48" Camelback Straightedge Pattern is in Process

Thanks for the positive vibes. They must have helped as the pour seemed to go well—-no runout and no pouring short at least. Now nervously waiting to dig out the casting!

Here is a pic of the mold “clamped shut” and sitting next to the furnace awaiting iron.

Denis

 

Wow, that is a BAF (big ass flask, pardon my french).
I can see why that would sag.

One method that I use when ramming my flasks is to screw the cope to the mold.
You can buy 4" long screws, and if they are not long enough, I counterbore the cope about half way through, and then use a long phillips bit.

Looks like your clamps are working, but the screws may be easier if you are into that.
I would say four screws per side would probably do it.
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Yahoo! It poured nearly perfectly. I am surprised actually and very very happy!

The casting weighs just a few ounces shy of 50 pounds as it is with blind risers, runners, and pouring basin.

There are a couple of minor contraction defects in the front of the sole at the fourth rib from the left. I am pondering why this happened.
It will machine out and is of no consequence, but I wish I could explain it better.

No pics, but sighting down the sole from the end shows it only bows up about a 1`/16th of an inch over its length as I made the sole with a slight downward
bow to prevent more bowing based on my 36" design casting characteristics.




Letters and finish

This is the nub left by the retaining pin in the sand. It will saw off easily.


Ga night!

Denis

 

Congrats! That came out excellent. The lettering is amazing.

 

50 pounds, I think you hit it. The lettering has come out very clear!

You’ve now become another caster, I wished, I lived around the corner from!

 

That is a beauty.
Its great when a casting turns out well.
Congrats.

 

Assuming it was not a sand mold contraction or distortion, then my first guess is that the shrinkage occurred in the last part that solidified.
Just a guess; not sure if its a plausible guess.

I know what they say about stepped runners and even filling pressure across all the gates, but I wonder if a uniform runner that is considerably larger then the largest cross section of your piece would act as a long riser, and since the large runner would solidify last, perhaps stop any shrinkage.
I have used a relatively deep/large runner before, and let it fill completely before it starts filling the mold cavity via the gates at the top of the runner.
It would require more metal and perhaps a larger crucible.

Alternatively add more risers?
There again, more metal.

I recall scavenger being up to a #70 before he dropped off the casting scene.
I designed my crane and pouring cart to handle 200 lbs, although 70 lbs is about the largest iron melt I ever attempted (and failed) to melt several years back.

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Here’s a pic of the new logo glued into place on the pattern. I simply carefully position the logo (or letter as the case may be) and use a syringe to place a single drop of thin cyano glue right next to the letter or logo. The glue wicks under the item and then I use a paper towel edge to absorb the excess glue. The result is a nice neat, firmly attached letter or logo with no excess glue obscuring details or making a general mess. I do sand the application area first to get a clean surface wtih "tooth." The pattern looks a bit grey now as I also use graphite along with talc as a parting agent to get the green sand to separate cleanly from the pattern.





I wish it came through so nice and shiny on a casting. Maybe I should cuarve one for each casting and rivet them in place rather than casting them into the SE! ;-). Ummm, maybe not...

Denis

 

That is a nice touch.
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Thanks, Pat. Fiddling around to make little details like that seems like it can easily suck me in. I have to try to hold back from trying to make it "perfect" when all that is really needed is a recognizable pattern impression. But, since I have done very little detail work like that in aluminum, it was fun to learn what was possible without too much effort. But finally, I just had to call it and say "good enough, move on."

Today, the limited shop time has focused on making a hydraulic lifting mechanism to facilitate clean solo draws of largish (for me) patterns. The plan is to make 3 small hydraulic cylinders that will be independently powered but all extend at an equal pace. So three lifting cylinders independently coupled to three power or driving cylinders. The power cylinders will all be connected to a single lever causing the power cylinders to move lock-step in unison causing the lifters to also move lock-step. Sounds like a good theory. We'll see if it is practical.

Denis

 

Sounds interesting.
Good luck with it.
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Sounds like the system they use to lift houses. If I understand it right by adjusting the flow to each cylinder you can get different sized cylinders to raise/lower at the same rate.
Sounds like a neat project hopefully you will share some photos of the unit / process of fabrication.

Love the pattern work on these straight edges.

 

I've been doing some work on the hydraulic lift for the larger patterns I am molding and plan to mold in the near future. I have completed one proof-of-concept piston pair and have 2 other sets an hour from completion. I think I will use a foot pedal to power all the pistons in unison as that will leave both hands free to monitor/tap the pattern as I apply lift.
The cylinder bases are 2" diameter and 1 thick 12L14. The cylinders themselves are 304 stainless .875 dia. The cylinders are glued into the bases. Pex tubing was used and DTE hydraulic oil is the what I used for fluid.
The rams are drilled and tapped to accept 3/8" bolts to act as compensators for unlevelness of the mold. The overall height of the cylinders will allow them to be lower than the top of the cope or drag. They will attach to the pattern via a piece of plywood or a triangular board arrangement so they can provide lift to the pattern.

Here is a brief video showing the cylinders in action.


A few pics of the cylinders under construction:



I used a 1/16' O-ring in the gland and polished the interior of the tubing so as to minimize friction.

I think this is going to work out. Hopefully, it will be working as a 3-cylinder system tomorrow.

Denis

 

After taking two days off trying to deal with a cold, I made out into the shop for a couple hours. I got the footpedal done. You will notice that it has a lip around the pedal itself. That is so that I can “kick it around“ a bit when I’m at the bench. I’ve noticed when using my TIG welder that being able to easily push the pedal around is a convenient feature. So I Included it on this pedal as well. Using the pedal to control the cylinders should allow both hands free for manipulation of the pattern as it left side of the sand. I’ll post more later when I’m out at the barn packing a mold and hopefully put this thing in to service. Initially I intend to use only three pairs of cylinders and I’ll put a fourth one into service if need be. I made the pedal to accommodate four so that I didn’t have to remake it should I decide to add that fourth one.



Added: Shallow recesses were cut into the base board to locate and hold the power cylinders. They will be secured by screws. You can see the screw holes in their bases.


You might wonder why the upright plywood piece is not placed at the extreme end farthest from the cylinders. That allows me to rest my foot and leg with weight supported by the hinge/upright while not actually putting pressure on the cylinders.

Denis

 

So, I learned a couple things about this setup today. (Working at 1/3 efficiency due to a cold---uggh). First off, using the foot pedal to operate the driving cylinders results in an action that is extremely smooth and easy to precisely control. That is, as long as there is NO air in the system. As I was putting the cylinders together originally I thought it would make little difference if a small amount of air were in the lines since the lifting forces were small and compression of said air should be very slight. However the difference between the static coefficient of friction in the cylinders and their dynamic coefficients does cause trouble. The resulting stiction causes just what you don't want---some initial hesitation followed by the driven cylinder breaking free from stiction and then springing forward. Yes, the deviation from smooth movement is slight, but definitely noticeable.

The solution was to through drill one of the cylinders in each pair and place a o-ring-sealed SHCS in the through hole to allow bleeding of the air post-assembly. As you know, there was already a 3/8-18 hole 1.5 inches deep in the top of all the cylinders to accommodate a height adjustment screw. So, I just drilled that hole all the way through with a tap-sized hole for an 8-32 screw. the bottom of the 3/8-18 hole was flattened with an end mill. The through hole was tapped for half an inch 8-32 from the top of the cylinder. A tiny o-ring was pushed onto a short 8-32 SHCS and then the two-cylinder system was filled with oil after connecting the cylinders with the PEX tubing. The rams were inserted and the 8-32 screw allowed bleeding of the system so that no air remained.

Once that is done there is still some stiction in the system by the "spring" of air is gone so the movement is very predictable and smooth. No herky-jerky stuff.



MAYBE tomorrow I'll get a chance to try it in real working conditions. The cold seems to have eased considerably, so, more should be accomplished tomorrow.

Denis

 

What keeps the rams from being driven right out of the cylinder bore? Normally a hydro cylinder has a collar to retain the ram. Not sure you'll have an issue but I could see myself hitting the pedal just a little too much at the wrong time and covering everything (including me) in hydro fluid

 

The limiting factor is the “pump.” In a typical hydraulic machine a pump supplies pressure to the driven cylinder and that pump has access to “unlimited” oil. So the pump, were the ram not mechanically constrained, could drive the ram out of the cylinder. However, in my application, the pump is the driving ram and it can only be pushed to its lower limit. The entire circuit has only enough oil to extrude the ram 3/4 of a full stroke. So, the driven ram can not be pushed out of its cylinder. Having the bleed screw installed in one of the rams makes excursion adjustment easy.

Denis

 

Here are a couple pics of the cylinders and a video of a lift of the three cylinders one of which has an 8-pound load.

Bleeding the two-cylinder circuit




Denis

 

Nice work Dennis!

What is the straight edge going to be used for? Will it be a datum to measure for gaps on a large surface?

Cheers Charlie

 

The hydraulic levitator worked!! The draw is so much more controlled with this system.

Sorry for the poor viewpoint of the video. Was working alone and failed to realize my big rear end would occupy much of the screen.



Here is a "tour" of the pulled pattern.



Lessons learned: I need to place the lifting sticks I attach to the pattern further toward the ends. Having them so close to center allows the pattern to rock too easily as seen in the very early part of the lift.
Overall I am pretty pleased with the first try. I will make a few slight refinements for next time. I think I will have a much higher pattern draw success rate using this system on largish, deepish patterns.

Added: It looks like the new logo pulled cleanly as well:


Denis