Aluminum pipes.

This subject seems to come up at our practice site fairly frequently.

Why are there no aluminum tuned pipes being offered for use in CL Stunt?

Yes, they would be heavier, but surely this is not a deal killer.

They would almost certainly be more reliable. I don't yet fly a piped two-stroke, but there sure are a lot of epoxy patches on many pipes I see.

In looking over support equipment of the more serious, I also see two and three pipes in reserve. I don't mind paying nearly $400.00 for a really cool assembly of machined parts; but nearly half the cost of an engine for one pipe plus a spare?!

They might be cheaper, although limited production runs might negate some advantages in cheaper, less hazardous materials.

Aluminum pipes might also be quieter. I've still got a bunch of 60-sized "muffled" tuned pipes from a failed business venture in Russia where at one time I was fixin' to bring in some pretty neat 60s for RC Pattern market. I think the pipes are fairly quiet, haven't run one for quite awhile, certainly never in direct comparison to a CF pipe.

I am going to give one of these pipes to Rush, as he is source of original question. But it might take years for him to plug it into his 40VF setup and I am interested in a slightly faster response to the question.

I seem to remember that Frank Williams was running a Mac (metal) pipe at the Lubbock Nats.. High RPM setup.

Maybe I'm confused; who am I thinking about then? Tell me, I command you.

[photo not recovered: 3e69bb3870f12ad5.jpg]

"Natural gas is hemispheric. I like to call it hemispheric in nature because it is a product that we can find in our neighborhoods." -George W. Bush (oil man)

>I seem to remember that Frank Williams was running a Mac
>(metal) pipe at the Lubbock Nats.. High RPM setup.
>
>Maybe I'm confused; who am I thinking about then? Tell me, I
>command you.
>

You are not confused. At least not concerning anything I would make public here. Even though you are indeed a very confused, tortured and convoluted soul. Reference: Your latest political rant directed toward me and via e-mail; at least it was billed properly. And entertaining, what more could one ask?

Memo to All: Only Larry and Nils Norling are allowed to send me political musings. So don't, I remain pretty well informed on that front.

Still, am I the only person who realizes the comany name is MACS? Yes, all caps. As written.

MACS "muffled" pipes are pretty close to what I've got. Internally they are a normal pipe, no baffles. Externally there is an aluminum sleeve, giving casual observer the idea there is no convergent cone.

>This subject seems to come up at our practice site fairly
>frequently.
>
>Why are there no aluminum tuned pipes being offered for use
>in CL Stunt?
>
>Yes, they would be heavier, but surely this is not a deal
>killer.

I have two Russian pipes, They are lighter I will be trying one in my new plane.

Robert, those look like speed pipes, are you sure the will give the stunt run we want?
A stunt pipe not only keeps the engine's revs under control, but also gives the engine a boost when loaded and holds it back when unloaded,

That means thar in a wingover the plane should pick up some power to go up and lock the revs on the down part, making the prop act like a break.

Those speed pipes, all they do is suck all the power ffrom the engine, no thought being given to the things above.

>Robert, those look like speed pipes, are you sure the will
>give the stunt run we want?
>A stunt pipe not only keeps the engine's revs under control,
>but also gives the engine a boost when loaded and holds it
>back when unloaded,
>
>That means thar in a wingover the plane should pick up some
>power to go up and lock the revs on the down part, making
>the prop act like a break.
>
>Those speed pipes, all they do is suck all the power ffrom
>the engine, no thought being given to the things above.
>
>Ion
Ion a true expansion chamber has no baffles. It offers boost from reversion. It is all timed to the bore and stroke and port height. I do not know if these will work. But I will try them.

>>Robert, those look like speed pipes, are you sure the will
>>give the stunt run we want?
>>A stunt pipe not only keeps the engine's revs under control,
>>but also gives the engine a boost when loaded and holds it
>>back when unloaded,
>>
>>That means thar in a wingover the plane should pick up some
>>power to go up and lock the revs on the down part, making
>>the prop act like a break.
>>
>>Those speed pipes, all they do is suck all the power ffrom
>>the engine, no thought being given to the things above.
>>
>>Ion
> Ion a true expansion chamber has no baffles. It offers
>boost from reversion. It is all timed to the bore and stroke
>and port height. I do not know if these will work. But I
>will try them.

They ought to work fine. Start with the same as "baffle-pipe" lengths, and measure from a point 2/3 of the way from the small end of the tail cone. That will necessitate, by my eye, a pretty long piece of constant-diameter tubing to get them long enough.

They are also likely to be very noisy. Frank Williams's at the 94 NATS was incredibly loud.

But there's no functional need to have baffles inside, in fact, I would guess it would be a lot more straightforward to adjust, since there is only one, soft, return wave instead of several pretty sharp ones. Most tuned pipe applications don't have baffles, and the waves don't know you are trying to use them as regulators instead of enhancers.

Dan, aluminum pipes are just as "Leak prone"as the CF ones, with the disvantage that leaks would be harder to fix.

Besides that, if aluminum was any better than carbon fiber Billy and Randy qould be using it.

>Dan, aluminum pipes are just as "Leak prone"as the CF ones,
>with the disvantage that leaks would be harder to fix.

Wrong on both counts, at least in my experience of actually using aluminum pipes, watching friends struggle to keep CF pipes leak-free.

>
>Besides that, if aluminum was any better than carbon fiber
>Billy and Randy qould be using it.
>
>Ion

I'm not so sure about that. For one thing, if an aluminum pipe were even 2 grams heavier than a CF pipe, Billy would snort and reject it out of hand. Okay, I embellish the tale, but not by much.

Still, weight has got to be a factor in the thinking of producers of CF pipes, I'm just not so sure there aren't a lot of consumers out there who would welcome aluminum pipes.

Tooling might be a problem which leads to molding pipes in CF, as in there is quite likely a larger initial investment if working with aluminum.

Still, given a design known to work, how hard could it be to simply have a company such as MACS do the heavy lifting, one of us to do the selling? I seem to remember that McAllister's primary operation is as a job shop in the specialized business of forming alumimum tubes for industrial uses, toy airplane stuff is merely a sideline.

>>Dan, aluminum pipes are just as "Leak prone"as the CF ones,
>>with the disvantage that leaks would be harder to fix.
>
>Wrong on both counts, at least in my experience of actually
>using aluminum pipes, watching friends struggle to keep CF
>pipes leak-free.
>
>>
>>Besides that, if aluminum was any better than carbon fiber
>>Billy and Randy qould be using it.
>>
>>Ion
>
>
>I'm not so sure about that. For one thing, if an aluminum
>pipe were even 2 grams heavier than a CF pipe, Billy would
>snort and reject it out of hand. Okay, I embellish the tale,
>but not by much.
>
>Still, weight has got to be a factor in the thinking of
>producers of CF pipes, I'm just not so sure there aren't a
>lot of consumers out there who would welcome aluminum pipes.
>
>Tooling might be a problem which leads to molding pipes in
>CF, as in there is quite likely a larger initial investment
>if working with aluminum.
>
>Still, given a design known to work, how hard could it be to
>simply have a company such as MACS do the heavy lifting, one
>of us to do the selling? I seem to remember that
>McAllister's primary operation is as a job shop in the
>specialized business of forming alumimum tubes for
>industrial uses, toy airplane stuff is merely a sideline.
>
>Dan

I can tell you the pipes I have pictured here are afew grams lighter than th CF pipe. Also I am working on sanding them thinner. I think the weight could go down to 1.25 OZ

LAST EDITED ON Sep-29-04 AT 04:55 PM (CDT)
 
Dan,

You could probably save some cash by molding your own pipe.

My buddy Paul recently showed me a pipe that he molded from a borrowed mandrel. It works quite well.

Now I want him to show me how he built his. Prehaps then I could borrow his mandrel and lay up a pipe for my 40-vf and save myself a few bucks!

Yep! Pipe motors are a real investment!

>You could probably save some cash by molding your own pipe.
>
>My buddy Paul recently showed me a pipe that he molded from
>a borrowed mandrel. It works quite well.

I saw that, too. Looked OK.

>>>Why are there no aluminum tuned pipes being offered for use in CL Stunt?<<<

Why you think? I am sure several of them was in Muncie (including that one in my model ).

Here is my new pipe for .40 size engine. The diameter is 35mm (1.3") and weight 40g (<1.5oz)

Couple of years ago I cut a MAC'S Pipe and added a baffle before the divergence cone as per GMA. Pipe worked OK but it leaked at the header coupling. The heat was the culprit. I tried HIGH TEMP SILCONE TUBING and still found leaks.
ASSESMENT. Aluminum’s heat expansion is too great for the length of pipe.
Aluminums rate of expansion is almost 1 foot per 100’

>Couple of years ago I cut a MAC'S Pipe and added a baffle
>before the divergence cone as per GMA. Pipe worked OK but it
>leaked at the header coupling. The heat was the culprit. I
>tried HIGH TEMP SILCONE TUBING and still found leaks.
>ASSESMENT. Aluminum’s heat expansion is too great for the
>length of pipe.
>Aluminums rate of expansion is almost 1 foot per 100’

Ron B.
F4Fguy

Scott:

FYI:

Aluminum alloys;
Coefficient of linear expansion= 0.000011"/"/Deg.F.

Carbon/Epoxy;
Coefficient of linear expansion=0.000022/0.00003+"/"/Deg.F. depending on the particular epoxy and fiber ratio.

That is 3"+/100ft. for Al,and 6"-9"/100ft. for carbon epoxy, both at 350Deg.F.

I've been using MAC's pipe in RC since about 1980 and never had a leak. I use the on almost every airplane as the engines run better, more power and most of the fuel and oil ends up in the rear of the plane.

As for MAC's products,last I heard the shop is being run by Wally's brother Dave. When they first started I would loan them engines to use as a platform for new headers. They have often built custom headers for various configurations at no extra charge and would replace or repair a broken header for $5.00.

I haven't been by there in a year or so but I'm sure Dave would be willing to work with the CL Stunt guys to build a pipe for stunt.

If someone would like to pursue this, let me know and I'll call Dave and get the smart people together to see if we can make it happen.

Note: My office is about 10 miles away and I would gladly deliver any information, samples, etc. to Dave.

BGM AMA 27695

I sugest we ask Randy Smith why he doesn't use aluminum instead of CF on his pipes before we proceed on thos thread.

Randy?

by any act, error, or omission, I have, intentionally or
unintentionally, displayed any breedist, disciplinist, sexist, racist,
culturalist, nationalist, regionalist, localist, ageist, lookist, ableist,
sizeist, speciesist, intellectualist, socioeconomicist, ethnocentrist,
phallocentrist, heteropatriarchalist, or other violation of the rules of
political correctness, known or unknown, I am not sorry and I encourage you
to get over it.

I find this thread somewhat amusing . The weight of a contemporary 4 cycle motor ex Saito 72 is used with very little bemoaning its weight. A contemporary 60 sized motor and aluminum pipe should not be such an insurmountable problem.
Flew a few 36 planes with the MACS muffler and the gain far exceeded the weight.
Dennis

>I find this thread somewhat amusing .

>Dennis

Ron B.
F4Fguy

You're not the only one, Dennis, though perhaps for different reasons.

Igor,

Who made the pipe pictured?

Robert Storick: THe pipes you show have no 2nd or 3rd chamber, they are simply a convergent cone.the simplest lightest cheapest type of aluminum pipe available and usually are used for boats. They are very noisy and intended for high R.P.M.s. The pipes we use have the other chambers added to make them quieter.by adding a sort of after muffler after the first baffle. There are many aluminum pipes used in pattern and a lot of them are made by Hatori and are shockingly expensive compared to the ones we are used to. Look on Central hobbies ad and see the listing for a muffler and header for 4 cycle engines as often used in pattern and notice the total price of $199.85. We often forget how lucky we are here in "Stuntland" http://www.centralhobbies.com/Exhaust/mufflers.html Keith Varley

> Robert Storick: THe pipes you show have no 2nd or 3rd
>chamber, they are simply a convergent cone.the simplest
>lightest cheapest type of aluminum pipe available and
>usually are used for boats. They are very noisy and intended
>for high R.P.M.s.

If he sets them the same length, of course. If he adds enough length to the front of the pipe to get the same tuned length as a baffled pipe, it should run at whatever RPM is appropriate for the length.

> Robert Storick: THe pipes you show have no 2nd or 3rd
>chamber, they are simply a convergent cone.the simplest
>lightest cheapest type of aluminum pipe available and
>usually are used for boats. They are very noisy and intended
>for high R.P.M.s. The pipes we use have the other chambers
>added to make them quieter.by adding a sort of after muffler
>after the first baffle. There are many aluminum pipes used
>in pattern and a lot of them are made by Hatori and are
>shockingly expensive compared to the ones we are used to.
>Look on Central hobbies ad and see the listing for a muffler
>and header for 4 cycle engines as often used in pattern and
>notice the total price of $199.85. We often forget how lucky
>we are here in "Stuntland"

Keith: I know this. As I stated before a true expansion chamber has no chambers or baffels. The prop is what you use as a brake. The low pich is like running in 1st gear.

Robert....How do you tune that kind of pipe without a baffle?

It works the same as one with baffles you adjust the length. Regulates the speed and boosts engine output. Speed control is as good as a baffled pipe, maybe better. The noise level can be reduced by running a stinger tube through the exhaust outlet to the widest part of the pipe useing high temperature silicon gasket material as a seal. Since the pipes are shorter an extension piece will probably be needed the tail boom from an RC helicopter is the right size and light.

If you have access to Flying Models where Dean Pappas discusses the use of tuned pipes for stunt he gives a very good explanation of how they work and where to start in setting them up. The articles appeared about 1990.

One of the reasons we use carbon pipes is the original carbon pipes only weighed 1 OZ at a time when the pipes such as MACS weighed about 2.5 OZ, 4 OZ for a muffled pipe.

>Robert....How do you tune that kind of pipe without a
>baffle?

Measure to the point 2/3 the length of the tail cone from the small end. which is the centroid of the cone in side view. Then in or out as needed. Just exactly like it shows in the Two-Stroke Tuner's Handbook; which, I might add, also mentions the possibility of using the pipe as a rev limiter - and no baffles anywhere. To keep from over-revving and maybe blowing the motor.

Brett,

>>Measure to the point 2/3 the length of the tail cone from the small end.<<

Could you explain this a bit. Do you mean measuring from the stinger forward 2/3 the length of the tail cone?

LAST EDITED ON Sep-30-04 AT 12:28 PM (CDT)
 
>Brett,
>
>>>Measure to the point 2/3 the length of the tail cone from the small end.<<
>
>Could you explain this a bit. Do you mean measuring from the
>stinger forward 2/3 the length of the tail cone?

Yes, for a single-tapered cone. Or in other words the centroid in the side view, and for more complex shapes.

super thanks guy's
Scott(see this thing works)Riese

Dan,
I've used aluminum pipes for quite a while. This year's Nats, last year's Nats, in the Friday winds (I'd have made the finals if I'd just got off my chair and flown my second flight - but that's another story) Even back to '93. The Lubbock Nats was unique in that I was launching at 13K rpm. It was indeed noisy with no internal stinger.

I use some old speed pipes (either Rossi or OPS I don't know) with an internal stinger. These pipes are quite a bit lighter than MACS or Prather but still a bit heavier that carbon. MACS can be carefully HCl dipped and the weight reduced significantly.

The internal stinger is a carbon or allum. tube stuck into the existing stinger. It goes up to about the high point of the pipe. A small hole is needed at the point of the tube that corresponds to the end of the contraction cone to let the oil get out. This does make the sound quite tolerable. Most people don't know now that I'm not running a carbon pipe.

Two reasons in my opinion for allum. over the carbon. 1) the shape is correct 2) they don't leak.

I have $500 maybe $700 of carbon pipes. The last one bought for $100+ flew two flights before the baffles came loose. Most have pin hole leaks eventually. Pin hole leaks are most important the closer they are to the engine. I have had good luck with ES Composites and Brian Eather carbon pipes. The ES pipe unfortunately seems to have holes in the baffles that are too small ... nothing though that a drill extension and a conical rasp can't cure. But then its still just a baffled pipe ... the wrong shape I think .. just a muffled megaphone. But then a lot of people make them work quite well. People like world champs and the like.

The "full wave" speed pipe from my experience has a better response than a baffled pipe. Both simply alter the power curve of the engine to allow us to run on the "backside" of the power curve. The "full wave" pipe makes the curve fall almost straight down. The slope of the operating curve is much steeper than that for the baffled pipe. The control from the pipe is more effective.

Another thing about alluminum is its strength relative to carbon. The serious boat guys don't use alluminum .... they use stainless steel for their pipes. They say the performance is better. I've wondered if it's cause of the potiential for distortion during the exhaust pulse. This wave is a real serious bang.

I'll try to publish some pipe curves

GUY'S what about heat draw on metal pipes. If they are hotter or cooler will that change tune or note of the pipe?

I've had Russian CL Speed guys claim two identical pipes, but one in natural aluminum finish, the other painted black, operated differently, were each to be used for certain conditions and/or engines.

Up until that point in time I was pretty well convinced there was no such thing as a Russian sense of humor, at least not while actually standing on Russian soil, that surely they wouldn't think of teasing their new gringo friend in such a manner...

*Hey, Rush!* I posted this thread on your behalf, thanks for leaving me to flop around out here all by little ol' lonesome. At least we got some answers, even got none other than Frank Williams fired up, how often does *that* happen?! Looking forward to seeing how your Impact flies with "...just another ounce or two..." of mass added to its current bulk, a fair amount of this mass falling behind balance point.

snip

>Looking forward to seeing how your Impact flies with
>"...just another ounce or two..." of mass added to its
>current bulk, a fair amount of this mass falling behind
>balance point.
>
>Dan
>

Danny boy...Just give it to me, and I'll test it for you.

I can do it with a 40 or a 60.

Do you have a pipe like this for a 60?

OK Howard, you're off the hook now. Let's see if the ole Dirt Master comes through now!!

Hands off. That's my pipe. After all the tip weight I removed from my airplane, I need ballast anyhow.

I have a whole box of used pipes and some new. These were given to me my best flying buddy, BOB LEE, before he passed away last November. I'm not sure exactly how many for which size engines. If you are interested in testing them, as I can't hardly get time to fly, I'll send some to you. If you get something that works pretty well we can get with Dave at Mac's Products to see what he can do to lighten them if there is enough call for them. I have some standard and some muffled. Send me an E-mail at [email protected] and I'll give you my cell#, another e-mail address, etc.

I'm thinking of putting a pipe on the ARF Cardinal with a Brodak 40,
if I ever get time to break it in and fly. If I don't have a header laying around that fits,I guess I'll have to go see Dave.

AMA 27695

Thanks for bringing this up. Composites are nice, but I'd think aluminum would make better pipes. Everyday epoxy goes bad at less than 250 degrees F. High-temperature matrix material is available, but composite tooling and materials costs go up pretty fast with temperature. I have a couple of six-year-old pipes that are made out of stuff that is marginal at the temperatures at which the pipes operate. They get holes and the front part of the pipe gets crumbly. New composite pipes may be better and could be lighter. I saw some made by a guy in Utah (I'm embarrassed to have forgotten who) that look great. Surprisingly, I have seen only one aluminum baffle come loose. Glueing carbon to aluminum is something that airplane makers avoid.

I suspect Dan of being up to something, perhaps something commercial. My phone number is adjacent to his in the PAMPA directory, so I get a lot of his phone calls. One recent wrong-number call was from the cosmic expert on welding thin aluminum.

Paul,

You, Howard and myself must establish a new rule: When one of us is flying, we can't talk. You missed my aluminum pipe conversation with Howard, he missed mention of the tip-weight saga, I probably missed truly inspired, nasty things being said about current trim level of my Impact.

Pipes under consideration are for 60s; I was kinda thinking what would amount to a large-volume pipe on Howie's puny 40 would be of interest.

There are a whole slew of smaller pipes laying about in the garage, I'll look through them. None are special in any way, at least not as far as I know. The RC Pattern-specific pieces are quite nice as they look cool and have a "muffling" sleeve over rear cone. Not unlike some of the MACS pipes. They are not particularly light, partly due to roubust (read: reliable) construction, the rest of it coming from external sleeve.

And you *know* I always come through! Especially when I now have bolted to a Saito 56 one of your best CF props, this on some kind of ill-defined "loan" arrangement.

Howard,

I tend to agree, aluminum would seem to be a better material for pipes, although with none of the *Wow!* factor of CF pieces. And with Frank using them, we're in really, really good company.

Were there to be a commercial interest on my part, I would be loathe to discuss it here. The supply of pipes we're talking about would have been reduced by about 10% if you had borrowed one and then tested it on your Impact without first digging into said model, replacing a frayed leadout.

You missed it, due to above and proposed rule not being in effect last Sunday, but incident with Mike Conner and myself determining that you were packing too much tip weight, resulting in serious resistance to the obvious on your part, served as inspiration for upcoming Bad Boy Stunt column. Yes, you are named specifically. Your actions were noted as well. I think it quite funny, although such may not be a universal reaction.

Let's make a deal: We will both begin taping phone conversations, as I too once in awhile get a "wrong number" call from toy airplane folk. It can indeed be funny...

>I've had Russian CL Speed guys claim two identical pipes,
>but one in natural aluminum finish, the other painted black,
>operated differently, were each to be used for certain
>conditions and/or engines.

This would be true. The guys on the salt flats found out many many years ago that flat black is simply the best finish on a motor. It desipates the heat faster and more evenly than any other color or finish they applied to the engines. The block and heads would be painted black to get the heat out of the motor the fastest and most evenly throughout the run. Even better that the natural cast finish or a polished finish or fins or purple or blue or orange, and those guys will try anything for even a tenth of an MPH. I have read in many different books that flat black gets the heat OUT the best. Dont know why it is that way but many came to SAME conclusion at DIFFERENT times and places.

>This would be true. The guys on the salt flats found out
>many many years ago that flat black is simply the best
>finish on a motor. It desipates the heat faster and more
>evenly than any other color or finish they applied to the
>engines.

Snip, snip...

Yes, I have heard this before. An opposing theory has merit, and that is the layer of paint itself serves to insulate the parts to a certain extent, resuling in no improvement or even a slightly higher running temperature.

I honestly have no idea, other than a natural and finely-honed skepticism to what appears to be intuitively correct, in this case engine blocks painted black running cooler than an unpainted block. For example, I don't know of the Formula 1 or MotoGP guys painting engine blocks, they appear to be as-cast or -machined aluminum...

We need some input from Ron the F4F guy. I'll bet he knows and can back it up with empirical data.

>>This would be true. The guys on the salt flats found out
>>many many years ago that flat black is simply the best
>>finish on a motor. It desipates the heat faster and more
>>evenly than any other color or finish they applied to the
>>engines.
>
>Snip, snip...
>
>Yes, I have heard this before. An opposing theory has merit,
>and that is the layer of paint itself serves to insulate the
>parts to a certain extent, resuling in no improvement or
>even a slightly higher running temperature.
>
>I honestly have no idea, other than a natural and
>finely-honed skepticism to what appears to be intuitively
>correct, in this case engine blocks painted black running
>cooler than an unpainted block. For example, I don't know of
>the Formula 1 or MotoGP guys painting engine blocks, they
>appear to be as-cast or -machined aluminum...
>
>We need some input from Ron the F4F guy. I'll bet he knows
>and can back it up with empirical data.
>
>Dan

Ron B.
F4Fguy

Dan:

Thanks for the vote of confidence.

You're right,black paint does not necessarily heat rejection make. Reynolds was very active in solar panel development and many emissivity tests were done on bare ,chemically treated,anodized, painted, and electro-static coated aluminum. To (over)simplify the results, bare had better emissivity than any but the most highly specialized treatments. The mechanism is that the transfer through the coating and the interface cost more emissivity than was gained by a black(or any other color) paint.Anodizing is, in itself an insulator.

The other side of the picture is that AL is a pretty good emitter and conductor,much better than carbon/epoxy. It's also (at 300+ deg F)much stronger.

In my opinion, aluminum pipes make very good sense, technically. Carbon is a LOT easier to produce in small volume.It's also easier to modify for specific apps,and ,at to really take advantage of a pipe it needs to be tailored to the engine(desired RPM,intake, exhaust,and rotary valve timing),fuel, plug, prop, and, eventually, the airplane. Unless you can spin your own cones,make your own header pipes and stingers,and weld it all together over and over again,it's a long, costly road.

While I'd agree with some of what's been said above, most of it reveals a profound lack of understanding of just how a pipe works.The point about temperature is an example.The wave travels at the speed of sound in the medium and at the temperature of the medium.In this case the medium is a mixture of gasses much different than air,and the speed of sound may not be predictable. Aside from temperature(more later), the make-up of the fuel,the mixture strength,the efficiency of combustion,and the compression ratio all effect not only the composition,but the temperature of the gasses entering the pipe.The RPM determines the time available for heat loss during the passage through the pipe. All of this determines the average temperature in the pipe.

The biggest factor affecting the tuning of a pipe is the speed of the wave.This in turn is temperature dependent. I should point out at this point,that the one HUGE error in the famous Pappas piece is that the speed of sound goes up as temperature goes down.In fact,the exact opposite is true.

This is another point for Al pipes Al emits better than epoxy,more heat is rejected per cycle,Temp is lowered and the wave speed goes down. The result is a shorter,lighter pipe for the same conditions.

I can't let go of this without addressing one other thing. A short pipe with a long header WILL NOT operate any thing like a pipe designed for the conditions with the same tuning length.A pipe can be used over a small range of speeds by trimming the header or extending it a little, maybe as much as 3/4-1 inch,but you'll still give up some potential over a pipe of the right length and with each component tuned to the particular porting and desired RPM range. A properly designed pipe will not only control the peak and the amount of braking,it can pump the torque and shape it in any part of the range. It not only improves top cylinder scavenging but also can draw more more through the venturi!,allowing larger venturis and making more power yet. Unfortunately, the pipe has not really been exploited to it's potential.

Having told you much more than you EVER wanted to know and added little but more fuel to the debate,I'll leave you now,

Ron B.

Ron you wrote .....
"While I'd agree with some of what's been said above, most of it reveals a profound lack of understanding of just how a pipe works.The point about temperature is an example.The wave travels at the speed of sound in the medium and at the temperature of the medium.In this case the medium is a mixture of gasses much different than air,and the speed of sound may not be predictable" ......

Actually ... an exhaust pulse is of such amplitude that it actually travels somewhat "faster" than the local speed of sound. Pete Soule caught me on this one several years back when I wrote it in "powertrain".

>While I'd agree with some of what's been said above, most of
>it reveals a profound lack of understanding of just how a
>pipe works.The point about temperature is an example.The
>wave travels at the speed of sound in the medium and at
>the temperature of the medium.In this case the medium is
>a mixture of gasses much different than air,and the speed of
>sound may not be predictable. Aside from temperature(more
>later), the make-up of the fuel,the mixture strength,the
>efficiency of combustion,and the compression ratio all
>effect not only the composition,but the temperature of the
>gasses entering the pipe.The RPM determines the time
>available for heat loss during the passage through the pipe.
>All of this determines the average temperature in the pipe.

I don't think anyone necssarily misunderstood it in the above - maybe didn't mention it, but that doesn't mean it's misunderstood.

Frank and I discussed it once. Hadn't seem him in a year, I was out talking to someone in the Lee's Inn parking lot. We walks up to me, and says "Hi! I think it's about 1400-1450".

>
>>While I'd agree with some of what's been said above, most of
>>it reveals a profound lack of understanding of just how a
>>pipe works.The point about temperature is an example.The
>>wave travels at the speed of sound in the medium and at
>>the temperature of the medium.In this case the medium is
>>a mixture of gasses much different than air,and the speed of
>>sound may not be predictable. Aside from temperature(more
>>later), the make-up of the fuel,the mixture strength,the
>>efficiency of combustion,and the compression ratio all
>>effect not only the composition,but the temperature of the
>>gasses entering the pipe.The RPM determines the time
>>available for heat loss during the passage through the pipe.
>>All of this determines the average temperature in the pipe.
>
> I don't think anyone necssarily misunderstood it in the
>above - maybe didn't mention it, but that doesn't mean it's
>misunderstood.
>
> Frank and I discussed it once. Hadn't seem him in a
>year, I was out talking to someone in the Lee's Inn parking
>lot. We walks up to me, and says "Hi! I think it's about
>1400-1450".
>
> Brett

Ron B.
F4Fguy

Brett:

Sorry ,but I can't agree.I think few of the respondents show a real appreciation of how the pipe really works.Look at this thread again.Most of the discussion is on subjects either mis-(or imperfectly) understood.I write off anyone's view who references the Pappas piece as gospel.Oh sure there's some understanding of the tuning length vs RPM,but there are far too many variables to say that, understanding that is knowing how a pipe does it's job.

Don't get me wrong,I don't think these are bad people,just that they, in large part, don't know what they are talking about. The very idea that you can take an existing pipe design ,put it behind another engine with different time areas and possibly even displacement,and get anywhere near optimum performance is unrealistic. Can you make it run?Of course. Will it be better than without the pipe? Maybe. But it won't be equal to a pipe designed for that engine/fuel/prop combination.

The design parameters for a "speed" pipe are the same as for a stunt pipe.The input data may be different,but the procedure is the same,and the function of each element of the pipe is the same.As you've said,a long taper on either the divergent or convergent cone will "soften" the transition for that particular function. This may or may not be a desireable trait,but it has to be designed into the package. The fuel will have a huge effect on the exhaust temp,as will the compression ratio and the needle adjustment.

The heat loss will greatly effect the tuning ,and it's changing for each element of the pipe. Consequently the wave speed is not the same all the way through the system and it also varies for the returning wave. Sure there are formulae out there for calculating all the lengths and diameters, but they're all approximations,even the temps.

Since the temp varies from the port to the stinger,the only reasonable temperature to use as a working number is the mean temp,not the exhaust tempat the port, and this is what most of the formulae use as a basis. I once ran a deconstruction on a bunch of published tuned lengths from various flyers to see if I could back out the mean gas temp from the length and RPM stated (this was "tech" info from Nationals flyers some years back)I got temps from 250deg F.to over 550deg.F. These are WAY lower than anything reported in the technical literature(Jennings says 1670 fpm,that =~700deg.F. This is not too surprising since we're talking small engines with high surface to volume,and methanol fuels at high fuel air ratios. On the other hand it is a factor I've never seen or heard addressed,except in passing,and then in the context of the Pappas article which stated it backwards,and the individual I was talking to refused to consider the article mistaken.

As a final note I have to say ,I've taken some shots at Pappas' article.This in no way is to discredit his work overall. He mispoke in one regard ,albeit a major one, but it's still a seminal work in our field.

Ron

I was watching this thread about pipe materials a couple of weeks ago knowing that we would be testing, a carbon fibre pylon race pipe in the near future.

Well testing went better than expected, we saw an increase in bench RPM for the same design pipe in carbon over aluminium, we know why this is, but I thought I would give you some up to date figures on EGT, we measured 430 deg C in both the aluminium and carbon pipes, we noticed that the carbon pipe cooled down much quicker than the aluminium version, its mass was only 5 grams less. we have not got any degradation of the header and no leaks, although the pipe was manufactured in an autoclave.

LAST EDITED ON Oct-17-04 AT 08:20 PM (CDT)
 
>Ron
>
>I was watching this thread about pipe materials a couple of
>weeks ago knowing that we would be testing, a carbon fibre
>pylon race pipe in the near future.
>
>Well testing went better than expected, we saw an increase
>in bench RPM for the same design pipe in carbon over
>aluminium, we know why this is, but I thought I would give
>you some up to date figures on EGT, we measured 430 deg C in
>both the aluminium and carbon pipes, we noticed that the
>carbon pipe cooled down much quicker than the aluminium
>version, its mass was only 5 grams less. we have not got any
>degradation of the header and no leaks, although the pipe
>was manufactured in an autoclave.
>
>Barrie

Ron B.
F4Fguy

Barrie:

I'm not at all surprised at 430C EGT, note that's about half the Jennings number. But, it doesn't address my point,which is that,EGT(as such)is not the criterion.We need to know the mean gas temperature throughout the tuning length. As you've noted,the pipe material will affect this,as carbon/graphite and aluminum have different conductivities and emissivities.The accurate measurement of temps in this environment is extremely difficult,as the thermal inertia is low, and the transient times are short.Thermocouples have too much mass. They can give mean temps at one point in the stream, but will not see the transients, add to this that their mass will affect the result.Without knowing the emissivity and conductivity of all the materials and the gasses,IR is no better. Heisenberg is alive and well! Anything we do to measure the conditions or the effect, affects the result.

What it comes to ,in the end,is that,the best method is to infer the temperature from the results and physical dimensions of a working pipe on the subject engine and use the result to abbreviate the cut and try. Even this has many pitfalls,as a minor fuel,or fuel/air ratio change can have major tuning effects,as can CR, plug, etc.Add in that,a change in pipe configuration,i.e. diffuser taper,or header length,affects the whole tuning regime.

Fortunately, while the specifics are extremely elusive, the concepts are relatively simple. A long taper is "softer" than a baffle,lower rpm needs a longer pipe, and higher temp needs a longer pipe.Too lean will make the pipe seem too short,too rich too long. Higher CR, shorter pipe (if EVERYthing else stays the same),higher nitro/lower CR,longer pipe (same caveat).

Somewhere above there's a reference to noise and mufflers.Pipes can be very easily muffled by simply extending the "stinger" to the inside with a perforated pipe plugged on the inner end and extending to the beginning of the reflecting cone.

One last note: I am a little surprised that the carbon pipe cools "faster"than the Al one. I'd expect the epoxy to offset any advantage of the carbon emissivity. Can you quantify this? Also,were the tuning lengths the same for both pipes,or was each optimised?

I cant quantify the quicker cooling of the carbon pipe, maybe it is due to increased surface area because of the wrinkled external finish from the bagging materials- just guessing.

Both pipes were set at the same length, the carbon pipe was not optimised for the higher RPM it just done it!, would have gone a little quicker if it had been shortened.

Who said it was epoxy resin?

>I cant quantify the quicker cooling of the carbon pipe,
>maybe it is due to increased surface area because of the
>wrinkled external finish from the bagging materials- just
>guessing.
>
>Both pipes were set at the same length, the carbon pipe was
>not optimised for the higher RPM it just done it!, would
>have gone a little quicker if it had been shortened.
>
>Who said it was epoxy resin?
>
>Barrie

Ron B.
F4Fguy

Okay! Binder, adhesive, molding compound, whatever. I was speaking to the probability that the composite is unlikely to have as good conductivity or emissivity as the carbon alone or the Al. If in fact the two pipes are the same except for material, the higher RPM would indicate a lower temperature(unusual,not impossible). That is, the pipe would "act" shorter.If the load(prop?) is the same it would also indicate higher HP.

We thought the gas temp might be higher, but that would make the pipe effectivly shorter because the gas travels faster when it is hot, anyhow the gas temp was within a couple of degrees of the Al pipe, it was actually slightly lower in the carbon pipe.

Our only reason for manufacturing the test pipe was to see if carbon fibre was a viable prototyping material to conduct pipe testing with, as stated in other replys it is much easier to do the tooling for a carbon pipe than an AL pipe.

First real tests are this weekend in our last pylon meeting, we will run the pipe mentioned in the tests plus one new type.

When I started looking at this thread for the education, I thought my knowledge was limited. Now I am sure of it! I thought that looking at a couple of tables and adjusting fuels and needle valves
etc would allow me to take advantage of what tuned pipes have to offer. WRONG!! Maybe there is some kind of publication that someone could suggest for my edification in this subject area, God knows I need it!

any finish you put on a hot part, like the pipe, or the engine head, CAN change the heat transfer and make the engine run differently. It all depends on how much it affects the emissivity of the part(how much heat it radiates), and how much it affects heat conduction out of the part. Some paints will emit more of the heat, others less. I know some anodizing finishes can greatly reduce the heat radiation. Black is not always better.

Hopefully any paint sold as a finish for engines has been tested to actually shed heat better, but you never know.

>any finish you put on a hot part, like the pipe, or the
>engine head, CAN change the heat transfer and make the
>engine run differently. It all depends on how much it
>affects the emissivity of the part(how much heat it
>radiates), and how much it affects heat conduction out of
>the part. Some paints will emit more of the heat, others
>less. I know some anodizing finishes can greatly reduce the
>heat radiation. Black is not always better.
>
>Hopefully any paint sold as a finish for engines has been
>tested to actually shed heat better, but you never know.

Ron B.
F4Fguy

Phil:

Unfortunately the "engine paints" black or otherwise are formulated to withstand higher temps.Emissivity isn't one of the criteria.

Just to add to the discussion:

http://www2.towerhobbies.com/cgi-bin/WTI0095P?FVSEARCH=tuned+pipe+MACS&FVPROFIL=++

Randy, those pipes are product of one flyer here (Zdenek Krizka). We use it here for longer time. They are molded from thin soft alu pipes and then glued by hi-temp glue for alu. It allows almost any configuration of baffles / silencers / stingers ....

On picture below is one pipe with silencer after pipe and angled exhaust. Another pipe shows a pipe insert allowing custom side holes to custimize proper silencing / throughput.

I personally prefer singe baffle pipes. We fly on relatively turbulent fields and jump in jump out is very often counterproductive as it reacts on every input, not only nose up nose down. Single baffle pipe allows to lock to one rpm and only sound shows how and when is the shaft loaded / unloaded without clear change in RPM. That is what I had in Muncie with .60 engine.

In 2002 in Sebnitz I had smaller engine .46 in the same MAX and it was too small power (or better prop was too small) for such constant rpm mode, so that was probably reason why I ended up with very short pipe tuned to back cone like Brett suggested. That cone allows little variation in RPM as it is not so sharp as vertical baffle ... I just wanted to say that that such tuning to back cone is possible also on our stunt pipes with baffles still in. The last picture shows how short was the pipe. Fot that purpose I use spread sheet calculating approximate lap times from prop pitch, baffle and back cone positions. It is very helpfull at initial trimming.

>This subject seems to come up at our practice site fairly
>frequently.
>
>Why are there no aluminum tuned pipes being offered for use
>in CL Stunt?
>
>Yes, they would be heavier, but surely this is not a deal
>killer.
>

I thought all the tuned pipes were aluminum. I bought 2 tuned pipes and they are both aluminum.

Something interesting I have noticed about a tuned pipe, if you build your own tuned pipe out of brass for example then build another one identical to the first one only this time make it out of a differrent metal it will "NOT WORK." Even if the 2nd tuned pipe is 100% identical to the 1st tuned pipe it will not work if it is made out of a different metal. If you build the 1st tuned pipe out of steel then built a 2nd and 3rd pipe out of aluminum and brass they will not work.
If you build the 1st tuned pipe out of aluminum then built a 2nd and 3rd pipe out of steel and brass they will not work. After doing so research I learned it has to do with the heat radiation rate of each metal is different.

LAST EDITED ON Oct-19-04 AT 12:52 PM (CDT)
 
By far the most common material for 40- through 65-sized pipes in CL PA is carbon fiber.

Virtually all pipes for motorcycles are fabricated from steel sheet.

Ditto for pipes used on karts.

In fact, in the big world of tuned-pipe equipped two-strokes, we are most unusual in the use of either aluminum or CF as a material for pipe fabrication. Mostly because in a great many applications there are some *very* serious packaging issues with which we do not have to contend.

There are people active on this very site who, if shown a pipe for a CR250, would tell you it cannot possibly work. Much as they claim for certain mufflers fitted to certain model aircraft engines used to win certain Expert PA contests as flown by a certain mid-pack "Expert" flier who is certain this sentence certainly contains way too many uses of the word "certain," but doesn't really care as folk like a certain Larry Cunningham will think it certainly funny. So there...

LAST EDITED ON Oct-17-04 AT 05:39 PM (CDT)
 
>By far the most common material for 40- through 65-sized
>pipes in CL PA is carbon fiber.
>
>Virtually all pipes for motorcycles are fabricated from
>steel sheet.
>
>Ditto for pipes used on karts.
>
>In fact, in the big world of tuned-pipe equipped
>two-strokes, we are most unusual in the use of either
>aluminum or CF as a material for pipe fabrication. Mostly
>because in a great many applications there are some *very*
>serious packaging issues with which we do not have to
>contend.
>
>There are people active on this very site who, if shown a
>pipe for a 250CR, would tell you it cannot possibly work.
>Much as they claim for certain mufflers fitted to certain
>model aircraft engines used to win certain Expert PA
>contests as flown by a certain mid-pack "Expert" flier who
>is certain this sentence certainly contains way too many
>uses of the word "certain," but doesn't really care as folk
>like a certain Larry Cunningham will think it certainly
>funny. So there...
>
>Dan

Ron B.
F4Fguy

Dan:

I'm not certain of that.

Ron B.

P.S.

Re the "other" apps; I think you'd have a real problem with even the best epoxies with gasoline fuel and/or anything over 1.5 or 2 C.I.D. Those guys are getting back to the temps Jennings inferred from his work. We only get away with it because we're dumping heat very rapidly,and we don't make much in the first place.

>Dan:
>
>I'm not certain of that.
>
>Ron B.
>
>P.S.
>
>Re the "other" apps; I think you'd have a real problem with
>even the best epoxies with gasoline fuel and/or anything
>over 1.5 or 2 C.I.D. Those guys are getting back to the
>temps Jennings inferred from his work. We only get away with
>it because we're dumping heat very rapidly,and we don't make
>much in the first place.

Ron,

Good point for certain, but packaging, as you know, is a very real issue for the motorcycle guys, although less so for karts. And at least in the early years when pipe development was on such a steep learning curve, it was just a lot easier to fab 'em out of sheet steel.

>>This subject seems to come up at our practice site fairly
>>frequently.
>>
>>Why are there no aluminum tuned pipes being offered for use
>>in CL Stunt?
>>
>>Yes, they would be heavier, but surely this is not a deal
>>killer.
>>
>
>
>I thought all the tuned pipes were aluminum. I bought 2
>tuned pipes and they are both aluminum.
>
>Something interesting I have noticed about a tuned pipe, if
>you build your own tuned pipe out of brass for example then
>build another one identical to the first one only this time
>make it out of a differrent metal it will "NOT WORK." Even
>if the 2nd tuned pipe is 100% identical to the 1st tuned
>pipe it will not work if it is made out of a different
>metal. If you build the 1st tuned pipe out of steel then
>built a 2nd and 3rd pipe out of aluminum and brass they will
>not work.
>If you build the 1st tuned pipe out of aluminum then built a
>2nd and 3rd pipe out of steel and brass they will not work.

No, that's not correct. They might require different lengths, since the temperature of the exhaust, and thus the speed of sound, might be different. But they will work with proper tuning.

>After doing so research I learned it has to do with the heat
>radiation rate of each metal is different.

Correct, which leads to the situation described above.

This reminded me of something that Gary posted a long time ago, so I went looking for it:

http://www.clstunt.com/cgi-bin/dcforum/dcboard.cgi?az=read_count&om=8910&forum=DCForumID1#3

and

http://www.clstunt.com/cgi-bin/dcforum/dcboard.cgi?az=read_count&om=6691&forum=DCForumID1#15

Hmmm...

Neat thread. I almost understand what y'all are talking about as well as I almost understood Wild Bill's series on CLPA Aerodynamics in AAM in the mid-60s.

A summation might read:

"There is a set of precise formulae which will get you into the ballpark; from there on - - Cut to shape; beat to fit; paint to match!"

And a refreshing level of civility, even in disagreement . . .

LAST EDITED ON Oct-18-04 AT 02:44 PM (CDT)
 
>This reminded me of something that Gary posted a long time ago, so I >went looking for it:
>http://www.clstunt.com/cgi-bin/dcforum/dcboard.cgi?>az=read_count&om=8910&forum=DCForumID1#3

>and

>http://www.clstunt.com/cgi-bin/dcforum/dcboard.cgi?>az=read_count&om=6691&forum=DCForumID1#15

>Hmmm...

I'm fixin' to put my Two-stroke Tuner's Handbook up on eBay.

Before I do, however, I would like it noted that if I were the sort of generous person I claim to be, it would simply be given to the most deserving individual I can think of.

The problem here is that I cannot for the life of me figure out whether the "most deserving" is Gary or Len. And ripping the handbook in half is not an option, as both already have approximately half the story when it comes to tuned pipes.

Just being ornery today,

Dan

...insert big wads of smiley-face icons, your choice as to message being sent...

Sorry to ruin your day, Dan, but you've lost your chance to make a killing on eBay. A very readable, downloadable copy is available at http://edj.net/2stroke/jennings/ That's the link Tony posted a while ago. At that time the scan quality was pretty poor. I checked in there about a week ago and, lo and behold, there was an almost pristine copy, aside from a few measurements converted to metric in the margins.

Best, Hoovie

>>This reminded me of something that Gary posted a long time ago, so I >went looking for it:
>>http://www.clstunt.com/cgi-bin/dcforum/dcboard.cgi?>az=read_count&om=8910&forum=DCForumID1#3
>
>>and
>
>>http://www.clstunt.com/cgi-bin/dcforum/dcboard.cgi?>az=read_count&om=6691&forum=DCForumID1#15
>
>>Hmmm...
>
>
>
>I'm fixin' to put my Two-stroke Tuner's Handbook up on eBay.
>
>Before I do, however, I would like it noted that if I were
>the sort of generous person I claim to be, it would simply
>be given to the most deserving individual I can think of.
>
>The problem here is that I cannot for the life of me figure
>out whether the "most deserving" is Gary or Len. And ripping
>the handbook in half is not an option, as both already have
>approximately half the story when it comes to tuned pipes.
>
>Just being ornery today,
>
>Dan
>
>...insert big wads of smiley-face icons, your choice as to
>message being sent...
>

Ron B.
F4Fguy

The most important part of reading is comprehension.

Give your copy to me .Mine's getting dogeared.

I am a REAL newby when it comes to pipes...You could pass it on to me...I would take real good care of it. Just a thought.