Hydroforming

[busastars]

hareng,

2T expansion theory. Lots of maths involved, never quite as simple as that though. Gorden Jennings & Graham Bell have writern very good books on 2T tuning which is what I always refer back to. I do have them save on my PC if anyone is intrested in 2T tuning & expansion design. Via email only as I dont want to get done distributing. I also got alot of manufactures designs saved, talk to a few builders quite oftern, its one area that has intrested me since I was a weeee lad.

BUT 2T expansion theory has moved on since then as you can now go onto mulitple stage defusers. think the KTM GP bike has a 4 or 5 stage defuser.

I understand the theory, I can deviate away from another design to suite my needs. My new design was done but a very good expansion designer who builds "Kenny Pipes" BUT was to my specs.

It can eather be called a 2 stage header pipe, or a 3 stage defuser pipe. Its beyond me this design as I can only go as far as 2 stage defuser tops.

 

[Drains]

This is good, apart from being, apparently, wrong.


An approximation of an expansion chamber in operation. It does a good job illustrating the positive portion of the exhaust pulse however there are several errors in this animation: The exhaust would not go all the way through the pipe in 1 cycle. Neither does it show the suction wave generated by the diverging section. The fresh mixture drawn into the header pipe can not go all the way down the header pipe.

Wikipedia strikes again!-No maths though, so it works for me.

 

[busastars]

All well and good to show how they work but it ends right at that point, on how they work. Design'ing one is a compleatly different story with alot of maths involved, however you can get some good software that will alow you to enter in the appropiate values and will give you a design from that.

Still software cannot account for real world and this is where some top designers are good, accounting for scavenging, head/sqwish & design ( another formular MSV), transfer timing, port angles, port hooking, inlet track area, volume & lenth, piston or crank ported, carb size & type.

All that will effect how the design should be but as I said you can get good results with using software. I have got a few software packages that work this out one of which is to Jennins formular, also got one that does MSV. They are avalible if you look hard enough on the net.

Typical proven example of exhaust design, has been extensivly dyno'ed on a low but accurate reading dyno and all RWHP

A bog standard RD350 motor was used:
Stock pipes 40rwhp
My design 47hp (ignition cut it at 9500, they were designed for 10,250)
Nikons, Jolly, Micron, etc, etc hit 47-50 rwhp (run of the Mill you can buy)
Kenny Pipes 54 rwhp on a stock motor with a big fat mid range. (Now thats the designer not software)

 

[hareng]

That Kenny is a big increase over a highly regarded Jolly Moto.
Sons after a Jolly Moto £390.
Think he has a GSXR stainless and carbon to flog some where.

 

[chunkolini]

Interesting stuff.
Did Walter kaden have any software aside form his boxers?
Who? the genius father of the modern stinkwheel.

We can lay the blame for every loud stinking expanied scooter at his feet.

Rocket engineer in WWII Germany, fiddled with poxy two strokes like MZ's then defected to Japan with all his deadful ideas.

There is a book, Stealing Speed, which I must get round to buying, in fact off to Amazon right now.

Chunko'.

 

[Drains]

Busa, to be honest, I never had a clue about expansions, other than that they made my RD250E a bit faster, a lot noisier, and did a good job of blowing holes in the top of the pistons when I hadn't set the timing right.

Until I saw that GIF above, I didn't know at all what they were for (or how they worked). I can imagine there is a shed load of complexity about getting the right amount of "bounce" and back pressure so the mixture gets nicely back onto the compression chamber, but still getting that jet of exhaust out the back, all allowing for revs, cc's, compression ratios etc etc. An increase of over 20% power has got to be a thing to go for! Impressive stuff.

 

[busastars]

Thanks for all the replies, dident think it would draw this much intrest.

I love bikes with a passion, over the past number of years ive tinkerd but the bikes have given me an area in which to learn more with regaurds to fabrication. Lots of projects I would like to see happen, I wanted to turbo my old Busa but at that stage funds and work went down hill big time, the two stroke thing is going back to most bikers routes and a cheaper way of tinkering compaired to four strokes.

One day I will build a turbo bike, (maybe a 2T turbo, lol) 2T turbos make crazy power even a busa turbos looks mild in comparison to some of those turbo 2T sledges.

Hopefully Sunday I can get the headers re'done and the second belly, ive cut them out rough so souldent take to long.

 

[pedrobedro]

How would a two stroke turbo work ? If the turbo needs the exhaust to drive the fan and the mixture is fed into the crank case before it is sucked into the combustion chamber how can you pressurise the charge ? The turbo will need a separate oil supply as well.

 

[busastars]

The turbo genuraly goes at the end of the chamber after the stingers, oil supply is done via a pump, seperate system.

2T Turbos are crazy,,,,,, just take a look at this vid:

http://www.youtube.com/watch?v=wvaoW3pz7Iw&feature=player_embedded

http://www.youtube.com/watch?v=WTeufdhZSak&feature=related

http://www.youtube.com/watch?v=E9S1qy__83o&feature=related

 

[pedrobedro]

That kind of power would be totally unusable on a bike without a 10 foot swing arm and the road would have to be as straight as a runway. The throttle is either on of off like a light switch.

 

[syborg]

oh my god...this brings back memorys. i had a tiny 50cc 2 stroke minibike and wanted a powerpipe, found a program called rocket something years ago,

after entering the rpm, the exhaust temps, the exhaust port height, and piston diameter it calculated the exhaust would need to be 3 meters long!!!!

i guess thats why all these new scooter pipes do about 3-4 laps under the bike to acheive the required length for that all important kick at about 25mph.


rather u than me mate...well done... hat off to ya...

peace

syborg

 

[busastars]

Not much of an update but I did redo the one of the headers and its almost bang on. Still need to trim all ends down and square off.

Also Wyn made me some dies / formers so I can hammer in and make sure the holes are 99.9% round as this will make it simple to weld after. Also now I can fit them in my lathe and turn the centers out so I can use them for upto four diameters, well more as they are tapered by about 10mm.

Just lacking in time and energy right now, should be able to compleate them soon'ish. Also Ive eatern up the 19mm rubber washers so going to order a pack of 50, that should last me a while and there only a few pound.

The new header with the center sections: (still need triming as I said)

How they should look roughly:

My Dies / Formers:

The waste, just cut and re'weld the pipes back on per section:

Templates so far, these should not change if all goes well:

 

[Shox Dr]

Looking good, fella

 

[mike os]

well impressed dude

 

[brookie456]

Bluddy 'ell, the Fred Dibnah of two-strokes...nice! Raced them years ago and even from an engineering upbringing to make your own expansion chambers is pretty damned special - well done with the hydroforming, looks pretty similar to the TZ,s of that time - my favourite race bike ever No power, but what a chassis

 

[chunkolini]

TZ's? two strokes? spawn of the devil.*
Whenever I see one I reckno you could just squeeze a bored out honda XBR500 motor in one, even the Aprilia 250's. Now that would be a bike.
* but this is beautiful shed engineering at it's best.

Chunko'.

 

[Woody.v8]

TZ's? two strokes? spawn of the devil.*
Whenever I see one I reckno you could just squeeze a bored out honda XBR500 motor in one, even the Aprilia 250's. Now that would be a bike.
* but this is beautiful shed engineering at it's best.

Chunko'.

XBR at 43hp and a screaming two smoke at 73 hp no competition!

 

[classic2cv]

Rocket engineer in WWII Germany, fiddled with poxy two strokes like MZ's then defected to Japan with all his deadful ideas.



Chunko'.

That was Ernst Degner

He defected from MZ and the East to race for Suzuki in the early 60s

I’ve always been a big Mz fan, last year we had a camping holiday in the Czech republic and visited the old Mz factory in Zschopau on the way back

the building is still there but Mz is no more

good luck your expansion chamber

there great fun to make and the results can be brilliant when you get it right

 

[hareng]

Just on the verge of ordering a JollyMoto for nipper, dare not attempt with my welding, here little birdies

 

[mike os]

go wash your mouth out chunko

some great 2 strokes...personally my fave was the RD500

OK utter rubbish as transport but great fun