ForcesR

Dan, the O-ring on the pistonis more then likely dry and allowing air to leak by. I had the same problem with one of my Robart retracts. I fixed the problem with pneumatic air tool lubrication oil.<o></o>

<o></o>

Make sure the air pressure in the retract system is at zero PSI. Disconnect the two quick disconnects to the two MLG retracts, take a syringe and put a small amount of pneumatic air tool oil in the syringe. Inject a bit of the oil into the 2 air lines at the quick disconnects. You will see the oil in the tubing as it enters, you only require about an inch in length of oil showing in each air line.<o></o>

<o></o>

Reconnect the 2 quick disconnects, re-pressurize the system, now cycle the gear full up full down as many times as possible. When the gear will no longer cycle due to low air pressure, re-pressure the system again, and recycle the gear until the air pressure is too low to cycle the gear.<o></o>

<o></o>

Re-pressurize the system; take note of the air pressure PSI, leave the system pressurized for an amount of time that you feel is right, then re-check the air pressure PSI. The leak should have either stopped or at least slowed down. If the leak rate has slowed down, then inject more oil into the 2 air lines and repeat the process again. This procedure should stop your air leak if the faulty O-ring was only dry and not previously damaged, torn, cut etc.<o></o>

<o></o>

Let us know if this method solves your leak problem, and good luck be with you

Roger

CorsairJock

My Feedback: (90)

I belive Robart sells air retract rebuild/ repair kits, which include (among other things) 'O' rings, and a special lubricant. Should be available from local hobby shops (probably special order), and Tower Hobbies as well.

SPLIT S

Air tool oil won't hurt the o-rings?

ForcesR

<o></o>

Air tool oil is an ideal lubricant forO-rings made from synthetic materials. Air toolshave synthetic material O-rings similarto the O-rings used inair retracts.

The oilcoats the surface of the O-ring, it will not causedeterioration oftheO-rings,it is notabsorbedby thesynthetic material, thus the O-ring will not swell andpreventthe retractpistons frommoving.

I have usedthe oilto stop leaking retracts since 2008 and have never had a problem with theretract O-rings since using the oil.

Air tool oil is much cheaper to purchase than replacement retract cylinders orO-ring rebuild kits.<o></o>

<o></o>

Also, someof the Robart retract cylinders cannot be taken apart to replace theO-rings, this ismainlydue to the ends of the cylinders having swaged end caps that do not unscrew. The retract cylinder has to be replaced with a new cylinder, which is very costly.
Example: the ROB 605 replacementcylinder costs approximately $45.00 each.

Roger

SPLIT S

Thanks for the info guys. I have some Marvel air tool oil, give it a try tonight.

andernamen

My Feedback: (3)

Don't do it!! I used some pneumatic tool oil in my system and it destroyed the O-rings! The system would no longer hold air and work properly. The o-rings are hard to replace unless you get the exact ones from Robart. There may be some oil that is compatible, just be careful. I would only use what Robart recommends.

CorsairJock

My Feedback: (90)

Just to add my 2 cents: I am retired from a maintenance position at a factory which extensively utilized air cylinders. Some of the so called air-tool lubricants contain alcohol, and/ or other ingredients that will dry out and/ or expand 'O' rings over time.

Lithium grease seems to be an acceptable lubricant. I would stick to lubricants recommended by Robart. Have you tried calling them?

Oldrcbuilder

I too am in (not retired) a maintenance position at plant. When i did rebuild pneumatic actuators we used lithium grease also. Robart recommends "Use white lithium or silicone grease only". Their rebuild packs have silicone grease. Between the two, i would choose lithium, do to silicone's tendency to adhere any particles that touch it.

Mark

Firepower R/C

My Feedback: (10)

It looks like my new Wingspan retracts will be here in a couple of days. After taking a close look at the design drawings, it looks like the new Wingspan rotators take several design cues from the robart 615 design, with a couple major differences. Overall, they look promising.

I have some Robarts for backup, just in case.

ForcesR

Andernamen, you are the first person that has posted a negative response to using air tool oil in a pneumatic retract system that I have read or heardabout in the past 4 years.

I have used Marvel Air Tool Oil to stop airleakagepast retractpistons and aircontrolspool valves.The air retracts on all my aircraft are Robarts, and I have been using Marvel Air Tool Oil since 2008. I have never had an O-ring failure or any issues with the Robarts not working properly since using the oil.

There are numerous posts throughout differentRCsites where people have used Marvel Air Tool Oil to fix air leaks, all have had positive results that I know of. No one has ever reported back that the O-rings in their air retract systems had failed due to using Marvel Air Tool Oil.

Robart is the same as any other company, theywould not recommend usingAir ToolOil because they do not want to be liable for any damage caused,if any,by their recommendation of a product other then what they use during the manufacture and assemblyof their products.

Roger

andernamen

My Feedback: (3)

Roger,

Just passing along my experiences. You of course may do as you wish. I think I bought the stuff at harbor freight, came in a small bottle. It WAS NOT Marvel brand. The type I used DEFINITELY was the cause of the O-rings failing. The O-rings that failed were in the air valve, not the retracts themselves. Fair warning, check compatibility before using air tool oil. Marvel may or may not be fine, but the best way is to stick to what Robart recommends. Good luck and happy flying.

ForcesR

Andernamen, the passing of ones experiences is very important in this hobby, it allows one to make an informed decision on what to use, or not touse. If you ever happen to remember the brand name of the air tool oil you used at the time, please post and let us know, so others may be warned of the consequencesofits use.
Oh, and thank-you for being candid and nottaking the part of an executionerin your reply. It’s so much more pleasant to conductcorrespondence in a civil and courteousmanner.
Best regards and very happy flying to you Sir.<o></o>

SPLIT S

Well I need a cylinder. I talked to Tower where I had purchased them, was told to call Robart which I did. Was told to take the cylinder apart and check for dirt in the o-ring. Found a very slight scratch running lengthwise but nothing else. I figured while I had it apart I would run some 2000 wet/dry trying to use it as a hone. The scratch did come out but made no difference. Testing it under water it looks like a kid blowing bubbles. I ordered a new one from Robart today, hope this one is better. I'll send this one back for repair eventually but would just like to get the gear working since it is the only thing holding me up from flying.

Dan

Firepower R/C

My Feedback: (10)

How much was the new cylinder, if I may ask? I have a set that has clyinders that were glued together incorrectly by some rather handy repairman. I would like to get them going sometime.

SPLIT S

$22.50 (each) + $6.50 shipping.

aghost

My Feedback: (13)

Well, off retracts for a moment and back to flying. I found that my plane needed a bit of up elevator with gear down and flaps deployed for low speed, level flight. In that configuration the plane will balloon a little if its going too fast when first deployed. However as it slows down to the landing pattern speed, the up elevator is needed.

Lifer

My Feedback: (1)

aghost,

Question: Does your transmitter have a setting for servo speed? If so, I have found that using it on flap servos to slow them down really diminishes the ballooning efffect.

Best regards.

aghost

My Feedback: (13)

The Futaba 8fg does not have a setting for servo speed. It does have a feature that has the same effect. i use that. you are correct the slower deployment really diminishes the ballooning.

Firepower R/C

My Feedback: (10)

I received the new Wingspan retracts today. First impression: they look great! The quality appears superior to 615s in every way. The whole thing appears to be machined & stamped metal, even the trunion. I am short on time right now, but will post pictures & more info later tonight.

Firepower R/C

My Feedback: (10)

Here are some pictures for any interested parties out there. You can see the rotation mechanism utilizes a ball & socket with a rod instead of gears. I have seen this exact method used on a full scale Aerocommander's main gear. Very nice. Michael said that this should cut down on the slop that geared rotators can get... we'll see! These gear have links very similar to the Robart 615s, but they are straight AND thicker. Time will tell if they are tougher.

One more thing: it does look like they only can use a 5/32" strut, as that is the size of the hole in the trunnion, and the meat is a little thin to drill it out (I guess you could after a second look). However, this shouldn't really be a problem since you can attach some Robostruts using a small 5/32" length of landing gear wire.

So, I am going to pull out my Aurora and try these buggers out in a bit.

EDIT: 3/16" struts can be used, only care must be taken during drilling to not break the welds on the trunnion. Michael from Wingspan shot me a note saying new trunnions will be sent to me soon, with a beefier weld contact area (must have been someone out there that broke one trying to drill it out). The way I see it, this really isn't a defect, but is more or less a proactive measure. I only wish more manufacturers out there tried this hard to keep their customers happy.

Robart, take note!!! (I still like Robart, by the way... their 615s need to be updated however)

WSRetracts

For anyone that will be using the 3/8" robostruts with either the 5/32" or 3/16" bushings that come with the struts, if they are hammered down enough it will allow for the strut to be slipped over top of the rotating part of the trunnion.  This will provide the most secure method for attaching the strut.  This is what I have done and it works very well. 

Michael

scottrc

Do you have flaps set up with the switch or dial?

aghost

My Feedback: (13)

3 position switch.

Hoghead385

My Feedback: (1)

CG question for those who have flown this model? With the gear retracted and the flight battery behind the tank, my balance point is at 4 3/8". Has anyone experimented with moving the CG aft? The manual states that there is a 3/8" range forward and aft. Really don't want to hang dead weight up front but you do what you have to do! Thanks

aghost

My Feedback: (13)

The CG on mine is slightly ahead of the design point. i have not tried it farther back (or more forward).