Sick XXX-S

[OptimaMan]

Hey guys, just checked out the speed of my XXX-S with Lehner 1920 5 turn and 11.1 volt LiPoly cells. Pinion and spur combo is 27 tooth and 90 spur. With 2.5 inch tires, the top speed at the end of 250 feet was 61.9 mph!!! That translate to motor RPM of 51000 rpm (just at the RPM max). If I had more runway, I believe I could have gotten another couple mph more. The thing was nuts though - outta control.

-OptimaMan

[OptimaMan]

BTW, I got Kokam 3 cells packs that are at 1500 mah each. I put 4 of them in parallel so total capacity is 6000 at an average voltage of 11.1 volts. The thunderpower is 8000 mah, but max discharge is at 5C which is about 40 amps. Each of my Kokam packs are rated at 8C so it can deliver 48 amps continuous (at this discharge rate, I'm only getting like 85% capacity). I have an additional pack to raise it to 60 amps 7500 capacity, but didn't need to use it nor could I find the space to load it up in my XXX-S and GPS.

I'm starting to think that to go faster, you need a larger vehicle with more suspension travel. OR, a VERY smooth road. At these speeds, these small cars are VERY squirrely. I'm thinking a B4 setup with heavy oil and springs and lowered slightly with anti-roll bars will be just as fast with more control. Every little undulation of the road makes my car jerk around.

Stick around - the street in front of my house is supposed to be repaved this week. Then, I'll have about 400 feet of straightaway. I'll gear it with 30 teeth and let it rip. Maybe I'll be at 65...

-OptimaMan

[Kenny T]

If you need more shock travel or better handling look at the HPI super RS4. it's 1/9th scale I believe and it should handle the speed a lot better and there's more room to cram in that extra cell. ;)

[BJMFH1.01]

You ain't kidding about losing control in a BL touring car. At any speed above 50 my TC3 starts bouncing and darting all over the place. I either flip the car or end up in someone's lawn. I don't even try to run my BL TC3 on "regular" pavement anymore. Touring cars just aren't very practical for running on anything but a perfectly groomed surface.

My BL T3 is perfect for running on the street though. I've only pushed it to about 60 and it was very stable at that speed. The only problem I've run into is hitting a bump during hard acceleration. The truck's front end will lift up, flipping the truck instantly. It usually comes to a stop after skidding about 100ft on its' body. My body almost has holes worn though it thanks to all the skidding. :o

[munim]

Wouldn't cutting out the rear bumper = instant downforce?Should be more stable,

[HiAmplidude]

Man, I can imagine the insanity of a 1920/5 in a light car like that, on the equivalent of 9-10 cells! Absolutely nuts!

[OptimaMan]

Bad news... Took the car to the LHS to show them how nuts the car was. Doing donuts in the back and 2 of the tires rip right off the rims (I suppose those inside tires were probably close to 100 mph).

Go back inside the store, buy some foam wheel sets for the car, take it to the back again. Flying... catches some air, goes sideways and the the car floats into the air like a piece of paper being blown by a gust of wind. Fortunately, nothing breaks.

Drive around some more - this time, flying down the straightaway, musta hit a pebble or something, car is floating sideways again and BAM!! Hits one of those steel posts filled with concrete. Graphite chassis busted, steering busted, front and rear suspension cracked... but worst of all, the motor is busted. Hit the motor and all three metal plugs are ripped clean off!!! I might be able to fix it though... we'll see... Oh, BTW, the brand new foam tires I bought for 40 bucks... chunked all over the place.

I'm going to have to keep this TC only on smooooth roads from now on - no more parking lots with little cracks in the asphalt.

Next time, I'll run it in front of my house - they paved 1/2 of it just today. I'm going to gear it up a tad and see if I could hit 70 mph...

-OptimaMan

BTW, after running it like 3-4 minutes, the battery only used up about 1000 mah... total capacity of the pack is 6000 mah!!!

[munim]

Ouch!You need more downforce I'm guessing. If the body is more or less trashed, cut out the rear bumper, it's basically what real race cars use for down-force (ie ground effects).Basically, at high speeds, a vaccum will be created in the car (since all the air is exiting from the rear bumper) pretty much sucking the car to the ground. This will work best if your wheel arches are close to the wheel, and the body dropped as much as you can.

[OptimaMan]

Munim, thanks for the info... However, the whole rear end of the car is cut out - just like you said for ground effects. It works fine as long as the car is on the ground but a slight blip in the road and the body catches just enough air to get underneath it and float away.

[munim]

Yeah, that's the downside, just a little bit of air and away you go.Ever seen that Mercedes CLK GTR video?Ouch...

[Craps]

Do they make an 1/8th scale 4 wd electric buggy to run with the gas buggies? That would be an interesting project and would be interesting to compete with the gas buggies and not make a pit stop in a 30 minute main.

[Bob Ebophalus]

I'm fairly sure that no manufacturers make an 8th scale buggy for electric power, but lots of people have converted them.

[spenzalii]

Post some pics if you can, especially of the wiring of the packs. I would love to see how you wired that. If I can get a XXXS to go close to that, Nitro season is going to be very funny next year...

[OptimaMan]

I'll post pictures soon - as soon as I get the camera charged up. BTW, I got the XXX-S going 64.5 mph today with a small 1515 motor that spins at over 9000 rpm/volt with the lithium packs. It was geared 16/90 with 2.5 inch tires. Motor RPM is approx 89,300 rpm!!! Max RPM of this motor is 100,000 btw.

This car flies... literally. I keep on getting airborne and everytime I do, the car flips and tumbles like 100 feet down the road!!!

I'm going to have to make a custom body - just a rear wing, front wing and rollcage to protect the car.

[spenzalii]

16/90? Geez, why such a small pinion. I would have thought to go bigger to try to tame some of that torque...

I really would like to see the wiring of that. I think I can get the Kokam batteries from Tower, or just buy a 11.1 pack from ThunderPower Batteries. Eitehr way, it would make a fun race...

[NIC]

OptimaMan,

Those rpms must have sounded sweet :) !
The acceleration must have been great also. High "thrill-factor" I could guess (lots of goosebumps :) ) !
I wish you a longer straight though, 70 mph shouldn´t be a problem with abit more road, especially with the 1920/5.
Could you gear it anymore then 27/90 or is it stop there ?
What is the internal ratio on that car ?
I drove my TF-2 with 3,59:1 with the B40 6L and 6 cells to 64,5 mph. I think your XXX-S can take alot higher gearing with the 1920/5 then it has now.
I don´t want to encurrage (sp?) you to go faster (things are getting abit dangerous now) you might break some parts or hit something but I think much higher speeds are possible.

I´m abit surprised to here that you seem to have abit of a problem with the aerodynamics though, or is it just when you get a pebble or something under the front of the car that it catches air ?

Keep posting you experiences.

NIC

[OptimaMan]

Hello guys. Yeah, I know I geared it real short - that's so it wouldn't pull so much current and I also want to make sure the expensive batteries don't fry yet. So far, the batteries don't even get warm.

The internal ratio is 1.83:1 so with the 16/90, the FDR is like 10.3:1!!! I'll be gearing it taller and taller in the future. But, keep in mind, the 1515 6 is a high rpm low torque motor.

The 27/90 ratio is 6.1:1 ratio and I just need to buy a larger pinion. The XXX-S seems to almost have no limit and pinion gear size and going to a 35 tooth will yield a ratio of 4.7:1 and 70+ mph should be within range.

Regarding the torque with the 10.3:1... I need to take a picture of my street. When starting from a standstill, the black peel out marks are at least 50 feet long!!! Imagine that, this car burns rubber just accelerating!!!! Awesome eye-popping acceleration. I've never seen anything rocket out from a standing standstill. Just for kicks, I got a car that does 0-60 in less than 7 seconds. I'll get to 35-40 mph in a very short distance, but the XXX-S will already be at 60+ mph!!! Amazing - I only wish I had a digital camcorder so I could post it... maybe for X-mas, I'll get a digital camcorder and figure out how to post vids.

But, here's a picture of the car and the 3cells x 4 packs. Oh, one thing about Thunder Powers - they're rated at like 5C so getting an 8000 mah pack means you can safely pull 40 amps continuous. The Kokam cells I'm using are rated at 8C so I can safely pull 48 amps continuous using a 6000 mah pack. Kokam also makes 20C packs, but they REALLY expensive and you need like 10 of them to get 3400 mah pack!!!

[OptimaMan]

Hello guys. Yeah, I know I geared it real short - that's so it wouldn't pull so much current and I also want to make sure the expensive batteries don't fry yet. So far, the batteries don't even get warm.

The internal ratio is 1.83:1 so with the 16/90, the FDR is like 10.3:1!!! I'll be gearing it taller and taller in the future. But, keep in mind, the 1515 6 is a high rpm low torque motor.

The 27/90 ratio is 6.1:1 ratio and I just need to buy a larger pinion. The XXX-S seems to almost have no limit and pinion gear size and going to a 35 tooth will yield a ratio of 4.7:1 and 70+ mph should be within range.

Regarding the torque with the 10.3:1... I need to take a picture of my street. When starting from a standstill, the black peel out marks are at least 50 feet long!!! Imagine that, this car burns rubber just accelerating!!!! Awesome eye-popping acceleration. I've never seen anything rocket out from a standing standstill. Just for kicks, I got a car that does 0-60 in less than 7 seconds. I'll get to 35-40 mph in a very short distance, but the XXX-S will already be at 60+ mph!!! Amazing - I only wish I had a digital camcorder so I could post it... maybe for X-mas, I'll get a digital camcorder and figure out how to post vids.

But, here's a picture of the car and the 3cells x 4 packs. Oh, one thing about Thunder Powers - they're rated at like 5C so getting an 8000 mah pack means you can safely pull 40 amps continuous. The Kokam cells I'm using are rated at 8C so I can safely pull 48 amps continuous using a 6000 mah pack. Kokam also makes 20C packs, but they REALLY expensive and you need like 10 of them to get 3400 mah pack!!!

[OptimaMan]

Sorry about the double post guys... Oh, see the big piece of chassis missing - I broke it when I crashed it - but it's not a vital piece. Also, all four packs are wired in parallel.

[big1s]

sh1t:eek:

[OptimaMan]

Hey, this was my car a year ago - a broken down XXX-S due to crashing into that post!!! Hahaha