Ceiling Light Unit / Vacuum Conversion

[kmisegades]

The cheap plastic bezel for my ceiling light unit has fallen apart. Can someone recommend a replacement source? Mine is a 1952 B model.

I am also interested in converted from venturies to a vacuum pump. Does anyone have info on pump units for C-145 engines?

Many thanks.

[jwmcgu]

Kent,
Email me and I'll send you a picture of the spare overhead light that I have and we'll see if it's what you need.
John McGuire jwmcgu@meta-net.net

[GAHorn]

Do you have an O-300-D engine? If not, then you do not have provision for a vacuum pump.

Why do you want a vacuum pump? The currently available dry pumps are failure prone and expensive. The conversion is labor intensive, and expensive.

Venturis always work. They are cheap. They do not fail.

[blueldr]

George,

You know just as well as I do , that as the airplane gets loaded with ice and is headed for old terra firma at about 400 MPH, those damn venturies will ice over just before impact.----but they WILL ice over.

[GAHorn]

Yeah. You're right. And it's so important to crash right-side up.

It does amaze me, the number of folks who become concerned about venturiis icing up, as if that were the problem with operating in ice with these airplanes.

Folks...trust me....the venturiis will make vacuum for much longer than the wings/tail/prop will carry ice on these things. Iced up venturiis are not your problem if you are flying in icing conditions. (And even if they were, it'd be cheaper to simply install a back-up electric horizon than install a failure-prone vacuum pump system.)

Then there are the folks who want their gyro's all spooled up before the takeoff run commences. Firstly, who in their right minds would take off into such low weather conditions that required that. If you can't get airborne before entering the clouds, do you really want to do this single-engined? (And even if you did have terrorists chasing you down the runway with AK-47's blazing, wouldn't the back-up electric horizon solve that issue?)

[Tom Downey]

I'm with George on this, If you have any ice in the venturi, it's the least of your problems.

[kmisegades]

Thanks, guys, for the quick response.

I am stripping my C170 of external stuff that slows it down in an experiment to see if I can get another 10mph cruise out of it. I don't intend to fly in any icing conditions, in fact the plane will remain day VFR only. I am pretty sure I have seen a vacuum conversion on a C-145, but perhaps I was misstaken and this was an O-300? Yes, the alternative is an electric gyro, but these are quite pricey. I am doing an alternator conversion this winter as my old & heavy generator just died (again!).

Again - my motive is strictly an aero clean-up. I know that the C-170 is a great "low-and-slow" flyer but I have a few destinations here in the SE that I could reach without a fuel stop if I were only 10mph faster.

My comparison in this work is Miss Pearl,
http://www.nwark.net/~mspearl/start.html
that shows what is possible through many little things adding up. If one can do this with an old Piper Pacer, just think what ought to be possible with the world's greatest taildragger, the C-170?

regards, Kent Misegades, Cary, NC

[doug8082a]

I don't think the expense of converting from the venturi to a vaccum pump will be worth it. We're used to looking at a "big venturi" from the side, but think about the actual frontal area of a venturi as seen by the oncoming air and the fact that it's mounted tight to the fuselage in an area of highly disturbed air. I seriously doubt you'll find any increase in cruise by removing it.

If I were to consider speed increases for a 170 I'd look into RIGGING first and foremost and Cruise prop followed by: removing unused antennas and replacing antennas in use with more aerodynamic ones, strut cuffs, wheel pants & brake caliper fairings, different wing tips, something to cover the "moat" around the fuel caps, and changing the screws on all the inspection covers to flush screws (if that can legally be done).

[lowNslow]

Again - my motive is strictly an aero clean-up. I know that the C-170 is a great "low-and-slow" flyer but I have a few destinations here in the SE that I could reach without a fuel stop if I were only 10mph faster.

You would have to come up with an equalivent horsepower increase of 30HP to achieve a 10mph increase! I doubt removing the venturis is going very far in doing that.

[Metal Master]

George,
How many times have you written the words? (Why would you want to install a vacuum pump?)

Jim

[russfarris]

The cheap plastic bezel for my ceiling light unit has fallen apart. Can someone recommend a replacement source? Mine is a 1952 B model.

I am also interested in converted from venturies to a vacuum pump. Does anyone have info on pump units for C-145 engines?

Many thanks.

Kent: What everyone else has said on the venturi.

I've seen Miss Pearl at Sun-n-Fun, but I couldn't find on his website any claims of increased performance due to his mods, if that's what you were refering to. Or was it the cleaned up appearance of his Pacer that impressed you?

Many younger pilots seem a little taken aback by venturis, since the airplanes they learned to fly on didn't have them. I've had more than one pilot ask me what it was (the deer warning horn, of course!)

For the overhead light lens cover (the bezel is the square metal part keeping the lens cover in place) cut an appropriate sized piece out of the side of an empty gallon translucent plastic milk jug; the very definition of an approved owner-produced part! Russ Farris

[doug8082a]

Many younger pilots seem a little taken aback by venturis, since the airplanes they learned to fly on didn't have them. I've had more than one pilot ask me what it was (the deer warning horn, of course!)

Good job Russ! Got to keep that urban legend alive!

[kmisegades]

Of course, removal of my two venturis won't have much of an impact, but they will have some. The added weight, complexity, mechanical friction and cooling drag of a vacuum pump offsets this, of course. I won't get my extra 10mph through the venturies alone, but maybe 10-20 small things adding up will get me there.

Miss Pearl's owner claims a top speed of 160mph and cruise speed of 140mph on 160HP. 1mph per HP sounds pretty good for an old, draggy design. Even stock RVs can't match that.

Thanks for the comment on "younger pilot" - I've been at it for 34 years, since age 15, and still have much to learn.

Latest issue of Cessna Flyer has an article on the "World's Fastest C180" that claims a top speed of 200mph. Must have been going downhill? Still, that's pretty impressive. Wonder what the Vne is, though?

regards to all, Kent

[Indopilot]

We had an examiner down here, refuse to give a check ride in a A/C with venturi's for some reason. If I remember correctly he was saying to be IFR certified the venturi's had to be heated or something like that. Not to often you ice up in southeast Arizona but it can happen. Brian

[GAHorn]

The examiner should have been shown the type certificate and the IFR approval, day/night the airplane has with venturi's.... and he should be forced to go to re-training/indoctrination....along with that guy who put condition tags on all those Q-tip props.