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Old 07-23-2013, 09:48 AM   #1
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Default 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?
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Old 07-23-2013, 10:23 AM   #2
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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.


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Old 07-23-2013, 10:25 AM   #3
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its definately food for thought
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Old 07-23-2013, 10:32 AM   #4
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Originally Posted by Shawn68z View Post
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.
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.
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Old 07-23-2013, 10:36 AM   #5
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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
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Old 07-23-2013, 10:54 AM   #6
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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.
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Old 07-23-2013, 10:55 AM   #7
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I hate these threads.
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Old 07-23-2013, 10:58 AM   #8
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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.
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Old 07-23-2013, 10:58 AM   #9
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Quote:
Originally Posted by daleburr View Post
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 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.
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Old 07-23-2013, 11:00 AM   #10
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Quote:
Originally Posted by wingracer View Post
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.
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.

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Old 07-23-2013, 11:00 AM   #11
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Originally Posted by sosidge View Post
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.
And if you read my post, that is exactly what I am proposing to do. Want to run a 3.5, go for it.
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Old 07-23-2013, 11:02 AM   #12
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Quote:
Originally Posted by losi888 View Post
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
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.
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Old 07-23-2013, 11:20 AM   #13
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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.
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Old 07-23-2013, 11:22 AM   #14
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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.
Yes it will. Which was kind of the point.
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Old 07-23-2013, 11:50 AM   #15
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And if you read my post, that is exactly what I am proposing to do. Want to run a 3.5, go for it.
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.
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