Guys !

Just of curiosity, how many have actually purchased an A-4 from Carf and what is the status ?

Peter Bang (Denmark) - Missing paint ready to fly - Need info for RC setup and front gear steering

I will update accordingly !


Peter B

Peter,

I took the actual measurements for control throws & CG off of Andreas' A-4 when he flew it at CA Jets last year. I'll post them for you later today.

David S

You can do that - that is the way I have seen pictures of the Skymaster system setup. However, using two cylinders gives you more pressure to operate the system in case you did not get all of the air out - which I think is pretty much impossible to do given that you don't have a way to bleed the system like you do with a full-size hydraulic system. Also, with two cylinders like that, you could put a mix in to move both servos forward a bit when powered up which would pressurize the system to help hold the nose wheel in the commanded position.

Bob

It's about a 1/2" to 5/8" stroke. Very little. See pics:

Andy,
How much room is available between the cylinder now and the strut? I have a few links on small linear actuators, but im not sure if they are small enough

Yeah I checked the linear actuators. They are not short enough. Also they don't have enough power to turn the wheel loaded.

Hi Bob:

Thanks for your answer.

BR.

I have a box of linear actuators. They will not work.

Any way to make a steel cable work? Build a fake steering cylinder that the cable would feed through and attach to the steering tiller.

Have any of you tried with some sort of thrust waster to reduce friction and thereby reducing the front wheel load ?

Peter

As well as the "full scale" T-2C Buckeye and the A-4E

Not so. I flew TA-4F and J models in the Naval Air Training Command in 1980-81. All the jets had operable nose-wheel steering. On the flight deck of the carrier, we did NOT engage nws, instead were 'steered' on the deck by a sailor with a steering bar hooked into the nosewheel assembly. We had to definitely make sure we did not taxi faster than a man could walk!

I later flew A-4E and F models as an adversary pilot. The 'E' had no nosewheel steering at all (diff brakes), but the 'F' model had nws.

Sluggo

True, The Blue Angels used the F model. Here is a pic of the nose gear on a A4F:

David,
I'm very interested in your posts of your A-4 problems, especially of the nose steering problems. I'm having similar problems with my A-4 project (Skymaster). Skymaster, Laiki, BVM, et.al. will not answer my emails requesting parts for the A-4 landing gear. I have dammaged the pistons in the left and right main gear units trying to operate them hydraulically. But that's another story!
Correct me if i'm wrong but i believe that the CARF as well as the Skymaster nose gear steering operate hydraulically. On the surface, this method has good promise of being friction free and very positive with "0" slop. It should operate like any common Automotive/motorcycle hydraulic clutch system. But a little bit of air in the system is a "deal breaker". I have spent literally hours on my system trying to remove every last air bubble but somehow air always seems to creep back in. I noticed on one of your photos what looks like a fairley large air bubble in the line. I have found that a bubble this big in my system renders the steering very sloppy and unresponsive ,especially with weight on the wheel. Since air is easilly compressed, the servo/master cylinder uses quite a bit of travel just compressing the bubble. Ball bearings are not the answer, when the airplane is not moving the increased friction is not in the system but skidding between tire and ground. Like trying to steer your car with the engine off. The servo mounted on the wheel end of the strut looks goofey. I think we can solve this problem ourselves if we can find a way of keeping air out of the system. When my system is air free it is very solid and responsive - it just won't stay that way for very long.

Hey CaptainBob, do you use single or dual "master cylinders" inside the plane?

A couple of other points, someone said side loads on the cylinder causes leaks, they are right!

Second, I found some very hard 4 mm line that I am sure will swell less than most line, especially at 100-125 PSI, but I can't find the link....it was "something "95A" which I assumed was like a Shore rating on elastomers. Rigid line would help too but it is fiddly to bend up.

Seems like if you get a bulletproof way of bleeding it and then it does not leak (letting in air) it would work much better.

I can get all the air out of the system and it will work perfect with one master and one slave, but somehow air creeps back in eventually.
here in lyes another problem: you have to submerge the whole system under fluid to remove air then find a way to instal back in jet with not dismanteling. the tubes are supposed to run down this protective shield to keep the lines from being pinched or cut. this is not possible now because you cannot disconnect lines.
scott

I've got a guy working on a solution with a reservoir like you see on a master cylinder. It will be interesting to see how that works out.

Andy

Just one cylinder.

Ok, how about this.

In order to keep air from leaking into the system, you need to devise a way to have fluid continually running through the system. So in order to keep this flow of fluid, you need a hydraulic pump to flow the fluid, but you also need a way to get fluid in and out of the cylinders.
You would have to install an additional nipple fitting at each end of the cylinders.

You would have the normal line that went between the Master and slave cylinder, but you would also have a "feed" line on each side of the piston on the master cyl. With the pump running, it would pump fluid into the slave cylinder, up the line that runs to the master cylinder and then out of the additional nipple fitting on the master cylinder back to the fluid reservoir. (this would make the fluid flow start at the lowest point of the system and work any air up to the highest point of the system (the reservoir)).

With the pump running fluid through the line constantly, it would always be forcing air out of the system, but since it would be operating on both side of the cylinders, it wouldn't steer the airplane any. The only issue I can see, is it possibly making steering the airplane a bit harder due to the fluid moving.

Thoughts?

That is where I was going with this:

http://morpower.net16.net/index.php?...tegory&path=59

That sounds prohibitively complex. We need to keep it simple, guys. Why can't a static system work? It's done in autos and motorcycles all the time.

Awesome bad news to me!
after leaving a MIG 29 behind, again C-ARF shows up with a new unsolved problem....not even an email reply from them
meantime i am working on other areas and will leave this gear problem to the end.
even worse to me that the steer cylinder came broken from the trip to Brazil (the attachement point of the cylinder to the gear

Interesting thread...

Andy, air getting in seems to be a common problem. Is there a way to allow any air that gets in to escape or vent to a trap? I don't know much about hydraulic systems but I would guess without a circulating pump and system that it may not work unless purged each time etc, so is there a way to let it simply ascend and be trapped above a valve that would vent but close once pressure is applied through the system that is "below" the vent valve? I can make a sketch if this is too confusing, I hope the idea makes sense even if it may not solve the problem.

Good luck,
Dave

I would like to throw my solution into the hat.
I like to keep things simple and use proven techniques.
I worked on a large A4 Gear some years ago for DCU Models. I pulled out an old prof of concept prototype from storage and made some updates to it last week. As you can see its is a simple torque rod arrangement that allows the rod to slide so the shrink link can do its thing. I just tested this for stiffness and it is very positive even with the nylon arm I used. Any production set would have all aluminum components to make it even stiffer.

The good news is this will work just fine the bad news is, the Comp Art retract is not a compatible configuration for the torque rod.

I would need to look at the Comp Arf gear to be able to see if it could be saved or changed in some way. Just PM me if anyone is interested in working on this with Matrix.

Thanks,

Hello guys !

I am doing some work on my A-4 with respect to position lights !

Does anybody off you know what sort of position light the A-4 have in the tail ?

Any info preciated !

Peter B