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CMF3 1237-series design concept

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#1 Rick Moore

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Posted 10 June 2020 - 09:08 AM

1237-Series Design Concept, Preface


This is a post some of those out there looking at this weird stuff I’ve been building since the beginning of 2016 have probably been to some level curious about. Since the 1237-Series has surprisingly, particularly to me, turned out to be much more successful than I originally imagined, thinking at the onset they’d be at best just a sidebar in my chassis designs, and now, over 50 design/builds later (not to mention the duplicate builds, and designs that didn’t get built), it is long overdue that I at least make some attempt to outline the premise and hypotheses behind all these chassis.


Is this a better way to design or build chassis that win lots of big races? Nope. Definitely not, for lots of reasons; I have mine, and no doubt others have theirs. It is merely a different way to design and build a chassis, and that is the challenge I wanted, and is all I can offer.


“Design Concept”, applying certain restrictions concerning the usage of profanity, scatological references, and countless disgustingly vile analogies, might be better described as, “Why Not?”


Questions are welcomed, though answers may not be definitive, since the 1237-Series is still an active study, and carry the often used caveat, “Subject to change”.


So, if you’re really bored, grab a frosty beverage, put on some background tunes, cop a comfy seat, and read on through this rambling narrative of design concept and WAG’s for the 1237-Series chassis. Waders are optional. I’ll try to keep it short and simple… Haha… Oh, that sounded utterly ridiculous…I’ll just apologize up front here for the unnecessary length and any additional confusion. Consider yourselves warned! Or, maybe that should be, abandon all faith ye who enter here!




Rick / CMF3


#2 Rick Moore

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Posted 10 June 2020 - 09:13 AM

1237-Series Design Concept, Part 1; Developing the 1237:


First things first. The objective was to design a chassis with an all-wire frame (no structural brass plate or sheet) using 0.032” wire…


All-Wire Framing; pre-1237 History:


My original all-wire framed chassis (early 12XX numbered) were largely an exercise to see if it could be done. All these early frames were built using 0.047” wire. By the “12-teens”, I’d figured it could be done, and with some definite possibilities, but also some inherent problems. With the 1218 I began to get a handle on those early lessons, and finally built a viable frame.


Eventually, the 1219 became the first design/chassis where I could start to incorporate these observations in a series of chassis designs and builds. In the 1219-Series, the 1225 would become the first all-wire chassis design to be built in a variety of dimensions; it also became the first design to be built not only in 0.047” wire as before, but also built using 0.039” wire, and eventually in 0.032” wire. That last one, the 0.032” wire framed 1225-Ca3, was an eye opener; rocket fast and absolutely unpredictable; what it taught me was that for 0.032” wire the 1225 design was all wrong. By the 1229’s I had decided to create “component based” designs to address some of the functional shortcomings. As it would turn out the 1229’s were better as 0.039” frames than 0.047”, and were almost as good when built using 0.032” wire, but still had some loading issues. The 1233-Cc3 was the first successful 0.032” wire framed chassis, but was still basically a 1219-Series design, and had to incorporate a lot of complex “anti-harmonics” for it to work. The 1234 and 1235 never got built. It was time to try something else. This is where the 1237 Series came in.


The 1220-C:





The 1225-Ca:





The 1229-Cb2





All-Wire Framing; 1237-Series:


It had become apparent that in order to build all-wire framed chassis using 0.032” wire that any structural rail (in this discourse “rail” meaning a lone or set of wires connecting two chassis points, not the wire itself; example, a “rail” of 4x 0.032 “wire”) should be as short as possible. By limiting the length, and triangulating/angling the rails, two problems could be solved; one, the component rails could have fewer/shorter wires with equal or greater strength, and; two, the multiple angles/directions of the rails should significantly decrease harmonic vibrations and lateral “spring” loading of the chassis frame.


All-Wire Component Chassis Design:


The concept going in was to have “separate” design elements and assemblies in the all-wire framing that would be interconnected with the framing wires. The concept is pretty basic; it is no different than a kit having preformed brass front/guide plate, side pans, motor bracket, and connecting them together in some fashion. The challenge was to incorporate this “sectional design” concept into an all-wire frame that in essence has no separate components, but still making these components wire-only assemblies that would be adaptable in themselves while being able to be integrated as a whole.


Rear Motor/Drive Assembly:


This is the triangulated portion of the rear of the frame that contains the motor box, rear axle tube and uprights, and lateral rear “wings” forward of the rear wheel wells. The motor/drive as a separate design assembly was originally a concept on the 1229, and worked well. As a “triangulated” unit it removed a lot of the structural problems when building with smaller wire (0.039” and 0.032”). The 1237 is a simplified design of those previous chassis, making it more triangulated, and with a more simplified wire layout, allowing for more design possibilities of the rear motor/drive assembly itself, and for the main rails.





Rear Motor/Drive Assembly Static Pans:


The lateral rear “wings” forward of the rear wheel wells on the first 1229’s were wire framed “holes” without the brass sheet pans filling them. One day after testing I noticed a pile of rubber and “track crud” loaded up on the wires in front of the rear tires, and I got to thinking about all the “rubber-crud bits” that had gone through the holes… How many times can the same crud bit go around the tire and get thrown back on the track in front of the tire again? Does it matter? As an experiment I took one of the 1229’s and filled the open area forward of the rear tires with a small cut-out of 0.010” brass sheet; the improvement was noticeable, and surprisingly quantifiable. The same was true when I did this to other 1229’s. And always with a fair amount of “track crud” on them. Originally these pans were about 7/16” (≈0.43”) forward of the rear axle center, but, since they are fixed, or static, pans, I did an additional experiment building another 1229 with the static pan framing only 0.30” forward of the rear axle center (they sit under the forward circumference of the rear tire, leaving only about enough space between the rear tire and the framing for a 0.047” wire to pass); this worked even better. They do need to be cleaned regularly. These rear static pans were incorporated into the 1237-Series.


Front Spanning Assembly / Front Wings:


Early attempts at all-wire framed chassis with a straight lateral spanner perpendicular to the centerline (with the guide tongue mounted atop) were structurally deficient, bending too often with front corner impacts (the most common). Alternatively/subsequently a V-shaped spanner was made, creating a guide well, and extending at a 45-degree angle to the “boxed” front wings. This structural layout has proven to be much stronger and effective in maintaining the guide and chassis front integrity.


Front Wings / Side Pans:


The 1237-Series simplified and standardized these assemblies. These two elements have a common medial line, making the side pans an extension of the front wings, separated by the front wheel wells with angled sides for better structural strength. The front wings are boxed between the lateral ends of the front spanner and the front wheel wells using a minimum of wires to attain the strength required, but keeping the mass low. The side “pans” are even more minimal, to allow for sufficient flex and body movement, while minimizing the chassis mass moving vertically.





Main Rails:


Design/build experimentation of main rails in early all-wire frames had brought one obvious conclusion: main rails that were straight and parallel to the centerline were structurally weaker than main rails that angled from the rear to the front, whether converging, diverging, or a combination. Long straight/parallel rails had to incorporate more wires to get the same strength, and were still more prone to being knocked “out of whack”, skewing the frame (askew... gesundheit…).


The 1219-Series had used a pair of main rails, direct or indirect, that converged rear-to-front (the same rear-to-front orientation will be used for main rail descriptions throughout) from lateral of the motor box to lateral of the guide mount on the front spanner.


The original “doodle” of what would become the 1237 ran a single center-line main rail from the forward apex of the triangulated rear motor/drive assembly to the apex of the triangle at the guide mount on the front spanner. It was significantly shorter, approximately 30%, than the previous 1219-series main rails. As simple as it was, it could solve a lot of the loading problems inherent in the longer converging pair of main rails. The question was stability…


Buttress Rails:


On the original 1237 “doodle” I drew in two more converging main rails as those on the 1219-Series, which made it a “tri-rail” chassis. They added the planar stability to the center main rail, but made the chassis basically another 1219-Series with a center main rail added, which was not what I was trying to design. On a whim I erased the connection points of these two rails where they met the rear motor/drive assembly, and made the notation, “articulate” with a question mark. This in effect kept the frame a single center main rail with the added stability it needed. Maybe. For lack of a better term these rails, “secondary articulated main rails”, would be referred to as “buttress rails”. Eventually the articulation would be devised as simply two small pieces of brass tubing, one soldered to the front of the rear motor/drive assembly, and the other soldered to the disconnected rear end of the buttress rail, with a piece of wire soldered inside on the buttress rail’s piece of tubing.





The Base 1237:


From my experience with previous designs it was apparent the 1237 would work as a frame constructed using 0.039” wire, and as a matter of discretion in the build progression the first 1237 would be 0.039” wire framed. The initial 1237-Cc2 frame spent about two weeks missing most of its superstructure as it was subjected to a lot of bending, twisting, prodding, and generally being stared at. After its completion the second 1237 chassis, the 0.032” wire framed 1237-Cc3, was built, and would be found to be not only structurally sound, but with better performance than the 0.039” wire framed 1237-Cc2, and better than all the previous 1219-Series chassis, 0.032” wired framed or otherwise.


Subsequent designs, builds, and testing would indicate the numerous components used to negate loading and harmonic problems with 0.032” wire framed 1219-Series chassis were not needed on the 1237-Series 0.032” wire framed chassis.


The basic 1237 design was complete, and the 0.032” wire framed 1237-Cc3 had confirmed proof of concept.


1237-Series Design and Build Progression:


The 1237 design has three basic and distinct framing components: 1) the rear motor/drive assembly; 2) the main / buttress rail assemblies, and: 3) the front spanner / front wings / side pans assembly. Variations could be made to any one or part of the separate components allowing for an easy progression of design changes.





And that is when the fun began!


Rick / CMF3

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#3 Eddie Fleming

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Posted 10 June 2020 - 10:37 AM

To me the trick is in tying the three components together. Some if not all the wires from each section must be integrated into the connecting section to form a strong joint and that is the magic part of this construction.


Drive on! :)

Eddie Fleming

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