# are rivets waterproof



## nhoj (Sep 24, 2016)

Hi I'm just starting on my first locomotive build a Baldwin 2 6 0 and whilst waiting for castings to be made I'm working on the tender, I have the tank cut out ready to assemble and I notice that a lot of the fittings are attached by rivets to the tank, question is are rivets waterproof or do they need sealing with solder or something?
John.


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## Blogwitch (Sep 24, 2016)

John,

With rivets, you can effect a watertight seal by using what is called 'sphere of influence of a rivet'. It might pay you to do a search for this term as it might explain it a little better than I can.

Normally this is the area that a rivet seals around a correctly formed rivet. That figure is usually 4D, where D is the diameter of the rivet.
So an example is if you are using a 1/8" rivet and it is correctly formed then there is a circle around the rivet of 1/2" diameter (4 x 1/8"). So if you put 1/8" rivets in at a pitch of 3/8" between centres, the spheres of influence overlap and so forms a watertight (or airtight) joint. A much stronger and better sealed joint can be obtained by offsetting a double row of rivets.

Normally, with model boilers and such, because of their smaller sizes, people also silver solder the rivets and joints as well after forming, a belt and braces exercise, but if done well, then the soldering shouldn't be required.

Hope this helps a little.

John


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## Jasonb (Sep 24, 2016)

Usual way with tenders on locos and traction engines is top drill all the holes and hold the parts together with a few screws. When all are drilled take apart, deburr all holes and then tin* the mating surfaces with soft solder. 

You then rivit up the tender followed by reheating and applying flux which will then melt the two soldered surfaces into one, any gaps can have a bit of flux cored electrical solder run in. While still hot wipe the joints with a damp rag to remove any excess solder.

* tinning is the process of coating the surface with solder so clean it up with wire wool or a Scotchbrite pad, apply flux, heat and apply solder then wipe over teh area with a damp rag to leave a thin coat of solder. Treat any fittings and the area they fit against in the same way as the main joints

Don't try silver soldering the tender as the higher temperatures needed will make the plates distort


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## Foozer (Sep 24, 2016)

Large scale - say a 777 skin lap to which I have done a few, both .190 & .250 rivets were spaced 1 inch apart  - General rule was 2D min 6D max spacing with 4D as optimal. Would drill some pilot holes bout every 20th hole and cleco down, full size the thousand or so lap holes, countersink and debure. Mating surfaces were debured using a swipe of 320 paper - No material to be removed that would thin the skins. Buck tail side of holes could be debured to a max of .003 deep. Majority of external holes were countersunk according to rivet type. Sealant was applied to mating surfaces, laps clecoed down, sealant squeeze out everywhere  - Yuck stuff - Load rivits, tape em down and wipe sealant off internal [sealant on a rivet acted like a lubricant causing the buck tail to be overdriven or simply explode]  Had fancy buck tail gauges, general rule was 1.5D min 2D max for bucktail dia 1D min thickness - -Riveting thin stuff - Blah - Would always try to put the manufactured head against the thinest material, bucking the tail against the thickest - Thin stuff not ones favorite - Have like one shot at it - Too much force and the tail upsets the material, deforming it, not enough and the rivet work hardens - When absolutely had to buck to the thin side, often used cork over the rivet to spread the bucking force to the material itself - Thin stuff is the case where rivet length to achieve desired buck tail became one of tighter choice.

Was a skinny sh*t when I started at Boeing - I fit thru the wing tank access panels - Everything inside the tanks are sealed and god awful amount of small dia rivets . . . Quantity of Big Macs later and off to skin laps knocking down .250" rivets - Rivets like a tight hole, e.g .187 rivet to a .190 hole, larger hole and the buck tail will often club foot over - Done tens of thousands of good rivets that I don't remember, the few bad ones - - Well, when their bad, their really bad . . .


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## Mechanicboy (Sep 24, 2016)

In case there was leakage, the rivets and edge of plate was caulked to keep tight or the other alternative to keep tight: Use oatmeal or horse dung mixed into boiler water to spread around inside the boiler to stop leakage.


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## nhoj (Sep 24, 2016)

Hi guys, lots of information there, from horse manure to solder so I think I'll go with tinning the parts before riveting as JasonB suggests, thanks for your input,
John.


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## bazmak (Sep 24, 2016)

Tinning with soft solder is the correct way to go for the tender where no
high temps are encountered.Silver solder would be the correct way for the boiler and components


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## Wizard69 (Sep 25, 2016)

nhoj said:


> Hi I'm just starting on my first locomotive build a Baldwin 2 6 0 and whilst waiting for castings to be made I'm working on the tender, I have the tank cut out ready to assemble and I notice that a lot of the fittings are attached by rivets to the tank, question is are rivets waterproof or do they need sealing with solder or something?
> 
> John.




Well solid rivets can be.   I wouldn't rely upon open ended pop rivets though.   

The classic example of a riveted thing that needs to be water proof is the aluminum fishing boat.   There they use rivets and sealant to bring all the seams together.   The key of course is that the rivets must be properly upset tone tight in the joint.  

If this is steel upon steel construction, with steel rivets, you might want to do what was done with structural steel at one time.    That is to heat the rivet up and then upset it.   A red hot rivet is of course softer but it is also longer and will shrink a bit as it cools.   Properly install rivets make for a very good mechanical joint.  As for a hydraulic joint that is a different story but there should be little pressure in a tender tank.


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## bazmak (Sep 25, 2016)

I think the original question concerned model engineering for 
example steam locos where the rivits are nom 1.5 to 3mm dia
Caulking,heating etc probably don't apply


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## fltenwheeler (Sep 26, 2016)

Hi

On the tender for my Allen 10-Wheeler, I used non-harden Purmatex at the seams. I did not use any sealants on the rivets used to hold the stiffer on. Just a correctly driven rivet. The seam for the bottom  to the sides was soft soldered. 

I used copper rivets in galvanized steel. It's been 20 years without any problems. 

Tim


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