bertrandsv87

iTrader: (2)

I meant re-releasing the Factory Team tc4..... with upgrades of course(lcd drives, short shocks, gear diffs,etc...)....

niznai

I think Tamiya's Evo6 is exactly that: a test of a new paradigm. They'll keep working on it, ironing out little problems here and there and when they'll feel ready they'll launch an attack on Awesomatix territory.

Shaft drive cars can be balanced just as well as belt drive (and to answer the original poster, it is not only the mass of the armature that contributes to the torque steer, it is the whole momentum that gives torque steer, and spinning the rotor up to ungodly speeds does not help, let aside the more powerful magnets that give our low wind motors their torque, that's why shaft cars can't have the motor lengthways even with brushless. And brushless rotors aren't lighter than brushed anyway). You don't have to have everything down the centreline, it would be quite counterproductive.

Ideally however, a shaft car would have the shaft further out one way to allow the motor to come in more, and perhaps lower than they are now too. This would probably mean hypoid gears for the drive/crownwheel like they have in some buggies now. Which would push prices up a little bit. Well, the Awesomatix has demonstrated not everybody is willing to pay that. So until then, we won't have a new SD car.

Moving the shaft to one side enough to have the motor come in will create problems with the battery sticking out too far the other side, so you see, 'tis not that easy.

Bingo883

iTrader: (1)

What about the JL10e? I heard a lot of good things about it but never seen one in person.
It's simple, it's light weight...

theproffesor

iTrader: (66)

Really??? Brushless rotors are way lighter than a brushed rotor. And their mass is alot more centralized. Combine these and you get a motor that has alot less torque effect. The weight is so centralized in a brushless rotor, that to my knowledge, brushless rotors are not balanced. Yet I never had a brushed rotor that didnt have expoxy and drill marks to balance it. Otherwise it would vibrate so violently it would destory the motor.

I also stated that a shaft drive would be ideal for spec classes. Classes where the RPM's arent getting up to insane speeds. Mod is different. A belt drive may still be better due to the higher torque affect of those motors.

TB03Racer09

iTrader: (1)

Used to be a very big fan of shaft drives. Lately, I have to come to the conclusion that the dual belt setup is simply the best for 1/10 touring car, efficient, simple, lightweight and balanced. I do have a Tamiya TB04 which I like a lot though.

niznai

As a business plan it wouldn't work for even the bigger players to have two platforms on the market at the same time for the same market share. They'd just split their customer base for the same revenue whilst having two platforms to design, support, etc. Where's the motivation? How many top end racers do they sell now? Tamiya probably makes a couple of hundred TRF kits. How much profit do you think that rakes in? Let's say 100% profit (cost to produce zero, just for the heck of it). Let's say they charge every retailer 100$/kit (again absurdly unlikely). That means what? For a sale price of 600$ (again, absurdly unrealistic) 100000$ profit? That's probably the phone bill for a month for Tamiya. Well, it's the same for everybody else.

As for the weight effect, as I said before, it's momentum that kills you, not the mass on its own. The weight difference between brushed and brushless rotors is not bigger than the momentum created by the massive torque of the brushless motors. Try this out if you want. Grab a motor by the shaft and see how much it deflects when power is applied and repeat for both brushed/brushless making sure you compare apples with apples. Use a motor hooked up to the ESC and apply trim until it just moves and holds the deflection. Measure the deflection and let us know.

Skiddins

A lot of brushless rotors I've seen do have a balance ring that is drilled in places. It's usually the coloured ring at one end

theproffesor

iTrader: (66)

While i cant take actuall measurements since I dont work in a science lab, I can tell you that a brushed will deflect alot more. I remember holding 27turn brushed in my hands with power applied, and even those low power motors, if you werent holding on, it would fly right out. Ive done the same with a 13.5 and felt no where near the amount of twist.

Yes, rpms make a difference in what we are talking about, but brushkess motors are spinning comparable rpms to there brushed counterparts. But lets say they weigh the same. If both weigh 100g but the brushed rotor has a radius of 30mm and the brushless has one of 15mm, it will take twice the energy to
start and stop the brushd rotor. This has a direct effect on torque steer.

Ill give another exaple. Stupid big rims on real cars. Overall diameter of new wheel/rim combo is diamieter as stock, but all the weight is now on outer edge of curcumfrence of wheel. Weight is also the same du to less rubber but more aluminum. Cars with these types of wheels go through brake pads like oil changes. Ask any auto mechanic. Why??? Physics. It takes more energy to stop weight that is farthur from a center point of rotation than it takes to stoo the same weight if it were closer.

Thats why we try to keep the weight of our cars as close to the center as possible. If weight was weight, then it wouldnt matter where we placed it on the car. But since the chassis is an axis, it does matter and we try to tuck it in as close as possible.

As far as business model, Im sure tamiya sells more than a couple hundred TRF kits. And if companies would actually make a car that works well without umpteen changes year to year, then production cost decrease over time as more units are produced. If your not making new molds and parts every 12 months, things tend to get less expensive.

niznai

You don't need a lab. Just a couple of motors, and some electronics which I suspect you have already since you're here.

Torque is your enemy and brushless motors have it more than brushed, that is their main advantage. That is what twists the chassis of our cars hence you need to put it across.

The mass distribution is important, yes, but I don't think it is in our case the main reason for our problems, simply because the differences are too small and completely overprinted by the force that spins the rotor (which is what gives the torque).

Your example with the car brakes has no relevance and you got your physics wrong too. Car brakes work by converting mechanical energy to heat. The main source of energy in that case is the car's forward momentum, not the wheel's spinning momentum. If you don't believe this, jack your car's wheels off the ground, spin them at whatever speed you like and apply the brakes. I bet you all your toys against mine, the wheels you detest will stop dead as quickly as the OEM wheels for any car (or within an absolute minimum variation - fractions of second). The mass of the car times its speed squared is what you're trying to convert to heat, that's the enemy. The wheels here have nearly no effect at all, be they train, car, scooter or bicycle wheels, small as your RC car wheels or big as those on the steam engines of yore as long as the wheel mass is the same.

As for the business model, I am sure Tamiya would sell more TRF kits. If they made them that is. But let's say they'd sell 1000. That is just one order of magnitude (not even that, in fact only 5 times) so let's say they could make in my absurd assumptions above 250.000$ profit per year. I am pretty sure Mr Tamiya wouldn't even leave his bed in the morning for that kind of money.

theproffesor

iTrader: (66)

Well this thread has gone a direction I never intended. Ive been doing this for over 20 years now and have seen and felt the difference in brushless and brushed motors and watched the evolution from in cars and electronics since the the gold tub RC10 and before the touring car was even thought of.

Ninzia, I dont think we will ever come to an agreement on this so lets move on.

Why with offroad has everyone but losi gone to a shaft drive? Durability, simplicty, weight balance with saddle packs. Even the Losi with its 3 belt design is done in order to centralize the motor. (Yes I realize its a copy of the XX4. I had one of those too). If it works in offroad, with very low turn,high torque motors, why not give it a shot onroad?

niznai

Because in off road you never have the grip that would turn your handling to shit as you do in on road.

That's why.

And by the way, I've got 23 years of RC if that matters, so mine's bigger than yours.

bertrandsv87

iTrader: (2)

Come on guys... Mine is bigger than all of yours !!! LoL !!!!
I have yet to experience that elusive torque steer in all my tc4's , brushed and brushless, but my brushed mod car is way smoother than my brushless mod car, accelerating and decelerating.... In short carpet tracks I prefer to use brushed mod motors(6turn to 9turn)......just sayin....

theproffesor

iTrader: (66)

Here we go again. Have you seen some of the offroad tracks recently? They probably have more grip than some outdoor asphalt tracks. I mean they are saucing their tires just like we do. And they run on carpet and astro tracks in Europe. Those have ridiculous amount of grip. As do the grass tracks they race on.

But to other point, even if there is less grip, wouldnt torque steer be more of an issue? As tires are slipping around it would be even more important that they all have equal grip to be able to accelerate out of corners in a straight line?

Exactly Burt. Torque steer is a non issue. I never noticed itnon my PRO4 in USVTA, USGT, or 17.5 racing. What I did notice, is that I always had an extreamly hard and smooth accelerating car off the line and out of corners.

niznai

Your tires in off road slip so much it doesn't matter if one wheel has 10% more grip than the one on the other side, that was my point.

Try this.

Use a wheel of a slightly larger diameter on your buggy on the left front (say, arbitrarily) and try to drive the car around. Now try the same trick with an on-road car.

Or just get one of those cars (not sure if you guys have them in the US, but they do in the UK), they call them "stock" or something. They race them on oval tracks and each wheel (yes, all four) has a different diameter. Try to race that one off road, and then try on road (on a normal track).

Where did it go best?

daleburr

I think off-road primarily prefer shaft as its easier to keep everything nicely sealed, and it probably copes better with bumps and jumps (no belt slip).

But you're right that brushless motors cause much less torque-steer than the old brushed motors, since the rotors have much less inertia due to the smaller diameter. I've personally compared a SD car with a 27t brushed motor vs a 17.5t brushless motor (so similar power). The 27t car could rock itself off the palm of your hand. The 17.5t car barely moves. (tested with wheels off, otherwise they'd both end up on the floor!).

SD was dead at the end of the brushed days for this reason. The A700 has shown its no longer an issue with brushless motors, even powerful ones. Although it hasn't shown to me that there's much advantage to shaft either. It competes okay with the belt-drive cars, but doesn't blow them away.