Mechanical pitch Trim compensator

jm-urbani

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Hi all,
it is always at the end that we have to sort out "details" that reveal not to be esay to sort out
I am looking for a simple idea to build a mechanical trim for my tandem ...
what kind system are you using ( I don't want any electrical device) ?
thx
 
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jm-urbani

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Hi Again,

My question did not bring many people attention (((-:, I understand it is not really exciting ..

sorry to insist I know it is a stupid question but I need help

searching a method to mechanically pull/release/hold my rotor trim (compensator) cable I started wondering if any of the gyro pilots from this forum are using such a device where one has to put one's hand off the throttle to turn the trim wheel ?

Is it ergonomically realistic to release the throttle to trim during especially the ascent ?

(my throttle keeps where it is when I put off my hand from it of course)


1144763

1144764
 
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ventana7

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Hi Again,

My question did not bring many people attention (((-:, I understand it is not really exciting ..

sorry to insist I know it is a stupid question but I need help

searching a method to mechanically pull/release/hold my rotor trim (compensator) cable I started wondering if any of the gyro pilots from this forum are using such a device where one has to put one's hand off the throttle to turn the trim wheel ?

Is it ergonomically realistic to release the throttle to trim during especially the ascent ?

(my throttle keeps where it is when I put off my hand from it of course)


View attachment 1144763

View attachment 1144764
T
 

ventana7

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The Xenon uses a really simple system. Two springs attached to a string pulling on the control tube. The spring comes up to the console where it can be put into a tiny sailboat jammer. It weighs ounces, is beautifully simple and works. Takes a second to adjust. I’ll post @ pic when I get a chance

Rob
 

Kolibri

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Uh, wow, Rob, sorry, but I can't get excited about that design.
It's like correcting a car pulling to one side by hooking a bungee cord to the steering wheel (vs. aligning the front end).

Gyro trim should have its own linkage attached directly to the rotorhead, all separated from the control system.
Kind of like "aligning the front end".
That way, trim can be used as emergency secondary control.

The RAF, for example, has a particularly inappropriate trim system, which adds force to the control arms/push tubes.
Some owners have added a second gimbal arm on the torque tube rear dedicated to the trim springs. That's a prudent mod, IMO.
 

Vance

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The Xenon uses a really simple system. Two springs attached to a string pulling on the control tube. The spring comes up to the console where it can be put into a tiny sailboat jammer. It weighs ounces, is beautifully simple and works. Takes a second to adjust. I’ll post @ pic when I get a chance

Rob
That does sound cleaver Rob. Thank you for sharing it.
 

All_In

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Not sure over 10,000+ logged FW, 260+ ultralights, sailplane, hang-gliders
Not sure I understand the system I know what a sailboat jammer is. Looking forward to the pictures or drawings.
 

ventana7

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In the attached photo you will see it right behind the black throttle handle. There is a tiny brown wooden ball- this is just to make it easier to pull, the string is attached to the ball. You see this is just resting on a tiny sailboat cam cleat. In flight I would pull the ball towards me which would be down in the photo as I fly from the right seat. I would pull the string into the cam cleat which would hold the string. More pull towards me equlas more nose up trim. The part you are not seeing is the string goes vertically down into the tunnel. Directly below where the string disappears from your view it goes down about 6" to the bottom of the tunnel where there is a 1" diameter pulley changing the diretion of the srtring from vertical to running back towards the firewall. The end of the string is attached to a spring. The other end of the spring basically pulls on one part of the control tube coming from the cyclic. 1144808DSC_0013sm.jpg
 

ventana7

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The next generation Xenons had a second one for side to side trim and I will likely get around to installing that one of these days.

Sorry not sure why it uploaded the picture twice.
 
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ventana7

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Uh, wow, Rob, sorry, but I can't get excited about that design.
It's like correcting a car pulling to one side by hooking a bungee cord to the steering wheel (vs. aligning the front end).

Gyro trim should have its own linkage attached directly to the rotorhead, all separated from the control system.
Kind of like "aligning the front end".
That way, trim can be used as emergency secondary control.

The RAF, for example, has a particularly inappropriate trim system, which adds force to the control arms/push tubes.
Some owners have added a second gimbal arm on the torque tube rear dedicated to the trim springs. That's a prudent mod, IMO.
Yes it is always possible to add more weight, complexity and redundancy to any system.

Rob
 

jm-urbani

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Hi,
the small string blocked by a sailboat jammer is a creative idéa !
I am just wondering if it is not difficult to tighten and release the rope finely ?
a trim must not be an on/off system
must you pull hard on the string ?
maybe on a tandem one has to pull harder ?
 

ventana7

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Hi,
the small string blocked by a sailboat jammer is a creative idéa !
I am just wondering if it is not difficult to tighten and release the rope finely ?
a trim must not be an on/off system
must you pull hard on the string ?
maybe on a tandem one has to pull harder ?
No it takes minimal effort and is quite precise. When my machine was new
I changed out the factory spring fora stronger one I bought at the hardware store for a buck

Rob
 

ventana7

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One of the few things Raphael who designed the Xenon did well was focus on weight reduction. He literally knew the weight of every nut and washer on the Xenon and came up with creative solutions to keep weight down.

If you look at the GBA Hawk 4 or Sportcopter 2 they took the opposite approach. As Kolibri posted above in this thread, if the trim system goes to the rotor head, then you can use it as an alternative method to control the rotor in the event of control system failure. True but you just added 12 lbs of tubes, cables,nuts, bolts, fittings etc. Now you need a few more Horsepower to get the same performance. A few more horse power means 8 lbs more engine displacement. This means you need an extra Gallon of fuel to have the same distance range. Now you need a slightly bigger fuel tank. Now since you added the extra engine weight, fuel, tankage, etc you really needed not 8 ilbs of bigger engine, but 12 lbs worth, and a beefier frame, larger rotor, etc, etc, etc, Was it worth it to entirely redesign your gyro so your trim system which is supposed to zero out stick force is a probably useless emergency control system?

The Hawk 4 started with a piston engine and ended up with a turbine engine. In the end it cost more than a Bell Jet ranger helicopter and could not hover, thus worthless. Sportcopter 2 went the same route with bigger and bigger engine, bigger airframe etc. I needed a step ladder to get in the SC2.

Rob
 

ventana7

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Hi,
the small string blocked by a sailboat jammer is a creative idéa !
I am just wondering if it is not difficult to tighten and release the rope finely ?
a trim must not be an on/off system
must you pull hard on the string ?
maybe on a tandem one has to pull harder ?
Jim,
Your question about how hard you pull the string got me thinking a bit more. I fly my Xenon with thumb and forefinger lightly on the stick. It lakes only a slight bit of pressure to do an 60 degree bank turn, and only fingertip pressure to come back to straight and level. It may be this light stick force which allows this system to work.

By contrast when I fly a magni Cavalon or Calidus I am astonished at how hard I have to hold the stick and the effort required to turn. I took my last BFR in a Calidus and my arm was exhausted afterwards. It’s possible on a gyro that takes much more stick input to fly you would need a very strong spring and thus harder to pull and more difficult to be precise.

Rob
 

jm-urbani

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thx for help rob,
i hope my 230 kg empty future tandem rotored with a 8.50 m averso won’t require a big trim force
in case the trim force is weak I will try a simple system like the one you are using
weight is the enemy and adding stuff is easy but at the end of the day it does not pay off
how can i calculate the necessary trim force guys ?
thx
 

Vance

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I would see how fast she flies with no trim spring and then add spring till she flies the speed you want jm-urbani.
This will give you an idea of how much force you want and what it will take to make it happen.
Once you get a spring that works you can trim for different speed with holes or a screw.
Once you quantify the force you can see what works.
I ran The Predator for years with no adjustable trim. I found a spring that gave me 65kts and just flew her.
I put the in flight adjustable trim on for clients who seem to like trim.
I have to admit now that I have trim in flight adjustable trim I like it.
I use a liniar actuator that weighs about a pound.
 

jm-urbani

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Hi Vance,
I think your method is the good one
it is interesting to find out you could fly your tandem without ajustable trim
did you fly it without any spring at the beginning ?
 
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Jazzenjohn

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Scott Essex has made some very nice, very lightweight trim adjusters.
 
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