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 Post subject: Muffler Mounts
PostPosted: February 25, 2014, 12:17 am 
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Here's something I clearly didn't give enough thought to on my build. The book has a nice picture of a cotton reel exhaust mount on page 88. It looked good, and it was in the book, which was good enough for me. So that's what I did.

Don't do that. If you're still working on your exhaust setup, there are many better ways. In fact, I'd venture to say that ALL other ways are better. Those cotton reels don't last more than a couple hundred miles. Tops. I've broken two so far. I'm not sure if they succumb to the vibration, pipe expansion, or the heat. Maybe all three.

I took a page from the Westfield exhaust and built something a little more robust this time. Best I could do with the existing holes and muffler. Better would be a modern style hanger with pins, but that needs to be designed in.

The guts of the new mount is a McMaster-Carr vibration isolator. It's good for up to 300 degrees, so we'll see.

Attachment:
hangermount.jpg

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brokenhangermount.jpg

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newhangermount.jpg

Attachment:
finishedhangermount.jpg


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 Post subject: Re: Muffler Mounts
PostPosted: February 25, 2014, 9:33 am 
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Nick, classy solution. that's gonna last a good long time.

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 Post subject: Re: Muffler Mounts
PostPosted: February 25, 2014, 10:05 am 
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Looks great Nick. Those rubber bobbins installed horizontally are always a bad choice, placing the rubber in shear. Your solution is a good one. Nice and clean looking even from the side view. Here was my answer to that problem:
Image

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 Post subject: Re: Muffler Mounts
PostPosted: February 25, 2014, 11:54 am 
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My first exhaust hanger, was also a bonded rubber mounting system. But I had the same breakage problem, because it is the only mount for the complete exhaust system. After breaking a couple rubber mounts, I changed the mounting system for the exhaust, to a small coil spring hanger. The under side of the aluminum bracket has a couple rubber washers and the top side is a coil spring with a thru bolt that attaches to a small rod end. There is also small rubber gommet in the center of the bracket so the thru bolt does not contact the aluminum bracket. This hanger allows you to adjust a little pre-load into the coil spring, and the rod end allows the whole exhaust system to twist when engine torque rolls the exhaust system. I do not think this attachment will break. Dave W


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 Post subject: Re: Muffler Mounts
PostPosted: February 25, 2014, 12:38 pm 
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I like that, Dave. I could probably replace my rubber isolator with a spring and give the mount a little more movement. The pipe does lengthen a bit, 1/4" or so, when it heats up, so the rubber gets stretched a good deal. Plus, no worries about the spring getting too hot.


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 Post subject: Re: Muffler Mounts
PostPosted: February 27, 2014, 11:11 am 
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Imho, any bonded isolator to hang the exhaust from is bad, but you've made the most of it. Your design is similar to Westfields, who also use a bonded isolator without a thru-bolt.

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 Post subject: Re: Muffler Mounts
PostPosted: February 27, 2014, 8:57 pm 
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Here is mine, I kind of took the lazy way out and just welded a piece of one inch by 1/8 inch strap to the bottom of the car and then used a piece of rubber from a shock mount.
I am not sure whether it was a good plan or not but it has stood up for the last two and half years just fine.

Al


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 Post subject: Re: Muffler Mounts
PostPosted: February 28, 2014, 1:15 am 
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That's very good, Al. That's more or less what I have now, or actually less, since mine had to be cobbled together with the mounts I already had and therefore weighs a ton. Putting the rubber isolator in compression instead of shear is probably obvious to anyone who's built a car before, and probably anyone who hasn't.


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 Post subject: Re: Muffler Mounts
PostPosted: February 28, 2014, 2:24 pm 
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Location: worcester county, Massachsetts
I'll add mine for reference...

in this picture you can see both of the exhaust hangers along the pipe from the engine and along the drivers side (the muffler has its own non-isolated hangers)

a piece of 3/4 square tube with a shorlt lenth of 1 x .065 wall round. The isolators are triumph spitfire control arm bushings. 1/25 x .125 tabs are welded to the enxhaust pipe in dbl shear.

I should mention that the B-3 motorcycle in-unit engine/transmission is fundamentally solidly mounted, so exhaust movement isn't really a concern for me.

Attachment:
20130826_201659.jpg


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The beginnings of the Jag Special,
https://www.locostusa.com/forums/viewtopic.php?f=36&t=19012
Again, all pictures were lost.


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 Post subject: Re: Muffler Mounts
PostPosted: July 13, 2014, 10:29 pm 
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Joined: December 4, 2013, 7:06 am
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Hi
I have found that using a strap type clamp around your exhaust or muffler rather than welding to the exhaust works well. When you weld you form a stress point for the vibrations to work on, normally leading to cracking.
The strap can then be attached to a fixed mount on the car using the rubber couplings. Worked for the last 20,000 miles for me after my original welded strap broken after 6,000 miles.
Cheers
Maurice


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 Post subject: Re: Muffler Mounts
PostPosted: July 17, 2015, 10:13 am 
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I haven't built mine yet, but this is what I'm planning on doing.

Utilizing a bolt on clamp, as I know its possible but I'm not really excited about using mild steel filler on a stainless application, as shown below. For my application I need to switch the 'hanger rod' and install it backwards so its pointing downwards in the picture.
Image

On the body of the car I plan on having the grommet portion of one of these.
Image

Once together, using my excellent MS Paint skills, it should look something like this:
Image

I think it should work really well (unless I'm missing something which happens from time to time). The only aspect I don't like about the device, is how visible the top portion of the clamp will be, I'd like it to be almost invisible. Unfortunately, for this to happen, I think I'd need to get into welding, which as stated above, also has its drawbacks.

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 Post subject: Re: Muffler Mounts
PostPosted: July 17, 2015, 4:16 pm 
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A swinging hanger like Chuck's is always going to be best, IMO. Since I first posted this, I've already had to replace the compression bobbin when it split apart last summer. It only lasted about 5000 miles. The current one has gone 7000 miles and it's still okay, but I think the pipe expansion stretches it beyond its designed shear limits (which according to McMaster-Carr is only 1/8"), so it's probably about to go.


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 Post subject: Re: Muffler Mounts
PostPosted: July 17, 2015, 5:10 pm 
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I have used these high temp rubber exhaust mounts on a car and they work well, I drilled out the U clamp and thinned down the nut so it fitted inside the base of the clamp, then trim off the excess thread.

Image

Image

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 Post subject: Re: Muffler Mounts
PostPosted: July 20, 2015, 4:57 pm 
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And . . . in the 72 hours since I last posted, the bobbin has broken again. Could have something to do with the engine starting to run on three cylinders over the weekend. Very shaky.

Those clamp hangers look like they'd work pretty well, but like a great many exhaust parts that are normally hidden under the car, not the most attractive.


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 Post subject: Re: Muffler Mounts
PostPosted: July 20, 2015, 5:40 pm 
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Bummer Nick. You spoke too soon. I'll take this opportunity to say.........absolutely nothing about my mounting method. Just in case. You understand :roll:

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Visit my ongoing MGB Rustoration log: over HERE

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