General aviation force feedback yoke for Cessna sim

[Cessna172sim]

You've got me re-thinking my design. Using more of Ian's original design as you are may far simplify things. The universal joint positioned where the FFB shaft connects to the 172 yoke answers the issue of angular change between the yoke shaft and the FFB shaft as the y column moves through its arc. How are you allowing for the change in the FFB shaft angle as this occurs back at the FFB chassis? Will you be mounting Ian's FFB chassis on a pivot?

I sent my suggestions to Ian couple weeks ago. He agreed that it could be possible to connect the force unit directly behind C172 Y-column with 2 pin joints. He actually made me a rough sketch that seems very logical. Here's the plan that we are now following:
untitled.jpg

As we are using the original upper engine cowling the force unit will not be visible from the cockpit.

Also at this point we got so many electric components inside the fuselage and very near the control column it would be basically impossible to make extra room for new electronics, encoders and motors. With the current plan we don't need any extra space since the force unit will be behind all current electronic components.

The only thing Ian pointed that the pin joint points must be tight enough (similar for the ones I pasted in my previous reply) for this setup to work properly. Although we might end up loosing some of the force from the motors you have to remember that the engines are still pretty powerful so I don't see this is a problem either.

[Tom_G_2010]

I sent my suggestions to Ian couple weeks ago. He agreed that it could be possible to connect the force unit directly behind C172 Y-column with 2 pin joints. He actually made me a rough sketch that seems very logical. Here's the plan that we are now following:
untitled.jpg

As we are using the original upper engine cowling the force unit will not be visible from the cockpit.

Also at this point we got so many electric components inside the fuselage and very near the control column it would be basically impossible to make extra room for new electronics, encoders and motors. With the current plant we don't need any extra space since the force unit will be behind all current electronic components.

The only thing Ian pointed that the pin joint points must be tight enough (similar for the ones I pasted in my previous reply) for this setup to work properly. Although we might end up loosing some of the force from the motors you have to remember that the engines are still pretty powerful so I don't see this is a problem either.

THANKS! That pin joint on the back edge of the FFB chassis is what I was thinking about. This is so much simpler than what I was considering! AS for hiding it under the engine cowl. I've been on an e-Bay hunt for an affordable one for several months now with no luck. I'm going to start calling the junk yards around the U.S. and explain that all I need is an upper cowl skin and it does not need to be perfect or airworthy only clean enough to be repairable for my use. Maybe I'll get lucky . . .

[Cessna172sim]

Good luck for your hunt. I got mine with pure luck from Finland. The part was airworthy and I still got it with appr. 200$. There should be plenty of spares over there. I can still tell you that it makes a huge difference for flying when you can see the actual nose and virtual prop. especially in turns and landings.

Have you checked this one yet. I bought a door handle from them.
http://aircraftpartsandsalvage.com/

[Tom_G_2010]

. . . Have you checked this one yet. I bought a door handle from them.
http://aircraftpartsandsalvage.com/

I purchased a couple switches, a flap lever, and a landing gear lever form them. Great to do business with. They'll be among the first I go back to when I start the new hunt for the cowl.

[geneb]

Doesn't the base of that yoke connect to either a pushrod or a set of control cables that go to the elevator? If so, why not build a box at the back of the cockpit that uses the original connection system?
g.

[Tom_G_2010]

Doesn't the base of that yoke connect to either a pushrod or a set of control cables that go to the elevator? If so, why not build a box at the back of the cockpit that uses the original connection system?
g.

It connects to an ~18" pushrod that goes to a cam to convert it to a pair of opposing cables. I had looked at that but all the mechanical advantage favors the pilot (as you would expect) and going the other way which the FFB would need to do would require quite a bit of gearing down to reverse that and regain the leverage need to apply force at the controls. I didn't see that as practical.

Ian's documentation emphasizes free movement and minimal friction on the controls. I'm even concerned about the existing mechanical resistance in the factory aileron linkage between the two yoke shafts and pondering how to reduce that. The Y bar setup is designed to accomplish three things: 1. Provide linked dual controls; 2. Provide optimal mechanical advantage to the pilot/co-pilot; 3. leave clearance behind the MIP for all instruments and avionics.

Numbers 2 and 3 make for some interesting challenges when it comes to providing FFB to the controls. That's why I think OP's idea is better than the others I've considered. As I said, my only concern is the drag in the aileron linkage. It would be easy to simplify that linkage provided a direct cable between the yoke shafts cleared all the instruments and avionics when applying full up elevator, but I'm not sure that there is in fact enough clearance.

[Cessna172sim]

It connects to an ~18" pushrod that goes to a cam to convert it to a pair of opposing cables. I had looked at that but all the mechanical advantage favors the pilot (as you would expect) and going the other way which the FFB would need to do would require quite a bit of gearing down to reverse that and regain the leverage need to apply force at the controls. I didn't see that as practical.

Ian's documentation emphasizes free movement and minimal friction on the controls. I'm even concerned about the existing mechanical resistance in the factory aileron linkage between the two yoke shafts and pondering how to reduce that. The Y bar setup is designed to accomplish three things: 1. Provide linked dual controls; 2. Provide optimal mechanical advantage to the pilot/co-pilot; 3. leave clearance behind the MIP for all instruments and avionics.

Numbers 2 and 3 make for some interesting challenges when it comes to providing FFB to the controls. That's why I think OP's idea is better than the others I've considered. As I said, my only concern is the drag in the aileron linkage. It would be easy to simplify that linkage provided a direct cable between the yoke shafts cleared all the instruments and avionics when applying full up elevator, but I'm not sure that there is in fact enough clearance.

At the moment our yoke (elevator and aileron) is centered with normal springs. After FFB is connected all springs are removed to prevent any unwanted and opposite friction. According to the original plans there should be plenty of force available from the motors and referring Ian's email he adviced that it's even possible to double the force with extra cooling. Not tested but should theoretically be possible.

In our solution there will be minimum amount of extra cables, gearing, etc. that I would assume to create more friction = more power needed from the FFB motors. As far as I remember, when there's no any springs or cables connected to the Y-column and all parts are clean/greased, the friction (aileron + elevator) is not so big.

(If) the FFB motor power is anything like the GA Frasca trainers I have been test flying you have to use huge amount of opposite force against the yoke if the plane is not trimmed correctly. With this kind of force the yoke friction is nothing. Of course I cannot tell what's the case with this DIY unit.

As far as I can remember from real life PPL flying, in C172 the most powerful control surface forces affects the elevator. This should be the one that should be working as real as possible. Then comes the ailerons and at the end the rudders.

[IanH1960]

Hi OP,

Sorry I haven't looked in earlier - been busy.

The forces generated by the unit in its default setup are described on the web page - elevator push/pull to about 9 kgf (~20lbs), aileron one handed force about 4.5kgf (~10 lbs). On my test yoke these levels of force are quite tiring to sustain for any length of time and there is a stong urge to trim the forces out when they arise in flight. These forces are however a good deal less than in commercial CL systems - but I guess their use in commercial systems is for flying with simulated systems failures - eg engine out etc, where sustained loading at high levels might be experienced.

In general the most effective way to increase the loading would be to increase the gearing ratios - eg fitting planetary gearheads to the motors would provide a factor of 2, 3 or 4 on the loading without additional electrical loading on the cards and motors. The cards however have capacity for 2x loading by changing their programming - although this will take the current draws above their ( and the motor's) continuous ratings - so would need care and forced air cooling to prevent overheating in circumstances where the higher loads were sustained for more than the length of a normal flight manouevre.

I'm going to test this once I get my hands an a suitable PC style fan that I can fit over the card heatsinks.

On the effects of mechanism on the force feel I was concerned that existing friction, cogging or general stickiness etc in the control mechanisms would affect adversly the force feel because I felt they have made a difference in my various experiments. However a 747 sim builder in Dublin has just finished retro-fitting his existing flight controls with the FFB system - I've made up a quick web page showing some details -

http://buggies.builtforfun.co.uk/Sim...-Customers.php

The force feel on this retro-fitted approach is very smooth (I visited on Tuesday) - better than I thought it might be given all the existing mechanism. So my feeling now is that so long as the existing control mechanisms are themselves smooth and friction free there is a good chance the FFB system will perform well when fitted retrospectively. But there will always be a need for care in the design and interfacing. And we did a bit of tuning to get things set up properly - I altered the card programming slightly to increase the vibration magnitudes to deal with the added inertia of his existing control mechanisms.

PS the builder of the 747 sim finds the vibration effects the FFB brings as one of the biggest suprises - simulated engine and ground vibration comes up through all the controls and varies in intensity with engine thrust, runway speed etc. Throttling up on takeoff for example feeds vibrations/shaking through to your hands and feet - and to an extent up through the flight deck structure. It sort of brings the controls to life - I can still picture the big grin on his face!

Ian

[Cessna172sim]

Hi OP,

Sorry I haven't looked in earlier - been busy.

The forces generated by the unit in its default setup are described on the web page - elevator push/pull to about 9 kgf (~20lbs), aileron one handed force about 4.5kgf (~10 lbs). On my test yoke these levels of force are quite tiring to sustain for any length of time and there is a stong urge to trim the forces out when they arise in flight. These forces are however a good deal less than in commercial CL systems - but I guess their use in commercial systems is for flying with simulated systems failures - eg engine out etc, where sustained loading at high levels might be experienced.

In general the most effective way to increase the loading would be to increase the gearing ratios - eg fitting planetary gearheads to the motors would provide a factor of 2, 3 or 4 on the loading without additional electrical loading on the cards and motors. The cards however have capacity for 2x loading by changing their programming - although this will take the current draws above their ( and the motor's) continuous ratings - so would need care and forced air cooling to prevent overheating in circumstances where the higher loads were sustained for more than the length of a normal flight manouevre.

I'm going to test this once I get my hands an a suitable PC style fan that I can fit over the card heatsinks.

On the effects of mechanism on the force feel I was concerned that existing friction, cogging or general stickiness etc in the control mechanisms would affect adversly the force feel because I felt they have made a difference in my various experiments. However a 747 sim builder in Dublin has just finished retro-fitting his existing flight controls with the FFB system - I've made up a quick web page showing some details -

http://buggies.builtforfun.co.uk/Sim...-Customers.php

The force feel on this retro-fitted approach is very smooth (I visited on Tuesday) - better than I thought it might be given all the existing mechanism. So my feeling now is that so long as the existing control mechanisms are themselves smooth and friction free there is a good chance the FFB system will perform well when fitted retrospectively. But there will always be a need for care in the design and interfacing. And we did a bit of tuning to get things set up properly - I altered the card programming slightly to increase the vibration magnitudes to deal with the added inertia of his existing control mechanisms.

PS the builder of the 747 sim finds the vibration effects the FFB brings as one of the biggest suprises - simulated engine and ground vibration comes up through all the controls and varies in intensity with engine thrust, runway speed etc. Throttling up on takeoff for example feeds vibrations/shaking through to your hands and feet - and to an extent up through the flight deck structure. It sort of brings the controls to life - I can still picture the big grin on his face!

Ian

Hi Ian,
Thank you once again for your detailed information. I'm sure there will be many happy grins here also when the FFB unit is built and operational.

[Cessna172sim]

BTW, can you independently control the 'shaker' option of the FFB unit?

Since our sim is full of fragile electronic connection, like DIY avionics the control column shake could deattach solderings and cable connections.

Of cource if you could adjust the shake functions to minimal but still senseable level it would be ideal.

For the rest of the cockpit shaking we use ButtKicker 2.

BR,
OP