Print

Please login or register.
1 Hour 1 Day 1 Week 1 Month Forever
Login with username, password and session length.

[flashtwo]

Hi Mayhemers,

Last June at the Sumner Ponds Model Show, my Edwardian Steam Launch “Vital Byte 10” performed very well, but I was “stung” somewhat by the comment that the Stuart D10 engine sounded like a diesel making rather loud clacking sounds.

I thought, at first, that the noise was caused by piston slap, but on closer examination found that there was a lot of travel between the piston and the worn-out big-ends, approximately 1.3mm. The D10 has been in use for the last 7 years powering the 5 inch prop.

I decided to replace the con-rods and cross heads, since the big and small ends were worn out and so I forked out some readies for new pressings from Stuarts (a much quicker service now there are on the mainland!) and machined them up.

Several years ago I made a “vibration” sensor out of an old Christmas card i.e. the bit that plays “jingle bells” – the piezo electric disk. Not only do they make a noise, but they can also convert a noise into an electric signal.

Before and after replacing the worn out con-rods and cross-heads, I made some “vibration” recordings to visualise what was making the noise.
The prop shaft speed pick-up was used as a reference pulse and enabled me to determine which con-rod was causing the most trouble.

The first recording (VB10 vib 18) shows the shaft pulse (at 568 RPM) on the top trace (red) and the “vibration” as the lower (blue) trace.  Knowing the relative positions of the reference pulse and the cranks’ top and bottom dead centres, it was possible to determine that one con-rod was worn out more than the other, but both were quite bad.

The actual clack noise is caused by the steam valve opening and the pressure suddenly taking up the slack in the bearings.

The second recording (VB10 vib 25), shows the shaft pulse (at 570 RPM) and the blue lower trace showing the marked improvement with the new components.
Obviously, you don’t need such sophistication to detect the improvement – just the new sound of the D10 is enough for that.

The last two photos show the “Christmas Card” vibration sensor mounted on a magnet with a bit of ebonite in between acting as thermal insulation.

How does the old Beach Boys song go……..”I'm pickin' up good vibrations  She's giving me excitations” (that’s enough of that!)

Vital Byte 10 will be at Herne Bay, Kent on the 24th August – see you there.

Ian

[rhavrane]

Bonjour flashtwo,


As told on one of your other message, I have several D10, bought in second hand. I also noticed they could be noisy when used for a long time.


I also noticed that there is a sound difference between a D10 running on a table or in a hull.


This D10 in my Côte d'Emeraude tug  is many years old but run only several hours, it is smooth unlike my Reeves Warrior which has been used a lot and which leaks and vibrates a lot.


In all the cases, I woulld never say that they sound like a Diesel  [size=78%] [/size]
[/size]
[/size]PS : I would be happy to see your launch, may I have a link on a video ?[size=78%]

[TurboTyne]

Hi Ian
That vibration sensor is a very ingenious device. How do you use the output of the piezo device - does it go to an amplifier of some sort?

Could this set up be used as the basis for dynamic balancing of, say, a turbine disc? I am thinking that if you know the positions of the shaft rotation sensor relative to the disc, you could estimate the location of the point where mass should be added or removed, although it would probably be too much to be able to predict how much alteration to make. This could be more sensitive than simply using horizontal knife edges and letting gravity rotate the disc to a low point.

Regards  Mike

[flashtwo]

Hi Mike,

The "vibration head" and reference pulse signals just plug into an oscilloscope/laptop interface module - in my case a PICOScope model 2205.

The 'scope enables me to take the snapshots of the noise as you can see above.

As regards dynamic balancing, I don't know if the piezo would give a sensible signal down at say 50Hz, if you were spinning at 3000RPM, to make sense of any out of balance forces. If you up at 30 000RPM then a useful signal would most likely be present. Considering how cheap the Christmas card "head" is, it will worth a try if you've got access to a 'scope.

I suppose you could experiment with a plain balanced disk and then add some known out of balance mass on the disk and see what difference it makes.

I'm still analysing my results and I can see that the non-drive end main bearing on the bed of the engine is causing noise as is confirmed by moving the shaft slightly up and down. I shall be machining some new blanks to replace the three crank bearings on the D10.

Ian

[rhavrane]

Bonjour,


My club members equilibrate manually the propellers of their offshore because their run at about 40 000 RPM and they use a dedicated magnetic tool to avoid any friction.


I guess they would be interested as flash steam users could be (we are in a steam topic) and, in France, unfortunatly, I do not know any flash steam user.


When I see THIS video, I fully undestand your topic !

[flashtwo]

Hi Rhavrane,

My steam launch is much more sedate than the high speed hydroplanes.

They use the flash boiler where the water "explodes" into steam when hitting the white hot boiler tubes and have very high steam temperatures that would destroy the Stuart D10 engine. My monotube boiler produces steam at saturation temperature of below 140degC normally, can run for more than an hour on one gas cylinder and travels along at a about 2 to 3 mph ( 3 to 5 kph) which is a scale speed of about 10mph.

I have found a couple of more photographs showing the vibration head fitted to the engine, with its magnetic base, and also the "Picoscope" oscilloscope connected to the laptop.

Ian

[rhavrane]

Bonjour Ian,


An autonomy of more than an hour is great especially if, like me, you like navigating and leave your mind doing the same with your ship.

140°C means about +/- 3 bars (45 psi) doesn't it ?

I confess that I like steam because it is alive, visible, and I do not control electronic devices otherwise.

I do not look for speed, but, for the falous internationl speed race "Anton trophy", my fastest boat reaches 6,93 km/h but is always passed by a "twin" equipped with a better performance boiler (Yarrow, I just have an horizontal one) HERE .   

[flashtwo]

Hi Rhavrane,

Yes, the D10 engine starts turning at approximately 0.35 bars at 140RPM and at 2 bars it is turning at about 550 RPM,  with the steam temperature going from about 112 to 135degC.

The gas consumption is about 3.5 g/min including the start from cold. A 230g gas cylinder gives me about 60 min running and the 460g cylinder theoretically would give me 120 min running, but I only run for about 45 min which is when I get bored. I also have to consider that the engine needs more lubrication oil to be added after a long run.

The steam boat race looks like a lot of fun - I wish there were more model steam boats in the United Kingdom (we won't be using that name much longer!).

Ian.

[ooyah/2]

I wish there were more model steam boats in the United Kingdom (we won't be using that name much longer!).

Ian,
I wouldn't be too sure about that.

George.

[rhavrane]

Bonjour Ian,


I would agree with George, I think there are much more steam passionates in Great Britain than in France.


Beside this, Allow me a remark on your D10. To my opinion, its exhaust pipe is nice looking but makes the machine lose energy because each cylinder thwart the operation of the other with its outlet pressure. I followed the recommendations of Stuart


After noticing weakness on his machine with an installation like yours, a friend applied the same recommendations and noticed a real progress.


And about lubrication, I have added my own solution 

[flashtwo]

That's a very diplomatic ambiguous take on my quoted statement George!

(Sorry Rhavrane - internal UK politics being talked about. George may not be referring to the number of model steam boats in Great Britain/United Kingdom).

That's a very large displacement lubricator - how much running  time does it last?

Do Stuart recommend that each cylinder has its own independant exhaust?

Ian

[ooyah/2]

Rhavrane,

Think 18th Sept 2014, referendum !!!!!

George.

[rhavrane]

Bonjour,


Thanks to the net, I know which referendum will be organized and sorry to digress in a steam topic.

With its coupled pump, its large oiler and  its large gas tank (below), I can navigate 1,5 hour with Jan, but I stop generally after an hour.


About the D10 exhaust, the one I have on all my D10 (and all my steam machines in fact) is the one presented in Stuart catalog.

As previously said, We have noticed a great difference with a friend by replacing "your" mounting by "my standard one".
Tri JMC.
Bi JMC

Other example, I had only one oil separator for my twin Anton Quartz Fulgerul and I could not use them at full speed, I installed two oil separators and now everything is back normal.

[boneash]

Do you believe that the swept pipe with tee connections, of Stuarts, is more efficient than Flashtwo's balanced length exhaust ??

I would have thought that the pulse of steam hitting the tee would create a back pressure wave towards the other cylinder exhaust valve.

But the balanced length pipes would be less likely to cause back pressure waves.

Have you carried out any comparisons ?

I am impressed with the quality of the engines you have shown us!!

[rhavrane]

Bonjour,


Thanks to the Net, I know what will happen in UK/Scotland on September 18th, and it is not a topic evoked on our TV channels.

About the piping, I confirm, boneash, even if we have not scientifically measured the difference before/after on my friend steam machine, we have seen a real difference of speed.

I have also personally lived the same problem on my Fulgerul which did not want to go full ahead. She had a single oil separator ==> I installed two separate ones, and now she runs like a torpedo, even if she weighs 18 kilos and is powered by only 2 x 2cc Anton Quartz.

And if you like the JMC production :

JMC triple expansion

JMC compound
JMC bi 2 cc with coupled water pump
Pictures of my own collection

[Jerry C]

I used to take exhaust steam from my separator to the flue/funnel with 5/32" I/d pipe but on a rebuild had problems with draft causing flame to lift off burner and occasional extinguish. Replaced with external exhaust but had no 5/32" pipe so used k&s 1/8" bore brass tube and a short length of plastic pipe. The result was a considerable increase in power.
Jerry.