Bell-mouth intake
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Joined: 11 Jan 2007
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Wed Dec 09, 2009 9:40 pm quote
After reading some research done by Gordon P. Blair on the ideal shape of bell-mouth intakes I've been drafting up some intakes for common vespa carbs and others. First started working on one for the 19mm smallframe but started having issues with the model. Earlier this week I finished the design to fit my motobi and today I finished the one for the largeframe 20/20 carb.

Should arrive in ~2 weeks, then testing will begin.

Screen shot 2009-12-09 at 9.25.12 PM.jpg

Sergeant at Arms
Weird 80's Vespas & Cool Vintage Lambrettas
Joined: 21 Oct 2005
Posts: 7122
Location: The state of insanity, SoCal
Wed Dec 09, 2009 9:43 pm quote
i'll be needing one for a 38mm keihein...

and a 24mm mikuni...

and a 24G...

just let me know when you've shipped them. i'll write an extensive review on each...

best,
-greasy
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Joined: 11 Jan 2007
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Location: San Francisco
Wed Dec 09, 2009 9:57 pm quote
greasy125 wrote:
i'll be needing one for a 38mm keihein...

and a 24mm mikuni...

and a 24G...

just let me know when you've shipped them. i'll write an extensive review on each...

best,
-greasy
No go on the mikuni and keihein, there's not much improving on them.

The 24G on the other hand... take one apart and scan the top surface for me (with a ruler for reference) and I'll crank one out. On the 20/20 there is a slight taper in the first 15mm of the bore. If the 24 has that I'd need to know the depth of the taper to match the angle.
Molto Verboso
Joined: 24 Jan 2008
Posts: 1886
Location: Santa Margarita,Ca.
Wed Dec 09, 2009 10:01 pm quote
The 24g has a bell shape built into the bottom plate of the air filter. I've wittled away the rest of it and used a uni pod on the airbox intake.
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Wed Dec 09, 2009 10:09 pm quote
scootermarc69 wrote:
The 24g has a bell shape built into the bottom plate of the air filter. I've wittled away the rest of it and used a uni pod on the airbox intake.
What's the radius on that filter? A simple radius get's you to about 85% of the ideal. The ideal shape turns out to be elliptical with the height being equal to the bore and diameter equal to 2.13 the bore.
Molto Verboso
Joined: 24 Jan 2008
Posts: 1886
Location: Santa Margarita,Ca.
Wed Dec 09, 2009 10:14 pm quote
Ha, you're way over my head there. I don't have that bike any more to check either.
Molto Verboso
Joined: 24 Jan 2008
Posts: 1886
Location: Santa Margarita,Ca.
Wed Dec 09, 2009 10:36 pm quote
Here's a pic

Poor mans Vortex.
Hooked
Too damn many
Joined: 05 Dec 2008
Posts: 293
Location: Seattle, WA
Wed Dec 09, 2009 11:34 pm quote
Quote:
No go on the mikuni and keihein, there's not much improving on them.
I was gonna say...the bellmouth is already there.
Ossessionato
Joined: 23 Sep 2008
Posts: 2633

Thu Dec 10, 2009 10:28 am quote
Very cool Patrick. Please keep us posted!
Molto Verboso
79 P200e, 81 100 Sport
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Thu Dec 10, 2009 10:32 am quote
Do you plan to finish the 19/19 one?
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2:6
Joined: 11 Jan 2007
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Thu Dec 10, 2009 11:15 am quote
I need to start over on the 19/19. The bell is easy but forming the case around it got complicated to the point that the model wouldn't export properly. I will get back to it at some point, there's a 50 special in the garage that keeps requesting it.
Molto Verboso
Joined: 24 Jan 2008
Posts: 1886
Location: Santa Margarita,Ca.
Thu Dec 10, 2009 2:13 pm quote
oopsclunkthud wrote:
I need to start over on the 19/19. The bell is easy but forming the case around it got complicated to the point that the model wouldn't export properly. I will get back to it at some point, there's a 50 special in the garage that keeps requesting it.
please do. I'm workin on a build using the 19 and would love to have that
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Joined: 11 Jan 2007
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Location: San Francisco
Fri Dec 11, 2009 12:24 pm quote
Here's what I was going for on the ET3. Not quite a filter but enough to keep out pets and small children. But despite starting over with the design the printer doesn't like it.

Starting again and just going to provide a flange for a K&N filter to fit on.

Screen shot 2009-12-11 at 11.14.46 AM.png

Hooked
Joined: 22 Feb 2009
Posts: 310
Location: Ex-Pat Brit in San Diego
Sun Dec 13, 2009 11:58 am quote
Re: Bell-mouth intake
oopsclunkthud wrote:
After reading some research done by Gordon P. Blair on the ideal shape of bell-mouth intakes.
I tried reading his work a few months ago. You're a better man than I for not only understanding it, but making your own.

For anyone else interested here's a link

http://www.profblairandassociates.com/pdfs/RET_Bellmouth_Sept.pdf
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Sun Dec 13, 2009 9:41 pm quote
Yup, that's the article. He makes you work a bit to get at the proportions. I've drafted up a standard at his proportions that I scale to fit whatever intake I'm working on.

Just finished the one for the smallframe 19/19 but It needs a cover or screen and that's the part that's been giving me hell. If you don't mind running an open bell you could run it without the cover.

If anyone wants to play with one I've opened up the models at shapeways.com so anyone can order them. There's no markup on these and I don't know how well they'll last but nylon should hold up ok.

http://www.shapeways.com/shops/oopsclunkthud

Screen shot 2009-12-13 at 9.34.52 PM.png

Molto Verboso
Joined: 24 Jan 2008
Posts: 1886
Location: Santa Margarita,Ca.
Sun Dec 13, 2009 10:52 pm quote
Ha. Just placed my order. I'll let you know how that works out. Ordered 2 as the minimum was $25 for a model. Any reason I can't just wrap the thing with a stocking for a filter?
nothing at all
Joined: 14 Nov 2008
Posts: 9657
Location: westla
Mon Dec 14, 2009 7:42 pm quote
hey marc

i'll buy the other one

did you get the 19/19

no need for you to have two
Molto Verboso
Joined: 24 Jan 2008
Posts: 1886
Location: Santa Margarita,Ca.
Tue Dec 15, 2009 10:36 am quote
I'll keep you in mind. There's no need for half the shit I have and yet........
nothing at all
Joined: 14 Nov 2008
Posts: 9657
Location: westla
Tue Dec 15, 2009 12:35 pm quote
scootermarc69 wrote:
I'll keep you in mind. There's no need for half the shit I have and yet........
totally dude, i'm not kidding, totally

i thru out bins of stuff, 100's of dollars of crap i hav'nt touched in years

10 sheets of 5/8 maple ply i've had before i got married

made two floor lamps and nothing else, thru em!

two bins of scoot crap just two months before a swap meet

idiot

and yet...............
Banned
2:6
Joined: 11 Jan 2007
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Location: San Francisco
Mon Mar 15, 2010 8:43 pm quote
I just got the errors in the cover for the bell intake fixed. Have one on order so I'll post pictures as soon as I get it. With any luck it will be by ROM so I can bring to for show and tell.
Molto Verboso
Joined: 24 Jan 2008
Posts: 1886
Location: Santa Margarita,Ca.
Tue Mar 16, 2010 2:14 am quote
oopsclunkthud wrote:
I just got the errors in the cover for the bell intake fixed. Have one on order so I'll post pictures as soon as I get it. With any luck it will be by ROM so I can bring to for show and tell.
ya, bring it. A flange to mount an air filter would be golden. I plan on using mine. Can you elaboate on the error? Any reason I shouldn't use the one I have?
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Tue Mar 16, 2010 8:40 am quote
scootermarc69 wrote:
oopsclunkthud wrote:
I just got the errors in the cover for the bell intake fixed. Have one on order so I'll post pictures as soon as I get it. With any luck it will be by ROM so I can bring to for show and tell.
ya, bring it. A flange to mount an air filter would be golden. I plan on using mine. Can you elaboate on the error? Any reason I shouldn't use the one I have?
I looked at doing a flange for a K&N but the filter would stick out too much. So I opted for a cover that would keep out larger stuff. The turbulence with the bellmouth should be reduced to the point that most particles will settle out.

The error was only in the cover, not in the bell. It was an issue with holes in the mesh that defines the shape. I could never find the holes but shapeways would report them. They just automated a process to fix these errors so now it's working.
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Mon Mar 22, 2010 11:16 am quote
Here's some pictures of the bellmouth and cover for the 19/19 carb on the ET3. I tried out the one for the 20mm largeframe carb and, well, it changed airflow enough that rejetting will be needed but I didn't have time to play with it more than that.

IMG_2157.jpg

IMG_2164.jpg

IMG_2160.jpg

IMG_2166.jpg

Hooked
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Joined: 14 May 2009
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Mon Mar 22, 2010 11:30 am quote
and your production run begins when? and how much?
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Mon Mar 22, 2010 12:32 pm quote
spielawieler wrote:
and your production run begins when? and how much?
They are available from shapeways if you want to try it out, printed to order. They deliver world wide in about 10 days.

http://www.shapeways.com/shops/oopsclunkthud

I've added no markup on them till they are tested and durability proven. For now the bell comes in at $13.59 and the cover at 37.02 shipping included.
Enthusiast
Joined: 26 Apr 2009
Posts: 92
Location: san jose
Mon Mar 22, 2010 1:17 pm quote
is there a pick up option for local people?

thanks!
Banned
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Mon Mar 22, 2010 1:31 pm quote
ahwest wrote:
is there a pick up option for local people?

thanks!
Nope!

I only designed it. They are printed in the Netherlands and shipped out from there. If I was to get in the middle of it it would only add time, tax, and effort.
Hooked
Vespa
Joined: 10 Oct 2009
Posts: 140
Location: Up north
Wed Mar 24, 2010 3:24 am quote
I'd really like to try this!

Do you have a bellmouth thing for the 24/24 carb? I can't seem to find it on your website.
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Wed Mar 24, 2010 6:39 am quote
JonnaV wrote:
I'd really like to try this!

Do you have a bellmouth thing for the 24/24 carb? I can't seem to find it on your website.
None for the 24/24 at this point. Not sure if there's room in the airbox for it. The Bell is as tall as the bore of the carb and it may not leave enough room for the air to flow into it. I could design a new carb box top to go with it. That and I don't have a 24/24 carb to measure.

Don't think I'll be messing with the 24 till it's been tested on the 20 and 19. Besides, for the 24 Hotrod Al makes a great setup.
Enthusiast
Joined: 26 Apr 2009
Posts: 92
Location: san jose
Wed Mar 24, 2010 8:14 am quote
call me dumb but what is the real benefit of having the bell mouth type intake? smoother throttle response? more power?

the plastic one in the picture is only a prototype right? the actual product will be metal?
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Wed Mar 24, 2010 9:09 am quote
ahwest wrote:
call me dumb but what is the real benefit of having the bell mouth type intake? smoother throttle response? more power?

the plastic one in the picture is only a prototype right? the actual product will be metal?
The entrance on these carbs is a squared edge. This causes turbulence that can reduce the effective area of the carb by about 25%. A simple rounded edge can solve most the problem but the bell mouth has been shown to have the best flow rates.

I've no intension of creating these in metal. Plastic is plenty durable and well suited to use here. That and I don't think there's enough people that would want them to make them any other way. If the demand was there I think I'd opt for silicone. For now it's something to play with to see if it helps.
nothing at all
Joined: 14 Nov 2008
Posts: 9657
Location: westla
Sun Mar 28, 2010 8:43 am quote
i am ordering today

my et3 is running a stock 19 with a 80 jet and a sport polini

the stock setup is a 76

i bought a 78 to see if there were improvments cause it felt a little over jetted

this product could be the perfect answer to the 80 thats in it

we will see

nice patrick, really nice
nothing at all
Joined: 14 Nov 2008
Posts: 9657
Location: westla
Sat Apr 24, 2010 6:44 am quote
i have been on such a slump that this got put on hold

i made a decent trade, my bbq rack for a new banana pipe

hey marcus, maybe my sport polini and a little cash for a bell intake!!!

_Media_Card_BlackBerry_pictures_IMG00363.jpg

Enthusiast
Joined: 26 Apr 2009
Posts: 92
Location: san jose
Sun Jun 13, 2010 8:36 am quote
Hey Jimmy, how's the bell mouth intake treating your et3?
nothing at all
Joined: 14 Nov 2008
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Sun Jun 13, 2010 10:23 am quote
ahwest wrote:
Hey Jimmy, how's the bell mouth intake treating your et3?
scooter funds have prevented me from most wanted purcheses

i want it because that damn stock air filter is carving my hand getting the carb in n out
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Mon Oct 25, 2010 8:41 pm quote
Finally got around to installing the bellmouth on Julie's 50 special. Went from a 74 main jet to an 85 for starters but I think I still need to go a bit higher. Idles nice and doesn't bog anywhere on it's way to WOT.

Only 4 weeks to get it dialed in before the landspeed trials, but it's looking good so far.

IMG_2549.jpg

Addicted
Wrench
Joined: 14 Sep 2010
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Location: Workshop
Tue Oct 26, 2010 4:40 am quote
[quote="oopsclunkthud"]Finally got around to installing the bellmouth on Julie's 50 special. Went from a 74 main jet to an 85 for starters but I think I still need to go a bit higher. Idles nice and doesn't bog anywhere on it's way to WOT.[/quote]

O please fill us in on the engine setup on this.. I have seen your bellmouths on shapeways, always a step away from buying, but that kind of flow jump is just kick ass..

And are those nylocks I spy holding the unit on? I was actually wondering about a firm non-damaging attachment.. It never even hit me, nylocks..duh
Hooked
'08 Voodoo Buddy 250cc, '74 Super 150, '74 Super /w 200cc Rally 180 engine
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Tue Oct 26, 2010 5:37 am quote
Wow, thats a neat little device. Makes me want to go figure out which carb my Rally engine has on it
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Tue Oct 26, 2010 6:15 am quote
Quote:
O please fill us in on the engine setup on this.. I have seen your bellmouths on shapeways, always a step away from buying, but that kind of flow jump is just kick ass..

And are those nylocks I spy holding the unit on? I was actually wondering about a firm non-damaging attachment.. It never even hit me, nylocks..duh
Nylocs are your friend, I use then everywhere except the exhaust. Buy them by the bag full.

The setup in this case is as follows:
50 Special crank (43mm)
pinasco 100 kit
22/63 Vespa 90 primary drive
4 plate clutch with stock spring
Dellorto 19/19 carb
Polini righthand exhaust

I'm a big fan of the 43mm cranks. They can rev out to 12,000 safely.

IMG_2546.jpg



Last edited by oopsclunkthud on Fri Mar 18, 2011 6:01 am; edited 1 time in total
Enthusiast
2005 ET4 150cc
Joined: 25 May 2010
Posts: 91
Location: Kitchener, Ontario
Tue Oct 26, 2010 7:20 am quote
Any plans for one for the ET4?
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