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Modify Aster return water valve needle?

5659 Views 36 Replies 11 Participants Last post by  Charles
Has anyone done this, and can give advice?

Aster has given all valve needles a very steep angle (like 80deg inclosed?) on my P8 / BR38. This is most likely to make RC conversion convinient. However, I do not intend to operate the return water valve with RC.

As it is now, the actual operating range of the valve handle is something like 20 degrees. That movement alone makes the valve go from closed / feed all, to not feeding any water.

Preferrably, I would like to extend the operating angle to 180 or 360 degrees, to make setting easier.

The valve seat seems to be 2mm, so i'm thinking of making the needlr acone from 1,8mm to 2,3mm. Unfortunately, I have not done any trig in 20 years, so i'm not sure how to calculate the angle. I may just set it up in the lathe, turn it down to 2,3mm, and the give it a slight taper with a file.

In case I screw up totally, does anyone know what thread the valve needle uses? (In case I need to make a completely new one /DesktopModules/NTForums/themes/mls/emoticons/whistling.gif
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Most aster needle valves use a 60* taper on the point, which as you have found out, is nothing more than on-off. The real issue does not lie in the taper angle, but rather the length of the taper. If you extend the taper length by a mil or two, then you will get much finer control. 1-2mm of an extension is good, but anything more than that and you will have to machine a new valve seat as the needle will not seal off. You should be just fine in

If you do screw it up, I believe that the thread (judging from the picture you posted) is 5mm x 0.5, a very common thread on aster engines. Not having owned/operated a P8, I can't give you a definite on that, but it sure looks like a fine pitch 5mm thread from experience.
If you fear damaging the original stem and having to make a new one, why not start by making a new one to your desired specs and leave the original alone (then the Aster engine can be returned to an "as delivered" state if case you wish to sell it to a collector).
Thanks Ryan,

Since posting this morning, I sort of realised I left out the length of taper... And of course you are making the point ** :D ** much clearer, that the lengt is the thing that gives "rotations". I just thought that since the seat is 2mm, keeping the length of taper - let's say 3,5mm?? - around the 2mm diameter, would give the most regulatory effect. BUT - this means a very sharp pointed angle, something like 15*, if my very rusty trig calculations were right. And I don't know that that is right at all.

If I just extend / "lean" / the taper from the point, to 2mm closer to the handle, is that taper something you know is in the right magnitude of taper?? (What angle would that be... now that much trig I definately do not remember ;D

With my bad spare vernier, thread diameter is 3,8mm, so some kind of M4 would be my guess. To me, just looking at it, it looks even finer than standard FINE M4.
Yes Charles,

The idea has occured to me :) Only, because I don't think it's a standard fine M4 thread, I do not own the threading die. And bying one, costs about USD 30, so buing a new needle from Aster is simpler if things go wrong.
Changing the taper on the part you have may make it useless.

Consider; if the seat in the body of the valve were to go away, how much farther could you turn the valve steam into it? Would the handle end bottom out on the body in just one more turn?  Or, think of it this way, if you grind off the end of the stem by, say, 1mm, would the stem be able to touch the seat before the other end bottomed out.

If you make the point of the stem sharper (more taper to the end) it could be that you could not rotate the stem far enough into the body to still close off the opening.

I assume you are talking about the "bypass" valve that you open to allow water from the output of the axle pump to be returned to the tender, and close to cause the axle pump to force water into the boiler.

I know people talk about finding some magic setting where the pump is feeding exactly the same amount of water into the boiler as is being boiled off/out of the boiler.  Actually, this is a very hard place to find, because the amount of water used varies constantly.  The fire is never constant, so the amount of steam being generated varies.  As the throttle is adjusted for speed and grades the amount of steam used varies.  If the blower is open some of the time or if the safeties blow off some steam, that amount of water must be accounted for.  If you can control the valve gear cutoff then you can change the amount of steam being used.  All of this means there can be no one setting for the bypass valve, it has to be adjusted periodically.

From my experience I am better off watching the sight glass and fully closing or opening the bypass valve as needed to refill the boiler when it is necesary.  On my 150-ft pike, I only have to open or close the bypass valve on my Mikes once every dozen or so circuits.  If I pay attention to the valve gear cutoff, I use only 2 tenders full of water on 1 fueling; if I don't pay good attention to it, then I need at least 3 tenders full.  If I get parked for some reason (derailment or yapping with visitors) I have to open the blower so I may have to use the hand pump in the tender to replenish water in the boiler.

With a deft touch I can open or close the bypass while the loco is passing me, without stopping.  If I see, on one pass, that the sight glass shows that boiler water is getting low, I can close the valve on the next pass, run for 2 or 3 passes and then open it again.  On the next pass I can open the tender hatch to see if I need to add water there; if so, I stop on the next pass to do so (I am not deft enough to pour water into the tender on the fly!  Heck, I ain't deft enough to do it "neatly" while it is parked!)

I recognized the engineering (both from the design "engineer" viewpoint and the driver "Engineer's" viewpoint!) desire to find the 'sweet spot' for the bypass valve, but I think it is too fugitive to persue.
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In many ways you are right. Even with a needle-valve that allows a reasonable chance of actually setting a "sweet spot" , amount of water factualluy needed to keep water level constant, will vary witth train load and speed. (and actually firing and blower, and maybee something else, that I would not, however, normally ty to accomodate) If however, there is no chance, or point, to finding the right amount beeing fed by the axle pump, what sport is left to the driverstask of setting the valve whatsoever? As it is now, I mainly regulate the waterlevel with the tender manual pump. That however, leaves me at the same operating "level" as Maerklin / Regner locomotives, where I add water with a flower-sprinkler. The axle pump becomes a redundant feature. And more impractical than a servo operated feed-water pump. So in the end, I find that an axle pump, has to be accompanied by a valve that allows reasonable chance of finding a setting, or it will actually be quite useless / pointless.

I have measured the space beondt the valve-seat, and it is actually in the range of 7-10mm. However Charles, thank you for thinking about it!!!! With a longer needle going beond the seat opening, possibly reaching the "bottom" before even closing, would be a catastrophy! The equavillanmt of a water tap, never beeing possible to close more than "half".

However, the more I actually consider the possible endeavours of achieving a suitable modification of the needle valve, let's say giving 180* or 270* effective operating angle, the more I become convinced this is actually a manufacturers job. It isn't fair to leave this kind of possibly very elaborate design experimentation to a kit-assembler. Especially since aparantly the same valve-needle angle is used over and over again, in various kit designs.

The needle point delivered leaves me the impression of actually beeing "un-designed". An completely unbalanced in-between of needle angle suitable for Radio Control, and manual control, leaving no-one even remotely happy.
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With a 1:1 steam locomotive the Engineer and Fireman do not seek to set the injectors and/or pumps to feed just the correct amount of water to account for what is used.  They run an injector/pump as needed,  The sight glass is not a single point measurement.  It displays a range of water.  Too much and you have no steam space and will probably have "carryover" (water in the dry-pipe and cylinders... a bad thing).  Too little and you risk a blown crownsheet (a catastrophy).  BUT, there is a wide range of water level between those two points and there is little difference in operating characteristics over that range (although I find I get better runs when I am on the "low" side... the engine seems to have more "pep", so I narrow my "operating range" to try to keep the water level in the lower half of the glass, rather than allowing it to be anywhere within the whole glass).

With our miniature boilers, we only need to do what our 1:1 brothers do.  Turn on the system (close the bypass) to add water when it gets low and shut it off (open the bypass) when it is back into the "range".  If you want to keep it closer to just one level, turn it on more often and shut it off before the level goes above the level you want.  That means MORE "hands-on" operating and a need to pay more attention to things, but with Live Steam, this is what it is all about.  If we just want to see the wheels go round and the rods flashing in the sunlight, an electric motor hidden in a boiler "shell" will produce that illusion.  But that is not a Steam Locomotive.  I must be the Engineer of my locomotive when I am running it and that means I must pay attention to water level just as much as I pay attention to the speed as I approach a curve!
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Let me quote the Aster running instructions in the end of the manual, under the subject "BY-PASS VALVE"; "You wiil learn by experience the proper setting which will maintain the volume of water pumped into the boiler consistent with steam consumption."

I think it is indisputable that Aster really do not intend, or describe, an "on-off" operational mode of the by-pass valve. However, as Ryan points out above, the needle shape delivered by Aster, really only allows for on-off operation, since a movement of only 1/12 or so, of a whole turn of the handle, constitutes the entire operating range between on and off.

The more I think about this, the more pissed I am getting. It's like supplying a TV-remote, that only has a range of 1m. It's poor engineering to the point of uselessness.

The fact that Aster aparently has used, and is using, this blunt needle shape, for years, and for all models and controls, actually severely  compounds the issue. Having almost nothing but on-off control by the blower is equally bad. In the case of the main regulator, speed control can alternatively be achieved by varying the degree of cut-off / filling with the reverser setting.

The worst part is, that it is not easily modified by the 90% of buyers, that build kits.
1) You need a lathe with a collet (a chuck probably won't do), and a travelling steady. My collets lack a through-put bore, so I cannot machine the blower needle. Also, I don't have a travelling steady
2) Even if you have the machinery, experimentation is actually needed to determine the optimum needle angle. This is clearly the job of the manufacturer / designer.

Not to mention, that this actually puts the Aster kits in a different category, where you need sofisticated machines and skills.

Also, because the needle valves are very sideways "rocky", lacking axial support, at least on my P8 / BR38, determining how much I actually moved a handle (and needle) clockwise, or if the handle just "rocked", is also an annoing difficulty. This gives the controls a rather cheapish and crappy operating feeling. I am surprised Aster realeses this "feel". (Car manufacturers spend a lot of time on designing the sound and feel of car doors!)

I'm angry. I'm going down to my workshop, to try finding out the needle thread, so I can possibly make sets of new needles, with varying point angles.


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I actually think Aster ought to offer a re-call program, the way car makers sometimes do, where Aster offers to re-tip any sent in control needles, with proper needle taper for reasonable operation.

I wonder if the difficulties of running Aster engines slowly, and possible "finicky operating characteristics", that some people complain about Asters, may not all be caused by the blunt needle valves employed.
Trying to measure the blower seat, using several consecutive diameter fine rods, it seems the blower valve seat might be a cone, with the final inlet hole beeing only in between 0,5 and 0,8mm in diameter. Rods with diameter 0,8 ; 2,0 ; 2,5 and 3,0 mm give the same depth measurement, as far as I can judge. This is the basis of my guess. The actual blower needle tip, has some slight circular dention around 1,5-2mm circumference. However, this may only be the result of an uneven seat surface.

This means, one would probably either;
1) Fit a sewing needle point extension to the blower regulating point, or
2) Fit a new flat seat with a circular hole as seat rim, and then shorten and reshape the blower needle tip in a suitable manner.

Otherwise, action will remain almost on / off like.
I have not personally looked at valve stems from the other live steam mfgs, but I remember some articles in SitG about the valve stem for a butane valve being of similar blunt construction (the photos I remember looked about the same). The article described tapering the stem to provide a finer control of the flow of the gas for burner control.  There was also talk of improving the fit of the threads to eliminate the "touchyness" caused by the loose fit (the mere act of letting go of the stem can effect the intensity of the fire).

I think this design is extremely common (across many manufacturers) because of the expense and complexity of making it a finer control, when that fine control is not necessarily needed.  Desireable by some, yes, but not actually required.  Yes, I know that Aster's manual suggests that the bypass valve is to be set to optimum place, but I know that is nearly impossible to achieve for any period of time due to the varities of the fire/boiler/engine system.

A "recall"... no, not anymore so than that Ford should recall the T-bird, because someone thinks the Corvette has a prettier color available.

If your anger causes you to do a redesign, then use that anger constructively and let us all know the results. I don't see how you could get a traveling rest into the same area as the bit and the part to be turned, since the part is so small in the first place.  Personally, I think I would chuck the stem in the lathe and use a file to produce some additional taper to the end of the stem, but then I'd have to then use some fine sandpaper to polish the tapered part so as to actually produce a good seal when the valve is fully closed (for maximum pumping into the boiler).

I think you will find that the seat of the valve is simply a standard drawn copper pipe soldered into a hole drilled with a standard pointed drill bit and there will be significant variation from one valve to the next, based on the sharpness of the drill, the uniformity of the cut end and the variation in the inner diameter of drawn copper miniature pipe, and the amount of solder deposited in the general area.  The ring scar on the end of the stem is just where the stem has rotated in the inner diameter of the drawn copper pipe as it seats.

Could the valve be made to operate much more precisely?  Probably,
Could we afford such precision?  I could not, I am sure.
Nor is it necessary.  If it could be adjusted to allow a precise amount of water through, you would need to constantly adjust it to fit the needs of the moment.  You would very quickly adopt the ON/OFF operation and forget the precision in favor of relaxing and enjoying this and the other aspects of running a Live Steam Locomotive.

I admit that I have been tempted to alter the taper of the throttle valve stem to see if it could improve slow speed operation.  I have not seen any need to adjust the blower valve to better its operating parameters as I tend to use it as a gross adjustment of the fire in just a few steps between OFF (and leaking a bit) and Full ON when the engine is not exhausting steam to maintain the fire.
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I struggle to see the problems some of you guys are having, with all my 3 Asters I can maintain a level in the boiler every time with the production needle valve.
Maybe you need to learn how to drive you locos that's where the pleasure is.

Posted By tony23 on 03/15/2008 2:08 PM
I struggle to see the problems some of you guys are having, with all my 3 Asters I can maintain a level in the boiler every time with the production needle valve.
Maybe you need to learn how to drive you locos that's where the pleasure is.


Don't struggle too hard... it is easier just to gnaw through the straps./DesktopModules/NTForums/themes/mls/emoticons/hehe.gif
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Dave Hottmann's fix for the loose fit of Accucraft's throttle valve was to add a spring on the throttle shaft. The spring tension kept the valve setting which allowed more control of the valve. He reported it worked well.
Remember those cars you drive at a fair-ground? The accellerator is actually on-off. At 1 Dollar a drive, I don't care. But if someone suppodedly sells me a Ferrari / Porsche / Mercedes with the same amount of accellerator control, I will get pissed, the way I am now. No amount of driving skill will actually quite compensate for such bad mechanical controls.

Regner supplies two different steam conrols. One for manual operation, and an optional intended for RC, that only needs like 40 degrees to go from closed to all opened.

Problem is, it's almost impossible to change the blower valve at all. I'm, stuck with the shitty stuff originally supplied. I'm not happy, because I expected something more. Furthermore, Aster actually perpetuates these these somewhat higher level expectuations, quite in accordance with the price tag that comes along an Aster engine.

Adding an extra groove with an O-ring or teflon packing, would probably eliminate the "rocky" movement of controls. However, no one would feel happy, having to add their own band-aid to controls of a Porsche, to give exact feel to control, even if possible.
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I'm baffled by all this "anger". I have over 20 Aster locomotives going from the original Schools though to a pair of 9Fs. They are superb pieces of engineering which get better with every generation and I've never felt the need to re-taper needle valves or do any other re-engineering. With the exception of Lion - which I never got to grips with - I run all of them whenever I can. Just cracking open the by-pass valve for the axle pump usually works well but you still need to monitor water levels in the boiler as water usage is never constant. Similarly, we are all kidding ourselves if we think that we need endless control of the blower - when I put radio control onto my Berkshire, I used just two switched positions - full on for raising steam and part on for keeping the fire active when the engine is stationary or under very heavy load. 

(Over the last few months, I've posted some videos to youtube (search - robertyoungjohns), primarily for my nephew in Finland, which show some of them in action.)

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Pauli, you need to chill out.  I have said here many times that Asters are not perfect.............but, what brand is??  (Well, other then  Regner :))  There are hundreds of Asters owned by MLS members and you are the only one that keeps having problem after problem with them.  As far as the by pass/water pump, the P8 that runs at my track  has no issues. On my Aster engines, I look at the water glass every few laps around my track as the engine goes by and turn the by pass on or off.  Whats the big deal??  I could not tell you the cut of the angle on the pin (nor would I know how to measure it) because I realize that these are toy trains, nothing more and nothing less.  Yes they are expensive, but go out and find a machinist, give him plans that are "engineered" to your standards and have him make you a one off P8.  You will find out in a hurry what a deal a Aster P8 is, and the Aster would probably still give you less problems.  :)
Aster has provided a visual feedback loop, to enable setting of the bypass valve.. if you watch the retrun pipe in the tender , with the bypass open a strong pulsing flow is visisble, turn the valve down until the flow is adribble , just leaving the pipe with no force..if you now set the bypass valve so the flow is about half way beteen these extremes, you are putting some water into the boiler, just try changes in the valve setting until you find where the boiler water level is held about ahalf glass.memorise the look of the water rom the return pipe, into the tender and you will be able reproduce this easily..

The thread on the valve is 4mm by 0.5 mm pitch.
When running Aster engines two things can be done; 1) blower-open to the point of full draft tthrough the range of  barely open as the draft builds and 2) as per David the by pass can be set from open to a dribble.  The control factors are available and with an adequate range from closed to full open.
What I do not understand Pauli, is the need to jump to conclusions with relative little experience with this particular engine.  As with the one other post you made prior,with a tone of dissatisfaction and anger, that later became a voice of success and pleasure.  Therefore, maybe a bit more patience and running time might offer all of us an overivew of one's total experience.
Many of us face problems with our engines from wicks  to loud gas burners, etc but most try to offer a perspective of  advice seeking or offer advice from on the results of the experience.
Our experience with the GS4 from another brand resulted in a lot of time, money and energy to get it correct.  We still have the engine and really enjoy the end results.  Could the company had done the workmanship that we invested in the engine, yes.  Did we "bad mouth" the company, no.  To make it a win-win we worked with the company to advise them of the upgrades.  We decided it was better to keep the company informed  by offering a better way to develop the product than to halt any future productions due to bad PR to that model.
Finally, your auto example of a product and consumer relationship should help with your Aster perspective.  The auto as delivered meets certain design specifications.  Yet, many owners customized their rides (as we have done with several of our cars) regards performance or style.  Could the company have done this off the producton line, yes.  Does the car make it from point a to b- yes.  Are there lemons, yes.  So, you have a base line locomotive that runs (as per you post), either enjoy it or make it meet your specfications rather than making rants.
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