Rowley's 400 and the Magic Tube , hijacked version .
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Re: Rowley's 400 and the magic spray tube .
Can someone elaborate on what is 'US silencing' ?
My understanding was that the US got the model with the peashooters, with mutes - the Mk 1 850 Commando for early 1973.
And the amals came with cutaway spray tubes, for ALL models of 850 for all years.
Late in 1973, the 850 Mk 1A model appeared, with noise control equipment. (black cap mufflers, and plastic airbox with horns)
This was for the European market, primarily. (?). Who required quieter bikes.
ludwig said:
Can someone elaborate on what is 'US silencing' ?
My understanding was that the US got the model with the peashooters, with mutes - the Mk 1 850 Commando for early 1973.
And the amals came with cutaway spray tubes, for ALL models of 850 for all years.
Late in 1973, the 850 Mk 1A model appeared, with noise control equipment. (black cap mufflers, and plastic airbox with horns)
This was for the European market, primarily. (?). Who required quieter bikes.
Fast Eddie
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Re: Rowley's 400 and the magic spray tube .
I tried angled and straight tubes some while ago to compare (on the track, not the dyno) and couldn't tell any difference! This was on 1000 series mk1s (the bigger bodied ones).
I was told that they work on some and not on others and that experimenting with them with different needle and needle jet combinations was required.
But as I had, by then, got it on the Dyno and showing good AF ratio, I didn't bother!
I tried angled and straight tubes some while ago to compare (on the track, not the dyno) and couldn't tell any difference! This was on 1000 series mk1s (the bigger bodied ones).
I was told that they work on some and not on others and that experimenting with them with different needle and needle jet combinations was required.
But as I had, by then, got it on the Dyno and showing good AF ratio, I didn't bother!
Brooking 850
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Re: Rowley's 400 and the Magic Tube .
Hi Ludwig, i am running 32mm premiers on my race bike with 310 jets, standard length manifolds & long velocity stacks with a head potential of 74 HP on AVgas , my carbs have straight cut spray tubes and as I am not looking for any low down running or idle , certainly dont notice any lag or hesitation with throttle response..
I was tempted to insert some notched spray tubes to see if any difference, but havent and probably wont as it performs well enough.
Just a side comment to your thoughts
Regards Mike
Hi Ludwig, i am running 32mm premiers on my race bike with 310 jets, standard length manifolds & long velocity stacks with a head potential of 74 HP on AVgas , my carbs have straight cut spray tubes and as I am not looking for any low down running or idle , certainly dont notice any lag or hesitation with throttle response..
I was tempted to insert some notched spray tubes to see if any difference, but havent and probably wont as it performs well enough.
Just a side comment to your thoughts
Regards Mike
o0norton0o
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Re: Rowley's 400 and the Magic Tube .
At one point I was convinced that I could use a richer main jet and more ignition advance and get similar results to the standard jets and timing. I thought that the richer fuel ratio would slow down the flame front so I could use more advance to get more power and also gain some evaporative cooling effect from any extra fuel so the engine would run cooler.
With those settings, the bike would not accellerate past 80mph any more. I changed the main jet to the standard 220's and reset the timing and now the plugs look a dusty light brown and the bike accellerates much beyond 95...
I guess I thought more fuel would give me more power, but as it turned out the right amount of fuel gave me the most power. So I guess the old addage is true. Sometimes less is more....
At one point I was convinced that I could use a richer main jet and more ignition advance and get similar results to the standard jets and timing. I thought that the richer fuel ratio would slow down the flame front so I could use more advance to get more power and also gain some evaporative cooling effect from any extra fuel so the engine would run cooler.
With those settings, the bike would not accellerate past 80mph any more. I changed the main jet to the standard 220's and reset the timing and now the plugs look a dusty light brown and the bike accellerates much beyond 95...
I guess I thought more fuel would give me more power, but as it turned out the right amount of fuel gave me the most power. So I guess the old addage is true. Sometimes less is more....
Re: Rowley's 400 and the Magic Tube .
Engines work within a fairly restricted fuel/air ratio.
To go faster with (much) more fuel, you usually need more air as well !!
Thats what the 4 C's are all about - cams carbs cubes compression.
Curious why the manual doesn't list different jetting with and without the mutes in the peashooters for the early 850s.
It lists different jets for the 750 mit and without mutes...
Engines work within a fairly restricted fuel/air ratio.
To go faster with (much) more fuel, you usually need more air as well !!
Thats what the 4 C's are all about - cams carbs cubes compression.
Curious why the manual doesn't list different jetting with and without the mutes in the peashooters for the early 850s.
It lists different jets for the 750 mit and without mutes...
A
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Re: Rowley's 400 and the Magic Tube .
Hi ludwig.
I refer to your original posting above and ask "How could 'US silencing' have made any difference for the 850 compared to the 750?"
Reason for questioning: The Mk1 AMAL carby is activated entirely by manifold vacuum which is around 20 inHg for either the 850 or 750 or even the Combat engine. Compression ratio is irrelavent for this scenario.
Screwing the throttle open at 40 mph will have the same effect of dropping manifold vacuum toward zero inHg for all of these engines.
Therefore, 'curing' this 'problem' by 'stepping' the spray nozzle for 850s is patent nonsense.
Ta.
Hi ludwig.
I refer to your original posting above and ask "How could 'US silencing' have made any difference for the 850 compared to the 750?"
Reason for questioning: The Mk1 AMAL carby is activated entirely by manifold vacuum which is around 20 inHg for either the 850 or 750 or even the Combat engine. Compression ratio is irrelavent for this scenario.
Screwing the throttle open at 40 mph will have the same effect of dropping manifold vacuum toward zero inHg for all of these engines.
Therefore, 'curing' this 'problem' by 'stepping' the spray nozzle for 850s is patent nonsense.
Ta.
Re: Rowley's 400 and the Magic Tube .
Lets not confuse manifold vacuum with the Bernoulli effect of drawing fuel up out of deep wells.
The main jet in amals is BEHIND the slide barrier, but UNDER the restriction/venturi in the carb throat.
Carburettors operate on airflow, not (manifold) vacuum.
Besides which, manifold vacuum varies deeply, pulsing from a near full vacuum to no vacuum every 2 revs.
Contemplate that manifold vacuum is GREATEST with a closed throttle, and LEAST with a wide open throttle.
So the exact opposite of what is required of fuel delivery at such times.
So some deep misinformation thwarted here....
Lets not confuse manifold vacuum with the Bernoulli effect of drawing fuel up out of deep wells.
The main jet in amals is BEHIND the slide barrier, but UNDER the restriction/venturi in the carb throat.
Carburettors operate on airflow, not (manifold) vacuum.
Besides which, manifold vacuum varies deeply, pulsing from a near full vacuum to no vacuum every 2 revs.
Contemplate that manifold vacuum is GREATEST with a closed throttle, and LEAST with a wide open throttle.
So the exact opposite of what is required of fuel delivery at such times.
So some deep misinformation thwarted here....
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Re: Rowley's 400 and the Magic Tube .
Ugh. Do not get stuck selling the rest of us on only one influence drawing fuel up spray tube. if air flow was what drew fuel up spary tube on a throttle snap then slicing a lower passage in spray tube would lessen the draw/chimney/stack effect to lean mixture yet it enriches - as sliced/diced spray tubes are known for at low rpm air flow. At low rpm flow rates its the drop in pressure on engine side that draws up or rahter lets ambient psi push it out of bowl but as stated a snapped throttle ad low rpm gives lowest pressure signal so must lower the lift fuel must rise or baby throttle til air flow is fast enough to draw by chimney effect or fit accelerator squinter. I worked in a number of lab that had water powered fauset attached Ventrui/Bernellii vacuum to know if water valve not turned up hi enough water flowed into vessel one way trying to evacuate. Tall spray tubes work best at high flow and short ones and low flow. BTW the definition of lugging is when adding throttle does not increase power/rpm.
Hard to believe a 850 would not accelerate past its flat spot after very few seconds or just leaness knocking its lights out so something else not quite right if actually held 20 sec w/o speeding up. That could be dangerous trying to pass.
Ugh. Do not get stuck selling the rest of us on only one influence drawing fuel up spray tube. if air flow was what drew fuel up spary tube on a throttle snap then slicing a lower passage in spray tube would lessen the draw/chimney/stack effect to lean mixture yet it enriches - as sliced/diced spray tubes are known for at low rpm air flow. At low rpm flow rates its the drop in pressure on engine side that draws up or rahter lets ambient psi push it out of bowl but as stated a snapped throttle ad low rpm gives lowest pressure signal so must lower the lift fuel must rise or baby throttle til air flow is fast enough to draw by chimney effect or fit accelerator squinter. I worked in a number of lab that had water powered fauset attached Ventrui/Bernellii vacuum to know if water valve not turned up hi enough water flowed into vessel one way trying to evacuate. Tall spray tubes work best at high flow and short ones and low flow. BTW the definition of lugging is when adding throttle does not increase power/rpm.
Hard to believe a 850 would not accelerate past its flat spot after very few seconds or just leaness knocking its lights out so something else not quite right if actually held 20 sec w/o speeding up. That could be dangerous trying to pass.
Re: Rowley's 400 and the Magic Tube .
850s don't have dangerous flat spots, they carburate great.
Amal sorted that all out, before they sold em..... ?!!
Be interesting if/when Ludwig gets to the bottom of all that.
Carbs work on airflow, and that guy bernoulli again.
Try fitting a carb AFTER your Drouin supercharger, it will still work - no manifold vacuum in sight.
Might be tricky not pressurizing the carb though, which is why its not so commonly done.
This really is simple stuff, bernoulli 101 stuff.
But we diverge, muchly.
850s don't have dangerous flat spots, they carburate great.
Amal sorted that all out, before they sold em..... ?!!
Be interesting if/when Ludwig gets to the bottom of all that.
Carbs work on airflow, and that guy bernoulli again.
Try fitting a carb AFTER your Drouin supercharger, it will still work - no manifold vacuum in sight.
Might be tricky not pressurizing the carb though, which is why its not so commonly done.
This really is simple stuff, bernoulli 101 stuff.
But we diverge, muchly.
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Re: Rowley's 400 and the Magic Tube .
Ugh, I am just the messenger on long known carb spray-emulsion tubes dual principles that lifts fuel into air stream. In case others are confused by Rohan half right concept - read the few paragraphs on height vs air speed spray tube flow. Btw air plane wings do not depend Bernoulli low pressure flow only angle of attack and Lake Injectors do not use Venturii effect to draw fuel like a carb does, only air density so work well in air craft and snowmobiles. Car ground effects for more down force use Bernoulli contours on undersides. Also its ancient carb diagnosis to let off WOT a bit to sense pick up which implies too lean for WOT.
https://books.google.com/books?id=lDLhN ... ube&f=true
Needing who does not know it all yet, might find a few more Concentric carb details to diddle from this old Vintage Bike discussion
http://www.britbike.com/forums/ubbthrea ... ber=204271
Ugh, I am just the messenger on long known carb spray-emulsion tubes dual principles that lifts fuel into air stream. In case others are confused by Rohan half right concept - read the few paragraphs on height vs air speed spray tube flow. Btw air plane wings do not depend Bernoulli low pressure flow only angle of attack and Lake Injectors do not use Venturii effect to draw fuel like a carb does, only air density so work well in air craft and snowmobiles. Car ground effects for more down force use Bernoulli contours on undersides. Also its ancient carb diagnosis to let off WOT a bit to sense pick up which implies too lean for WOT.
https://books.google.com/books?id=lDLhN ... ube&f=true
Needing who does not know it all yet, might find a few more Concentric carb details to diddle from this old Vintage Bike discussion
http://www.britbike.com/forums/ubbthrea ... ber=204271
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Re: Rowley's 400 and the Magic Tube .
Please tell us more about this.
hobot said:
Please tell us more about this.
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Re: Rowley's 400 and the Magic Tube .
I do not like failing tests nor being found in error on my physics quips so search up the current theory of wing lift that got updated about 15 yrs ago that by far its angle of attack that matters. Vortexes play a part in wings too but carbs have too confined passages for that to apply.
Here one the most detailed reviews of Amal-ish type carb functions with variations of spray-atomizer tubes reasons for their different heights and reliefs for both low and hi speed air flow in carb ventrui. Scroll till the extremes of spray tube images stop ya to read the science of trial-error offerings.
http://www.danskkartingcenter.dk/dellorto_manual.pdf
I do not like failing tests nor being found in error on my physics quips so search up the current theory of wing lift that got updated about 15 yrs ago that by far its angle of attack that matters. Vortexes play a part in wings too but carbs have too confined passages for that to apply.
Here one the most detailed reviews of Amal-ish type carb functions with variations of spray-atomizer tubes reasons for their different heights and reliefs for both low and hi speed air flow in carb ventrui. Scroll till the extremes of spray tube images stop ya to read the science of trial-error offerings.
http://www.danskkartingcenter.dk/dellorto_manual.pdf
Re: Rowley's 400 and the Magic Tube .
Read what NASA has to say on wing lift theory and Mr Bernoulli's equation, Steve, and then quote us some good physics.
Remember he is all that is keeping you up there next time you fly, so better quote it right....
https://www.grc.nasa.gov/www/k-12/airplane/wrong1.html
Not that this has much to do with Amal carbs.
Nor manifold vacuums, which are a total red herring.
If manifold vacuum had anything to do with it (other than drawing air through the carb so Mr Bernoulli can do his stuff),
then carbs would draw the maximum fuel with the thottle CLOSED, and minimum fuel with the throttle WIDE OPEN,
exactly the opposite of what is actually required in an operating Otto Cycle engine.
Read what NASA has to say on wing lift theory and Mr Bernoulli's equation, Steve, and then quote us some good physics.
Remember he is all that is keeping you up there next time you fly, so better quote it right....
https://www.grc.nasa.gov/www/k-12/airplane/wrong1.html
Not that this has much to do with Amal carbs.
Nor manifold vacuums, which are a total red herring.
If manifold vacuum had anything to do with it (other than drawing air through the carb so Mr Bernoulli can do his stuff),
then carbs would draw the maximum fuel with the thottle CLOSED, and minimum fuel with the throttle WIDE OPEN,
exactly the opposite of what is actually required in an operating Otto Cycle engine.
Re: Rowley's 400 and the Magic Tube .
Ask yourself too why manifold vacuum doesn't pull a bucket of fuel into the engine with the throttle closed = when manifold vacuum is at its maximum.
Its because the carb jets are isolated from manifold vacuum by the carburettor slide,
and the jets are behind the slide - on the atmosphere side.
Minimal airflow through the carb with the slide closed = minimal Bernoulli effect = minimal fuel going into the engine.
As it needs, wants, requires - and gets.
Ask yourself too why manifold vacuum doesn't pull a bucket of fuel into the engine with the throttle closed = when manifold vacuum is at its maximum.
Its because the carb jets are isolated from manifold vacuum by the carburettor slide,
and the jets are behind the slide - on the atmosphere side.
Minimal airflow through the carb with the slide closed = minimal Bernoulli effect = minimal fuel going into the engine.
As it needs, wants, requires - and gets.
A
Anonymous
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Re: Rowley's 400 and the Magic Tube .
You have simutaniously:
1. Failed to comprehend the NASA link you posted - it says "Wrong"! and hobot is correct!
2. Do not know a herring from a pearl,
3. Failed to recognise the functions of the pilot jet circuit through to the main jet circuit on metering fuel to meet changing airflow requirements.
Ta.
Congratulations Dear Rohan.Rohan said:
You have simutaniously:
1. Failed to comprehend the NASA link you posted - it says "Wrong"! and hobot is correct!
2. Do not know a herring from a pearl,
3. Failed to recognise the functions of the pilot jet circuit through to the main jet circuit on metering fuel to meet changing airflow requirements.
Ta.
A
Anonymous
Guest
Re: Rowley's 400 and the Magic Tube .
Ta.
I say again: "Wrong" and quote your link "... There are modern, low-drag airfoils which produce lift on which the bottom surface is actually longer than the top. This theory also does not explain how airplanes can fly upside-down which happens often at air shows and in air-to-air combat. The longer surface is then on the bottom!...:Rohan said:
Ta.
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