stainless tubing intake manifold

[petertha]

I'm wondering out loud if it's feasible to make an intake manifold from more or less stock sections of tubing, kind of like this sketch. I'm hoping to avoid some funky bending from a single piece of tubing - filling with special bending alloys, heat conditioning the tubing, compound 3D angles using jigs etc. While I certainly appreciate the skill involved, I'm wondering if it can be reduced to more... uhhm... 'amateur' steps? ;D

In this example I assume 0.25" OD stainless tubing. It comes in various wall thickness increments ranging from 0.020" to 0.083". (I was figgering 0.035"). They offer stainless 304 & 316.
http://www.onlinemetals.com/merchant.cfm?id=312&step=2&top_cat=1

The only real bend would be a basic hoop, in this example 0.75" radius. I would just cut ~60 deg chunks from that. I would have a flange piece from flat stock on either end bolted in position. My hope would be to dry assemble the pieces so they joinded up flange-to-flange & then silver solder the joints to make one piece. (The real engine looks a lot like that anyway).

- could tubing like this be rolled to a hoop diameter this tight without splitting or badly oval-ing in the jig? Any links that help with design criteria in this regard?
- could one 'stretch' (swage - is that the right word?) an end so it would kind of interlock to the stock OD of the adjoining tube? Im guessing a butt joint would be a bad idea.
- any recommendation on which SS alloy?

 

[Ed T]

Any particular reason you want to use stainless other than it's difficult? I don't think you'll have much luck swaging the size tubing you're thinking about w/o so special tools and even then I think it would be tough. Have you considered using automotive brake line or fuel line? It's cheap, available and designed to be bent. You might be able to do the whole thing from one piece and a 3' section is only a few bucks. Lots of room for trial and error. If I see what you are trying to do, I would bend a 180 degree hoop, as you said, and then capture one of the legs (clamp between wood blocks) and see if you can twist the other leg 90 degrees in the other plane. Most/all of the bending will be in the top of the hoop. Regardless of what tubing you end up with, if you have to join it I would put a small internal sleeve at the joint made from, perhaps, hobby shop brass tubing and then silver solder the whole thing together. Stronger and easier than butt joints. Yes, it might interrupt the smooth flow in the manifold, but that is usually not a huge issue for these types of engine. One piece would be better of course. Good luck!

 

[petertha]

Ya see, thats why this is such a great website! Brake line tubing never occurred to me. Now armed with that info & a bit of web searching, I see its available in 5/16" OD too which is maybe what I was moreso wanting over 1/4" in the first place. At least the availability gives me options. I also found lots of video's demonstrating (tools) showing easy it bends & flares.

http://www.plews-edelmann.com/standard-steel-lines/?brochure=1878&location_id=2517

I didnt have a partucular reason for SS other than having seen it used before (and as mentioned, some of the special skills involved). I'm all for simple. But what I failed to mention was considering the the same technique on the exhaust side. Im guessing what makes brake tubing bendable is something like copper alloy? Would you think it could be similarly joined with silver solder & withstand typical exhaust temp?

I found this one material spec
http://www.brakequip.com/pdf/ezibend_tube_booklet.pdf


Some of the reading on SS tubing that had me looking for alternative ideas
http://homepage2.nifty.com/modelicengine/h9111101.htm
http://homepage2.nifty.com/modelicengine/k070402.htm

 

[ChooChooMike]

http://homepage2.nifty.com/modelicengine/

WOW !! That Paz guy sure is an artist !! Great tutorial on his making those tubes/manifold

 

[sunworksco]

Stainless steel and copper tubing can be bent easily if you first inject hot liquid tar into the tubing and allow to cool. Then heat the tubing after bending and clean out the tar. Wind instruments are manufactured by this method.

 

[ghart3]

Could that be rosin and not tar that is used?

 

[mu38&Bg#]

Been following Paz's site for years. There's a lot of detail and photos on the site.

Greg

 

[Maryak]

Could that be rosin and not tar that is used?

Interesting..................I was taught to use resin for bending copper and brass, sand for ferrous and I think there was a link here, where there was a video of making brass wind instruments using ice in the bending process. This would leave a nice clean interior without any residue to distort the airflow/sound.

Best Regards
Bob

 

[Ed T]

Any brake line that I have ever seen in ordinary situations (your car for example) is steel with various platings and coatings to keep it from rusting. Ordinary metal fuel line is similar but with thinner walls since it doesn't see much pressure and is available in larger OD's than brake line. We're talking the kind of stuff you can get at your local parts store or wrecking yard. The copper-nickel stuff you referenced is "special" and, I'll bet, REALLY expensive given the going rate for the two metals involved. Another possibility might be the dead soft, chrome plated, copper lines you often find connecting your sink faucet to the water lines. These are also designed to be bent which is a leg up and they are SHINY which is important too. On the down side, you cannot solder to the chrome plating so it must be removed from the areas you want to solder. May be a bit big for your needs.