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  #11  
Old 02-09-2019, 02:09 PM
rvbuilder2002 rvbuilder2002 is offline
 
Join Date: Jul 2005
Location: Hubbard Oregon
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Quote:
Originally Posted by FinnFlyer View Post
BTW, these are old gel coated tips.

Finn
The older white gel coat tips are made with polyester resin (I think all of the current grey ones are as well, they are just made with a different type of gel coat).
Polyester resin is even less tolerant to high temps than epoxy is.
If you want to minimize the weight of the counterweight by keeping the mass as far from the hinge point as possible, I would recommend using plaster or something similar to make a mold the size and shape you would need, and then mold the balance weights separately. Then drill and mount them with bolts.
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  #12  
Old 02-09-2019, 02:25 PM
FinnFlyer FinnFlyer is offline
 
Join Date: Aug 2018
Location: Bell, FL
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Default Best plan

Thanks Scott, sounds like the best or safest plan!

Will also give me the opportunity to work with molds -- something I haven't done since making molds for wingtip lenses for my RV-3 back in the last century.

Finn
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  #13  
Old 02-09-2019, 04:19 PM
BillL BillL is offline
 
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Location: Central IL
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Default I did this too . . . you can do it!!

Quote:
Originally Posted by rvbuilder2002 View Post
If you want to minimize the weight of the counterweight by keeping the mass as far from the hinge point as possible, I would recommend using plaster or something similar to make a mold the size and shape you would need, and then mold the balance weights separately. Then drill and mount them with bolts.
+1

Properly heated lead will pour like mercury. Just take some old spoons and use them to scrape off the scum (dross) on the top just before pouring.

Plaster works quite well for the shape, you can make the blank from wax (or something) then make the mold around the correct shape. Slowly heat the plaster and get ALL the water out of it. It will pop and splatter the lead if it's not dry. I heated my molds to ensure the lead does not chill too quickly as it is being poured. If it does, it will look like the Vans counterweights(bad).

Once poured it does not take long for it to solidify. Old wheel weights make a good part, clean, smooth, & strong.

Good luck.
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  #14  
Old 02-09-2019, 06:48 PM
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dpansier dpansier is offline
 
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"Properly heated lead will pour like mercury."

I recall HS Science class where the teacher would pour Mercury into our hand and we would pass it from student to student, rolling it from hand to hand, only caution was not to drop it.
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  #15  
Old 02-09-2019, 07:17 PM
FinnFlyer FinnFlyer is offline
 
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Originally Posted by dpansier View Post
"Properly heated lead will pour like mercury."

I recall HS Science class where the teacher would pour Mercury into our hand and we would pass it from student to student, rolling it from hand to hand, only caution was not to drop it.
I don't think I want to do that with molten lead.

I received a posting reply by e-mail that does not show up when browsing this thread. Why would that be?

lr172: "Two concerns. One, The lead needs to be quite hot and I don't think it cools quickly. If it comes in contact with the F/G, I would expect some deformation and possibly charring. Two, What if you put in too much? How do you get rid of the excess?

I have an easily accessible block of lead that is only 1/2" from the forward edge of the horn. Not sure what you are gaining here. Is an ounce or two worth the risks?

Larry"

I'll substitute the F/G fairing with a plaster mold. That will make the original question moot because then I can pour from both sides.

I'll get rid of the excess the usual way, shave or drill it off.

I just measured it (adding a 5 oz bag in the middle if the elevator to simulate vinyl/paint). Left elevator requires 33 oz at 11" from pivot point, 41 oz at 9". 8 oz difference.
For the right elevator the difference is about 5 oz.
Perhaps I'll only achieve a 1" difference. But that's still 5 to 6 oz total. Consider how many hours spent with a fly cutter making lightening holes in ribs, spars, and so on, I think that's worthwhile, especially on a FP prop RV-4 that's notorious for being tail heavy with a passenger.

(Another possibility mentioned in an old RVator is to use lead shot in resin, but I'm sure I wouldn't get the same density thus negating the whole idea of moving weight as far forward as possible.)

Finn
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  #16  
Old 02-09-2019, 07:31 PM
Ezburton Ezburton is offline
 
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Location: MD
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Oddly enough, I am getting ready to pour some lead for a BB8 Droid which my daughter and I have been building. The dome (head) is attached magnetically to tower which pivots at the center of the sphere (big beach ball 3D printed part). The dome needs to have a significant counter balance (about 20lbs). I researched pouring lead and I here is what I am doing.

I 3D printed the shape of the weight and created a hydraulic concrete hemisphere using the print as a mold. Next, I when my wife was gone for a few hours, I put the 30 lb concrete mold in the oven and cooked it at 300F to get the water out. I plan on sealing it with high temp automotive silicone so it pops out of the mold.

I found 25# bags of lead shot on line and will be melting them with the hot plate I use to reconstitute epoxy hardener and a propane torch. You can buy $40 electric lead melting pots at Cabellas or on eBay if you don't want to work with a torch.

I also have some elevator counter weights to make for my Velocity. Figured I do the BB8 first before I did something that is more critical.

MTCW,
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  #17  
Old 02-10-2019, 12:13 AM
lr172 lr172 is offline
 
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Location: Schaumburg, IL
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Quote:
Originally Posted by FinnFlyer View Post
I don't think I want to do that with molten lead.

I received a posting reply by e-mail that does not show up when browsing this thread. Why would that be?

lr172: "Two concerns. One, The lead needs to be quite hot and I don't think it cools quickly. If it comes in contact with the F/G, I would expect some deformation and possibly charring. Two, What if you put in too much? How do you get rid of the excess?

I have an easily accessible block of lead that is only 1/2" from the forward edge of the horn. Not sure what you are gaining here. Is an ounce or two worth the risks?

Larry"

I'll substitute the F/G fairing with a plaster mold. That will make the original question moot because then I can pour from both sides.

I'll get rid of the excess the usual way, shave or drill it off.

I just measured it (adding a 5 oz bag in the middle if the elevator to simulate vinyl/paint). Left elevator requires 33 oz at 11" from pivot point, 41 oz at 9". 8 oz difference.
For the right elevator the difference is about 5 oz.
Perhaps I'll only achieve a 1" difference. But that's still 5 to 6 oz total. Consider how many hours spent with a fly cutter making lightening holes in ribs, spars, and so on, I think that's worthwhile, especially on a FP prop RV-4 that's notorious for being tail heavy with a passenger.

(Another possibility mentioned in an old RVator is to use lead shot in resin, but I'm sure I wouldn't get the same density thus negating the whole idea of moving weight as far forward as possible.)

Finn
I didn't fully read your thread before posting that. Upon re-reading, I realized that you had only cleco'ed the fairing on (I originally assumed it was rivetted on) and were using a barrier to protect the f/g, though not sure how the wood fits in there. Either way, after re-reading didn't feel my post was appropriate, so deleted it.

My lead chunk is only 2" wide, starting 1/2" back from extreme forward end. CofG would be 1.5" from edge vs yours which will be 1/4 or 1/2". So that is 3 oz. I did not go nuts cutting out lightening holes that weren't already in the parts. To me, it just wasn't worth 2-3 lbs savings. However, we all have different goals and appreciate your approach. My issue was really the risk of ruining the f/g parts in exchange for saving a few ounces. I questioned if that was a good gamble.
Larry
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Last edited by lr172 : 02-10-2019 at 12:21 AM.
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  #18  
Old 02-10-2019, 08:29 AM
FinnFlyer FinnFlyer is offline
 
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Location: Bell, FL
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Quote:
Originally Posted by lr172 View Post
...Either way, after re-reading didn't feel my post was appropriate, so deleted it. ...
OK Larry, but you certainly made a very good point on the fiberglass. Alum foil probably would not protect the F/G from deforming.

Finn
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  #19  
Old 02-10-2019, 03:53 PM
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G-force G-force is offline
 
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Location: Castaic, CA
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I couple of points about working lead. I've done a bunch of it, melting down wheel weight, scrap lead, gun range reclaimed bullets, shot, etc. for casting ingots, bullets, and fishing weights.

1) do it outdoors, its going to be smokey. Naturally wear protective gear.

2) you only need to get it to around 700 deg F. Any camping stove or propane stove will work. Never tried an electric hot plate.

3) Most lead is dirty and should be "cleaned" before pouring it. Melt it in a pot, toss in a bit of dry sawdust or chunk of candle wax, and stir. It will be smoky, probably catch on fire, but this "fluxing" will draw out the impurities (dross) to the surface where you can skim it off with a slotted spoon. Note to the poster who is going to be meting shot, i just did 37 pounds of shot and ended up with 32 pounds of clean lead ingots so expect to flux and remove alot of dros out of melted shot.

4) If your going to use a soup can or similar to melt lead, be warned they have a plastic coating in them that needs to be burned off with a propane torch before using. I would look to the dollar store or Goodwill and find a stainless or cast iron bowl for cheap. Also pick up a cheap stainless ladle and big spoon. Drill half a dozen 1/8" holes in the spoon for your dross scraper. Hammer a nice spout on one side of of the ladle for your lead pour.

5) Make sure your mold is 100% dry from moisture. Pouring hot lead on something with water in it was cause an instant and violent explosion as the the water steams off. Same goes for adding more solid lead to a pot of melted lead. Ensure everything is dry! If in doubt, heat it up with a propane torch or baking in an oven prior to putting it in the pot.

6) Dry wood will work fine as a mold. It will char a bit on thicker pours, but its pretty easy to work with mill or router to create the shape you need. You can also try and line it with high temp RTV sililcone. It has a working temp of 650 deg F so it will hold up enough for one or two castings. Again, ensure it is DRY by baking the wood in the oven at low temp to remove the moisture and sap. I haven't tried, but lining it with aluminum foil would probably work as well.

As with most things, if you youtube "casting lead ingots" you will find hundreds of vids on melting, cleaning, and casting lead.
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  #20  
Old 02-11-2019, 02:24 PM
Sylvester Sylvester is offline
 
Join Date: Mar 2017
Location: Uk
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Default Counterweight

Lead shot bonded with epoxy resin works very well. Difficult to hurt yourself too.
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