My starfire made its maiden last weekend. All went well except on its landing. the gear retracted ok..(so i thought) when it touched down the nose gear collapsed. No big deal...it used the gear door as nose stand/braking ....put a lil angle cut on the door but better the door than the nose of the fuselage.
Upon inspection the nose gear didn't lock in place when it was retracted. when i got home i started testing the retract cycle and was noticing that when the nose gear retracts it has a slight pause/bounce to it just before it locks in place. I really thought that i might have i had my steering wires a lil tight. So to test i disconnected them and still the same issue.
I noticed that the lower the pressure in the system the better it gets and with no air in the system it works just fine. I also noticed that if you hold the nose gear for a sec to let the mains come down first and then let go of nose gear it works fine also.
I though about using a wheel colloar over the tubing to restrict the mains or the nose gear to try and make it work. Will try that at lunch today.

Can someone offer a suggestion to make the nose gear SLAM down and lock......i can make a small 15 sec video of what is actually happening if need be and email it.

There's a set screw that adjusts the slop in the strut block when the gear is down. It's on the cross member that the strut block presses against when the gear is down. You may have to take the retract unit out to get to it. Take about 1/8 to 1/4 turn off this set screw and it will allow the piston arm to slide to the down and lock position easier.

Do you have any restrictors on the air line going to the nose gear?
What kind of valve are you using to actuate the retracts?
It sounds like the air is not able to exhaust the system quickly enough.
I would check for any restrictions in the air lines, fittings, and valves.
If that doesn't work you can always add another spring to the piston in the nose gear retract (several of my jets have required this modification in the past). You can probably get springs directly from Spring Air, but I usually just cut down some hardware store springs to the correct length.

thud driver. Are we talking about spring airs? i must have missed that set screw. There are two set screw that i have messed with...ONE holds the 3/16 piano wire in the strut block and the Second is on the strut to hold the strut to the piano wire.


kevin. No restriction on any of the lines as of yet. And now that you have made the remark that it can't let the air out fast enough makes sense. (on retract it will exhaust air for about a second or so before anything happens) I really don't think there is a restriction in the air lines because they retract up very nice and quickly. (100-120 psi)


The valve i got with the spring airs would not exhaust any air what so ever. Made me think i had bad retracts there for a lil while until i tried the standard robart retract valve.(I STILL HAVE THE OLD VALVE) Then all started working well. I have remove the restrictors totally on the robart valve to make sure it could exhaust. I have capped off the down leg on the robart valve since spring airs don't use the down side. Was that a wrong thing to do. I can't fill the tank if i don't

thanks guys.....
sean rushing

I suspect that the robart valve is part of your problem. It sounds like you set it up correctly to actuate the spring airs, but the problem is that the robart valve exhausts it's air through the limited space between the valve body and the shuttle. This is usually not a problem with air-up/down retracts because the exhaust air is being forced through by the relatively constant pressure of compressed air, but with spring down retracts the force of the spring lessens as it reaches the end of it's travel and the force applied to the exhaust air lessens as well. It will still be moved out, but not as quickly and if there is any opposite force on the system (such as the force of ram air moving against the gear leg) the spring might not be able to overpower both of the opposing forces.
I don't like the valves that spring air is supplying with thier systems now, the ones they used to use work much better and that is what I always used.
You can get them directly from the manufacturer if you like.
http://www.clippard.com/store/displa....asp?sku=TV-2S
or give Spring air a call and see if they still have any.

The set screw that Thud driver is talking about is a limit screw in the crossbar at the front of some of the spring air retracts. It is used to prevent slop in the pivot block with the gear down. Not all series of spring air retracts have this on them. The problem with the set screw is that if it is adjusted incorrectly the gear will come down, but the trunioun will not be able to slide all the way to the locked position. It does not sound like this is your problem.

I second what Thud Driver asked. Check the screw first before you start buying parts. Yes there is a set screw to make sure the strut does not woble around when it's in the down and locked position.


Turbulence

I have had this problem a bunch of times.

I believe it is the set screw that is on the wheel collar that holds the 3/16 wire in the gear block. It touches the end of the retract just enough that it will sometimes bind on coming down. Just turn the wheel collar on the 3/16 sideways a bit or grind a bit of the set screw.

I hope I explained it correctly.

Adil

Yes the set screw on the wheel collar can interfer as well. Maybe not all springair's have the set screw on the cross member, but on the ones that do, an incorrect setting can keep the gear from locking. This set srew is on virually all my units and I have 4 sets. In fact I just readjusted one on my #109 nose gear last week.

BVM used to have a mod on his web pages that showed how to modify the robart valve to let the air escape more quickly. You would have to do a little grinding. The springair valve will let the air exhaust, it also escapes around the actuator pin but you have to get the input/output lines on the correct barbs.

Do most of you guys use air to make the gear go down on the Spring air retracts or do you just use the spring in the cylinder to make them go down?

Carl

Springair 500 series are the only ones with air both ways. All others are air up & spring down with no air connection to the down side.

I have looked all over one of the mains. (easier to take out) I am not able to find a set screw. I could be wrong here...but i really think kevin has hit it right on the head. I tried some more at lunch and with the air line off....IT POPS DOWN EVERYTIME WITH NO HESITATION AND LOCKS(this is with me manually pushing the nose retract into its retracted position.) I noticed that if i put in a 130 psi.....it has more of a bounce when it let s go then it does let say with 80 psi. and in turn makes a lil more sense that as air depletes from the canister the retract starts to work better.. So i am pretty sure that it has something to do with the robart valve not exhausting quick enough. But man.....the new valve that come with just refuses to exhaust. With the new valve the legs come down halfway and stop dead. JUST NO EXHAUST..

I started tearing into retract. HOW TO GET INTO WHERE THE SPRING IS AT... im trying to be careful and not break anything as I go.

I am gonna mess with it some more tonight when i get off. Nose gear is gonna be a lil difficult to get out.
thanks again
sean rushing

Sean,

If the problem (as you mentioned in your first post) is with the nose gear, taking the main gear does not make sense. The wheel collars and set screws that people are talking about only exist on the nose gear.

After reading and re-reading, it sounds like the exhaust is not fast enough and the spring takes over first and then has to wait for the pressure to drop. I suggest you find the exhaust control on the Robart valve and open it as much as you can.

I'd still look into the set screws etc because there is definitely a problem with the nose gear as it is not locking down when the mains are. As long as there is exhaust, the spring will lock the gear as long as it is not being stopped by the cross member or getting stuck on the collar set screw.

Good luck.

Adil

So do you reccomend using air down on the Spring Air 500's. What is the down side of just using air up and spring down on these.

Carl

ok guys..i now know what you are talking about. THAT SET SCREW IS NOT BINDING/HOLDING ANY THING UP. I CAN TAKE THE AIR HOSE OFF AND MANUALLY PUSH THE RETRACT UP. IT WILL LOCK INTO PLACE WITH NO BOUNCE. My problem hasn't been that the retract won't lock it just seems that is slows or has a slight hesitation as it get close to locking and like kevin said...with the ram air hitting it....and then the hesitation...was enough to keep it from having enough UMPH to lock into place.

I THINK WE HAVE IDENTIFIED THE PROBLEM.....NOW I JUST HAVE TO FIX IT.

any suggestions. Has anyone had the problem with the newer valve that now comes with spring airs not exhausting right.

I just went to bvms site. He still has the mod up for making the robart retract exhaust a lil quicker. Im gonna give it a go. I noticed that his is blue and mine is RED. I WANT TO MAKE SURE THAT FILING THE FLAT SPOT UP FRONT IS THE RIGHT PLACE TO DO IT..
again thanks everyone

I likes Spring Airs' old toggle switch. I never had any problems with it.
Ultra Precision makes a special control valve for Spring Air that adjusts the speed similar to the new Robart valve. I've got one on my 1/5 scale P-39 (see my gallery). I had problems with the long nose strut on the P-39 catching too much wind and had to take the cylinder off the nose unit and I added another spring inside. It still doesn't lock until it's on final and just about to touch down.

But I think your problem will be solved with the right control valve. When I get around to building my JMP Starfire, I'm thinking about letting the nose gear retract forward.

hey guys my valve is a lil different than the one bvms site. He only has 2 orings and mine has 3

should i place the flat spot in the same place anyways.

If I'm not mistaken, the red Robart valve has adjustments, needle valves, for how fast the air flows through it on each side. Shouldn't you look at that first before modifying it? You should remove the needles completely for full exhaust flow. Least that's what my instructions say.


jcarl - even though the Springair web site says it's the 500's that are air both ways, I believe it's actually the 800's. Springair's claim to fame is that you get the gear down even when the air system leaks. OTOH, the springs are not always sufficient for every case, particularly if you're using the gear to move/hold doors. A properly set up 2 way system works just as reliably. I choose for strength, suitability & size before one way or two way.

They were never on this jet. I pulled this valve from my CBM f-16.....and they plane only flew once. I STILL HAVE IT in ONE PIECE.....but needless to say i got fed up with it.

when the spring air valve wouldn't work right i tried the robart valve. Those needle type screw are not there. THANKS THOUGH..

SHOULD I PUT THE FLAT SPOT IN THE SAME SPOT AS BV SHOWS.

Can't say if you should flat spot it or not. Probably not as it appears the exhaust air goes out through the needle areas and not the ends. A flat spot might not do anything. Looks like the 3 o-ring system keeps the air inside and forces it through the needles. You could look at drilling out the exhaust ports, but that's at your own risk.

Just to check for brain fade, I went out to the garage and checked all my Springair mains. Of 8 main gear units, six had set screws and two didn't. The ones without had black cross members, whatever that means. All the nose units had a set screw.

You said something about 130 psi. I run 80 to 100 psi. You need just enough to get them up and keep them up, nothing extra for down.

i appreciate you keeping up and posting replies so fast. I normally don't put that much in there. ussually around 100 or so.... But i didn pump it up real high to see if there was a change. There was, the hesitation/bounce was a lil more than ussual. Then i begin to notice that as the tank got lower on air the gear would work better. At the time it didn't ring a bell that the air wasn't coming out fast enough.

Hmm what to do now...

Just to chime in with another opinion here, I only use 80 lbs of air in my Springairs. too much air will make 'em hang up, sometimes.

Ok guys ...the flat spot didn't work....BUT what did work was to drill out the exhaust port.(thanks thud)..quit a bit. THEY NOW SLAM DOWN AND LOCK.

I am sure the flat spot works on the older style with only 2 orings..but with the new 3 oring style .....YOU MUST DRILL OUT THE EXHAUST PORT if you want to use a robart retract valve with spring airs.

again thanks alot.