Rowley's 1/4 mile and the Magic Tube .

Status
Not open for further replies.
needing said:
Hi ludwig.
From your recent testing of spray nozzzles, running at 40 mph utilises only the pin holes and throttle slide cutaway for air:fuel supply. At this speed, there is not enough airflow across the flat top nozzle to raise and atomise fuel.
.
Click to expand...

What ???
On what basis do you make this claim ?

Try plugging up the pilot jet - as many standing bikes find has happened anyway.
The bike will then run SOLELY on the needle jet - and even idle in a fashion, if somewhat roughly (very roughly !).

The Norton booklets of old used to show the Amal carbs functioning in diagram form, across the 4 stages of carburating.
Anyone got a ready link to that ?, very informative.
 
L.A.B. said:
All production 850s supposedly had the balanced exhaust system (no idea if that applied to the test 850s?).
Click to expand...

We'd hope they tested with the balanced system, if thats what they ultimately sold !

A reminder we still haven't seen a genuine dyno chart showing the (claimed) advantages of the balanced system
over the old single pipes versions of Commando.
Perhaps not entirely relevant to this discussion - but they and cutaway spray tubes did come togther as part of the 850 package.
Even with the mutes installed the exhaust could have breathed out through 2 mufflers with the balanced-tube exhaust system.
 
Rohan said:
A reminder we still haven't seen a genuine dyno chart showing the (claimed) advantages of the balanced system
over the old single pipes versions of Commando.
Click to expand...

The only apparent "claim" was that the balanced system reduced noise.
 
L.A.B. said:
Rohan said:
A reminder we still haven't seen a genuine dyno chart showing the (claimed) advantages of the balanced system
over the old single pipes versions of Commando.
Click to expand...

The only apparent "claim" was that the balanced system reduced noise.
Click to expand...

The words more torque come into it too ???
That has been bandied about ever since.....

And, we could surmise, is why factory dyno charts of 850 output have been VERY conspicuous by their absence.
 
Rohan said:
The words more torque come into it too ???
Click to expand...

Who's words? :?

Rohan said:
That has been bandied about ever since.....
Click to expand...

Yes, lots of things get bandied about but was not a claim made bay the factory as far as I'm aware?

Rohan said:
And, we could surmise, is why factory dyno charts of 850 output have been VERY conspicuous by their absence.
Click to expand...

And the factory charts for the 750 can be seen...where?
 
Well, I'll have to study some bike stuff from 40 years ago, but at a glance, Norton Triumph BM and Guzzi at least all went to cross-balanced pipes back then.
Maybe it was entirely noise, but Dunstalls had made a noise about increased torque with them. (?).

Been done to death on here too, just one example thread on it.
pea-shooter-mufflers-mk3-850-t19066.html
No one shot it down - moderator and tech experts must have been snoozin....

And similar comment in there someplace on the NOC.
Again no one shot it down.
http://www.nortonownersclub.org/noc-cha ... /616885215
 
Rohan said:
Been done to death on here too, just one example thread on it.
pea-shooter-mufflers-mk3-850-t19066.html
No one shot it down - moderator and tech experts must have been snoozin....
Click to expand...

Whether the balanced system increases torque to any significant degree or not is still debatable, and the subject has certainly been "done to death" but, as I said, it was never a claim made by the Norton factory as far as I know-so there's nothing to shoot down? :roll:
 
Sure would be interesting to see dyno chart comparisons.
It almost defies logic that it could have totally no effect ?

Sure are a lot of deluded folks that mention more torque in google search too...
 
ludwig said:
I suppose most of us have seen this diagram :
Click to expand...

I haven't - where did you obtain it ?

And I'd question - What does 'effectiveness' actually mean, as one scale on that graph. ??

It shows the pilot jet going to near half throttle - which seems highish, but its down the bottom of the chart,
so does that mean its not so effective ?!
It also shows the main jet extending up from 1/4 throttle, which is not entirely my understanding of when it comes into play ??

ludwig said:
Where is the spray tube ?
Click to expand...

I suspect we need some dyno time to run a few different versions of carb setups.
And note the engine output, and especially note the air fuel ratios at various throttle percentages.
And throw a few varieties of exhausts at it, and see how the various carbs handle it.

Hey, Amals carburate great on a stock bike, this is all just navel gazing on a grand scale.
But certainly curious.
 
ludwig said:
Sorry that It wasn’t clear from the start ( blame it on my insufficient command of the english language ) , but the essence of this thread is not Rowley’s roll on test , but the function of the spray tube , and if or why all 850’s ( and ony 850 ) should have them .
What we have learned from Rowley ( and others ) so far , is that it looked like the stepped spray tube was an essential part in the solution for a very specific problem :
to pass a rather unrealistic test , with a type of muted silencer that practically nobody uses anymore .
LAB wil correct me if I am wrong , but isn’t is so that if you order Amal carbs for an 850 that they come with stepped spray tubes ?
Is it then so strange to wonder why we need them , and what they actually do ?
Speculation about its function ranges from emission control to accelerator pump ( henche the adjective ‘ Magic ‘ ..).
I know very well that my tests are of limited value , but I hope that they help to narrow down the options .
I invite you all to do better .
It may well be that the answer lies in atomisation .
And then whe haven’t even started on the obligatory link with the 4 ring needle .

I suppose most of us have seen this diagram :
Rowley's 1/4 mile and the Magic Tube .

Where is the spray tube ?


Maybe we should leave it alone , and say like someone here said :
“I don’t know how it works , or what it does , but I know it works “ .
But then , whe are no wiser than the man with the elefant powder .

And now , I will be on the road for the next couple of weeks ..
Click to expand...


Spray Tube diameter would be the same as Straight Dia. on the diagram. Mikuni needles usually all have the same straight diameter at the top of the needle and a range of different diameter needle jets or spray tubes as Amal calls them. Keihin has needles with different straight diameter and one size spray tube. I don't think that's an Amal chart.
 
ludwig said:
You must be joking , right ? ..
Click to expand...

No. No joke,
On that diagram/chart, I have absolutely no idea what is meant by 'effectiveness' there.
With that layout, they could just be randomly thrown up in the air and thats where they landed.

Except, the idle jet is down the botton, and only extends to part throttle.
That bit at least makes sense.

But, why isn't the mainjet up the top then. ?
Its 'effective' at full throttle.

But aren't they both 100% effective in the area where they operate.
Or does effective here really mean effect ?

You don't say where you obtained that chart from either.
Is it something from Amal ??

If that was handed in as an assignment, I'd mark it could do better, present again.
 
Rohan said:
ludwig said:
I suppose most of us have seen this diagram :
Click to expand...

I haven't - where did you obtain it ?

And I'd question - What does 'effectiveness' actually mean, as one scale on that graph. ??

It shows the pilot jet going to near half throttle - which seems highish, but its down the bottom of the chart,
so does that mean its not so effective ?!
It also shows the main jet extending up from 1/4 throttle, which is not entirely my understanding of when it comes into play ??.
Click to expand...


I think it's a Mikuni diagram.
 
edgefinder said:
Spray Tube diameter would be the same as Straight Dia.
Click to expand...

"Straight diameter" is the metering by the parallel part of the needle in the needle jet.

Not the spray tube.
 
Triton Thrasher said:
I think it's a Mikuni diagram.
Click to expand...

Of what ??
What is 'effectiveness' in this context.

There has to be some discussion somewhere of how those blocks are so placed,
whatever this 'effectiveness' is has some strange properties.
 
Triton Thrasher said:
"Straight diameter" is the metering by the parallel part of the needle in the needle jet.
.
Click to expand...

So why is 'clip position' at the top of the chart ??
 
Rohan said:
Sure would be interesting to see dyno chart comparisons.
It almost defies logic that it could have totally no effect ?
Click to expand...

I wouldn't necessarily disagree, however that has nothing whatsoever to do with the (apparently official) "claimed advantages" you mentioned.

Rohan said:
Sure are a lot of deluded folks that mention more torque in google search too...
Click to expand...

What has this to do with claimed advantages?

ludwig said:
What we have learned from Rowley ( and others ) so far , is that it looked like the stepped spray tube was an essential part in the solution for a very specific problem :
to pass a rather unrealistic test , with a type of muted silencer that practically nobody uses anymore .
Click to expand...

Yes.


ludwig said:
Is it then so strange to wonder why we need them
Click to expand...

No, not at all. But if the question simply boils down to "why we need them" then the answer would probably be that "we don't need them at all" and probably why your test results were inconclusive.
I expect some of us (myself included) have used the flat top spray tubes and standard needles on our 850s without encountering any flat spots when riding under normal conditions but then our 850s probably don't have mutes and we don't operate the throttle in the same manner as was done for the noise test.

ludwig said:
, and what they actually do ?
Click to expand...

As to what it actually does is a slightly different matter and therefore we would need to understand exactly what is happening inside the carb, and I think the answer could be more complex than just an alteration in mixture strength which seemed to me to be what your testing was mainly concerned with.

ludwig said:
LAB wil correct me if I am wrong , but isn’t is so that if you order Amal carbs for an 850 that they come with stepped spray tubes ?
Click to expand...

According to Burlen's (Amal's) original Norton factory carb specification sheet, all 850 carbs had the stepped spray tubes (and 104 needles) so if carbs are ordered from Burlen then that's what one should expect be supplied with, as that was the original "factory" specification, however if a carb is a generic item bought from an Amal dealer and "built to order" then it's anybody's guess which spray tube it will have.
 
Rohan said:
Sure would be interesting to see dyno chart comparisons.
It almost defies logic that it could have totally no effect ?
Click to expand...
L.A.B. said:
I wouldn't necessarily disagree, however that has nothing whatsoever to do with the (apparently official) "claimed advantages" you mentioned.
Click to expand...

Until we see those dyno charts, everything is just supposition ...
 
Status
Not open for further replies.
Back
Top