New hi-speed project - RC-Monster Forums

BrianG · 01:43 PM

I've done a few off-road conversions and now want something that I can hit really high speeds with (100mph+). I looked at a few electric sedan kits, but want something that is built more on a 1/8 b/truggy platform.

From what I can tell, the Ofna Ultra GTP would fit the bill. Plenty of chassis space, 2 speed, solid design etc. I was thinking of getting just the roller for now, but am thinking that getting the RTR and selling the parts I don't need (radio, engine, misc parts) might be the better way to go because it will have the body, steering/brake servos, and the 2 spd already installed. The RTR is listed as $320 and the roller is $190 at nitrohouse. I'll check a few other places first of course...

Then, to get the high speeds I'm looking for; use the two speed "tranny", 6s lipo, and a Neu 1512 motor set to run around 45,000 rpm. Since I'll be using the 2 speed, I think I'll need the Tekno clutch adaptor and just set the shoe spring very loose so it grabs right away.

Even though this vehicle looks to be the winner, I'm open to other ideas. One reason I like the Ofna one is the easy LHS supply.

This project would get started a lot easier/faster if I could get a few hits on this first (hint hint).

EDIT: Added info (more for me for future reference):

Tire diameter: 4.25"
F/R diff ratio: 3.1428 (44/14)
Stock 2 speed spurs (2nd,1st): 45T, 49T
Stock 2 speed CB (2nd,1st): 18T, 14T
Optional 2 speed spurs (2nd,1st): 44T, 47T
Optional 2 speed CB (2nd,1st): 21T, 17T

Ugg. To get a theoretical 110mph, I'm gonna need to get the optional spur/CB set, and get a 1512/2d (kv=2600) and spin that sucker at almost 58,000 rpm.

snellemin · 12.26.2007, 02:38 PM

Good to hear that you are going for high speeds now BG. It's hard going fast in a straight line, and gets your heart pumping pretty good. What tires are you planning to use?

lutach · 12.26.2007, 02:43 PM

Welcome to the club

. I'm glad I'm not alone in the chase for High Speed.

BrianG · 12.26.2007, 04:22 PM

Don't know about much other than the vehicle itself. From what I've heard, a good set of foams may be the best thing to use, right? Then, mounting them so they are perfectly balanced is imperative at the speeds I'm going to try to hit.

If I can't get a 2spd spur/pinion combo right to reach those high speeds, I might have to go with a single speed and use a very large pinion. But then, I'll need a larger motor (1515 or even the 1521) to generate the low-end torque since it will be geared so high.

I think I'm going to try to make the battery tray and the ESC/Rx mount out of fiberglass to keep the weight down. Should be interesting...

lutach · 12.26.2007, 04:29 PM

The 1521 would be a nice choice. I will use the 1521/1.5Y to make my speed machine.

jhautz · 12.26.2007, 04:34 PM

A 1521 spinning at that kind of rpm would draw LOT of current. Plan for some serious battery packs and asc if you want to pull 60K rpm with a 1521!!

lutach · 12.26.2007, 04:43 PM

I used my 1521/1Y with 37V and that was some awesome power. Too bad the drive train didn't hold up. The six gears inside the rear diff had a little melt down. I will eventually get this http://www.vertigoperformance.com/products_Lockers.html to save my diffs.

BrianG · 12.26.2007, 04:39 PM

That RPM was based on using the max size spur/CB setup available for the 2 speed setup. I was kinda leary about those high rpms as well. If I went with a single speed setup, I wouldn't be as limited by what 2 speed gears are available and use a larger pinion and/or smaller spur. That would bring the required rpms down a bit. Heck, I could even try a direct drive setup using an outrunner, but would have no gearing options and would need to control top speed via voltage and motor choice only.

squeeforever · 12.26.2007, 04:57 PM

I would not get the lockers. The will make it almost impossible to even get to high speeds. I had on in my Maxx and I couldn't hardly get about 50 with it.

lutach · 12.26.2007, 05:02 PM

Quote:

Originally Posted by squeeforever

I would not get the lockers. The will make it almost impossible to even get to high speeds. I had on in my Maxx and I couldn't hardly get about 50 with it.

Before I installed the buggy diffs in the truck, the rear truck diff had locked and it was actually working better then before.

lincpimp · 12.26.2007, 05:11 PM

Hey Brian, check this out: http://www.rc-monster.com/forum/showthread.php?t=9179

The car is very similar to the GTP in design. Plus it has a two speed! I am only trying to get to 70mph, but I can gear up if needed. You should have fun with it, my 10th scale tamiya that can do 80 is a blast, body choices will be critical, downforce and airflow management will be a big concern.

BrianG · 12.26.2007, 05:36 PM

Quote:

Originally Posted by lincpimp

Hey Brian, check this out: http://www.rc-monster.com/forum/showthread.php?t=9179

The car is very similar to the GTP in design. Plus it has a two speed! I am only trying to get to 70mph, but I can gear up if needed. You should have fun with it, my 10th scale tamiya that can do 80 is a blast, body choices will be critical, downforce and airflow management will be a big concern.

Actually, I was looking at that project a while ago. I liked the way it was built, but not sure how easy parts availability will be at my LHS. Of course, I could get them directly, but sometimes it's just easier to call up the LHS and tell them to get it for me.

lincpimp · 12.26.2007, 05:49 PM

Quote:

Originally Posted by BrianG

Actually, I was looking at that project a while ago. I liked the way it was built, but not sure how easy parts availability will be at my LHS. Of course, I could get them directly, but sometimes it's just easier to call up the LHS and tell them to get it for me.

I understand about parts. I have bashed the snot out of my ofna mbx buggy (identical mostly to the gtp) and it has never broken, only the front bumper cracked. I only bought the Yusa cause it was under 100 bucks shipped. I doubt that i will break anything, these vehicles are so solid being based off 1/8 scale buggies, almost indestructible! And the wear items will interchange, such as diffs, etc.

Are you going to use a clutch, or one of mike's lst 2 pinion adapters?

tashpop · 12.26.2007, 04:58 PM

i'm planning on going hv with my yosa rally project. i'll tell you my plans and maybe itll give you ideas or maybe you'll tell me im shooting myself in the foot.

pistix
12s air esc
12s a123
kb45xl motor 1000 or 1200 kv
2speed setup
what ever tires will hold up

i would realistically like to break 80mph with the setup, but idk if it'll do it or not. i haven't played much with the speed cal. so right now i'm clueless really. i have a kb in my very heavy emaxx running 6s2p a123 and i'm very impressed with that motor. i figured i would stick with it for this project because of price and the fact its got so much grunt.

BrianG · 12.26.2007, 05:10 PM

Sounds interesting.

You might want to play with the calc cause you'll find that you need quite tall gears, larger tires, higher voltage, higher kv motor, etc to reach those speeds.

Tires are gonna be tough. I don't think anything short of using foams or solid rubber will work since it will be really high to prevent ballooning.