Tuned Pipes

[Four Paws]

Anyone want to share a little theory and offer up some tips for us do-it-yourselfers to take a stab at building our own pipes? I know it is a black-art, based on mathematics and years of experience in regards to what works and what doesn't. I would like to give it a try but need some direction and some guidelines as to where I need to start. Mind you all, I am not trying to take the market by storm or steal any saw builder's clientelle - your help and advice is appreciated.

 

[timbrjackrussel]

Try to get a copy of Two-Stroke Tuner's Handbook By Gordon Jennings from H.P.Books.I saw it for down load somewhere.Try a search of this site or Google.

 

[timbrjackrussel]

Two Stroke Tuner's Handbook

http://edj.net/2stroke/jennings/ Try this link

 

[Four Paws]

Thanks, that is surely a great start!

 

[Freakingstang]

try this link for some fun....

Turn your Java on!

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

-Steve

 

[Four Paws]

Bad to the bone! I'll be in no time!

 

[RaisedByWolves]

Heres an idea I hit on working with R/C race trucks.


Use copper pipe to make your prototype pipe and to go through your testing stages.

Its malleable and easily worked, and can be quickly soldered up into new shapes, and simply unsoldered and the shape changed.


Large pieces of copper pipe can be had from plumbers for cheap if not free. They save them for scrap but if you tell them what you plan on doing they will sometimes be amazed and just start handing this stuff over.

 

[timberwolf]

The Java pipe software produces poor results, I tried it a couple times and it was a big waste of time. Jennings material will get you there but the math is a lot of work.

Soldering coper likely won't work, the temp of the pipe on gas will be well above the melting point of regular plumbing solder. You might get away with it with alky as long as your not adding much nitro.

 

[RaisedByWolves]

Youve tried this?




Ive run 20-40% nitro with no problems other than at the exhaust port area.


Someone who is ingenious enough to make their own pipe will figure out to make the header out of steel (vibration is the killer here) and the actual pipe out of copper.


The pipe its self wont get that hot.......

 

[timberwolf]

If your actually going to race with it the weight of the copper is also a problem, making changeovers with a couple pounds of metal off the side of the saw causes problems.

Copper, Sure it can be done, but not the best idea, esp if you were going to run it on gas which most people would, at least to start. 22-24 ga sheet steel is a much better bet.

TIG and maybe torch welding as a second in the hands of a good welder are likely the best. Time consuming though.

I like MIG (On gas not a MIG with flux core wire), fast clean, Won't make the welds as pretty as TIG, but a bit of grinder work and it can look quite good. Have had no problems with cracking.

 

[Four Paws]

The Java pipe software produces poor results, I tried it a couple times and it was a big waste of time. Jennings material will get you there but the math is a lot of work.

What did you find were the major points of error with the software? I read the entire section of Jennings book regarding expansion chambers - seems like he gives a good general baseline, and that most fine tuning is by trial and error.

 

[timberwolf]

Ended up with incorrect tuned length, belly too small, and reflector cone too shallow.

One pipe I made with this was only a bit faster than just a muffler, the other was slower than on muffler.

If the pipe is too long it will suck some of the fresh charge out of the jug and not get it stuffed back in before the port closes (net loss).

From what I have found some fine tuning will be required no matter what, the system is too dynamic to have it calculated to that degree of precision unless you work for NASA. Just changes in the the air temp, humidity, fuel, oil, jetting, chain, load on the saw... will all make changes to the exhaust temp, this will in turn change the the charicheristics of the pipe which will change the charicteristics of the motor output which again changes RPM and exhaust temp and you enter a vicious circle.

 

[RaisedByWolves]

If your actually going to race with it the weight of the copper is also a problem, making changeovers with a couple pounds of metal off the side of the saw causes problems.

AHem.....:bang:

Use copper pipe to make your prototype pipe and to go through your testing stages.

.

 

[timberwolf]

If your set on that, great it works for you.

But I find it easy enough to cut a steel pipe and re-weld it shorter or longer as required. Adding a pipe clamp and trobone slide works well too to fine tune the pipe. The when it is done there is no need to build the final version.

Might be worth keeping in the back of the mind that steel and copper have very different heat reflectivity and transfer properties, when you fab up a steel pipe based on a copper prototype you may be introducing a new variable. Even changing the thickness and mass of the pipe can have influences. For racing the pipe goes from cold to hot in just a few seconds, what that pipe weighs and how fast it heats up makes a difference. Ever feel a pipe start to die on the third cut?

 

[Chopwood]

Ever feel a pipe start to die on the third cut?

No:hmm3grin2orange:

 

[timberwolf]

Andy, I dont imagine the pipe on your 3120 CV was built by trial and error. Man that is a sweat saw.

 

[RaisedByWolves]

I have seen the light!

I dont race saws, and I dont think you evar raced R/c trucks.


The reason our outlook different is that you can use the calculations as a guide more than we could. And also there is the issue of us having to be able to fab/make parts in the bed of the truck miles from home.

See, what we would do is run a track (assuming we hadent raced there before) and would get our setup as fast and consistent as possable using a off the shelf pipe, gearing, tires, springs etc.


Once we had this nailed we would run the track in twos or threes and find where you could pass and could not, this would help us find a strategy. Once we had this worked out we would break out the torches and home made pipes and start to tinker.

If the track had a long wide straight away or two we could assume to run a pipe tuned more twords the top end (30-35k), where most of those high strung lil buggers are tuned to run.

IF, however the track was tight and twisty, or had the start/finish line after a tight section we could now play with our power curve to have the truck develope monster low end rpms(15-25k) witch would allow it to literally squirt out of the turns when the other trucks had mostly fallen off the pipe.


Given 4-5 turns we could easily catch trucks that had us by 15-25 lengths going down the straights. As long as we could keep the front wheels on the ground untill we were done steering.


Without being able to customize our pipes at the track we would be stuck with the same old setups and tricks everyone else had. For the final versions of the pipe we would use copper roof flashing and paint them with high temp aluminum paint as to make them look average.

The big Trick at the tracks was for people to go around and see what others were running as a baseline setup.

People who didnt race with us regurarly would come around and copy our setups after seeing us in practise and their trucks would just bomb on the track.



I guess with the trucks you only had to be better than the pack over 60% of the track, where as with the saws you have to be on the money 100%