Nineball

Get a carbon chassis, they said. Add a bunch of weight, put it low as possible, they said.


Turns out CAD hasn't changed much in 15 years. My day job already involves mapping things out and putting holes in exact places, so this was really in my ballpark. Sendcutsend.com did the cutting and it looks like I planned it out right (holes appear to line up, so far). Looks like a few hours of wrenching over the weekend and I should be able to see what it does.

rskoncepts

iTrader: (37)

Looks awesome. So lucky you have resources. I'm amazed that even with mid motor, huge batteries all the way to the shock tower, servo on the bumper, they still have to add weight to the bumper and more. Tires and traction has come a long way.

Nineball

Well, for the record, it didn't take much. I just used FreeCAD, exported the designs as .dxf, and gave them to Sendcutsend.com. They have a minimum order of $29, the whole setup was about $35. Chassis and rails are 3.2mm 6061 aluminum and the transmission riser is 3.0mm steel (almost as heavy as brass but way cheaper).

If you have a metric ruler and some free time, you could make a chassis. There isnt anything odd, every hole will line up to a nominal measurement. Or at least that's how the associated parts work... the holes for the transmission are all increments of 10 or 12mm. It's no wonder there are so many chassis out there, it's super simple to make one.

Traction is an odd component. Over the last two years, I've seen things shift a lot. At first, it was all about getting as close to to the weight limit as possible. Top runs were around 2.2sec and weight was the enemy. Then, the last season was all about prep... technique, formula, timing... a lot of work for a toy car. I try to be realistic about these things.

Anyway, as I started to try tire prep, I quickly realized that it isnt all about getting sticky... you can have industrial grade adhesive on your tires, but they wont grab unless you put some weight on them. So this is my experiment.

Nineball

Coffee + wrenching...

Toaster556

I gotta ask, are those brass airline fittings and plugs on your rear arms? How do they work for you?

fyrstormer

iTrader: (1)

Assuming the suspension is slammed as one would expect for a drag racer, getting a carbon chassis is antithetical to putting weight as low as possible. I mean, the chassis on a drag car is already about a quarter inch above the ground -- you can't put weight lower than that without guaranteeing it will smack into pebbles and whatnot. If the minimum weight limit has enough headroom, I'd honestly go with a sheet-steel chassis plate instead of carbon or aluminum.

Also, switch the battery cables to connect directly to the battery with bullet plugs, instead of having that bullet-to-EC5 adapter in the middle. Getting rid of the EC5 plug might not increase peak amperage much, but every little bit helps.

Nineball

Yup, right from the plumbing aisle at home depot. 3/8" threaded brass cap, plug, and an extra reducer. Each side weighs about 20g. Putting them on the suspension arms makes them unsprung weight. They definitely help the car launch harder.

Sheet steel is a little too heavy... aluminum is roughly twice the weight of carbon fiber, so this is a pretty good in-between. I'm also pretty sure a 540 motor would struggle with a 10lbs car, so I'm not trying to push it too far. Mostly, this eliminates some chassis flex and I can ditch the waterfall brace. Changing up the servo mount was a bonus.

I've heard about going direct wire, but it's actually a pain for race day inspections and batteries are all going QS8 now. EC5/XT90 are technically 4.5mm bullet connectors in a housing anyway, so to me, it's to-may-to/to-mah-to.

rskoncepts

iTrader: (37)

Hope you have some test results (GNSS or Timeslip) before the transformation and then the after. A lot of the fast cars are very heavy (11K mah batteries up to the shock tower, servo on the bumper, brass weights on the bumper, etc). You might be on to something!

Nineball

I don't have any GNSS results from before, but I do have some time slips from last season. Running just WD40 for cleaning tires, I had a lot of passes around 2.5-2.7 with the best/fastest being a [email protected] Iowa cornfields see nothing but wind and dust, getting good clean runs is hard. I even managed a perfect, full-throttle-from-launch run... into a 30mph head wind... for a [email protected] That was all with a 4.0t, 15° can timing, no boost, +20° turbo, on 23/87 gearing. So... I built it slower than most would. Buuuut I'm hard on the throttle and tune it to not be as twitchy as I am. I rarely get to full trigger before the end. There's probably a DRK in my future, I hate my RS pro and I'm lucky it hasn't exploded yet.

Now I'm adding 20° boost from 10k-max rpm to finally get the rest out of the motor. Also went down a tooth to a 22t pinion. Minor changes, really... but it should be able to match what it did before, at least.

rskoncepts

iTrader: (37)

Bummer about your cornfield dust.
I run a 4.5T right now and have gone 2.36/63 on blinky. Stock DR10 with a DRK but all tuning done on the radio. I don't use the stages and no timing added for now. Working on gearing and suspension first.
I like Tekin but you have to treat it kindly. It seems to only likes boost or turbo and not both. I use the RS Pro BE also. Mainly because I'm not using low turn motors yet.
My suggestion is to put the motor back to 30. Motors seem to not like less timing. I like using turbo mostly because it’s added after you reach full throttle. I've used PB Blaster for conditioning (smells though) but now use a conditioner (Tony Tonn or Frank Greer) and clean with Naphtha. I’m using Reactions with foams on Showtime rims.
What radio are you using?
We can discuss in Messenger or PM if you like. I'm definitely no expert.

Nineball

I thought I put the can timing to 20°, as that's what the manufacturers seem to be suggesting when you add a lot of electronic timing... but I guess I didn't. I also know traction is my biggest problem and I should be running a tire prep, but I wanted to see what I could do without it. Every time I added weight, the car got a little faster. So that's how I ended up here.

Locally, we had trouble getting prep last year. Reaction Time or SXT was it. RT works great, but IMO, the track was never clean enough to use prep properly. Then I did some research on chemicals and figured out WD40 is about 90% naphtha, which is a petroleum distillate... and really should work quite well on it's own. I also tried Gremlin Goo, but it was... dare I say, too sticky? Some preps just take a particular treatment to work right. I'm going to try the pink lemonade, but RT just jives with our temps and track conditions, it seems.

Otherwise, to answer your questions... I run foamless reactions, the old skinnies. My radio is a Sanwa MX-6.

Toaster556

Interesting, I may have to try that on my next round of changes.

If you're having trouble getting prep, I run a homebrew mix called "Tree'd". It's basically 3-4:1 mix of isopropyl 99% with pine rosin, and works pretty good locally. I clean with non-chlorinated brake cleaner between passes and reapply, and condition with simple green. Also running standard reactions on showtime rims with 30cc of air

Nineball

How do you feel about the pressurised tires? Do they work noticeably better than the alternatives?

I wish someone would make a proper belted wrinkle wall but that might be asking too much from a tire so small.

We're due for a very warm but windy weekend... maybe I'll try to get some test passes.

Toaster556

With 30cc of air, they hook much better than airtight with no pressure or no foams on regular width rims, but they are incredibly finicky to glue up. It took me several attempts to get a good news seal on both sides, even with bands and a centering jjg. I think it also helps keep the belts alive longer than running no foam/no pressure, as the few reaction belts I've seen broken locally have come from wrapping the tires like a bias ply slick off the launch. Otherwise, I'd be interested in the Cyrul 3DFX 2.2/2.2 bead tire

rskoncepts

iTrader: (37)

I've made air tires but haven't tried them yet. Have to learn to get the pressure even in both tires. Interesting that you use volume of air versus pressure. Might have to try that. What do you use?
I'm running foams and found them to be very consistent. I just condition and clean with naphtha. I couldn't get the no foams to be consistent. Cyrul setup looks promising but $$$.