A couple really busy years have passed since the last major improvements to the Shay ---- volunteer teaching trips plus design of a new house have limited the activity with the Shay. We moved into the new house at the end of August and the shop was operation in operation a couple weeks after. (An update of the shop description is a good project for the cold winter.)
Meanwhile --- the construction at Mill Creek Central Railroad has proceeded at a brisk pace with the completion of the Mountain Division reverse loop in late spring 2008. See the Track and Structures and 2008 Construction pages at www.millcreekcentral.com. The elevation graph below shows the killer grades at MCC.
This fall I fired up the Shay and tried it up the big hill ---- from Barney Yard up Wilson Siding, through Varian Tunnel, across Tower meadow, over the trestle and up the final grade to the peak just beyond the gas well. How did it go? Embarrassing! The Shay had to go very slow ----- like 5 scale mph. I couldn't add water on the grade or would loose pressure and would have to stop to rebuild it. Had to stop at Tower siding to add water to the boiler and rebuild pressure.
The Shay has been able to make the grade from Daffodil siding to Barney yard with no problem. I usually stop at the yard to add water to the tender so it was no problem if I got there with low water in the boiler and low steam pressure. The big difference is that the grade to the gas well is much longer.
Note that between Daffodil siding and Barney yard the track climbs about 15 feet in a distance of about 1300 feet. By contrast, the climb from Barney yard to the high point just beyond the gas well is about 35 feet in a distance of about 2700 feet. It's clear that the performance on the long grades is limited by the ability to generate steam. This is not a problem on a railroad with limited grades --- the Shay can easily pull ten or more cars on flat or nearly flat tracks.
The simple solution is to just open the oil valve. Unfortunately, increasing the oil causes the fire to smoke and quickly soot the tubes --- little extra heat is generated. Increasing the blower pressure helps some but the steam through the blower is lost --- it would better used to drive the pistons. The exhaust seems to have little effect on the draft --- not what one would expect.
The biggest problem seems to be insufficient draft. The first step was to take a look at the smoke box to see if there was a way to improve the draft.
The effect of the changes to the petticoat was very significant. Previously, the blower pressure had to be set to 30 psi or greater to prevent significant smoking at the lowest fuel setting that would provide a stable fire. After the change the burner would operate at below 15 psi blower and there seems to be a greater range of useful oil feed and blower settings. At the track I found the performance on the big hill was much better ---- it was no longer an embarrassment. With these changes to the petticoat the exhaust provided some draft and the blower could be set to about 10 psi with open throttle.
Dick McCloy suggested that we run a test with the atomizer and blower supplied from a portable air tank --- the Shay plumbing is such that air can be supplied to the atomizer and blower for startup. We charged a ~10 gallon portable tank to ~ 100 psi and started up the hill through Wilson siding with the blower pressure set at 15 psi. The tank was essentially empty before we got to the tunnel. The message is clear --- the blower really sucks the steam --- we should try to generate more draft from the exhaust.
These modifications really improved the power. The Shay pulled the 6 cars shown above with a husky engineer and brakeman up the grade to the gas well without stopping. The speed was 5 to 10 scale mph on the steepest grades and 15 scale mph or greater on the milder grades. I was able to add water as we went along and had a full boiler when we got to the top. One thing was different --- the axel pump couldn't quite keep up with the consumption ---- maybe I'm able to burn more fuel. I used the steam powered pump to add some water when we went through Tower siding. The smaller exhaust nozzle greatly increased the draft ---- I could both turn off the blower when the throttle was open and also increase the amount of oil slightly. The smaller nozzle also produces a more pleasing exhaust sound. There was one problem ---- the fire blew off more often. On the other hand, it seemed to be easier to relight with the igniter. Just after this photo was taken, the operation became more erratic--- the fire seemed to be too lean and completely opening the valve had little effect. The fuel filter was blow out at the beginning of the day but it seemed to be partially plugged again.
It was decided to take the shay back home to exercise it on the test stand to try to make the burner less prone to blowing out. (It may be that the filter was partially plugged and the fire was too lean.) Dick McCloy had another suggestion --- attach the output pipe from the axel pump to the under side of the fire pan to make a feed water heater.
So --- I leaned that when the fuel filter plugs up, microbes are probably growing in the fuel tank. The fuel should be drained and the tank cleaned. It's probably a good idea to drain the tank each fall and clean it. That should fix the problem since it seems to take several years to get the growth started. ( I also learned that the odor from the diesel fuel I'm using can linger in the house for many hours and some women find that odor unpleasant.)
After cleaning everything and putting fresh fuel in the tank I fired it up on the test stand (bearings under the wheels).
All the problems with the fire going out seemed to have gone away. The fire would burn with essentially no smoke at 10 psi blower setting and a low fuel setting. The fuel valve could be fully opened and there was very little smoke with the blower at about 30 psi. The burner seems to be about 2:1 range from low to high. The limiting factor for the amount of fuel seemed to be the fuel nozzle itself. This is good news ---- I seem to be using the full capability of the nozzle. It also tells me that the under construction Heisler which is a bit larger than the Shay should have two oil nozzles.
The exhaust was able to provide sufficient draft and the blower could be shut off completely when the throttle was partially open. Opening and closing the throttle did not cause the fire to go out except at the lowest fuel settings.
The oil feed line was under the fire pan. I tried pushing it up against the bottom of the fire pan. The operation seemed to get erratic --- so I concluded that running the line below the fire pan with a little gap provided about all the oil heating that can be tolerated and still have reliable operation.
During this test the holes in the sides of the firebox were covered. I uncovered one of the holes to see if the operation was different. There was not a significant difference good or bad. However, with low draft settings the fire would shoot out the side through those holes. That is not so good so it was decided to keep those holes covered.
While writing this up I realized that it sounded almost too good to be true ---- especially the fact that I could completely open the fuel valve and not get much smoke. I decided to test it again to make sure before making any other modifications. I blew out the fuel filter to make sure it was really clean. I also topped off the fuel take so I'd have maximum fuel pressure.
It was a cold day --- 26 F at 10 AM when photo above was snapped. This is just outside the shop door. (Earlier in the day a bunch of ducks were swimming in the lake. Don't understand why they didn't fly south for the winter. Maybe I should take pity on them and invite them in for dinner --- they are great with a cherry sauce.)
With the full oil tank I was able to make the fire too rich. However, even when too rich it didn't seem to smoke as much as before the modifications. With the very cold weather it was difficult to tell whether the exhaust was all steam or whether there was some smoke. In any case, I can't think of anything else to do to generate more heat from the burner.
I ran the axel pump a little during this test and was reminded of the cooling effect of adding water so that probably the best next improvement to work on.
When I took everything apart to make the feed water modifications I also cleaned the tubes. There was considerable soot. I suspect that the soot accumulated on the previous outing when I was having trouble with the plugged filter and the burner going out a lot. I also recall that I forget to add the RED DEVIL SOOT REMOVER the last time I filled the fuel can. This is probably a good reminder to not get too cavalier with the oil mixture.
Photo above shows the fire pan after the water feed lines have been routed through it. The copper tube down the outside is the oil feed. The smaller stainless tube only visible on the left is the atomizer steam feed --- it is unchanged from the previous photos. The stainless tube across the top of the photo is for the feed water from the steam powered pump ---- this tube was previously unsuccessfully used for heating the oil feed. The U shaped tub is for the feed water from the axel pump. The atomizer steam tube is 3/16" OD and all the other tubes are 1/4" OD. All the tubes are connected with compression fittings to facilitate removal for maintenance.
The modifications were tested on the test stand before making the trip to the track. It was about 35 degrees F during the test. I used an infrared thermometer to measure the following temperatures while the boiler pressure was about 110 psi.
The boiler and smokestack base temperatures are a little low for 110 psi pressure ---- ~340 degrees would be expected and indeed temperatures near 340 degrees have been measured on warm summer days. Guess the cold temperatures had some impact on the measurements. Previously, the top of the smoke box was quite a bit warmer than the boiler ---- the holes in the smoke stack at the top of the smoke box probably allow those hot gases to escape. Don't know whether that is good or bad.
The feed water heaters did work --especially the axel pump heater. The tender had been filled in the shop so the water temperature was probably about 60 degrees. The temperature of the output of the feed water heater was measured by shining the infrared thermometer on the water tube about 6" from the fire pan. Based on the measurements, the cooling effect of the feed water from the axel pump is reduced by at least 50%. The next step is a field test on the big hill at Mill Creek Central.
Went back to Mill Creek Central for a final test run on the Sunday before thanksgiving. It was a few degrees above freezing when I did the run. I had one car attached with two passengers. The performance was very good in that we made it to the peak just beyond the gas well with essentially full pressure and a boiler full of water. We made good speed on the way up --- ~10 scale mph on the steepest grades and about twice that on the less challenging grades.
I seemed to be able to burn more fuel without significant smoking. Dick McCloy commented that these was much less of a trailing oil smoke stench. The burner operation seemed very stable. It only blew out a couple times, each time apparently due to a too lean of mixture ----- as the oil level in the tank goes down, the valve has to be opened more. The total run time was about an hour. I ran with some blower -- about 10 psi even when the throttle was open some.
The feed water heaters did work and contributed to the performance.
After the run I cleaned a few of the tubes and found a little soot. This probably happened when I ran very rich for a while to see if it improved performance --- it didn't. At the rate it accumulated I would probably not have to clean the tubes more than once every 8 hours of operation. The next challenge will be to understand the burner well enough to be able to set the oil to the maximum possible with no soot accumulating.
Further tests must await warm weather --- probably next April.
I expect to incorporate all of these changes into the Heisler design.