Casting the Merriman Cleat

[Jim Ledger]

I poured a couple of bronze cleats this afternoon. Although the castings were far from perfect I found the results encouraging. The thing that had worried me most, the thin walls, turned out to be not such a problem as I had imagined. The actual flaws I think can be remedied with a hotter pouring temperature and an improved gating system.

[BBSebens]

Forward one with obvious flaw, but the other one looks serviceable.

[hawkeye54]

Thanks for starting this thread, Jim -- I will be watching for updates



Rick

[nedL]

Definately a lot of “cool factor”!

[JimConlin]

I'm eager to see the pattern and the core box.

[MN Dave]

Definately a lot of “cool factor”!

He did say that he would pour the next one at a higher temperature to avoid the misrun.

[Jim Ledger]

Thanks for starting this thread, Jim -- I will be watching for updates

Rick

I'm eager to see the pattern and the core box.

Thanks, Rick, Jim. I had mentioned this project in another thread back when it began. I think that now I'll recap the beginning as well as follow events henceforth so the entire process can be seen in one place. It's an interesting project in itself and has a few new twists that I had never done before, a baked core, for example, and the use of a pyrometer to measure the temperature of the metal prior to pouring.

Definately a lot of “cool factor”!

He did say that he would pour the next one at a higher temperature to avoid the misrun.

Yes, Dave, I did say, that, but the absolute coolness factor will remain quite high, nonetheless.

Forward one with obvious flaw, but the other one looks serviceable.

That's because the photo shows their good sides, Ben. Here's a more detailed look at their casting flaws, which will provide a good illustration of a few ways castings can go wrong and, hopefully, the steps that can be taken to improve the situation.

The rods extending out from the feet of the pieces are vents, whose purpose is to allow air to escape the mold cavity as the bronze is poured in. The same problem occurred in each piece, the foot furthest from the sprue where the bronze was poured froze off before being completely filled. A better gating system and hotter pouring temp would alleviate this.

More to come,

Jim

[Rich Jones]

The good news is that the bronze can be re-used. No wasted material.

[Jim Ledger]

The good news is that the bronze can be re-used. No wasted material.

That is correct, Rich, silicon bronze can be remelted multiple times without the composition of elements changing much. In fact, my failure rate is so high that it's rare that I have to add fresh material, I just keep remelting the old sprues, risers and reject pieces. Also, you always have to melt more metal than you need, the excess being poured off into muffin tin to make small ingots for the next pour.

Here's where the trouble began. I won this cleat in an Ebay auction for twenty-five bucks. At the time I thought it was bronze, due to the lighting of the photo. My disappointment was temporary, however, as I realized that it would make an excellent pattern from which to cast actual bronze knock-offs.

I need four of these.

[amish rob]

That is correct, Rich, silicon bronze can be remelted multiple times without the composition of elements changing much. In fact, my failure rate is so high that it's rare that I have to add fresh material, I just keep remelting the old sprues, risers and reject pieces. Also, you always have to melt more metal than you need, the excess being poured off into muffin tin to make small ingots for the next pour.

Here's where the trouble began. I won this cleat in an Ebay auction for twenty-five bucks. At the time I thought it was bronze, due to the lighting of the photo. My disappointment was temporary, however, as I realized that it would make an excellent pattern from which to cast actual bronze knock-offs.

I need four of these.

I thought you needed four bronze ones?

Peace,
Robert

[Figment]

Hey Jim, I don't want to derail this thread but I'd be interested in your thought process on going with the merriman pattern vs the herreshoff.

[BBSebens]

That is rather more substantial that I thought they were. Hefty!

[Jim Ledger]

Hey Jim, I don't want to derail this thread but I'd be interested in your thought process on going with the merriman pattern vs the herreshoff.

There was no thought process involved, Mike. Without wanting to ruffle any feathers among the Herreshoff crowd over their fine cleat pattern, let me just say that I prefer the Merriman design. They both have the four bolt pattern through widely spaced feet, which is good. The Merriman pattern is a lower fatter cleat, better, in my opinion, for tying lines to and ever so slightly less likely to stub your toes. And they look friendlier, which is a big consideration for a catboat.

That is rather more substantial that I thought they were. Hefty!

They are a generous size, Ben, which is what's needed for this design, both for looks and utility. I often see production catboats whose looks are somewhat spoiled by cleats of insufficient heft. For a deck cleat it's probably wise to avoid anything that could fit in between your toes.


So, I screwed the cleat onto a block of wood in order to be able to clamp it in the vise. Some smoothing and polishing followed...

[Figment]

....And they look friendlier, which is a big consideration for a catboat.

Excellent thought process!

[Jim Ledger]

Excellent thought process!

T'wern't nothin', Mike.

In order to use the cleat as a pattern it had to be split lengthwise along the original parting line. Having done so the extent of the interior cavity became apparent. This was the shape needed for the sand core.

[PeterSibley]

Is your core box and further detail covered elsewhere Jim?

[Jim Ledger]

Yeah, I'm working my way there, Peter. It's a baked core as well, if I hadn't mentioned it, which I think you'll find it interesting. I'm pleased with the way that part is working out.

[J.Madison]

I'm very interested to see how the core is done. I have some cored parts I've been putting off. Details of your recipe would be appreciated!

[PeterSibley]

The very idea ,seeing you have the perfect moldthat won't mind the heat.
Sand and molasses with reinforcing steel for the legs ?

[Jim Ledger]

I'm very interested to see how the core is done. I have some cored parts I've been putting off. Details of your recipe would be appreciated!

The recipe is quite simple and I will share it when we get to that point. The recipe was taken directly from the book "Bronze Casting for the Boatbuilder" written by Sam Johnson.

The very idea ,seeing you have the perfect mold that won't mind the heat.
Sand and molasses with reinforcing steel for the legs ?

I did it a little differently, Peter, as you will see. When I do it again I will make more changes in the light of actual experience. Keep in mind that when I made the core mold I had no idea of the qualities I might expect from a baked core. I thought I might need wire reinforcement for the legs, as you suggest.


One of the requirements of a core in a casting is that the core must remain in position within the mold cavity...somehow. In some cored castings this is easily done. In this particular casting the core has to be cantilevered in the cavity and be held in place without touching the sides of the cavity in any way. I came up with a solution, probably not the same one as the founders at Merriman, but one that worked after a fashion.

The idea was to attach blocks to the feet of the casting patterns, and attach blocks of the same dimension to the feet of the core. In foundry terms these feet are known as the core prints.

[Jim Ledger]

To make the pattern for the core the hollow in the cleat was filled with bondo. A coating of Vaseline inside the cleat allowed the release of the core with only a few taps.

These two cores are the shape required for the sand core. All the parts are labeled as to what came from where as the two halves are different due to the hand carved origins of the original patterns

[Jim Ledger]

The cleat halves were screwed to the wooden core prints, the bolt holes filled with bondo, and the whole given a coat of primer. The core patterns in this photo are just sitting in place, slightly misaligned

[Falcon1]

Following with interest, as I've only just begun to wrap my head around the notion of cores for hollow casting.

As usual, I appreciate your thoughtful process and the clear documentation of same.

Mike

[Rich Jones]

Fascinating to watch the process.

[Jim Ledger]

Following with interest, as I've only just begun to wrap my head around the notion of cores for hollow casting.

As usual, I appreciate your thoughtful process and the clear documentation of same.

Mike

Thanks, Mike. The subject of cores in castings is vast, this being only a slight scratch of the surface. Nowadays cores are made of resin bonded sand and are made in molds produced by CNC machines, which serves to make the subject slightly less interesting. Years back, though, using similar sand mixes to this and patterns made by hand every engine made had a core for each cylinder, cores for the water passages, and a core for the interior of the engine block, all fitting together.

I try wrapping my head around that from time to time. You can look at old films of industrial casting on youtube. During the Thirties there seem to have been a lot of films made. A rudimentary knowledge of casting is a big help in following the action. No matter how sophisticated the work it is always based on the simple principles seen here, pouring liquid metal into a shaped hole.

Jim

[Jim Ledger]

Fascinating to watch the process.

Thanks, Rich.

Here's a video of a small family-run iron foundry in Ireland, back in the Sixties or Seventies, I'm guessing. At one point the old man makes some sand cores.



Sorry for the rabbit-hole.

Jim

[Figment]

That's a grand rabbit-hole!

[jeffcapeshop]

I looked it up and it was still going as of 2014 at least https://www.pressreader.com/ireland/...82879433897756 - that doc was from 89 though!

[Jim Ledger]

Thanks for that, Jeff, the background is fascinating.

For anyone who found that documentary interesting you would be happy to know that it's one of a series. Other episodes feature curaggh making, bookbinding, pottery, saddlemaking. It's a good list.

Jim

[Peerie Maa]

The cleat halves were screwed to the wooden core prints, the bolt holes filled with bondo, and the whole given a coat of primer. The core patterns in this photo are just sitting in place, slightly misaligned

Out of interest, why the pattern for the core in two halves? Is that for ease in casting a bondo core mould?

[willin woodworks]

Jim,

Do the vents exit the cope or are they recesses in the sand for extra metal to fill while expelling air?
Thanks.
JRM

[Jim Ledger]

Out of interest, why the pattern for the core in two halves? Is that for ease in casting a bondo core mould?

This picture should make all clear, Nick.

Forgive me for jumping ahead here, I neglected to take a photo of the plaster casting. Nonetheless...the bondo impressions of the interior cavity of the cleat were used to make two molds in Plaster of Paris. PoP is not the best plaster to use but it's cheap and available at Home Depot. Always a plus, that. The molds had to be painted with multiple coats of spray Rustoleum so the sand would release cleanly. Before use the molds are also waxed.

So there's your sand mixture, all ready to dump out and bake. The formula is as follows...sixty parts dry sand by weight mixed with one part Dextrine, a white powder similar to flour. Separately, mix two parts water to one part linseed oil, you don't need much. Work some oil/water mix into the dry ingredients until you get the consistency of brown sugar, not sticky but able to hold and impression when squeezed.

That's it

Jim

[Jim Ledger]

Jim,

Do the vents exit the cope or are they recesses in the sand for extra metal to fill while expelling air?
Thanks.
JRM

These vents were formed by pushing a sharpened piece of half inch copper tubing up through the cope to the outside. Seeing metal show up at the top of the vent is the first indication of a good pour. They also act as risers to feed molten metal to the cooling casting.

Jim

[Jim Ledger]

350 degrees farenheit, 30 minutes, let it cool. Doesn't stick to the plate.

That's a nice core!

[Rich Jones]

Uh.... is your wife looking for that toaster oven?
I once used our gas grill to melt some lead. The good wife was not happy!