Welding Tips and Tricks

Hi guys!

First, let me introduce myself. My name is Simon Kvas, I am 22 years old and I come from Slovenia. I recently graduated on Faculty of Mechanical Engineering. My biggest hobies are welding and tuning two stroke, so I decided to incorporate that into my thesis. The main goal of this thesis was to determine appropriate welding technology for welding titanium and thus overcome poor weldability of this material. With known welding technology I have then fabricated exhaust system made from titanium sheet metal and compare it to steel exhaust with same dimension after testing both on inertial dynamometer. Main point of interest was how different materials affect engine power. Proper welding technology was determined by different methods, such as visual control of the weld, hardness measurement and bend test. Because of its different thermal properties, titanium exhaust shifts maximum engine power to higher RPM. Ok so enough of talking, here are some pictures for you guys. Feel free to leave any coments, suggestions, opinions and sory for my bad english.






Short video of fabrication: https://www.youtube.com/watch?v=F0YRg1J9Vig

Regards, Simon

Welcome
Nifty thesis subject
Welds look good
English no worse than the rest of us posters
Thermal properties effect power band,interesting!
Looking forward to more posts.

would love one for my KX 500!!
a real beauty
craig

Very nice! I have never done titanium, wishing I get the chance one day. Your English is fine, mine falls apart after 15 or 16 beers There is a lot of science and study behind what materials do to engine power. I wish you luck in your studies!

Nice work. And great thesis subject. I had no idea that the thermal properties of the exhaust material could affect the power band. Well done.

Holy cow, nice looking job. Like the rest did not know the correlation between the material and output.

Very nice!

It would not have occurred to me, but I guess it makes sense that the thermal conductivity of the material would affect the expansion of gasses in an expansion chamber...

I'd love to know more.

Steve S

I'd love to know more too!
I can understand how the thermal conductivity of the material effects gas expansion. I would have thought once full operating temperature was reached and steady state achieved it wouldn't make any difference. Maybe that's where the expansion chamber comes in?

Hey guys thanks to all for such a nice response. I hope I can explain this right, because it has been some time since I used English more often. As we all know, exhaust is very important component on two stroke engine. Two stroke exhaust is usually made of five components. Header, difusor, mid section, cone and stinger. Each of them has its own role. The most important thing is temperature inside exhaust. The bigger the temperature, the faster the exhaust gases. So for example if we make a exhaust of a certain length and compare it to a shorter exhaust. Engine with longer exhaust fitted will work on lower RPM then the one with shorter exhaust because temperature in it will be smaller, also the the gases will be slower. The same thing is with changing the exhast material. Titanium has a very weak thermal conductivity, smaller heat transfer coefficient and smaller thermal emissivity, compared to steel. The end result is the same as shortening the exhaust or to heat wrap it to achive higher RPM. I hope i was understandable enough. Take a look at the picture below to see the difference of one exhaust compared to the other. You guys can probably figure this out from a legend, but anyways.
Black curve - steel exhaust
Red curve - titanium exhaust



Regards, Simon

Almost looks like it smooths it out a bit as well.

One of the biggest tuning changes we could make in very short order trackside on the race karts was to change the length of the flex section between the "header" (basically just a homologated piece of pipe that was the same in every kart) and the expansion chamber/muffler.

Our drivers would also use EGT (exhaust gas temperature) readings on their RacePak dash on the steering wheel to make carb changes on the fly. Our engine builder would give us a dyno card that says they make peak horsepower at "x$ degrees F of EGT. The driver would then either richen or lean the engine out using the high speed adjustment screw on the carb.

The change in exhaust had a direct correlation to where the kart came in to power/how responsive it was coming back on throttle after braking/turning. We were also turning 22k rpms with about triple the horsepower out of a 125 2 stroke, so everything happened more violently, and at greater speed. Some of our shifter karts would hit 120mph, and our centrifugal clutch single speed karts would hit 75-80. They were speed limited by the fact that you had one gear to pick to make up for long straights and tight turns on throttle.

Sent from my SM-G900V using Tapatalk

My experience with 2 cycle exhaust in 60's-70's was Black Magic. With today’s instrumentation your welding skills/knowledge it has taken some of the black out of the magic. Carry on will be interesting to follow. Your English explanations more than adequate for this old guy.

Again i would like to thank you all for support and great responses. I have always dreamed about how I am going to work on cars, motorcylces and racing stuff once I finish my school. But here in Slovenia there are only individuals who are dealing with racing or tuning cars and motorcycles. Two stroke engines are almost totally neglected. And this really bothers me, I am such a huge fan of racing, welding and fabricating but there is no such company in Slovenia that would deal with that kind of stuff... I dream every day when I watch your Discovery shows such as American outlaws, OCC. It would really be a dream come true to experience that in live, even if it is really half the truth they show on TV

KVAS
what engine with this connected to?
how many CC?
craig

KVAS wrote:Again i would like to thank you all for support and great responses. I have always dreamed about how I am going to work on cars, motorcylces and racing stuff once I finish my school. But here in Slovenia there are only individuals who are dealing with racing or tuning cars and motorcycles. Two stroke engines are almost totally neglected. And this really bothers me, I am such a huge fan of racing, welding and fabricating but there is no such company in Slovenia that would deal with that kind of stuff... I dream every day when I watch your Discovery shows such as American outlaws, OCC. It would really be a dream come true to experience that in live, even if it is really half the truth they show on TV

Sadly, it's not even half of the truth. My friend, who is a machinist, and probably the most anal person I have ever met, got to see OCC's bikes up close at Sturgis a few years ago and he told me that they were hack jobs. Not the production bikes but the custom ones made for the show. He said there were so many things wrong that he it looked like the bikes were built in a highschool metals class. He said that everything that was outsourced on the bikes, such as paint and chrome was great but OCC's part was a cobble job. Best of luck in your endeavors. Want anything bad enough and you will get it.

exnailpounder wrote:

KVAS wrote:Again i would like to thank you all for support and great responses. I have always dreamed about how I am going to work on cars, motorcylces and racing stuff once I finish my school. But here in Slovenia there are only individuals who are dealing with racing or tuning cars and motorcycles. Two stroke engines are almost totally neglected. And this really bothers me, I am such a huge fan of racing, welding and fabricating but there is no such company in Slovenia that would deal with that kind of stuff... I dream every day when I watch your Discovery shows such as American outlaws, OCC. It would really be a dream come true to experience that in live, even if it is really half the truth they show on TV

Sadly, it's not even half of the truth. My friend, who is a machinist, and probably the most anal person I have ever met, got to see OCC's bikes up close at Sturgis a few years ago and he told me that they were hack jobs. Not the production bikes but the custom ones made for the show. He said there were so many things wrong that he it looked like the bikes were built in a highschool metals class. He said that everything that was outsourced on the bikes, such as paint and chrome was great but OCC's part was a cobble job. Best of luck in your endeavors. Want anything bad enough and you will get it.

Thx man

motox wrote:KVAS
what engine with this connected to?
how many CC?
craig

The engine is AM6 from Minarelli with malossi MHR 50cc cylinder on it. It still has a lot of reserve as cylinder and crankase are still original form factory.

figured a small bore with only 12 plus HP.
do you race as well as?
craig

exnailpounder......
"Sadly, it's not even half of the truth. My friend, who is a machinist, and probably the most anal person I have ever met, got to see OCC's bikes up close at Sturgis a few years ago and he told me that they were hack jobs. Not the production bikes but the custom ones made for the show. He said there were so many things wrong that he it looked like the bikes were built in a highschool metals class. He said that everything that was outsourced on the bikes, such as paint and chrome was great but OCC's part was a cobble job."

I kind of always expected that. Genius at reality TV and building a "Brand", that's what built their nice shop and bank accounts, not the quality. Most people do not understand the price of "quality", and are either unwilling or can't afford the cost. But I am certainly not hating on them, more power to them.

Two of the most elusive variables in the personal wealth calculation is luck and timing.

motox wrote:figured a small bore with only 12 plus HP.
do you race as well as?
craig

Just mopeds for now but I am planing to build a 250cc road racer.

Sadly, it's not even half of the truth. My friend, who is a machinist, and probably the most anal person I have ever met, got to see OCC's bikes up close at Sturgis a few years ago and he told me that they were hack jobs. Not the production bikes but the custom ones made for the show. He said there were so many things wrong that he it looked like the bikes were built in a highschool metals class. He said that everything that was outsourced on the bikes, such as paint and chrome was great but OCC's part was a cobble job. Best of luck in your endeavors. Want anything bad enough and you will get it.

Jesse James was the real deal bike builder
craig

If you look at the picture I've used as my "avatar" here, that's an OCC bike I'm sitting on. The executive VP for Airgas took that picture for me.

I might ride it in a parade, but I would not be comfortable on the Will Rogers Turnpike at 70 MPH.

Sure, it's pretty, but I would question the design, and am not impressed with the construction. The tank is an ACTUAL acetylene tank, not a replica, so it's top-heavy as hell.

BTW, the AirGas bike build did not appear on TV.

Steve S

As a fellow welder, biker and two-stroke nut, I am loving this thread.

And to the OP...very nice work!



Kym