Homemade expansion chamber

[motorbiek]

I'm trying to make an expansion chamber, cause I need one and why not. I'm not doing this the right way, to be honest. I just made some paper tests of a shape I thought looked good. I'm just sort of winging it, I figure I can make another shape chamber later if I want to. but I wanted a fairly large chamber with a gradual increase. I've been basic my shape on moped pipes I've had and the jaguar pipe, sort of. this is a work in progress.

I think I need the cut the back end (end is the side with bigger opening) off at about 3 inches in, then make a shorter cone that goes from that diameter to the stinger. the stinger will be 1/2 inch EMT. I think right now the tail end of the chamber would be too long.

I'm using what looks about like 20 gauge sheet metal. I've tacked it together, but I will braze the joints. too hard to weld the whole thing without burning through. I cut the shapes out with tin snips.

I'm definitely going to have to make my joints between the two cones smaller.

having fun so far!

 

[Frankenstein]

View attachment 75709 I'm trying to make an expansion chamber, cause I need one and why not. I'm not doing this the right way, to be honest. I just made some paper tests of a shape I thought looked good. I'm just sort of winging it, I figure I can make another shape chamber later if I want to. but I wanted a fairly large chamber with a gradual increase. I've been basic my shape on moped pipes I've had and the jaguar pipe, sort of. this is a work in progress.

I think I need the cut the back end (end is the side with bigger opening) off at about 3 inches in, then make a shorter cone that goes from that diameter to the stinger. the stinger will be 1/2 inch EMT. I think right now the tail end of the chamber would be too long.

I'm using what looks about like 20 gauge sheet metal. I've tacked it together, but I will braze the joints. too hard to weld the whole thing without burning through. I cut the shapes out with tin snips.

I'm definitely going to have to make my joints between the two cones smaller.

having fun so far!

Packing a large enough grain of dry sand into the pipe can help you weld a bit easier without burning through.

 

[LRSimons]

I think 1/2 conduit for the stinger might be too big. I think most pipes have one between 1/4 and 3/8. I used 3/8 when I made a pipe.

There is a free pipe design program that can help get the geometry right. Every angle will have an effect.


What head are you using? Something from a moped?

 

[motorbiek]

I think 1/2 conduit for the stinger might be too big. I think most pipes have one between 1/4 and 3/8. I used 3/8 when I made a pipe.

There is a free pipe design program that can help get the geometry right. Every angle will have an effect.


What head are you using? Something from a moped?

cool. the reason I would use a large diameter stinger is bc I am considering using the stock muffler. but I am now thinking it will probably be better to make my own as well.

the head is puch. hard to beat for $23
https://www.treatland.tv/Puch-50cc-Hi-compression-head-p/puch-hi-comp-head-50cc-old.htm

 

[gary55]

I read somewhere the stinger should be close to 65 % the diameter of the head pipe, and 12 times the length of it's ID So 1/2" ID by 6" long would be just about right for a 3/4 inch ID head pipe

 

[butre]

I think 1/2 conduit for the stinger might be too big. I think most pipes have one between 1/4 and 3/8. I used 3/8 when I made a pipe.

There is a free pipe design program that can help get the geometry right. Every angle will have an effect.


What head are you using? Something from a moped?

I've always used 7/8ths. 1/4 is absolutely tiny. open it up, your engine will thank you. 3/8ths is probably fine for a stock diameter header but if you've got anything even a little meaty on there then with anything smaller than half an inch will have your motor breathing about as easily as a pug.

 

[motorbiek]

ok. brazed this up tonight. working on header now hard to get the curve right. I'm not sure about the stinger, might put a different one on.

 

[Frankenstein]

Good luck I always hated brazing, mine looked like yours but with bigger gapping holes burnt in the walls. Sometimes it all just turned into a big pool of nothing but me screaming on the ground. Yeah it sucked.

Anyways you should practice your welding skills more, no point in holding skills out on yourself. I took up an old Russian arc welder and a quarter pallet of rods, never looked back at brazing ever again except for some special alloys.

If you can weld you can build anything.

 

[motorbiek]

Good luck I always hated brazing, mine looked like yours but with bigger gapping holes burnt in the walls. Sometimes it all just turned into a big pool of nothing but me screaming on the ground. Yeah it sucked.

Anyways you should practice your welding skills more, no point in holding skills out on yourself. I took up an old Russian arc welder and a quarter pallet of rods, never looked back at brazing ever again except for some special alloys.

If you can weld you can build anything.

I can weld. I just can't weld this 20 gauge stuff. it would be cool to be able to do both really well.

 

[Steve Best]

TIG is the answer if you can buy the gear.
Less heat distortion and works well with thin metal.
Need gas and a DC welder.