building model engine radiator

I am designing a radiator for a model engine.
Keep in mind that looks are more important than function.
The entire radiator (fins, tubes, manifold) will be made
from Stainless steel. The radiator will be about 5 inchs
square and 1/2 inch thick. There will be 4-5 tubes running
from top to bottom. I will press the 1/4 inch tubes through
60 pieces of .036 SS fins spaced about 40 thou apart.
I figure I will press the fins onto the tubes one at a time.
My problem is connecting the tubes to a manifold. Silver solder
might work but I'm not particularly good at it and I am very concerned
that the heat will tarnish the SS and I will not be able to polish
it after its assemebled. I am also concerned that 1250 degrees
will distort things and maybe cause problems.
I am wondering if I can use O rings to seal the tubes where they
enter the manifold. The manifold will be a square block of SS
drilled from the end for coolant passage and drilled from the side
for the tubes. The difficult part is cutting O-ring groves
for the 1/4 inch tubes.
First; Will this work? ie NOT leak. The cooling system will not
be pressurized but there will be some pressure from the circulating
pump.
Second; How do I cut internal O ring grooves so that it will
seal when a 1/4 inch SS tube is pushed though it.
I have a wide varity of metal working tools available. I can
cut the o ring grooves with a boring head on the mill or by
mounting the manifold on the lathe faceplate.
chuck
Reply to
Charles A. Sherwood
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Yes, it will work, but you must make the gland to proper specs, and be certain that the tubes have a radius on the end so they don't cut the O ring when it's assembled. The entire assembly should be rigid and not flex if you intend for it to seal permanently. When you machine the gland to specs, it seals, you need do nothing else. As long as you can do something to prevent the tubes from losing contact with the O ring, there's no reason for the concept to work, and quite well. Roundness of the tubes, and surface finish shouldn't be overlooked, either.
I trust you're using 303 stainless. Pretty much any other grade could prove a bitch aside from 416. Cutting the groove will be hard because of the small hole size, which will limit the size of your bar. Aside from the setup, it will be much easier on a lathe than on a mill with a boring head unless you have a facing head. If you have one of those, the mill might be easier because of setup. In either case, you can go so far as turning the spindle by hand to avoid chatter. Love to hear how it turns out.
Harold
Reply to
Harold and Susan Vordos
My old Honda Silverwing motorcycle had a bunch of tubes and o-rings in the cooling system. They needed to be replaced every few years. Given the hard service they received, I think it was a good application and they should work fine on your engine.
Reply to
Jim Stewart
Are the specs in the Machinery handbook?
I bought 304 tubing from Mcmaster carr. I have not ordered the material for the manifolds but I was planning on 303. 416 would be a bit easier to machine but its not quite as shiny.
I could change to 3/8 tubing, but I already have the tubing and I can't return it. I have tubing with 35 and 50 thou wall. I figured the thin wall might compress when I press the fins over it so I was planning on using the thick wall tubing. Is that a possiblity? I guess I will have to try and make some O ring grooves and see what happens.
I don't have one, but I'm not against buying one if it makes my life a lot easier! Seems to me that I could drill the hole and then change to a boring/facing head to cut the groove. Much easier and more precise (using a DRO) than positioning the manifold on the lathe to cut the groove.
chuck
Reply to
Charles A. Sherwood
"Charles A. Sherwood" wrote: (Clip)Silver solder might work but I'm not particularly good at it and I am very concerned that the heat will tarnish the SS and I will not be able to polish it after its assemebled. ^^^^^^^^^^^^^^^^^ Before you go to all the trouble of machining all those O-ring fittings, why don't you talk to someone in a plating shop? They may have a way to clean off the silver solder discoloration--possibly chrome, silver or nickel plating as the final step.
Reply to
Leo Lichtman
I'd use some SWAGELOK 1/4" SS fittings if you can find them.Or some other brand. I used these for all sorts of hot,ugly applications( steel mills are not the cleanest places).Probably get 'somehing' from a highend auto parts supplier, HVAC distributor,saltwater aquariums, RV parts/dealer ? Jay
Reply to
j.b. miller
Greetings Chuck, Instead of silver solder why not use soft solder made for stainless? I've used the stuff befour and it works very well. The stuff I used was made by EUTECTIC. I don't know if they are still in business but a web search is bound to find a source. An easy way to solder all the tubes at once would be to use a hot plate to heat the assembly. Then apply the solder to each tube. ERS
Reply to
Eric R Snow
All State 430 is an example of this stuff that I've used...
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Im sure Harris makes an equivalent and likely a few variations as well.
Ned Simmons
Reply to
Ned Simmons
If you are using thick wall tube just put the O ring groves in the tube. You could even swage an O ring grove in the tubes and not cut. You would still need a sholder for the tubes to butt against in the manifold and something to tie the upper manifold to the lower manifold on both sides. Glenn
Reply to
Glenn
I would look into doing it an easier way, like drilling tapered holes in the manifold and pressing the 1/4" tubes into the taper to seal them.
Reply to
Nick Hull
Or epoxy, with which I have repaired several auto radilators. Don Young
Reply to
Don Young
Could you make your headers in two pieces? I'm envisioning using the square block of SS like you are curently planning, but with a recess on the tube side at all but the edges and a sheet of SS let into the recess. In the sheet SS cover would be holes for your tubes, in the main manifold would be holes and counterbores appropriate for your O rings. I'm not sure what the best way would be to hold and seal the covers. There isn't a need to seal the whole cover, just around the edges will make it water tight. Maybe some of the silver bearing soft solder would work, just aroung the edges (although I've never used it with SS). Another obtion would be a thin line of the RTV-like gasket material that is used for engine gaskets. With good fits, the seam should be nearly invisable. You could also take a skim with the mill across the cover plate to make it more invisable if the plate is thick enough.
Dick Morris Anchorage, Alaska
Reply to
Dick Morris
I would use a low temp silver solder line Allstate 430 and then soak it in some hot Citrisurf 2250 to get the color back.
Reply to
Glenn Ashmore
Not to my knowledge, but you may find something online. This link may be helpful.
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If not, Parker Packing publishes a booklet with engineering specs for glands of all designs. You might be interested in acquiring one for your personal use.
The difference between 416 and 303 are not enough to concern you regards machining, but if you choose 303, Se has a slight edge over 303 S in that regard. Any of them would be a good choice.
My personal choice would be to put the grooves in the blocks, not on the tubes, although if you use the .050" wall, it would probably work fine. You'd have ample material left after cutting the groove. Regardless of which way you go, remember to have a gentle radius on the parts where appropriate, so you don't shave the rings when you assemble. The gland should have relatively sharp edges to prevent extrusion, but that won't be much of a problem under your conditions. No pressure. Depth of your groove, using a 1/16" cross section ring wouldn't be very deep, and cutting it on the tube would certainly be a lot easier than internally. For scale sake, you'd probably like to stick with the ¼" tubing, maybe even smaller, so I think I'd go with what you have already purchased.
The idea of soft soldering sort of appeals to me. You might consider that excellent advice, which has been offered by so many. I've never experienced soft soldering of stainless, but have done a little silver soldering. For a job like yours, silver solder isn't well suited unless you have considerable experience soldering. Distortion and failed joints, along with considerable discoloration would be a problem. If you happen to over heat the joints, it's almost impossible to get the solder to take. Silver solder is a wonderful way to go, but requires some skill for success.
That was my idea, more or less, but with a little creativity you could make a lathe setup that worked quite well, saving you the cost of a facing boring head, and they aren't cheap. A good name brand can cost in the high hundreds. Sure would be a good reason to add one to the shop, though!
Assuming you end up doing it as we've discussed, and on your lathe, you could locate the bores within a thou or two simply by a pin in the tailstock chuck, locating the block on location while you snugged your clamps. A dial indicator in the hole and some light tapping once the block was lightly clamped would bring it right in, at which time you'd tighten your clamps. You'd have a lot better success that way than with a boring head, depending on how rigid your lathe and mill are. Hard to say without knowing what you're using. For me, it would be much easier to control the cut. YMMV.
Harold
Reply to
Harold and Susan Vordos
I did some browsing in Machinery handbook and MSC catalog. MSC catalog list various O-rings and they were all .060 thick. The machinery handbook suggests 20% compression so I would have to cut a groove about 50 thou deep. Not going to work in 50 thou wall tubing. However Mike told me that there are thinner O-rings available. Apparently as thin as 40 thou. That would leave a 18 thou wall in the 50 thou tube which should work.
Me TOO! I didn't think it was an option until it was suggested here. I will order some and experiment with it. Apparently the key is the flux.
I have just enough experience with silver solder to understand that it is most likely beyond my abilities! The scary part is when 1 out of 4 joints leak and next to impossible to get things apart to try again.
I have a rockwell 11x24 lathe and a myford super 7. I would probably use the rockwell for this job because it is quite rigid. I also have a rockwell Horizontal/Vertical combo mill and a mill drill. I think either one is capable of turning a boring head.
I agree that the lathe would do a better job, but the setup time would be a lot more.
Reply to
Charles A. Sherwood
Use Harris Staybrite silver-bearing solder. It is considerably stronger than lead-tin solder, wets stainless readily, works at 430F and is a good color match for stainless. Use Harris Staykleen flux or ordinary tinner's fluid.
You could flux the joints, make little preform rings of the solder, place the rings around the tubes where you want the joints and heat the whole works in an oven. When the solder melts it will mostly wick into the joint leaving a very small and perfect fillet. Try a practice piece or two first to see how this works.
It is also available in preform rings but you might have to buy way more than you need to get them. I'd go with the 3/64" dia wire.
Reply to
Don Foreman
Don sez:
"Use Harris Staybrite silver-bearing solder. It is considerably stronger than lead-tin solder, wets stainless readily, works at 430F and is a good color match for stainless. Use Harris Staykleen flux or ordinary tinner's fluid."
Right on, Don! The same soldering components are supplied with boiler kits from PM Research.
FWIW - Radio Shack used to carry "special" solders. Dunno, they may still do. Their Stainless Steel Solder (Kester Brand) has a "special flux core" and melts at 460 deg. F. On the package it is advertised "for all stainless steel repairs".
Also available from the Shack, is 4% silver, 96% tin, "silver solder" with a melting point of 440 deg. F, Keyster brand; advertised as "high strength for jewelry, antique silver". It comes with "organic acid and chloride salt" flux core. I'm reasonably certain this is about the same as Harris Staybrite recommended above except that it has a flux core and doesn't require the Staykleen flux. It'd probably be a good idea to use the Staykleen flux any way which is dilute hydrochoric acid.
Bob Swinney
Reply to
Robert Swinney
Pretty close. I think Staybrite is 5% silver, balance tin.
The flux is "killed" HCl; HCl that has dissolved all the zinc it can hold.
Reply to
Don Foreman
Really. I got one of them kits. I have been tempted several times to steal the solder out of it for other projects. Now I know what to buy.
You guys are amazing. Thanks for the advice.
chuck
Reply to
Charles A. Sherwood
Where can I order Harris solder and flux? MMC doesn't specify brands and the silver solder that I have ordered from them was made by some unusual company. I'm pretty sure MSC doesn't carry Harris.
chuck
Reply to
Charles A. Sherwood

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