Copper Tubing is there something better?

[barnstorm2]

My redive is lubracated via 1/8" copper tubing with compressing fittings. After taking my redrive off and on a few times lately it must have been stressed and or vibrations are affecting it. When I landed last night I found one fitting leaking oil (again) so I grabbed a wrench and teflon tape to fix the leak. When I started to turn the nut the copper tube snapped off in my hand.

This does not build confidence.

At Mentone someone (sorry so much going on I forgot whom) recommened an alternitve to the plain copper tubing. He mentioned a product that had a protective outer sleeve.

Is there something better that I can trust to replace the copper with?

[scottessex]

to get you back up and flying, go to an auto parts store and get an oil pressure gauge plumbing kit, they have both nylon and copper tubing. You could go with the plastic, it won't work harden, but you may have to replace it every season.

[Dean_Dolph]

I agree with Scott on the nylon. It is flexible enough that it should absorb the vibrations and won't work harden like the copper. However, like Scott has suggested it may need replacing once in a while because it will harden from the environment.

An alternative, although more expensive, is to have hydraulic hose made up using teflon hose with a stainless steel outer braid. The hydraulic hose people make these for the chemical industry all the time so it shouldn't be a problem getting one. This type of hose and size should be flexible enough and they can be removed/replaced numerous times with out worry of damage. The will require the proper fittings. Trust me, there won't be any more leaks or failure!

[jawbrey]

Steelbraided Line A Little Expensive Worth Every Bit

James

[Ron Marlett]

Definitly ditch that copper... As mentioned vibrations will "Work harden" the copper and make it brittle. When I was young(and stupid) and didn't know about this, I made a replacement fuel line on a old truck out of copper that looked really cool. I was very proud of how it came out but it eventually fractured and I was dam lucky that it only stranded me in the middle of nowhere for a while and that it didn't catch fire. Just about any racing parts suplier such as WWW.jegs.com or www.summitracing.com can supply you with oil rated teflon hose with a braided stainless outer sheath and the proper AN aluminum fittings to do up a neat professional looking job on that oil line. They sell the hose by the foot and you can get straight and elbowed fittings(from 0-180 degrees) to fit just about anything metric or standard. They are real easy to make up yourself in any length and not terribly expensive. I have been running one on my trucks turbocharger oil supply line for several years now without a problem.

Ron

[Vance]

Be bery carefull when handling braded stainless. It tends to be very hard on your skin and the abraisions are very painfull. I always assemble the hoses with an outer layer of heat shrink tubing. It doesn't look as cool, but it is much nicer to work on. Keep the bradded stainless away from electrical wireing as it will very quickly abrade the insulation and it does conduct electricty. good luck, Vance

[Jerseywing]

Depending on the routing you can also relieve stress in a line by putting a "pigtail" in the line. Just a loop but don't kink or stress it when you bend it. This will allow for vibration and thermal expansion. Check that it won't interfere with anything else first. From the looks of it you can probably get the proper length teflon hose and a couple of 45 Deg fittings and almost have a straight shot end to end. Copper doesn't play well under vibration. And like Vance said watch for the hairs on the braided lines, they're real painful under the fingernails

[scottessex]

Just remember, stainless is harder that aluminum. I have seen braided oil lines cut into motorcycle cases like a saw blade.
Another solution, would be to get some harley aftermarket brake fittings and stainless plastic coated brakeline from the local bike shop, any competant shop can make up the lines/hoses to any length you want.

[Vance]

Given the realitivly low presure, probably you could use niples and power steering hose that is avalible from any good auto parts store. I like to use safty wire to hold the hose on the nipples, but hose clamps will work fine too. Power steering hose has less tendency to kink than rubber hose or even gas line. Vibration proof, easy and cheep. Thank You, Vance

[barnstorm2]

Thanks guys!

I have been looking up the teflon hose but i hate the online descriptions. I would like to find a place where I can see it in person, so I am working on that. For the short term (next couple of weeks) I am going to use the pig tail method. This will give me time to examine all of the suggestions in your posts.

I am a little concerned about the braded line. How could you see a stress developing? If the underlying hose broke the brade would not help keep it in so it really just helps protect the tubing, possibly at the expense of cutting what ever was rubbing against it.

I do not want to tap and die out the holes in my redrive for a new kind of hose, so if possible I want to go with something that will fit the existing threads.

[Vance]

Tim, from the picture it looks like it is 1/8 pipe into the case with an adapter for a compresion fitting. 1/8 pipe is very common and gives you a lot of options. 1/8 pipe is common for niples. In my experance with braded stainless it is very vibration proof. I have used it a lot on the front brakes on motorcycles, where both vibration and bending are quite severe and failure can be a safty problem. Thank you, Vance

[barnstorm2]

Vance,

Yes, your eye is spot on. 1/8" copper tubing with compression fittings. I like the nipple idea as then I could easily change the hose and inspect it. Do you need a special cutter/bender for the stainless tubing? Stainless would need a compression fitting also?

I just make some copper pigtails as per the suggestion above. Kinda cool looking. I wonder if it will make my redrive look like a Mad-Scientist's lab or a Kentucky moonshine still? :)

[scottessex]

Motorcycle brake line (harley type) sounds like your best bet. The fittings are 1/8 pipe on one end and flare on the other. And most of the stainless line is teflon lined, and the bonus is the outer covering is clear plastic so it won't abrade against anything. I had some lines made up and it cost around $40. did it while I waited.

[Vance]

Tim, Hard stainless steel tubing work hardens with vibration. If you are going to use it putting a loop in it like a still is a good thing. I would recomend against it. Braded stainless is very easy to assemble from any number of manufactures without any special tools. The nipples that I spoke of are generaly brass with 1/8 pipe thread which is what I beleive is in your case. You can buy them at most auto parts stores or hardware stores. Remember you are dealing with fairly low presure, relitivly low tempeture and a fairly benign liquid. Keep it simple. Thank you, Vance

[Dean_Dolph]

Tim, I used SS braid covered Teflon hose in an R&D environment for over 25 years and found them extremely reliable. We used them to transfer various hazardous chemicals including pyrophoric ones like sec-butyllithium. We wouldn't have used them if we couldn't have relied on them not to leak or fail.

The outer braid strands will break if subjected to a lot of bending and severe flexing but I've never seen this happen from pure vibration. Like has already been mentioned, a broken strand will get your attention in a hurry! We would use cotton gloves to run down the braid to see if and how many strands were broken. The gloves would catch on the strands. I can assure you that we abused these hoses much worse than you will on your gyro.

The fittings used will have pipe threads on one end with flare on the other. The flare is different than what you are used to making with a copper tube so requires that the hose be made up with matching female swivel fittings.

You can have hose made up with a male fitting with pipe threads permanently fixed on one end and a female swivel fitting on the other. However this requires turning the whole hose to screw it in. I would rather use two female swivel fittings and two pipe thread (NPT) X flare fittings.

[automan1223]

I want to go with metal line, steel brake line 3/16" with flared ends/threaded fittings is the best. Maybe. Right now I am using weather head rubber 1/4" oil rated heavy duty hose on 1/4" barbs with pipe ends going to where I have to oil. .
It is very tough stuff. It is clamped with aba marine non marking hose clamps.

The copper under pressure leaves me a bit nervous, and as you have found out compression fittings can only be used once without leakage, then you have to overtorque them to get them to seal and they break or are overstressed. USE TEFLON TAPE SPARINGLY. I use thread sealant on clean prepped with special spray primer on the threads, so far no leaks.

Jonathan

[Dean_Dolph]

....The copper under pressure leaves me a bit nervous, and as you have found out compression fittings can only be used once without leakage, then you have to over torque them to get them to seal and they break or are overstressed. USE TEFLON TAPE SPARINGLY. I use thread sealant on clean prepped with special spray primer on the threads, so far no leaks.

JonathanJonathan, you are right about he use of Teflon tape. It is great on pipe threads, up to a point, (I prefer the Teflon thread sealant) but it should NEVER be used on the threads of compression or flare fittings of any kind.

Manufacturers sales reps cringe every time they hear about using Teflon in that application. While it doesn't particularly cause a problem with the threads, there is the very real possibility of the tape getting down on the flare and then a leak is very possible. If there aren't any nicks or scratches in the male/female flare surfaces then there isn't any need for additional sealing material. If the surfaces do have a defect then they shouldn't be used anyway.

Actually there isn't any reason that a compression fitting cannot be used more than once. However, copper fittings/tubing of any type are subject to cracking from external stress so the more they are messed with the higher the chances. But again, if the compression fitting mating surfaces are clean and free of defects then there is no reason that they won't seal. It is the tubing that is the passing thru the fittings that is the weak point. Adequate tubing support to handle the vibration in our machines will go a long way in preventing tubing cracks.

Compression fittings have a recommended tightening procedure that I can't find at the moment but as I recall, the initial tightening calls for 3/4 of a turn after it has been 'snugged up'. Then any remake of the joint calls for a 1/4 turn. If the mating surfaces are clean and free of defects then that is all that is needed for a leak free joint. If it leaks then over torqueing is begging for more and bigger problems. Been there, done that! It gets real exciting when a pyrophoric material leaks!