RE: COMP-ARF A-4 BUILD
 

I sent a set to down and locked and they were supposed to try and find a solution but i believe they are probably on the shelf for now.
scott

RE: COMP-ARF A-4 BUILD
 

I think you really need to narrow down what the problem is. You could test the steering cylinder using just air pressure to see how much pressure was required to move it when the aircraft is standing still and when it is moving. Once you have that nailed down, then you could work on sizing the drive cylinders and servo to provide you with that amount of working pressure. With a large BVM or Robart cylinder and an 8711 servo, you could get a heck of a lot of pressure.

Also, you might find that the steering servos are not big enough to move the nose gear with a reasonable pressure (over 150 psi or so and you're going to have to worry about the tubing blowing off the fittings or splitting) and if so, you'll need to see if its possible to mount a bigger cylinder on the gear.

I would think that its a solvable problem with a step-by-step approach...

Bob

RE: COMP-ARF A-4 BUILD
 

Seems like you have it working fine on the bench, then you install it with a ton of weight on nose and it fails after a couple of turns.
I was hoping to get Down and locked to solve it with a electric jack screw of some sort
maybe having a look at Skymasters setup will help.
could just be some shotty cylinders. they are special made for this app. cant sustitute any other ones, at least for the one on the strut.
scott

RE: COMP-ARF A-4 BUILD
 

Almost bit on one of these a little while ago......appears waiting a little longer is definitely warranted. Really to bad, as the Blue Angels version is awesome.

RE: COMP-ARF A-4 BUILD
 

Bill, Ill make you a special deal for two!!! lol!! two for one!!

RE: COMP-ARF A-4 BUILD
 

What about those miniature hydraulic units they used to sell a few years ago, I think it was also used on the Fiberclassics Mig 29, could they be incorporated into this mess?

RE: COMP-ARF A-4 BUILD
 

I've only seen the one detailed photo of the strut at the beginning of this thread and it doesn't show the steering cylinder very closely. It does look like something non-standard though, so I'd begin by figuring out some way to replace it with a standard BVM or like cylinder. Also, does the steerable part of the nose gear itself use ball bearings? If it doesn't, then weight on the nose is going to really increase the pressure needed to move it due to friction. That would have to be fixed too...

The Skymaster strut looks pretty simple, but Likai is a landing gear guru. I don't know who did the one for Comp-ARF...

Note below on the Skymaster one below the simple, standard cylinder and the ball-bearing supported steering yoke...

RE: COMP-ARF A-4 BUILD
 

First off I have only seen the gear a couple times so I thought I would throw out some totally uneducated thoughts out there. One I know that it extends to raise the AOA for takeoff and that is a "wow" factor thing but could that be part of the problem?? would it be possible to fix the leg at a fixed length loose the strut extension wow and then change the motivator for the rotation to something more conventional??? Also if it is binding the way the yoke turns in the strut, following up on Bobs idea, could you steal a bb thrust washer from one of your heli friends and see if that might work? Just throwing it against the wall and seeing if it sticks, Scotty

RE: COMP-ARF A-4 BUILD
 

This gear is essentially the same except for a bit more scale appearing cylinder. The question is what does SkyMaster have on the other end in the fuse that works?

http://i465.photobucket.com/albums/r...t/DSC_0249.jpg

David S

RE: COMP-ARF A-4 BUILD
 

Looks like you may have a line close to being kinked Dave, maybe not statically but you never know under load.

Am I the only one who thinks trusting an air cylinder with steering, which I barely trust with my gear doors, is a little bit off? Is this some kind of precise control air actuator?
But then again, if CompARF put it in there so it must be a good idea right?

Makes no sense, a $10,000+ model with redundancy on everything, and then an air cylinder on steering, because we all know how reliable air cylinders are. I would convert them to electric IMHO.
David

RE: COMP-ARF A-4 BUILD
 

The nose steering cylinder is using oil vs air to actuate, hence it becomes hydraulic. The short line you think is almost kinked is an air line which leads to the nose gear extension for take off. This photo is a very early photo taken at the very beginning of my trials to get the system to work. I am now using a much harder tubing in an attempt to prevent expansion of the tubing under pressure, thus softening the steering, which hasn't worked either.

I think I've found a way to set up steering via the wheel brakes, but I have to reallocate channels in order to make room for an additional two channels to make it work, since I'm currently already using all 12 of the proportional channels on my 14MZ.


David S

RE: COMP-ARF A-4 BUILD
 

Actually, they may be "air cylinders," but they are filled with fluid and the entire system must be filled with fluid or it won't work.

David, I believe that the other side of the system is another cylinder that is connected to a servo - just like I presume that the Comp-ARF one is. Is the steering fork supported on ball bearings?

Do you have a picture of your setup on the drive side?

Bob

RE: COMP-ARF A-4 BUILD
 

Yes, I know it's not scale.[:o] Yes, I know, looks ugly as hell.[:'(] But, I think it's going to work!:D A few more adjustments/additions to stabilize the mount and control rod & I think this beast will be RTF for BITW!:D:D


http://i465.photobucket.com/albums/r...t/DSC_0225.jpg

http://i465.photobucket.com/albums/r...t/DSC_0226.jpg

David S

RE: COMP-ARF A-4 BUILD
 

Dave, for the next step you could probably install a bellcrank next to the steering arm, and keep the servo away at the top, keep only a linkeage visible.

Just a thought.

RE: COMP-ARF A-4 BUILD
 

Sign me up!
paint it white go fly!!
Scott

RE: COMP-ARF A-4 BUILD
 

Ok, David tell everyone where you got the idea from... :)

I am also working on some smaller high torque servos. This should eliminate the ridiculous hydrolic system all together which will save a lot of weight too.

Andy

RE: COMP-ARF A-4 BUILD
 

deeyyyaaammmm that is Ugly!!!! but F'it if it works....paint it white and go fly. :D

RE: COMP-ARF A-4 BUILD
 

I had thought of it as well, but you will need a really strong servo to counter all that weight and it not be too big! hope it will work for BITW.
Scott

RE: COMP-ARF A-4 BUILD
 

Sorry to hear about your troubles guys. I put down a $1000 deposit for an A4 kit but canceled the order after hearing about the problems. So, my loss was only the deposit :(

Would it be possible to use an electric actuator like this one? A 2" stroke with 15 lbs force. Or maybe it's too slow at 1 sec per 1" travel. It will also need a small 12v battery, but those can be made with lightweight LiPo's

http://www.e-motionllc.com/Mini_elec...ms-15-12-2.htm

There may even be faster actuators available. I just did a quick search.

RE: COMP-ARF A-4 BUILD
 

I just realized that those actuators are 11" long LOL. But they are available in much smaller versions

RE: COMP-ARF A-4 BUILD
 

Unbelievable, you guys pay thousands for a superscale jet and have to figure out a nose gear steering cuz the company fufs you over.
Then the only solution on this superscale plane is a servo hanging next to the nosewheel ??!!. I commend the flexibility for solutions but that is disgusting (from a costumer service view) !!
You should get together and fly over there....

RE: COMP-ARF A-4 BUILD
 

I'd try this.

RE: COMP-ARF A-4 BUILD
 

Won't work. That bottom unit extends almost 3" to increase the AOA for takeoff. But thanks for the effort!

David S

RE: COMP-ARF A-4 BUILD
 

OK Scott, I'm following your advice!:D
The 9156 is a Digital Hi Torque servo with 340 oz in at 6v. Should be plenty strong.

http://i465.photobucket.com/albums/r...t/DSC_0227.jpg

http://i465.photobucket.com/albums/r...t/DSC_0229.jpg

David S

RE: COMP-ARF A-4 BUILD
 

paint the servo too!
scott