Another project, this one steam related, renovating old steam toy.

[J Tiers]

Unexploded Ordinance???, Bomb???? No more dangerous than pumping up a bicycle tire. I would thing the volume of air under pressure would determine the extent of "danger due to a failure". Just my humble opinion. Rick

Yes. A "bomb" may not be huge. But it can throw pieces around, and then also, it is destroyed. With water, if a leak occurs, in many cases the boiler can be repaired successfully, and it is just not a good idea to use air.

You want to test with air pressure, I guess "you gotta do you". I'll stay with water, and away from your tests!

[rickhann]

Sparky hit it on the head.. Fill the boiler with water, then use air pressure!!! to test, unless you are afraid of the air hose suddenly becoming weapon of mass destruction. A bit of critical thinking is in order. It's a toy! Rick

[J Tiers]

Sparky hit it on the head.. Fill the boiler with water, then use air pressure!!! to test, unless you are afraid of the air hose suddenly becoming weapon of mass destruction. A bit of critical thinking is in order. It's a toy! Rick

That's not as bad as straight air. Basically "air over hydraulic". With some flow limitation on the air, it's probably OK. But it just don't matter that it "is a toy". It is about a quart of volume, and if straight air was used, it could do some damage.

Remember, I have no idea if ther are any defects in it, and I have had to repair it. It might be fine, or it might go pop.

But I have the pump pretty much designed in CAD already. Now it gets the design finished and goes on the list. Seems like fun to make, and calculations say that at several times the pressure I need for this boiler, it will take less than 2 lb pressure on the lever to force in water.

I also have to make a bunch of blanking plugs to replace various fittings that won't be on there. Not an issue, have two sizes already done, have several of the third type left to do.

I may have to have the water gauge in place for the test, it is German, and has no boiler fittings for the gauge glass (see earlier photos). I may do a blanking plate instead, I don't want any chance of messing up the glass, I am no glass-blower.

[chipmaker4130]

As noted in post #58, just use a grease gun. The only fitting needed to apply pressure is a zerk. I've use one to hydro-test tanks and its dead simple. If you do a complete water fill, the amount of grease required to achieve pressure is minuscule and it will exit with the water drain. Or just go ahead and waste time making a one-time-use pump.

[J Tiers]

As noted in post #58, just use a grease gun. The only fitting needed to apply pressure is a zerk. I've use one to hydro-test tanks and its dead simple. If you do a complete water fill, the amount of grease required to achieve pressure is minuscule and it will exit with the water drain. Or just go ahead and waste time making a one-time-use pump.

It will NOT be one-time use, as-planned. I have intentions to do at least one or two more boilers, and intend to do some steam engines. I have materials for a couple fair sized all-copper firetube boilers. So, there is a reason to go ahead.

But, you know what? If I never get to those, I won't feel that the design and construction of this pump is a waste. No doubt that will result in a "mind blown" response (per Doozer recently) but that's certainly not "my" problem.......

Meanwhile, I have some blanking plugs to make, as well as a manifold for use in comparing pressure gauges, and checking safety valves of various sorts..

[J Tiers]

Hmph..... I got some of them done, but found that the last one was the size I had not obtained a die for. Got the tap, but the die was put of stock. It's an M5x0.5 thread, and I need to plug that hole, since that is the mounting for the gauge, and I do not want to have it in place for the test.

Maybe I'll try single-pointing it, although I usually avoid doing that below about 40 tpi, as the slop in the halfnuts approaches the thread pitch. I may still hold out for the die, since the entire length of thread is only 5mm or so, and needs to be threaded close to the head.

I made the rest of the ones I wanted. Here are some of them in the boiler (one would not be there due to needing a connection for feedwater to apply pressure). oddly, even though you could easily see the taper on the parting pip as it was being parted off, every single one of them broke off at the fat end, leaving most of the pip attached to the screw. I had purposely ground the tool to cut thinner at the part end, and fatter at the stock end, but it did not act as intended. Material was some hex stock I had that seems to be free machining.



And those same ones loose. They will get a gasket or o-ring for the test:

[J Tiers]

I did design what should be a good pump. But I did not have a suitable piece of bronze or brass, and so I had a different idea.

I don't need very high pressure for now, and I do have stupidly high water pressure. But the idea would work with most any workable water pressure.

You may be familiar with the resistive voltage divider.... it occurred to me that I can do a simple resistive water pressure reducer, since ideally I do not need any real water flow at pressure. All I really need is the "voltage" (pressure).

So, supplying the water through a small orifice (resistive), and having an adjustable "leak", should allow me to adjust for nearly any pressure in the range that I want. Pressure with the "leak" closed is obviously full pipe pressure, and with the "leak" much larger than the orifice is equally obviously essentially zero pressure.

So, with a needle type valve, I ought to be able to get any pressure I want between the two by suitable adjustment. Might be a bit fiddly to set, but that's not much of an issue. I can set it up, then open a valve between the pressure output and the boiler or other item under test.

Besides the boiler, I have some gauges that could use calibration, so I can get one with a suitable range calibrated, then use it as a standard for checking the others. * I just need to make a suitable manifold, which I would need to use anyhow, and screw in an inlet orifice and a pressure setting valve. Also needed is a standard gauge, and an output to whatever is being tested.

* In practice, I would likely use the principle that if two unrelated measuring instruments give the same reading for a given "input", they are probably correct. If a third one agrees, the probability goes much higher.

[PStechPaul]

Using that method for the boiler should be pretty safe. If there is a leak, or rupture, the small orifice or tubing will greatly limit to flow, and you'd get nothing more than a trickle. You should be able to verify operation of the gauge and also test whatever safety valve(s) are on it.

[J Tiers]

So, my friend who owns the thing has had most of the pieces trying to get a paint color match, since most of the paint is off of it. I'll work on it more when I get it back. I can still work on getting the generator fixed, I looked at it and found it was non-functional.

I did find the explanation for the rust, however. It turns out that the blow-down valve stopped working for some reason and got replaced by a bolt to close up the hole, back in the dim past. The valve got lost, of course. So did the lamp post that the generator operated, and the little set of stairs that used to be on the boiler..

Anyhow, the bolt was steel, and that would be where the rust came from.

[J Tiers]

Well, I got the M5 x 0.5 die that was out of stock, and the boiler is here, so I will have to do the hydraulic test now. I made the needed plug with the new die, and all that is left is covering the holes where the water gauge goes.

That guage has no pipe fittings, it is just holes through the flat brass at the end. There really is no "seal" for the water gauge, it had a close fitting rubber gasket that apparently slipped over the u-shaped gauge glass, and was held down by a bracket. Only the rubber being squeezed seems to have made any sort of intentional seal for the glass.

I can probably just tighten down a plate over the holes, with some rubber under it, and deal with sealing the glass tube later.

So, now I have to make a few parts... the manifold, a restriction for the valve to work against to adjust the pressure off of the 110 PSI local water supply, etc. Been lazy and putting that off until I needed these things.

The seal area



As assembled (before working on it). The rubber seal had cracked and failed.

[old mart]

I haven't read right through the thread, but the toy, being older German, might well have had a pressure gauge calibrated in Kg/cm2, One unit of is roughly equal to 14 psi. That system predated bars by many years.

[The Artful Bodger]

The traditional German unit for pressure was Atü which was basically 1 atmosphere, about 14.7 lb sq inch or 1000mbar (or 1 bar).

[J Tiers]

I haven't read right through the thread, but the toy, being older German, might well have had a pressure gauge calibrated in Kg/cm2, One unit of is roughly equal to 14 psi. That system predated bars by many years.

The traditional German unit for pressure was Atü which was basically 1 atmosphere, about 14.7 lb sq inch or 1000mbar (or 1 bar).

Look back and the units likely are bar or just kg/cm^2, I forget which the label actually probably says (it's not perfect as to the dial marks). That gives a max pressure of 45 psig, which I'd say was mighty high for a brass boiler with flat ends, all of 0.5mm thick.

The owner says that the gauge was pegged a number of times, so who knows? None of the safety valves appear to pop at an appropriate pressure.

[The Artful Bodger]

I somewhat apprenhensively suggest that the dial image in post number 7 shows a 3 letter word with the first character 'A'.

[J Tiers]

I somewhat apprenhensively suggest that the dial image in post number 7 shows a 3 letter word with the first character 'A'.

Don't be apprehensive, it probably is something like that. I have not looked at the gauge dial for a while, but the consensus seems to be that they meant 3 atm as the dial range. I originally thought that was way high, this being a kid's toy, basically, and the brass boiler being so thin that heavy doubler plates had to be added for all the places things screw in. More on the Mamod line than anything else.

But, late '40s and mid '50s..... people were expected to have some sense. I don;t know if that was any more true in actuality. Having grown up in the '50s to '60s, I suspect probably people were no better then than now, there were as many idiots then as now. They may have had considerably more exposure to mechanical stuff, maybe that helped. Dunno. My friend says he pegged the meter, and the boiler did not blow, so there you have it.

I have no clue as to the actual calibration of the gauge, just what is printed on the dial. I will need to make the gauge work, and calibrate it against gauges here. As my father-in-law likes to say, "I ain't too worried about that right now", I need to test the boiler, which means fabricating some stuff.

Didn't get squat done today. Spent all day waiting for the plumber to show up and estimate a repair. I knew that as soon as I got started, he'd be here and I'd have to stop. Turns out he got delayed, and is coming tomorrow.