Capacitive Water Level Gauge: Assembly Notes
The probe is an insulated thin wall brass tube. The insulation I have used is Teflon (PTFE) heat shrink tubing. To prevent some problems experienced with earlier versions, the brass tube should be perforated about every half inch. I suggest rotating the tube while heating the heat shrink tubing to obtain uniform shrinkage. I have tried several samples of heat shrink tubing and think McMaster-Carr catalog number 75665K62 is particularly suitable. A four foot length costs less than eight Dollars.
A second method of insulating the probe is to wrap the tube with overlapping layers of teflon tape made for pipe joint purposes. I have not tried this method, but it has been used successfully by another user of this gauge.
The bottom end of the probe is inserted in a Teflon insulator which is in turn inserted in a drilled hole in a quarter inch brass pipe plug. Red high temperature silicon rubber joint compound seals the probe from water leakage. As the probe is open at both ends, the silicon rubber is not required to be pressure resistant.
The top end is centered by its contact wire on the sparkplug used as the gauge's signal connector. I have used both the Autolite 4194 and the Champion J99, which is an industrial furnace igniter. The Champion is both easier to use and more reliable, it having a long electrode to which it is easy to braze an extension. The extension serves only to make electrical contact with inside of the probe tube and may be as thin as twenty gauge copper wire. A few slight bends in this wire will insure adequate contact.
As the usual spark plug gasket works poorly with steam and to obtain a grounding point for the cable, an O-ring retainer made of a tenth inch thick brass or steel is fitted on the plug. If the seat hole is 0.75 inch diameter, a 206 Viton O-ring will work. The grounding point is tapped 6-32.
I have used a length or one inch black iron pipe with ends and suitable connections welded on. The ends may be made of three eighths thick steel plate. A 1 1/2 inch hole saw can be used to make the end pieces. The top end can be tapped to take the sparkplug directly, 14 by 1.25 mm. thread for the Champion plug. The bottom end should be tapped one fourth National pipe thread.
The side fittings may be five eighths round steel rod, or short bits of 1/4 inch black iron pipe.. Drill them and the body of the gauge one fourth of an inch so a bit of threaded rod will hold them in place during welding. Afterwards, they can be drilled five sixteenths and tapped one eighth pipe thread.
For a ten inch gauge, a twelve inch length of pipe is suggested. Thus the side fittings can be an inch from the end and still be ten inches apart.
To keep the probe centerd while inserting it in the case. I used a long piece of thin (18 gauge) steel wire inserted first. After the bottom fitting is in place, the steel wire sticking out of the top hole will keep the probe tube in view. One may then insert the end of the connector wire in the probe, remove the steel wire and screw the sparkplug home, remembering to have the ground connector and O-ring in place first.
An assembled gauge should have an infinite electrical resistance whether empty or full of water. The empty gauge should have a low capacity, probably about thirty picoFarads. When full of water, the capacity should be roughly ten times as great. If the gauge is over filled so the water goes above the end of the insulated probe, it will short out and have a relatively low resistance. This will cause no damage either to itself or the circuit to which it is connected. As soon as the water level drops and the plug insulator dries, the gauge will work normally.
The circuit board has two potentiometers on it for calibrating the gauge. with the gauge connected but empty, adjust the potentiometer marked R2 so the meter reads zero. With the gauge full of water, adjust the potentiometer marked R4 so the meter reads full scale.
Stanley Mixing Tube Fires by Pat Farrell (aka SSsssteamer) SACA
NW Steam Clinic September 27, 2019
What are mixing tube fires? The mixing tubes of the Stanley steam car are where the vaporized fuel and atmospheric air mix to produce a combustible flame to fire above the burner grate. When the fire presents itself below the burner grate in the plenum, or in the mixing tubes below, that is not acceptable. This generally is called a mixing tube fire. What are the causes? Most common tube fires are started by a fire leak from around the burner to boiler seal. The pilot light inspection hole not being fire tight, as well as the super heater exit at the rear of the burner can also start mixing tube
fires. A fuel flooded mixing tube fire is usually caused by a flooded burner. The flooded burner can
be flooded either by the main fuel jets, or by the pilot light being out causing raw fuel to build up in the mixing tubes and plenum. Mixing tube fires can also be started by forcing the burner too fast at firing up and flooding the burner with raw fuel. Instead, preheat well and build a slow hot fire. Tube fires can be caused by the fire dropping down out of the burner and into the plenum by the way of a cracked burner grate. The burner’s slots or its drilled holes can become too big and therefore dropping the fire down through them and into the plenum. A warped or heat damaged burner grate can be the cause for the over-sized slots. The burner grate’s plenum not being sealed tight enough around the burner grate, can also allow the fire to descend into the plenum. Flooding of the burner plenum can be caused by using too heavy of fuel for the too large of main jets being used. Thin your fuel with gasoline or reduce the size of your jets to help reduce fuel flooding. This flooding is also a problem found at higher elevations where the oxygen is thinner. Sometimes, old fuel will refuse to vaporize, and until that fuel is disposed of, the old fuel will be a problem. Partially plugged main jets can cause drooling that will accumulate creating flooding of the mixing tubes. Misaligned main fuel jets within the mixing tubes can flood a side of a mixing tube and thereby flooding the mixing tubes. Also a resulting fog of vaporized fuel blowing back outside of the mixing tube can result in a puddle of raw fuel and an eventual tube fi re. The main jets vapor spray should always do a perfect bull’s eye inside of the mixing tubes. What should be done? A roaring mixing tube fire should be extinguished as soon as possible to prevent further damage to the Stanley burner grate. The first thing to do is to eliminate the fuel source by turning off your main burner valve. If I have a roaring tube fire, I prefer to quickly pull off of the road and try to let the excess fuel burn itself off in a small flame. Continued driving fans the tube fire making it a hotter tube fi re and possibly doing excessive damage to your burner grate. Sometimes if my mixing tube fi re gets too large, I will use my Halon fire extinguished to keep the fire from getting too big and doing collateral damage. Never use a powdered fire extinguisher in your mixing tubes as that will plug your burner grate up solid with extinguisher powder. To resume firing properly, the excess fuel has to be burned off, so a smaller fire is encouraged into eliminating the excess fuel. If the burner has lost its fi re and it is blowing raw fuel fog into the air, turn the main fuel valve off immediately and drive until the fueled smoke screen has subsided and then pull over to relight the burner. The first lighting attempt is to light the fire from the top at the smoke bonnet’s access door. To prevent your body from being burned, stand upwind from the fuel vapor cloud when lighting. Next is to check your pilot light at the peek hole for being lit. Light the pilot light if it is still out. What is the collateral damage? Too much roaring burning of a mixing tube fire will eventually crack your burner grate. Plenum fires can also destroy all of your refractory materials located in your burner. Excessive tube
fires with fuel left uncontrolled can eventually burn your Stanley up. Always shut off your main fuel valve when leaving your Stanley unattended. Try to shut off your main fuel valve a quarter mile before arriving at your destination. That should clear out any stored fuel in your steam automatic system and prevent your main fuel from later cycling on and drooling fuel while the Stanley is parked. What can be done to continue driving while tube fi res persist? Sometimes while on the road, a quick fix for tube
fires is just not available. To survive this problem and to continue driving, these steps can be taken. Reduce your fuel pressure so as not to create too much internal pressure inside of the burner/plenum area. Reducing your fuel pressure to below 100 PSI can sometimes get you home. Get your Stanley rolling up to about 18 MPH or faster before slowly turning on your main fuel valve. This creates a draft so as to keep the fire burning above the burner grate and not in the plenum or mixing tubes. Some Stanley's have a stack blower that can be used to duplicate this need for a draft. Before using your main fuel valve, by using your firing up valve you can gently bring your fire temperature up to a good
firing rate following with firing with the main fuel valve. If your burner grates become sooted up from tube fires and it restricts the passage of the air/fuel vapor, remove your main fuel jets and if you have one, use your steam enema with full steam to clear your burner grate of any soot. I have also removed my smoke bonnet, and by blasting down each fire tube with an air nozzle, I cleared the sooted up the burner grate below of its blocking soot. Once I was in a blinding dust storm that blocked my burner grate with dust. My steam enema saved me that day too. Hopefully something in my above SSsssteamer experiences will help you in your steam car adventures. <
From bill Bill Lloyd 2011
Only today I had actually made a start at sorting through all my own Dungog photos, apart from just picking out a few here and there – like the ones attached. I still have hopes of making a disc of all my rally photos of the past decade, but something always seems to interrupt the process. I’m sure it will happen, eventually.
The Model K was delivered here to Denistone in Sydney to give me more time to “bond” with it. It’s been stone cold since it left Dungog, but we’ll be taking it out again on Friday so a couple of friends from the Road Steam Engine Association can have a ride and officially certify it for its annual club registration. The Doble went back to Trevor’s for some new plumbing. Trevor’s currently on holidays somewhere in central NSW for a few weeks. I nearly killed myself getting ready for the rally. Now I’m killing myself catching up afterwards. One of my friends went to London on Sunday. Another left for Japan today. He asked if I wanted to go with him, as I did once in the past, but alas, I’ve used up all my leave points for a while.
I’ve asked the body people to get me the Model K paint colour code which Basil wanted, so please tell him it will be forthcoming in due course. They’re currently working on the 1915 Detroit electric, which was dropped off in the same truck which then loaded the Model K for Dungog. The Detroit springs and wheels need stiffening up in a few places, with powder coating on the wheels. Incidentally, I made contact with your friend Don Davidson, first to buy a reproduction motor plate for the Detroit and then to see about having some Doble hub cap badges made. I told him how much I had enjoyed both the articles you sent me about his Detroit and Stanley.
Best regards to you both