Hi folks,

i made some work with my electronic cylinder indication system. My steam friend Jürgen have a nice 4 inch Garret Traction Engine. Last year i showed here the video transport for live steaming.

Jürgen made some progress with the adjustment of the valve setting until he was satisfied. The engine run for him OK. But sometimes during start the engine behave in second gear like a wild horse. I had build an electronic measurement system to indicate cylinder and found some not good adjusted valve timming in my own locomotive. So I know how good such a setup is to tune the valve setting. With his Garret there is an additional problem, the valve setting changes from cold to warm,because the boiler length changes about 1.5 mm by calculation of the heat difference and length from the drive shaft to the cylinder.

My setup is based on a selfbuild rope displacement sensor with a return spring in it. It is able to measure 300 mm in total. With this i measure the piston travel.The pressure sensors for the cylinder pressure are capable to measure 12 bar. They are equipped with an integrated
electronic amplifier and are factory calibrated . It is an affordable China product. The data has been collected with an Arduino Nano and is able to work with 8 Channels. The sampling rate is 560 samples per channel per second.

It is possible to measure the towing force , the speed and the temperature in parallel.

The software is my homebrew for the arduino and the laptop.

I used this system before to optimise my 5 inch locomotives. The attention is to increase the effiency and not the speed of an engine. I like traction engines which are in standby slowly ticking over and this is a sign for a good valve setting.

My hobbies are constructing steam engines and electronic systems. So is this a perfect symbioses of both for me.

So I convinced Jürgen and add the measurement system to his engine. At the first step the displacement sensor was tricky to mount and not good aligned, but the measurement correlate to the action of the engine. The next step was to construct a better attachment of the displacement sensor. Between me and him are many Kilometers in distance so i constucted it after pictures and it was attachable with some improvisation.

The pressure sensor was adapted with tubes, this was the only possible way to make it quick and dirty.

Edited By Werner Schleidt on 27/06/2021 15:44:41

Hello Nigel,

in the video it is not good to see, in front of the pressure sensor is a copper tube with one turn for condensing the steam as it is normally made for pressure gauges.

Hello Noel,

i do not know the Dobbie-Mcinnes steam indicator. In principle i measure the displacement by a multi turn potentiometer with a return spring. At the moment i have sensors for 300 and 250 mm displacement. So the piston travel is measured linear. The pressure sensors are connected to the draincock pipe at each end of the cylinder. This is equal to any kind of Indicators I saw in old books.

In two or three weeks we have our next steam meeting and so we tune Jürgens 4 inch Garret again. We will see how good we get the engine. I make a documentation again and I will try to show more details. But for me it is a one man show. With handling first my own engine , making a general video of us and then at the end of the session make the measurements and documentation. And it is working fine , but it is not a turn knob equipment.

Werner

Hello Noel,

i know the Maihak Indicator, but they are all similar. With my displacement sensor you see in the time diagram each stroke very clear and the pressure at each millimeter of piston travel.

My Software is quasi a digital storage oszilloskop software with the possibility to store in a file and show it in a

XY chart or here is it the indicator diagram . I can measure 8 Sensors in principle two independant compound cylinders with two setups 2 times diplacement and four pressures.

Werner

Here is the diagram with the principal indicator diagrams.

It is from the Handbook on steam engines from Haeder and Powles 1902.

Thanks to Vic who sponsored me with informations and web links!

This is taken from the side 383

The left curve number four with late admission fits to the kind of the measured curves and number two throttlling. For the power of the engine we had during the measurement to less load . Normally the engine have to pull a wagon with some adults as load.

Werner

Hello Vic,

a few words to my fire king. It is roughly planned to make indicator measurements too. But this have not so a high priority.

The steam engine had a remarkable improvement of the boiler and fire performance with the added steel stripes in the fire tube which is normally for the superheater pipe. Many thanks to Johannes, known as Yorkshire Man, he gave me the hint in a german forum. So i gave this idea a go and test it at my fire king boiler.

This stripes hang in the middle wide tube of the boiler. This stripes force the exhaust around this stripes and add some resistance for slowing down the gas velocity. So the exhaust gas have more time to add heat to the boiler.

The change was remarkable. I could drive after this with continous blowing safety valves and the fire burns much better. There was only like black sand in the smoke chamber. Before there were much more bigger unburned coal parts and sparks. I changed then the exhaust nozzle to a wider bore. This gave the steam engine less back pressure and so the RPM and power increased. The fire burns a litlle bit worster ,but much better then before I made all this changes. If i drive continously and do not forgot to add coal regulary , I can drive permanent with a pressure short for blowing of. I can control the pressure by adding water or not.

Here is a photo with the setup and the changed exhaust nozzle after 11 Km of driving.

And here is the clinker after this ride

This was a big improvement.

I made measurements with a thermocouple to measure the exhaust temperature and it was clear to see that the fire burns much better.

More information in the thread Merryweather Fire King self propelled

Werner

Hello all,

we made another meeting with our steam friends. Jürgens Garret Traction engine have now a correct valve setting , based by the investigation of the electronic cylinder indication. On the end of the video there are two sequences were the engine is set to a very slow rpm . Now the engine have a fine driving behaiour and the coal and water consumption is remarkabel less than before.

Have fun with the video.

Werner

Hello Nigel,

I know that for internal combustion engines piezo electric pressure transducers were used. One special brand is Kistler from Swiss, they have a good knowledge and reputation. But there parts are extremly expensiv.

For this job the china made transducer are in the range of 20 € and this is no problem and they are precise enough.

My homebrew software is able to measure the rpm of the engine and the average pressure during running. And with this i am able to calculate the engine power. For valve setup investigations this is not useful, because normally we run the engine not under full power there is normally a throttle valve in front of the cylinder. The Garret of Jürgen is extremly powerfull there is no easy way to brake the engine to get a full power diagram.

And with my small 5 inch locomotives it is the same.I had to use a brake locomotive it is the same as they do it in full size. I tried to make a test on track with cylinder indicated power in comparison to Power at the dynamometer and speed of the wagon. This gave partly some good and some strange results and i found that our track is not in horizontal level. I have to use my electric locomotive as a brake loco to charge the battery.

But then came winter and corona and so all investigations were on hold. I have more ideas then capacity to do all.

Electronic cylinder indication is a good tool for fine tunnig the valve setting and this is the main function i use. And it is much better then the try and error method i use before. And i am very astonished with which small changes a very different driving behaviour is possible.

Werner

Part 2

The displacement sensor or the piston travel sensor is more tricky. I want to have a sensor who is on small and bigger engines possible to install. I had an incremental angle sensor this is very accurate but it have to be attached to the axle or flywheel and that is not so easy without changes at the model or object. I get by chance a very fine LVDT displacement sensors with a carrier amplifier and inbuilt electronic. To meassure 100 mm the sensor is about 300 mm long. This is difficult to mount. So i came to the results that the sensor mechanism with a rope like in the old indicators is very favourable. So i thought about about how i can build a sensor. In my former job i know rope displacement sensors based on a rope a return spring mechanism and a rope drum and a potentiometer. This parts are very expensiv , the range is from 500 to 1000 €

So i construct my own. The base is a multiturn wire potentiometer with 5 Kohm , a drum which is coupled with the potentiometer axis and a return spring i got from a identicard jo jo. This were my parts which play together to operate the rope sensor. My modelplane colleague Herbert sponsored me with thin multiwire control line rope.

It was very tricky to bring all parts together and after the first one i made two others all in a range of max 300 mm. I tested them in comparison to my digital gauge at the milling machine. The measurements were very repeatable and with a good accuracy. I added a small amplifier with a filter for cutting noise and with a level shifter for easy zero shift adjustment. The span was precalibrated at the amplifier and a fine calibration can be made by software. All sensors have a unique calibration file, but the rope sensor are very similar.

To give you an idea from my sensor

The spring is in the frontside of the drum . In the front cover of the housing there is a screw which is the spanner for the spring. The tricky part is adding the rope winding by winding in the right direction and spanning the clock spring and setting the potentiometer at the correct position. This is a four hand job, but with several try's it worked good. The amplifier ist then attached to the potentiometer and then it was added some heatshrink tube. Then the parameter and calibration was measured and marked at the sensor.

In the next picture it is adapted to my loco for measurement.

The pressure sensor is connected to the cylinder cover. The rope sensor is mounted with some improvisation with clamps and wooden bars at the front. The rope is connected to the crosshead by a chain and a adapting screw. The white PA part allows clamping of the sensor and some adjustment.

part 3

Werner

Edited By Werner Schleidt on 15/09/2021 18:03:05