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David Emery's Gilbert Erector No. 10 Coal Loader

Dave writes: "We've all looked at the picture... the one with the boy in necktie and shorts kneeling beside the Erector Coal Loader. (Did kids really dress like that?) Although I had seen this model on manual covers for years, I had no idea which set, if any, had actually built this model. I found the answer when I bought a reproduction No. 10 Erector manual from a friend. But the drawings of this model are so lacking in detail, and the reproduction manual is just rough enough that I never gave construction more than a passing thought. Then there was the matter of finding the parts, especially the 'Y' clamshell which, if you can find one, can cost $400 or more.

A few weeks ago I saw photos of Bob Galler's No. 10 Coal Loader on this website and wondered how difficult it would be to build. I studied the drawing of the hoist mechanism in my manual and found it, at first, to be indecipherable. I laid gears and other assorted parts out on the bench to help me understand what I was seeing... and in a flash of inspiration I saw it. Eureka! Then I noticed that I had all the necessary parts... well, almost all. No 'Y' clamshell and no 'CQ' slotted couplings. But I forged ahead and had it operating in three days!

My version of the No. 10 Coal Loader, as you see it here, is a very close replica of the original as it appeared on Erector manual covers and as it was intended to be built with the No. 10 Master Engineers Erector Set from the Classic period. All parts other than the 'Y' clamshell and 8 'CQ' couplings are original except for the occasional hardware store nuts, bolts and washers.

There are really only four significant differences in my version of this famous model: the first difference (if it is, in fact, different) is the manner in which the 'P58' motor is mounted; the second is my reproduction 'Y' clamshell, very ably made by Brian Johnson; the third is the use of homemade 'CQ' slotted couplings; and the fourth is the addition of a circa 1953 'Smoke-and-Choo-Choo' unit inside the boiler, along with an orange light. I am fortunate enough to have two of these rare 'Smoke-and-Choo-Choo' units, and they are really a spectacular addition to Erector models like this one.

Construction of the Hoist Mechanism
The first task was the construction of the hoist unit, and I immediately ran into difficulty. From the drawings, it appears that the boiler and 'P58'` motor are mounted on a base made of two 'P' regular baseplates, with the gearbox made of two more 'P' plates mounted on the side. But the gears wouldn't mesh! The 'P14' worm gear sat about 1/8" above the 'CJ' 36-tooth gear. Something was very wrong! Finally, I solved the problem by mounting the 'P58' on an 'EJ' gearbox base. The boiler is mounted on a small base made of 2 'Q' small baseplates. The gearbox, made of two 'P' baseplates, is held together by two 'N' brackets. The boiler base covers one end of the 'EJ', and the gearbox is mounted on top of the 'EJ' at the other end. The 'P58' sets in the middle, raised above the 'EJ' by the additional thickness of one 'H' 11-hole strip to allow the worm and gear to mesh without pressure. The net result is an arrangement that works smoothly and reliably! For all I know, this is the intended arrangement, but there is no way to tell for sure; the drawings simply don't show it.


The next obstacle was the gearshift mechanism. From the drawings in the manual, it appears that the lower-drum gearshift gear train is made of two 'P13' 12-tooth pinion gears mounted between two 'H' 11-hole strips. When the gearshift is engaged, the gear train is supposed to tilt toward and mesh with a third 'P13' mounted on the drum shaft. But it didn't even come close! I laid several gears out on the bench and soon discovered the reason: the manual drawing is misleading. These gears aren't 12-tooth 'P13's... they are 18-tooth 'P49's! And when the 18-tooth gears are used, everything fits together perfectly.


There was a similar issue on the other side of the hoist mechanism, exacerbated by the fact that the placement of the upper drum made the 'gear gap' even wider. This requires the addition of a third 18-tooth gear in the gear train meshing with a fourth 18-tooth gear on the upper drum shaft. It is the addition of the third gear in the upper-drum gear train that makes it necessary to use a pair of 'I' 21-hole strips to make the bracket instead of 'H' 11-hole strips. But since there is no drawing of that side, you just have to figure it out.

There are other gear train configurations that work, but there are problems with each. You can use 'CJ' 36-tooth gears on both drum shafts which provide maximum lifting power, but the drums then turn too slowly; the same occurs if you use 'MP' 24-tooth gears. You can easily use a 'P13' 12-tooth pinion gears on the upper drum shaft, but a 'P13' on the lower drum shaft causes the gear train tilt so far when engaging that it interferes with the 'BT' that drives the boiler piston. I finally figured out a solution to make the 'P13' work properly by changing the angle of the 21-hole strips that hold the drums. I have used this 'P13' arrangement in my model in order to closely approximate the original design.

It is necessary that the drums turn at exactly the same speed or else the clamshell will open or close as you raise it or lower it; when the drums turn at the same speed, the clamshell remains closed unless you open it intentionally, or vice-versa. Therefore, you are stuck with the same gear train scheme, whatever you choose, on both drums.

As far as I can determine, the use of 'P49' 18-tooth gears is the most satisfactory arrangement for this model. In my opinion, none of these other arrangements are as mechanically sound The 'P49' gears mesh well when engaged by the operating levers, avoid interference with other parts of the mechanism, and produce a reasonable balance between lifting speed and power. You will need 9 'P49' gears in all... 7 for the gear train mechanism just discussed... and two more for the clamshell carriage discussed later in this article.

The Tower
The base onto which the hoist mechanism is mounted is made of two 'S' 10" baseplates. The 'outriggers' to which the tower is fastened are also 'S' baseplates, but if you don't have these, there is no reason that you can't use standard 'MN' 12" baseplates. As I erected the tower, I used a level to keep it straight and to keep the arms straight and parallel to the base.

Construction of the tower is very straightforward. But have plenty of 'C' girders handy (it takes 84), plenty of washers (you may have to cheat and go the hardware store), and plenty of 'S-62' 7/8" screws! It's all square girders except for the dumper funnel braces and dumpcart railings. No matter which way you orient the square girders, you will inevitably have to screw something into them 'the weak way' (that is, through the girders that are not supported).

As I mentioned, I don't have authentic 'CQ' slotted couplings. These are used to hold 4 'P57E' 8" axles as tower braces. Even if you can find original 'CQ's, they may cost $10 or more each, and this model requires 8. There are two options: you can use 'P15' dual couplings and screw one of the setscrews through the end hole of the 'F' 5-hole strip; or you can do as I did and split 8 'P15's halfway with a standard metal-cutting sabre saw blade. A standard sabre saw blade is exactly the right width and if you take your time, you can produce your own 'CQ' couplings that are virtually identical to the originals but at a small fraction of the cost. And 'P15' dual couplings are easy to find.

Cabling and Operation
Another mystery was the method of running the string to operate the clamshell. This proved to be easy. The trick is to tie one end of each string to the rod that supports the end of the clamshell carriage arm. One string is then passed over a pulley on the carriage, down to the clamshell, back up over the opposite carriage pulley, and down to one of the hoist drums as shown on any manual cover. The other string is threaded in the same manner. If this is done properly, one lever raises the clamshell, and the other closes the clamshell. If the two drums are operated together, the clamshell is raised while remaining either open or closed, however it is left. But if the clamshell is raised while the other lever is not engaged, the clamshell will open; if the clamshell is lowered while the other lever is engaged, the clamshell will close. You'll get the hang of it when you play with the levers.

You will notice that you can move the carriage without changing the vertical position of the clamshell. But don't be tempted to use a simple string-and-pulley arrangement to operate the carriage. This will not work well. You will see that the carriage tends to move toward the tower on its own when you raise the clamshell, particularly if there is a load. Even if you add a gear and ratchet on the crank, the load will cause the string to slip on the crank pulley. That is why the original loader uses two 18-tooth gears and ladder chain to operate the carriage.

Because the upper drum and the lower drum are driven by different numbers of gears (4 and 3 respectively), they turn in opposite directions. I found that I needed to wire the motor so that the direction of rotation causes the drums to wind the string on the outside of the drums rather than on the inside of the drums to prevent the strings from rubbing against each other during operation.

Since the motor turns the hoist drums in one direction only, lowering or opening the clamshell is accomplished entirely by gravity, which can be tricky. The clamshell needs to be quite heavy, and the drum shafts well-lubricated and loose, for the clamshell to descend properly when the gears are disengaged. But if the clamshell and load are too heavy, the strain on the motor will be too great and it will not be able to lift the load.

When adjusting the mechanism, be sure that nothing keeps either drum from moving freely... so freely, in fact, that you can spin them with your fingers when the gears are not engaged. Likewise, be sure that all the pulleys are loose and will spin and don't forget to check the 'Z' flanged wheels used for string guides on the tower. Also, be sure that the brake strings are loose when the brakes are off. And place a drop of light household oil on everything that moves. Another source of friction (and frustration) is the tangling or twisting of the cable. Even one twist between the carriage and the clamshell may prevent it from descending smoothly.... or at all.

I found this to be a very satisfying model-building experience. It was challenging partly because the instructions found in the No. 10 manual are lacking in detail, and partly because of the many adjustments necessary to make it operate properly. There is no question that its gravity-driven design could be improved upon. But, in my opinion, few other Erector models (and we each have our own favorites) have the esthetic appeal or the sentimental ties to the 'glory days' of Erector as does the famous No. 10 Coal Loader."