Question:

What grade of Stainless Steel is best for Turbine Exhaust Tubes in a model ?

Or what do you use if you are making your own ?

Thanks.

Well has anyone got a view on this.

What grade: 316, 321, 304, 303, 325, 416, 431, 430, or 310. Just would like to know.

In all my jet books it just refers to making the pipes from "stainless" without an alloy #, but from my research I would think 310 or 316 (more commonly available where I am anyway) would be more than adequate.

Many KJ66 combustion chambers and tail cones are made from 316 SS so it woul also do the trick for the pipe.

AJC

I use 316 for all of pipes I make.
Roger

ajcoholic, jetjock50



Thank guys for that . . . . . Now I can do some work on my pipes.

I am using 316 grade SS anywhere from 0.15mm to 0.25mm thickness will do.

Nice and easy to form and you can cut it with a pair of normal household scissors.

Don't make my mistake and get caught doing it with the Wifes!!

I made my own Spot Welder after help from another RcUniverse
colleague using a transformer from a microwave oven. toal Cost
$4. Welds above SS a treat.

"I made my own Spot Welder after help from another RcUniverse
colleague using a transformer from a microwave oven. toal Cost
$4. Welds above SS a treat." - purge 98


Where can I get the plans for this Spot Welder? Any pics?

wled123

I'll email you a picture and instructions later today.

Gotta go to work now.

Jason

Type 316 SS is chemical resistant and generally used for high corrosive applications such as photographic equipment. Type 321 is usually used for high temperature (800-1650F) applications such as aircraft ducts. 310 also fits the bill. All of these are readily weldable and will work for your application.

The AMT turbine manual, specifically recommends 316 ss for tail pipes and a few hundred tailpipes later, I have yet to hear of any of the pipes I make failing.
Roger

purge98,

I've GOT to see those plans! It sounds like something that I need to try. Give me a PM regarding the hombuilt spot welder.


John

Its really not that hard to make one. I didnt have plans, but in Kamp's book on making turbines (and also in Shreckling's book) he discusses it briefly.

They tell you what KVA rated transformer to start with, and also what the secondary voltage range you should work to get.

I found a large transformer, cut off the secondary winding and rewound mine with 2 and a half turns of HEAVY wire (about 1/2" core) I got from the local industrial motor shop. It was trial and error for me, but after a few tries settled on the 2 1/2 turns.

I used a toggle clamp, and 3/4 square aluminum 6061-T6 for my arms, 1/2" diameter copper I turned into tips and have the whole thing mounted on a piece of wood. Momentary push button switch. I dont have a timer, but depending upon the thickness and number of layers you are welding you get to know how long to hold the switch down for...

If anyone is interested I can take a photo of mine and post it.

Andrew

Please do!

Here's a web site with homemade welder instructions. I'd like to see info on the ones guys heree have built as well.

http://www.5bears.com/welder.htm

I went to my local junk yard and scrounged an old broken Microwave oven.

On opening it up, first short out the large capacitor in there with a screwdriver. Don't want to blow a hole in your heart do you?

Remove the transformer, one of the mains rated microswitches and mains lead and plug. Junk the rest.

Test the primary windings (thicker ones) on the tranny with a multimeter for continuity. Most Microwave ovens stop working 'cos the Magnatron blows up so you should have a serviceable tranny!

If the primary is ok, then spend 2 hours drilling, pulling & cutting the secondary windings (thin ones) off the tranny. Try not to damage the laminated core too much.

Next find some heavy duty cable about 1/2" core diameter multistrand for ease of bending. Feed into secondary holes for one turn. See picture below. You are trying to keep the voltage down as low as possible and the current as high a possible.

Next make pincer type contraption out of non conducting material (eg. wood) and connect wires to probes, pref. copper.

I used two bolts with 1.5mm holes drilled in them and use 1mm copper wire as the probes. They concentrate the weld down to a small area and work fine for SS up to 1mm thick. They are easily removeable and replaceable.

I used a microswitch (see picture) to turn the primary on and off to make timing easier as the metal glows red hot in about 1/2 second.

Hope this helps.

Total cost:

Tranny $0
Microswitch $0
Wire $2
Wood $2
Mains plug and cable $0
Bolts $1
-----------------
$5 max.


Have fun and NO Ted Bundy's!

Jason

more pics

more pics

more pics

more pics

Last one

OK I will!

Here is a shot of the welder...

the other side...

and a close up of the transformer.

It had an "H" type core, easy to cut away the secondary coil as it isnt wound onto the primary like so many.

For my secondary heavy windings, I actually used two lines of the heavy stranded wire (2 or 3 ott). 2.5 turns as stated before. I am also running my primary on 220V. secondary voltage (no load open) is only about 3 volts.

I used a heavy duty toggle clamp as you can see, and bolted the aluminum arms to it.

For spot welding into confined areas I disconect the wires off the heavy arms and use a smaller set of tips I hold by hand.

Works really well and is something you wont know how you did without!

Andrew Coholic

OK, so who wants to do a rundown on tailpipe basics? First thing I'm wondering is the spacing between welds? Next thing is how/where you get a bellmouth?

I wonder if a stick welder could be used as a amperage source for some homemade spot-welding jaws...

Ajcoholic, where do you get the toggle clamp? Thanks.