This is cut and pasted, so it kind of a mess...but still great reading!
Mark
http://groups.yahoo.com/group/049Collectors/ JOE KLAUSE
P. 0. Box 2699
Lil(llInOl HIlls. CA 92653
.Some years ago, I was warned of the danger of making casual assumptions. I remember being told by my senior . "Consider the word 'assume.' Think of the first three letters, the next one, and then the last two. Now. if you assume too much. you'll make an (first three letters) out of (next letter) and (last two letters)." I've never forgotten that incident. Nevertheless, I still always assume that no modeler would purposely do any- thing to damage an engine. My faith in this assumption has been fortified by the many modelers who have asked ques- tions such as, "Is it okay to put a T.D. .049 cylinder/piston on one of my reed valve engines~" Obviously there's a concern about not causing damage. Another common question, which came up in a telephone call this past week, is whether an .051 cylinder/piston assembly can be installed on an .049 crankcase. Seems like a good time to review some parts of the Cox .049/ .051 engines.
PARTS INTERCHANGEABILITY
The basic reason why so many Cox .049/ .051 parts are interchangeable is because cf engine stroke. A!! of these engines, whether they're T,D.'s or reed valves, have a design stroke of .386 inches. Similarly, the threads on the cylinder and crankcases are the same, and the crankpin diameter and the con- necting rods also match. Thus, you can freely. interchange cylinder/piston as- semblIes between all.049/ .051 engines.
Please note, however, that I spoke of cylinder/piston assemblies. All .049 engines have a bore of .406 inches. The bore of the .051 is .410 inches. Naturally, the pistons can't be interchanged be- cause of this difference. but there are two other reasons for keeping assemblies intact on the .049's. On the .049 reed valve engines the bores of the cylinder and the piston are straight. The T.D. cylinder has a slight taper.likewise, the T.D. piston is tapered. Although both pistons will physically feel like they fit both cylinders, they should not be arbitrarily interchanged because performance will usually be lost in both instances.
With respect to T.D. crankshafts. crankcases, backplates, prop drives, carburetor retainer nuts. needle valve assemblies. and venturies, thev're the same on the .049 and .051. In tact, the only difference between the lower ends oi these engines is the color oi the plastic carburetor housing. The more common .049 housing is black, and the .051 is red.
The interchangeability of parts of the lower ends of reed valve .049 engines is
not quite as universal. The crankshafts on many of these are identical, however , some reed engil1es that were installed in plastic cars such as the Sandblaster, the Van, and others, had different style crankshafts. Reed valve crankshafts vary even more. However, for the general scope of this column. the crankshafts and crankcases of the following engines are interchangeable:
Black Widow Dragonfly Golden Bee QRC
Baby Bee
The only diffcrence in this group is the anodized color of the Black Widow and Golden Bee crankcases.
The tank and backplateare sometimes considered to be parts of the lower ends of .049 reed engines. Again, there are many variations, so I'll just comment on a few. The backplates of the Black Widow, Goldt:r. Bee, and QRC are the same. The tanks of these engines are also the same except for color and some variation in fuel throat diameter. AII.049 reeds and their retainer springs are interchangeable as are the gaskets.
Cox number 325 is a low compression head. The 1702 is the high compression one.
That completes the parts interchangeability of interest to most readers. If you need other specific information, just send me a stamped self-addressed envelope together with your questions. Before moving to the next general subject, let me give you one caution. Putting a T.D. cylinder/piston assembly and a #1702 glow head on a reed engine will really improve performance, how ever. you will increase the risk of fracturing the crankshaft pin. So, be forewarned.Occasionally, I am asked about the numbers that are stamped on Cox .049/.051 cylinders. \\'here are they located? What do they mean? Well. those two short questions can't be answered with two short sentences. It's more like a short but interesting story. Here goes.
Cylinder numbering is simply a means of identification. The practice was not begun primarily to aid the modeler. Rather, it was begun at the Cox factory as an internal identification system. At one time. there were literallv millions of cylinders manufactured during a year . There were subtle but significant differ- ences in cylinders depending upon the many different engines that were being made. These diffierences were not obvious and so a simple number provided
the answer. Numbers 1 through 9. and a single zero were used. Initially, the small numbers were stamped on the outside of the cylinder about an eighth of an inch above the cylinder threads. Later they were stamped on the side of one of the exhaust ports. In recent years. when internal factory identification was not always deemed necessary, 'ome cvlinders .were not numbered:H,' " is a brief synopsis of what the number meant.
No.1. A two bypass cylinder with a large exhaust port that permitted sub-piston induction. It was originally made for the 290 and 291 series engines that were used in plastic cars later. it was used in the first Black Widow engines. At that time the top cylinder fin was not milled to accommodate a maintenance
wrench. Subsequently, the Black Widow I cylinder had two narrow slits for each I exhaust, and the top fin was milled. but I the cylinder was not numbered in this I configuration.
No.2. This denoted a single bypass. sub-piston induction cylinder. The top fin was not milled. This type was used on the Golden Bee, however, the cylinders were not always numbered.
No.3. A two bypass cylinder that initially did not have the bottom of the exhaust ports milled low enough to pro-
vide sub-piston induction. Later, the exhaust milling permitted sub-piston induction, and the outside was ground for use with an exhaust-restrictor type throttle, and the top fin was milled.
No.4. This was made for T.D. .049 engine. There are two bypasses, each with three separate milling cuts. and the bore is tapered. The exhausts allow sub- piston induction and the top fin is milled.
No.5. This has the same features as number 4, however. the bore is .410
inches. It is used on the T.D. .051.
No.6. Twin bypass, no sub-piston induction. and milled top fin. Some were externally ground for restrictor throttles.
No.7. The same as number2, but wiith a milled top fin.
No.8. Single bypass. narrow exhaust. no sub-piston induction. Top fin not
milled. Used in cars.
No.9. Unfortunately, I do not have samples of this cylinder. My only information is that it was only in very limited production.
No.0. Again. I have no samples, but it reputedly is the same as number 6.
Now if all that sounds reasonablvdefinitive. let me add a bucker-size grain of salt. There are variations to the above. I Some are minor, such as the size of the numbers. and are understandable.
Others are major and unfathomable. For example. I have two number 6 cylinders that both have .410 inch bores and .051 T.D. pistons..I can only conjecture as to how and why they were produced.
Guys, next time around, hopefully I'll have a series of photographs of some interesting Cox engines. Until then. have A happy and blessed holiday season.
Topic: Black Widow or other 8cc stunt tank ?? (Read 1003 times)
