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Home made weights

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Old 12-11-2005, 12:17 AM
  #26  
mirwin
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Default RE: Home made weights


ORIGINAL: feep " . . . you can take some clean sand and press a cowl or other complex shape into it to make a crude mold that you can pour molten lead into . . . . . "

Feep,
I'm interesting in making a mold like this to make better use of space and a neater weight installation.
Could you expand on the sand process? For example, is there a particular kind of sand that's best? How does one keep the mold from collapsing when you begin pouring the molten lead into it.
Also, how do you melt the lead in the can? Put a torch under the can, or put it on a stove top?
If you prefer, feel free to email me at RCWarbird@yahoo.com
Would greatly appreciate any info you have time to share.

Mike


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Old 12-11-2005, 07:11 AM
  #27  
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Default RE: Home made weights

The best way to melt the lead is to use a camp stove outdoors to keep fumes that are toxic from you and others. Next best would probably be to use a propane torch. For the shaping part I would line the sand casting with aluminum foil, which will separate from the lead later on. Normally we simply pour the molten lead into spoons or measuring cups of different sizes to get a batch of different weights.

Someone earlier in this thread was amazed that a trailer ball weight was needed in any plane. The Balsa USA Northstar (seaplane) has a rear pylon mounted engine and requires quite a bot of weight in the nose for proper CG. To minmize tha amount of weight, one wants to put the weight as far forward as possible. The best way to do this on this plane is to hollow out the nose cone and pour lead into the cavity. Then whatever amount of weight needs to be removed - not usually much - can be done easily with a drill.
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Old 12-11-2005, 07:51 AM
  #28  
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Default RE: Home made weights

Jlnews answered the question as well as I could. Let me add that lead will melt at a very low heat so both methods are good. Stove top is perhaps safer.
Let me discribe a situation I used and you can gleen whatever info you can. I had a 1/4 scale Sopwith Pup that was tail heavy. WWl type are notoriusly tail heavy. With the CG being very close to the front of the aircraft you often have to add a lot of weight to balance them out. I took the cowl and pressed it into some wet sand. I than poured the molten lead into that impression and had a weight that was shaped to fit as far forward as I could put it. Just remember that if you must make engine adjustments you can not fly without the cowl.
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Old 12-11-2005, 09:04 AM
  #29  
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Default RE: Home made weights

A neater way to use lead where you don't have to melt and cast it is to look in your yellow pages for a gun store. If they sell shotgun reloading supplies they'll have bags of shot.

It's very easy to balance your model to find out what weight you need and where you need it. Then make a custom weight from the shot mixed into epoxy. Use aluminum foil to line the inside cavity of the model where you want the weight and fill the foil liner with your mix. Plastic spoons work good for the filling and you don't have to sweat cleaning them after. You can also use any kind of drink straw in your molding effort to put a cast hole into the finished weight for solid attachment to the model.

And I'd suggest quite strongly that you study the amount of weight you're adding and where you're adding it. However you cast your lead plugs, they're going to be putting a bunch of mass into an airframe that's probably balsa and maybe lightply or behind a fiberglass surface that was designed to keep the wind on it's other side.

With some of the epoxy/shot weights I've made one side of the finished product has been a much larger "bulkhead" of plywood. The ply is then used to attach the mass to the airframe. It distributes the stress. Needless to say, those weights weren't going into a/c in the nose where there already is airframe strong enough to handle lead weights.

Buying a bag of shot that looks like it's way more than you will ever use actually has hidden humor in it. I used up a couple of 25lb bags in one year. It was some years back, but I was in a fairly large club and the word got around that I would make custom weights. When the LHSs started giving out my phone number...... But truth is, if you plan to stay in this hobby, a bag of shot is a fairly sensible expenditure, especially with most everything swinging to ARFs.
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Old 12-11-2005, 09:12 AM
  #30  
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Default RE: Home made weights

Thanks for the details. The GP Super Skybolt I'm working on now will need an estimated 10 oz of lead in the nose but there's little room for it. Coincidentally, I recently came into a great deal of clean lead, probably 25 - 30 lbs. So I'm anxious to try molding the weight. I'll try it this afternoon if I can find some sand.


Mike
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Old 12-11-2005, 09:28 AM
  #31  
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Default RE: Home made weights

BTW, I cast lead and have a convenient setup for my casting pot and supplies. And I have only hot cast a model airplane weight once. The difference in effort between molten lead casting and epoxy/lead casting is tremendous. And molten lead isn't really something you should be handling in your kitchen.

Melting lead isn't like boiling water. The lead you find around (like wheel weights) is actually somewhat hazardous to melt. Most people who haven't done it don't expect it to pop and splutter. And when it does, it spits tiny chunks of very hot molten lead around. I've got a ruined jacket I wear when casting. It's got little holes in the sleeves.

And there is another detail about molten lead that's not often appreciated. Scrap lead often has tiny droplets of water trapped in it. When you're melting that down, with bad luck the water turns to steam and blows lead out of the pot. With good luck, it turns to steam and blows just tiny bits of lead out of the pot.

And if you are somehow very unlucky and have any water at all around the molten lead, and a drop happens to hit the lead, it explodes. Yeah, explodes. There is an incredible amount of heat in melted lead and that heat turns the water into steam so fast that it doesn't just poof away. It blows a little crater into the surface. It's not fun. Not even close to funny.

I wouldn't even dream of heating lead on a kitchen stove or in a house. The usual vent over the stove just had spagetti boiling under it right? Or what? Why take any chance.

Hey, we got enough to worry about with LiPos coming into the hobby, why would we want to mess with molten lead too.
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Old 12-11-2005, 09:49 AM
  #32  
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Default RE: Home made weights

Mirwin,
I get clean lead from a stained glass mfg that's a couple of miles from my house. The stuff is brandnew shiny scrap that has never been outside their shop. My leather gloves also have small holes in them just like the jacket.

It's usually a good idea to "cook" any lead for awhile before you turn up the heat to melt it, no matter how clean it's supposed to be, just to insure it's dry. And all the other horrors I mentioned are worth contemplation.

Casting is really a lot of fun. And it's really not a constant dodging of flying lead. I've done it for years and years and still am wearing the same "holy" jacket and gloves I adopted after getting a splatter on a bare wrist years ago. But it ain't something you do with your boy watching the fun while playing with the new puppy and it also ain't something you do casually.

It easily is something that your average sensible model builder can do, but it's also something that can be very unforgiving. I compare it to anyone learning to use CA. How many of us discovered that the stuff wicks really well and learned that when we glued our fingers together. If it had been lead.... But whatever.... I've described most of what any sensible modeler would like to know up front.

Oh yeah, a good side to molten lead. The deal about it's vapors.... it's greatly exaggerated. The poisonous fumes don't actually wick very far from the molten lead surface. They are heavy so usually only waft downward. You won't breathe them unless you lean down and sniff to see what molten lead smells like
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Old 12-11-2005, 12:12 PM
  #33  
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Default RE: Home made weights

If you don't have any tire weights around, just melt some solder into a blob. It's a lead/tin alloy.

Drill a hole into, say, a shaped tail block or wing tip. Make a tube out of aluminum the same diameter as the hole, then melt solder into the tube. Then you'll have a 'rod' of balancing weight you can trim to length. When you have it right, epoxy in the hole, and fill. The weight will be secure and out of sight.
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Old 12-11-2005, 12:19 PM
  #34  
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Default RE: Home made weights

Thanks, darock. I used to mold my own bullets on a regular basis but that's been 30+ years ago and I don't remember much about it. Anything that's hot enough to melt gets my total respect. I have a shop with a concrete floor so that's where I'll do my melting and pouring. I'm still thinking about the best method to melt it though. Wish I still had that old Coleman stove! I have two lead bars, each weighing around 15 lbs or so. Before pouring it, my buddy spend a lot of time getting the slag out of it so it's suppose to be pretty good stuff. I'll know when I g to melt a chunk of it. The sand though, I need to find some sand. Hate to make a run to Home Depot because it's in town about 15 miles away.

Mike
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Old 12-11-2005, 12:39 PM
  #35  
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Default RE: Home made weights

Isn't it a lot easier just to buy the stick-on weights from the hobby shop - as we do here in the UK?
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Old 12-11-2005, 04:29 PM
  #36  
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Default RE: Home made weights


ORIGINAL: Runway

Isn't it a lot easier just to buy the stick-on weights from the hobby shop - as we do here in the UK?
Theoretically, yes. But I personally have not had good luck with stick-on weights.

In the case of one of my planes, I needed 14.5 oz which calculates to 58 of those little .25 oz squares. I had those $%$@!@$% things stuck to every available surface forward of the firewall. Plus, they seem to eventually come loose, particularly when exposed to glow fuel residue. So I screwed them to their respective surfaces. But the lead doesn't hold a screw very well, especially around vibration, so they were always coming loose. And it was a very unprofessional looking engine compartment.

Only a few moments ago I finished molding my first "custom" weight. I rummaged around in my shop, and found a square tin rod about 36" long by 3/4" square (I think that's about 1.9 cm, right old chap?) I cut a 4" section from it, braced it vertically in a vice, and filled it with molten lead. It's too hot to handle now or I would have included a photo. The outside finish of the tin rod is chrome so, when it's mounted in the engine compartment, it should make a nice, neat appearance. No more unsightly mess. Sometimes I amaze me.

Thanks all for the super advice.

Mike

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Old 12-11-2005, 07:19 PM
  #37  
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Default RE: Home made weights

Mirwin, I'm glad my response helped you. I have never believed that my ideas were the ONLY way to do something. I learned that 30 years ago when I first joined a modeling club. What I like about exchanging ideas is that quite often someone will take idea and expand on it. What we often do is neglect our sister hobbies because we are not interested in them and many times there is a goldmine in what they have to offer. I first cast lead for a keel weight for a scratch built RC sailboat. I remember many years ago while in static modeling reading about a process that railroad modelers used called Photo etching. And just recently, while researching scratchbuilding spoked wheels, I discovered a special glue for attaching tires from RC car modelers.
Have fun casting. Don't get burned.
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Old 12-11-2005, 07:46 PM
  #38  
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Default RE: Home made weights

Speaking of exchanging ideas -- the comment about using shot gun shot reminded me of another use for shot. Put some in a zip lock bag and seal it then I put the bag in a couple old socks and tie the ends. I now have a neat weight to hold things in the shop or slip one over your plane tire/ axle in the trunk or where ever and it will hold your plane in place.

ENJOY !!! RED
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Old 12-12-2005, 10:49 AM
  #39  
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Default RE: Home made weights


ORIGINAL 12/11/2005 9:29:59 PM Post: mirwin wrote, ". . . . . . . molding my first "custom" weight. . . . . found a square tin rod about 36" long by 3/4" square . . .filled it with molten lead. . . . "
Here are two photos of the installation. The 1st photo shows the tin "vessel" that I used with the shorter section that I installed forward of the firewall and above the engine mount (2nd photo.) I used a 3/8" drill bit to remove lead from each end until I got the weight exactly where I needed it (10.7 oz.)

Now that I've figured out that molding lead isn't black magic, I'll use the process in all future work.

Mike
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