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hydroforming an expansion chamber? tzr 125

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jordey
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PostPosted: 19:13 - 24 May 2013    Post subject: hydroforming an expansion chamber? tzr 125 Reply with quote

i have a tzr 125r 1993 project bike. the exhaust is scratched and dented and the mount isn't great on it, so was looking for a new exhaust. theres not many exhausts available for the bike, and if i wanted an aftermarket one i would have to buy new, which is expensive and they don't even look or sound good. i've seen videos of people hydroforming an expansion chamber and it doesn't look that difficult. this website also gives a fairly detailed how to:

http://www.eurospares.com/frame8.htm

i dont have alot of experience welding but have a mate who can help out if needs be. if anyones done this, how difficult was it to actually do it?
also, how would i know what size and shape to make the cutout?
and im assuming a different size/ shape expansion chamber would give a different sound and performance?
if i went down this route for an expansion chamber, what end can could i make fit? the original exhaust still works so im not in a mad rush to get a new one sorted quickly
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Copycat73
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PostPosted: 20:24 - 24 May 2013    Post subject: Reply with quote

your opening a can of worms here...
get your mate to weld up your old one...
then buy some solvol autosol chrome cleaner and polish it up...
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jordey
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PostPosted: 21:18 - 24 May 2013    Post subject: Reply with quote

Copycat73 wrote:
your opening a can of worms here...
get your mate to weld up your old one...
then buy some solvol autosol chrome cleaner and polish it up...


what would be the problem with it?

the exhaust on it now is fine in terms of it works. it just looks horrid and doesn't sound very good. end can is scratched and dented, expansion chamber is dented, and it's been painted really badly so just all round looks sh*t, which is why i'm looking for a new exhaust. since it still works though it'll do for now so i have time to look for a new exhaust/ make one
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Zen Dog
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PostPosted: 21:19 - 24 May 2013    Post subject: Reply with quote

I think the problem is less the hydroforming (although that is a problem), and more the extensive mathmatics and in-depth knowledge involved in designing a 2-stroke pipe for a decent powercurve. Companies who make aftermarket pipes put in a lot of development time, and they don't always get it right.

You're also probably going to need dyno time to setup the bike properly for the pipe afterwards. Get this months Practical Sportsbike, they have an article about a guy trying to sort out a custom pipe for his RGV250 (with lots of professional help).

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jordey
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PostPosted: 21:25 - 24 May 2013    Post subject: Reply with quote

Zen Dog wrote:
I think the problem is less the hydroforming (although that is a problem), and more the extensive mathmatics and in-depth knowledge involved in designing a 2-stroke pipe for a decent powercurve. Companies who make aftermarket pipes put in a lot of development time, and they don't always get it right.

You're also probably going to need dyno time to setup the bike properly for the pipe afterwards. Get this months Practical Sportsbike, they have an article about a guy trying to sort out a custom pipe for his RGV250 (with lots of professional help).

Zen Dog


yeah this was the biggest problem i could think of, getting the right shape/ size
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jordey
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PostPosted: 00:25 - 25 May 2013    Post subject: Reply with quote

okay so was looking up about shape and size. i found this program that has good reviews for making expansion chamber sizes. it gives the option to print out the design to make cones out of paper so you can mock up a design. since you dont need this for hydroforming, i thought i could mock up the exhaust like this, then just flatten it which would give the shape/ size of the expansion chamber. i could then use this to cut out the two shapes out of sheet metal, but a bit bigger to allow it to be welded. would this work?
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bladerunner
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PostPosted: 01:17 - 25 May 2013    Post subject: Reply with quote

If you don't know the design behind a 2 stroke pipe then your wasting your time! Buy one. Google mick abbey tuning he will make one for you for not much£££ and as for hydro forming you'll need a pump and a tig welder for best results .... The hard part is the getting the header part of the pipe not to crease when you form it then you'll need a lathe to make the flange to mount it to the head and end can attachment. You'll be able to machine different diameter washers for the end can end to adjust the pressure in the pipe to get best results but having access to a dyno is the only way to tell what works and what does not.....oh and expect to make at least 10 different pipes UNTILL you can find one that works as well as you want if learning. A lot of time and money if you don't have the gear already!
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bladerunner
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PostPosted: 01:20 - 25 May 2013    Post subject: Reply with quote

Double post
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Last edited by bladerunner on 23:57 - 25 May 2013; edited 1 time in total
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bladerunner
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PostPosted: 01:41 - 25 May 2013    Post subject: Reply with quote

Doh! Double post!
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Last edited by bladerunner on 23:59 - 25 May 2013; edited 1 time in total
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Walloper
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PostPosted: 09:56 - 25 May 2013    Post subject: Reply with quote

Hydroforming a one-off exhaust?

The equipment to complete the hydroforming will cost you as much or more than a custom pipe from a supplier/OEM.

As far as the technique is concerned, it is just a method of fabrication. It is rather specialised and requires a lot of experience to get the correct result.
Chopping out some plate from a 'known' template and welding it together will be much easier and probably 10% of the cost after tooling is factored into the plan.

Hydroforming is also fraut with dangerous high pressure risks:

Explosion like the same energy released by a lump of dynamite.
Hypodermic injection. Lethal/Life changing injury.

Lots of other evil stuff.

Walk away from this website http://www.eurospares.com/graphics/hydroform/hydroform001a.jpg

Smile
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jordey
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PostPosted: 12:55 - 25 May 2013    Post subject: Reply with quote

Walloper wrote:
Hydroforming a one-off exhaust?

The equipment to complete the hydroforming will cost you as much or more than a custom pipe from a supplier/OEM.

As far as the technique is concerned, it is just a method of fabrication. It is rather specialised and requires a lot of experience to get the correct result.
Chopping out some plate from a 'known' template and welding it together will be much easier and probably 10% of the cost after tooling is factored into the plan.

Hydroforming is also fraut with dangerous high pressure risks:

Explosion like the same energy released by a lump of dynamite.
Hypodermic injection. Lethal/Life changing injury.

Lots of other evil stuff.

Walk away from this website http://www.eurospares.com/graphics/hydroform/hydroform001a.jpg

Smile


i don't really need to spend much on equipment tbh. i've already got a welder so dont need to buy that. as for the pump i'm gonna look around to see if i can borrow one off of a mate or rent one, so shouldn't cost me nearly as much as a stock pipe.

as for fabrication i was planning on using a template, but they're a little difficult to find. i could base the dimensions off of the stock exhaust if needs be. or i could use that program to give me the shape/ dimensions.

that website also says there isn't really any risk of explosion as the water will only leak out if there is a hole, as there would be no air/ gas in chamber. theres notes on this at the bottom of the how to.
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Walloper
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PostPosted: 13:30 - 25 May 2013    Post subject: Reply with quote

jordey wrote:
Walloper wrote:
Hydroforming a one-off exhaust?

The equipment to complete the hydroforming will cost you as much or more than a custom pipe from a supplier/OEM.

As far as the technique is concerned, it is just a method of fabrication. It is rather specialised and requires a lot of experience to get the correct result.
Chopping out some plate from a 'known' template and welding it together will be much easier and probably 10% of the cost after tooling is factored into the plan.

Hydroforming is also fraut with dangerous high pressure risks:

Explosion like the same energy released by a lump of dynamite.
Hypodermic injection. Lethal/Life changing injury.

Lots of other evil stuff.

Walk away from this website http://www.eurospares.com/graphics/hydroform/hydroform001a.jpg

Smile


i don't really need to spend much on equipment tbh. i've already got a welder so dont need to buy that. as for the pump i'm gonna look around to see if i can borrow one off of a mate or rent one, so shouldn't cost me nearly as much as a stock pipe.

as for fabrication i was planning on using a template, but they're a little difficult to find. i could base the dimensions off of the stock exhaust if needs be. or i could use that program to give me the shape/ dimensions.

that website also says there isn't really any risk of explosion as the water will only leak out if there is a hole, as there would be no air/ gas in chamber. theres notes on this at the bottom of the how to.


This technique relies on both sheets to be cut to a pre-determined profile and welded together at the edges.

Then the 'balloon' is inflated with water. And hydraulic force forms a pipe which will/conform to the tempate.

If you miss-cut then the shape will suffer. And you will need to select a suitable material. SS comes in several grades FYI.

If you can be arsed go for it. Your welding will have to be good. Smile
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jordey
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PostPosted: 14:31 - 25 May 2013    Post subject: Reply with quote

yeah im familiar with the process, and it doesnt seem too difficult or time consuming which is why im asking, as i wouldn't of thought it would be that easy to make an exhaust. i'll be using SS instead of ali which ive seen some people used, not sure of the grade yet.

as i said the original exhaust still works so it doesn't really matter if i get this wrong as i've got a backup. if iw as hydroforming, what should i do about an end can? could make a cone but think they look horrid
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Drake
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PostPosted: 15:42 - 25 May 2013    Post subject: Reply with quote

the fact your asking shows you wont make a usable exhaust, just buy one.
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Walloper
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PostPosted: 16:34 - 25 May 2013    Post subject: Reply with quote

If you don't know already, the expansion part of a 2 stroke petrol engine exhaust does more than control sound/noise.
It is designed to, more importantly, act like an exhaust valve and block the fresh air-fuel mixture 'blowing' through the engine at the start of the compression stroke. It employs a bit of science and a lot of witchcraft. The speed of the gas flow, temperature of the gas and the pressure of the gas all contribute to the back-pressure needed to 'seal' the exhaust port. If you get the design wrong you can easily down-rate the engine performance. Which will lose you several man-points on here. Razz

The idea looks simple but I'll wager 'a pound to a bucket of shite' there will be many 'prototypes' before the final product is born. Smile

If yer keen to have a go then fcuk it. Knock yer sel out. Smile

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jordey
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PostPosted: 17:49 - 25 May 2013    Post subject: Reply with quote

yeah i understand the basics of how a 2t exhaust works, but was wondering how it can be 'tweeked' to affect exhaust note. e.g. if i was using a stock pipe as a template, what steepness of the cones or length of pipe (not including expansion chamber) could be tweeked to affects performance/ sound.

on a somewhat related note, on the original exhaust, what affect would shortening the pipe between the expansion chamber and end can have on general performance?
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jordey
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PostPosted: 18:11 - 25 May 2013    Post subject: Reply with quote

Drake wrote:
the fact your asking shows you wont make a usable exhaust, just buy one.


the only exhaust i can buy for my bike is a used stock one. if i want an aftermarket one i would have to get one from a different model and make it fit, and a decent system would be around £300. so not alot of options for exhausts. the reason im asking here is because there isnt much information online on my bike as its fairly old now (1993) and there arent many about, so i cant simply find a template like you can with other bikes.
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Zen Dog
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PostPosted: 18:25 - 25 May 2013    Post subject: Reply with quote

I don't know about tweaking for different sounds, 2 strokes always sound awesome to me! Lots of OEM pipes are dual-skinned to make them quieter though I think, and aftermarket ones only single-skinned. You should probably bear that in mind (that the internal and external profile will be different) if you use your original pipe as a template (which is probably your best option to end up with something useable).

Apparently the pipe length after the expansion chamber "largely determines the overall exhaust-system back pressure". More length, and more pressure is good for power, but also increases heat, which can be a problem. So to answer your question, shortening the pipe will give you less power.

EDIT - I'd get the used stock one, or look at repairing your existing one, if the ultimate aim is to ride the bike. On the other hand, if the ultimate aim is to set yourself an engineering project, go nuts, just bear in mind that its likely to cost a fair bit in time, effort and money to get something useable.

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Copycat73
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PostPosted: 18:39 - 25 May 2013    Post subject: Reply with quote

jordey wrote:


what would be the problem with it?


there is a lot of work involved... actually makin the exhaust will be the easy bit... it will end up costin more time money and energy than its worth.....

but please don`t take my word for it...
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Vincent
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PostPosted: 19:20 - 25 May 2013    Post subject: Re: hydroforming an expansion chamber? tzr 125 Reply with quote

jordey wrote:
i've seen videos of people hydroforming an expansion chamber and it doesn't look that difficult.


The person doing it may have made it look easy..........but it's not. First time out, it would probably take as many as 20 attempts to get a usable pipe. That's not to say it's not worth having a go - I'd be careful though Exclamation
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jordey
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PostPosted: 20:08 - 25 May 2013    Post subject: Reply with quote

Zen Dog wrote:
I don't know about tweaking for different sounds, 2 strokes always sound awesome to me! Lots of OEM pipes are dual-skinned to make them quieter though I think, and aftermarket ones only single-skinned. You should probably bear that in mind (that the internal and external profile will be different) if you use your original pipe as a template (which is probably your best option to end up with something useable).

Apparently the pipe length after the expansion chamber "largely determines the overall exhaust-system back pressure". More length, and more pressure is good for power, but also increases heat, which can be a problem. So to answer your question, shortening the pipe will give you less power.

EDIT - I'd get the used stock one, or look at repairing your existing one, if the ultimate aim is to ride the bike. On the other hand, if the ultimate aim is to set yourself an engineering project, go nuts, just bear in mind that its likely to cost a fair bit in time, effort and money to get something useable.

Zen Dog


yeah the only thing about 2 strokes i dont like is they're really high pitched, and makes it sound like a moped. if i could get a nicer exhaust note it would be nice but isn't that important

as for the profile, the end product will likely be slightly smaller than the stock exhaust as the stock will be a little more spherical so should have a slightly largely volume, so if i go by the external profile it should give a fairly close size internal profile to the original once expanded, if that makes sense. i could also make the template a couple mm's smaller all round to compensate.

yeah i read the pipe length affects power which is why i didnt do it. do you know how long i could make the pipe? as i originally wanted it to be closer to the body (like an r125), so could curve some pipe round to make it exit before the rear wheel, but not sure how long i could make the pipe if heat is an issue.

i will be using the stock one for the time being, its on the bike and works, but im looking for a nicer replacement, which isnt as simple as just buying one!
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Pete.
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PostPosted: 20:45 - 25 May 2013    Post subject: Reply with quote

Don't be told you can't do something, it'll fail, you'll blow your bike up, it's not worth it etc. That's what I was told when I announced I was going to build my own turbo setup and it just made me more determined.

You can make a hand-powered high-pressure water/oil pump with a few bits of metal and a long tube for a handle, if you've got a lathe.

I'd buy a cheapo bottle jack, remove the piston and weld a cap over the hole with a fitting for some hydraulic tube. A tube into the filler hole to a larger reservoir and you have your pump. Or get a portapower pump off eBay for £50.

Got a tig welder? Just buy a sheet of 20 gauge steel, a pair of tinsnips and have at it. Cut some test profiles to get your method working and you're set.
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bladerunner
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PostPosted: 00:14 - 26 May 2013    Post subject: Reply with quote

Hydroforming is not dangerous as said earlier. Your using water not dynamite...and unlike compressed gas it won't explode on you....worst case is you spring a leak! And not much of one either as it's a liquid as soon as it leaks you lose pressure and that's it. A good starting point for a design is a TZ spec 125 or 250 as it will work on the tzr. Make the tuned length maybe 50mm longer to start with to move the power a bit lower down the rev range and see what you think. You'll learn a skill if you have the gear and keep at it. After you've got the hydro formed shape you'll have to cut it and reeled to route it to fit the bike. This is best done by cutting the header into sections that are wedge shaped...turn them over 180 degrees or whatever is required and re weld.....that way you get the bend and don't alter the tuned length by much...say 2mm shorter per part....ie thickness of your hacksaw blade x 2. It is worth doing just to learn but you will be in the shed for a good few late nights!
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Walloper
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PostPosted: 07:00 - 26 May 2013    Post subject: Reply with quote

bladerunner wrote:
Hydroforming is not dangerous as said earlier. Your using water not dynamite...and unlike compressed gas it won't explode on you....worst case is you spring a leak!


You think working with high pressure fluid is not dangerous?


You speak to HSE about working with high pressure fluid and see if they agree. I believe the guys who visit incidents where high pressure fluid has 'leaked' out will be able to advise you.


High pressure anything is only safe if you know what you are working with and normally would require some experience/competence.

Filling any chamber with fluid (hydraulic) will usually mean air has also to be purged. If the trapped air is not purged and the work piece fails then for sure you can have the same effect as a lump of dynamite exploding.

I work with high pressure shit for a living.

I personally wouldn't faph about with such a project as for a one-off it seems like re-inventing the wheel.

A bloke was killed last year when he was trying to make a BBQ from an old 45 Gal oil drum at his brothers house. Probably ignited some hydrocarbon which was still in the old drum but this is an example of how shit goes sadly wrong when folk don't understand what dangers are present.

http://www.dailymail.co.uk/news/article-2180244/Man-48-killed-explosion-sparked-sawed-oil-drum-half-make-DIY-BBQ.html

This happens almost regularly. Because people are ignorant they do not properly assess dangers. I know cutting an oil drum is fraut with hazards but mitigate the hazards by following approved procedures.


So don't casually diss a safety warning. That's Darwinism at it's Elemental best. Smile

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Vincent
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PostPosted: 11:39 - 26 May 2013    Post subject: Reply with quote

I'm no expert on them but two things I do know about expansion chambers:-

1/ the fatter the chamber part, the better acceleration over top end power. So, a fat pipe will make more power low down and better for acceleration, a skinny pipe will give you more top end power and give you a "screamer".

2/ The downpipe needs to be conical.

While still crucial, it's not so much the back-pressure that will give you more power by helping to stop unburnt fuel escaping the cylinder too easily and at the wrong time, as the resonance made by the exhaust gasses themselves.
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