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Exhaust springs

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4.3K views 20 replies 10 participants last post by  Old Cafe Racer  
#1 ·
Any of the racing folk using springs to fix pipes to heads? I'm thinking of using this method for a set of T140D downpipes which need welding anyway, so attaching hooks for springs wont be a problem.

What I'm wondering about is the best way to fix the springs to the head. Drilling through one fin would be asking for the spring to saw its way through in time, I'd expect. I'm wondering about drilling through several fins each side of the port and dropping a stainless rod down the hole (leave bottom fin undrilled to retain it), and attaching the spring end to the rod. But I'm guessing this has all been done many times before and there are tried and proven methods?
 
#2 ·
I've seen single fins drilled. I've also seen adapters that mount to the head and they hold the springs that retain the header.

I like your idea of a pin engaging more than one fin. But I would not use a pin. I would use a threaded screw and small spacer or even perhaps a spacer/tab to hold the engine side of the spring. Using a threaded fastener and tapping the fin would preclude relative movement between the "pin" and the fin and the resultant wear. The pin itself would wear and that could be replaced when necessary.

regards,
Rob
 
#3 · (Edited)
as Snakeoil's suggestion but add a bit of stainless tube so that it is the collar that wears, but the screwed fixing remains ok?

Or ( if I can post the picture) I saw a bobber with the pipes held together at the top by two welded brackets, and probably a tapped tube that was bolted into, or a threaded rod covered up by a tube.

You can also use the T140D collars that tap into the head (T1240 shop) but I like roses and the collars mess this up
 
#4 · (Edited)
I don't want to use those T140 shop collars, but I would like to know the dimensions of the threaded holes they use. Another idea I've had is to weld collars (ie: big washers) to the pipes so they sit maybe 20 thou away from the head when the pipes are fully home (maybe home against a composite exhaust sealing gasket if I can find one that fits - Guzzi ones can;t be far off?). Then have 3 countersunk screws at 120* holding the collar to the head, and finned 'roses' abutting the collars just for ornament.

I'm thinking 4mm or 3/16" would be the max diameter for threaded holes. I'd prefer them to be Helicoiled but I'm not sure whether there's enough 'meat' to play with.

More thinking needed, but if anyone has any ideas, I'd be glad to see them, thanks.
 
#6 ·
there may be enough "meat" for your 3 proposed fixings -- there is that conversion kit available for "push in " pipes that uses an ali collar fixed in a similar manner with 3 screws -- however there is more metal available on the push in head as it hasn't been threaded for the stubs
-- can i ask why you don't want to use the T140D standard fixing or the "usual " stub fixing
 
#7 ·
It is a push-in head I'm talking about. The idea comes from having T140D pipes and a push-in type head. The pipes are going to be painted black, so chrome damage from welding isn't an issue. I don't know how the std T140D fixings work, but don't they rely on a threaded collar of some sort? If so, that's ruled out on cost grounds (and finding anyone to do a proper job of it grounds). Same goes for getting it converted to standard stub fitting - I can get it done, but it'll cost me at least ÂŁ100. And then, T140D pipes will need extra work to make them fit, as these are push-in!

I've looked at the Shorpshire Classics/T140 Shop site and can see how their system uses 3 screws, but I don't like the look of it (plus I don't want to deal with that shop). There really isn't much meat where its needed - I'd want threaded holes Helicoiled and either Loctited studs & nuts, or screws that can be removed & replaced many times without high risk of those tiny threads getting stripped. There can't be space for more than a 4mm stud/screw if using a Helicoil as well?
 
#8 ·
HI john - I see where you are coming from -- I am working on a T140D at present -- as far as i have found out about the way the pipes are secured to the head is ;;; -- As i understand it the head has the same threads in the exhaust ports as the stubs for the "push over" pipes - instead of using those threaded stubs there is a combined threaded stub with a finned collar of some sort - a copper compression washer is crushed onto the "push in " pipe as the T140D fixing collar is screwed in -- cant confirm that this is exactly correct as i haven't got any exhaust parts yet (the previous owner dumped the exhaust as it was "rusty") --- its not a system that i am happy with due to the possible wear on the threads in head from repeated fitting / removal ( just like your concerns with small fixings into the head itself)
my own preference is for push over pipes --- I have never liked the push in pipes --
However you end up deciding to fix the pipes to the head you will need some fairly rigid fixings from the pipes to the frame further down the pipes to be sure they don't exert too much "waggle" force back into the fixings to the head
 
#9 ·
My bike has those shop collars, fitted by the previous owner. He said he was a bit nervous drilling and tapping the holes!

Obviously they look quite a bit different without the fins but do provide a secure fixing. I agree with the comments about possible stripping of the holes if disturbed a number of times but hopefully I won't have to do this for some time and will be really careful.

I note that my bike also has a balance pipe which I guess helps with keeping the headers in place i.e. doing a similar job to the bobber example though not being able to be tightened together as much.
 

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#10 ·
I did, once, fit a set of T140D pipes to my old T140 which had a normal push-in head. I didn't even know about the proper T140D fixing, and I just fitted them as normal, shoved into the ports with a bit of Holts Firegum paste. I made sure the brackets to the engine stud were as secure as possible, as that was the only positive fastening (no silencer was involved). I never had any problems, not even any banging on the overrun. I was surprised years later when I learned about the 'D''s screw-in collar arrangement!
 
#11 ·
if you're running the pipes with a bottom fixing and have some kind of solid fixing between the pipes at the tops, I would think that TWO point fixing would be fine.

I don't agree with TT's opinion that the Photo that I posted is " a lot of work" as so long as you have the tangs for the springs, they can be made for a small screw/bolt. Then you just need a bit of stainless rod/tube tapped internally to act as a across brace.

It is just doing what the balance pipe did.

Maybe the bottom exhaust mount could be more like a small bit of corrugated iron?
Two bits 4" long that sandwich the pipes and were held together with a stud would hold them pretty firmly? Think an M over a W.
 
#13 ·
John -- as you say that in the past you have just used the T140D pipes "pushed in " and sealed without problem - how about you stick with that and just add tabs to the pipes and have a through bolt (like in the pics earlier) to pull them together - that would hold them tight together and into the head -and allow the use of an exhaust rose -- just a thought !
 
#14 ·
Yes, not a bad thought either. I didn't have problems when I used them as normal psh-in pipes years ago, but back then I didn't even realise the T140D had any different kind of fitting method. I suppose it was just learning that they 'shouldn't' work like that, which made me want to do a better job of it. I still like the springs idea though...
 
#15 ·
John, I use the T140D screw in roses, (stainless), but after I bought them the supplier put a note in the box saying the copper washers were no longer available! Why send me the collars knowing I wouldn't be able to use them without the copper washers? :mad:

Anyway, I bought some copper olives from a plumbers merchant and they work a treat, as you tighten the rose up by hand you can feel the header pipe getting nice and firm, then just nip up with a c spanner and job done.

I kow this is going off topic but just thought I'd share my experience with the D set up :)
 
#16 ·
Hi guys, I have a Yamaha DT-1, which is a 250 2-stroke. The exhaust on it is fastened by factory design with two steel springs, which hook on the cylinder side to a small hole drilled in the fins on each side of the exhaust outlet. There is no balancer on this bike, and as a 250 2-stroke thumper it shakes quite violently. If the springs haven't sawed through those fins I doubt they would ever do so on the Triumph. I would definitely ensure that there's just enough spring pressure to hold the exhaust in, wouldn't want to overdo it. FWIW, on the exhaust side there are two loops of steel welded onto the pipe, which the springs hook onto.
 
#18 ·
Don't know if this is any use to you but below are photos of the exhaust spring attachments on my old Ossa SDR - a 250 two stroke single with a lot of grunt - the motor would ring like a bell when pushed hard so lots of vibration.

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It uses 2 square section rings that go through a fin and the springs hook onto them. The fin is cast slightly thicker at the point where the holes are.

No wear I can see in the fin holes.
 
#20 ·
Hey, if we're breaking out the pictures... here's a closeup of the Yamaha DT exhaust flange. I know Yamaha went to a push-on exhaust held in place with the springs because the 2-stroke had such hard pulses and shaking that the bolt-in exhaust adapters were fracturing. The springs are readily available, I think I bought mine off ebay, or maybe http://www.nwvintagecycleparts.com/. They carry vintage japanese parts.

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