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No.7-7a Compact No.1

Type: Vertical, single cylinder, double acting, slide valve.
Bore 1 in
Stroke: 1 in
Availability 1904-1924.
Design: Standard & Rod. Then Double Standard, Then Inverted Y trunk.

Stacks Image 134

No. 7

1 in. Bore, 1 in. Stroke.

Finished Engine

£3 10s. 0d.


List of Castings
and Parts.

CAST IRON.- Cylinder with Steam Ports cast in ; 1 Bottom ; 1 Cover ; 1 Piston ; 1 Valve Chest ; 1 Cover ; 1 Standard ; 1 Sole Plate and Bed combined ; 1 Flywheel ; 1 Eccentric Sheave.
GUN-METAL.- 1 Each Piston and Valve Glands ; 1 Crosshead ; 1 Connecting Rod ; 1 Eccentric Strap with Rod ; 4 Main Bearing Brasses ; 1 Slide Valve : 1 each Steam and Exhaust Flanges ; 1 Valve Rod Guide.
CAST STEEL.- 1 Crank Shaft.
SUNDRIES.- 1 each German Silver Piston and Valve Rods ; 1 Steel Front Column ; 1 piece Steel for Foot ; 2 Guide Plates ; Sheet Steel for Lagging ; 1 Finished Piston Ring ; 1 Hard Brass Valve Spindle Head ; 1 Sheet Drawings showing all parts full size, fully dimensioned.

Price " " " 7/6. Parcel Post 9d. extra.

All Studs, Bolts, Nuts and Screws, 4/6. Drain Cocks, 2/6 per pair. Cylinder Lubricator, 1/6.
This set is well suited for beginners, as a very small lathe only is required, and it will be found that my special Cast Iron is remarkably soft and can be polished quite as easily as brass. The use of Cast Iron in Models give them a very realistic appearance.
The Sale of this Set of Castings has been enormous - over 2000 lbs. weight being delivered per Parcel Post during December 1904.

Foreign Orders sent Carriage Forward unless cost of postage is included in payment, weight packed is under 7 lbs.


This really is a compact No.1. This reduction in size makes this engine ideal for the model engineer with limited access to machiinery, a very small lathe is ideal for machining this engine. It is also ideal for using with a smaller dynamos. It is also much less intimidating than a larger engine for the beginner. The main diferences are mainly due to the reduction in size, Starting at the bottom, the sole plate has been combined with the base as opposed the the 2 separate pieces in the No. 1. This is the main identifying point for this engine. The base is stepped like the two parts of the larger brother but has a wide rib cast in that runs from the bottom to the top where the standard and rod mount. (See front and back pictures below. Note that the catalogue image and the picture in the sidebar dont have this slope on the front of the base, the engine in the sidebar does have this slope on the back. It may be that the early versions had only a back slope but was modified for later versions) The next change is that the eccentric strap and rod are combined into a single gunmetal casting. cast with a stretched eccentric hole so that cutting the eccentric into two phalves with a 3/32 cutting disk will leave a round hole ready for easy turning. (I think I remembered the size correctly) The engine in the sidebar has no valve rod guide and relies on a long bulge on the top of the valve chest to provide a guide to the valve rod. The engine shown in the catalogue does show a separate guide. It is quite possible that the design was changed between original release and this cataloge, as did the No.1. The Valve rod guide, the Cylinder Block being so much smaller that the big brother there is no room to mount it on the block behind the rod, so it is instead mounted to the right of the rod on the Valve Chest. A single piece piston rounds off the differences. The screw pattern on the Valve Chest Cover is often used to identify between the different models but as can be seen below this small No.7 has been machined with the same pattern as the much larger No.1

Stacks Image 117
Old No.7 Front.

Stacks Image 127
Old No.7 back.


In 1926 Stuart advertized the new No7a alongside the original No.7. They added the 'a' suffix to denote the change in design. On most other engines that evolved they didn't bother with this diferentiation. I have included images below of all three variations of the No.7 to show the evolution. Check out the Evolution V page for more detailed descriptions;

Stacks Image 156
No.7 Standard & Rod
The original No.1 design of Standard & Rod.
Easy to machine.
Fairly easy to setup.

Designed for full power in one direction only.
Stacks Image 164
No.7a Double Standard
The Original No.5 design of Dual Standards.
Designed for full power running in both directions.

Difficult to machine.
Difficult to setup.
Stacks Image 172
No.7a Trunk Guide
The Original Stuart No.5a design of Trunk Guide
Easy to machine.
Easy to setup.
Designed for full power in both directions.

More expensive

Video of Original design No.7.


W.B. writes "I received your castings, and I think that they are the best I have ever clapped my eyes on."

G.W. writes "Received castings safetly this morning. I am very much pleased with them, thanking you for your promptness and attention."

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