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Digital Throttle Trims

Old 12-30-2002, 02:59 AM
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Flyfalcons
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Default Digital Throttle Trims

I thought I'd get some opinions from you guys on the use of digital throttle trims. I didn't think I would like it when I got my 9C, but have really come to appreciate having a consistent trim, as well as the ability to use a reliable idle-down switch for landing some of my planes that don't slow too well. For example on my Majestic during low power, negative maneuvers the engine has a tough time maintaining enough fuel pressure to keep running. I think this is due to my fuel line routing, but that's another story. If I were to set the idle high enough to keep running, it is way too fast to slow nicely for landing. Using mechanical trims to idle down would increase the chance of me pulling the power back too far and accidentally killing the engine. So now my engine management is done with two switches (idle-down and kill) instead of a mechanical slider. Would like to hear your good/bad experiences with either method.
Old 12-30-2002, 03:23 AM
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JohnW
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Default Ditto

I basically do the same as what you describe. Throttle cut is on a switch and I put my low speed idle setting on my left slider so I can easily (and quickly) adjust the idle point without having to remove my thumbs from the sticks. A little different from your idle up switch in that I have more control with the slider, but still performs the same function.
Old 12-30-2002, 08:16 AM
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Default Digital Throttle Trims

Digital trim is a very good feature but I don't like the feel. It should be like the mechanical trims but with spring action to reset it to centre.

The problem with these, just 2 push button trim is that when you have your comptete attention to the flying plane you don't have the exact idea how much actually and how fast you have moved and you have to rely on the beeps...

On the other hand the mechanical ones are good in such a way that you have the complete feel and control.

These new digital trims should be MECHANICAL WITH SPRING ACTION TO RESET TO CENTRE.
Old 12-30-2002, 10:52 AM
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HarryC
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Default Digital Throttle Trims

Ryan, you are saying that the digital trim is better because you don't use it! You have stopped using the trimmer and use switches instead. Actions speak louder than words, and your actions say that the digi trim is unusable!!

What you describe about using switches to control flight/ground idle and engine cut, is not actuallya question about digi trims versus mechanical trims. My radio has all mechanical trims (which incidentally I much prefer to digi trims) but like you I often program a switch for flight/ground idle, and always have an engine cut switch available. However I never use them. The throttle is set so that full trim is flight idle, pull the trim back to centre notch gives ground idle, and full back is cut. Digi trims provide no tactile information to the pilot so they are forcing you to stop using the trim and to use programmed switches instead, whereas my mechanical trim give me the choice of using switches or trims. Digi trims are removing your choice.

Harry
Old 12-30-2002, 11:18 AM
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MikeL
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Default Digital Throttle Trims

I've got a radio with digital trim on the throttle, and one without. To me it makes no difference. I don't fly anything too fancy, and thankfully my engines aren't too sensitive. I do like digital trim for some things (adjustable steps, for one), and I do like analog trim for others (tactile feel, knowing just where I have it set). One of these days some bright engineer is going to figure out how to combine the attributes, and then we'll all be happy (yeah, right!).
Old 12-30-2002, 01:02 PM
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Default Digital Throttle Trims

have both,like the digital trim better.
Old 12-30-2002, 01:28 PM
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Edgar Perez
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Default Digital Throttle Trims

Mechanical for throttle
Digital for other functions (best when you share your transmitter with several planes)

JR got it right in their 10X (I don't own one. I fly Futaba)
Old 12-30-2002, 02:53 PM
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HarryC
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Default Digital Throttle Trims

Originally posted by MikeL
One of these days some bright engineer is going to figure out how to combine the attributes, and then we'll all be happy (yeah, right!).
The software to set up trims is a separate issue to whether or not the trims are mechanical or digital. My radio has mechanical trims with extensive software for programming those trims. Most other makes only bother including software for trims when they put in digi trims, thus fooling people into thinking that it is digi trims that bring them the benefits.

I can choose auto or manual trim, and it is selectable independently for each control, specific to each model memory. In autotrim I move the mechanical trims as normal. After I switch the Tx off, I move the trims back to the centre notch. The Tx automatically alters the electronics to the trimmer position so that when I switch on again the servos are at the trimmed position even though the trim lever is in the centre. I can choose to have auto-trim on the 3 primary controls and manual (classic trim!) on the throttle. Manual trim behaves as you would expect but with all the added features listed below:

Mechanical trims with variable steps, i.e. sensitivity, is on my radio. Perhaps it works differently to digi trims, what mine allows is setting the trim travel as a % of total travel, at normal I choose 20% but can have trim all the way up to 100% which makes it same as the stick. This effects how sensitive the trim is for each click, which is what digi trim steps do. I don’t know if digi reduces the number of steps as step size increases, to keep the total trim travel the same? I use 20% as the default for all controls except the throttle where I coarsen or refine the sensitivity of the trim to suit the motor during pre-flight testing.

A claimed advantage of digi trims is that when you come back to the model at some later time, the trims just have to be the same, they can’t have been knocked. My mechanical trims have the same end effect. The software memorises where the trims are when I switch off. When I switch on again, or change model memory, it checks the trims against the last position. If the trims have been moved, the screen automatically shows which trim has to be moved, and where to, to be where it was last time. The Tx will not complete booting up or the memory change, until the trims are back where they should be. In practice this only takes about 2 – 3 seconds to do, not as good as zero seconds with digi trims, but 2-3 seconds is nothing in the grand scheme of things and is a price I am happy to pay as I prefer mechanical trims.

For the 3 primary controls, I can choose the trim to be standard trim or centre trim, and again this can be set independently for each individual control and is special to each individual model memory. Standard trim is the old fashioned version where the trim lever affects the servo even if the control stick is at full movement, so it alters the travel. Centre trim is a bit like a controls version of throttle’s idle trim. The trim affects the servo position at neutral but progressively loses effect over the stick movement so that by full stick in either direction it has no effect and therefore the control surfaces’s total travel is not affected. Centre trim is the radio manufacturer’s default setting.

When setting up a mixer I can choose whether the trim setting is included or excluded from the mixer input.

It’s not something I want to do, but my mechanical trims can be crossed like digi trims so that the elevator trim is next to throttle stick and throttle trim next to elevator stick etc.

My mechanical trims can be decoupled in software from the controls, and become full channel controllers in their own right. I have never thought of a reason why I would want to but there we go, just another example of mechanical trims being as adaptable as digi trims if you are given the software. In truth, the trims are controls in their own right with their own inputs to the processor, but by default they are not assigned to a transmitted channel and are mixed at a low percentage to one of the control sticks. That is how they can have such extensive software all of their own.

So I get all the advantages of mechanical trims combined with software that gives me the advantages associated with digi trims, and in fact much more extensive trim software than most digi trim Txs.

Harry
Old 12-30-2002, 04:50 PM
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Default Digital Throttle Trims

HarryC

What radio you have?
Old 12-30-2002, 05:37 PM
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Default Digital Throttle Trims

Harry, regarding trim memory, there is at least one radio out there that has a mechanical trim memory system where once you set the trims you hit the memory switch and recenter the trims. Works well, and really is a must for using multiple models.

But as far as the poll goes with digital throttle trim, the reason I am starting to like it is because I can get the exact same idle with deadly accuracy every single flight, versus having to find it and trying to remember exactly how many 'clicks' of idle it takes to achieve perfect consistency. If there is a trend, such as when the engine is breaking in, I can lower or increase the idle a 'beep' at a time (which can be a smaller step than with a mechanical trim). Therefore the trim button is completely usable, but I'm not using it every single flight to find the right idle. I think there are advantages and disadvantages to every method; digi trim just seems to work best for my style.
Old 12-30-2002, 06:21 PM
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Default Digital Throttle Trims

Originally posted by guaraguao
HarryC

What radio you have?
Multiplex, but that's not the point.

The point is that all the software capabilities, and more, are available with mechanical trims. It is just that most manufacturers don't make software available with mechanical trims so people are confusing the digi trim button with the software and thinking they are the same thing.

Harry
Old 12-30-2002, 06:36 PM
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Default Digital Throttle Trims

Originally posted by Flyfalcons
there is at least one radio out there that has a mechanical trim memory system where once you set the trims you hit the memory switch and recenter the trims.
I can think of a Hitec radio that does that. But what I am talking of is a radio where you don't even have to press a memory switch, it just does it.

Originally posted by Flyfalcons
I can get the exact same idle with deadly accuracy every single flight, versus having to find it and trying to remember exactly how many 'clicks' of idle it takes to achieve perfect consistency.
I can use idle-up and t-cut switches if I want to. It is not digi trim buttons that give you those, it is software and it can be applied to digi or mechanical trims. It is simply a fact that most makes have chosen not to make the software available with mechanical trim Txs, but there is no technical reason why not since some makes do have all the software with mechanical trims.

Originally posted by Flyfalcons
I can lower or increase the idle a 'beep' at a time (which can be a smaller step than with a mechanical trim
I can make each click of trim as small as 0.05% of travel and I will be surprised if your digi trim step can be as small as that! I doubt the servo can even resolve that far down.

Harry
Old 12-30-2002, 08:49 PM
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AJF 2
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Default Digital Throttle Trims

I always thought I wanted digitial trims all around-- then I got a radio with them and found out that (in my opinion) it is a bell that I thought I wanted untill I used it--- then I found out I wanted mech trims instead. Harry--does the 3030 have the same feature as your 4000. I hope so. Maybe I will find out if it ever gets here.
Old 12-30-2002, 09:01 PM
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MikeL
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Default Digital Throttle Trims

Originally posted by HarryC
The point is that all the software capabilities, and more, are available with mechanical trims. It is just that most manufacturers don't make software available with mechanical trims so people are confusing the digi trim button with the software and thinking they are the same thing.
Which manufacturers don't? My mechanical 8103 does, and I can't recall if my 783 did or not. I know the Stylus does it. There aren't really all that many radios still being made that don't have digital trims (non-computer ones, anyway). The only ones I can think of that may not have trim memory are perhaps the Hitec Flash series the low end JR 5 channel.
Old 12-30-2002, 10:19 PM
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Default Digital Throttle Trims

I have a Hitec flash-5 and I love the digital trims I set them for each individual model as I am flying and the settings are automatically locked in for that model, no need to push any buttons to lock them in. I hope there's no radio out there that claims to have multi model memory and does not let you set the trims easily for each model, that would be worthless.
Old 12-30-2002, 10:54 PM
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Default Digital Throttle Trims

Originally posted by AJF 2
Harry--does the 3030 have the same feature as your 4000. I hope so. Maybe I will find out if it ever gets here.
'Fraid not. It has the memory screen for when you switch on or alter memories, but all the rest of the trim software is 4000 only.

Harry
Old 12-30-2002, 11:01 PM
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HarryC
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Default Digital Throttle Trims

Originally posted by MikeL
Which manufacturers don't? My mechanical 8103 does, and I can't recall if my 783 did or not.
Not just the trim memory Mike, but all the other "goodies" like manual/auto trim, step sensitivity, cross trims, standard/centre trims etc. I am not aware of anyone else offering that with mechanical trims, but the point is that it can be done, such things are not exclusive to using the sprung button associated with digi trims. So given the software, you can keep the positional feedback and speed of a mechanical trim with all the best programming attributes of a digi trim.

I have just realised that by decoupling the trim from the control and sending down its own dedicated channel I can do what someone asked on here a few months back, that is have the trim operate its own servo to control a trailing edge trim tab.

Harry

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