6 replies to this topic

[Chris Wilson]

Does anyone have information on slip joints used in the days of F1 1.5 litre turbo engines, as applied to tubular exhaust manifold design? I am wanting to make or commission an Inconel manifold for a straight six engine, and need to address expansion and avoid cracking in endurance applications. I believe a gas tight seal, with mechanical expansion properties can be achieved with slip joints, as well as convoluted bellows? Thanks.

[cheapracer]

Originally posted by Chris Wilson
Does anyone have information on slip joints used in the days of F1 1.5 litre turbo engines, as applied to tubular exhaust manifold design? I am wanting to make or commission an Inconel manifold for a straight six engine, and need to address expansion and avoid cracking in endurance applications. I believe a gas tight seal, with mechanical expansion properties can be achieved with slip joints, as well as convoluted bellows? Thanks.

I'm not a metallurgist and even though exhaust pipe is like a big hollowed bolt which I know nothing about I'll have a go.

All the rally cars I have built for myself and others over the years and people before and after me have had the exhaust solidly bolted to the floor. Because the engine moves around of course, its neccessary to have the exhaust connected to the extractors or header pipe with a slip joint to stop cracking. I usually slip about 3-4 inches in (no jokes please) and the most I pay attention to is grinding the internal weld joint smooth. The slip can be quite loose and suffer no real noticable leakage.

[dosco]

Originally posted by Chris Wilson
Does anyone have information on slip joints used in the days of F1 1.5 litre turbo engines, as applied to tubular exhaust manifold design? I am wanting to make or commission an Inconel manifold for a straight six engine, and need to address expansion and avoid cracking in endurance applications. I believe a gas tight seal, with mechanical expansion properties can be achieved with slip joints, as well as convoluted bellows? Thanks.

Yes, a convoluted bellows will work, however I'm not sure what the race folks used "back in the day."

I used to work for a company that made these types of products for aerospace applications (to take up thermal expansion in an aircraft pneumatic system).

There are some other companies that use piston-ring arrangements - Cook Airtomic, for example.

[Chris Wilson]

Thanks, yes, I use single walled slip joints on any naturally aspirated tubular manifolds I make / have made, and they work fine, but here I am talking of a manifold with 2 bar internal pressure at maybe 900C, so some serious consideration must presumably have been given to leakage limitation? I am thinking they must have used double walled slip joints?

[dosco]

Originally posted by Chris Wilson
Thanks, yes, I use single walled slip joints on any naturally aspirated tubular manifolds I make / have made, and they work fine, but here I am talking of a manifold with 2 bar internal pressure at maybe 900C, so some serious consideration must presumably have been given to leakage limitation? I am thinking they must have used double walled slip joints?

I understand the design considerations.

Not sure about the Cook Airtomic products - they were one of our competitors.

The products made by my former employer would no doubt fit the bill, as they ranged from parts for the main engine bleed, wing anti-ice, and fuselage A/C and pressurization. Temps ranged from 1100 deg F to 200 deg F, and pressures (IIRC) up to 800 psi.

Yes, there were leakage limitations, and therefore were multiple designs for a variety of applications. My thought for you is something like a double-walled stainless or inconel bellows with a braided stainless "sleeve" on the exterior. It's cheap (relatively speaking) and effective.

I would recommend the following websites:

http://www.airtomic.com/index-1.htm (site is light on product info, but gets you part of the way there)

http://www.aerospace...dair/index.html (also kind of light on detail)

http://www.thomasnet...20180600-1.html (a few names here ring a bell, suggest you poke around...)

[cheapracer]

Originally posted by Chris Wilson
Thanks, yes, I use single walled slip joints on any naturally aspirated tubular manifolds I make / have made, and they work fine, but here I am talking of a manifold with 2 bar internal pressure at maybe 900C, so some serious consideration must presumably have been given to leakage limitation? I am thinking they must have used double walled slip joints?

Chris the Honda rs250r motorcycle use whats called a labirynth seal between the paired cyls. I have made them in the past because Honda sell you the whole crank only at great expense. Google for ideas about them but a simple explanation is that of a very course threaded bolt and nut even though not tightened the flow path is so long and hampered that fluids and gasses cant pass. Maybe an idea for you that will give rotational slip but little lateral slip.

[Almag]

Typically bellows or flex sections are not used on automotive exhaust manifolds (though commonly found on the exhaust itself). The only production example that comes to mind is Porsche 944 turbo, which had a bellows on the #4 runner only.

A double slip collector will do you well. These are readily available too:

Reid Washbon double slip collectors (Reid have Inconel collectors available off the shelf)

Burns Stainless double slip collectors (not listed in Inco but Burns will usually do items in the material of your choice)