I read through that thread a while back. That is a crazy car. One of my favourite RC cars of all time. I couldn't find the video on youtube though. Any direct links?

http://www.youtube.com/watch?v=fphhgmQqOQ8

This is with a Hacker C40 12T on 7S, stock FT TC4 with a Stratus body. It ran 88 to 90 mph consistantly. 0 to 80 in 2 seconds.

Matt

I saw that but didn't think it was yours because of the body. You need to make a new video with the new body. Actually you probably don't cause you can only see the car in the video for a fraction of a second as it flies past.

The only parts left from the car in that video are the diffs and suspension. Every other part has been changed. Heck even the transmitter has been modded.

Matt

I am curious, why would say this when Nic Case did his 134mph run on a 1509 with 8S in a TC3?? Obviously the power from a 1512 is more then enough to hit 100!!

Nic is a good friend of mine. We have gone over this subject for many hours on the phone. He really lucked out with that setup! Even he says that. He had the sweet spot found for that motor and power system. Since then, he has not been able to duplicate that run! This year, after and entire year of R&D, his top speed was 126 mph. He went all the way up to a 1521 on 12S and still could not break that.

When we talked about S count, we both found that 6S seemed to be good for 90mph (we both went down that road), but 8S or higher was needed to break 100. Now, bear in mind, top speed is a funny thing. Nic also held (still holds?) the world record in drag racing running only 5S (I believe 114 mph in 132 feet). But, that car does not want to wind out more than the 132 feet.

This is such a funny hobby to mess with. I can tell you that a 1512 on 6S is capable of some high speeds. You may hit the perfect sweet spot. But, that is hard to do. I put hundreds of runs on my car with various setups (motors, chassis, suspension, gearing, lipos, ESCs, bodies, etc, etc, etc) and found that most changes netted a loss of speed. So, I wouls change that back and try something else. When I did make progress, it was one MPH at a time. Be prepared for ALOT of R&D.

Oh, Nic also ran his own hand made body with a super low CD for that car. That seems to be the single most important thing other than perfectly matching the motor to the pack to the gearing to the tires.

You will get there. It will take alot of time, though. That is the fun of this!

Matt

Wow, quite a few posts here while I was away!

ModMan, I'm glad you're here. This is my first foray into really high speeds, so the experiences from someone who's done it will be nice to have!

Your vehicle is probably a lot lighter than mine is going to be. The Ultra GTP is simply a 1/8 scale buggy modified for onroad use. I can see this thing weighing around 8lbs (128oz) RTR. TBH: I think 90-100mph would still be fun to see. I would like to hit really high speeds every now and then, but I will probably also be using it in parking lots and such for fun. From your thread, it looks like you need to make this specifically for high speed use only if you're really serious about it. Given that fact, I probably won't hit the high speeds I was hoping for (~130-140mph) since this will be doing double duty (playing and high speed runs). Plus, it sounds like this project will get VERY expensive VERY quickly if I try to go crazy.

After having the vehicle stripped down, I am pretty sure I will be using 10S (the most my charger is capable of), a 1515 or 1521 motor, probably the CC HV ESC, mechanical brakes, and the two speed tranny. I'll have two sets of pinion gears; one for the high speed runs, and one for more normal usage. I'll also have two bodies for the same reason. I'm thinking of making the high speed body modeled after yours, except made of 1/16-1/8" thick lexan for workability.

Anyway, I appreciate your input! Thanks!

Just the start of the pictures of this project. Not much to see here really. All I've done is strip all the nitro stuff off it and did a little modding to the brake area...

http://scriptasylum.com/forumpics/ultra_gtp_1.jpg

It all looks very good!

A couple things for you;

#1 I would just run it single speed. A 1515 or 1521 on 10S will be plenty of power to run without a two speed. Also, a two speed will tend to break the tires loose when it shifts. You will find that wheel spin management is critical with this and a two speed make wheel spin tough to control.

#2 I bet you can get your car to run solid 90 mph while geared for all around running with a 1515 on 10S. I would setup everything for 90 mph and move up from there.

Another thing to consider is, 100 mph is nearly twice as hard on the car as 85 to 90 mph. I know the numbers show that it should only add about 30% to 40% more drag. But, trust me, moving up 10mph is a huge thing. That is why I say to shoot for 90 first. If you shoot for 100 right off the bat, you are almost surely going to ruin alot of equipment and get very frustrated very quickly. However, 90 is not too hard to hit with the caliber equipment you are running and will really make you smile!

Also, most "Standard" RC tires will take 90 mph, but not 100. That is another reason to shoot for 90 first. You can move it up a bit at a time to the magin tripple digits soon enough.

Wait till you pull the trigger on that beast. It is like nothing else in the world. My top speed car is the only RC car I have (RC anything I have) that can draw this statement out of me "OK Honey, can you wait? I will be therer after this run!!"

Seriously, I cannot tell you what is was like when I got my car dialed. To give you an idea of the power, I gave it 40% throttle in front of my house as a sort of top fueller run and this is what happened; I pulled the throttle (again 40% throttle) from a dead stop. The tires (4wd) instantly broke loose and smoked (yes I said SMOKED) all the way down my street leaving long black marks down the pavement. The car accellerated like a freaking nitro burning blown funnycar. Then at about 80 mph or so, one tire shredded (Kevlar BSR radial tire). When the car came to a stop, one tires was blown, the other three were pretty worn, all the tires were too hot to touch, and there was tire dust and debris all over the inside of the body!

My wife was standing there and all she said was WOW! That thing is dangerous!

ABSOLUTELY!

My advice is GO FOR IT! Yes it is expensive (like nothing else RC you have run, no doubt). But, it is well worth it.

Matt

Here is my modded TX for top speed use. The steering throw is increaed 3X for finer control and the antenna is a 9db gain unit for longer range. I get 1500 feet out of this setup.

I do not mean to hijack this thread, though. Thsi is not my build up.

I am more than willing to answer questions, though. If you would like me to start my own thread, I will.

Matt

Thanks for the input!

I'll probably pick up the single speed eventually, but the two-speed kit is ~100 alone, so I got the RTR. It was more $$$, but I also got a body (for just playing around), servos, and radio (I won't be using an AM radio for anything BL, but maybe for something else). I figure I can get some cash back from the silly .28 engine and other nitro crap on eBay. :smile:

I already thought about the BL torque when shifting, but was hoping that if I dialed down the ESC start power (or whatever it would be called), it would help with that. It should also minimize the off-the-line power for less tire spin. Plus, I plan to use the exponential throttle function of my radio to give me a little more off-the-line control (hopefully).

I was concerned that by gearing so high, that the ESC would have trouble getting rotor position at start. Hence another reason for the 2 speed.

We'll see how things go as I build this up.

Cool!

I have never had any startup hesitation with my car. I have run both 1512 and 1515 with a HV110. No startup issues at all and that is geared at 1.9 to 1 (motor to wheel ratio). It is funny, my motor pinion is actually about 50% bigger than the spur!

Matt

Love the transmitter dude... gear reduction?.. :)

Belt drive, 16 tooth pinion, 48 tooth spur. :)

Matt

That is looking good brian. Can't wait to see the top speed figures. Mod man that radio is almost as crazy as your car.