Goin' Crackers.

[shred]

Looks great! It's always really cool when they run on real steam.

You've gotta rig yourself a pressure gauge so you can see what's up when testing the safety and burner tuning-- doesn't have to be a little one, mine was a surpluscenter 200 PSI model, same as available at hardware stores for $15-20. there's not a pic of it in my thread except on the pump, but it's featured in the safety-test video- http://www.homemodelenginemachinist.com/index.php?action=dlattach;topic=2049.0;attach=1603 the pigtail pipe is to prevent live steam from damaging the works-- a U-bend would probably work as well.

 

[vlmarshall]

Very cool! :bow:
Hey! What are you doing over here? I need your help. :big:

Doing here? I figured I'd pollute my own thread with senseless ramblings for a change. ;D

Looks great! It's always really cool when they run on real steam.

You've gotta rig yourself a pressure gauge so you can see what's up when testing the safety and burner tuning-- doesn't have to be a little one, mine was a surpluscenter 200 PSI model, same as available at hardware stores for $15-20. there's not a pic of it in my thread except on the pump, but it's featured in the safety-test video- http://www.homemodelenginemachinist.com/index.php?action=dlattach;topic=2049.0;attach=1603 the pigtail pipe is to prevent live steam from damaging the works-- a U-bend would probably work as well.

Thanks, Shred.
I've got a gauge set aside, I guess I'll turn a fitting tomorrow. I really should build a test pump.

 

[shred]

FWIW, on the original 'Cracker' design, there is no 'safety valve' per-se. The spring and oscillator mechanism provided that. Personally I wanted a more positive safety, so I added one, but it never comes close to 30 PSI when the motor is running.

 

[BMyers]

very nice !
I have a question for those who have built the Cracker. Never building a steamer I don't see from the drawings how the steam gets into the engine and condensate leaves. I guess the drill jig for "ports" has something to do with that. But I dont see ports on the drawings.
Some pictures and advice would be appreciated because I think I am going to build the cracker, I need a reason to try out my new 10" Logan

 

[vlmarshall]

FWIW, on the original 'Cracker' design, there is no 'safety valve' per-se. The spring and oscillator mechanism provided that. Personally I wanted a more positive safety, so I added one, but it never comes close to 30 PSI when the motor is running.

Thanks, Shred.

very nice !
I have a question for those who have built the Cracker. Never building a steamer I don't see from the drawings how the steam gets into the engine and condensate leaves. I guess the drill jig for "ports" has something to do with that. But I dont see ports on the drawings.

Yeah, they don't actually SHOW the ports on the drawing, just a little drilling jig that you're supposed to build and drop over the assembled engine backplate and crankshaft. the top hole will line up with the correct drilling location at either end of the cylinder's swing.
I just sharpened one end of a small piece of drill rod, cut it to a length that would sit in the cylinder, barely sticking out of it's port. Then I rounded the opposite end, , left the pivot's spring off, and pressed the cylinder into the backing plate at each end of it's swing, marking the drill locations.

 

[vlmarshall]

Well, I turned up that test fitting, and plumbed a pressure gauge, and a diaphragm pump into the boilers.
I'd forgotten I had a 12v sprayer pump laying around, with a 60psi cutoff switch on it.

Still, I managed to peg the needle on on the 60psi gauge I dug up... and the pump leaks down to 45psi after 20 minutes or so, leaving me with a puddle of water, but I'm still grinning.

It's good to be another step closer to completion.

 

[zeeprogrammer]

Most excellent.

 

[vlmarshall]

It's alive! Test ran the second Cracker today, Chassis #1 actually, the one for my dad. I'm trying several burner sizes, so this run was on my Weller handheld soldering iron with torch tip.
[ame]http://www.youtube.com/watch?v=uakRJp4p7-M[/ame]

It's blurry, I keep forgetting the camera doesn't have Macro mode when shooting video. ;D

 

[rake60]

Looking Great Vernon! Thm:

Beautiful Craftsmanship!

Rick

 

[shred]

Looks good. What boiler pressure was the Weller able to make?

 

[vlmarshall]

Thanks Rick! It'll never compete with the stuff on here.

Looks good. What boiler pressure was the Weller able to make?

Not much pressure, wet exhaust... I don't know exactly, I sprung my gauge when I overpressurized it. It reads 7psi at zero, and was showing around 15 when running...but I wouldn't trust it to be a simple math solution. It's trash now.

No matter, the gauge was something I had left over from a coolant filter project, else I'd have used something with a larger range.

 

[vlmarshall]

I'll try again whith a real gauge, when I have the safety valves started.

Has anyone ever added a whistle to the top of a safety valve?

 

[shred]

I'll try again whith a real gauge, when I have the safety valves started.

Has anyone ever added a whistle to the top of a safety valve?

I considered it (I thought it would be kinda cool to have the safety blow through a whistle), but unless you make it big, it'll be very shrill and maybe not even audible-- The Gauge-1 train folks usually have a large whistle hidden underneath somewhere and a fake one on top.

 

[vlmarshall]

...unless you make it big, it'll be very shrill and maybe not even audible...

Yeah, that's what I thought. I've seen the hidden whistles (man, they sound nice), and as much as I'd like to have a big ol' multichime tucked under there, the idea of running my safety valve through a long tube doesn't appeal to me.

Still, the whistle on my old Wilesco engine is a 30mm long piece of 5mm OD tubing, and it's not TOO bad. I'm going to try it. I even drew it up with a remote release lever.

Worst-case, I have an odd-sounding valve, and I won't tell anyone it's supposed to be a whistle. ;D

I see why you ran your loco so much during construction, these things are a lot of fun.

 

[BMyers]

Very Cool !

Has anyone ever TIG welded a copper boiler ?

 

[vlmarshall]

Very Cool !

Has anyone ever TIG welded a copper boiler ?

A quick search online says "yes". I didn't try it with mine, My TIG skills in aluminum need help, and I imagine copper welds much the same way.

Yesterday, I rebored the cylinder for Cracker #2, removing a mark in the bore I didn't like, and giving me a reason to make a new piston. (bigger, and stainless) The first set of pistons were drill rod. I didn't oil one after a test run, and that was it; rust and pitting. I knew better. :-\

Other than that, no physical progress... just burner testing and planning, cab layout, and time spent drawing up a smokebox cover.

 

[BMyers]

I have tig welded a little copper. DC current, but it takes a lot of heat to get a puddle then you have to back off. I may practice on some scrap and see what happens. I did silver solder the crank on mine today and was happy with the results.

 

[BMyers]

Hey Vernon,
How about some pics of the banjo fittings and screws. How did you make those ?

 

[vlmarshall]

Hey Vernon,
How about some pics of the banjo fittings and screws. How did you make those ?

Sure thing! They're nothing special, at all.

The steam dome fittings, ( the larger in the pic.) are 5/16-24 thread, turned from brass stock, with a lot of extra material left at the head, because I may drill and tap them for either a relief valve, or a filler. (Or, I'll toss these, and make something more suitable.)
The ring portion of the banjo is just a chunk of Phosphur Bronze, turned and drilled. I used one of them for the temporary test line, and since I've read that you can't silver-solder over ANY soft solder, I won't even try cleaning that one, I'll just make another. I'll probably add a groove around the inside at the same time.

The inlet and exhaust port fittings are crap, just a drilled and turned piece of 8-32 bolt, some turned brass rings, and a couple of nuts that absolutely refuse to seal, always leaking around the threads. The next attempt will use either a cap nut, a bolt, or a straight compression fitting, if only I could find a supplier for something that small.
I don't want any of the lines to be permanently attached at either end; like I said in an earlier post, I'm planning for future maintenance.
Here's a shot of the fittings. Left to right, two leaky bolts, next time, stainless. two brass fittings, one soldered to a test line, a phosphur bronze steam dome fitting, and two steam dome banjo bolts.

Here's a shot of the inlet port. Nothing special here, other than the clearance notches I had to cut in the cylinder to clear the banjo fittings.
Also visible are the setscrew holding my pivot bolt in place, and the mica-block boiler saddles. The rear saddle bolts to the footplate, the front is captured between the smokebox and the footplate by a through-bolt.

 

[BMyers]

thanks Vernon,
I went 4-40 on the ports, figuring that was pretty close to M3. Hope I dont regret the decision