RAF & Sparrowhawk steering

[CLS447]

While redesigning my nosewheel & steering system on my SxS AC, I have been comparing notes with the RAF & SH's system.

Today I went to see Larry B.'s new machine & made an eye opening discovery.

What actually turns the nosewheel on these machines?

When the right pedal on the pilots side is pushed, the rod on the left passenger's pedal pushes back on the steering "knuckle". How does this happen?

Well, the rudder cable from the R pilot pedal is pulled, this rotates the rudder & pulls back on the left pass. pedal which then pushes on the Knuckle & turns the wheel. And visa versa.

I guess you all knew that! I just didn't realize the the stresses of turning the nosewheel were actually on the rudder cables!

Obviously it works fine, but if one were to lose a rudder cable, you would also lose your nosewheel steering.

No big deal, but with all this stuff about crimping & bungee cords on the pedals it just makes me feel better about having push/pull teleflex cables!

My system I am building on my AC is different in the aspect that my nosewheel is in front of, not behind my pedals, like the RAF.

I will have it so that when I push the pilot right pedal my steering rod
will directly push the steering knuckle to the right. When I push the pilot left pedal the movement will be transfered to the passenger left pedal via the connecting rod & then directly push the knuckle to the left.

The rudder cables are an entirely different thing. I could lose steering but still have rudder control or lose rudder & still have steering. Or I could just smash into the ground & lose everything!

If you lose one rudder cable , you could still use the rudder with the push/pull cable. (heel/toe).

No big deal , just a recent observation that I have never heard anyone talk about before. Thanks

[CLS447]

I didn't mean to knock their system or upset anyone just was hoping to hear some other opinions.... pro or con.

Does anyone have anything to say about it ... even if it's "shut the hell up"?

Another thing about both systems, Is it true that you can tighten the steering by tightening the 3/4" nylock nut beneath the knuckle? How tight do you guys like to make it? Or do you like 0 friction on the nosewheel? C'mon anybody!

These are important subjects to me right now.

[mceagle]

Personally I like zero friction on the nose wheel and I like it directly linked to the rudder pedals. I have heard many disagree with this type of system for various reasons but I would be happy to challenge anyone to a centreline tracking contest on take off and landing, and in any wind conditions, with this system. Both students and genuine pilots found it very easy to use. If you are worried about breaking a cable, link the two pedals together. However, no amount of redundancy will make up for poor workmanship.

[CLS447]

Thanks Tim, maybe we can get this dicussion going,

I just always assumed the RAF was directly connected to the nosewheel. Then I found out that it is actually the rudder cable that really does all the steering.

If they would use springs & nuts on the other side of the knuckle rod ends, then it would be a push/pull rod setup. I wonder if this would be an improvement or not?

Has anyone tried this? Then even if a rudder cable was disconnected you could still steer the nosewheel. This would also relieve some of the stresses placed on the cables. Hmmm....

[Harry_S.]

Chris:

The RAF steering is directly off the rudder pedals. Threaded rods are connected to a pitman arm which is solidly connected to the nosewheel shaft.

The rudder cables control only the moveable rudder.

I'm like Tim...I like it and have had no problems.


Cheers :)

[CLS447]

Harry , unless your setup is different ,you better get under that dash & have a closer look! When you push the pilot side right pedal, Does that pull on the pitman arm or does the left passenger side push on the arm.

If you answered left side push, then what makes that side push?

Maybe the one I am looking at is set up wrong. The SH we are working on is not that far yet. I will definitely have to refer to the manuals.

Which side of the pitman arm rod ends are your springs on....front side or back side?

Get me straight on this ,could you Harry?

[Aussie_Paul]

....out of the Raf consruction manual. I added the rudder cable info myself.

When you push on either of the right rudder pedals the nose wheel is steered via the springs, and the rudder cables are direct from the pedals. The spring idea is good only if you have a decent trailing nosewheel, but a cable failure will allow a lot of "non pilot input rudder" to one side.

Centering springs back at the rudder end is the best scenario to allow for rudder cable failure.

Aussie Paul. :)

[CLS447]

Thanks Paul, then Larry's is set up correctly .

OK, then from those pics, tell me , do those rods push rearward on the pitman or pull forward on the pitman?

If they push rearward against the springs, How then by pushing on the pilot side right pedal,does this steer the wheel to the right?

[Aussie_Paul]

Thanks Paul, then Larry's is set up correctly .

OK, then from those pics, tell me , do those rods push rearward on the pitman or pull forward on the pitman?

If they push rearward against the springs, How then by pushing on the pilot side right pedal,does this steer the wheel to the right?


They push rearward on the pitman arm Chris.

I am sure that it relys on the rudder cables to to pull the left pedal back and so push the pitman arm rearward. :confused:

Aussie Paul. :)

[Harry_S.]

Chris, me lad...with all due respect...I don't have to take a closer look under the dash of my RAF, as you suggested...I built my RAf and have maintained it and have flown it for 7 years now. :D

There are no centering springs for the rudder/rudder pedals on the RAF. I believe the two small springs you have reference to, are installed on the rods to the pitman arm. These springs are installed fwd. of the arm and the rod end bearing. These springs are compressed on the initial installation and adjustment of the rods...to maintain the the left offset of the nosewheel steering. The purpose of these springs is also to maintain the space between the adjustment nuts.

I'll try to describe the rudder pedal setup. The rudder pedals consist of two separate, square steel tube welded assys. One pedal assy has the pilot's L/H pedal and the passenger side L/H pedal; the other pedal assy. has the R/H pedal for both positions.

When the pedal assy's. are bolted down, the pilot's R/H pedal has a rod attached from the low corner of the pedal to the pilot's side af the pitman arm. The passenger side of the L/H pedal has a rod going to the passenger side of the pitman arm.

So; if you can picture that setup, you will see that when the pilot presses the R/H pedal, he in fact pulls forward on the pitman arm and the nosewheel and the rudder deflects to the right...and vice versa.

Centering the rudder, in flight, is by foot pressure of the pilot. I have the Snider Rudder Anti-Servo Tab installed on my RAF and it works fine.


Cheers :)

[CLS447]

Harry, Let's work through this together, peaceably.

First of all I believe the spring are there to absorb sideway bumps on the nosewheel & for landings with rudder inputs, also.

Now for a couple of basic tests.... If you remove the nylock nuts on the end of the allthread rods, does it still steer exactly the same?

2. If you disconnect one of the rudder cables does it still steer the same?

3. If you do both of these things, I think that the rod will just pull right through the rod end on the pitman arm & fall to the floor without ever moving the wheel or the opposite pedal.


Since you are performing an annual on your machine , this would be a perfect time to check those points anyway. Lube cables , inspect crimps, lube pedal to cable pivot points, check nosewheel for slop & so on & so on.

I am curious to see if adding springs on the back side of rod end also wil work/help.

Your response would be helpful. How about you Stan F., since you two are obviously the only people who fly RAFs or at least the only ones who post! Oh & aussie Paul !

[Aussie_Paul]

Chris, me lad...with all due respect...I don't have to take a closer look under the dash of my RAF, as you suggested...I built my RAf and have maintained it and have flown it for 7 years now. :D

There are no centering springs for the rudder/rudder pedals on the RAF. I believe the two small springs you have reference to, are installed on the rods to the pitman arm. These springs are installed fwd. of the arm and the rod end bearing. These springs are compressed on the initial installation and adjustment of the rods...to maintain the the left offset of the nosewheel steering. The purpose of these springs is also to maintain the space between the adjustment nuts.

I'll try to describe the rudder pedal setup. The rudder pedals consist of two separate, square steel tube welded assys. One pedal assy has the pilot's L/H pedal and the passenger side L/H pedal; the other pedal assy. has the R/H pedal for both positions.

When the pedal assy's. are bolted down, the pilot's R/H pedal has a rod attached from the low corner of the pedal to the pilot's side af the pitman arm. The passenger side of the L/H pedal has a rod going to the passenger side of the pitman arm.

So; if you can picture that setup, you will see that when the pilot presses the R/H pedal, he in fact pulls forward on the pitman arm and the nosewheel and the rudder deflects to the right...and vice versa.

Centering the rudder, in flight, is by foot pressure of the pilot. I have the Snider Rudder Anti-Servo Tab installed on my RAF and it works fine.


Cheers :)

From the schematics I posted you can see that the compression springs are there for 2 purposes. The main one is to keep the 2 degrees left nose wheel position, the second being to keep some pressure in the cables.

If the nose wheel was a trailing design the the springs would also allow self aligning of the nose wheel to the direction of travel if the nose wheel touched the ground.

Harry, the right rudder pedal does not pull the pitman arm, the left pedal pushes the pitman arm.

Chris I will have a look and see what having another spring behond the piman arm would do. I might just have to get some all thread and springs to try it.

Aussie Paul. :)

[CLS447]

Thanks Paul. I did another test with Larry the other day.... I had him hold the pedals centered. Then I grabbed the nosewheel & twisted it left & right. The spring allowed it to move without the pedals moving. I figured that this was for some sideways shock absorbancy.

When setting up the nosewheel, Is the pitman arm installed perfectly perpendicular with the nosewheel or is that where the 2 degrees left is applied?

Or is that done with the rod adjustment alone?

Why is the 2 degrees left used ? And would that be with the pedals centered?

I am really trying to understand why RAF decided to push the opposite side of the pitman using the rudder cables, when they could put the springs on the back & actually pull the pitman directly, without the rudder cables. Those rods would be stronger in tension than they are in compression.

I know that the pitman arm rodends are 3/8" but they are used with a side load. It has recently been dicussed that they are only designed for tension/compression.

I believe the Sparrowhawk is exactly the same. If it needed improvement, I figured SH would have done it. If it ain't broke don't fix it, might have been the thought.
Or maybe there was no thought used at all....just copy it.

I can tell you that there are more parts to the SH setup... mostly in the addition of bronze bushings installed in the pitman arm so the 3/8" rod ends swivel freely. Not a bad idea after examining the RAF setup where the rod ends are tightened directly to the pitman. The rod end itself did not swivel at all.

I have been told that SH is changing their rudder cables over to an exposed system with pulleys....I wonder why? I know it was a real pain bending the guide tubes and routing the rudder cables through the keels.

I sure am anxious to here Harry's thoughts & findings. How about you Stan?

I know that for me this was a bit of an eye opener!

[StanFoster]

Chris: The two degrees left nosewheel setup is due to the fact that some right rudder is being held on takeoff. This tends to keep the nosewheel more straight with the runway as is leaves the surface. If the nosewheel did not have this 2 degree offset to the left..and was straight...then when the nosewheel came off...the right rudder would turn it right a little..and if it came back down on the runway,...then the nose of the RAF would be pulling right.

Stan

[teiland]

As far as I know the current plan is to change to external cables over pulleys on the Sparrowhawk. David and I did this mod to my machine quite a while back and I have been lobbying for it. I have found the pedal pressures to be too high to suit me with the stock setup. I have sent pictures to many of my SH customers showing this, but if any others would like them, I will be glad to send.

[Aussie_Paul]

Terry, please send to paulbruty@lexicon.net

Thanks, Aussie Paul. :)

[Harry_S.]

Harry, the right rudder pedal does not pull the pitman arm, the left pedal pushes the pitman arm.


Aussie Paul. :)

Touche' Paul...my brain fart...I was sittin' here at the keyboard trying to visualize the pedal effect on the pitman arm and got screwed up. Thanks.


Cheers
:)

[Harry_S.]

Chris:

You got it. I'm too old to do anything other than peaceably. :D

To answer your queries:

A. Sideway bumps? :confused:

1. Sure does.

2. Sure does.

3. Nope...L/H maybe; R/H no...per my setup. I think your simulating a rudder
cable failure?!

Adding springs aft of the pitman arm...mabe/maybe not help what...
centering the pedals? I don't have space to add any springs, aft of the
pitman arm anyway.

As Stan said, the left offset was to...as RAF factory stated...to help the
low time RAF pilot to compensate for the torque on takeoff. An experienced
pilot would not need the offset.

On the ground, the offset does help on L/H turns but hinders R/H turn
radius quite a bit.


Cheers :)

[Aussie_Paul]

Touche' Paul...my brain fart...Cheers

Not a problem Harry. Now I don't feel so alone!!!! LOL :D

Aussie Paul. :)

[GyroRon]

Why not make it simple and light Chris and make it a castoring wheel and use indivdual wheel braking for steering.

[Gary_in_Orygun]

I'm attaching a picture that I took during my RAF 2000 build process. You could disconnect the rudder cables from the rudder pedals and taxi around all day with perfect steering.

Sorry the picture isn't better.

[CLS447]

Gary, I don't want to keep repeating myself but it seems you don't understand what steers the wheel either. So disconnect your cables & try it!

You will see that with the cables disconnected, when you push forward on the pilot's right pedal, the empty all thread rod will slide forward,what an inch or two?, before that nylock nut would even contact the pitman arm rod end. Also there would be no backwards push from the passengers left pedal unless you would hook your right heel on it & pull back because it is pulled back by the rudder cable!

Perfect steering .....I doubt it ! Now Stop, Think, Reread & try it !

Terry, what in your opinion causes such high pressures? Maybe the nosewheel swivels to tightly or the 3/4" nylock on the shaft was overtightened? This is adjustable ,No?

If you diconnect the nosewheel steering rods & just operate the rudder with the pedals , are the pressures still high? Why?

Back to Harry, no problem we all have brain farts occasionally. But I think I told you that before Paul did !

Thanks

[Aussie_Paul]

Gary, I can't see that happening unless you have the nylocs behind the rod end adjusted tighter than the Raf book says. There is supposed to be some play on each side to allow the springs to compress on one side and extend on the other. The manual says 3/4" to 1". As per attachment.

If you removed the rudder cablkes the pedals would fall forward until the rear nuts hit the rod end.

I am due to replace the inner cables, particularly after what happened to me in the L/Wing!!!!!

I will remove my cables the see what happens.

I thought that I had it very clear from the manual.

Aussie Paul.

[teiland]

Chris, I think the pressure comes naturally from the bending of the cables down through the drop keel, and to maybe an even greater extent from my screwups. I don't think I did a very good job of bending and positioning the tubing in the drop keel.

As the first, I was building before we had complete instructions or drawings, and lots of the modifications. I didn't get the tubes until after the fact, so to speak, and that made it more dificult to install properly.

[CLS447]

Terry,I didn't get that part either... those tubes were a bear!

The more bends in those cables & casings the harder it gets to pull ,right?

How hard is it to turn your nosewheels by themselves? Or how tight do you like them?

I sure would hate to have to replace those cables after the machine is finished!!!!!

Paul, you might be the only guy who gets my purpose for starting this thread.Thanks Mate !

Does it all have a reason ? For me it does . I'll be posting pics soon. If I had been happy with my nosewheel & steering , I would have never looked more than skin deep !

[Aussie_Paul]

Chris, having just experienced an accident due to a rudder cable swage failure, and lost rudder control, I knew axactly what you were getting at.

Aussie Paul. :)

[teiland]

Chris, my nosewheel turns very freely.

Jaap, the AAI engineer, just told me that he is going to a new system of cables over pulleys similar to mine, except he is going to run them inside the keel. That sounds like a great idea to me. It will be a while before this change is implemented, though.

[Harry_S.]

Paul:

I have an interest in your results as well. I may be missing something here??!

Please take a picture of your connecting rod installation as is...before the cable disconnect...and another after a normal taxi and turn sequence...if you don't run into something. :eek: :mad:

You remember back on the original Bensen, you steered by coordinated foot pressure on the steering bar...no springs, no cables?! Simplicity.


Cheers :)

[Aussie_Paul]

I am going out to do that now Harry.

Aussie Paul. :)

[Aussie_Paul]

..... Below are the 2 pics. One before I removed the rudder cables from the rudder end, and one one after.

The systrem was set up as per the Raf manual with 3/4" between the rod end and the rear nut.

All rudder pedals went as far forward as they could and the wheel stayed straight. Not possible to turn at all!!!!!!

I removed one cable first and ended up with full rudder one way!!!!!!

Harry, my Bensen style gyro in 1982 had unitised nosewheel and rudder combined like the aircraft that I flew. No way was I going to try and learn a new way!!!! :D

Doubting Thomas Aussie Paul, who always has to test for himself!!!! :)

[Gary_in_Orygun]

Paul, thanks for the memory refresh. Yes, it has been awhile since I installed my rudder cables.

[CLS447]

I'm just one of those guys that wants to know how things work. I was really surprised when I took a look at this system. I couldn't believe that that "throttle cable " was steering the nosewheel. I don't believe that there is any reason for this! Like anything ...there is always room for improvement.

I hadn't given this much thought until today when Shar asked me"Why does the RAF & SH cross their cables". My machine does not. It took a couple minutes for me to answer. Who else can explain?

[mceagle]

They are back to front compared to a normal Gyro. The right cable connects to the left pedal and the left cable connects to the right pedal. No problem as long as you cross the cables.

[Harry_S.]

Thanks for the pics, Paul.

I can see more clearly now why that fellow up in Canada went in, when the cable turnbuckle failed on the initial takeoff. I don't know what his altitude was at the time he lost his rudder control...do you, perchance?

This may be something to ponder...losing rudder control on takeoff?!

IMO, my reaction will be to chop power and try to steer as best I can with the cyclic, to get to the ground in a level attitude... and forget about the yawing.

What do you think?

Back to your pics...if need be, with no rudder cables...you can steer while taxiing, by straddling the keel with the left foot on the R/H pedal and the right foot on the L/H pedal. Foot pressure would be reversed but it would get you back to the hangar. ;)


Cheers :)

[CLS447]

Harry, still don't get it do you?

This would work if you hooked your heels over the pedals & pulled back with them, not pushing on them. But it would still have slop play back & forth.

Understand?

[Harry_S.]

Chris:

Remember *peaceably*...Nope.

I could taxi...controlled taxi...with no rudder cables.


Cheers :)

[KenSandyEggo]

You can make sharp turns while taxiing by just grabbing a rudder cable near the keel and giving it a tug upward. That locks up that wheel and you can turn on a dime. Of course that won't work if the cable is broken. It's good when you slightly overshoot your turn-off and are too embarrassed to have to taxi a 1/2 mile to the next one because you can't make the turn......especially when there's a line of planes waiting for you to clear the runway so that they can take off.

[Aussie_Paul]

....you cannot taxi at all if you have it set up as per the Raf manual. If you, as I do, only have 1/8th" between the rode ends and the rear nut you would be able to taxy using the normal pedals but as you said with some slop in the steering response. If the distance from the front of the keel to the rear rudder pedal bar were further away than the Raf manual says you would have a little more comtrol.

I changed mine for the pics as you asked me to have it seat up as a standard Raf.

Firebird ain't gonna be like that, I can tell you!!!!!

Aussie Paul. :)

[CLS447]

That's it Paul, Think out of the bun ...I mean square . That's the TACO BELL commercial.

And Harry, calm down, I meant that nicely! :)

[Harry_S.]

I didn't mean to knock their system or upset anyone just was hoping to hear some other opinions.... pro or con.

Does anyone have anything to say about it ... even if it's "shut the hell up"?

Another thing about both systems, Is it true that you can tighten the steering by tightening the 3/4" nylock nut beneath the knuckle? How tight do you guys like to make it? Or do you like 0 friction on the nosewheel? C'mon anybody!

These are important subjects to me right now.


Seems like you asked for it, so...I became the *Devil"s Advocate* for you. ;)

It's Palm Sunday, start of Holy Week...so I'm coming clean. :D


Cheers :)

[CLS447]

Good morning ,Harry!

I guess you meant the part about shutting up. :rolleyes:

I want to thank you & Paul & Gary,& Tim & all for participating in this discussion.

When I started it , I got no responce at all. Sometimes it is like pulling teeth to get people to respond, & I don't know why that is.

If it wasn't for this Forum, I wouldn't be able to type at all, but I didn't let that stop me.

I want to share ideas ,observations ,& everything about gyros, with gyroheads all around the world. Isn't that why we are here?

I just wish that more people would come out of the shadows & not be so shy, & put their thoughts to the keyboard !

[CLS447]

As far as the crossed cables go.... On my machine, when I push the pilots right pedal, it rotates the rod it is mounted to. This rotates a linkage arm on the right side that my cable is attached to & visa versa. So my cables don't have to cross.

But since the RAF & SH connect their cables directly to the pedals, to not have to cross them, they would have to connect them to the outer pedals. Then they would be in the way on the floor.

Ron A. , If you're still following this.... I like a steerable nosewheel, it's all I have known. How much heavier & complex do you think it is? You will have to demonstrate for me how well your diff. braking system works at BD's .