I've been thinking about this some more & I believe the problem is not the servo speed as such, rather the problem is that the servo is moving too far too quickly. An easy way I can illustrate this is when taken to extremes, consider a hypothetical servo with instant/infinite/zero/0.0s transit. This servo can go from one end-point to the other (or anywhere else in it's range of motion) instantly, absolutely zero time (extremes remember).

If the servo horn were to move 1 billionth of a mm in 0.0s that would cause no one any problems because we wouldn't even know the servo horn had moved as the distance is so small as to be completely undetectable to the driver. Now consider the horn moves 2 or 3mm in 0.0s, on the way into a low-medium speed 180o corner, needing quite a bit of lock to get through the corner. When the steering wheel is moved & the servo responds instantly, going from wheels straight ahead to (e.g.) 60-70% of full lock, the car would dart right off the track way to the inside because of too much lock too soon.

Now just think of the servo having some sort of intelligence to over-ride the driver inputs & instead of going to 70% lock in 0.0s, the servo only goes to perhaps 5-10% or maybe even 1-2% in 0.0s, just barely peeling into the corner. But this is an instant servo, so less than 1 billionth of a second later it moves the horn perhaps another 1% or something, gradually increasing the amount of lock to be able to navigate the turn & stay on track.

So it would seem that the problem isn't that the servo is too fast at all, it is moving too far. The amount the horn moves the front wheels is not correctly responding to our inputs on the steering wheel. This is an absolutely 100% personal thing different from every single driver to every other driver. When we turn the steering wheel we don't have any need to think about it. No driver ever comes to a corner & thinks to himself 'I'm going to move the steering wheel 2hours to the right to get around this corner' because the decision of how much to turn the steering wheel to make the front wheels turn a certain amount that will allow the car to safely navigate the corner is a sub-conscious one. Think of 1/8th nitro buggies & how often & how quickly the driver must make steering wheel corrections & reactions to the front end sliding, rear end sliding, etc. I'm just guessing here, but maybe there would be a correction happening every 10ms or so. Even trying to drive down a bumpy straightaway requires constant steering wheel correction to keep the buggy going kinda straight.

WOW! I was beginning to think that was never gonna end. Damn instant response servos!:mad: :ha:

Regarding negative expo being the solution, better than slowing the servo's overall speed, negative expo is doing exactly what drivers like us absolutely need it to do if we have a too fast servo making our cars twitchy. Negative expo is actually changing that relationship between how far the steering wheel is moved & the resulting movement of the front wheels. We still move the steering wheel the same amount but with negative expo, the servo & therefore front wheels don't move as much as they usually would. And it is so perfect because as I explained in previous post, as more steering lock is dialled in we actually need the servo to start responding quicker, moving quicker than when in the near-neutral steering area.

Again, I do hope I haven't made things worse by confusing the situation for some. I never meant to imply that we shouldn't ask what other drivers do or how they determine what settings to use. Absolutely we should! Trial & error is a horribly crappy method of learning. We don't learn anything with trial & error, we happen to stumble into the solution. By asking & explaining, we are actively learning & understanding the thought process that goes into making the choices of which settings to use/change. I was just pointing out that we cannot use anyone else's settings blindly for this particular problem as it is such an extremely personal thing that trial & error is the only way to arrive at the solution, but only after knowing what the setting being changed should accomplish. I emphasise should because this is the trial & error now - does -10% expo get me to where I need to be? No. -25% expo gonna be enough, maybe -45%? Who knows, try it & see what happens is the only way.

Forgot to say for sure you can still use your 451R with digital servos, just set your M11x to NOR instead of SHR or SSR.

Also I've never actually driven an on-road RC car, only buggies. But to me a car is a car & it doesn't really matter about the surface when talking about basic car movements. I have driven full size on-road cars on race tracks though.:tire::tire::tire::p

Aaron 125 fantastic write-up !!!!!!!!!!!!!

Let me tell you guys how stupid I am....I have had this radio for about 1.5 years. I have been making Expo adjustments but never had the feature Activated on the radio. It was alwasys set to INH. :rolleyes::lol:

Hey guys

I have bought a new SDX801 servo and want to know if i can run it in the fast mode ??

Do i need the rx451R reciever also ??

Thanks Phil

:Sprikler:
That's pretty funny man (I can see how it could be easy to miss coz you change the expo setting & wouldn't think you have to hit "ok" after doing it, just change menu & it's active), but didn't you think something strange was goin on when you changed your expo settings but they made absolutely no difference?:p All the same, glad you got it working now or still no change?

:sidecarphil1:
I would say it depends on exactly what you mean by "fast mode"? I've got the original RX451 & I set my M11x to the SHR/SSR "fast mode" but I've no idea if it really is any faster than the NOR mode as I've only ever run them on SHR/SSR. Apparently it does speed them up but neither Sanwa/Airtronics nor anyone else I've ever heard from can actually quantify how much the servo is sped up or give an exact figure. Please correct me if I'm wrong, would love to know by what amount any servo's transit time is being decreased (decreased is faster).

aarron 125
Hi futher to the last posts i was thinking the response time
i would like to keep, but travel (distance of horn movement)
to decrease my question is apart from expo is there another
set up avaible.
Many thanks in advance

Hmmm... That is a mighty fine question indeed. If Airtronics/Sanwa would actually write an instruction manual that wasn't so arbitrary & difficult to decipher I would hope to be able to give you an answer. e.g. Just what the hell does Adjustable Rate Control actually do? No one has yet been able to explain this to me. Consider: "The Adjustable Rate Control varies the amount of servo action with respect to manipulation of the steering wheel or throttle trigger." Then in the next paragraph: "Adjustable Rate Control is similar in function to Exponential, however, Adjustable Rate Control allows you to move and pinpoint the neutral position anywhere between the Steering or Throttle stops, not just the center." from M11x instruction manual. Well I certainly cannot understand how it's possible in any way for the neutral position to be adjusted or moved or changed. To me, 'Neutral position' indicates the point in steering wheel movement (for me steering wheel is on the Tx, front wheels are on the car) where one can remove their hand from the control & the vehicle will procede to travel in a straight line, as long as the trims, setup, etc. of the vehicle will allow it to do so. So is Sanwa trying to tell me that ARC actually allows one to set the Neutral point to somewhere other than 0o???:confused: What the f***? How could Neutral be somewhere other than when the wheel is normally when one takes their hand away from the control? Just makes absolutely no sense to me whatsoever.

That's not the only one. "Use the TWEAK setting when you want to fine-tune the left and right steering balance. This allows you to move and pinpoint the neutral position of the Exponential function independantly anywhere between the Steering Endpoints, not just the center. This ensures that Exponential is balanced for both the left and right sides." Again, I just can't understand what the f*** their on about. First the bit about "anywhere between the Steering Endpoints, not just the center"; the neutral point on the graph on the LCD never changes, it is always at the bottom left or right corner of the graph, so how can it be said that the neutral point is being moved when it clearly isn't? I've just set my M11x steering Expo to -17% & the left Tweak to 14 so that the left graph is a straight line, essentially so that the Expo is only coming into effect when the steering wheel is moved to the right. This is confirmed by checking that the increment lines on the horizontal axis are almost completely matching up with the increment lines on the vertical axis. And STILL the neutral point hasn't move one tiny bit, confirmed by checking the servo position on the read-out to the right, after pressing the STAR button. I can go from +20 directly to 0 & see no change. Then from 0 to -20 again no change.

So unfortunately I really am not so sure right now. I'll have to read through the manual & try to decipher Sanwa's gibberish & see if I can figure out an answer. But I do know that the Expo function is doing just exactly what you asked, not slowing the transit speed, but is slowing or reducing the servo horn movement. Remember, the Expo function alters the relationship between steering wheel movement & servo horn movement such that (e.g.) if you set Expo to -50% & then move the steering wheel to wherever it needs to be so that the servo is at 50% of its physical range, the actual time it takes for the servo to get to that point will not be altered. All that is happening is that the operator has to move the steering wheel further in its travel. If we could control the Tx via a computer so that we could just tell it to go directly from 0% to 50% we should find that the transit time has not changed as the computer doesn't have to contend with moving steering wheels, guessing where 50% is, etc. (obviously).

Hope that helps Chris.

And if anyone can give me a reasonable definition or explanation of just what Adjustable Rate Control does or why/when one would want to use it I'd really love to find out.

Does anyone know of a screen protector for the main screen? I thought I read somewhere on here that a cell phone one fits near perfect.

I can tell you about the screen protector I have on both my M11 & M11x that don't fit near perfect, they fit absolutely perfect.:nod: It's called Crystal ScreenGuard & I bought mine from ebay for $8.

Absolutely invisible, didn't get a single air bubble on either Tx, absolutely cannot notice it in any way unless looking extremely closely at the very edge of the screen, where the protective layer edge is. I am extremely happy with mine & can recommend them with 100% knowledge that you will not be disappointed. If you can't find it on ebay let me know & I'll see if I can find it for ya. Buy one, you won't regret it.

Yeah if you could find it that would be great! I have been looking everywhere. Thank you!!!

No probs at all mate, here you go: http://www.ebay.com.au/itm/XPRO-Crys...-/290495336009
Enjoy! I know you will.

Thank you!! Ordered!

ARC is simple really. At whatever point you set it for (let's say 50%), from 0-50, the steering moves in a certain rate, then from 50-100, it moves in a different rate. The main difference between ARC and expo is that expo is gradual, where ARC has one sharp inflection point that you can set to whatever you want.

Looking for some help on channel mixing. I'm setting up mechanical brakes with a brushed system and don't know where to start on the tx. Can anyone lead me in the right direction?