* Chassis, with an Asterisk / 1245

[CMF3]

1245-Cc2

Long suffering readers of my posts here, and even the ones who gave up reading and just look at the pictures, are more than aware by this point that not only do I have difficulty writing short sentences, many of which with an overuse of accompanying punctuation, but, and not dissimilarly, I also just can’t seem to leave any given chassis design alone. It would be pointless for me to attempt to change any of these peccadillos at this late juncture in my existence, another more encompassing subject that also could be questioned as to having any point. The statement is pointless; the finger is speechless.

Any new readers to my posts here will probably have given up after that first paragraph.

While playing around with an asymmetrical retro stock car design adaptation of the 1237, that by that time in the design chronology was the 1244, I came upon the idea of articulating the “buttress rails” not only at the rear, as on the 1237 and subsequent designs, but at the front and rear. To do this would require another rail supporting the buttress rail from the side. The design concept was to more directly transfer any upward force on the outside front wheel to the inside rear wheel when cornering. To this effect, the supporting rails to the buttress rails were designed: 1) to extend from the forward apex of the rear motor/drive assembly where it attaches with the singular center main rail, and: 2) to attach to the buttress rails (upon which the front axle uprights are mounted) just below the line of the front axle.

I figure if the first paragraph didn’t send people screaming for the doors, that last one sure did.

Anyway, for those of you still left, it came out with five main frame rails meeting at one point, looking like some big metal asterisk, or

*

The first 1245 build would be a retro CanAm chassis, using the same dimensions as the original 1237, and also made of 0.039” wire for the framing, making it the 1245-Cc2. I wasn’t sure where the final weight would be on this thing before starting the build, so I opted for 0.039”, instead of 0.032”, guessing the 0.039 RTR car would wind up approximately 96 - 98 grams.

Okay, I apologize for making you read this much. Here are the pics:
















I had fun designing this thing, but it was a joy to build; the joy was the challenge. Plus it just looks pretty bizarre, even by my standards. I like it!

All the hoopla: All framing wire is 0.039”, except as noted. Side “pan” movement restrictors are 0.055” wire in 1/8” square brass tube. The wire at the fore of the “triangle” under the guide tongue mount is 0.047” wire. The 2x small pans flanking the forward end of the center main rail are 0.032” brass, and are semi-static, suspended with 0.024” wire which is soldered to the front spanning wire assembly only. The two lateral motor box assembly static pans are 0.010” brass sheet. The 6x body mounting 1/16” brass pin tubes are mounted atop 0.039” wires, the middle and rear tubes only soldered to the side “pan”. Guide tongue is a Slick 7 (S7-25) mounted on a 0.025” brass plate above the framing wires at the juncture of the center main rail and front spanning wire assembly. Motor bracket is a modified JK (JK-D3F122) and is mounted at an angle to achieve a non-hypoid gear mesh, but keeping the motor mass as low as possible.

As with the other “-Cc” designs, wheelbase is 3.875”, RAX-GPC is 4.875” (with resulting guide lead of 1.00”).

And, as it turned out, the RTR car came out to 97.5 grams. Any initial testing would be at this “as is” weight.

After last week’s deluge, I was finally able to get to Fast Eddie’s Raceway this week to try this chassis out on the Hillclimb. For comparison purposes, as far as chassis dynamics and handling characteristics, the 1245-Cc2 would be compared against the 1237-Cc2. As it turned out, I had raced the 1237-Cc2 in the last GRRR retro CanAm race (20 entries; qualified 2nd; finished 4th), so the performance benchmark would also be the 1237-Cc2.

Out of the box, the 1245-Cc2 was the fastest of any of my CanAm cars, not just the 1237-Cc2, but also the equally fast 1237-Cc3 and 1239-Cc3. This was despite having a motor that is noticeably lacking on the top end. Any straightaway speed/time the motor was losing was easily made up for with the chassis corner handling. This was even more apparent as I move toward the gutter lanes. I even went ahead and added the two small pieces of lead ballast to the front semi-static pans to get the weight up to 100 grams, and there was no noticeable effect on the chassis and car.

Okay. I have to admit I wasn’t expecting that. But I’m not complaining either. There just might be something to this design. Cool!

Obviously, this chassis will morph at some point, but for this brief moment…

Have fun!

Rick / CMF3

[badfast]

Beautiful CRAFTMANSHIP!! ....and a boat load of patience as well, I suspect. I've thought about trying to copy one of your designs but my eyes glaze over trying to follow the wire.

Don Weaver

[CMF3]

1245-Cc3

After testing of the 1245-Cc2 (0.039” wire framed), and months of testing, and racing, of both the 1237-Cc2 (0.039” wire framed) and 1237-Cc3 (0.032” wire framed), I felt it was necessary to build a 0.032” wire framed version of the 1245 design.

However, the 1245-Cc2 barely made the 100g minimum weight rule for CanAm cars, and my guess was that a 0.032” wire framed version would weigh around 8 grams less. The adjustable bite bar used on the 1237’s was not part of the 1245 design (but is part of the 1246), so that additional mass would not be available for this build (yet). To counter this loss of mass, it would be necessary to incorporate semi-static pans to fill the four central spaces adjacent to the 1245’s central main rail and buttress support rails.

And, hence, the 1245-Cc3:














Weird looking thing, isn’t it? No weirder than the 1245-Cc2, but weird nonetheless.

Being 0.032” instead of 0.039” required some changes, for examples: center main rail is 10x wire wide (instead of 8x); buttress support rails and buttress rails are 5x wide (instead of 4x); outer “pans” are now 3x wide (instead of 2x)… In fact, more wires everywhere in the framing.

The blah-blah-blah: All framing wire is 0.032”, except as noted. Side “pan” movement restrictors are 0.055” wire in 1/8” square brass tube. Buttress rail articulations are 0.055" wire inside 3/32" round brass tube. The wire at the fore of the “triangle” under the guide tongue mount is 0.039” wire. The semi-static pans flanking the center main rail and buttress support rails are 0.032” brass suspended with 0.024” wire. The two lateral motor box assembly static pans are 0.010” brass sheet. The 6x body mounting 1/16” brass pin tubes are mounted atop 0.032” wires, the middle and rear tubes only soldered to the side “pans”. Guide tongue is a Slick 7 (S7-25) mounted on a 0.025” brass plate above the framing wires at the juncture of the center main rail and front spanning wire assembly. Motor bracket is a modified JK (JK-D3F122) and is mounted at an angle to achieve a non-hypoid gear mesh, but keeping the motor mass as low as possible.

As with all “-Cc” designs, wheelbase is 3.875”, RAX-GPC is 4.875” (with resulting guide lead of 1.00”).

The semi-static pans added 8.4 grams of mass. The final RTR weight came out to 101.9 grams… but that was with a R-Hawk motor, and not the P-Dog’s I had previously been using… you know, since the P-Dogs will no longer be legal in 2017… and I completely forgot to factor in the R-Hawks weigh on average about 1.7 grams heavier… Oops… I’ll have to remember to factor that in next time… Duh.

First test runs of the 1245-Cc3 on the Hillclimb at Fast Eddie’s Raceway, comparing against the 1245-Cc2, the 1237-Cc2, and 1237-Cc3 (still in “race trim” from the last GRRR race), and after a quick addition of 0.005” to the guide depth, had the 1245-Cc3 running within 0.01s of the 1245-Cc2 and 1237-Cc2, and 0.04s of the 1237-Cc3, all three of which were running faster than the 1237-Cc3’s qualifying lap for CanAm at the last race. And that was with “just another” R-Hawk in the 1245-Cc3, while the others still had there “race” motors (instead of “practice” motors). The handling was as I had hoped and expected. That was good enough for me. More tuning and testing to come.

Have fun!

Rick