Monday, November 24, 2014

Outlet Elbow Ends Trimmed

 The round inlet end of the elbows were marked, band sawed and ground just like was done for the outlet end of the manifold.

For the outlet end of the elbow I followed a similar process.  I used the form block to mark the cut lines on the flanges.

To draw the cut line I started by using a straight edge to line up a block in the bottom of the opening so I could mark the bottom of the cut line.

 To mark a straight line in the curved outlet I used the Pin Contour Gauge as a guide.  The shape of each shell is slightly different so it made an easy way to create a guide for each one.  You just line it up wit the three marks and draw a line along it with a pencil.

I then cut off the scrap with the band saw like the inlet end, and ground the end square and smooth wit the belt sander.  A little deburring and the end was done.

Sunday, November 23, 2014

Trimming Exhaust Shell Inlets and Outlets

 Around the inlets the welded flange is cut off to give clearance for the exhaust stud nuts.  The flange is also cut off at the outlet end for the elbow to slip over.
 I thought about all sort of complicated tools to mark the cut lines.  In the end I decided to use the old form block, which was setting around.  I drew the cut lines for the ends of the cut offs on the block.  Then I placed a shell in the block and drew the lines on the shell, using the lines on the block as a guide.

 To make the cuts easy I punched 1/4" holes in the corners using the line as a guide.  Normally I would center punch where I want the hole.  In this case the hole location is not that critical.  Instead I turned the Whitney Punch upside down and looked through the hole in the die to line up the edge of the hole with the line.  You have to clear out the slug in the die after each punch so you can see the line, but it worked fine

 I realized part way through that a red line was easier to see in the die hole than the pencil line I started with.

 For the outlet end I needed to first cut off the excess metal from the forming operation.  I had started making a tool for shaping this end during assembly, more on it later.  I decided it would make a good guide for drawing the cut line because it would stay square in the shell.  Just position it in the shell and draw a pencil line along it.

 I cut the end off with the band saw.

I could have used a supports for the shell while sawing.  I was able to tip the shell for half the cut and support the flange with a block of wood for the other half of the cut.

To clean up the cut I just used the belt sander and deburred the edge.

 Once the outlet end was cut off I just used the snips to cut along the lines I drew and to follow the edge of the tube to the hole.  You need left and right snips to do this.

They came out very good.  They're starting to look like parts which could make the manifolds.

Wednesday, November 19, 2014

Manifold Shells Trimmed

 All the manifold shells, enough for 3 motors, are trimmed to the scribe line.  As with the outlet elbows, I've sorted them into tops and bottoms because of the different width of the flange.

The next step is to trim the inlet and outlet ends.

Tuesday, November 18, 2014

Trimming First Shells

 I have all the outlet elbows trimmed.  You can see here how much gets trimmed off.

The marking tool made a line which was easy to follow with the band saw, just outside the cut line.

For the outside curves the belt sander made it easy to grind to the line leaving a nice smooth curve.

I still have the inside curves to smooth up and then trim the ends.

Sunday, November 16, 2014

Trim Line For Exhaust Shells

 I haven't finished the exhaust manifolds because I've been busy on other things and I didn't like any of my ideas for trimming the shells and for forming the edge overlap bends.

I've had a great idea for marking the trim line on the shells.  It's kind of the reverse of scribing a line on a board with a marking gauge.  Instead of the guide being on the scale, the guide is the rounded end of the block of wood.

For a scribe I used a coarse thread drywall screw.  I drilled a hole at the distance for the flange on the lower shell and a hole 1/4" further out for flange on the top shell.  The edge of the top shell wraps around the edge of the bottom shell to make a nice finished edge.  You adjust the screw tip, for the line you want, to just stick out of the block.  Run the block around the part leaving a nice even trim line.

Too simple.