Equal Length Tubing Programming

[LastCat]

Hey,

 

To start, I'm building a turbo exhaust for a friend, and I am trying to find a function that would work for MC9. This type of exhuast I am building will have equal length single tubing for a 6 cylinder engine.

 

Is there a way to create a line from one anchor point (center of exhaust port from each cylinder) to the anchor point on the turbo exhaust flange. I need to find a way to create each line the same length and start at different points, but all end at the same place, the turbo. I was trying manual spline, but need a way to control length.

 

thanks in advance

LastCat

[Scott Bond]

Hi Lastcat

Could you make a Soild of each tube?

Cutr and fit them,and cut to lenght?

Then analyze the volume of each tube.

[BernieT]

I'm just thinking out loud here, but this might work.

 

Create 6 splines 'Manual', starting at one exhaust port and ending at the turbo. Each spline would be generated by clicking 5 or 6 points along the way to the turbo. Might want to put each spline on a serarate level and/or different color.

Now you can 'Modify - Ctl pts nbs' pick and drag control pts to modify the shape and length of each spline until you get what you want. HTH

[LastCat]

Thanks Scott, Bernie,

 

Give that a try. I like the 5 Point spline idea, that way I could check lengths, and adjust certain points to create equal lengths.

 

Any other ideas, would be appreciated.

 

Thanks

LastCat

[Chris Rizzo]

I also am in the midst of building a turbo exhaust/header, but it's for a four cylinder bike, and it is totally symetrical...lucky for me. (Also lucky for me that I'll probably be riding the bike....7.8sec 1/4 mi.)!

 

I was thinking of how I could use Mastercam to aid in the coping/fitting of tubing. Maybe making patterns and the like. I don't have a whole lot of experience with 3d stuff, and was thinking that solids might make sense.

 

Alternately, tubing manufacturers must have some type of trick software for fabricating complex forms...anybody have any knowledge/experience with Mastercam or other systems in tube fabricating?

[LastCat]

Hi cmr

 

Good luck on your project. Unfortunately, inside this BMW car there isn't much room for exh manifold, plus the turbo exh flange is offset to the head, and not much side clearance, a tight fit, but very doable.

 

I know there are CNC Tubing benders, I wonder what they are using for software, if any?

 

Cheers

LastCat

[Craig Madsen from CM3D]

I remember reading that it is not necessary for the the tubes to be equal length so much as to know or calculate the speed of the exhaust gases at different rpm's.

 

If the exhaust pulses are timed properly, then there will be a low pressure (read: almost vacuum) at the valve to assist in accelerating the gases out of the cylinder. You would need to the volume and speed, giving you a diameter for the tubing, for a given flow at a specific rpm to come up with a length. This would then be modified by the bend radius' (gases flow faster around the inside of the radius than the outside due to a low pressure zone).

 

I think you would have to have access to a good dyno to see the result of any change to tubing size, radius of bends, length of tube, etc. etc. etc.

 

I the end, with a turbo, I don't think you will be as concerned with length as you will with resonance and 'smoothness' of flow.

 

It may be faster in the long run to find which companies have the best results with headers for your application just purchase a set.

[Jack Mitchell]

LastCat,

 

quote:

---

I know there are CNC Tubing benders, I wonder what they are using for software, if any?

---

Addison, Eagle, etc! Are tube bender manufactures. There is proprietary software on all Cnc benders. The software allows for rotational, length, angularity, linear tangency, etc! User friendly? = sometimes but mostly yes, reality? = a tough haul to fine tune to a desired result.

 

Consideration of tube OD, ID and material type and even coatings all come into play for any automated bending operation. Personally, these are the least of your worries for bend analysis.

 

Clamp dies, pressure dies, bend dies, inserts, mandrel balls, linkages, and lastly wiper dies all play a crucial part in a tube bending procedure. (Competent set-up men are a pipe-dream at best) .

 

Not meaning to rant but this is not a realistic expectation for a prototype or one-off situation – yes it can be done and yet nobody would realistically attack it for this purpose - including myself.

 

As Craig has alluded to, I would suggest buying it off the shelf and porting to smooth the transition of resistance (it’s the biggy when it comes to flow control).

 

I might find a picture of a CBX1000 head that I did ten years ago for a professional racing bike.

 

 

Regards, Jack

[LastCat]

Thanks Craig, Jack,

 

Check this pic:

 

 

Its from a 1985 535i BMW with the M30 engine, 3.5 liter straight 6cyl. The guy had the header made, and mounted the turbo above the head, verses below which I need to create the same.

 

He dynoed the car a month ago, and produced 520 hp at the crank and 540 ftlb of torque. Very impressive.

 

At this point, it might seem to be simple to do a trial and error exhaust manifold, as long as the lengths are close and it fits. 304 SS is my choice of material. I was hoping to lay the design out on MC9, and then start fabbing the header from there.

 

LastCat

 

[ 06-08-2003, 08:18 PM: Message edited by: LastCat ]

[Jack Mitchell]

Lastcat,

 

Nice picture - this would be reality in stainless tomorrow if you came to Cambridge, but alas you are in Seattle.

 

The welds look divine and the bends look relatively simple. I would hazard a guess between 2K and 4K for this work of art.

 

Try doing this method:

 

Go to your muffler dealer and scope the various manufacturers, models, sizes, and bends. Choose the diameter and the different parts that capture all of the components.

 

Most exhaust systems today are manufactured in stainless so I don't believe this will present a problem.

The parts could get a little expensive but who ever said that 520 horse comes cheap. The magic here is finding a person that can weld with the passion of artistic expression.

 

I will cut you a deal of a lifetime as follows:

 

Come to Cambridge and walk out of the candy store with all we can carry in a backpak - multiple trips to the candy store as well.

It will cost you the time and dedication to do the same for the 560 Mercedes in my garage.

 

Bye the way - the hands are too pretty and the nails are a little long for a machinist, perhaps somebody else is holding the header?

 

 

Regards, Jack

 

[ 06-08-2003, 09:20 PM: Message edited by: Jack Mitchell ]

[LastCat]

quote:

---

Bye the way - the hands are too pretty and the nails are a little long for a machinist, perhaps somebody else is holding the header?

---

LOL..thats funny Jack.

 

Ya, thats the owner of the car, and the picture was taken at the guys garage that did the welding. But the owner himself is a good wrench too.

 

I can get 2 1/2 dia 304SS tubing in simple 90 and 45 bends, smooth mandrel bends, they aren't that spendy, probably about $125 just for 4 or 6 pieces. Theres a few websites out there, and some Muffler shops have excess pieces laying around, that they sell for cheapo.

 

I have a 120 volt welder that will work fine with stainless. Hopefully in a short time, I'll have the header welded up. 560sec? Those are nice looking Benz's.

 

Weld you a exh header,,hmmm..anything is possible.

 

LastCat

 

[ 06-08-2003, 10:49 PM: Message edited by: LastCat ]

[Scott Bond]

Wow! You guys are Smart.

Jack - My dad was a Tubebender in the 60's craftsmen were respected then, your paragraph was nostalgic for me.

quote:

---

Clamp dies, pressure dies, bend dies, inserts, mandrel balls, linkages, and lastly wiper dies all play a crucial part in a tube bending procedure. (Competent set-up men are a pipe-dream at best) .

---

These are the names my family uses for names on the same tooling you described...Clamp blocks,Follow blocks,Bend blocks,Snake Mandrels,Rotation Fixtures,,Wiper dies.

Here's a few more things a bender may need to stretch the outside ,and shrink the inside with no scratches, stretch marks, or wrinkles. Some Bear grease, ,Several pair of "Vise Grips", serrabend(SP),and maybe some talcum powder.

 

P.S. Nice call on the pretty hands.

 

[ 06-09-2003, 01:43 AM: Message edited by: Scott Bond ]

[chris m]

I know that this isn't the answer that you're looking for, but:

 

I've seen where a guy cut 4 lengths of steel welding wire (like 1/8") to the same length amd tacked them to a plate that resembled the header flange and bolted it up to the cylinder head. He then proceeded to bend them around until he ended up where he wanted to be and tacked them to a plate mimicing (sp?) the header collector. Once this was done he had a template to work from for the real thing.

 

Lot of work, but what can you do?

 

C

[Andris Skulte]

Unless you're going for the final few percent, don't worry about getting identical lengths. The backpressure due to turbos will generally be between 1 and 2x boost pressure. When welding stainless, don't forget to back purge the tubes with argon if you're tig'ing it. Otherwise, the inside of the welds on the tube will have oxidation, and may lead to cracking. Stainless also has a much larger coefficient of expansion (3x of common steel, IIRC?), so you'll need to either leave room for all the tubes to expand equally, or brace the hell out of them so the expansion doesn't create stress risers and cracks in the future (everyone with the 4.0 Jeep engines will understand, where the $5 and $6 header tubes crack).

 

When I was fabbing the intake system for my Camaro (89 IROC, twin turbos, http://www.skulte.com/turbo.html), I found cutting a cardboard 2d template, with trial and error worked well enough to get the mandrel bends cut properly. I did use AutoCAD to make the 2D templates from the 3d model. We used some flexible heater duct with bent welding rods to approximate the shape. Position the header flange and turbo flange, make the collector, and work it from there.

 

A few books that are helpful would be Corky Bell's Maximum Boost and Hugh MacInnes' Turbochargers. Check out the archives for the Junkyard Turbo list on Yahoo and the power adder board at www.thirdgen.org. Let me know if there's anything I can help with!

 

Andris, finally talking about something I know a little about!

[Chris Rizzo]

LastCat,

 

Make sure that you back-purge the assembly before welding...cap-off tube ends and fill assembly with argon. The unshieled backside of a stainless weld will get "sugared"....which basically looks like a big crystalized and porus stalagtite. Not the hot ticket for maxium flow.

 

I'm building my bike headers the old school way...i.e. turn the computer off and cut & paste some parts!

 

[Jack Mitchell]

Hey, this is becoming a seriously cool thread.

 

Keep it coming cause I'm learning lots of new things.

 

Regards, Jack

[Chris Rizzo]

Ok, here's another "trick" that I'm using...

Well, it's not really a trick, per say, just a nice way of doing things...

 

When butt joining pieces of tubing, I have swaged (flared) the receiving tubing. The mating pieces actually "plug" together. If you follow the route of exhaust gas from the port, it will always be traveling into a flared tube.

 

Sure there is a slight transition internally, but it is always in the "smooth" direction, never flowing against a sharp lip of a tube, or roughness of an over-penetrated weld. Also makes welding nicer, ensuring there are no gaps to fill with weld, which invarialbly are less-than-smooth on the inside....make sense?

 

oh, this system will obviously only work with butt joints, and not in the situations where multiple tubes and saddles join...

[LastCat]

Thanks Andris, Chris,

 

Yep, got the book:

 

quote:

---

Corky Bell's Maximum Boost

---

Great reading to get a start on Turbo Charging. I think I'll set MC9 aside and go the old fashion route. I have an extra engine I can model the exh header, using that foam pipe insulation. Shape 6 equal length pieces, and see how they will route to the turbo.

 

CMR? How can I keep the argon in the tubes if the 2 pieces to be welded are not sealed, until after they are welded? Wouldnt the argon seep out between the 2 peices? Great idea, makes great sense too, fatiuge, heat, expansion, would be disasterous.

 

Heres a site that sells the 304 tubing.

Burns

 

I have another friend that has a twin turbo hooked up to his BMW 6 series M30 3.5 liter engine, get this...568hp at the crank, unreal. Straight 6!!!

 

 

Cheers

LastCat

[Chris Rizzo]

They don't have to be super-duper air (argon) tight.....your right, they won't be if they arn't welded up yet! You just have to provide a reasonable backing-gas shield.

 

Here's how I do it:

 

1)Split the gas supply

 

I built a simple "Y" valve off of my argon regulator...one leg going to my TIG torch, the other with an on/off valve and about 8' of hose. Use the secondary line as your back-fill gas supply.

 

2)Plug the tube ends

 

You can just use some masking tape to seal the ends of the tubing, or turn some simple aluminum plugs...I've even seen somebody stuff a raquetball in each end of the tube! Whatever you use to seal the ends, puncture a hole in EACH END- one end for gas fill, the other for gas vent. Feed your gas line in one end and fill her up. I leave the gas back-fill supply on while I weld...but make sure you turn up your regulator pressure, because the two outputs drawing from your gas cylinder will probably cause a big pressure drop in the gas flow to your torch/gun.

 

And to come full circle to your question, yes gas leaks out from the cracks, but also note that I have an extra vent in my other tube plug anyway...when you weld your tubing and create a "vessel"

A) Hot gas expands

Your building positive pressure in your pipes from the back-fill gas supply....

 

It will "blow out" the last little bit our your molten weld if it does not have anywhere to go...so make sure your vent the assembly.

 

If ya'll hav'nt noticed, I've been a welder a hell of a lot longer than a Mastercammer!

 

P.S. LastCat, Do you ever come down to Portland? I was watching a BMW event a few weeks ago at our track, PIR.

[Chris Rizzo]

p.p.s. That Burns Tubing site is very cool...And that twin-turbo straight-6 is beyond cool! How is the "durability"? What type of racing to these Beemer's see?

[chris m]

+1 on making sure that the regulator is gonna flow enough with the back-gas and the torch both drawing on it.

 

I used to use rubber stoppers like the ones mad scientists have sticking in their flasks to plug the ends of vessels being welded (assuming that you aren't welding right next to them, rubber doesn't like 1700 degrees much) but you could just use sheet rubber bandsawed round and belt sanded to fit in the hole.

 

Before you weld, make sure you back purge the pipes until you smell the argon coming out the far end, otherwise you will have an argon/air mix in the pipe and get a grapey (is that a word?) weld inside.

 

Cool thread, much more fun than speeds and feeds.

 

C

 

[ 06-10-2003, 07:04 AM: Message edited by: chris m ]

[LastCat]

Thanks Chris, cmr,

 

I usually head to Longview, my hometown on holidays. I've been to PIR many times, and Woodburn drag strip, where we would campout over night, during the oldies drag races.

 

LastCat

[Jack Mitchell]

Chris,

 

quote:

---

grapey (is that a word?) weld inside.

---

grapey - let it be known that ChrisM has coined a new word

 

quote:

---

Cool thread, much more fun than speeds and feeds

---

Seriously cool

 

Regards, Jack

 

[ 06-11-2003, 12:59 AM: Message edited by: Jack Mitchell ]

[Chris Rizzo]

We've got two horsepower related threads going at once! All us motor heads have hi-jacked the forum yet again!

LastCat, keep us posted on how your project progresses. I'm all ears....