[Technique] Réalisations de Maarten JANSSENS

Maarten,


Could you tell us what grade of titanium alloy was used ?
Welded with neutral Argon gas ?


--
Stéphane

ttroncs a écrit:

Maarten,


Could you tell us what grade of titanium alloy was used ?
Welded with neutral Argon gas ?


--
Stéphane

I would have to check for the grade...

it's welded with 12L/min of "normal" argon from the outside and then there has been put something like 5L/min on the inside of the tubes. The tubes were sealed off with tape in wich we made a few small holes so the gas would flow through a bit.

Maarten, I don't know if Nelson wants to give away his secrets, but I guess I can ask anyway :)
Does he do anything special with preparing the tungsten for titanium?

I found not much problem to butt weld two pieces together, but welding on the spring-hooks I found it very difficult to get an accurate arc because of the very low current. So then I would often burn up the hook before getting a puddle on the sheet.
Many failures in practicing, I did one ok on the pipe but I'm not so confident to do more :-(

GrahamB a écrit:

Maarten, I don't know if Nelson wants to give away his secrets, but I guess I can ask anyway :)
Does he do anything special with preparing the tungsten for titanium?

I found not much problem to butt weld two pieces together, but welding on the spring-hooks I found it very difficult to get an accurate arc because of the very low current. So then I would often burn up the hook before getting a puddle on the sheet.
Many failures in practicing, I did one ok on the pipe but I'm not so confident to do more :-(

Hey Graham,

I'm not going to tell but you can always ask him yourself

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cheers!

p.s. He didn't weld it with low current...

GrahamB a écrit:

Maarten, I don't know if Nelson wants to give away his secrets, but I guess I can ask anyway :)
Does he do anything special with preparing the tungsten for titanium?
I found not much problem to butt weld two pieces together, but welding on the spring-hooks I found it very difficult to get an accurate arc because of the very low current. So then I would often burn up the hook before getting a puddle on the sheet.
Many failures in practicing, I did one ok on the pipe but I'm not so confident to do more :-(

Graham,

I'm not an expert welder at all, but experimented the same problem on a stainless steel exhaust.
Why not making it in two steps : the first one welding the spring hook ona small sheet of metal and the second one to weld the hook/sheet on the exhaust which easier ?

With this method, the difficult step won't cost you a huge amount of money if failed (just the cost of the small steel sheet and the hook) and the welding of the small sheet on the exhaust will be stronger.

No ?

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Stéphane

I also tried welding the edge of a small piece of 0.8mm Ti to a larger sheet, with the same problem. I maybe need some thicker material to try on, some is on its way. The exhaust itself is very rare and no longer made...

Funny, 30 years ago on steel I did it with oxy-acetylene no problem !

GrahamB a écrit:

I also tried welding the edge of a small piece of 0.8mm Ti to a larger sheet, with the same problem. I maybe need some thicker material to try on, some is on its way. The exhaust itself is very rare and no longer made...
Funny, 30 years ago on steel I did it with oxy-acetylene no problem !

Oxy-acetylene on steel is more tolerant than TIG on Titanium ... the reason why as a poor welder I prefer the oxy-acetylene method !

--
Stéphane

a "small" update:

I redesigned the exhaust to get the noise down and the ground clearance up (most important reason) It did cost power and it caused the silencer under the engine to explode because it had gotten too hot! The picture with me next to the bike I attached the (very) small silencer that was hanging next to the wheel under the engine so I could finish my day on croix. very loud but the power was back.

Making a small "corner" here (first picture) ment the front of the pipe went inwards on the right side and the silencer on the left side also went closer to the centre --> more ground clearance. The silencer was now pointing AGAINST the swin arm so I had to make a pipe that went past it.

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also made a new tacho face that is A LOT better to read than the standard ktm unit! It also has the red line in the middle on top as it should be.

OLD:
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NEW:

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The "problems" with the exhaust got me thinking about exhaust tuning.
I might have said it before but I'll do it again to be sure: The single titanium pipe gave me much better throttle-response and more mid-range power then the twin-megaphone setup. I just lost a little power at maximum revs but the bike was better to ride on track!

Adding the extra damper didn't change the way the bike rode but it just lost power over the entire rev-range.

After calculating the exhaust I found that I am using the correct diameters (that was calculated before).

first pipe: 48mm diameter for 67 cm

second pipe: 50 mm diameter for 81.5 cm

first silencer: 52 mm diameter for 30.5 cm

third pipe: 50 mm diameter for 31 cm

second silencer: 52 mm diameter for 22.5 cm

standard camshaft:
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ktm "rally" camshaft that I'm using now:
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Calculations also said the "tune" length should be 685.8 mm. For those that don't know: this means that the pipe itself needs to be a single tune length or this length multiplied with whole numbers (2x the length, 3x the length,...etc.) measured from the exhaust valve.

My exhaust pipe measures 148.5 cm from valve to first silencer. this is 2 x 74.5 cm or in other words: 11 cm to long! Then there is the first silencer (30.5 cm), the follow up pipe (34 cm) and the second silencer (23 cm).

I was wondering if having the exhaust coated (zircotec) would raise the gas velocity and thus have the same effect as a shorter pipe?!

Logic says it would have the wanted effect but we all know that motorcycles, tuning and logic don't like to work together  

what would the length of the third pipe have as an effect?

what do you guys think?!

all the pictures here: [Vous devez être inscrit et connecté pour voir ce lien]

kind regards,

Maarten "MJ-Works"

Thinking about the wise words of Frits: the idea of a constant speed of sound is a convenient fiction used to make a first approximation.
(The rest of these thoughts can't be blamed on Frits if they are wrong)
Partly this is becasue of heat loss through the pipe walls, which coating will help, but partly because of gas expansion which is necessary both to properly evacuate the gas and to get the noise level down. So the temp will drop along the pipe, and the velocity of sound is proportional to the sqrt of the absolute temp... and in any case, we are far from the small deviations from atmospheric pressure in which the acoustic approximation holds...

Are you sure that rate of pipe expansion is enough? It seems small by multi-cylinder standards, but you are working in a different rpm range.

PS How much does a zircotech coating cost?

I'm thinking about that expansion as well, but no room to get a expanding pipe underneath the engine :s. I top out at 9200 rpm and the engine keeps making power until that point so I calculated the exhaust for 8000-8500 rpm because I shift at +- 8500.

I only have sponsor prices from zircotec (that I can't tell you  ) but it's never all that expensive. I believe the most performant white coating they have is 80 euro's for coating a piece of exhaust tube (length doesn't really matter).

what do you think on the effect of the parts behind the first silencer? what would you change to this exhaust?

thanks!

MJ

No one here that knows about 4-stroke exhausts and that can help/think with me?

Maybe a topic about it on pit-lane? (that I can't find)

cheers,

MJ

Find below the a link about exhaust for single cylinder 4t

best regards
Rudg

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I would probably do something dumb like 8500 x 690/500 =11,700, ie vaguely the same sort of gas flow as a Duc 999RS at peak power. Then I'd go have a good look at some pipes for such a beast :)

Actually it's interesting that Ducati pipe philosophy is quite special: a very rapid increase in diameter in the first 15cm, followed by a large, constant diameter pipe. In contrast, Akrapovic et al tend to start smaller and taper up over 50cm or more.

Not so good throttle response suggests maybe there is an extra resonance generated by the 1-2 split in the original pipe, which made a nasty dead-spot at some rpm... nothing shows on the full throttle torque curves?

GrahamB a écrit:

I would probably do something dumb like 8500 x 690/500 =11,700, ie vaguely the same sort of gas flow as a Duc 999RS at peak power. Then I'd go have a good look at some pipes for such a beast :)

Actually it's interesting that Ducati pipe philosophy is quite special: a very rapid increase in diameter in the first 15cm, followed by a large, constant diameter pipe. In contrast, Akrapovic et al tend to start smaller and taper up over 50cm or more.

Not so good throttle response suggests maybe there is an extra resonance generated by the 1-2 split in the original pipe, which made a nasty dead-spot at some rpm... nothing shows on the full throttle torque curves?

Didn't norice that about the ducati's but now that you mention it...

There was nothing like a nasty dead-spot in the torque curve wit the 1 into 2 pipe...

What do you think the effect of the piece of pipe between the two silencers in my current setup is? And the effect of the second silencer? Because if I removed these it ran a lot better...
I've just sent my exhaust away for zircotec coating. I've only sent the first two pieces (so everything until it reaches the first silencer) So that I can still experiment with everything from there on to the end of the system.

No idea... not enough experience. At best I can guess: the role of a silencer is to de-cohere the sound waves and lose some energy by allowing expansion into the packing. That is  the opposite of what you would want for a resonance or travelling wave phenomenon to improve scavenging. So my random guess is that the pipe between the two silencers should be much bigger in diameter than the first part... maybe with a converge cone for the core in the second, or some sort of smooth venture like Akrapovic use at the entry to the silencers on their 1198 pipes.

But can you explain better what you mean by better or worse throttle response ?

Bravo et magnifique et merci de nous en faire profiter.

Faudrait la vidéo embarquée

GrahamB a écrit:

No idea... not enough experience. At best I can guess: the role of a silencer is to de-cohere the sound waves and lose some energy by allowing expansion into the packing. That is  the opposite of what you would want for a resonance or travelling wave phenomenon to improve scavenging. So my random guess is that the pipe between the two silencers should be much bigger in diameter than the first part... maybe with a converge cone for the core in the second, or some sort of smooth venture like Akrapovic use at the entry to the silencers on their 1198 pipes.

But can you explain better what you mean by better or worse throttle response ?

wouldn't the bigger diameter slow the gasses down and give a big pulse back to the engine, while we would just want them to get out after they have already been slowed down by the first silencer? Or will the bigger diameter speed the gasses up? Same for a megaphone shape, it slows the gasses down, right?!

What do you mean with the "venture" I can't see it on pictures? maybe you can put an example here.

Better throttle response: sharper feel and less "ON/OFF" effect.

Argh... venture should be "venturi". If you go to the Akra site, fight your way through to the full systems for 1198 etc and look at the exploded view, you'll see what I'm talking about :)

For the larger pipe, I'm thinking to avoid trying to compress the gas down again after the muffler has let it expand. A megaphone lets the gases expand while staying coherent (which is why a trombone works) and reflecting a negative pressure wave to help scavenge. A silencer lets them expand chaotically so all the pulse structure is lost.

But as I said, I'm guessing...   

Very, very beautiful bike and very good job, congratulations.  

davidnb44 a écrit:

Bravo et magnifique et merci de nous en faire profiter.

Faudrait la vidéo embarquée

semi-slicks in the rain on croix: [Vous devez être inscrit et connecté pour voir ce lien]

this other movie is first time on a real racetrack clearly missing power but making up for it with the brakes (ESA @ red bull ring) I know the driving isn't great but that was the first time on a big track for me and the bike, it has improved since then   --> [Vous devez être inscrit et connecté pour voir ce lien]

2strokeman a écrit:

Very, very beautiful bike and very good job, congratulations.

thanks!

grtz

MJ

Graham, to continue on the exhaust topic:

firstly, the duke 4 akrapovic also uses a twin "in-line" silencer system (ugly bike, just look at the exhaust):

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Maybe I can up the gas speed after the second silencer to "suck it empty" by adding something like the Ferrari F12 has? I think this could up the velocity without giving to much backpressure?

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BTW: we don't need to be experts, let's just start by using our basic insight  

MJ-Works a écrit:

firstly, the duke 4 akrapovic also uses a twin "in-line" silencer  system

Yes, good point... singles are hard to quiet!

What I notice is that the first silencer is a lot closer to the head on the Duke. If you are good friends with the Dyno operator, it would be good to make up a straight-pipe replacement for the first silencer, then try all the combinations: short, long, first silencer, second silencer, both silencers. If it works well with the pipe ending after the first silencer, then you would need to add axtra pipe that was less apparent to the engine... which is part of my foggy idea about making that next bit larger in diameter. But then you would need to bring it down again to get into the second muffler, hence the venturi idea.

I have tested everything until I fitted the second silencer. So the first pipe has had some prototypes before it was made fully out of titanium!

It would indeed be logical to improve the gas-exit from the first silencer, since adding the second one has cost me power. The pipe between the two silencers is currently 50 mm, maybe I should increase it to 60 mm and just re-make the internals of the second silencer to 60 mm? (if the carbon fibre can cope with the extra heat due to less insulation thickness).

Unfortunally no good friends that have a dyno   

found the venturi's you've mentioned btw, but these will again increase backpressure of which I presume I already have too much with the two silencers

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This is a quick sketch of the options that I'm thinking about to build:

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MJ-Works a écrit:

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I really can't work out what that would do, other than make the noise different in some subtle way  

Design artifice to affirm the technical/male aesthetic of the muffler exits ?

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Stéphane