1. Home
  2. ⏣ General Metalworking
  3. Removing broken steel screws in aluminium (this time it's a siren)
  4. Page 2

Removing broken steel screws in aluminium (this time it's a siren)

Thanks for the offer. I'm just outside Newport, Shropshire. I'll bear you in mind if I can't find any nitric acid locally.

To update everyone on the project a little, I got inside the motor tonight. It looks fine. Everything is still coated in solid resin, there's no corrosion and the motor doesn't look burnt out. The wires which lead to the brushes will need replacing, but this is no big deal.

Unfortunately I made a small mistake when dismantling the motor. I tried to remove a screw from the end of the shaft to release the bearing. Damn, this screw is tight, I thought. Really tight. Then the screwdriver blade bounced out of the slot and really made a mess of the screw head. I then discovered that it was a left hand threaded screw! We live and learn. I probably could have avoided this if I had the manual for this beast, but as yet I don't even know the manufacturer.

Does anyone have a spare left hand threaded 2 BA machine screw? The original is tin plated brass and 7/16" long, although length and material are not critical.

Best wishes,

Chris

Reply to
Christopher Tidy
Loading thread data ...

That one won't bother the neighbors for very far, after all it's just a pennywhistle. What, 1 Horsepower?

Now if you want a *real* siren that'll make some /serious/ noise, Bubba, here's a 180-HP siren that'll wake the dead, gaa-ron-teed...

formatting link
;-)

Seriously, if you can get that old one apart far enough to let the Alum or Nitric Acid do it's work getting the waste steel bits (shaft stubs, setscrews, assembly bolts) off the aluminum castings, you might have something there. If anything, sacrifice the motor shaft and save the aluminum impeller & housing castings. The motor windings are most likely toast by now anyway.

You can always find a replacement motor and/or get a new chunk of shafting. But finding a foundry, making a proper pattern, casting a new impeller, and getting it all machined and dynamically balanced (so the siren doesn't shake itself to death) will be a total pain.

-->--

Reply to
Bruce L. Bergman

Wish I could afford one. I would LOVE it. I could lend it to Gunner as a burglar alarm!

Got inside the motor tonight. It looks near perfect. The totally enclosed construction has protected it well. Here are some pictures:

formatting link

There's no need to sacrifice the shaft. I took off the motor end bell, unbolted the rotor, tapped the shaft with a centre punch and it slid out. But I really am going to have to get a new rotor. This one is flaking apart. I guess I could get new fins welded onto the rotor disc, but this is also a pain as it would need to be done perfectly. The other aluminium castings can be saved though.

Interestingly I found a date on the motor. 20/7/38. This is sounding more like a wartime siren!

Best wishes,

Chris

Reply to
Christopher Tidy

Of course it is. Few factories used such a siren for lunch etc. Thats an air raid siren.

Gunner

"A prudent man foresees the difficulties ahead and prepares for them; the simpleton goes blindly on and suffers the consequences."

- Proverbs 22:3

Reply to
Gunner

:-D

I wasn't sure at first. This factory is way out in the country, so I wasn't sure they'd have an air raid siren, but it seems they did. Another thing which suggests wartime use is that the demolition guys who got it down for me didn't have to disconnect any wiring. It had been been disconnected long ago and the siren painted over, despite the fact that the motor looks in good order.

I think I might see if I can look up some old guys who worked at the factory and see if any of them remember the siren.

Best wishes,

Chris

Reply to
Christopher Tidy

On Wed, 06 Sep 2006 03:49:39 GMT, with neither quill nor qualm, Gunner quickly quoth:

It's quite obvious that you have never eaten homecooked UK food. Steak and kidney pie, their neighbor-island's haggis, etc.

-------------------------------------------- Proud (occasional) maker of Hungarian Paper Towels.

formatting link
Comprehensive Website Design ======================================================

Reply to
Larry Jaques

That's what I was thinking. There's some pretty tasty food in the town :-D.

The pharmacy have got me 1 kg of potassium alum. I'm going to pick it up tomorrow. If it doesn't work, I'll have to look for nitric acid. I don't know if the pharmacy will get that for me, though...

Chris

Reply to
Christopher Tidy

Actually, for the factory that I started off in, the works hooter was the whistle from the SS Mauritania. That was GEC Machines in Rugby... was BTH originally. The whistle did tend to flatten the power house boilers though!

These days It appears that it's not politically correct to wake up the entire town half an hour before the shift starts.

Mark Rand RTFM

Reply to
Mark Rand

I'll second the aluminum casting idea.

I've used a similar process to make new rubber manifolds for motorcycles as well.

Just siliconed up the bad manifold to spec and added to spots that were too thin in the original. (Manufacturer was a bit too cheap with the rubber!)

I cast the rubber in plaster of paris and have done the aluminum in petrobond (oil) sand. I used an artist's brush to sculpt sand from the mold made from the bad part, to replace the missing areas. Then a classmate and I poured the mold full of aluminum. (In high school metal shop no less, that teacher had big brass balls having teenagers with red hot metal! To be fair only the "good kids" got to do the pours.)

Ah, the good old days. Oh, that was just 1986!

Bart

Bart D. Hull snipped-for-privacy@inficad.com Tempe, Arizona

Check

formatting link
my Subaru Engine Conversion Check
formatting link
Tango II I'm building.

Remove -nospam to reply via email.

Gunner wrote:

Reply to
Bart D. Hull

PolyTech Forum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.