Exhaust

Hi All,

Just thought i'd share with everybody what i've been upto over the last couple of days;

Exhaust templates made out of cardboard and marked out onto sheet steel

Don't try this at home on the dining table 'the wife was out'

Now the tricky bit after cutting the patterns out of sheet steel, bending them!



phew at least it looks like an exhaust.

Regards Mark

Hi Mark,

You have been busy and looks a good job, if you dont mind me asking how did you manage to roll it?


Eddie

I agree with ED - you must have a pair of rollers to do such a nice neat job.

What formula did you use, you been using your own ? or from what book or ? - please tell us.

looks like you have done this before !

Has Trevor's posts influenced your design, at all, or helped. please say ?

some one recently asked on here about the type of steel to make exhausts out of,

what sheet steel have you used , R? or and what gauge or simply thickness.

regards Derek.

Hi Derek, Eddie

Yes that's right I've invested in a 12" metal roller (slip rollers), only found out about these on monday. watched a few you tube clips and believe it or not this is the first time i've ever used them.


RDG Tools or Ebay Item number: 370483299413

The formula i've used was given to me Brian White. Very helpful as it works everthing out for you.

I've used 1mm sheet steel, I don't know what others use but I think I might use 0.8mm next time (lighter and easer to bend).

reagrds Mark

Would you care to share the formula ?

I have tried old Bacon and Bell ones with mediochre results

Hi Mark,

Thanks for the info and pics, looks a very nice job for your first go at it.


Eddie

Great stuff Mark, like the mini rollers how much?(scrub that just found em on ebay, that's a good price) Think my brother Ray rolled his around a scaffold pole welded to a car ramp.

You know what will happen next.........?





You'll be taking orders or you could roll pipes for swaps



Tony

Looking good Mark. Just one question, how did you manage to bend the coned areas of the exhaust? Been pondering that all day actually haha!

T

Hi all,

Tim, in the picture of the roller you can't see it, but their is a third roller behind the two front ones, now to make a cylinder the third roller is adjusted up straight so it bends even hence you produce a cylinder shape, now to bend a cone the third roller 'bending roller' is adjusted unevenly (for example 1/4" on left and 3/4" on right) so when the steel is rolled through it makes a cone shape. Hope that's clear!

Tony, orders are now being taken or if anybody wants a pipe for Bantam ride

John, sorry that was a bit misleading the formula works out the cone shapes, you still have to entre the variables to obtain the size of pipe you want.

Regards Mark

OK, about the cone shapes.

But did use use a modern formula to design or get the size of the pipe ?

johnSbantam wrote:

OK, about the cone shapes.

But did use use a modern formula to design or get the size of the pipe ?

John,

Looking at the printout on Marks table

The design Brian uses is based on Mick Scutt BRC Mag 134 Re: overall length and the rest on Yamaha Paper 71004 1968

James

Hi Mark,


Out of interest how are you intending to fit the pipe to the barrel?



Eddie

It is handy to have your own welding equipment and advantageous to test small variations on the chosen pipe dimensions.
...
Well, that was my experience with a very low cost Bantam engine (Contact Breaker ignition and long stroke) tuned for a good torque-back-up & reliability. I spent a lot of hours practising at Brands with our chosen pipe dimensions varied by a small amount each time, finding out the revs at which the pipe became effective and the power band width at given conditions etc... etc... -- agonisingly time-consuming yet well worth it.
...
Colin Neil, brother of my engine-builder-tuner, Derek worked for Joe Ehrlich at De Haviland and provided the formula and I made several pipes and bits-of-pipes to eventually develope the exhaust pipe for Icarus-1. By having interchangeable sections of exhaust pipes --that could be assembled behind (or AFTER) the diffuser -- that included varying sizes of tail-pipe -- I could ring a number of changes in a Practice day at Brands. In those days 4-half-hour sessions were available to the bikes with sidecars having only one, half hour and cars the same as us bikers.
It is surprising how much an inch here & an inch there -- plus small differences to the major diameters of the Diffuser, Nozzle & tail-pipe dimensions can make to the width of the power-band and to when the pipe becomes effective.
One experimental pipe had a telescoping parallel portion that enabled the determination of the diffuser to nozzle distance -- that actually proved the theoretical data to be an ich too long.
...
The first time Andy Boyle gave me his 250 ABS (Alpha engine) to try out at Brands he was disappointed with the rev readings I reported to him and redesigned the exhaust pipe, which -- although it looked wrong -- I made and fitted. Fortunately I took the original pipe because the very short looking pipe would not work with me on board no matter the changes of gearing I tried -- it just burble-burbled in firsts gear never getting speed enoughto change up. I went around and around getting more embarrassed & frantically frustrated as the day went on. (After all, it had cost me 10Bob a session -- two sessions so far...) so I fitted the original pipe, changed the gearing and managed to frighten myself after all. It was another case of small changes in the dimensions that got the engine working well enough to match John Senior´s Greeves Silverstone at Llandow -- I have to admit to being beaten by half a wheel into 4th place with us two not far behind two Japanese machines. Nice to feel I was second British bike in taht race.
...
I doubt that this has been of any use to anybody but a bit of nostalgia is what I allow myself every so often.
...
Go well and keep well,
Cheers,
JayBee.

Hi Mark,


I tip my hat to you on doing the cone's, i have a set of these now and its not as easy as it looks, will keep on practising


Eddie

Hi Eddie

It's not as easy as it looks! but keep at it it's very satisfying once you've made one.

Regards

Mark

Hi Mark,

Yeah im gonna keep at it, all a bit of trial and error. Hope the rest of the bike is coming along.


Kind Regards



Eddie