Teflon inner Tube Liner or Not ?

[rol243]

guys, i have always used shaft liners without any teflon liner insert, just the correct inside diameter brass tube to suit the flex shaft outside diameter. my question arises from a new zippkits model 21 fe rigger where the motor mount was pre drilled to take the zippkits motor mount and the actual angle of this makes for a reasonable bend in the shaft tube which i used a teflon liner but i feel there is a fare amount of drag in the shaft tube caused by the bend / teflon liner. if there was no liner i am sure there would be alot less shaft drag but unfortunetly i can,t remove the liner as the actual brass shaft would then be to large in internal diameter for the flex shaft to run without flopping etc . i am thinking on having 2 pieces of teflon liner in the shaft tube , front section and rear section not on the tube bend section.

[Prodrvr]

Not a fan of liners. It's a problem waiting to happen. Could you use the next size down of brass tube in the straight parts of the stuffing tube and glue them in?

[rol243]

actually that's a very good idea, I could fit a piece on the motor side and another piece on the strut side leaving a short space at the bend. as mentioned I don,t like this drag atall. thanks Prodrvr.

[NativePaul]

No wonder it is draggy, it comes with a 1/4" tube which is suitable for running the 3/16 cable it comes with without a liner. If you want to run a liner you will either need a bigger 9/32" stuffing tube, or run a smaller .150 flex which is the right size for a 1/4" with liner.

On a lesser note, I am not a fan of S bends in stuffing tubes, and the driveline seems obscenely long for a flex, I swapped my JAE.21 out to a wire drive (that really benefits from a shallow bend) when I went to a front motor layout with it.

[Prodrvr]

actually that's a very good idea, I could fit a piece on the motor side and another piece on the strut side leaving a short space at the bend. as mentioned I don,t like this drag atall. thanks Prodrvr.

Hope it helps.

[rol243]

I removed the teflon liner and inserted 2 x short lengths of brass tube next size diameter down from the existing brass tube in tub / hull. the lengths were approx 3 inches at the strut end and approx 2 inches at the motor collet end, left about 1/4 inch sticking out at the ends so i could sweat solder the sleaves so they wouldn,t turn or move. certainly no drag now, that liner was just no go and i am sure the motor will rev alot easier now without having this extra drag to worry about. i can understand the teflon liners would work well with long shaft tubes that have a gradual bend but definetly not for this particular boat set up.

[MarkF]

I have been racing rc boats for over 25 years, have been national champion and broke a dozen saw records in that time. Every one of my boats run a teflon liner with the exception of my big gas boat conversions or maybe a hot saw boat. And some of my boats the motor is way back with a very sharp bend. You can rub metal on metal or metal on teflon. If you got a tight spot, it will wear in just like it will when it's rubbing against metal. I will also say there is plastic liner which is crap and teflon liner which is not. There is no difference in "Speed" whatever way you go but there is an annoying metal on metal sound I hate when you don't use a liner. But that's just me. You also have a softer bend with the liner because you are using a bigger brass tube. If your going to run a spec motor in your boat. Run the liner and the 150 cable. That is what I run in all my spec race boats. Taking the liner out and putting smaller brass tubes where you can will gain you nothing in performance. Well that's my 2c on the subject, but what do I know.

Mark

[RaceMechaniX]

One tip, try sanding the cable down. This will help reduce friction whether you are running teflon or brass. I put a piece of silicone fuel tubing on the motor side of the cable long enough to cover the entire section of cable that goes into the collet. Chuck up the silicone end in a hand drill and either use a small belt sander or carefully hold a piece of sand paper in your hand. Start with a 220 grit paper to knock off the high spots, then finish with a fine 600 grit paper with some oil. The goal is to knock knock the high ridges and then polish the outer diameter. You do not need to take off a lot of diameter. Some there betweeen .010-.015" in diameter is usually enough.

This was a 46W difference on a p-spec boat that I could measure through logging with otherwise identical setups.

Just remember to not sand down the collet section and to clean the cable throughly with brake cleaner to remove any left over grit.

Tyler

[Tamelesstgr]

This was a 46W difference on a p-spec boat that I could measure through logging with otherwise identical setups.

Tyler

No that's my kind of data collection

[rol243]

thats great advice guys, thanks.

[Shooter]

Good tip regarding sanding. I run tef liners in all my boats. It's very true that it is "another part in the system that can go wrong". However, it works very well if done right. It's much cleaner (no goopy mess of high viscosity grease necessary) and it is also more forgiving if you don't lube. You can run very light oil and the result is a very clean, low friction set up.

The thrust is transfered thru the flexshaft and its going to rub somewhere on the sidewall as Mark said. I prefer it to be rubbing on Teflon.

[grsboats]

Well different points of views but in my case my gas nitro and fe riggers have no liners ,i dont use grease (only oil) and if my memory doesnt fail my last failure was when I started running riggers in the 80's (1984) and forgot to leave the gap between the drive dog and strut.I think we have here a valuable tips. Gill

[MarkF]

I think it's a giving that not nobody run liners in nitro or gas boats. I draw the line at 6s and 180 size cable. Over 6s and 1/4 cable gets no liner. Liners are trouble on 8 and 10s boats.

Mark

[rol243]

Mark, why are the liners trouble with the larger lipo powered boats ?

[Prodrvr]

I don't use liners, but I'll ask along with Mark...what's up with no liner over 6s compared to lesser voltages?