Thermal expansion

[Worty]

Folks, a question.

Is it possible to fit a 45mm pipe into a 41mm hole by heating one pipe and freezing the other?  What's the best I can achieve with a freezer and blowtorch?

It's an exhaust pipe conundrum.

I can cut the silencer back to a larger size as it's tapered, but I don't want to go overboard.

[limeyrob]

No, you have perhaps 5 thou of leeway.  Can you use a short length of 41mm OD pipe.
If its chrome forget the blowtorch and the idea of heat plus freezing always sounds great but the moment the 2 parts touch they equalize temp and its all over.
If you watch a bearing being frozen and dropped into case it is dropped, it can't be pressed because if its stops halfway it equalizes and gets stuck solid.
Explain the taper on the pipe.

[Worty]

What I mean is the diameter of the silencer increases away from where it joins the downpipe.  Cutting back on the silencer will allow extra room for the pipe I have.  I do have a couple of other ideas, it's just a shame the silencer wasn't a larger bore as I could have used inserts.

The problem has arisen because POs cut the front pipes too short when they were dispensing of the original item (all welded together in one piece.  This means that the slip on mega fouls the sidestand, and has led to a dent in it.  My idea was to extend the length of the downpipe, past the sidestand, then into the silencer, which will then sit at about the same length as the originals.

[RichardL]

It seems like you might need something like this: https://www.jpcycles.com/product/emgo-muffler-and-exhaust-pipe-reducer-set?sku_id=10231588

Though, from your description, I think this would put the end of the exhaust inside the pipe, instead of the standard arrangement. I believe this would mean having to slot the pipe so it could be clamped over the exhaust.

Richard L.

I read your latest before posting and think what I've said here is still about right (since I'm only hypothesizing, anyway).

[Worty]

Cheers Richard.

I can slot the pipe further up as you say.  Basically taking a little from the silencer and making it up with straight pipe.  It was whilst I was thinking on that I came up with the idea of using heat.  Silencers are going to get a few coats of heat resistant paint as they were too scruffy to put them back as is.

It'll probably cost me as much as buying a new pair of cheap and nasty silencers (can get a pair of tulips for £70), but I don't like tulips or the megas I have on, so I'm persevering for now.

[RichardL]

To clarify my idea, the appropriate reducer diameter from the link would go inside the pipe, then, the custom-slotted pipe would be clamped over the whole thing together with the exhaust inside the reducer.

Richard L.

[berger]

worty you have just thermally expanded out of my grey matter any sense that might have been in there, the nonsense can stay .

[Swarfcut]

    ebay has a fair few reducers, mild steel or stainless. Must be something off the shelf to do the job.

  https://www.ebay.co.uk/sch/i.html?_from=R40&_trksid=p4432023.m570.l1311&_nkw=exhaust+pipe+reducer&_sacat=0

 Swarfy.

[Worty]

Cheers guys, but rather than wanting to reduce bore size, I need to increase it.  I'll try to explain:

Downpipe is double skinned, so can't do much with the i/d, the o/d = 41.4mm.

The connecting tube needs to fit OVER the downpipe, so needs to be, say 42mm i/d, which, in turn means the o/d is the i/d + metal thickness x 2.  Assuming it's 1.5mm, that'd make the o/d of an i/d 42mm tube 45mm.


On the silencer end, the o/d is around 44mm and the i/d is 41mm.

So, how do I get a a i/d 42mm, o/d 45mm pipe fit over or into an i/d 41mm, o/d 44mm silencer.

There are some 'expanded end' items out there which means the i/d of the expanded end is the same as the o/d of the rest of the tube.  If I could get a double-ended expanded pipe of 45mm, that should fit over the downpipe and silencer, but I'd have to use a reducer at the downpipe end.

Good bedtime reading is this, just don't show it to Bergs

[Swarfcut]

 Exhaust pipes generally overlap so that the gas flow has no means of escape, think of how roof tiles overlap. In the case of exhausts, a smaller pipe enters a bigger pipe, not a larger pipe over a smaller one. Consider what is on offer, something will do the job.

 Swarfy.

[morris]

Pipe expander?
https://tinyurl.com/4zr7zhpy

[Worty]

Exhaust pipes generally overlap so that the gas flow has no means of escape, think of how roof tiles overlap. In the case of exhausts, a smaller pipe enters a bigger pipe, not a larger pipe over a smaller one. Consider what is on offer, something will do the job.

 Swarfy.

This is what I hope to achieve.  Downpipe goes into slight larger mid section, which then goes into the silencer.  A pipe expander is definitely an option, but it's probably going to be a 'used once' tool if I buy one (not too expensive on Ebay).  the only other option is to judiciously cut  back the silencer to a wider section (about 60mm) so it's a fraction off fitting, then heat the pipe up with heat gun and blowtorch so it slips in and shrink seals.  If I do this right, it may mean I don't need a clamp on that part of the pipe, with only one at the other end.  This would be a lot tidier if it goes well??

[limeyrob]

If its painted anyway I would be inclined to weld it all up into one piece.  I can image this all coming loose and rattling on a run.

[Jules]

Worty, have you talked to a good exhaust/muffler shop? its just that looking at all those bits on Ebay, a good exhaust shop should be able to flare and/or bend an adaptor to precisely suit your needs using 304 SS, which you could then polish up a bit too if you wanted...not sure what they would charge you mind...

[Worty]

I have thought about talking to a couple of local garages, but they would have to charge, and at around £60 per hour minimum, it wouldn't be worth it.  I could buy a expander set for around £20 but, again, I wouldn't really use it after this.  I wanted some non-dinted silencers that I liked the look of and would look right on the bike.  The pipes were £38, £16 for a length of stainless, and 12 for paint.  This puts me at £66 which is just under what I could pay for a couple of chromed tin cans from China.  Given that I want to lengthen the mid section due to POs butchery of the front pipes, it was always going to add a bit to the cost anyway.  Reckon I'll experiment with cutting the silencer down to a slightly wider i/d and see how it all fits together.  Like Rob said, a dab of weld may be needed but I'll have a look to see what my options are.

I think I like the challenge of adapting things and seeing what happens.  Even if all doesn't go to plan, it's been a bit of fun trying to make it work.  Of course, I can retain the s/s pipe for any silencer that goes on, including the megas I have on at present.