Full Wave Carbon Pipe?

Frank Williams said in another thread:

"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."

My question is, why doesn't anyone make a "full wave" carbon pipe? Seems simple enough.

>My question is, why doesn't anyone make a "full wave" carbon
>pipe? Seems simple enough.

I have a bit of a problem with the terminology (full wave? - it's certainly not 1/4 wave, and its not 2 wave), but people *have* done this. I took a standard Billy pipe in which a baffle had come loose, and cut out the center section, and glued it back together. I found it to work a little too well, and the problem appeared to be that the tail cone angle was much too "flat" to provide enough RPM range to work. Frank's non-baffle pipes had *much* shallower tail cones, and that softens the response.

Frank gave me some of the dyno data for the multi-baffle/multi-reflecting-surface pipes, and I was somewhat amazed that we make it work at all. But I can see that some people, in fact, don't! But a full wavelength of reflections got to work better, even if there are several of them from different places, than the same thing on a fractional-wavelength pipe like the 20FP muffler, and that definitely does work with the right load.

Easy enough to do- get the sleeves from Aerospace Composites, or some such, some high-temp epoxy, and make tail cone mandrels of varying dimensions to tack on the the back of a defunct Billy pipe.

LAST EDITED ON Sep-30-04 AT 09:40 PM (CDT)
 
I don't know where to find the formula but there is one for cone legnth,angle,head pipe legnth,stinger legnth and diameter. This is a basic starting point for a two stroke engine but the real test is on the dyno.

Edit: I guess we could make a crude DYNO form a fishing scale.

>I don't know where to find the formula but there is one for
>cone legnth,angle,head pipe legnth,stinger legnth and
>diameter. This is a basic starting point for a two stroke
>engine but the real test is on the dyno.
>
>Edit: I guess we could make a crude DYNO form a fishing
>scale.

The Two-Stroke Tuner's Handbook is a pretty good resource. But I think our application is different enough that the rules of thumb for dimensions might not be so good.

I think, however, that to pick up the effects we are talking about - some of which are very subtle - you need a pretty good dyno. Since it's not about maximizing some parameter, but making the torque curve a particular shape, you need some very repeatable measurements.

Of course, the first step would be to take known good systems with significantly different characteristics, and test those in some realistic way on the ground, and see what makes them different. We can talk all we want about theory but right now, I don't think we have a very good idea at all what makes a good PA61 setup different from a good 40VF setup and a RO-Jett 61 setup in an engineering sense. . I know what I *think* the differences are, but that's different from having data showing it. I guess what I am getting at is we don't really know the goal.

I guess what I am getting at is we don't really know the goal.
>
> Brett

I've also seen many of Frank's pipe curves, in some cases the results really make you shake your head in dismay. As Ron pointed out in the other thread the shape of the pipe will effect the operations which means that we could set an engine exactly as Frank did and not be able to duplicate his results because we are using a different pipe.

I think that we know the goal it is the route through the maze of approaches we're trying to figure out.

My 0.02 cents worth.

>(Snip) I think that we know the goal.
>It is the route through the maze of
>approaches we're trying to figure out.
>
>My 0.02 cents worth.
>
>Carl

I am not sure we all even know the goal. Although there are a number of approaches and set-ups that may work, and some may even suit one person's style better than another, there are also a number of very wrong approaches. Some people who are using the pipe still haven't even figured out what it is there for. When you move the pipe in or out a bit, change the engine rpm faster or slower, change venturis, head shims, prop diameter and pitch, you can see what effect these all have on the set-up. Unfortunately most people do not have the time or care to take the time to test these. For them following certain patterns or copying someone else's approach may be best. (That's where charts come in and talking to people like Randy.)

However, I still heep hearing people talking about getting a boost in power from the pipe. That is not what we are seeking at all. Some talk about the backside of the curve. That would not be my approach at all. (These are two opposite approaches, by the way.) What we are trying to do is regulate while allowing the engine to deliver its power effectively in a stunt run. This still allows for differences in prop selection, both as to diameter and pitch, but will mean corresponding changes in pipe length as well as other parameters. Still, the pipes used for stunt are going to end up being different from those used for speed.

Speed engines will have the pipe set for one particular frequency, and will "come on" the pipe with a bang. That is something we are trying to avoid, but may be the result of using some of these other pipes designed for other purposes.

Ron B.
F4Fguy

Brett:

And you took me to task for saying some of the respondents didn't know how pipes work!!!!!??

As far as I know then ope pipe resonator (megaphone) is 1/2 wave resonator, while closed (reflexing) pipe is 1/4 wave resonator. Does not matter what (reflexing cone or any of baflless ) reflects the wave. You can have higher harmonic resonantion but physical effect is still the same.

And why baffles? It is much simpler to modify its position and reflexivity to get wanted properties then to make different templeates to make different back cones. And on other it is not so noisy.

btw Martin Hepperle has nice applet for pipes on:

http://www.mh-aerotools.de/airfoils/javapipe_de.htm