With the frame completed the next step was the exhaust system.  Since Goliath is a unique vehicle, there wasn't any off the shelf products that would work, so a custom exhaust was needed.  The engine's 30HP rating is with the air filter removed and no exhaust, so keeping the back pressure as low as possible was important.  The engine has two exhaust ports so a dual exhaust system was built.  The exhaust system was started from a exhaust kit and muffler intended for racing go-karts.  The most difficult part to find was the right exhaust flange to fit the engine.  After spending some time looking around, I decided to try making  the exhaust flange out of steel on the CNC Router.

The CNC router used was a CNC Router Parts 2448. It's a very beefy router, but it's not made to be cutting steel, same as most CNC Routers.  After doing a bit of research, it seemed that it would be safe enough to attempt cutting the two flanges I needed, as long as the machine went really slow so I don't put too much stress on the system and used a coated end mill to help keep the temperatures down.

It worked out ok.  As you can see from the video, I didn't set the depth deep enough on the first pass.  The biggest problem with the final piece was that the bar stock I used wasn't very flat, which meant that it wouldn't create a good seal.  In the meantime I found a universal flange that would work with some extra welding and decided to go that route.

Below are the exhaust parts kit used to build one side of the exhaust.

After test fitting the parts together on the vehicle, they were taken back off and welded together.  Below are most of the elements welded together.

With the exhaust assembled, it was test fit one last time and a bracket was made to support the exhaust.  The bracket was made by twisting a piece of flat slotted steel and a U-bolt was used to mount the tubing.

A coat of high temperature primer and paint was added to keep the steel from rusting.

The exhaust was then bolted back onto Goliath for the final time.  You may notice that the exhaust isn't symmetrical.  When I was fitting the exhaust on the starboard side, I accidentally placed the pipe on the wrong side of the bracket and welded the flange at the wrong angle.  It'd be a lot of effort to rework it, so I'm going to leave it for now and fix it later if it becomes an issue.

At this point the only things keeping us from testing out the engine is getting the fuel and electrical hooked up to it.  I'll talk about the initial electrical system next time.