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HomeAircraftHelicopterMain Discussion › rev max limiter
12-07-2004 11:32 PM  13 years agoPost 21
Simon Brown

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gary / alexander.
I asked if alexander can give you some pointers on how to do a 0 lag setup for two reasons. 1: so you can get the best from the unit and 2: because I do not know how that is actually possible while retaining a powerful punchy pitch for dynamic 3d.

I would assume you would start with full power climb outs in both inverted and normal? tacho and drop the pitch until you get a perfect no change climb.
What I don't get is that unless you back off the pitch at top a bit more, what happens when you do climbing metronomes!.
So the pitch is hammering between full neg and full postive to punch the machine back and forth but the added cyclic load is going in on top.

Mixers can;t help as full power is matched to the pitch but cyclic is the additional load. So it will lag due to the extra load. Clearly no unit can give more than full power. So lag it will have to

Continuous abuse can pull the engine down more.

there can be lots of repeated loading of cyclics while pitch is at full.

Does one therefore have to back the pitch off more than the point where no lag occurs on climbout, so leaving room for the extra cyclic loads to be catered for by the engine?

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12-07-2004 11:41 PM  13 years agoPost 22
Sceadu Abuser

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So how experienced do we have to be before we are good enough to get the best from the unit?
Maybe only Curtis himself could do that!

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12-07-2004 11:44 PM  13 years agoPost 23
RussD

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Hi....

Is this a new type of bushtucker challange?
If the Rev Max truly has 0 Rpm lag I will eat the Rev Lock. Ade will want to see this so I guess he will be trying very hard with me to reach that magical setting.

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12-07-2004 11:47 PM  13 years agoPost 24
RussD

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Hi Colin,

We are talking 10 rpm initial bog when executing an aggresive manouver.

No Daddy tonight...... are you 'Home-alone'?

Scarry!!!

R.

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12-07-2004 11:47 PM  13 years agoPost 25
Simon Brown

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ade
IN a way you have put the same thought I have in that.
Especially RPM recovery after pushing it just that little bit too hard
We all do that
See, if we watch AS and every one who gives it big time grief to their machines, all of them load to get the dramatic stuff.
Remember Curtis. He really rips his helis.. Alan does too.
Sudden yanking stops.. Engine groans.. There are obvious extremes but in normal modern 3d we are all working the machines hard. We can always do with more power in the engine as no matter how much power we have, we work them to that and more.
We have to work the head hard and use the power and torque of the engine many a time to get those agressive 3d fun things we get the smiles from.

Ok, not bog the heck out of it, but am very sure 10rpm is not even close to the lags we get
nothing will compensate for a sudden load of pitch and cyclic which full power can not maintain.

0 lag during 3d flight has to be unatainable. If you are going to go for that, I think you will be either flying it softer and having to watch the inputs or back off the pitch curve to allow for the combination of loads.
Which I am sure will give the heli a soft lack luster responce.

So this is why i think Alexander needs to help with his method of setup.
If he can explain where he starts, what he considers and mixer levels etc, you can all learn and get the best 0 lag, and we all can to the extent that if you get 0 lag, thus we can all get that, sell revlock and get the revmax..
If you can not get that, with Alexanders help, he can maybe fine tune the advice until you do.

I do think we need proper informed guidence please..

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12-07-2004 11:49 PM  13 years agoPost 26
Sceadu Abuser

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If you need help I'll be glad to help you...but don't you think there are enough topics on this? Test it, and if you have any problems contact me and we'll see if we can get them sorted out. Then draw a conclusion. I would do the same for a revlock. Seems like the best way to do it?
Thanx for that I wanted to post it with your permission.

As you state int there, "but don't you think there are enough topics on this?"

if this is the case then how come you JUMP on every oppertunity to RAM the Revmax down everybodys and anybodys throat.

dear oh dear some people never learn!!!

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12-07-2004 11:59 PM  13 years agoPost 27
Simon Brown

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Dear oh dear

Sceadu abuser

I was asking if Alexander can give us setup advice as to how he goes about it, so we can all get the best from the revmax over here

Not some PM..
Could he post a setup guide one where he starts, what he looks to acheive at each stage and how much mixing he finds is required.
We need to know the limiter setting and the desired head speed

With this knowlegable advice being on this thread I thought it would benefit us and get this 0 lag sorted!.

And what happens.. He decided not to post on this thread!.. thanks

Wonderful, so he keeps is 0 lag setup private.. cheers.

I think that in the UK there are indeed very few who have the knowledge. Would have been for something postive to come from a bloody thread of this topic..

Maybe Alexander can rise about Sceadu abusers comments and just post his thoughts on setup before he retires from revlock / revmax threads. At least he can go out on a positive!.. please!

si

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12-08-2004 12:00 AM  13 years agoPost 28
Sceadu Abuser

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As regards for setting up I have gone through all the possible ways off setting up a Revmax now. And if I am unable to get Zero lag in all conditions which is what you have been claming, I would most definitely need your help as I believe it is not possible.

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12-08-2004 12:06 AM  13 years agoPost 29
Simon Brown

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As regards for setting up I have gone through all the possible ways off setting up a Revmax now. And if I am unable to get Zero lag in all conditions which is what you have been claming, I would most definitely need your help as I believe it is not possible.
Exactly.. so rather than spending time, trying to get a 0 lag setup, how about asking someone who has and can tell us the best way.

Why do you insist in inventing the wheel when they have done it to the best results!

I do hope Alexander can post his setup guide, as I reckon Sceadu abuser isn't going to be able to set it up to that level.

I don;t understand how to get that. I was hoping to gain the knowlege from this thread. it would make a refreshing change, would it not!!

Si

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12-08-2004 12:15 AM  13 years agoPost 30
BigChopper

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oh no, not again

0 lag is not possible, not even by theory... in a control loop situation there will always be a finite delay..

It doesn't matter if its a revlock or a revmax, there is always non zero lag...

to claim 0 lag is just BS...

More beer, barmaid

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12-08-2004 12:19 AM  13 years agoPost 31
Simon Brown

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Set your throttle curves very high
What sort of percentage are we talking about here? 60% plus?
and is thee a V in the curve at all or more a flat line at high ish?
set your curve 10 rpm higher than the limit value
Ok so what we need to do is have the limiter always be holding it back rather than only when it over speeds.. But only by a small amount rather than full bore... ?
Add throttle to cyclic mixes as needed (until the bogging stops). You may also want to use throttle to tail rotor mixing.
Could you have a look at your tranny and give what you have ended up with here.. Just examples I know and relvant to blades, engine etc, . but it would be a guide..

Sorry I missed that post.. I was a bit dumb struck with Sceadu abusers usual tones.. but at least he might be able to understand these ideas.

For sure, Gary etc have a starting point. I reckon they would have matched climb out pitch, then added mixers and left it at that, rather than over setting the throttle curve 10rpm above..

cheers. i think maybe a positive has come from this.. Time for the lads to give that a go..

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12-08-2004 12:27 AM  13 years agoPost 32
BigChopper

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How can anyone overset a throttle curve by 10rpm exactly?

The fact that talking about oversetting a curve by 10rpm just seems like BS..let face it the average tacho is no more accurate than +/-100rpm at best...


10rpm my arse.. (a$$).

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12-08-2004 12:37 AM  13 years agoPost 33
Simon Brown

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Big chopper...

If you have a sky tach from Minature aircraft or the Model avionics unit which Alexander probably has you can clearly set it 10rpm higher.

You would set the head speed at what ever.. say 1850 as per the tacho you own. ok it might not be 100% acurate, BUT when you then come back to raise the speed, you would use the same tacho..
And those view jobbies are expensive and at least accurate from one use to the next..

I am hoping to get an example of mixing so we can understand the backing throttle authority being used.

if the curve is initially set to get the desired head speed, then raised, then the revmax is always clipping the top. not just when it over speeds.. As it is actually over speeding all the time.

Add in throttle mixing and in a way the unit is possibly sort of, swamped with extra throttle inputs, again clipping most of the time, but having the power on top.
And he did say you have to have a fast servo or faster than pitch is poss.

I can see where this is coming from.
Loads of fast throttle mostly more than usual and the revmax clipping.

fair enough, if that gives 0 lag we might actually find it is as good as a revlock is..

Si

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12-08-2004 12:41 AM  13 years agoPost 34
Simon Brown

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100rpm!

WOW.. ok. but that is quite a bit as a percentage..

So indeed, the revmax is clipping all the time, and on top goes mixing.

Nought wrong with that I guess, if it gets the best from the product..

I would think that in general when pilots have seen the revmax, they would think that you simply hae your proper usual curves will well matched mixers, and then simply add the revmax to clip the over speed..

Clearly with this basic idea we would get lag.. Pumping things up sorts it?? Sceadu abuser, gary.. give it a go..

Maybe this technique needs to be put in future instructions as a tip..

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12-08-2004 12:44 AM  13 years agoPost 35
Sceadu Abuser

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but this way unless the helly is only hovering the Revmax will be "clipping" alot of the time and hence bring and a lag

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12-08-2004 12:45 AM  13 years agoPost 36
Sceadu Abuser

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sorry typing crap at this time of night you get what I mean

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12-08-2004 12:46 AM  13 years agoPost 37
BigChopper

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And those view jobbies are expensive and at least accurate from one use to the next..
Mmmmm.. are they? I'm not always entirely convinced.. none of the spinning disc controllers are based on any kind of accurate reference... any time I use one they always seem to change their mind, +/-100rpm even when there are no setting differences on the heli?

The electronics in these gadgets are crude, to say the least.. you cannot expect accuracy with these babies...

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12-08-2004 12:47 AM  13 years agoPost 38
MJWS

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Zero lag refers to an underspeed condition where the Rev-Max is not active. It does not and can not lag. It is completely inert at this point.

It MUST lag when controlling overspeed, as BigChopper put it so eloquently. There is a control loop involved, therefore delay. Period.

The 10 rpm or 10% overspeed in your curve sounds like total rubbish. Overspeed is overspeed, the sensor sees rpm... it has no way of knowing whether you overshot by 10% or 50% (this would be mechanically dependant)... it just sees that the rpm has exceeded a limit and responds as quickly as it can.

I don't have much time on mine as it is -17C here right now. Bottom line is I want it to LAG only when reducing speed. A few extra rpm will not hurt my flying style.

All of these new products are great. Nothing like a Holy War to obufuscate simple data.

Mike

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12-08-2004 01:01 AM  13 years agoPost 39
Simon Brown

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I have had some more setup on a PM, which I really think needs to be known if those who are about to set revmax up want to get the same results as alexander..


Mixers only relevant to that one 90 machine and engine combo.. but worth seeing the levels as a basic example..
Here is my throttle curve for idle up: 100, 70, 57, 70, 100
Throttle to Fore/Aft mixing: 30%
Throttle to Roll mixing: 30%
Throttle to tail rotor mixing: 0%, 0% 0% 20% 25%
And to my question about throttle levels and v curves...
To setup the limit rpm you can go 100% across the curve if you wish however I just raised mine to where I knew it would scream with the limiter off,
In a way we can see that the best way to set the revmax is the principle we have discussed else where. In that 100% flat line or slightly less creates a different style of operation to what we might have perceived.

In that you need to swamp the unit so it perminantly clips. thus if the engine under speeds, the revmax will release the throttle. So it now compensates for underspeed.
BUT while it is doing that, if the under speed is due to cyclic inputs, fairly postive mixers bang in more throttle to carry it through.

If one did cap the back curve at 100% maybe this would not work as well as less with mixers? afterall if it was 100% full then mixers would be irrelivant..

On other thought occurs

Steven Gerrard set his revmax originally to 100% flat throttle.
When we discussed the pros and cons of full bore behind a curve, he went away and altered his curves to a more 'expected' setting.

He made them as he would normally, then set the limiter a few rpm higher.
He clearly felt after test flights that it gained from the changed. He reckoned he got less lag, and more power..

This is confusing sometimes.. but we do have alexanders full setup to consider now..

si

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12-08-2004 01:10 AM  13 years agoPost 40
Simon Brown

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MJWS
Zero lag refers to an underspeed condition where the Rev-Max is not active. It does not and can not lag. It is completely inert at this point.
Not exactly. See when you now look at how Alexander sets it up, this is not the case. it is almost never "inert".

See, if it is swamped with throttle perminatly, then it is always clipping..So when the fan drops due to load, (underspeed) the revmax lets the throttle out like a govenor does which compensates for underspeed.

With me.. Revmax is not being used as just a limited as you think.

A clever way of making the revmax regulate underspeed aswell as over speed.

Si

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HomeAircraftHelicopterMain Discussion › rev max limiter
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