Bomb Shell venturis

[T. Cotten]

Yes Mick,..

The ink marks are the extent of the conventional venturi of an M53A-1.

I haven't a true bombsight M53 available, but the much shorter portion of its OD would only expose much more of the pit.

Not that it matters, as just an exposed edge, or even much less, would be enough to allow it to suck air from the bowl.
This only shows how little I know about these things, as I would have bet it should barely even start.

....Cotten
PS: Wow. What if it wasn't the bombsights' fault they were discarded?

[ryan]

Does the drool pit have a hole going into the bowl?

Yes, it sure does. It is on the casting parting line.

[aumick10]

The hole in the end looks too small to be used very well to adjust the air flow. It is such a small percentage of the open venturi area.
Would it be a fuel drain for when you stop the motor?

[T. Cotten]

The hole in the end looks too small to be used very well to adjust the air flow. It is such a small percentage of the open venturi area.
Would it be a fuel drain for when you stop the motor?

No doubt it is a drool pit Mick!

But when running, it's a source of air downstream from the venturi.

And gargantuan, compared to microfissures that I have cured to greatly improve performance that were at least two or three orders of magnitude smaller.

That's why I am baffled completely, and seriously wish to understand.

....Cotten

[ryan]

The hole in the end looks too small to be used very well to adjust the air flow. It is such a small percentage of the open venturi area.
Would it be a fuel drain for when you stop the motor?

Although, I do not have any plug gauges in the house, the hole to the bowl measures .045" with a set of dial calipers, all 3 times I measured it.

[T. Cotten]

Using the butts of drills, Mick,..

The drool drain is a #55 (.052") and the bowl vent is a whopping #28 (.140").

Diabolical.

....Cotten

[aumick10]

I don't think it would pull much air at low speeds through such a small hole. There would be very little negative pressure there until the air flow through the venturi started to generate some negative pressure over the drain. Even then, an extra fraction of a turn on the high speed jet would counter that.
I hear the M53's were offered in a racing version for alchohol. Is the drool pit only for the racing versions?

[T. Cotten]

That's a huge hole, Mick!

It sees the same vacuum as the idle bleeds (before the venturi kicks in), and is roughly the same size.

The HS needle wouldn't affect anything until there is draw at the nozzle.

I wonder if Tom Sifton plugged the damn thing.

...Cotten

[T. Cotten]

What's a "Da Vinci", Kitabel?

Is it like any of the other 'wildcats'?

....Cotten

[kitabel]

Brand name of a replica bombsight, that's it in the picture.
The 1-1/4" replicas look very nice ($$$) but certainly flow less air than an original M-51. Would be helpful to adapt a 1-1/4" to a really small engine like a 741.

[T. Cotten]

Replica, Kitabel?

I thought we were talking Linkerts, where the secondary was in the middle of the bore, and the nozzle spigot poked through it.

Sorry, but your modern carb is completely foreign to me!

It just looks like a nozzle spigot with a tube on top?
We could do that. I solder things inside routinely with HX models.

....Cotten
PS: OK, I figured out that the secondary is so low because of the horizontal shaft. Great for a DC?
PPS: I just found another pic in my library; Similar?

[kitabel]

How it's described elsewhere, clearly an add-on rather than an entire booster assembly. The nozzle replaces whatever the carburetor had, no idea what is changed. Apparently at least some people are happy with it, the worst comments I've seen are "It's not much different". I would guess the usual comments applicable: a 883 Sportster with a Super E will get some transition improvement, a 96" TC with the same carb may be worse because it shifts the fuel curve to who-knows-where.

"because of the horizontal shaft", yes, it anticipates flow being faster closer to the throttle disc's open crescent. Should a fabricated booster for a Linkert be off-set toward the idle/transition holes...? There are shrouds for Mikuni that aim flow under the slide.

[T. Cotten]

Horizontal shafts solve the cylinder bias problem of course, Kitabel,..

And mark the divide from the archaic and classic to modern carbs, and improved performance naturally.

L&L did it first for American production machines, it appears.

I can't armchair-engineer any reason to put a secondary booster anywhere but in the middle of a Model M.

....Cotten
PS: Wouldn't it be great if one of my thimbles with golf ball dimples on the inside gave flow the same "lift"?

[kitabel]

I wonder what a smoke test directed down the barrel of an M-51 with 3" of vacuum on the far side of a throttle disc opened to 1/8" would show? Would it be centered until very close to the disc (after the nozzle), or begin tracking offside quickly?

[T. Cotten]

I wonder what a smoke test directed down the barrel of an M-51 with 3" of vacuum on the far side of a throttle disc opened to 1/8" would show? Would it be centered until very close to the disc (after the nozzle), or begin tracking offside quickly?

Me wonder too, Kitabel!

Got a Lucite body?

Somebody could scan a body, and 3D 'print' us a clear one, I'm sure.

(I've wanted a see-through bowl forever.)

....Cotten
PS: My money says it spins, and there isn't much linear flow. The disc directing turbulence at the bleeds is pretty much a "given", even though I have never seen it in literature.
PPS: I've been watching the bathtub drain for many years. That 'hemisphere' directional spin thing seems to only apply to global weather.