Open stock, a radical approach to speed limiting.
 

First of all, before all the haters of rpm limiters jump on me, please actually read the entire proposal. This is a bit different idea so please consider it on its own merits. The purpose of this article is just to discuss the feasibility of the idea, not whether it should actually be done or not. I myself have been a hater of rpm limits in the past but this idea intrigues me. So throw out all your past views on the subject and really think about what I am proposing.

So what are the rules? That is the simplest of all, there is only ONE! You heard me, just one rule other than the usual weight and dimensional rules for the car. That rule is a maximum allowed rpm at the tire. You can run any motor, battery, speedo, timing, gearing you want as long as your rpm is limited to the maximum rpm allowed AT THE TIRE. Want to run a 3.5 on 6s, go for it. Top speed will be no different.

What will be needed to do this? Just two things:

1. A speedo with a user adjustable rpm limit (with a laptop, programer or other such method but not on the track. Similar to setting blinky mode). It will also need a clear indicator of full throttle such as a particular light coming on or blinking (most speedos have this already). See #2 for the reason why.

2. An accurate tachometer for teching wheel rpm at full throttle. To check for compliance, all you have to do is have the racer pull the trigger to full throttle, check the light on the speedo to verify that it is at full throttle (so he can't back off his endpoint for tech and then raise it on the stand) and check the rpm of the tire. If it is over the max, he has to go back and adjust his speedo down until it passes.

That's it other than the usual gear for teching the car itself for weight, width, height, etc. You don't even need a voltmeter (this part is optional. just throwing it out there) since they can run whatever battery they want, charged in whatever safe manner they like.

Now let's look at how this will work. Let's say the track has determined that 5k tire rpm (not a real number, just for illustration) gives an appropriate 17.5 stock level of speed. You could run a 17.5 with a 4.0fdr and an rpm limit of 20k which should give you the max allowable 5k wheel rpm. But this is not the only combo you can run, like the title says, this is OPEN stock. Want to get to max rpm quicker to accelerate faster, drop a hotter motor and appropriate fdr into the car. You could run a 13.5 or 10.5 with a 5.0fdr and a 25k rpm limit or 6.0fdr and 30k rpm limit and still have the same 5k wheel rpm max, thus the EXACT SAME top speed. The only difference is how quickly you get there. Want to run a 3.5, fine. A 550 SC motor? Go for it. Run anything at all you like as long as you use an FDR and rpm limiter setting that doesn't exceed the 5k wheel rpm limit.

Now there is at least one potential problem to look at. Drivers seeking any competitive advantage they can find will probably end up running pretty hot set-ups. This will not help their top speed but will increase acceleration. The end result could be cars that drive like a light switch as they accelerate to the max rpm almost instantly. That might not be fun to drive but might not be a bad thing either. It may help train drivers to handle the tire spinning power of mod without the car destroying, intimidating speeds.

Let's look at some potential benefits.

1. No more motor of the month.

Since you can run any wind, timing, boost, gearing you want, spec motor performance and variance no longer matters. If your brand y 10.5 isn't accelerating as fast as the brand x 10.5, put a brand y 9.5 in it. Or throw some more boost at it or play around with different gearing/limiter options. Or you may find that your weaker motor is better as it is more driveable.

2. Battery performance is far less important.

As long as the battery has the capacity to last the full race without a major fall off, battery doesn't really matter. If your laptimes are falling off too much late in the race, you could go to a hotter set-up. If you are running a hot set-up at the limit of available grip, your times should actually improve late as wheel spin is reduced and the car gets easier to drive.

3. It can be tailored for different tracks.

A big outdoor track that wants higher speeds can simply raise the wheel rpm limit. A small indoor track can lower it. No need for different motor rules/classes. Most traveling racers will probably have a variety of different motor combos for different grip levels so they should have little difficulty adjusting to a different limit.

4. The selling points for motors will be different.

Instead of buying the motors that provide the best laptimes, motor's top selling points will be things like driveability, durability, price and support. You know, all the things we wish we could get from the best performing motors.

5. Simple tech.

No need to count teeth to determine FDRs. No motor tech or approval processes of any kind. No battery voltage checks needed (unless you just want to for safety). Just the usual weight and dimension checks plus a quick wheel rpm check before the race.

6. There is still room for the tinkerers.

While top speed should be identical for everyone, there is still room for the hard core tinkerers and testers to try and find better ways of getting to that top speed. The difference is that the gains will be smaller. A good driver with a well set-up car but a less than ideal power combo should still be very close to a similar racer with an optimum combination, not two laps off the pace.

So what do you all think? Could this work? See any potential problems I am missing?

Whats the point? To make it easier for newer drivers? Or to compress the field for closer racing?

The way I look at it is there is nothing "stock" here, you just put a RPM limit on the MOD class.

I don't know the tracks you run, but at track my car only spends about 20% at top speed. The rest of the time its the corner speed and acceleration on the infield that makes the car have better lap times.

This just changes the focus from RPM and HP, to Torque and Amp draw.


Shawn.

its definately food for thought

The point is to have good, close, fair racing at slower than mod speeds without all the complaints of cheating, motor/battery of the month, complex and time consuming tech, one brand only specs, etc.

As for it not being "stock". What's stock about current "stock"? Nothing I can see.

RCTech user Meradin has done this using an optical tach, but for the VTA class. It's working quite well for his racing group. But I wouldn't use it as the only tech item, because (as you said) the acceleration will vary quite a bit depending on the motor, battery, and car weight.

Here's a way to equalize the racing without ANYTHING to tech, if that's what you're after:

http://www.rctech.net/forum/electric...pec-class.html

Still not difficult for the ESC firmware writers to work around it. When the car is tested in scrutineering the motor is under almost zero load. On track, even at the end of the straight, there's quite a lot of load on the motor from aero/tyre drag.

It would be easy to write firmware to disable the RPM limit if the current drawn is over say 10A. Passes tech, yet has no RPM limit out on track.

Whatever the rules are for a 'stock' class, there are ways around them. The best solution is ESC boost as the limit then is how much heat the motor can take, and most of them can take about the same. In any boosted class you will see a huge range of ESCs, motors, lipos etc, showing there is no 'flavour of the month' or 'must have'.

And for the newbies (or those who just can't be bothered with boost), you also have a slower blinky class. So whatever you prefer, there's a class for you.

This is what we have in the UK at the moment; 17.5 blinky, and 13.5 open. Both classes are thriving, and long may it continue.

I hate these threads.

Sure, I'll run to an RPM limit. I'll just motor up and beat you between the corners while running the same speed at the end of the straight.

RPM isn't what makes a car fast, POWER is. Stock will always be about who can get the most out of the limits. It's a great class at club level but at national level it becomes rather ridiculous.

I actually agree with you. The only problem is that there are a VAST number of racers that don't. Boosted is dead in the US, replaced by fifteen different motor spec classes.

What you are trying to do could be done a lot easier by just setting minimum lap time on the computer to a certain time say 14.9. So any lap faster then that wont count. People could detune there motor/car to a 15.0 for a perfect lap and it would reward the most consistent with out going over.

Joe DiGirolamo

And if you read my post, that is exactly what I am proposing to do. Want to run a 3.5, go for it.

That would be breakout racing as someone mentioned earlier. Breakout racing can be lots of fun but to me (and many others) that isn't racing. What I propose would not limit racers from trying to go quicker, just limits their top speed to manageable levels in a different way from the usual motor limits.

You really need to do a actual testing...using a 4.5T vs a 17.5T with the same ESC and RPM setup that equal to each other.......but my thought is, the car with 4.5T will have the MONSTER PUNCH over the 17.5 even though they have the same or even lower then the limited RPM.

RPM is not the only answer...ohm resistance, amp draws....all these number will effect the motor performance. TITC at Thailand started this in 2012 for their blinky GT class...and they are still trying to add more LIMIT to get it equal because they have found more and more ppl can cheat the system and be faster on the track even they have the RPM, ohm resist and amp draws limit on their rule....still not fixing it.

Yes it will. Which was kind of the point.

So basically your idea is completely pointless. It's either a class for beginners that is uncontrollable, or a class for experienced racers that is futile.

Maybe, maybe not. Look, I don't like all these limit or spec or breakout or whatever ideas either, I say just run mod or boosted and be done with it. Unfortunately many racers don't see it this way so they keep throwing crazy ideas out there that either wont work or aren't practical. I think this idea addresses many of those concerns but I could be wrong. If you have some actual constructive criticism to offer instead of just dismissing it out of hand, please feel free to do so. None of this is currently possible anyway since as far as I know, no esc exists that can do all of this so it's not like I'm trying to force it down your throat.

Sure, my constructive criticism is that we have a class structure available to us already that works. TC has a variety of motors available to it from "easy for your granny" to "world class only". The onus is on racers and organisers to support the class that best suits them. The cars are built for 2s so why change, and motor classes need basically no scrutineering whereas rpm classes need constant scrutineering.

You will always have people that will spend silly money on having the fastest "slow" car, it doesn't mean that stock classes are a failure - if it bothers you just race in a class that has more power than traction, that is where driving skill matters rather than the depth of your pockets.

As mentioned in the PM it is not only the topspeed but the needed time to reach the (limited) speed determing the laptime because we are accelerating from corner to corner. With this the lower turns motors have the advance still giviing a lot of stress on the drivetrain and tires.

There is a German company who devellopped a capacity meter and can be programmed to a certain capacity. Every driver has to be sure he is driving within the determed capacity. If he is going beyond it a red light will be shown. In that case you are working on the energy so basicly pushing with slow motors and save driving with fast motors using the same amount of energy equals the performance.

Thank you. That's pretty much exactly what I would say if I wasn't trying to come up with something to please those that disagree with us :D

I still think this is worth at least consideration though.

So without discussing the merits of the class idea, what I'm intrigued by is how to accomplish RPM limits.

Measuring no-load peak RPM at the rim is dumb, IMO. It takes time in tech, and the car will always see much higher RPM on a stand in tech than it does on the track. It seems more interesting to me to have a physical device that can be controlled.

The most obvious would be something in-line with the sensor. What could you accomplish with that? Some things that would seem possible:
1) Monitor not just absolute RPM, but also delta RPM, so you limit both top speed as well as acceleration.
2) Completely cut the sensor signal to cut power, if the ESC cooperates.
3) Retard the signal to the speedo to effectively reduce motor timing and limit power when nearing limits?
4) Massively offset the signal to make the ESC actually apply brake? I'm not sure why you'd need this, though. And it'd probably be a really good way to burn down motors and ESCs.
5) Record telemetry for post-race inspection.

EDIT: Also, you could change the shape of the signal to maybe get the ESC to fire each phase for less time, as another way of reducing power without cutting it?

-Mike

+1 well said.

This is an interesting idea that the local track owner and I have already discussed.

For proper control, a microprocessor would need to monitor (but not modify) at least one of the sensor signals to read the motor speed, but have the capability to intercept the signal going from the receiver to the ESC. When the speed limit is reached, then the microprocessor would replace the normal signal from the receiver with a signal that gives neutral (zero) throttle. (I have an external LiPo cutoff module that works like this.)

The microprocessor could also monitor and control acceleration in this manner, as you already observed.

It's very much like real F1 cars used several years ago for traction control (monitor wheel speed, interrupt spark if necessary).

This post may have come off as being a bit rough around the edges, but I completely agree. In a nutshell, I'm afraid that is exactly what the result would be. Everybody would end up running high power mod motors that go from zero to top speed in 15 feet, and I just don't see that being entertaining, fun or competitive.

@Wingracer

What you propose requires a technical solution to implement it and one does not currently exist. You could achieve the same outcome by using a fixed FDR, but doing that makes teching a headache because the bean counters need to count teeth to ensure compliance.

So ultimately, what you are trying to achieve is a limit to wheel speed, this is currently done via blinky esc's and motor turn limits. But it could also be just as easily done by specifying a maximum wheel speed per class.

Teck then becomes a simple matter checking the motor is of the correct wind for the class and then putting a car onto a dyno and spinning it up to max rpm after ensuring the radio is set to 100% throttle. You could tech a car in 1 min, if they failed, all they have to do is change pinion or spur and come back and tech again.

For this, a technical solution already exists in the McPappy Dyno and Eagle Tree data logging software.

There are other benefits to doing this also, you could use a lower wind of motor and not have to push the thing to the point of magic smoke being released. Cooler running motors mean motors last longer and do not need to be replaced, fans become obsolete as you do not need to run the motor beyond its capabilities to remain compeditive.

Stop the whining guys, and practice.....just sayin... These types of ideas have no chance whatsoever, and the will to make everything equal is a fantasy, not reality.... If you want equality, then only race VRC PRO....

This is the answer. Old school hand out motors. Just like the big races used to have.

Can't time it. Timing is locked.

Can't rotor tune. The rotor is marked.

Just do the best with what you got.

If a group or orginization buys enough of them, you may be able to get them at a pretty good price.

http://www.trinityrc.net/shop/image/.../ml5-80x80.jpg

Handouts solve nothing, you have the same old issues of someone whinging someone else got a better one than he did or people handing them back in again and again until they find one that is better than the rest as happened at a resent meeting that used handouts.

Racing is inherently unfair, that's why we try like hell to make the unfair in our direction.

So how would this work with a pan car?

Car "A" is running 42mm diameter tires.
Car "B" is running 44mm diameter tires.

With the same max RPM and the same gear ratio, Car "B" will still be faster due to the difference in rollout. There's also a variance in the diameter of different touring car tires, but since spec tires are often the norm with touring, that issue isn't really a concern there.

.........me too......breakout racing is not racing.........lets penalize every racer who wins.....better yet give each racer his own class...then everyone can win their "A" main every time they go to the track......these ideas are ridiculous...

The reality is that there is no single solution in R/C racing that is going to be ideal for every track and every racer. Instead of trying to fix "stock" racing to be a one-size fits all class, the best solution is to promote the classes that are best for a specific track or a specific group of racers.

If stock feels slow at your track, the track director should help promote open mod. If stock is too fast for average racers at your track, the track director should promote slower classes (VTA or some of the slower TCS classes).

What we can take from this thread is some good ideas how to improve racing at our local tracks, but there is no need to change national/international classes.

Personally, I have no desire to race in a class like this, but if you really wanted to do it, I think it might be possible to do, using the sensor from a laser mouse to watch the surface fly by and have a device between the rx and ESC to control the max speed as well as maximum acceleration curve based on readings from that sensor.

Only if you find some way to stop drivers removing the tyres and stuffing bigger foams in there to increase the diameter to get more top speed for a given rpm.

Having a maximum wheel rpm limit is different. Unless your track is made of nothing but long straights and fast corners, or the rpm limit is set so low that you are driving around most of the track on the limit, you will spend very little time actually at the rpm limit and the rest of the time you would be looking at mod acceleration and performance.

You want to limit speed? Build a track layout with very short straights, say 30-40 feet, and let everyone loose with whatever they want. Higher turn motors become much more drivable when they can't run out of revs and low turn modifieds will get too hot.

Why limit top speed. It is not the straightline speed that makes our cars difficult to control. It is actually the acceleration that makes mod hard.

As an example, most drivers in our national 1/10 200mm nitro races have improved this year while we switched to a stock 'simple' .12 motor. Now comes the best part: due to the combo of motor and pipe the top speeds have gone up but the torque has been reduced. This has made the cars easier to control and thus has given cleaner and better racing.

So imo limiting top speed in mod (as someone else already poonted out this idea is) does not go well with novice racers. As everyone will always switch to the most badass combo available. Especially the beginners....

Limit the battery capacity. Tamiya has 2200mAh LiFe batteries that can be run down to zero capacity. :)

Classes like 17.5 Stock and 21.5 VTA etc already have limits on top speed, that limit is the point just before the magic smoke is released from the motor. All using RPM or Wheel Speed or FDR does, is move the class speed limitation from the motor to some other location where you might have more control over it.

In 17.5 Stock you have guys changing rotors every other round, others using motors for 1 or 2 runs and binning them, pro teams that are dynoing 100's of motors to find the best couple from a batch and other equally as crazy things all in the pursuit of 100ths of a second advantage over another guy.

So, if the goal and primary objective of stock racing is to provide a level playing field where all drivers are competing equally based on driver skill and setup ability, then removing the ability of the HAVES to gain advantage over the HAVE NOTS this way, goes a long way to achieving the prime objective of the class.

I don't like the idea . . . I don't think 'stock' racing is broke.

On VRC Pro if you race a spec class you will notice, motors are locked, gearing is locked, and heck half the setup is locked. There are still people who can flat out drive the crap out of those spec cars, and there is still a large range in ability. In fact to such an extent that I would be willing to bet most races are not decided on the motor / esc / battery of the month. The fast guys are going to be fast with a silver can motor and nicads.

If anything was to be done would be to create classes based on skill level not motors (ie just like nitro). There will always be sand baggers though so no system is perfect . . .

this solution will just make things more complicated, and tedious. Tech needs to be simple, and easy to enforce, and not ruin the actual racing. I don't see the OP proposition accomplishing any of that.

I agree with you, the 3 things that win races are driver skill, car setup skill and then probably tires. What all this really comes down to is PERCEPTION, the guys in the C and D mains want to have the perception that they are competing on an equal footing with the guys in the A main. What they do not want to admit to themselves is that, well, they suck and just do not have the skills to compete at such a high standard.

The greater perception of fairness the less likely you are of having bad aspects that currently exist in stock. Stock should be about driver and setup verses driver and setup, nothing more and nothing less, but currently there is an inherent bias in the system that favors certain groups of people over others, thus you have a perception that the racing results are not representative of driver skill and setup but are a representation of who can throw the most money at the problem.

what you're describing here is the fact that with more money (as a big team) you can get a competitive advantage, and that we haven't moved forward an inch since the good ole days of 27T closed cans stockers that were one-run-only. The solution to this is to simply prevent big dogs from running stock. This would de facto mean that stock turns back to a "novice" class - which is perfectly fine by me as this is the original concept of "stock", as opposed to what "stock" has become i.e. just another class.

We should all keep in mind that stock truly is for the slower, beginner drivers and that the system has drifted badly. There's a reason why stock is 10.5, 13.5, 17.5, 21.5, 23.5, 27.5, you name it, but never 3.5 or 4.5... And as the motors are "slow" and don't overpower the car, then people start looking for another advantage (speedo, batt, timing, ...)


Now - back to the topic - fixed RPM at the wheel, good idea but doesn't prevent playing around with inserts, but fixed topspeed is even better, I say rolling dyno with no resisting torque but with a 5lbs weight on the car (to prevent from smart esc's that phase faster under load than when free wheeling). Let the folks manage their low-rpm torque like they wish!

Better still: No more stock classes - kill stock, open for everyone.

Keep up the discussion, it's interesting :)

Paul

Could always go back to foams, that would kill the insert fakery. I prefer to race on foams than rubber anyways, $12 a set for a set of 4 foams and i get 3 club meets out of them + practice, $30-40 a set of 4 premount rubbers + traction compounds and tire warmers and they are lucky to last more than a meet before they drop off notably, and after 2 meets are useless.