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The below PDF describes what I did on my '37 120 but could apply to a wide range of our cars. It lays out how to create an exhaust system from scratch at your shop instead of leaving it all to the muffler shops. They will still need to bend the pipes, but the rest is on you.
Enjoy,
Bob J.

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Exhaust System Modelling.pdf Size: 889.97 KB; Hits: 215

Well done Bob!

Please describe the reaction of the muffler-shop crew when this ‘crazy’ guy walks in with a bunch of lumber. I bet they are still talking about that experience. Were you allowed to watch/participate in the fabrication?

dp

They were very enthusiastic!! Can't say they ever had seen the like before but first of all, anyone involved in auto mechanics loves old cars, so you are already a welcome client. The other point expressed by all, was that they were so happy to have such a detailed model to work from. Doing it in wood, even the scrap pieces I did it in, allowed them to make the bends very accurately and not have to worry about me coming back and having to do it again. The last issue they had was that I needed to bring in the new donut gasket so that they could get the collar on the exhaust pipe in the proper place for a good seal. I was fortunate too that the car still had the original collar that attached the exhaust to the manifold. There is nothing currently used in the new cars that would retrofit.
Afterward I made sure I called them back to let them know how well it went together, even with a shade tree guy like me doing the work!
Bob J.

Bob, did you forward the shop a copy of your pdf? I’m sure the shop would share that knowledge with the next customer that wants to build a ‘custom’ exhaust. dp

or just buy one from Waldron's, et al.
I'd be curious to know how well it matches the OEM replacements from the computerized bending equipment and how they knew to make the muffler longer/or off the shelf/listed.
I bought one from the guy in NC in the PAC ads for the '49 and it fit like a glove and the xframes are tough to navigate pipes thru. It was very reasonable back then. I expect today, you have to bring the first born for the exchange at least an arm. I picked it up from his shop. I think he's since sold that business/don't keep up.
As the old saw goes, if you get a carpenter to fix something expect a few hammer blows, so goes it for industrial designers and mock ups. To each his own according to their abilities in DIY land.
When it said "modeling" I was expecting something different than a .pdf like 3D sketch or something. Not many homes have a laser scanner to generate the mesh. I don't even have AutoCaD any more since I re-retired. Everything is pay by the month now even Adobe. At zero usage that's infinite cost/month. I liked the pay for it once era. It makes us retirees take the free offer then cancel with we need something. They're getting tricky, and send you a pop-up and if you touch the screen it bills you. Happened again today. ottabalawaginit.

Sorry you were so disappointed with the PDF. The intent was to help someone do something they may have not thought they would be able to do on their own car.
OEM would not work as in this case there are 2 different platforms, the exhaust pipe has a different manifold angle and diameter to a 37 and the chassis is different than the 53 Patrician, so comparing the results to any off-the-shelf product for the case study I did the article for is moot.
The model was made so the shop I dealt with, which reflects the majority of muffler shops I have seen, could simply bend stock pipes on their hydraulic ram to the form I created, yes there are 3D mandrel bending shops but this was not one, and there are none locally. (I could have made it as a 3D model as that is my life too but what good would that do in a shop not equipped?)
I also did the description for the vast majority that have neither access nor knowledge of any 3D modelling. I was not intending to create a model other owners could use as I doubt very much my particular combination of requirements will be duplicated again.
The muffler itself was custom made at a different shop to a drawing I supplied with a given tolerance to accommodate their process requirements. Knowing that the muffler would likely not be exact, allowance was made by lengthening the pipes slightly at the muffler joint. The trimming was simple and quick again by having the model for reference.
Cost was very good. $120 for the muffler. $300 for all stainless steel pipes, and $20 for the hangers and clamps. Labour was $100. (All prices in $CDN).
I am afraid that I am bashing my way through this DIY land as I work on my car. I thought that is what our hobby is about? Wrong again, but then I am only an Industrial Designer.
I will be sure not to bother posting again.
Signing off,
Bob J.

Don’t let this be your last post

Agree...I am impressed by your work and enjoyed following along...Ernie in Arizona...Just down the road from David Packard!

If anyone reading this has followed the tailpipe issues in the blog for my 1951 Henney-Packard, I had absolutely no luck in getting one made even from the factory blueprint! I suspect if I had printed it full size they may have been able but the blueprint itself seemed to confuse more than help!

Bob I thought your PDF was written well.