Problem rigging Tri-Gear steering

[dcazier]

I have rigged my rudder cables per the plans and have just completed installing the tri-gear engine mount for an AeroVee turbo engine. There is a pushrod from the rudder pedals that goes through the firewall and attaches to the steering fork for the nose wheel. According to the plans, you adjust the length of the pushrod such that it fits with the rudder pedals in the neutral position and the nosewheel fork centered. After adjusting and installing the pushrod, I pushed on the rudder pedals to confirm that the tail rudder still goes from stop to stop and that the nosewheel turns from stop to stop. When pushing full right rudder, the tail rudder indeed goes to the stop and the nosewheel turns right to the stop. However, when I then push full left rudder, the tail rudder goes to the stop, but the nosewheel only centers itself (does not turn to the left). I must have done something wrong, but I have checked the rigging numerous times and can't understand why the nosewheel will not turn to the left. Has anyone else had this issue? Any suggestions on where I might have gone wrong?

[Area 51%]

I believe what's going on is related to the design itself, and not a rigging faux pas.

I haven't installed my cables yet, but can see my installation acting the same (or worse) than yours. I say worse because the cables have to pass through the mixer on my Waiex.

The RH rudder pedal is connected directly to the steering link via the pushrod. Stepping on the RH pedal immediately initiates a reaction from the nose wheel. And drags the rudder along with it due to the cable link.
Depressing the LH pedal pulls the rudder first, then the rudder pulls on the RH cable that's connected to the RH pedal that's connected to the steering link. KISS principal on the Right..........Rube Goldberg on the Left.

The inability of the system to deflect the wheel to the left is (at least in part) related to cable tension and or elasticity in the system. That's not to say you should tighten the cables till they snap to get a positive result.

I would think there to be sufficient tug on the steering linkage to produce a left turn while the buggy is in motion and the lower thrust washer is no longer in contact with the bushing which may be causing too much friction to operate properly.

You might try removing the suspension spring and see what happens.

[dcazier]

Thanks so much for taking the time to make this well thought out reply.
Your analysis makes a lot of sense. I think I will try placing weight on the engine mount to simulate the engine being in place to compress the suspension spring. I will then push the aircraft while someone in the cockpit pushes left rudder to see if it indeed turns. I will keep you posted.

[Area 51%]

Please do keep in mind my favorite T-Shirt says: I make Sh#t up.

[dcazier]

I received the following email from the engineering department at Sonex Aircraft:

"Good evening Dan,
 
I would confirm rudder inputs. (disconnect nose wheel steering pushrod from pedal)
• neutral pedal results in a neutral rudder
• full left rudder pedal input results in full rudder deflection (hitting the stops at the tail) and the same for right input.
 
If that is all good then we can move to the nose gear steering.
• Connect steering pushrod.
• Verify neutral pedals result in a straight nose wheel. Adjust rod end as needed
◦ Note using Chalk line to mark center line of the aircraft is a great way to verify the nose wheel is straight. 
• Now verify nose wheel travel left and right with no weight on the gear.
• If you still are not getting a left turn add some “preload” to the front spring by adding a washer.
◦ The washer should go between the spring and SNX-C02-07. You may have to experiment with different thicknesses to get your desired result. 
 
Also note- Aircraft operation procedure with the nose wheel steering. Don’t force the pedals left or right while not moving, rather apply normal pedal pressure and slowly start to roll forward."

(Since I have confirmed that the rudder itself is rigged correctly, I will try adding the preload as he suggested and see if that works. I will report back with the results)
 

[dcazier]

I added a preload between the front spring and SNX-C02-07 with 4 washers (total thickness of approx 1/2"). With no weight on the nosewheel, when I press on the right rudder pedal, the rudder goes to the stop and the nosewheel turns right to the stop. When I then press on the left rudder pedal, the left rudder goes to the stop and the nosewheel turns to the left about 3/4 of the way to the stop. I think it is likely, now that the left turns starts, when the aircraft is rolling, it will probably turn to the stop. I will report the results later.