Topic: 3d printing pod inserts for laminar flow

[stan.]

I was inspired after considering the honeycomb inserts you see in the MAF on a car, and seeing mkowski's build where he used a bundle of straws to create an insert.  I'm putting uni filter pods on my K7 and one of the non-motorcycle things I do is props so i have the tools for creating 3d printed things.  I designed an insert piece that is 46mm (inlet size of my PD41As) in diameter and 30mm long which is filled with a hexagon pattern and am currently 3d printing it.  I'm interested to hear if anyone has done something similar and also to discuss thoughts on the ideal shape for the channels, diameter of the channels, and length. 

[evinrude7]

function wise, what's the benefit?  i'm not knocking the idea.  serious inquiry.

[stan.]

turning turbulent flow into laminar flow, my reading has been that a chief complaint against running pods is that they do not have the nice laminar flow that the stock airbox does - allegedly the major cause of performance losses and tuning difficulties.  the insert would solve that.  this has been done in a sense before, with mkowski using drinking straws.  my goal is something more durable that can also be dialed in to perform best as i'm printing the part instead of relying on off-the-shelf straws.

[evinrude7]

great idea.  the convenience of pods is nice.  if you can find a fix for the problems they cause, all the best.  keep us posted. 

[TwoTired]

How will you test them?

Up to what air speed will they remain laminar?

Be aware the extra surface wall area does add drag to airflow.  And, at higher speeds, induce turbulence due to high speed air in the center of each tube and high drag low airspeed near/at the tube wall.  Then there is the added lip of each individual tube, entrance and exit.

The stock airbox velocity stack looking rubber coupler were shaped that way for a reason.

Do you have a flow bench or smoke wand?  Can you measure pressure differentials on either side of the "flow straighteners"?

Cheers,

[FunJimmy]

Interesting concept. Do these laminar flow inserts mount inside the pod filters?

[FunJimmy]

How will you test them?

Up to what air speed will they remain laminar?

Be aware the extra surface wall area does add drag to airflow.  And, at higher speeds, induce turbulence due to high speed air in the center of each tube and high drag low airspeed near/at the tube wall.  Then there is the added lip of each individual tube, entrance and exit.

The stock airbox velocity stack looking rubber coupler were shaped that way for a reason.

Do you have a flow bench or smoke wand?  Can you measure pressure differentials on either side of the "flow straighteners"?

Cheers,

Why didn't I say that?

[scottly]

The optimum shape for the entrance to a carburetor is a bell-mouth shape, commonly known as a velocity stack. Print a stack that pod filters can be fitted to, and you may be onto something.  

[FunJimmy]

The optimum shape for the entrance to a carburetor is a bell-mouth shape, commonly known as a velocity stack. Print a stack that pod filters can be fitted to, and you may be onto something.

Add your laminar air flow honeycomb to that velocity stack get best of both worlds.

[stan.]

How will you test them?

Up to what air speed will they remain laminar?

Be aware the extra surface wall area does add drag to airflow.  And, at higher speeds, induce turbulence due to high speed air in the center of each tube and high drag low airspeed near/at the tube wall.  Then there is the added lip of each individual tube, entrance and exit.

The stock airbox velocity stack looking rubber coupler were shaped that way for a reason.

Do you have a flow bench or smoke wand?  Can you measure pressure differentials on either side of the "flow straighteners"?

Cheers,

this is very much a try-and-see project since i have the means to create the parts on hand already anyway and it's trivial to iterate the design.  i'd love to know how to actually figure out the particulars of the variables you mention, maybe doing flow simulation in my cad software but i'm not sure how i'd simulate the pulsing flow that i assume is present on each carburetor.  ideas?

[stan.]

here's the printed parts from the earlier images

[BomberMann650]

Motorcycling for Science!   

[TwoTired]

The printed parts look impressive!

But, surely you must realize that all the material in the cross section fill, reduces the cross section area, essentially making a restrictor.

Because of the cross section area reduction, such devices are usually placed well ahead of an actual venturi, and always exceed the venturi throat area.

Have you made a calculation or measurement for the cross section area of your device?

I guess I'll ask.  If you just toss them into service, by what benchmark(s) will you declare victory?

Finally, simulation are wonderful tools during prototyping.  But, at some point the tool must be verified as accurate, or the prototypes have to be verified to "prove" the simulator.  Unfortunately, precision measurement tools can be expensive.  And then learning to use the tool properly and for repeatable results, can be an adventure in it own right.   BTDT

Cheers,

[stan.]

The printed parts look impressive!

But, surely you must realize that all the material in the cross section fill, reduces the cross section area, essentially making a restrictor.

Because of the cross section area reduction, such devices are usually placed well ahead of an actual venturi, and always exceed the venturi throat area.

Have you made a calculation or measurement for the cross section area of your device?

I guess I'll ask.  If you just toss them into service, by what benchmark(s) will you declare victory?

Finally, simulation are wonderful tools during prototyping.  But, at some point the tool must be verified as accurate, or the prototypes have to be verified to "prove" the simulator.  Unfortunately, precision measurement tools can be expensive.  And then learning to use the tool properly and for repeatable results, can be an adventure in it own right.   BTDT

Cheers,

the ones pictured above are matched  to the diameter of the carburetors' inlet (ID of solid wall is matched to ID of carb inlet) and represent 25% reduction in area, 75% open space, compared to free flow.  early victory will be if the bike runs better with them than without.  having a lower restriction would be accomplished by having fewer and larger hexagons, so the question is whether freer flow or smaller hexagon diameter would be the bigger benefit.

my goal ultimately is to make pods more manageable.

[Smudgemo]

I got an email recently from Shapeways, the outfit that prints my start switch housings, and they've apparently outfitted themselves with the newest, bestest printers available and are ramping up for using them. 
If that technology isn't suitable for this job in plastic, they also print in metal.  Plenty of examples that look smooth and shiny, but I have no idea whether that requires work after printing or not.  Additive manufacturing keeps improving, so maybe this job is now viable or will be soon.

[flybox1]

Of course, all this is a remedy for a problem created by the owners who modify the stock induction system 

Hahahaha 

[flybox1]

Of course, all this is a remedy for a problem created by the owners who modify the stock induction system 

Hahahaha 

And I freely admit to being one of those troublemakers...

My name is Rob, and I punched a few holes in a perfectly good airbox once.
Maybe best to save it for (Pod-Anon) group! 

[TwoTired]

my goal ultimately is to make pods more manageable.

OK...

But, with a scientific or engineering process, wouldn't you first characterize behavior/performance before a mod and compare it to behavior/performance after a mod, using hard repeatable data?

For me, it is concerning that you treat "pods" as a specification in its own right, when the are many manufacturer's offerings, and I've yet to see published any sort of a spec on flow characteristics, pressure drop through the membrane, etc.  Even physical size and shape are barely specified.

Do you have a particular POD brand or part number in mind?

Trying to wrap my head around this...
So, the action plan is to add a device to an unknown variable (pods) and expect a definitive outcome?  Do I understand this correctly? 

[BomberMann650]

TT has a point.

Testing a hypothesis with solid measurements and controls is good science.

[Duke McDukiedook]

I'll pile on too. Maybe you could talk to a local tech school or university to see if you could get some time on a scale tunnel for smoke testing at real world velocities? My fluid mechanics expertise is more on the macro scale so I really could not help you much here. good luck with the design and testing.

[MessnerMoto]

I have a similar idea for my Mikuni rs34. The problem is the minimum thickness of wall when you do 3d print and quality of finish

[stan.]

I have a similar idea for my Mikuni rs34. The problem is the minimum thickness of wall when you do 3d print and quality of finish

SLA might be a strong candidate for those needs.  I've got a friend with a formlabs printer.  love how you did your pattern.  I was trying to wrap my head around lofting a series of channels in one go, looks like you did a circular pattern for each position to make life easier?

[stan.]

TT has a point.

Testing a hypothesis with solid measurements and controls is good science.

agreed, but at this time i don't have access to test the sorts of variables involved

since it is easy to test the bike with and without the inserts, or with different variations, I see no reason to pass on a project simply because it cannot be scientifically characterized.  at the end of the day it's a $300 bike and if it runs better then that is not an invalid result for me personally.  clearly that does not make it a marketable product, but if it works for me and inspires someone to do better then why not?

[stan.]

my goal ultimately is to make pods more manageable.

OK...

But, with a scientific or engineering process, wouldn't you first characterize behavior/performance before a mod and compare it to behavior/performance after a mod, using hard repeatable data?

For me, it is concerning that you treat "pods" as a specification in its own right, when the are many manufacturer's offerings, and I've yet to see published any sort of a spec on flow characteristics, pressure drop through the membrane, etc.  Even physical size and shape are barely specified.

Do you have a particular POD brand or part number in mind?

Trying to wrap my head around this...
So, the action plan is to add a device to an unknown variable (pods) and expect a definitive outcome?  Do I understand this correctly?

i'll be testing with uni filter pods, the specific part number escapes me at the moment but i can post later.   you're absolutely right that they don't have well-defined specs, which is why the conversation is as coarse as it is.

the plan of action is to change one variable - no insert, various versions of inserts - and characterize the results using my NIST-certified gluteal dynamometer as well as an array of ocular, auditory, and tactile sensors to determine which works best.

[Duke McDukiedook]

If possible you will want to try and radius taper/chamfer your inlets and outlets- that will help reduce eddies and turbulence. Squared inlet and outlets at the lips are not going to help you achieve laminar flow.