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Thread: F1 or another / A306

  1. #1
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    F1 or another / A306

    A year ago I built my last F1 ret-ro chassis, the A305; it was the first F1 chassis on which I incorporated “damper” main rails (“Z-rails", or whatever people want to call them). I’ve raced it twice for a first and a second. It just handles so much better than all the other F1’s that it literally rendered them obsolete.

    So, now that I’ve ascertained on the CanAm/GTC chassis the narrow center-guide section of the 1307-C and 1309-C (the center rails of the center-guide section consisting of only four 0.047” wires side-by-side) was an improvement over the standard width center-guide section on the 1306-C, I figured it was worth a try to build another F1 chassis still using the damper main rails, but also using the narrow center-guide section.

    But I also decided it was time to try using a different body; and I prefer to build the chassis on my F1’s to fit a specific body. Previously I had very good success with the TrueScale Matra (TSR-20) body for the other chassis; now I wanted to try to use the TrueScale Lotus 49 (TSR-21). While both bodies are very low profile, the structural dimensions change: the Matra chassis had a Wheelbase/RAX-GPC of 4.125” / 5.0625”; the Lotus 49 would be a little shorter at 4.00” / 5.00”. And then there are those little front wings on the Lotus. Seemed a shame just to have them sitting out there without any chassis underneath… So, I extended the chassis out to them; of course I was restricted by the maximum chassis width of 1.625”, but I was still able to get some wires out there under them (for no better reason than I wanted to, and just maybe take advantage of what little downforce the body front wings might create by having them rest on a chassis component).

    The only other major change I would incorporate into this design was the use of an angled motor bracket… There will be more on this subject when I post up the 1310-C chassis builds. Suffice it to say it achieves the same effect of a non-hypoid bracket while keeping the motor mass as low as possible… Sorry, but this one isn’t fully sorted out yet…

    Here’s the ever popular (at least among those as boring as myself… ) diagram, except now it is new and improved in living color! (Please try to contain your excitement... )



    Bold lines still show where adjacent section wires are not soldered together (like “cuts”); the colors show the wire framing components of the various sections:

    Motor Box / Rear Axle Assembly - blue-violet
    Center-Guide Section - purple
    Main Damper Rails - olive green
    Front Wing Section - indigo
    Wire Side "Pans" - orange

    Let me know if this helps…

    Anyway the A306 came out looking like this:















    All the usual specs: All structural framing wire is 0.047”. Outer side pan movement restrictors are 0.055” wire in 1/8” square brass tube. Center pan down stops, rear damper rail down stops, and center-guide / front damper rail up stop are 0.032” wire. All spring wires (rear damper rails, front damper rails, center-guide section, and rear pin tube mounts) are 0.024” wire. Pans are 0.010” brass sheet backed with 0.039” wire.

    Motor bracket is a modified JK (JK-D3F122). Guide tongue is Slick 7 (S7-25) mounted on a 0.025” brass plate above the center-guide section 0.047” framing wire.

    Maximum width is 1.625” at front wings and 1.60” between the front and rear tires. As pictured the roller chassis is 62.6 grams; that should put the RTR car at about 92 - 93 grams. Dang, still got to add another 7 - 8 grams to get it to the _______ (fill in the blank) minimum weight, but, while annoying, I found the added mass on the A305 didn’t screw up its handling (sure didn’t help it any either…), so I’m hoping for the same here.

    With a little luck I’ll be painting up the body and giving the A306 some runs against the A305 at JSCG this Saturday.

    Rick

    In the meantime, I do not believe I’ve ever posted a build sequence on an F1 chassis…
    Last edited by CMF3; 05-24-2011 at 05:13 AM.

  2. #2
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    A306 Build Sequence, Part 1:

    As usual, all wire used is 0.047” unless otherwise noted. Photo captions are above each picture…

    Picture 1: Prehistoric Champion Align-O-Jig (‘cause I’m cheap…) set up with 7/32” rear axle tube, and front spanning wire set on layout.




    Picture 2: Four damper main-rails (two on each side; all 1-bend with an upright bend) running from the rear axle tube forward but NOT soldered to the front spanning wire.




    Picture 3: Next part of the damper system main rails is a 1-bend rearward-running wire soldered to the front of the first two wires (again NOT the front spanning wire).




    Picture 4: Finally a 2-bend wire is soldered to the rear of the rearward-running wire, and soldered to the front spanning wire. The jig has been removed to better see the completed damper main rails.




    Picture 5: Innermost wire (2-bend) of torsional wire side pans soldered to forward portion of outer main damper rail wire.




    Picture 6: 1-bend wire adjacent to innermost side pan wire.




    Picture 7: 3-bend outermost wire of side pan (extending to wing front).




    Picture 8: Final wire (1-bend) soldered medial to outermost wire.




    Picture 9: 1-bend wires added to front spanning wire; straight wires added at outermost front wing.


  3. #3
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    A306 Build Sequence, Part 2:

    Picture 10: Time to build the center-guide section. This is assembled inside the frame, but not attached at this time. First are 2-bend wires (with 1 upright bend) running from the rear axle tube to another approximately 0.40” long piece of wire, forming a “T” at the guide end. The flanking 2-bend wires can be seen at the photo bottom.




    Picture 11: The center-guide section frame completed. The result is a section that is only four pieces of 0.047” wire wide along its length.




    Picture 12: The frame wires for the center-guide section pans. Each of these are two 1-bend pieces of 0.039” wire, made to fit between the center-guide frame and the damper wires.




    Picture 13: The frames are used to pattern a piece of 0.010” brass sheet that is cut out and soldered to each frame. (Yes, due to different rate of expansion/contraction of brass and steel, they will warp a little when soldering, but are easily flattened.) The pans are trimmed to ensure a good fit; there should be minimal space between the pans and surrounding framing allowing free movement, and soldered to the center-guide frame. They are only soldered behind the “T” to approximately 0.75” along the four center wires, so the back of the pans will move freely.




    Picture 14: The 0.025” brass “sandwich” plate and guide tongue (used; I forgot to order more…) attached. Center-guide section pan 0.032” down-stop wires attached (in retrospect, I should have done these later…)




    Picture 15: Center-guide sections soldered in place; center-guide / front damper rails up-stop wire (0.032”) soldered in.


  4. #4
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    A306 Build Sequence, Finale:

    Picture 16: Center-guide section and front damper rail spring wires (all 0.024”) soldered in place and resting on up-stop wire.




    Picture 17 & 18: Motor box wires, rear gear guard and rear axle tube spreader wire complete the rear assembly.






    Picture 19: Rear axle tube cut. Modified motor bracket in place. Pan movement restrictors in place (1/8” square brass tube soldered to motor box; 1-bend 0.055” wire soldered to rear of side pans). Rear damper rail down-stop wires (1-bend, 0.032”) and spring wires (0.024’) in place.




    Picture 20: “Raised rail” attached to outer wire of side pan rears (between pan restrictor wires and rear pin tubes). (Note: “Raised rails” keep the body from folding in on top of the chassis.) 1-bend wires added just inboard of outer pan wires to restrict inward movement of spring-mounted pin tubes. Rear spring-mounted body pin tubes (1/16” tubing with a 1/16” collar soldered to 0.024” wire) soldered to pan wires.




    Picture 21: Spanning front axle uprights in place.




    Picture 22: 2x “raised rails” added above outer pan wires; middle and front pin tubes soldered atop “raised rails” (allowing for clearance of front axle uprights, guide tongue, etc.).




    See, no “smoke and mirrors”…
    Last edited by CMF3; 05-24-2011 at 05:28 AM.

  5. #5
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    A306 Update

    One quick bump of this chassis thread before it rolls off with the tumbling tumbleweeds into the western Web wastelands…

    More testing to come for sure, but here’s the skinny on this puppy. As I mentioned, I ran the A306/Lotus versus the A305/Matra. In the center lanes the A305 is a tick faster. Moving to the gutter lanes the A306 is decidedly faster… in fact it is just as fast in the gutters as it is on the center lanes… Have to check this out further. I’m guessing the slightly shorter WB/RAX-GPC on the A306 allows it to handle the greater range of curve radii encountered in the gutter lanes. If I find anything out of interest I’ll post… Otherwise…

    Happy Trails to you…”

    Rick

  6. #6
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    Thumbs up


    I wish I could "picture" a chassis as you do. I might be better at it.

    OLPHRT
    PHIL I.

  7. #7
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    My bad...

    A friend of mine has brought it to my attention that some of the newer readers of my threads might not be up on all the lingo being tossed around, and should not be punished by having to search through my proliferation of overly long posts. I wouldn't even wish that on people I don't like... (However, the unstable few fellow fingerburners out there like myself have probably aleady done this...)

    Leftovers from my graph paper doodlings are some abbreviations, that have for quite a long time and continue to appear on all of my chassis diagrams:
    "C" is the longitudinal centerline;
    "RAX" is the rear axle centerline;
    "FAX" is the front axle centerline;
    "GPC" is the guide pivot center.

    So the "WB" is the wheelbase, or RAX to FAX distance. I imagine this one was a "no brainer" or a "duh". Except for its application to chassis where the front wheels play some significance to the handling characteristics, as in ret-ro, the magnitude of significance and effect seems to be somewhat debatable, as most "evidence" appears to be anecdotal. (It would be nice to see some industrious type build three identical chassis where the only difference was the WB, say 3.875", 4.00" and 4.125"...) And when building "no-rules" chassis where the front wheels are merely along for the ride, this value is completely insignificant.

    More importantly, the "RAX-GPC" is the distance from the rear axle centerline (RAX) to the guide pivot center (GPC) measured along the longitudinal centerline (C). Some builders like to use the term "guide lead" instead, which is the distance from the front axle centerline to the guide pivot center; this value is absolutely meaningless without the wheelbase being added to it. The entire function of any chassis is based around the triangle(s) formed by the rear axle centerline width and the GPC. How we hang the functional bits inside and outside that base is really all the fun us fingerburners are up to... Anyway, I include the RAX-GPC instead of the "guide lead" so y'all don't have to do the math... (Again, wouldn't it be nice if the previously mentioned industrious fingerburner made three or more identical chassis with different RAX-GPC's? Though more the procrastinating type, I might even have to get in on this one... )

    "...until we meet again..."

    Rick

  8. #8
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    Thanks for this, Rick; your unique and thoughtful approach to Ret-Ro is much appreciated by we Engine-Earring types, and a table of Acro-Nyms is a big help in understanding.

    Duffy

  9. #9
    Join Date
    Nov 2007
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    Rick,

    H'mmm new build, very low slung, almost no frontal area. I'll bet it slips through the air quite easily.

    Many eons ago, I showed up at a race with a Formula 1 car. I had lowered the body down as fast as it would go, resting on the top of the 16D motor. The guy doing tech passed it as there was nothing that did not meet the rules. He did make a point of holding it up and mentioning, "This car is setup to run 1/16 of an inch BELOW the track's surface!"

    With all the build sequences and such, I'm thinking it's time to build one for myself.

    So you are saying that RAX+FAX+GPC=5.00 on this build and that GPC=1.00?

    Nice job BTW. I'm looking forward to August and September Formula 1 races at ASR and The Viper Pit!
    Florida Slotter, aka Marty Stanley,
    A "Double 60's" Slot Racer
    Killer X Raceways Team Racer

  10. #10
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    Yeah, I probably should mention the TrueScale Lotus 49 body leaves little room under it for the motor (I knew this prior to this build from a no-rules A205 chassis that used the same body), especially since I used an angled motor bracket raising the rear of the motor. So anyone out there thinking of using this body should try to cut the rear as tall as possible (which ain't much) to start, then trim down to fit.

    And on the nomenclature, RAX and FAX are lateral lines to the longitudinal centerline, while GPC is a point on the centerline, and technically none have a dimension. The dimensions are the distances between them. On the A306 chassis:

    RAX-GPC = distance, rear axle centerline to guide pivot centerpoint = 5.00"

    WB = RAX-FAX = wheelbase = distance, rear axle centerline to front axle centerline = 4.00"

    FAX-GPC = "guide lead" = distance, front axle centerline to guide pivot center = 1.00"

    [RAX-GPC] = [WB] + [FAX-GPC]

    Sorry for any confusion...

  11. #11
    Join Date
    Nov 2007
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    If only my 8th grade Algebra teacher could have foreseen this. The subject would have become so much more popular or interesting, whichever works for you.

    Actually it is a very definite way to describe the relationship between wheelbase / guide lead.

    Thanks for sharing this.
    Florida Slotter, aka Marty Stanley,
    A "Double 60's" Slot Racer
    Killer X Raceways Team Racer

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