Spring sizes

[NicD]

Guys - just about to install spings in our control load mechanism. 8 springs in total - 4 forward and 4 to the rear of the control-column connecting tube that runs under the floor. I'm all at sea with what type and size spring to get.

When control columns are pushed forward:
- front springs compress
- rear springs extend

When control columns are pulled backward:
- front springs extend
- rear springs compress

So should I be using compression or tension/extension springs. And any ideas on the spring load rating?

Just another skill area that cockpit building is forcing me to learn! :)

[Trevor Hale]

Nic,

Gwyn is using gas springs, "Screen door closers" and he likes them. Maybe you could try that.

Trev

[Westozy]

Yeah, they work perfectly and the return to centre speed is adjustable.

See http://www.mycockpit.org/photopost/showphoto.php?photo=820

http://www.mycockpit.org/photopost/showphoto.php?photo=821

With push pull springs it's unlikely that you will get a positive centre position which will affect trimming.

Gwyn

[NicD]

Thanks Gwyn. Likes like another engineering marvel there!

I can't quite make out from the pics where your control columns link in - can you explain it further?

Also - do you have an electric trim mechanism hooked up to this?

cheers
Nic

[Westozy]

Here's a pic of the underside, it was taken before I fitted the centering device but you can see the lever arm that I bolted the swing plate to. The 'torque' tube connect pitch motion accurately without any free play and my pitch pot is fitted to the end of this tube.

Under the floor - http://www.mycockpit.org/photopost/showphoto.php?photo=576

Pitch pot - http://www.mycockpit.org/photopost/showphoto.php?photo=624

Original trim drive (Now removed) - http://www.mycockpit.org/photopost/showphoto.php?photo=177&ppuser=305

That should clear it up for you. I don't have electric trim fitted yet although I have made it, it used to be fitted under the radio box. I removed it when I decided to fit my Sim-Boards in there. I have dual pole rocker switches on both yokes wired in parallel and they just send trim up/dn commands to FS through the Sim-Boards. I used dual pole rocker switches so the other contacts of the switch can be used to drive the trim wheels via a 12volt cordless drill motor. I found it wasn't as accurate as directly trimming through FS so I put it on the back burner. (I have a pot attached to my trim wheels through a reduction gearbox in the quad). It was way over the top really, I got a bit carried away making the quad which was my first part I made. There's quite a few redundant parts in the quad since I converted to FDT.

Gwyn