anyone have one of those 1/18th scale rc buggies?

[audiolife 5,000+ posts]

http://www.castlecreations.com/products/mamba.html everyone i seen useing them uses 6800 on 6 or 7 cells and 8000 on 6 or lipo

 

[HiAmplidude 10+ year member]

http://www.castlecreations.com/products/mamba.html everyone i seen useing them uses 6800 on 6 or 7 cells and 8000 on 6 or lipo

I totally believe you, but I'm just saying that it's probably not optimal, based on my experiences. I've likely been through more BL systems than 99.9% of the BL folks out there, with a couple guys like krauterbutter overseas being the exception, and he'd agree with me. Higher RPM/V doesn't necessarily mean faster, and it almost never means snappier torque.

If you're talking real world voltage of 6 cells, then the 8k would probably be fine, hitting an estimated 53000 rpm at peak. (using 1.1v/c as the standard). But I still think it may be on the hot side. If using actual 8.4V under load (almost 8 cells) then, no way. Beyond too much.

 

[audiolife 5,000+ posts]

with the 2 lipos on a sponge tire rc18t with an 8000 it would do a wheelie from the word go. they showed me how to tweak the control setting and it was a bullet. sounded every bit as evil as i thought it could lol. 6800 is like 15-20 less but they have brushed motors that keep up with that unless that was 5 cell vs 7

 

[HiAmplidude 10+ year member]

If it were my money, I'd lean toward the 6800 on 6 good cells or 6.5V loaded from lipo (good for around 45000 RPM peak). Gear it a little taller than the 8k, and your speed controller will be loving life. Plus, you'll still be getting the same, if not better, overall speeds and performance, with longer run-time and cooler parts.

 

[audiolife 5,000+ posts]

you ever hear of united rc? those are the cells i was going to use. i dont want to do lipo seems they need more monitoring and im taking this thing on the road with me so i need all the help it can get without having to be "watching" it while it charges

 

[HiAmplidude 10+ year member]

6800 is like 15-20 less but they have brushed motors that keep up with that unless that was 5 cell vs 7

eh... I don't buy it. Anyone who thinks a brushed motor can keep up with a good BL @ 45kRPM hasn't seen it set up right or is spreading rubbish.

Here's a beautiful example. When I was going for the world land speed record for a full monster truck the results on 24 cells were:

B50 8XL 22/51 gears = 53.9 MPH

slower RPM/V B50 9XL 24/51 gears = 60.1 MPH (much faster under extreme resistance)

 

[HiAmplidude 10+ year member]

you ever hear of united rc? those are the cells i was going to use. i dont want to do lipo seems they need more monitoring and im taking this thing on the road with me so i need all the help it can get without having to be "watching" it while it charges

You are COMPLETELY correct. They need baby-sitting, but pros and very serious racers will be using Lipos because of the weight reduction and increased performance because of it. They're willing to baby sit them. There's a fire-hazzard too -- and you can "bottom out" the cell making it useless if you're not careful. They definitely have their ups and downs. In an ultra-light car/truck, I'd probably bite the bullet and go Lipo, but for the heavier stuff, it may not benefit it much (although every ounce counts when you're talking about speed).

Speed and run-time, controllability, reliability, are not synonymous.

 

[audiolife 5,000+ posts]

eh... I don't buy it. Anyone who thinks a brushed motor can keep up with a good BL @ 45kRPM hasn't seen it set up right or is spreading rubbish.

Here's a beautiful example. When I was going for the world land speed record for a full monster truck the results on 24 cells were:

B50 8XL 22/51 gears = 53.9 MPH

slower RPM/V B50 9XL 24/51 gears = 60.1 MPH (much faster under extreme resistance)

they were upper echeleon 1/18 th scale racers on a pretty big track. (on a track is diff) 1/10 scale cars gas vs electric the gas are faster yet they useually finish a lap or 2 slower in alot of heats probably more of a control issue. im not doubting your thought im just going by what i seen/ heard on one18th,com

 

[HiAmplidude 10+ year member]

they were upper echeleon 1/18 th scale racers on a pretty big track. (on a track is diff) 1/10 scale cars gas vs electric the gas are faster yet they useually finish a lap or 2 slower in alot of heats probably more of a control issue. im not doubting your thought im just going by what i seen/ heard on one18th,com

Even though it's been in RC cars for several years now, BL is still in its infancy for use in RC cars. People are proving people wrong all the time. That's kinda' what got me excited about it when I was into it. I literally destroyed every misconception about BL power in land vehicles that existed up to that point and loved every minute of it. I wrote new rules and standards. I found results where nobody else was looking. You can too. Just because someone "got it right" with a not-optimal setup doesn't mean that you should follow all the sheep that think it's the best you can do. I know you're not -- you're obviously assembling as much information as you can to make the best possible decision, unlike almost everyone else out there.

Often, little details like gear drag or other resistance can be the problem, when it had nothing to do with the power source.

Since you are talking about racing, though, I must confess that some times the less-optimal power solution can easily be the best on the track. For instance, using a way-too-hot motor may be smoother on the launch because of its strain. That makes it easier for the racer to control, and ultimately win the race. You don't necessarily want a torque monster in that situation. You want control. A comfortable/confident driver is a fast driver -- which holds true for real car racing and RC.

That being said, I submit. The more power-to-the-wheels solution I suggested may not be the best choice for your racing needs. It may be a good idea to go ahead and use the strain to your advantage with the very hot motor. There's no other real way to smooth out the power delivery of brushless electric.

 

[HiAmplidude 10+ year member]

... I should also add that sensorless systems will give you some headaches at starting speeds due to "cogging", especially when you're running a very hot low-winding motor. Check out sensored motors from Aveox (if they still do RC) and others like Novak. Not necessarily recommending Novak, but they do have a sensored BL system that's not shabby. Anything with a sensor system will have absolutely zero cogging, sputtering, etc. ever. It can't. The sensor knows where the motor position is and what direction it's turning at all times, in contrast to the sensorless BL system that relies on impulses of current through its 3 cables and a processor to figure out motor position and direction.

 

[audiolife 5,000+ posts]

Mini t's arnt as upgrdeable as most truck, there toys not hobbys if uwant a hobby go nitro or HPI electric

i just got my rc18t to whip the snot out of a 2wd losi 2wd (stock motor) electric race truck on dirt on a track lol you upgrade the steering on the rc18t (3racing aluminum ball bearing) and know how to set up ball diffs they (18t) freaking go where you point it and clear double jumps better than you would think. mine had a stock motor as well with a top speed of only 22 mph (was a handleing issue as to why it was faster around the track) you can also hop up a mini t to a great extent. i like the 18t alot better than a mini t as with bashing in a yard the 4 wd allows it to go get it in the rough stuff . i seen a mamba mini t hang with capet cars and also stay within a few feet per lap of 10th scale nitro sedans (full racing versions. was only losing 12" to at most 24" a lap and in the straight aways it was actually gaining lol)

 

[helotaxi 5,000+ posts]

Wow...I've been out of RC for only about 3 years and have no idea what you guys are talking about. BL setups were just being experimented with when I got out. The MiniT was being hinted at.

Last bit of racing I did was with an RC10TC3 which I still have, an HPI RS4 mini (I don't think that it has any stock parts left on it...) and Kyosho V oneRR (very heavily modded with a bunch of Japan market only parts), a Mugen MTX-3 (it wasn't available in the USA when I got mine in Japan, also heavily modded) and a heavily modded T-maxx with a 4 stroke in it.

I was cleaning out my garage and moving all my RC stuff around and thinking that I ought to get it all back in running order. I wasn't great at racing but I wasn't a total hack. One more thing to do when I get back from the desert. My wife says that my hobby is collecting hobbies, I think she's probably right, but she doesn't have any and is a total stress case. I do well at relaxing, seems justified to me...

 

[audiolife 5,000+ posts]

http://www.bigsquidrc.com/videos/ april 25 video of a rc 18t with a mamba lol look at the tires when it runs

 

[ryanroma]

Don't mean to jack your thread, but I'm selling a brushless 18T on ebay...

Just search for associated RC18T- Duratrax Evader BX

Both pretty highly modded.. Includes 4 transmitters and 4 batteries, 3 for the evader, 1 for the 18T.

 

[audiolife 5,000+ posts]

i moved up to 1/8th scale nitro and 1/10th scale electric trucks but i am sure when people see what these can do it might spark intrest...