Teflon PTFE

[PeterT]

I just learned its basically the same, like saying Kleenex or Tissue
https://www.nes-ips.com/teflon-vs-ptfe/

I'm working on the induction tubes for my radial. I initially assumed I could use Viton O-rings between the flared tube end & the head as a gasket type air seal. But after a lot of trial & error, concluded that it needs a rectangular washer profile as opposed to a circle section O-ring. Because its an oddball OD/ID/Thickness & I don't have a lot of dimensional latitude, I don't think I'm going to find anything off the shelf. I turned some dummys from scrap nylon & UHMW & they both sealed despite being a harder material. So that was encouraging. Now I'm hoping teflon/ptfe will be about the same or maybe bit less hardness but give me the high temp rating. I could either turn my own from 0.5" solid stick, or possibly make them from stacked 1/16" thick sheets. Or maybe 1mm if its metric.

Its the typical 'need a little bit' issue. I've seen some prospects on Ebay but its either stupid shipping cost or 2 months away if from China. Has anyone seen a (smaller quantity) supplier for this stuff? Or maybe something that is made from this material that I can re-purpose?

 

[Johnwa]

@PeterT how much is a little bit? This piece is 20mm OD.

 

[DPittman]

I'm not quite sure the dimensions you need but I have (somewhere) some flat "bar" Teflon. I'm guessing it might be 1-1.5" wide by 1/8-1/4" thick and I think I might have 8" of it squirelled away. Let me know if that might be helpful....

 

[CalgaryPT]

I just learned its basically the same, like saying Kleenex or Tissue
https://www.nes-ips.com/teflon-vs-ptfe/...

Would acetal work?

 

[PeterT]

Thanks Johnwa & DPittman. John's rod would be enough length but probably wasteful of the OD. I subsequently found a stick of mystery plastic among my 'white pile of plastic' that might be teflon. It has a different feel & more pure white color vs my UHMW & nylon which is more pale color. I have to think back of how & why I acquired it. Something tells me it was related to foam cutting which maybe meant insulation collar over hot wire. If I don't find something useful I may take you up on a trade.

I don't need it urgently, it was more about getting them done & over with. Now that I think about it, stacking a thin sheets like 1mm might be more of a pain. My experience with plastics like these is nothing bonds very well, other than maybe double stick tape, but probably more trouble than its worth.

PT, delrin/acetal is good for only about 120C. Teflon is in the 300-350 C range. I could probably get away with it on the induction side which just sees head temp. But the exhaust pipe will be hotter from the flame passing through & was hoping to make the same gasket washer for both sides of same stuff.

 

[CalgaryPT]

PT, delrin/acetal is good for only about 120C. Teflon is in the 300-350 C range. I could probably get away with it on the induction side which just sees head temp. But the exhaust pipe will be hotter from the flame passing through & was hoping to make the same gasket washer for both sides of same stuff.

Gotcha. I have some acetal if you need it at some point.

 

[RobinHood]

How about PEEK? Good to 343*C. I have a 1” OD stick if you want to try some of it.

I also have 1.5” OD Teflon.

 

[eotrfish]

What are the final part dimensions?
I have the following material that may work...
- .030 Rulon sheet - stack them up and turn diameters
- 25% glass filled PEEK rod
- Virgin teflon tube
- Virgin teflon rod
Have you tried to source crushable V-seals or metal o-rings? I’ve used both to 25,000 psi / 500F

 

[John Conroy]

Peter if You are after any size or style of o-ring try Fluidseal. They have never let me down for any seal or o-ring I needed.

https://www.sealsonline.com/flabed/en/48-o-rings

 

[PeterT]

Thanks for so much interest & generosity. The washers need to be 0.400"OD x 0.275"ID x 0.050" thickness. I was clicking away on Ali when you guys responded & found a suitable stick pretty cheap & reasonable shipping cost/time. But I also found the exact OD/ID range of obscure flexible silicon tubing sizes that I also need to couple the intake tube to the manifold nipple (green shade area), so the planets aligned. Some pics so you can see whats going on.

RobinHood, never heard of PEEK, now my interest is 'peaked' LOL. Again I'd feel bad turning off 90% as waste. But I may have to revisit this material when the time comes. As mentioned I made some testers from nylon, screwed the nut finger tight, blocked the valve holes & (lung) pressure held (although its technically vacuum I need to test). I also tested UHMW to see if the hardness mattered, then back & forth. It sealed again but possibly not quite as good. So not quite sure if its just hit & miss assembly or maybe the first tighten is the best one. My trumpet ends are getting more consistent but they still need a bit of flattening dressing. And these dang head threads are so delicate, initial partial engagement on the nut at the entry angle I have to be super careful about starting it properly & not cross threading. So unfortunately not a crank down thing, just light mini wrench torque.

eotrfish, again thanks. My first preference was something softer durometer like typical O-ring. I tried every combination of size & thickness & hardness in my arsenal but when I tighten it always wants to extrude into the flare a bit. Function of this crazy geometry. I thought about neoprene sheet & making washers but that would mean stamping out a hole & not sure it would take the exhaust temp either. There is no real seal issue on the exhaust side but I figured make a batch from one material & then hopefully set for the engine plus spares. Who knows if this will be the end result until it runs.

Thanks again guys. The journey continues...

 

[CalgaryPT]

Are those pics parts you made?

 

[PeterT]

Yes, shop made by me. The heads about a year ago, the crankcase & manifold before that. Pretty bad when you measure progress by year number, LOL.
Now that the assembly is coming together, working on some intermediary parts like the induction tube you see in pic and the rocker/pushrod assembly on the front side.
My mantra is 'Run in Twenty One' haha

 

[CalgaryPT]

Yes, shop made by me. The heads about a year ago, the crankcase & manifold before that. Pretty bad when you measure progress by year number, LOL.
Now that the assembly is coming together, working on some intermediary parts like the induction tube you see in pic and the rocker/pushrod assembly on the front side.
My mantra is 'Run in Twenty One' haha

Had to ask because that is beautiful work Peter. That's on another level in fact (at least to someone like me who only uses his lathe for facing and turning down shafts or making plastic bushings).

Absolutely beautiful work. I'm really impressed. No way in a million years I could do that. So nice...

 

[YYCHM]

Are those pics parts you made?

https://canadianhobbymetalworkers.com/threads/radial-engine-build.68/

 

[PeterT]

Thanks for the compliment. The project also acts as a natural hair hi-lighter, mine is rapidly turning grey, Haha.

 

[DPittman]

"Pretty bad when you measure progress by year number, LOL"

If I started a thread about unfinished long term projects I betcha I could be king. I have an ultra light project that I started over 14 years ago that was supposed to be (at the time) only a 6 month project. Ha ha. The thing hasn't flown yet. It is now high on the bucket list, but I fear the bucket may fly before the ultralight does.

 

[CalgaryPT]

"Pretty bad when you measure progress by year number, LOL"

If I started a thread about unfinished long term projects I betcha I could be king. I have an ultra light project that I started over 14 years ago that was supposed to be (at the time) only a 6 month project. Ha ha. The thing hasn't flown yet. It is now high on the bucket list, but I fear the bucket may fly before the ultralight does.

Hopefully the laws of physics won't change before it gets airborne. LOL.