Lets talk air clinders for gear doors
 

Okay I have been trying to finish up my SM F-14 and this thing has had me beating my head on the wall for awhile now, but its getting there. Last little thing to sort now is the leaking air cylinders, I tested all them prior to the build and most required some glue to the threads of the barbs to stop leaks, but now im getting blow by from the internal O-rings(already tried the bvm O-ring stuff". So im pondering ripping out the SM cylinders and replacing them with something else.

It would be nice to get some air cylinders that hold up and just require the occasional O-ring replacement so any ideas on other brands that will keep me from taking a bat to this project :p?

I was considering the dreamworks valves since they dont slam open/close but at a price of 40ish per and I will need 10 that can get costly. Thanks

lol its funny you started this thread. So I was working on mine testing out the speed brakes and all of a sudden one of the air cylinders blew the back cap off :( I don't know why it would have done that so I put the back cap on and put a little hysol around the joint where the cap meets the tube. I hope it holds up. I am right there with you on the price for the other ones. I just cant see paying that much just for a little air cylinder.

The only thing that I can think of is to use some Airline Restrictors but I'm not sure you tried them. I would try to put them on the down line.

Hey Joe, yeah the force isn't the problem I'm having its just bad quality. If you use jettronic valves you can put a throttle on your gear doors like I did to prevent the slamming. The problem I'm having is the air is passing from the pressure side of the inner o ring to the other and then out the valve.

O Wow, That's crazy. Here is a link: http://www.rc-warbirds.com/product_i...oducts_id/1057
Not sure if you have been to this website. I ordered my Airpower air valve from them and it was good. The only issue that I have found with this company is that they use the Singapore post and it takes for ever. I think they use other shipping methods too.

I had problems with Ultra Precision cylinders for gear doors so I used Robart.
They had longer stroke than the UP so ended up restricting their travel with
plastic tubing on their shafts.

http://robart.com/collections/air-sy...-air-cylinders

John.

Cylinders = BVM. You will have all your problems solved.
Valves= Ultra precision ( old school that will not let you down)
or Jet- tronic , Xicoy.
Have used all the above with no problems.

I have tested cylinders that held fine on the bench but started leaking once installed. Some of these cheapies just need a little side load and they start spitting air. Todds or UP would be my choice.
Vin...

Ultra Precision or Robart. Never had either leak.

Kinda like how beefy the Robart look, how is the weight compared to others?

I don't know Keith, you keep finding more things wrong with the F-14 gear...... :(

At least you are providing me with some substantial information on issues you've had with your airplane. I sent an email to John at Skymaster about mine and he said it had been forwarded to Likai but no response from him and it's been three weeks now.

Zeeb, it would be nice to depend on the company to listen and make the needed changes but I lost that battle long ago so like most I have come to just fix things myself. Its costly but tends to keep my blood pressure down. I like SM jets but every issue I seem to get the "your the first to have this problem" and they never change anything unless someone crashes due to a design flaw. John does try his best to get things done, if I needed new cylinders he would send me more but they would end like this. Anton sees every build thread on here and all the comments from folks but it's very rare to see a change from it.

jet model products cylinders work well

yeah I love there stuff, just not to pay that when the Robarts and UP are a bit cheaper and just as good. I really like the mechanical valves I have one in my rebel pro, true hi flow.

Keith, a few years ago I had that blow by issue on my SM F-18F mains. I tried a lot of different things but the ultimate fix was to use a different O-ring. The factory rings would cold form and.flatten while at the end of the stroke while sitting with a side load.

The rings I found were either silicone or viton (McMaster Carr). They were a little softer, lower durometer and the compound was more resilient and didn't cold form. They were also a little tighter fit in the cylinder. It was an instant fix. Still airtight after 2 Years.

I don't know if you can take those little cylinders apart but just a thought.

SteveK

You can take them apart, I guess I could try that.

Robart cylinders use 2 O rings on the piston and it makes them almost perfect. The piston is wider than the others so side loads won't displace it enough to leak. The problem is they don't make that many sizes.


Bob Neal

Hi Keith,
If you can get them apart, fold over some plumbers' Teflon tape into a 4 ply strip and put it under the o-ring, by removing the o-ring from the piston, putting the 4 ply into the groove and re-fitting the o-ring. Sounds much harder than it really is. Learned this one from Duke in Hawaii on my F-35A when all the cylinders began to blow by in the heat.
Len

If I cant get larger O rings I may give it a try some of the cylinders are tiny and this would be a chore

From what I could ascertain the Asian 0-rings at least in my case were the right size but their composition was so bad that they'd just roll up on themselves and create leaks. In my case it was that the manufacturer had never considered a warm climate in the design of the gear and door cylinders. Anyway I must agree doing this to a 1/4 or 5/16 door cylinder would be very nit-picky. Good luck!
Len

I think the o rings are just to soft and crap material.

I cannot understand why you are losing sleep over this. Just replace them all with UP cylinders. That is what I do, and the UP cylinders I have had never leak and even can stand the piston shaft being bent and straightened.

John

Whatever happened to the electric actuators that were once so popular? I thought everyone would switch to those eventually. If I recall they had programmable speed and end points, making them super easy to setup.

Are those no longer available?

Ditto on SM.....once they have a new toy in town all eyes are on that one (F-16 1/5), plus they have to sell that puppy before BVM comes out with theirs.

David

+1 . UP and forget it

Yes ditto on SM. From what I have seen, just another Chinese ARF. Of course I never touched one of those flyeagled so I have not seen rock bottom I guess

John, that is my intent and the reason I inquired about the best replacements. I took some measurements last night and I will say the SM cylinder lengths are 29mm x2 22 mm x6 and 15.5mm x2 I am placing the order for 2x 5/16 x 1 5/16, 2x 5/16 x 3/4 and 6 5/16 x 1in I think these are the closest to the stock as I can get. UP-6 is the plan since they have all the sizes I need.