a bad design


Image
When life gets tough, remember: You were the strongest sperm :)
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