Author Topic: Manhole cover  (Read 11303 times)

Offline bingster

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Re: Manhole cover
« Reply #30 on: June 23, 2009, 10:14:58 PM »
These would make awesome firebacks in a fireplace, too. 
= DARRIN =



Offline odiedogg

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Re: Manhole cover
« Reply #31 on: July 17, 2009, 05:11:34 PM »
Muddying the water here.  I took this picture in West Lafayette this morning.  Several of these in town, but many have been paved over.

Offline HobieSport

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Re: Manhole cover
« Reply #32 on: July 18, 2009, 12:27:21 AM »
Bwanna and Dan/Panther, making castings really intrigues me too. What are your various ideas for casting materials?  

Since my only meager casting experience is mostly with various recipes of concrete, my mind tends to lean towards concrete front doorsteps and garden walkways and such.

For a lighter weight concrete product, one could use "tufa", using sand, cement, perlite and/or small grained red lava gravel. It would need wire or plastic mesh reinforcing, or loose fiberglass strand reinforcing, but that would be fairly easy.

Thinking about what material would be best suited to make the master "negative" form, I'm thinking of the standard super lightweight yet quite durable expanding polyurethane foam in an aerosol can. There is a readily available Dow product called "Great Stuff", and I'm guessing only a can or two for about 20 bucks would make a very durable mold of the whole personhole cover.

Expanding polyurethane is the same stuff they use to insulate buildings, fill cracks, is a roofing material, as well as the same stuff they use in the movie-set and theater industry to make inexpensive molds for complicated castings like natural rocks, architectural details, fake marble statues or pretty much anything else. You just spray it on and it expands like the Blob and fills in all the details and dries very hard very fast. I assume you know the stuff I'm writing about.

Of course one would need to coat the cleaned up "personhole cover" first with a "release", so that the polyurethane wouldn't stick to the metal at all so that it can be easily removed once the foam is dry. I'm no chemist but I'd personally do small tests first with water and oils and soaps and the like.

The neat thing is if a direct negative casting were made of of the "personhole cover" using polyurethane foam, it would be very durable and very lightweight and quite ship-able, and you could make as many as you wanted pretty fast, once you had a good method.

But I do warn anyone about the importance of finding a good "release" through testing, because if one just sprayed this stuff on, it would stick forever and the only way to clean it out beside infinite scraping and cursing would probably be by fire, and it's nasty stuff when burned. So we don't want that.

I don't have any ideas about making a finished product resin positive cast from a polyurethane negative mold, because resin gets so hot while curing, and I wouldn't know what to use to keep the materials from melting together and bonding.

Okay, I'm thinking too much about this and I'd love to hear Dan's ideas before I ramble on like an idiot any further. Sorry. I just get a little exited sometimes.

Bwanna, it is so very cool that you have one of the Bell System covers. Will you be our mother?  Hee hee just kidding.
« Last Edit: July 18, 2009, 12:48:27 AM by HobieSport »
-Matt

Offline McHeath

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Re: Manhole cover
« Reply #33 on: July 18, 2009, 01:32:44 AM »
There must have been about a bazillion of these covers at one time since we are all finding them all over the USA.  I've also seen a couple here in my hometown since I first noticed that one over at a costal town.  Even GTE got into the act it seems, using the same basic design.  We had a foundry in my town back in the day, and many of the old covers list the name of that foundry and date.  The new covers are all made in India, which is an interesting economic puzzle to be able to make an item that heavy and ship it halfway around the world and still beat the local guys out on price. 

Just a house down from me the phone junction box covers still have the Bell System logo on them, and I know that were installed in 1998 as a guy was planting a tree with a backhoe and ripped the trunk cable up and apart, the covers were placed to shield the splices.  I recall that there were 4 PacBell trucks there for most of a day repairing the damage, and they billed the unfortunate backhoe operator about 2500 dollars for the work. 

To top it all off the transplanted tree died a year or so later. 

Offline Phonesrfun

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Re: Manhole cover
« Reply #34 on: July 18, 2009, 03:09:26 AM »
Those manhole covers are all over my town.  I live in what is now Qwest territory; formerly US West; formerly pacific NW Bell.  We have a combination of the covers, most with the more modern Bell system logo and some with the older looking bell.  I don't think I have seen any covers with either US West or Qwest, and I see a lot of them because in the summer I ride a motorcycle around this town of 40,000 (pretty small).

Maybe one reason for not seeing the more recent names on the covers is that the downtown area is where I see most of them, which was cabled underground massively in the 50's and 60's.

The neighborhoods were all overhead cables, and have been upgraded more recently with cables that are placed along side the road with green pedestals, rather than in vaults under the streets.

-Bill
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Offline bwanna

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Re: Manhole cover
« Reply #35 on: September 18, 2009, 09:31:39 PM »
thought i'd show a progress pic of the manhole cover clean up. in my spare time i have been using a torch to heat the ashphalt that is caked into the crevices. when i get done with that i will sandblast to remove the black from the heat & also rust.
donna

Offline Dennis Markham

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Re: Manhole cover
« Reply #36 on: September 19, 2009, 12:27:38 PM »
Pretty cool Donna.  That looks like a big job.  I heard on the news locally that the authorities were searching for responsible(s) in recent cases of missing manhole covers!

Offline Dan/Panther

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Re: Manhole cover
« Reply #37 on: September 19, 2009, 12:40:57 PM »
thought i'd show a progress pic of the manhole cover clean up. in my spare time i have been using a torch to heat the ashphalt that is caked into the crevices. when i get done with that i will sandblast to remove the black from the heat & also rust.

Donna;
You are doing all of this work yourself, Sandblasting etc. My kinda woman.
Looking forward to the molding process.
Keep us posted.
D/P

The More People I meet, The More I Love, and MISS My Dog.  Dan Robinson

Offline McHeath

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Re: Manhole cover
« Reply #38 on: September 19, 2009, 12:43:15 PM »
A lot of work but the results should be worth it.  Wish I had one of these covers, they are pretty artsy. 

Offline Dan/Panther

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Re: Manhole cover
« Reply #39 on: September 19, 2009, 12:59:14 PM »
McHeath;
As soon as Donna finishes the work, she plans to make a mold of the cover.
We hope it can then be cast is Resin.
D/P

The More People I meet, The More I Love, and MISS My Dog.  Dan Robinson

Offline bwanna

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Re: Manhole cover
« Reply #40 on: September 19, 2009, 05:52:24 PM »
LOL, dennis, you have been taking lessons from mc heath ???

just for the record. MY cover was bound for the scrap yard. i got it out of a salvage heap.

also, i must be honest & tell you all that the SO has done alot of the scraping. tedious work & he has more patience than me :o sandblasting will be a piece of cake. just gotta wear long pants ;D

d/p desires a resin cast. so once this is cleaned up i will try my hand at making a mold for him. if the mold turns out all right, i know dan has the talent to make the cast. :)
donna

Offline Dan

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Re: Manhole cover
« Reply #41 on: September 19, 2009, 11:12:42 PM »
I could pour dental alginate  in a garbage can lid and put the cover in it. Then you could pour plaster or paris or dental stone into it and make a perfect duplicate (the stone would be lighter too, than the cast iron).

This is similar to how I duplicated a mushroom cap for a WE P/U 500.
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Offline bwanna

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Re: Manhole cover
« Reply #42 on: September 19, 2009, 11:23:25 PM »
well, dan, we did not consider that process, since we didn't know where to get such a large quantity of dental alginate.

i found some type of material for the mold, that will be flexible when dry. since the cover is so heavy, it will have to lay flat in a form while the material is poured over it. there is a releasing agent used before hand, that will allow the cured mold to be peeled off the cover.

maybe dan will want some of that dental stone when he does the casting ;)
donna

Offline HobieSport

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Re: Manhole cover
« Reply #43 on: September 20, 2009, 12:50:23 AM »
I may be an idiot, but once you have burned and cleaned and sandblasted the manhole cover, please test a small area with any kind of thick oil as a release and then test some Polyurethane expanding foam, such as the product "Good Stuff" avilable in any hardware store in a small inexpensive can.

I don't intend to sound smarter that Dan/Panther (impossible) or Dan the dentist but I have molded human faces and I want to know what really works. What I love about "Good Stuff" (Polyurethane expanding foam in a can) is that it's cheap, fast, very strong, lightweight, and shippable as a starter mold.

Never use it on faces of course!

Just a suggestion but I hope you test it at least.

Alginate is the right stuff for every pore and detail, but not needed for a manhole cover.

By the way, I found the same cast of manhole cover in our small town here.

So if nobody listens to me, I'll probably get arrested for doing weird evil street experiments on it. I might send you a sample "test bit".

I'm not trying to prove a point; as if "my idea is better" or something like that.








« Last Edit: September 20, 2009, 12:58:09 AM by HobieSport »
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Offline bingster

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Re: Manhole cover
« Reply #44 on: September 20, 2009, 01:22:38 AM »
Never use it on faces of course!
Why not?  Slather Granny down with some Pennsylvania Crude, and shoot the expanding foam at her.  She won't know what hit her!
= DARRIN =