3 Cars - Down to the Wire! (Weigh-In is Tomorrow)

[Scrollsawer]

Well, work is doing a real number on my car builds this year. Managing customers in all four corners of the globe (long hours), and a daughter who decided last-minute to enter a car, we're coming down to the wire on these three car builds.

'Weigh-In' and 'Car Impoundment' is tomorrow night, and we still need to polish the wheels & axles, assemble the cars, and tune / glue-in the axles. Oh yes, and we've got one car that is notoriously close to being at weight (sans graphite and tuning). Good times...

Here are the cars:


The 'Pink Copperhead' car (obviously my daughter's) is going to get valentines hearts added to it tonight (no weight issues with this car - plenty of room for final weighting). 22 tungsten cubes around the rear axle.


The 'Fire & Ice' car is also good, from a weight perspective (4.8 oz., projected weight after assembly - tungsten putty to bring to weight). The COM is between 1/4 and 3/8 inches. 23 tungsten cubes around the rear axle.


The green 'Minecraft Creeper' car (it's a VERY popular video game with boys right now) is the one that's got me concerned. When weighed on a scale (with the wheels and axles included, but not yet assembled, or any graphite added) comes to 4.98 ounces. I will need to consider sanding what's left off the bottom to try and gain a couple more grams back hopefully. The COM is between 3/8 and 1/2 inches. 23 tungsten cubes around the rear axle.

Input / Suggestions / Criticisms are most welcomed.

Thanks,

Scrollsawer

[Speedster]

Beautiful cars. Very aggressive COMs. I'm eager to hear how you do. Good Luck.

[Scrollsawer]

Speedster, will post assembled car pics. tomorrow before car impoundment, and actual results on how each car fared sometime over the weekend.

[DerbyDash]

I too am interested in the results with the COMs where they are. Our car isn't as thin, more like a wedge, but COM is currently at 3/4" which is about as aggressive as I am willing to go (at least for this year!)

Based on other posts about wobbling issues, I get concerned in having a more aggressive COM without being able to test it on a track.

We won last year with something a bit over 3/4" and it was rock solid....never lost a race, no wobbling and won by over a car length every time.

Good racing!

[Scrollsawer]

Yeah, I'm reserving the right to make final weighting adjustments (using putty) under the front axles to pull that COM out just a wee bit, if needed. I still need to measure the COM with the axles and wheels installed, but 'all things being equal', I'm assuming it will be close to where it is now.

Scrollsawer

[Noskills]

Super thin and slick cars. I agree that the COM would make me nervous. Like the mindcraft car. My son has a Zombies vs Plants car, but that game is so yesterday as he play mindcraft now. Do all these cars have the double row of 7 cubes behind the rear axel? Let us know how the tuning goes. All 3 wheel RR I assume.
Noskills

[sporty]

They look fantastic. Im really impressed...

Sporty

[Scrollsawer]

Thanks Sporty, they will look much better with the wheels attached. And were-weighed the Minecraft car. It's actually 4.90 oz., so we have a whopping .10 oz. to get it to weight (sigh of relief). Noskills, yes, they are all canted, rears, RR, and raised wheel. FB and others opinions on the 7 cube weighting convinced us to change the cars weighting, so now they are all 12 cubes in back, and the rest in front of the rear axle.

Scrollsawer

[Scrollsawer]

Not FB, FS, and others advice (especially Sporty's) really has helped us. Yes, the COMs are extremely aggressive, but I am hoping that smaller wheel gaps, and a little more 'steer' into the rail, will do the trick.

Scrollsawer

[davidwilkie]

Yeah, I'm reserving the right to make final weighting adjustments (using putty) under the front axles to pull that COM out just a wee bit, if needed. I still need to measure the COM with the axles and wheels installed, but 'all things being equal', I'm assuming it will be close to where it is now.

Scrollsawer

I think when you add the wheels and axles the COM will move considerably forward. It's simple physics. The rear wheels and axles will be just a 1/2" away from the COM, but the front ones are like 4" away, so they will have 8x the effect on the COM as the front ones. That explains how you have such a small COM with what looks like a design consistent with 3/4"-1"-ish COMs.

[Curse You Red Baron!]

I saw the effect that David mentions... I saw my son's com go up at least 1/8 of an inch, if I measured correctly, once the wheels were added - I wasn't being overly precise with the initial measurements.

[Noskills]

Don't you guys measure COM with the wheels on?
Noskills

[Scrollsawer]

Noskills, I'm relative 'newbie' to advanced car build principles, so I probably shouldn't quote COMs until the car is finished.

I will repost the cars pics. Later today with revised COMs. Learning a LOT on this board, thanks to you seasoned veterans!

Thanks,

Scrollsawer

[Curse You Red Baron!]

Noskills, yes, if I quote a com it's with the wheels attached. However, I do measure the com before I attach the wheels just to see if I'm in the right ballpark, because I prefer not to be messing with weights and glue once I have the wheels attached... at that point I try to be close enough that I'm just adding on lead tape for final .1 oz or so.

Of course, sometimes in the rush of the build I'll forget things that I should keep in mind - like how easy it is to balance wheels on the car even if they are not attached, to get a truer picture of the final com

[Lead Reindeer]

Love the digital camo. Did you use a stencil or did you freehand mask that pattern?