Yet another collector box thread...

VanguardontheLav

VanguardontheLav

Hero member
Location
Cambridge, UK
Hi all,

No wonder the Sprint was noisy coming back from the Island...

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'Twas a bugger getting the short broken ends out of the silencers...

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Now, I know all about having the system mounted properly and nothing under tension, and I admit that earlier collector box failures could be down to that, and the Island WAS incredibly bumpy, but to be honest I'm a bit pissed off with my collector boxes breaking. In this case, the system was fitted by Keith (who knows what he's doing - you can see the lambda sensor mounting he fitted to it) so I really don't think it was under strain.

I remember robjota saying some time ago that he had a collector fitted with a slip fit and springs. I was wondering whether that made sense to do the same... The design I was thinking of, would have a slip fit joint in the "1" part of 3-1-2, i.e. a front 3-1 and a rear 1-2, joined by a slip fit joint and springs. What do people think?

If I were going to do that, the other thing that strikes me about this collector is the narrowing at the point where the three goes into the one. That just 'looks' too restrictive to me. If I am going to have a special one made up, I was wondering whether to 'smooth out that part. Same goes at the one into two. Again, what do people think?

--
Dick
 
Classic failure.  My original big-bore collector has a small reinforcing plate welded across that failure point (as well as the front 3-1 section), presumably to reduce the risk.  I wonder if your rubber mountings (either silencer hangers or engine mountings) are loose / worn / cracked, allowing more movement than normal?

It may look restrictive, but the '1' bit of the collector is critical to engine performance.  Whilst the later pressed item used on RGS series is reckoned to be better from a gas flow perspective, I'd stick with the same cross-sectional area.  There are several aftermarket designs available from the usual sources...Wolfgang has one that seeks to leverage the venturi principle: Lothar has posted about his specially designed 3-2-1 and the performance boost it delivered.  Bigger ain't always better!  :)
 
I had mine on the RGS go in Invercargill NZ, about as far away from home base Christchurch.
It was a very noisy ride back.
I went for a set of stainless headers and collector from Wolfgang, work very well with the stainless "Jota" cans.
No problems at all now.
 
The joys of stainless steel eh? Stainless is a poor material choice for this application. If you're going to get a new one made, do it in mild steel. It won't look as shiny unless you chrome it, but it'll last longer. Material choice is one of the reasons I bought a Redax/Pipemasters exhaust system. The headers and collector are ceramic coated mild steel. The silver ceramic coating looks like a satin chrome or stainless finish.

There seem to be some commonly held myths about stainless steel. It's not constant strain that breaks stainless, otherwise yacht masts would be falling out of boats all over the place because of rigging failures. Stainless is quite happy to be under constant load. Think of all the stainless bolts in the world that are all done up tight and under load all the time. They don't spontaneously fall apart. So it doesn't matter if your exhaust system is under load when you bolt it up. In fact, it may even be a good thing because it might reduce vibration movement.

What stainless steel doesn't like is any kind of cyclic load because it work hardens and cracks. The headers and collector are all solidly mounted to the bike via the exhaust port clamps. But the muffler cans are free to move a little bit because of their rubber mounts. So they bounce around on the ends of the collector box spigots, imparting cyclic loads to both the collector box and muffler spigots. If you have a stainless system, you might be better off ditching the rubber mounts and making up solid equivalents.

Just getting back to the yacht rigging example mentioned earlier ...  Being a sailor, I see a lot of stainless steel boat fittings and rigging. Whenever I see a yacht with stainless steel rigging wire that's been set with insufficient tension (leeward shrouds hang loose when beating to windward) I think "there's a rigging failure waiting to happen". The limp rigging flaps as the boat punches into the sea, bending the stainless rigging wire back and forth, work hardening it all the time. When the boat goes on the other tack, that wire comes under a lot of tension. Sooner or later it'll let go. Rigging failures very often result in the mast coming down, which is a bit of an inconvenience to say the least.

Cam
 
If you have a stainless system, you might be better off ditching the rubber mounts and making up solid equivalents.
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That sounds like quite good advice Cam.
Ta.
Two things I'm going to check when I get home are the torques on all the isoelastic engine mounts on my 120's and also the state of the collector boxes.

As an interesting aside to Dick's collector box problem, my Jota 120 has a stainless steel exhaust system throughout. On the 400 mile ACU rideout in July (which Dick was on as well), it was the mild steel triangular plate holding the exhaust to the rear footpeg that fractured and broke. I returned home all tie-wrapped up with no ill effect.

So, it just goes to show that vibration can do damage anywhere, no matter what the metal.

FYI. To reduce engine vibes on 120's, the gurus say the recommended torque settings are as follows:

Isoelastic silentbloc to frame:    30 - 37ft/lb
Isoelastic silentbloc to engine:  37 - 40ft/lb
Swingarm nuts:                        53 - 60ft/lb

Check yours now.....
Happy vibe free riding.  :D
Cheers
DoC!
 
 
Hmm ... yes, I forgot about 120s having rubber mounted engines. Probably best to keep the rubber mounts on the exhaust cans on a 120.

BTW, Malcolm Cox is having a batch of collectors made from mild steel (chromed, galvanised, or finished to your requirement). They will be made to fit standard sized headers and mufflers. Not sure whether he has them available for sale yet, but they should be soon.

Cam
 
Cosi said:
Galvanised?  :o :o :o
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You can hardly see the suckers under the bike, and most are filthy anyway. maybe galvanised will last longer especially if coating is inside as well.
 
trust me Davo, once youve got the fucken thing running you will spend a lot of time lying on the ground looking under it for various reasons  :D
 
The fracture of the collector photo'd looks like like a brittle fracture (jagged edges), and looks like it is in the 'Heat Affected Zone' of a weld. Chromium turns into a brittle substance 'Chromium Carbide' at the weld periphery when it cools.
Cyclic loading through heating and cooling has likely done it in.

There are ways to prevent this, so it is down to material/weld procedure.

I'm sure a qualified TIG welder will correct any of my errors!!!

 
Dick,

do yourself and the bike a favor and get a 3-2 system made (without the -1- in the middle) like i did. The collector you used is designed so badly, I almost can't tell... Look at the place where the 3 join together to get into the "double chamber". It is almost like trying to breath while hanging in a robe that's around your neck... Same at the end of the "expansion chamber"...
Then at the end of the -2 part it starts into the pipes that go to the mufflers with a diameter of - say - 34 to 35 to go down to 32 - outside diameter... another bottleneck! This will never work properly and signs it doesn't are thae fact that it looks as if it exploded...

cut the 3-part at the point where it allows to weld 2 32mm (or 34mm if you can) tubes in, make sure that where you weld the 2 together you make a smooth transition inside and than go straight backwards with a small angle like 5-10? so that you can use a maximum of 45? to join these two individually with one of the mufflers. See:

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Well, after a long chat with Malcolm Cox about what to do on this, he has loaned me the collector (original Laverda part) off his Corsa - which fits much better than the Keihan one, surprise, surprise with no strain. Much smoother flow to its lines and mild steel of course.

The box fits well to the Keihan headers, though Keith had added extensions to the downpipes to make them fit properly and these were essential. I had a few (unrelated) problems fitting it on Saturday, so didn't get finished before I had to leave to go and play rugby... (The clips turned out to have damaged threads in the allen keys so they wouldn't open enough to go over the collector at the front which is slightly bigger outside diameter than the Keihan one. I had to take them off again and clean the threads out to make them work. Also I had some new header O rings, composite rather than copper, and they didn't compress like the copper ones so the header clamps were marginal and the pipes didn't quite fit - it's all highly critical isn't it?)

So, with new copper rings and good clips I then took a couple of hours getting things right, starting from the back end. When I was cleaning up the old connector I was puzzled by the rust on the rear outlets which implied that the silencers hadn't slid the whole way up them... turns out that was right, they only slide on half way if they are to fit correctly! Anyway, after careful fitting, it all looks and sounds great and nothing under any strain, so time for a long ride: bike improved in every way, quieter, smoother throughout the rev range, and faster at the top end (130 v 125 on my usual test road.) So I'm VERY impressed.

Will keep you informed of any future progress!

--
Dick

 
Result!

Now we need Malcolm to get his finger out and confirm when he'll have a batch of collector boxes available to fit to his (very nice) chromed steel silencers ;)
 
He's getting header pipes made, just having trouble finding someone to make the bends to his satisfaction.
 
Looks like it's my turn!! Coming back from Urbenville to Woodenbong today on the worlds bumpiest piece of crap road except the Legume road apparently, all of a sudden argy was a lot louder and much clanging of metal bits. Pulled over and yep the collector box was in pieces.I'll get the local muffler shop to do a shonky weld up until Malcolms mild steel ones are available. Now some of the cracks were very grubby so I suspect it's been cracked for some time, might answer the metallic vibes at about 1500rpm that I couldn't work the cause of. As for others it was a very noisy ride home!

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drikko said:
Looks like it's my turn!! Coming back from Urbenville to Woodenbong today on the worlds bumpiest piece of crap road except the Legume road apparently, all of a sudden argy was a lot louder and much clanging of metal bits. Pulled over and yep the collector box was in pieces.I'll get the local muffler shop to do a shonky weld up until Malcolms mild steel ones are available. Now some of the cracks were very grubby so I suspect it's been cracked for some time, might answer the metallic vibes at about 1500rpm that I couldn't work the cause of. As for others it was a very noisy ride home!
Click to expand...

If yer welding doesn't work out I might 'ave one to suit... Won't be any worse  :D
 
So red's ones are made by Pipemasters who are 200 metres up the road who I was going to take this one to fix to anyway. So I'll get them to make a new one in mild steel.
 
Red tells me he has a pile of shitty ones in a box somewhere. Got one over to me that will do the trick till Malcolm has his made.
 
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