Pneumatic connectors for retracts query.

[SiBee]

I’m new to pneumatic retracts as I’ve bought a 10 year old Black Horse warbird.

The removable wings each need connecting to a Down and Up T connector each time I fly and I suspect there’s a slight leak in one of the connectors which isn’t surprising as they’ve been in use for 10 years.They are Easun quick release connectors. Anybody know whether it’s advisable to smear the air lines with some sort of grease to get a better seal ?

Thanks

[Nigel R]

No experience of air retracts, but, I have read that air tool oil is ideal (which makes a lot of sense).

 

Such as:

 

https://www.halfords.com/tools/power-tools-and-accessories/power-tool-accessories/sip-advanced-air-tool-oil-1-litre-117945.html

[SiBee]

Ok thanks that’s great

[Paul De Tourtoulon]

I use silicone spray, also Tamiya or other makes of damper oil for RC cars.

[Jon H]

How big is the leak? If they hold pressure for 15 minutes and still get the gear down i wouldnt worry. I see some guys who want their retracts to hold air for a month. This is rather unrealistic as an expectation! 

[Engine Doctor]

Silicone oil or ait tool oil might help.  The quick connectors usually have  a "o" ring seal and if that has cracked due to age then the only fix is to replace them . Look on ebay they are pretty cheap . You need to measure inside diameter and thickness of wall.

As Jon says if they hold air for 15 to 20 mins then thats plenty long enough for a flight with air up , air down types but if they are air up and spring down theres nothing to worry about as they failsafe to down if air is lost. 

Edited August 8, 2023 by Engine Doctor

[SiBee]

25 minutes ago, Jon - Laser Engines said:

How big is the leak? If they hold pressure for 15 minutes and still get the gear down i wouldnt worry. I see some guys who want their retracts to hold air for a month. This is rather unrealistic as an expectation! 

Hi Jon

 

thanks for the reply. If I carry the Typhoon to the take off point it seems to hold better so it seems to leak more during taxi. The gear goes up and down no problem but if it gets low the right gear collapses during the landing roll. Pumped up to 100psi seems to last for one flight but not two. It’s a great flying model but hasn’t been available for about 10 years so spares are like hen’s teeth.

[SiBee]

28 minutes ago, Engine Doctor said:

Silicone oil or ait tool oil might help.  The quick connectors usually have  a "o" ring seal and if that has cracked due to age then the only fix is to replace them . Look on ebay they are pretty cheap . You need to measure inside diameter and thickness of wall.

As Jon says if they hold air for 15 to 20 mins then thats plenty long enough for a flight with air up , air down types but if they are air up and spring down theres nothing to worry about as they failsafe to down if air is lost. 

I’ve had a look for those Easun quick release connectors but can’t find any except at Alibaba. Are there any suitable alternatives? It’s the T connectors I need

[Engine Doctor]

1 minute ago, SiBee said:

I’ve had a look for those Easun quick release connectors but can’t find any except at Alibaba. Are there any suitable alternatives? It’s the T connectors I need

Sorry cant help . They used to be readily available fro modrl shops but most seem to have gone electric. Try giving Rapid RC a call he keeps load of stuff. Alternstively look on ebay. There are "springair" T pieces an Robart quick connectors on there in "Toys and models" section

[SiBee]

👍

[Ron Gray]

My air retract systems use the Robart type connectors but they are quick release straight connectors for joining the wings. Nexus amongst others sell air system parts.

[Jon H]

11 minutes ago, SiBee said:

Hi Jon

 

thanks for the reply. If I carry the Typhoon to the take off point it seems to hold better so it seems to leak more during taxi. The gear goes up and down no problem but if it gets low the right gear collapses during the landing roll. Pumped up to 100psi seems to last for one flight but not two. It’s a great flying model but hasn’t been available for about 10 years so spares are like hen’s teeth.

 

Always refill retracts before each flight. I refuel first, get everything ready, then gas it up. Start the engine and then off we go. 

 

When i build a new model with air retracts to leak check it i just pump it up, wait 3-4 minutes, retract the gear, wait 10 minutes. This simulates a flight and what i want to know is if the gear come down. If they do, great. I then retract them again to get an idea of how much margin is left. Normally another cycle is fine and i do not check further than that as i dont mess about with the gear in flight.

 

I would also make sure the leak is coming from where you think. Normally the filling valve, spool valve and the retract cylinders themselves can be problematic. As the other have suggested some air tool oil or thicker silicone oil can help with this if the O rings have dried out. 

 

One final thing i can recommend is to stop worrying about the wheels not coming down. Its inevitable that the retracts will fail one day, so my advice is to not worry about it. The model can be belly landed without incident, and even if it picks up minor damage which will prevent it flying that day its not exactly going to be totalled. So dont worry about it. 

 

The reason i recommend you just accept it and not worry is that i have seen so many warbirds crashed because the pilot is so worried about his missing undercarriage/causing damage with a belly landing that he forgets all about the flying part. With their mind not on the job their approaches are terrible and they make a total dogs dinner of the landing smashing up the model in the process. Its something i dont really understand as the gear have failed, there is nothing you can do about it and worrying about the damage of a belly landing makes no sense. Its going to belly land, that damage is already a given, so just accept it and land as well as you can to minimise it. Worrying about it will just make it worse. 

 

 

[SiBee]

Great, thanks for the replies 

[Ron Gray]

I agree with Jon regarding flying the models and not worrying too much if the gear doesn’t come down. My ESM P51 has been belly landed on 3 occasions now and has not suffered any real damage, in fact after the first one I reinforced the cowl and belly intake with carbon tow to help with such landings! 2 of the air failures were due to air tubes having popped off a connector as soon as the gear was retracted. Having fixed that problem I changed my fill procedure and instead of 100lbs pressure I now only put in 70, this gives enough for 4 cycles. The fill valve on the P51 does leak a little bit so pressure will have gone within a couple of hours, but as per Jon, I always top up each time just before I fly. On the other hand my ESM Hurri maintains pressure for months and I put that down to the installation which has all of the air system in the wing so there are no connections to be made when fitting the wing (apart from electrics). I do deviate from the filling procedure for my ESM Tigercat, as that has 3 legs I pump it to 100lbs.

[SiBee]

Ok thanks 👍

[Frank Skilbeck]

You note that if the pressure is low then the right leg would collapse, do the legs not lock down. Many of the systems I have used have mechanical which needs air pressure applied to "unlock"

[Chris Walby]

I agree with Jon and Ron, fill before every flight, only thing to add. Old pipe becomes hard and I have come across some pipe to fittings that leak when flexed. So bench tests ok, but once the engine is running and things are moving about the pressure is faster. Re-plumb it as it won't take long, you can check each component for leaks + get a little silicon oil in part. And its a good job done for the next few years (piece of mind as well).

 

Plan B again...if the retracts don't work then you have already picked a spot of long grass to land in 🙂

 

 

[SiBee]

29 minutes ago, Frank Skilbeck said:

You note that if the pressure is low then the right leg would collapse, do the legs not lock down. Many of the systems I have used have mechanical which needs air pressure applied to "unlock"

When the pressure is low, they both lock down but the right leg can’t maintain the lock once it’s rolling along the grass.

[Jon H]

9 minutes ago, SiBee said:

When the pressure is low, they both lock down but the right leg can’t maintain the lock once it’s rolling along the grass.

 

I would imagine the down locks never engage as they are mechanical in nature and even with very low air pressure they will hold on their own. I would check the operation of the unit and make sure the locking aspect is smooth in its operation. My small Hurricane had an issue where one leg would get jammed up if pressure was a little low. I traced this back to the channels cut in the side frames being just a smidge tight on the crosspin/slide thing. It was tight at the point where the cross bar sat when in the up lock position. It was ok going up as it was moving with full pressure and its own momentum but coming down was sometimes a problem as it had wedged itself.  I took the unit apart and a few swipes with a file had the problem solved. 

 

The problem is slowly returning, but i suspect that is down to one or two 'arrivals' which have just tweaked the whole unit. I will sort it out over the winter as its working ok at the moment, it just takes a few seconds to think about life before deciding to come down. 

[SiBee]

48 minutes ago, Jon - Laser Engines said:

 

I would imagine the down locks never engage as they are mechanical in nature and even with very low air pressure they will hold on their own. I would check the operation of the unit and make sure the locking aspect is smooth in its operation. My small Hurricane had an issue where one leg would get jammed up if pressure was a little low. I traced this back to the channels cut in the side frames being just a smidge tight on the crosspin/slide thing. It was tight at the point where the cross bar sat when in the up lock position. It was ok going up as it was moving with full pressure and its own momentum but coming down was sometimes a problem as it had wedged itself.  I took the unit apart and a few swipes with a file had the problem solved. 

 

The problem is slowly returning, but i suspect that is down to one or two 'arrivals' which have just tweaked the whole unit. I will sort it out over the winter as its working ok at the moment, it just takes a few seconds to think about life before deciding to come down. 

Ok thanks Jon

 

If the left leg is locked up when the wing is removed and the pneumatic connectors are disconnected, it stays up.

If the right leg is up when the air pressure is removed, it just drops down.

[SiBee]

Actually thinking about it, this is what you’d want wouldn’t you. Pressure lost, gear dropping down 🤦‍♂️

[Jon H]

yea that sounds like the locks are not fully engaging for some reason. On all of mine when working on the bench i have to jab at the cross bar thing with a screw driver to level the up/down locks off so i can move the legs and do whatever maintenance i need to do. It takes barely a fart of air pressure to keep the locks in place so i really think your locks are only partially engaging at best. 

[Jon H]

3 minutes ago, SiBee said:

Actually thinking about it, this is what you’d want wouldn’t you. Pressure lost, gear dropping down 🤦‍♂️

 

if you rely just on air pressure to keep them up you can have gear droop when pulling G. This is more pronounced on bigger models with long oleos and heavy 4 and 5 inch wheels. Spring/air retracts used to be very popular with air up and a spring to push them down and engage the down locks. Great idea, but a pain in the butt to store as the legs were stuck out of the wing instead of remaining retracted. 

[SiBee]

Are they easy enough to dismantle and check ?

[Jon H]

Should be a handful of screws to undo and they all come to bits. I stripped a rebuilt a robart unit earlier in about 5 minutes as i wanted to reverse the configuration of the cylinder.