xjman

Recently I decided to build a car for on road racing. I started with the TC5 because I've had a TC4 and loved it, so I figured for a guy who wants to build a track only car the TC5 would be a good bet.

The questions I have are more about electronics in general though. I know I want to go brushless, but I'm not exactly sure how to match a brushless to a brushed motor. My TC4 is running a Mamba Maxx with a matching castle 5700 motor. I've been told its equivalent to good 10 turn motor.

Ok, so thats awesome, but what do I look at to compare?

Second. I've been reading some of the IFMAR and ROAR rules to determine a body and tire sizes. They body was pretty self explainatory, but the tires are a bit confusing. I don't see a max tire width with roar rules, and IFMAR seemed to say one width in one place, then another just below that.

Also, can anyone point me to some information on choosing tires? I've had decent luck with HPI X-Patterns on my TC4, but figure a track only car may benefit from a different choice.

Thanks for any help.

xjman

No one can give me an idea on how I can tell what brushless is similar to X motor?

Bruce Grembowski

iTrader: (6)

I'm not familiar with the TC4/TC5, but folks at our track run the 1/10 sedans. I'm running 12th scale. I did have a brushless in my 12th scale for a bit but went back to brushed for the weight. Lots of guys are running the Novak brushless motors in the 1/10 sedans, though. Novak brushless motors that have "turn" ratings can be compared to brushed motor turn ratings like this:

The SS10.5 is equivalent to 19T brushed; it's similar to their SS4300
The SS13.5 is equivalent to 27T brushed, or stock

The other rating I've heard about for brushless motors is kV (kilovolt), or RPM/Volt. The 10.5 is rated 4200, and the 13.5 is rated 3300. They have a motor with a 5800 kV rating, which is shown as 7.5 turns, but I don't know what that would equate to in brushed motor turns. Castle's web site shows that their 5700 equates to a good 9T or 10T brushed motor.


But if you are going to do on-road, where are you going to do it? You can check with the track, and they should be able to help you.

My advise, from my limited experience, would be to get a combo from Novak that supports LiPo in addition to 4-6 cell NiMH packs, like one of these two listed on the Team Novak web site:

GTB/SS10.5 Pro Brushless System—this system is ideal for use in “SS4300 class” races with performance similar to 19-turn brush motor. (#3010)

GTB/SS13.5 Pro Brushless System—this system is ideal for use in Stock class races with performance similar to a 27-turn stock brush motor. Its lower speeds provide better vehicle control for newer drivers, and longer run-times for those wanting to get valuable “practice” time on the track. (#3013)


HTH,
Grem

xjman

So, basically there isn't any clear cut way to compare speed of a brushed and brushed motor?

Any idea on the tires? I think 26mm will be the widest I can use on 1/10 sedan.

edseb

No there is no way to compare the two systems accurately. What you will see from the manufacturers is an approximation. If any one says any more than that, they are wrong. Brushless and Brushed have fundamental physical limitations that will never make them comparable; sorry. You can get close, but the power band is so much different, and efficiency so different along with other tings, it can never be a true comparison.

ROAR does have rules on tires, depending on what class (foam or rubber), etc. Rubber class is more strict, but foam sedan (usually only used on carpet) has a max width of 26mm, but it is common to see 24mm for efficiency, etc.

edseb

I know you are just trying to give him some general information, but there are some things that may be misleading. For one, a Brushless and Brushed motor comparison is always an approximation, and never equivalent. Yes the SS10.5 is similar to a 19t brushed, and evolved from the SS4300. When Brushless was first introduced, it was illegal to use sintered rotors and that was what came in the SS4300 (at the time of release the SS4300 was actually considered stock until it was so rediculously obvious that it wasn't even close, but came with a bonded rotor). If you could develop a dyno to accurately measure Brushless motors, chances are you will be very wealthy. As time progressed, the benefits of a sintered rotor outweighed the cons (manufacturing, costs, etc.) and it was necessary to streamline the labeling at Novak so with a new rotor, ribbed can and locked timing, the 4300 became the SS10.5. It is possible to upgrade your SS4300 to the 10.5. A Brushless motor is much more efficient and has way more torque, so when geared properly, it will be much faster than the so-called equivalents. What happens is when you start to get in to the mod motors, the technology is starting to surpass the ability of the drivers to lay that power down. A 3.5t Brushless is incredibly fast, so to put down that power, you have to have feel and often that is what people complain about with brushless. Often in the slower classes like 19t or stock, the tradeoff was worth it, since you gained so much speed it was a good tradeoff, but with mod it is different. The ESC controls the motor and how it feels to a great degree, and this is where the most advancements have been made. Size and properties of the rotor in a brushless can contribute, but it is the ESC that delivers the "feel." Software is a main key, and sensored or sensorless contribute as well. That's why many top drivers that have decided to go with brushless usually go with sensored (it has other cons, but I won't go into them here). Unfortunately, there is still no standardization for manufacturing or measuring the brushless systems, so even a 10.5 motor from manufacturer to manufacturer will vary greatly. A 10.5 BL from feagio (Orion, Checkpoint, GM, Much More, Speed Passion, Trinity, etc.) will be much different than from Novak or LRP. IN 1/12th, running out of battery time is still a huge issue, so the efficiency of the brushless comes in to play, letting the extra run time be turned in to a more powerful motor to compensate. In sedan, the fast BL motors are so strong, they have huge side affect son the electronics and since a car equipped with 5-cells instead of 6 is still plenty fast, many are opting to go to that route to make it easier on electronics, make the car lighter, and smooth out the power by reducing the voltage.

xjman

Thanks edseb, thats kind of the information I was looking for.

So something closer to a "stock" brushless setup will be my best bet for beginning racing? I plan to run a local asphalt track, if they allow electric, not sure on that yet.

I like the feel of the Castle setup I have now. I may consider one of those systems for this car as well. Although I have noticed that the brushless Mamba systems are not listed on the ROAR approved list that I have noticed.

Being new to the Touring car aspect. Is there anything else I should expect that I currently may not be ready for, or aware of. I've messed with crawlers, and various monster trucks and off road trucks. I can't imagine too much that I may not have a handle on.

edseb

In regards to which rubber tires of choice, there is no correct answer. Like full size tires there is different ones for different applications. Heat, wear, efficiency, etc. all add up to give different characteristics. Track temp is a huge influence and many manufacturers rate their tires in heat ratings with mixed results. The best thing to do is run what is working for the fast guys. X-patterns are a good standard tire, but as your laps become more consistent, you will start to notice slight differences in minute details. How the tire is treated (tire warmers, saucing techniques, etc.), what wheel is used, what insert, size of breath hole, etc. can have an affect. Also, some tires wear fast and are only at their best used once, but tires that last longer and wear better tend to have less favorable results than one-run tires their first run (again this is a generalization). Common tires for racing are RP (30s, 22s, 36s, 40s), Much More (32, etc.), Sorex (22, 32, 36), Yokomo (not as common any more), and now Jaco (Green, etc.).

edseb

Best to check at the track you plan on running at, since local tracks will have varying rules to suit their racer's needs. Often they use ROAR as a guide, but often stray from being strict in order to increase participation and other influencing factors. Castle Creations is the manufacturer of Mamba and have been a round for a while. Most clubs that allow stock brushless to be run with brushed stock, usually use the Novak system as a standard since they have been the ones to have the most established system. Your Mamba might be fine, but it is not considered stock, so you may run in to problems. The Mamba is unsensored so it won't be very common in racing, although I have seen it. Check with the track, most are often more than happy to help you and accommodate. For stock the Novak 13.5 seems to be the most accepted, but I don't think you can use your sensorless Mamba with that motor. If your are able to run it with the Mamba ESC, it may feel kind of "weird."

xjman

So I'm assuming that a sensored BL motor will cog less? More power sooner?

I have noticed that if I hammer the throttle when there is gobs of traction it tends to cog for just a split second before its on the power. I've heard that sensored don't have that problem, and is why a lot of us use them for crawlers.

edseb

Actually the cog is created by the magnetic field of the rotor in relation to the can. A sintered rotor will "cog" more and have more resistence due to the typ of magnet. If I read between your lines, basically you are telling me there is a jump and it tends to feel more like an on/off switch? In that case, a lot of that is the software of the ESC and the sensor. Often sensorless systems have a hard time with the poles of the magnetic feel because there is no "sensor," to tell the ESC where the rotor is and how it is spinning. What you are feeling is common and why top level drivers prefer sensored systems. In rockcrawling, you don't need speed, but it is torque you are looking for, so brushless systems work great for that application and for their ease of maintenance. Often brushed lathe motors are used too for crawlers.

edseb

Got to go now, good luck.
Carl Hyndman
Xtreme RC Magazine

Bruce Grembowski

iTrader: (6)

Not from what I undertstand talking to people at my track; I just started racing about a month ago, so this is just what I've heard talking to people. It was a little confusing to me, too, so I decided to go with brushed. With so many people going brushless, I've been able to pick up brushed motors cheap

I only watch the 1/10 sedan, so I have no idea. You might try posting your questions on the Electric On-Road forum, as this one doesn't seem to get much traffic.

TTFN,
Grem