Knight One-cylinder Motor


Name Knight One-cylinder Motor Designer Gilbert Nelson
Type Spark Ignition, side port Capacity 0.451 cuin (7.39cc)
Bore 0.875" (22.22mm) Stroke 0.750" (19.05mm)
Production run unknown Country of Origin USA (Illinois)
Photo by Ken Croft Year of manufacture circa 1931-34

 

Background

This review came about through a Watzit from a reader. The current owner had been told that it was of German wartime origin, but as it turns out, it was neither, being rather older and of historic American origin. What little that is known of the engine and the company that made it was gleaned from the Engine Collectors' Journal [1], The American Model Engine Encyclopedia (AMEE) [2], and Anderson's Blue Book [4].

ECJ [1] offers one Gil (Gilbert) Knight as the possible designer and builder, saying that some believed him to also be the designer of the Aero Midget made by the Gil Manufacturing Company in the period 1922 to 1933. Certainly, there are remarkable similarities between the two engines, and both originated in Chicago, so a certain amount of common thinking is possible. The article cautions however that this information could not be confirmed. More recent information given in Anderson's Blue Book and the AMEE credits the Knight to Gilbert Nelson, indicating that the information given in ECJ has been proven to be incorrect.

The Knight spark ignition engines were products offered by the Power and Model Boat Company, of Chicago, Illinois, in the early 1930's. As seen here in the company advertising material, their engines were available in three forms; tested and ready to run, or a set of machined parts ready to assemble, down to a set of castings and drawings for the home constructor. In all cases, the engine was offered with either an alloy, or cast-iron cylinder, the latter adding $1 to the price for an assembled engine, or raw castings, but $2 extra in the case of fully machined parts.

The Power Model Boat company produced three models. The first, released in 1931, had a blind bore of 7/8" with a stroke of 3/4" for a displacement of 0.451 cuin (7.39cc). Later, in 1934, a somewhat different design with a bolt-on head finned in a similar way to the GHQ was released. This engine was larger with a displacement of 0.687 cuin (11.26cc) provided by a 1" bore with a 7/8" stroke. To add to the confusion, the three-view at the head of this page depicts a blind bore engine with the larger bore and stroke figures! No examples of this engine are reported by the resources used to prepare this page.

Also announced in 1931 was an in-line, alternate firing twin cylinder engine with a displacement of 0.902 cuin. This was based on components of the 0.451 single cylinder engine. Induction was through a rotary shaft valve in the center section of the crankshaft—quite unusual and advanced for its day. These were made to order, but at least one example is known to exist in a collection. As with the single cylinder engine, the twin was available assembled, ready to assemble, or as castings and plans.

Construction

The Knight pre-dates the Brown Jr and other mass-produced model engines that followed it, owing more to motorcycle design than model engines as we know them. And, along with the Gil Aero Midget which may share some history, being "first", it incorporates some design ideas that subsequent experience shows to have been sub-optimal. Chief among these would be the prop drive arrangement, but let's leave that to last.

The baffeled piston was advertised as being made from an alloy named Lionite. It was fitted with two very broad rings above and below the unusually small diameter wrist pin which obviously owe a lot to full-size practice and would not look out of place in a steam locomotive. The massive bronze connecting rod adds further to the reciprocating mass. The example seen here is a restoration job undertaken by Ken Croft for Mike Beach (England). The wide and widely spaced rings were probably intended to prevent alloy to alloy contact on the alloy cylinder version of the engine, although the engine Ken restored had a very thi steel liner fitted into the alloy cylinder. The may be the wise choice made by a home builder as even with large cast-iron rings, the life of an alloy bore is not going to be a long and happy one. The cast iron cylinder version was was also available would have been quite durable for use in a boat where weight the weight would not a problem.

Ken found the highly complex check-valve "compensating" carburettor to be of little positive value and made this replacement item for running, returning the other to the owner for fitting for display purposes. The Cyrano de Bergerac inlet of the Watzit Knight indicates that others recognized this failing as well.

The crankcase is of the vertically split variety, a design common with many early motorcycle engines. The timer assembly is simple and adjustable. Although open and so subject to dirt and oil, it would have functioned well. This brings us to the prop drive method, and Ken's experience running Mike's restored engine.

Running

According to Ken's notes—wisely written down when he did this job several years ago—the engine would hand-start readily after generous choking and a hefty flick of the prop (like all early spark engines, the Knight has a relatively low compression ratio). Attempts to run the engine on the original carburettor were less successful, even with 3 inches of head to the fuel supply. The surprise came after the engine stopped.

The prop driver requires two holes be drilled through the prop hub to take the screws which clamp the prop between a washer drilled for the screw spacing, and a plain prop carrier which slips ofer the plain end of the shaft and is pinned to the shaft. This can be seen in the photo, as can a split radiating out from the hub into either blade!

The thread on the shaft in this photo is a modification to cure the rather fatal problem where the steel pin has elongated the hole in the alloy drive washer. Bad things happen quickly after that. Close examination of the carved wooden prop illustrated in the Power Boats flyer suggests they may have been fitted with an inset hub disc. Even so, holes like this without carefully made and fitted bushes are dangerous. Ken threaded the shaft end for a more robust retention method when not fitted out in display mode.

Conclusions

Together with the "Baby" (1911), Weiss (1913), Aero Midget (Gil, 1922), and Brown "A" (1931), the Knight would have been one of the very earliest model engines made in the USA. The name of the manufacturing company and the strong boating leanings evident through their advertising material suggest that this was the prime intended use for the Knight. Certainly, with a cast-iron cylinder and a flywheel, the Knight would have been quite adequate to the task. Manufacture ceased in 1934 with the remaining stock and design rights passing to the Acuntra Tool & Die Company of New York who continued the .687 engine under the Fireball 500 name up until 1940 [3] [5].

References:

[1] Engine Collector's Journal, Volume 5, Number 1, Issue #19, Sep/Oct 1966, p18.
[2] Dannels, Tim: The American Model Engine Encyclopedia, Country View Enterprises, USA, 2005, p144.
[3] op cit. p1.
[4] Anderson, Frank: Anderson's Blue Book, 4th Edition, Florida, USA, 2005, p61.
[5] op cit. p26.
[6] Engine Collector's Journal, Volume 12, Number 6, Issue #66, Feb 1980, p12.

 

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