Boatnerd Discussion Forum

We've also all heard of hatch combings being damaged by gravity chutes as well

Gravity chute docks also aren't able to load footers as well as belt docks because the chutes aren't able to spread the cargo across the 105' beam. In Marquette the American Spirit had to load one side then back out and then use the other side of dock to finish loading.
The belt dock in Escanaba could load us as quickly as the chute dock at Presque Isle with none of the hassle of shifting but the downside was that only one boat could be loaded at a time in Esky where PI could load 2.

[quote=Scott post_id=273273 time=1747580346]
So, from the information posted here, the shuttle loaders are only efficient for a small number of freighters? Was this taken into consideration when the shuttle loaders were installed or was it merely a trial and error process?
[/quote]

I believe you have that sort of backwards. The shuttle loaders are efficient with any ship designed for ore movement on the great lakes regardless of whether they have standard sized hatches or the smaller hatches configured for shuttle loaders only. The movement away from chute loaders was also made possible by the transition from the shipping of bulky natural iron ore to marble-sized taconite that could be handled better by conveyor and is also one of the primary reasons that self-unloaders became the prominent type of vessel in the US ore trade on the lakes. Shuttle loaders were designed specifically to load lake freighters with the standard parameters of the hatch spacing and sizes taken into consideration during the engineering process. The reason some ships (relatively few) were built with the smaller hatches that can only be loaded with shuttle loaders goes back to the intended roles these ships were intended to serve when designed and built (in some instances limited to between only two ports). The Cort, Gott, and Speer were all designed solely for the movement of taconite with their cargo holds also having smaller cubic foot capacities and larger ballast tanks in comparison to other vessels of their class. This stems from them being built by steel companies (Bethlehem and USS) that at the time were only concerned with the movement of iron ore for their own consumption and not necessarily in the wide scale movement of outside cargoes. This not only restricted them to loading at shuttle equipped loading docks but also to unloading ports with specifically designed hoppers due to the vessel's short shuttle unloading booms. If my memory is not faulty, I believe that at the beginning of the 1970s shuttle equipped loading docks consisted of only Silver Bay and Taconite Harbor, followed shortly after by Superior, Duluth, and Two Harbors before the end of the decade. Thousand footers built for other fleets such as American Steamship, Columbia, and Interlake that required a more diverse cargo handling arrangement due to the need of serving a wider range of trading patterns built their thousand-footers with standard sized hatches to enable operation over a more diverse range of ports and cargoes. As has been noted in other posts on this topic, ships of this size still have some restrictions when it comes to loading at certain ore docks such as the 1,000 footers built by Bay Shipbuilding being unable to load at Marquette.

[quote=Scott post_id=273273 time=1747580346]
So, from the information posted here, the shuttle loaders are only efficient for a small number of freighters? Was this taken into consideration when the shuttle loaders were installed or was it merely a trial and error process?
[/quote]

The shuttle loaders are efficient for all ships regardless of hatch size or hull depth, because ships are loaded faster, and they put less stress on a hull during loading because the loading is continuous. The gravity ore docks are outdated technology, but due to decreasing demand for iron ore pellets since 1980, there is no economic justification to spend money to replace them with new ship loaders. The gravity dock in Marquette is nearly ideal for the thousand footers with a 50 foot hull depth because they can fit under the chutes, while still having an angle of repose sufficient for loading. The distance from the lake level to the hinge pin on the chute at the LSIRR ore dock is 43 feet. Six-West at Duluth has a distance from the lake level to the hinge pin of the chute is 40 feet 4 inches. At Two Harbors that distance is 39 feet three inches for Dock #1, while Dock #2 North has a distance of 40 feet 4 inches. The LSIRR ore dock in Marquette has the greatest distance between the lake level to the chute hinge pin of all the other gravity ore docks

I can't recall which dock was first to ship taconite, but the first loading dock with a shuttle loader was at Erie Mining's Taconite Harbor. Reserve Mining's Silver Bay dock has two conveyor loaders. They both came into operation between 1956-57.

The design for the Stewart J. Cort was started around 1966, with a building contract signed between Erie Marine (Litton Industries) and Bethlehem Steel in late 1968. She was designed to load at the ore dock in Taconite Harbor, but was also designed to load at Silver Bay. The hatches are narrower (along with the Edwin H. Gott and Edgar B. Speer) because of the reach of the conveyor loaders at the two docks mentioned. (US Steel's DMIR modified Dock #1 South in Two Harbors in late 1978 so that the Gott and Speer could load at that dock. Dock #6 East was modified in the early 1980s.)

I've enclosed a diagram of a cross-section of the Presque Isle loading at a gravity ore dock.

[quote=Scott post_id=273273 time=1747580346]
So, from the information posted here, the shuttle loaders are only efficient for a small number of freighters? Was this taken into consideration when the shuttle loaders were installed or was it merely a trial and error process?
[/quote]
Seems the opposite - the shuttle loaders sound more versatile, while the gravity chutes pose problems for the larger boats.

So, from the information posted here, the shuttle loaders are only efficient for a small number of freighters? Was this taken into consideration when the shuttle loaders were installed or was it merely a trial and error process?

The Speer, Gott, and Cort with their teeny central hatches were designed to only be loaded at shiploaders. A regular thousand footer can and more often is loaded at chutes these days, but it is not a particularly efficient way to load them, and requires a lot of creative shifting and dock recharging. I know the PI used to take the shuttles on her port side at Two Harbors and then back out move over and do the rest of the load at the ship loader, not sure if she still does that regularly.

I think that is a safe assumption. Some thousand footers can be loaded at the chutes, but it isn't really easy. Except for maybe the Presque Isle. The 730 foot boats can be loaded at the chutes. Essentially, it has to do with the placement of the hatches on the main deck. Those footers with small hatches midship, no chance.

It depends on the hull depth of the ship, the water levels and the height from the lake level to the center-point of the hinge hole of the chute.

The Presque Isle was designed for loading at the gravity chute ore docks due to her hull depth of 46 feet. The American Spirit, Mesabi Miner and James R. Barker can load at the gravity ore dock in Marquette, but they have to be ballasted and can only load on one side of the vessel. They have to either move to the other side of the ore dock or turn around so the opposite side of the ship can be loaded. That's because of the angle of repose of the chute. Too shallow an angle of the chute means that the iron ore won't flow into the ship's hold.

Vessels with a greater hull depth than 50 feet will have issues loading at the gravity ore docks because of their greater depth and the angle of repose of the chute.

I've noticed that lakers at the ore docks in Duluth will sometimes use the shuttle ship loader while other times they will use the gravity fed chutes. Are certain ships designed more for the shuttle ship loaders and not the gravity chutes?