Topic: CB500 4 into 4 sandcast aluminum muffler build (maybe?)

[wolf550]

So I started working on a muffler for the 4 into 1 I have on the frankenstein bike but once i cut off the exhaust entrance and put on a connector to the exhaust it would have looked like any other muffler really. So...
I scrapped that project and Ill just get an aftermarket for it but since I have this top right side muffler already in fiber glass, the most logical thing to do is cast this up and see what comes out of it.
If it casts?
then I will have to see about getting it brazed together.
if that works?
then I will have to cut up the rusty muffler off the pipe and slip it on.
then Ill have to go ahead and do the other 3.
not sure how thick or thin these will have to be to work but I will get to that if they cast huh?

Ok so next on the list is to tape these back up and make a complete fiberglass muffler to re-cut so they mate up. I couldn't do this while on the metal muffler because of the extended weld that connected the two pieces together.

[wolf550]

after working on Frankenstein for awhile getting the 750F rear assembly completed I decided to go ahead and dissect the muffler.
when I got through both sides of the weld it just seem to fall off the exhaust pipe!
I think it was being held together by the rust in it.
I knew there would be some of the pipe inserted into the muffler but it seems like alot.
I don't know if I could slide a muffler on the pipe if it was brazed together.
I think it the two pieces would have to enclose the pipe and then welded?
or I can just cut off the extended swiss cheese pipe. this would allow me to make it slip on with some sort of muffler insert that wedges in between the pipe and muffler like the 4 in 1 has.

[wolf550]

after making the first fiberglass muffler mold it was not coming together like it should due to starting it off with a fabric lining to build up with the fiberglass. when I cut it in half the thin molds twisted some. so I went ahead and did another with just fiberglass this time and it is holding up better with the HVAC tape. I went at the exhaust pipe with the angle grinder to get rid of the tabs that were attached to the baffles inside. after making the aluminum castings I have to see how difficult it is going to be to make the 3 chamber baffle. since this is not my expertise I may have to end up with the straight pipe to baffle packed with fiberglass as grcamna2 mentioned earlier.

Once I get both sides taped up I have to make the sand mold boxes and try making a sand mold with these and see what happens.

[wolf550]

while waiting on my exhaust from bobcovintage to arrive I finished up the boxes for the muffler molds.
Im using a 1/2 inch thick boards to save on the weight.
after the bottom half was complete I saw that I didn't have enough sand to finish the mold all the way but went ahead to split them and see what comes out.
lucky me, the two halves didn't get stuck together and the muffler popped out of the sand mold complete.

since this was a different type of casting that is more long, uneven that my past pieces I was trying a different method when splitting the mold this time going for a horizontal release instead of the vertical because it is so long but since I am out of sand I will have to make do with going vertical and making the lower sand mold only and inch and leaving the top mold 4 inches.

almost there. after getting the shorter mold made I should be able to give this a go with a casting. we will see...

[calj737]

While I applaud your creativity, I have to say I think using aluminum for an exhaust is contrary to wisdom. The native properties of aluminum will reduce the exhaust gas temps, thereby reducing scavenging, probably not withstand the thermal expansion/contraction without cracking prematurely, and generally reduce the performance of the engine.

Aluminum is great for intakes, terrible for exhausts. On the intake side it helps reduce the air temp of the inbound air by extracting the heat, which is desirable. The opposite is true for exhausts.

Just saying...

[wolf550]

yeah I have no idea what this is going to do or if it will work to any extent but it sure is fun finding out what will happen.

we will see

[calj737]

yeah I have no idea what this is going to do or if it will work to any extent but it sure is fun finding out what will happen.

we will see

along for the adventure!

[Don R]

 Eastwood inside the pipe exhaust paint would repel some heat. I use it on my Yamiya 4-4 sets. 

[754]

Plenty of aluminium cans on modern exhaust on 4 cylinder bikes..

[Alan F.]

Yup, fear not. You're on the right path for mufflers but no, not head pipes.

[Bodi]

Reminds me of a university barbecue many years ago. The Engineers had a charcoal grill made from several "oil" drums. The Physics dept came with a very fancy new grill fabricated from welded aluminum plate.
Anyway, the Physics guys were crowing about how amazingly superior their new BBQ was. Until they lit the charcoal... once the fire got going good the aluminum bottom melted and dropped all the coals on the ground.

I think aluminum headers would melt, it isn't so unusual to see headers glowing by the ports. OK for a muffler, most likely.

[wolf550]

I am hoping where the muffler and header pipe attach that it would not melt.
I remember Marissa making those aluminum header stays for her 500/550.
I don't think she gave an update if they melted off or if they withstood the temps.

as of now I have to make a thicker wooden box for the sand molds.
when I remade the bottom mold about an inch and half height the sand bulged out the wood after putting the top half on to fill.

i think after this project I will have to put the aluminum stuff on hold until later spring and start clearing out most of the extra CB parts.

[grcamna2]

I like to see what the insides of the OEM muffler looks like,those parts could be custom made by a person with as much creativity as you:imagine using stainless steel to build some Real repros.The mufflers could last Many more years than stock. 

[Alan F.]

Carbon steel melts at 2800F, aluminum at 660F.
https://www.metalsupermarkets.com/melting-points-of-metals/

Exhaust temps are what? In the 350-400F range on the high end? I'm not sure, but I doubt it'd be a big worry using a stock length head pipe.

Keep calm and carry on with your ideas, I'm not an engineer but I say your premise is very sound.

In a pinch some alloys melt a little hotter and have other properties that give them advantages over other alloys, I'd suggest using that.

[wolf550]

that is good to know.
so far this trash can forge has melted:
aluminum
brass
copper
and part of my 1/4 inch thick steel rod used for blending

im guessing aluminum is a lighter material than the others

[Alan F.]

Sounds like a good time, I'm hoping to play around with that stuff someday myself.

I can't speak to how aluminum behaves compared to brass or copper. Perhaps there are some specific forums to join?

[calj737]

Carbon steel melts at 1425F, aluminum at 1221F, exhaust temps are what? In the 350-400F range on the high end? I'm not sure, but I doubt it'd be a big worry using a stock length head pipe.

Keep calm and carry on with your ideas, I'm not an engineer but I say your premise is very sound.

In a pinch some alloys melt a little hotter and have other properties that give them advantages over other alloys, I'd suggest using that.

aluminum melts around 700*, but the oxide layer melts above 2700*. Exhaust temps on these bikes can easily surpass 500*. If you doubt that, look at chrome or stainless headers where they turn blue. That is an excellent example of temperature. You’ll see how hot based upon the material and color chart.

For mufflers, sure, aluminum canisters are fine. For headers, not so much due to the temps.

[Alan F.]

Corrected, my fault for taking guugle answers as facts...

[SOHC4 Cafe Racer Fan]

My friend Isaac Siegl of Speedy Siegl Racing (https://www.speedysieglracing.com/) makes lightweight aluminum parts for motorcycles, INCLUDING exhaust flanges for Hondas, Ducatis, Moto Guzzis, Triumphs and Yamahas.  The exhaust flanges can easily withstand the temperatures of air-cooled motors.

I've had them on my (liquid-cooled) Thruxton for the last 3-4 years.  No deformation, but remember these are aluminum billet, not cast. 

I don't think I'd go with aluminum headers.  They'd be much more fragile than steel, too.  Also, if you get a bubble in the casting, it could cause the headers to crack from repeated heating and cooling cycles.

IMG_2494 by Donald Leonhardt, on Flickr

IMG_2495 by Donald Leonhardt, on Flickr

[calj737]

My friend Isaac Siegl of Speedy Siegl Racing (https://www.speedysieglracing.com/) makes lightweight aluminum parts for motorcycles, INCLUDING exhaust flanges for Hondas, Ducatis, Moto Guzzis, Triumphs and Yamahas.  The exhaust flanges can easily withstand the temperatures of air-cooled motors.

I've had them on my (liquid-cooled) Thruxton for the last 3-4 years.  No deformation, but remember these are aluminum billet, not cast. 

No to mention those flanges are much, much thicker mass to deal with the temps. Tubing is very thin-walled comparatively and will not endure for long.

But there is still the fundamental scavenging issue with using a material (ally) as the exhaust tubing. It undermines the effectiveness and intent of the tubing (to remain as cool as possible for as long as possible to evacuate the gas).

[Bodi]

The clamps are not exposed directly to the exhaust gas, and don't get nearly as hot as the first bend of the header where they tend to blue, and glow red sometimes. I have used alloy clamps with no issues on a few bikes.

[scottly]

Carbon steel melts at 1425F, aluminum at 1221F, exhaust temps are what? In the 350-400F range on the high end? I'm not sure, but I doubt it'd be a big worry using a stock length head pipe.

Keep calm and carry on with your ideas, I'm not an engineer but I say your premise is very sound.

In a pinch some alloys melt a little hotter and have other properties that give them advantages over other alloys, I'd suggest using that.

aluminum melts around 700*, but the oxide layer melts above 2700*. Exhaust temps on these bikes can easily surpass 500*.

Aluminum melts at about 1200* F, or about 650* C.

[SOHC4 Cafe Racer Fan]

Good points, Bodi and Cal.