<p>This report describes the development process of a pipe clamp used on exhaust system for cars. It is made based on the manufacturers desire to improve and make the clamp easier to manufacture and to reduce its price to their customers. This should be done either by manufacturing the clamp in one piece without an expensive and work intensive welding process, or by generating ideas of how to develop a brand new type of clamp. Investigating the market for similar products was done to eliminate intrusion of other manufacturers’ patents but also to generate ideas. Making drawings of the many ideas gave a concept of three concepts called existing clamp in one piece, existing clamp by several pieces and innovation solutions. Some of these ideas were investigated further and were 3D modelled in pro-engineer and necessary drawing files were made to be used in the manufacturing of several prototypes. One of the solutions resulted in a prototype that was manufactured by handmade tools and the results of the tests was very positive. The clamp was strong enough to join the pipes together very well without breaking. It was manufactured in one piece and formed in five steps without any welding operations instead of the seven steps, including welding, that is used on the clamp today. The prototype requires 25 % more material and most of it is scrap from the cutting operation.</p>

This report describes the development process of a pipe clamp used on exhaust system for cars. It is made based on the manufacturers desire to improve and make the clamp easier to manufacture and to reduce its price to their customers. This should be done either by manufacturing the clamp in one piece without an expensive and work intensive welding process, or by generating ideas of how to develop a brand new type of clamp. Investigating the market for similar products was done to eliminate intrusion of other manufacturers’ patents but also to generate ideas. Making drawings of the many ideas gave a concept of three concepts called existing clamp in one piece, existing clamp by several pieces and innovation solutions. Some of these ideas were investigated further and were 3D modelled in pro-engineer and necessary drawing files were made to be used in the manufacturing of several prototypes. One of the solutions resulted in a prototype that was manufactured by handmade tools and the results of the tests was very positive. The clamp was strong enough to join the pipes together very well without breaking. It was manufactured in one piece and formed in five steps without any welding operations instead of the seven steps, including welding, that is used on the clamp today. The prototype requires 25 % more material and most of it is scrap from the cutting operation.

Detta kandidatexamensarbete behandlar design och konstruktion av ett nytt avgassystem för en motorcykel. Utvecklingen grundar sig på resultat från en körning i bromsbänk av motorcykeln utrustad med original avgassystem, där det visar sig att det finns en påtaglig dipp i vridmoment mellan 4000 och 6500 rpm. Samt på resonemang kring avgassystemets geometri och dess inverkan på motorns egenskaper. Dessa resonemang grundar sig i sin tur på fysikaliska principer. Målet med projektet är att utveckla ett avgassystem som påverkar motorn på det sätt att vridet i motorns mellanregister ökar för att utradera den påvisade dippen i mellanregistret samtidigt som det fortfarande ska uppfylla de krav svensk lagstiftning ställer på motorcyklar angående ljudnivå. Resonemangen på vilka avgassystemet utformas behandlar cylinderspolning, lågtryckspulser, avgasernas hastighet, avgassystemskonfiguration och cylinderparning. Det beslutas att systemet ska utformas på så sätt att avståndet till kollektorer blir så långt som möjligt i tillgängligt utrymme, att avgassystemet ska vara av 4-2-1 konfiguration och att cylinder 4 och 1 respektive 2 och 3 ska paras ihop. Avgassystemet tillverkas med enbart handverktyg och består till största del av standarddelar. Efter konstruktion så testas det nya systemet med en körning i bromsbänk och en ljudmätning. Den resulterade grafen från körningen i bromsbänken visar att dippen i vridmoment mellan 4000 och 6500 varv utraderades samtidigt som momentet ökade lite genom hela registret. Maximala vridmoment ökade från 103,7 Nm (Newtonmeter) med original avgassystem till 106,6 Nm med det nya. Toppeffekten ökade från 115,7 hk (hästkrafter) till 122,5 hk. På grund av att tillgång till verkstad försvann i och med pandemiutbrottet våren 2020 så beslutades att inte tillverka någon ljuddämpare, istället inhandlades och monterades en standardiserad fullflödesljuddämpare. Ljudmätningar visar att målet med ljudnivån inte uppnåtts. För att vara lagligt så får den maximala ljudnivån vid 5200 rpm inte överstiga 93 dB (decibel). Det nya systemet uppmättes till 109,4 dB vid 5200 rpm och klarar därmed inte ljudnivåkravet. Projektet visar att det är möjligt att markant påverka motorkaraktären med ändringar i avgassystemets geometri och konfiguration. Detta projekt visar dock bara på vad summan av förändringarna åstadkommer och kan inte ge specifika svar på vilka ändringar som står för vilken del av resultatet. / This bachelor's thesis deals with the design and construction of a new exhaust system for a motorcycle. The development is based on the results on a dyno run of the motorcycle equipped with the original exhaust system as well on reasonings regarding the exhaust system geometry and its impact on engine characteristics. These reasonings, in turn, are based on physical principles. The dyno run with the original exhaust system showed a significant dip in torque between 4000 and 6500 rpm. The aim of the project is to develop an exhaust system that affects the engines performance in a way that results in the increase of the engines midrange torque in order to erase the detected dip in the midrange while still fulfilling the requirements Swedish legislation imposes on motorcycles regarding noise pollution. The reasoning on which the exhaust system is designed deals with cylinder scavenging, low pressure pulses, exhaust speed, exhaust system configuration and cylinder pairing. It is decided that the system shall be designed in such a way that the distance to collectors is as far as possible in the available space, that the exhaust system shall be of 4-2-1 configuration and that cylinders 4 and 1 and 2 and 3 shall be paired. The exhaust system is manufactured using hand tools only and consists mostly of standardized parts. After construction, the new system is validated with a dyno run and sound level measurements. The resulting graph from the dyno run of the motorcycle equipped with the new exhaust system shows that the dip in torque between 4000 and 6500 rpm was erased while the overall torque increased slightly throughout the register. Maximum torque increased from 103.7 Nm with the original exhaust to 106.6 Nm with the new. The peak power increased from 115.7 hp to 122.5 hp. Sound measurements indicate that the aim for the sound level has not been achieved. To be legal, the maximum noise level at 5200 rpm must not exceed 93 dB. The new system was measured at 109.4 dB at 5200 rpm and thus does not meet the sound level requirement. The project shows that it is possible to significantly influence the engine character with changes in the geometry and configuration of the exhaust system. However, this project only shows what the sum of the changes achieves and cannot provide specific answers as to which changes account for what part of the result.

To be able to predict the sound pressure level emitted by a exhaust system one must be able to describe the source. The source in the form of an engine can linearly be described as a source strength and a source impedance. An IC-engine can acoustically have a non-linear part meaning that the source characteristics have a dependency on the load. The first part of this work investigates through simulation's in GT-Power how these characteristics are affected by the load connected to the source. The Second part of the work combines the source characteristics with simulations of a muffler and compares to different methods of getting the pressure at the outlet of the exhaust. The first method is direct simulation of the muffler in COMSOL Multiphysics and the second is a transfer matrix based calculation. How sensitive the results at the outlet are to changes in the source impedance is also tested. It is concluded that using five loads for the multiload method in the form of five different lengths on the pipe connecting the engine and muffler works when the pipe have the same length as would be seen in reality. Furthermore, the pipe lengths should have a small range, 100 mm between largest and smallest pipe length giving good results. The source characteristics were at least above 1000 RPM stable enough as to not significantly change the sound pressure level at the outlet. / För att kunna modellera ljudtrycket som avges från ett avgassystem behöver man kunna beskriva källan. Källan i form av en bränslemotor kan linjärt beskrivas som en källstyrka och en källimpedans. En bränslemotor kan dock ha en akustisk ickelinjär del vilket medför att källan kan vara beroende utav vilken last i form av ljuddämpare den är kopplad till. Första delen av detta arbete undersöker genom motorsimuleringar i GT-Power hur lasten påverkar källkarakteristiken. Den andra delen av arbetet kombinerar källkarakteristiken med simuleringar av ljuddämparen och jämför olika metoder för att få ljudtrycket vid utloppet av avgassystemet. Den första metoden för detta är direkt simulering av ljuddämparen i COMSOL Multiphysics där källkarakteristiken inkluderas och den andra metoden är transfermatris baserad. Det testas också hur känsligt ljudtrycket vid utloppet av ljuddämparen är för variationer i impedansen. För källkarakteristiken används fem laster per uträkning och slutsatsen dras att lasten i form av röret mellan motor och ljuddämpare samt ljuddämparen bör vara så lik som möjligt det riktiga systemet. Utöver det dras slutsatsen att en liten variation i det kopplande rörets längd ger bättre resultat och att en variation mellan största och minsta röret på 100 mm ger bra resultat. Till sist dras slutsatsen att för varvtal över 1000 RPM är källkarakteristiken tillräckligt stabil för att ge stabila resultat vid utloppet av ljuddämparen, medans under 1000 RPM kan det vara stabilt nog men här är validering viktigare.