2wd but 4 wheel braking?

[David Church]

I'm no expert, I asked the boss and that was his answer, but he was referring to his memory, perhaps the rule book would correct things, oh and I will find the biggest hat ever, in case he was right LOL

[jimmy]

I think it's a case of complying with the 'wording' possibly - but not the 'spirit' or intention of the rules. It simply ain't legal imho.

The sheer number of things you could get away with if micro servos were allowed all over the car would be insane. Servos have pots, the pots control movement in the suspension - you lock up a wheel and it could bind the suspension to some degree. So is 'that' active suspension? If it doesn't - then I'm sure you could design the car so it DID bind up - is that legal?

What about using just the pot to mechanically sense forces (with weights etc like some jules verrne type madness) and adjust things on the car.

Do ESC manufacturers start building in servo ports for 4-wheel braking? or servos on the car to prevent squat or dive?

If active suspension is suspension that moves and compensates for hard cornering - then I've already seen it done - purely mechanically.

Right, I'm gonna go put a servo on the back of my 410 and get some 4-wheel steering on the go - PROGRESS stylee

[David Church]

This may open up the next generation of RC cars!!!
Or we are possibly just talking complete rubbish haha

Great ideas though, perhaps it's time the boundaries are pushed?

[jimmy]

Originally Posted by SlowOne

There is nothing to stop anyone doing this. Two receiver connections allowed - use the Y lead. Driven wheels - I think not! Where is the engine/motor driving the front wheels? Driven, by definition, means that there is an energy input to the wheels that creates a force to which there is an equal and opposite reaction. There is no energy input to the front wheels, they are being used as a means to allow conversion of the kinetic energy in the car to heat energy.

As Terry points out above, 23.13 might sink you if in the Committee's opinion...

Hope your hat is tasty, Jimmy!!

A Y-lead?
There is force going into the wheels by a servo is what you're saying but you're also saying there's no force going to the wheels. YES there is an energy input going to the front wheels - it's called friction and it would be coming from the servos which are putting in energy to the front wheels.

I won't be eating any hats I don't think By use of sheer mechanical clever design you could in theory trigger servos to do other things that are within the wording but not spirit - and would not be legal.

End of for me - I think if it gets to the point you've got servos doing odd jobs all over the car I'll take up a new hobby. The idea is to race fairly - there are so many things that, say, a designer like the Awesomatix guy could do that we couldn't even dream up - using servos and other electrics to bypass the rules as they are written.

If you think binding up the front supension and putting forces into the front wheels is legal that's cool, I'm not gonna argue. My opinion is my own and this sounds like a hornets nest that could destroy 10th off road and the level of skill required to race it.

[David Church]

As I said Jimmy, I am no rules expert, haha you know this
But maybe your reading too much into it, it's not a driven wheel. It's free wheeling, it just has a disc brake connected somewhere. As far as the servo's go, my guess is it would be legal, and it is a guess, I would have thought that when I asked I would have been told any reasons why it's not legal.
Very interesting topic though.

[jimmy]

Originally Posted by David Church

As I said Jimmy, I am no rules expert, haha you know this
But maybe your reading too much into it, it's not a driven wheel. It's free wheeling, it just has a disc brake connected somewhere. As far as the servo's go, my guess is it would be legal, and it is a guess, I would have thought that when I asked I would have been told any reasons why it's not legal.
Very interesting topic though.

Agreed Dave it is very interesting but as I pointed out above - I think - it aint freewheeling if it's braking. Let's see how this discussion and putting theory to the test goes - as I say, I think it could ruin racing. Servo actuated front brakes - so all 4 wheels are under control on a 2WD car? Just doesn't sound quite right to me.

Besides which - front brakes are crap on any car. What's wrong with steering on the brakes/throttle anyway?

[mark christopher]

Originally Posted by terry.sc

There is nothing in the rules that limits how many servos you have in the car.

The pertinent rule is:
23.12 The use of sensors fitted to wheels, lay-shafts or suspension units to aid traction control or active suspension is prohibited. The use of the third channel parameter on a receiver is limited to external power supply only (no signal circuitry allowed).

As long as they are driven only from the two steering and throttle outputs on the receiver and no external sensors are used there is nothing limiting how many servos you can use.

If someone want to use a servo for front wheel braking there's nothing stopping you doing that but the only control of it must be from the throttle output shared with the ESC, so you can't have it so it can vary brake balance between front and rear when running.
If for example you wanted to use servos to stiffen the springs/dampers during hard cornering you can technically do that, but it will be doing the same whether you are going really slow or flat out, there's no way of the buggy sensing how hard it is cornering.

Of course the BRCA has put in rule 23.13 so if the committee thinks you are adding driver aids they can ban it whether it's legal or not.

Originally Posted by AntH

Is this not the same difference? Both methods (via driveline or front brake discs) apply a braking torque to the front wheels.

but the link in this thread to the guy with brakes clearly claims he uses servos and mixing ability, that example is illegal

yup he could use a y lead in the throttle port on the rx as i put earlier, to me against the spirit!

[Origineelreclamebord]

*Brake like a man (handbrake turns) or don't brake at all! *

Nah, to be fair... interesting points are raised here and it's an interesting front to discuss.

So terry.sc, I understand you could stiffen suspension and you say it's the same regardless of throttle input from the driver... but if there a rule prohibiting what you could see as communication between throttle and steering channels? In other words, is it prohibited to make the spring compressing servo respond to both the steering signal and throttle/brake signal (which is an indication of speed) or to the signals going through the actual sensor cable?

To be honest though, I wouldn't want to go that far... I like the fact that innovations have to be mechanical: it's much more feasable to DIY mechanical mods than electrical ones for most racers - also, it prevents the dependency of drivers to stay competitive by having the very newest electronic gear And I think if you find such a tight/tiny gap in the rules they will patch it quite quickly by banning your idea.

So in that aspect, mechanical brakes are really quite awesome! I'd say first step is to actually build and test the mechanism to test how much time it can actually win as a proof of concept as the link/project posted earlier in the thread

[dodgydiy]

i would say mechanical brakes are fine on something like a 5th or 8th scale car, but a 1/10 buggy is such a light nimble thing in comparison that it probably would have little benefit, think how light the rear end of the car would be under braking and how the weight transfer would affect turn in. you would have to be off the brakes earlier to let the car settle before turning in. you are also increasing unsprung weight on the front suspension affecting the handling too. Origineelreclamebord can tell you the effect of front wheel braking from his excellent fwd buggy, i know thats really light on the back anyway, but similar effect.

[terry.sc]

Originally Posted by Origineelreclamebord

So terry.sc, I understand you could stiffen suspension and you say it's the same regardless of throttle input from the driver... but if there a rule prohibiting what you could see as communication between throttle and steering channels? In other words, is it prohibited to make the spring compressing servo respond to both the steering signal and throttle/brake signal (which is an indication of speed) or to the signals going through the actual sensor cable?

The way the rules are written, if you have a setup so that when you steered left a servo stiffened the right hand side springs, whether you are crawling around a tight hairpin or going flat out round a banked sweeper, then at the moment there's nothing to stop you doing that at all. Although it is fairly pointless as you can get similar actual handling just with springs and roll bars.

Adding in the receiver throttle signal as well would also lead to some interesting handling characteristics as the throttle signal is not dependent on actual speed at all. Lets say it is set up so that it only stiffens the suspension when steering and when on power. This is great for a sweeper, at speed it stiffens the springs and keeps the buggy flat at high speed. But you then have a slow, tight hairpin so you brake and turn in, the suspension remains soft and the chassis rolls, until you open the throttle halfway through the corner and the outside suddenly stiffens. Unless you are going to feed in the throttle very slowly it's going to lead to some interesting handling out of slow corners.

Of course tapping into the motor sensor lead so you can measure the actual motor speed using the motor sensors is already banned in the current rules.

Then there's the problem of adding all this extra complexity and extra weight into a buggy, with none of the extra weight likely to be able to be placed in the best places for weight balance. Realistically it's not going to make much difference on track but would be an interesting engineering exercise. If someone does fancy a go I would say the best way would be 4wd axles and a diff or spool in the middle with the brake disc attached so less unsprung weight and no trying to balance left and right side braking. Good luck on trying to match it to the progressive braking on the rear though.

Years ago I did know a fellow racer who tried experimenting with a third servo controlling the rear wing which he mounted on a pivot so when he braked it raised to stabilise the rear end, but then flattened when accelerating to reduce drag on the straights. It meant he had less steering going into a corner and less rear grip coming out of the corners. He tried swapping it round so wing up on the straights but flattened when braking which gave him much more steering into the corners, but when jumping if he braked to lower the nose it also flattened the wing and ended up landing upside down.

[SlowOne]

Just for the avoidance of doubt about driven wheels...

In F1 the car is only allowed four wheels, the front two of which may steer and the rear two of which may be driven. Since the front wheels have brakes they are clearly not driven otherwise they would not be allowed.

You can only drive things by giving an energy input from an 'engine' - simple physics and mechanical engineering definitions. There is nothing in the BRCA Rules to prevent front wheel brakes being fitted and used providing a Y lead is used for the brake servo off the throttle connection. There is, however, Rules around the number of servos you can fit to to a receiver and that you cannot provide any feedback from the suspension to the servos you might want to actuate the those servos to stiffen springs, etc. Sleep easy in your bed, Jimmy!

As Terry says above, the potential performance advantage would likely be lost in all that weight and technical complexity. If it was that good, we'd all be doing it by now, or the Rules would have been amended to stop it! Love this debate...

[jimmy]

Lol, you seem to have a chip on your shoulder slowone

[SlowOne]

No, nothing like that. Just trying to make the point that 'driven' has a specific definition and that using brakes on the front wheels does not come under that definition - simples! Love the debate, simple as...

[David Church]

Have thought a bit more about the 2WD braking idea.
Whilst the pictures were not clear to see all the fine details, I am thinking that two separate servo's operating two separate cables would be very difficult to get equal braking on both wheels. I guess it would involve a lot of time to get the adjustments of the cables exactly matched.
The more sensible way would be to use one servo and one cable. Each end of the cable attached to each calliper, then the servo operating from the centre of the cable. This would give an equal pull to both callipers.

Now as far as being in the spirit of the rules I believe it is, as these cars are supposed to represent a full size car and I don't know of any full size cars without front brakes!


The current rules do not make this idea illegal, providing it is not operated by a third channel, but (as some have already recognised) we have an 'open' rule that allows the Section to disqualify any development that is considered not to be within 'the spirit' of the rules.

23.13 The 1/10th Off Road Committee are empowered to legislate at any time against any new equipment that in the opinion of the committee detracts from the essential skill of the driver controlling the car during racing. Manufacturers, importers and others are therefore strongly advised to consult with the 1/10th Off Road Committee before investing in technology that may be ineligible.