Kiln drying STEEL?

[B A R R Y]

I've seen lots of polished spinners, but no polished props.

[B A R R Y]

John,

Isn't that section of the prop heated for ice protection?

[J. Clarke]

Centrifugal force takes the ice right off outboard, the prop deicers are on the inboard end and the spinner On an older commuter airliner like the DHC-7 you can see the heater as a rubber piece bonded onto the blade.

In

you can see the heaters on a solid aluminum blade if you look carefully--there's a foam cuff inboard with a rubber covering, but on top of that there's a deicer attached--you can see the edge of it about 1/3 of the way back on the top left blade. The little tab that sticks up is part of the heater but isn't itself heated. The shiny strip along the leading edge is likely where dust and rain and whatnot have eroded the anodize off the blade, although the Dutch may have painted it for some reason. The tips would have been repainted recently. shows a different model of that prop (both the P-3 and the C-130 use the 54H60 but with different blade tips--nobody ever told me why the difference). shows the heater very clearly. Note the clear tape at the ends of the heater--that's one that I haven't seen before on that prop but would bet that it's polyurethane tape that's there to protect the outer edge of the heater--the outer few inches of those heaters would wear through long before the rest and the polyurethane tape was an approved modification on the commuter airliners when I left the company--it's very likely that someone after me got it approved for that use on the P-3. is another with a clear view of the heaters--on this one they've been cut back a little bit--not sure if it's far enough to get into the wires or not--but that's the area that would wear through.

[Stealth Pilot]

alright you got me there :-) hovercraft props!!!!

I dont recall seeing the leading edges you mention on commuter turbo props but I'll believe you.

most props are forged 2025 aloominum with an anodised surface hardening. the polished prop effect is achieved by wearing off all the anodising and polishing the remaining aloominum. the leading edge treatments I can recall are more like icing cuffs or polyurethane tapes.

seriously though I do believe you on the hovercraft props.

Stealth ( Hovercraft props!?!?) Pilot

[J. Clarke]

I think that the term for the sort of commercial aircraft that would have Hamilton props is "regional" airliners these days.

The C-130 and P-3 have 7075 blades (note, not 707_6_--Hamilton props are about the only place that 7075 is used and Alcoa used to have to run special lots for Hamilton). The Hamilton commuter props have a fiberglass or Kevlar shell over an aluminum spar, which may be 2024--I honestly don't recall what they were using on those spars. The 54460 on the E-2 had a fiberglass shell over a steel spar--don't know what they're doing on the new 8-way. If you look at the photos of that prop on flickr you'll see that inboard of the nickel sheath the leading edge is smooth--the deicer is molded into the fiberglass--the wires are stitched into place during layup. The 24PF had a glue-on rubber heater, but the newer ones have gone to the integral heater.

Here are a few that show the sheathes more or less well:

clear prop close-ups are rare.

By the way, those polyurethane strips--I'm the guy who got the first one certificated, for the 24PF on the DHC-7.

[Stealth Pilot]

centripetal force and inertia exist. centrifugal force is a misnomer. Stealth pilot

[J. Clarke]

Most engineers don't have time to write book every time they refer to the mechanism by which water is retained in a bucket that is swung in vertical circles on the end of a rope. We just call it "centrifugal force" and recognize that that's shorthand for a long-winded explanation and get on with life.

[Morris Dovey]

LOL - Just thinking of the fortune you (I/we) passed up by not selling a rubber stamp with this explanation...

:-D

[Andy Dingley]

Here's a worst-case example: lots of thin strip, hot-dipped afterwards. =A350 (minimum charge) to do a couple of them (or a few more)

can't chrome plate over zinc though

[Stealth Pilot]

suave stuff!

what aerofoil family(s) did you use? what limiting tip speed did you work to?

this area of aviation seems to one of the least publicly documented areas and yet it is one of the most important.

Stealth Pilot

[J. Clarke]

I've long since forgotten--I seem to recall that they were from a family developed specifically for propeller use. Wasn't something I normally had to deal with.

Not a number I ever carried in my head. The only one that sticks is

1050 RPM as the governed RPM for the 54H60 (note--adjusting the RPM on that prop was a maintenance item, not a cockpit control). You can work from that to the tip speed.

Of course Hamilton built supersonic props but I don't know for sure that they ever flew--the one on the XF-84H doesn't look like the drawings and components I saw (_really_ wish I could have taken pictures in the shop, but cameras other than in the hands of the official photographer were strictly forbidden, there was all sorts of historically interesting stuff racked in odd corners which has probably been lost now), which suggests that it was the Curtiss design--the project was supposed to test several prop variants but the airframe proved to be unsatisfactory for the purpose and rather than fix it the project was cancelled. Never encountered anybody who was willing to talk about it.

Somebody really needs to write a history of the aircraft propeller before it's lost.

[Larry W]

For ordinary hotrolled mild steel? The traditional solution is paint. If you want the bare steel look I suppose you could use varnish or laquer.

[Stealth Pilot]

a very good point. what are you doing later this week? :-) it would make a very good retirement project.

...go on give it a go.

Stealth (seriously) Pilot

[J. Clarke]

If I thought there was a real chance that I was ever going to retire that would be a fine idea.

[B A R R Y]

That would be interesting.