You know more about it than I do, so I'm sure you're right. It's just that I have those materials to hand, and I really fancy making something like that. Much tastier watching two pistons operating than one!

Anyway, I'll have to modify the plan before I start cutting metal. Do some arithmetic with the data you showed me and measure the speed I get from the motor when the gears get here. I think the delayed top-up is a brilliant idea, can't stop playing with it!

Ray, have you got any readings from your sensors in steam yet?
Just a thought but as your sensor is close to the top of the boiler it might be better to delay the pump starting rather than stopping, ie allow the water to drop below the sensor before pump starts, and then stop as soon as the level reaches the sensor. This would prevent it from over filling the boiler.

Geoff, sorry I missed your earlier post.
I don't know if a larger sight glass would make any difference. The problem with the sight glass seems to be when you are using a large amount of steam the water in the gauge starts boiling violently. Perhaps the bottom feed for the glass could be routed along the side of the boiler and back again to the glass making the water in the glass slightly cooler than the water in the boiler, this might prevent it boiling.
Any thoughts?
Stew

Stew, I have found surface tension in a 5mm out side diameter tube the problem with the unreliable readings. Even just filling the boiler. Laboratories would be a good supply for 1/2" glass tube, so not hard to find. Just scale appearance the only concern!!! Geoff

Hi
You are starting to discover what I found when trying to "look" through 5mm glass tube, results not reliable!
Think blowdown first........it is all in my article but do not know when it will be published.
Tim

I've heard about people using a fine copper wire in the sight glass to reduce surface tension, does this work?
I'm sure I've also read about someone adding glycol to the water but I can't remember if the outcome was good or bad.

Tag
Do you have any resistance readings for the sensor in steam and hot water, as I need some values to complete my circuit.
Did you make your sensor like the one in Malcolm Beaks article or is yours a different design?
Stew

Hi Megatron
I too have heard of putting a wire in the sight glass and by all accounts it works. I have not used this method as the opto coupler system "sees" it as water always present, the same using a fibre optic. Therefore method rejected. Not wild about putting additives in boiler feed water. Did once try a tanin based additive (as used on some preserved steam locos) but the brown colour confuses the opto.
I am afraid I have never seen Malcolm Beek's electrode design and my grade in Paddleducks is to low to let me look at his design. I use the Roy Amsbury design.
As far as water resistance is concerned it is what you make it. I use air conditioning condensate with a dash of tap water to make it reliably conducting. Steam which is pure water has theoretically infinite resistance hence the ease of detecting the presence of water using electrodes.
My electrode electronics (AC) can detect water resistance up to 150 kohms.
Hope this helps    Regards  Tim

Stew - ref. pump start delay, that's exactly what I've done. When top sensor goes dry, white led goes out and delay is triggered. After 10 seconds-ish, motor starts and runs until sensor goes wet, white led illuminates and pump stops. And so on, ad infinitium. Or at least until top up supply tank runs dry.

Ray.

Ray
great minds think alike.
Is your little tail still wagging?
Stew

Faster than ever!

Just completed calculating pump flow rates et.c. from equation you pointed at.

Conclusion: single cylinder 12mm diameter x 12mm stroke will deliver required flow rate into 60p.s.i. at 9.2 r.p.m!

Kind of proves your point I think! I've yet to measure motor speed.  I'm guessing a couple of NiMH cells will do it, if not one,
and a much smaller pump of course.

Greatly appreciate your guidance.

Ray.

I am following with interest although I know nothing about electronics. I still like to but my pennies worth in. The idea of Glycol in the boiler was to make the steam more visible out of the funnel, apparently not a good idea. As for 60psi in the boiler remember it is one square inch, so the smaller the piston bore the less force required. I am sure intelligent people like you know this, but some think 61 lb  will be needed to put water in not so. Geoff

Ray
You may want to put another sensor into the feed tank so that when the water level gets low it prevents the pump from switching on and possibly running dry.
Stew

Megatron - there's some serious telepathy going on here! The first sensor system I built was neatly packaged in a small plastic 'black box' with no room for the motor delay circuit. I've since shoe-horned the whole caboodle into a slightly larger box with a new built circuit board. Contemplating the old one I thought, I can use that for the feed tank, and use it to stop the motor when empty!

Telepathy goes both ways - so I've had to restrain myself from telling you what you're going to get for Xmas!

Have a good one, and hopefully a somewhat less wet new year.

Ray.

Ray
I hope your thinking something red, fast, made in Italy, and beginning with the letter F.
Merry Xmas
Stew

Quote from: megatron on December 23, 2012, 04:11:46 AM
Ray
I hope your thinking something red, fast, made in Italy, and beginning with the letter F.
Merry Xmas
Stew

I suppose it depends on your definition of fast, but I fail to see why anyone with any sense would really want a Fiat. 

Merry Christmas
Eddy