another home made pipe

Clotho,

That IWT racing freeware is fascinating to sit and play with plugging in figures and learning how the software calculates the physical characteristics of the motor to do that with.

Anyone wishing to "understand" the workings of a chamber need only to look at the post "Expansion Chambers" in the Classic Category and watch the animated chamber as it works, download the free IWT racing program zip file, and actually have a torn down motor they are going to use to get the crank journal to piston pin centers measurement, piston ports measurements, and exhaust angle calculations etc to plug into the software before pressing the "calculate" button. The software will plot the diameters and lengths on a chamber profile laid out straight for you and it's printable. From this, patterns can be made on paper, and transfered to .040 sheet metal and formed into cones in a slip roller. Then those can be "nibbled or notched" to fit nicely on a frame before final welding.

My present thoughts on this would be to take the truncated conical portion of a finished pipe and make a stamping die to stamp out inside and outside pieces. Then join them and asembel this in jig for final welding. For something this small it would likely be the more expeditious route. The pipe could be for one like Norm's which goes below the bike or another which would go up like a TT pipe. With the stamping or pressing dies made the impressions could be wholesaled to buyers like Jemma who would like to have their own cottage industry where they could purchase raw pre bent tubing and stampings to assemble and custom finish for resale.

Regretably I don't yet have a 49cc in frame motor or the specs from one I need to design with. I would be inclined to build "torque tubes" for these small motors.

I downloaded the software and have played with it. It is fun to see how it all works down to a final shape.

If I had the correct numbers to plug in I would probably work from the pattern and do much like Norman here did. I want the pipe to fit a specific frame tightly so there would be lots of tweaking to get it to fit. I see Normans work here as inspiration.



I'm not interested in producing anything en masse atm. I just want a nice looking pipe for my bike. I have been playing with an expansion chamber on a new project bike but it is an adaptation of a pocketbike pipe and I know that there is much room for improvement. I think Normans pipe here fits much better than my own. Also, his looks to be pretty decent size wise from the various pipes I have seen.

Thank you very much for posting the link to the software eDJ! Also thank you to Norman for posting these pics of your fine pipe!

Now about those numbers needed to plug into the software. Does anyone have a motor apart that could supply some measurements? Hopefully one of the 69cc (real displacement) variety? eDJ mentioned:

a) crank journal to piston pin centers measurement
b) piston ports measurements,
c) exhaust angle calculations

Norman, how about selling it like the car guys do for custom headers? Sell it in 3 pieces, flange & headpipe, expansion chamber, & stinger, with maybe a short 90 degree elbow and some straight pipe. Then customer fits it up and has it welded. Some people want them high, I would like mine low, Just give us parts and pieces and we'll make it fit. Walter F.

Norman, here's a simple enough idea for you that could help walter and some of the others here too.

If the paper paterns you have could be set up as .jpb or .bmp files, you could
calculate the cones for the 49cc thru the other common motors to assemble an upper routed or lower routed finished chamber. After you've tested them and find the response an improvement over the muffler then the paper patterns in the finished form could be emailed as an attachment to those wanting to purchase them, have a local sheet metal shop roll and weld them together for them and a tubing shop bend the other tubing so they could do the final fitting and marking to have the tube brazed/welded and basically finish it themselves.

So with the R&D limited to six or eight chambers people could purchase from a small web site with a USPS money order and recieve an email with the printable files. (assuming that no one cone would lay out flat above 8 1/2 X 14....or the tubing similarly)

It would just depend on whether you want to design single, dual, or tri stage
diffuser chambers. (and which of those would be the most worthwhile effort)
Those wanting to custom build these for others could invest in a small slip roller and light brazing/welding set up and purchase the plans and make master templates from them. (knowing them to have been built and proven
by someone they know and respect) Local sheet metal shops could cut the blank sizes at .040 that they need for them in small lotts. I believe Harbor Freight and some others sell Chinese made shop tools for cheap for doing this now.

So far I've not found a cheap rolling tool over $400.00 is the cheapest and rolling the tubes and cones is work when doing it by hand. I've been getting a little faster though learning some tricks as I go. If you want to figure out the sizes for a pipe and I can see if I can make it I haven't messed with the down load for the pipe I seem to have computer problems sometimes when I try to download those types of things. More likely than not is the problem lies between the chair and the keyboard for me.
I may try it soon though I need to get my gas bottles exchanged and some more metal and have another go at a pipe this is getting habit forming. I'm using hood skins from an auto body shop the metal is around 0.030 thick which is plenty thick enough and the price is right all I have to do is haul it off. cutting the metal is easy with air shears and fine cutting with hand shears or a cutoff wheel. gas welding isn't too hard but you have to be careful not to burn through and fitting the parts is very important so you don't blow holes when welding it up. I been wondering if a wire feed machine would work better Ilikeabikea has one but I haven't played with it enough to be any good with it people say they are easy to use but everytime I've played with it it looked like a mud dobber had been at work.
Norman

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Norman, I download to my jump drives at the public library when using their computers & high speed LAN. Then install from it when I get home. I'll do that with these soon as I get to the Library.

But the IWT software took some playing around with for me as I don't have an in frame motor (torn down much less) to take measurements from. So, I just dreamed things up. My Tanaka isn't a likely candidate for an expansion chamber unless the 33cc chamber can be less than
36 inches long and mount to the right fork somehow.

Another software is here, and takes about 10 seconds to download on dial up:

The Expansion Chamber Design Software

For $40 dollars Build and Click.com has their 2 Stroke Wizard Expansion Chamber Design Software. 30cc and up, multi fuel, Win 98 and up. (If any of a group would purchase it together to use) I didn't see a trial but there may be one.

Here is a Free Java Applet Chamber Design ap that requires Java 1.4 (says it won't run on the old windows VM) I've had it up and it has loads of things going for it. Takes a few minutes to load but looks interesting. It's reviewer says this.

JavaPipe: Tuned Pipe Designer

It also allows you to export a .dxf file for the blanks to make the cones and stright sections from. The file can be used by many CAD softwares.

You can slide each value and see what part of the pipe they change. You can also type in specific values or values that are beyond the range of the slide.

SteelSnakes is a Free expansion tube design software. Look for it half way down the page here: (lottsa neat stuff for the math nuts here)

The Archive

Harbor Freight has this 12" x 20 gage slip roller for $150. If none of the cones are over 12" long.

Harbor Freight Tools - Quality Tools at the Lowest Prices

Their 90 amp flux wire feed/non gas welder is $129 but I've seen it on sale in the store for $99.

Harbor Freight Tools - Quality Tools at the Lowest Prices

But somewhere around $300 bucks and some free software could put a person who wanted to, making custom chambers that would sell for $75 bucks easily enough. A few chambers would net a breakeven fairly soon. If the motorbicycling trend continues to grow given gas prices....well those here doing this would be aboard as vendors already.

EDJ
Do you have a item number for the slip roller from harbor freight? I went into the store about 1 month ago to buy one but what it turned out to be was a panel roller that made flanged edges or raised ridges on a panel and it did not roll panels into cylinders I was bummed it was on sale for $75.00.
If you have a 33cc engine get the measurements for making a chamber and the way you want to make it look I'd like to see if the program will make a good chamber I might be inclined to knock one out for you just to see if it will work. I'll need a exhaust gasket cut to fit your exhaust exactly so I will be able to make a mounting flange.
You get the measurements and draw the shape of how you want the pipe to look along with mounting points etc and lets see what kind of an abortion I can make. What ya think?
Norman

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Thanks Norman, I'll look for Harbors Freight's # and I was thinking about Lindsay Publications too as I believe they offer plansets to build them inexpensively. Could get something really nice outa that.

When I get a few minutes I'll pull the motor off my bike and get the ABS plastic shroud off it. I know I'd have to cut a hole in the vents to use it with the shroud on it. But the previous owner had left a bolt out of the exhaust manafold and melted one of the grill loovers in half anyways. I could just run it without the shroud.....I think it's largely cosmetic.

It will be Sunday before I'm by Harbor again and I'll look to see if they still have that small slip roller on display.

I'll get back to you directly when I get back home. I'm on a clients computer now.....posting here by way of checking some mods I made for their OS.___________________________________

OK, I'm home now.

Harbor's slip roller is 12" and can roll 20 gage. I've seen the one you speak of too. (see the link at the bottom)

Here's ya some neat things to check out. Just gotta watch Harbor
for their sales.

Lindsay Books

Slip Roller Plans $9.95
by Dave Gingery's

Gingery's Slip Roll Machine


Aircraft Sheetmetal Working (reprint from 1940) $14.95
by Norcross & Quinn

Lindsay: Aircraft Sheetmetal Work


Build a pipe bender $8.95
by Vince Gingery

Gingery's Pipe Bending Machine


Aircraft Welding (1940 reprint) $15.95
by L S Elzea of Beachcraft

Lindsay: Aircraft Welding 1942


Build a Sheet Metal Brake from common metal $8.95
Plan No. 161 (seperate order request)

Gingery Series: Metalworking Shop from Scrap



Harbor Freight

12 inch by 20 gage Slip Roller # ITEM 36698-0VGA $149.95 ($99.95 sale)

Harbor Freight Tools - Quality Tools at the Lowest Prices

So, I'll get some beginning measurements tonight for a starting point.

Ok, here are some visualizing sketches for my proposed tube.

It would have one 90 degree radiused bend. the rest would be laid out straight. The positioning from the motor would come out at about 1 o'clock position aside the front wheel and sweep down to the 7 o'clock position. Total length would be best kept under 26" from the bend for this tube. It would provide for about 7 inches or so of road clearance at the exhaust tip. Support would be provided by standoffs mounted to the mid fork and the other brace mounting secured by the front axle nut which would extend out diagonally from the axle to the chamber tube and hinge for a few degrees. The top mounting point would be the the engine exhasut stack. The mid mount would be flexable since the motor is a friction drive and must move slightly to disengage from the tire which would require some shifting of the chamber.

For the sake of the photo to illustrate this proposal (I'm using the opposite side of the motor in this photo) I took some liberties yeah. So this is what I envision with a built in silencer.

Attached Thumbnails

   

I tried to find that slip roller but so far no luck.

Norman

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