Ive noticed that there seems to be a preference toward external horns. why is that? has anyone had problems with torque tubes?

someone? anyone?

BVM told me that they use torque tubes on his F-80 for the flaps. The servo is in the fuse.. This is for the EDF version, I don't know about the turbine version.

I don't like them personally because they are a pain to install, overtime they develop slop because of metal on metal wear, they have a certain amount of flex to them and there are better ways to do concealed linkages (twist drive system ...forgot the official name).

I think it is because external horns are, 1) Very easy to install and rig, 2) Very very effective, with minimum play/slop. Both important qualities in todays high performance ARF jets.

Torque tubes on the other hand have the advantage of being 1) Internal, (low drag). 2) Invisible. The down side is they are much harder to install, and, if not done corretly can induce play/slop.

However, if torque tubes are designed and installed well they are just as effective as direct linkage. All the BVM Bandits (except the BARF) use internal torque tubes on elevator, and these are some of the fastest jets around.

And for scale fidelity, torque tubes are the only option.

Roger

RDS - Rotary Drive System.

http://www.irfmachineworks.com/rds/

Ok, this is just what I thought. I guess it just depends on scale vs convenience. external linkages a huge eyesore. torque tubes a huge butt hurt source.
I havent worked with the RDS system but looking at it, The first thing that jumps out at me is although it is direct drive, the rod length may possibly introduce a torsional spring effect.

I think the other good thing about external horns is that you see them all the time and (IF) one is loose or broke from transporting you see it rather than finding out in the air.

My 2 cents

Thank you Sean, the acronym had escaped me!!!

This should eliviate any of your concerns:

http://www.hauninger.gmxhome.de/hobb...g/RDS/RDS.html

It does act as a torque rod, but much more torque is required than your servo would handle. ie. your servo would fail before the rod would twist.