'WIDE A WAKE' a steam launch tale

[Maryak]

P.S.

What has happened to your steel boiler build ?
Have you had it pressure tested yet ?

George,

Alas, it like all my hobby work is on the back burner and has been since April. My health, our winter and Galina's family problems have conspired to turn me into an armchair modeler. I am hoping for the spring to bring a spring back to my step. Thank God for CAD so I have some engineering challenge each day and keep the brain churning over.

Best Regards
Bob

[Ramon Wilson]

My health, our winter and Galina's family problems have conspired to turn me into an armchair modeler.

Bob - you have my sympathies - to have my workshop time curtailed in such a way is something that would affect me greatly. May your health soon return, your problems resolve and you get a good warm spring - 'hang on in there buddy'

Jim - Well, what can I say? To receive a favourable comment from someone of such obvious talent is a compliment indeed - thank you.

I too have looked at all your postings and can tell you I truly admire your skill, your knowledge and your ability to produce such superb examples of I/C technology. Though I have not responded save for my initial comment I assure you I have read all your responses with a very high degree of respect for your dedication to such a demanding level.
Though I used the word 'enviable' in my post, envy, at any level, is really not one of my characteristics for I am very content with my lot. However to see what you have achieved does bring a high degree of  'I would have loved to have been able to do that' 

It's days long gone now but years ago I was involved with high speed R/C boats with a keen interest in the Naviga Triangle event - I had one of the first OPS 60's over here, an awesome motor at the time - but personal circumstances at the time dictated that interest's short life. I had to move on and that was all left behind. I still have a couple of OPS 60's and a new 90 (acquired much later) but it's been a long time since the desire to do anything with them. So whilst I can't pretend to have a deep knowledge of your work I do have an understanding of your aims and a fair appreciation of the engineering skills at your disposal  . Thank you again.

Nothing to report today - Sue's on holiday so it was a long beach walk and gardening - I might get a day off tomorrow though

Regards - Ramon

[K.B.C]

P.S.

What has happened to your steel boiler build ?
Have you had it pressure tested yet ?

George,

Alas, it like all my hobby work is on the back burner and has been since April. My health, our winter and Galina's family problems have conspired to turn me into an armchair modeler. I am hoping for the spring to bring a spring back to my step. Thank God for CAD so I have some engineering challenge each day and keep the brain churning over.

Best Regards
Bob

Bob,
Sorry to hear that you are not quite well and at present an armchair modeler.
I hope that when your summer arrives you will be much better and get on with the boiler.

In the U.K. we are having a great spell of weather , even here in Glasgow the temps are up to 27 deg C which is warm for us and looking good for the games.
This hot weather makes it far to warm for the workshop so I can indulge in my main passion "cycling "
I started when I was 7 years old and at 75 I still manage 2 -3 rides of 30 mls per week, so today with temps at a dull 23 C it's over the hills and far away for me.

Here is a pic of my trusty stead.

Keep well.
George.

[SandCam]

Hi Guy’s,

Bob,

Sorry to hear you suffering some health issues and family problems, never good in isolation, let alone both together.
I hope the coming warmer spring weather helps you in recovering your health and that the family problems can also be resolved soon.
Hang in there, both of you.

BTW…Too much CAD is bad for your eyesight… you just can’t win.

George,

I am puzzled by your use of the term ‘Blowback’ in relation to high gas velocity.
Can you explain what you are suggesting?

From a burner point of view this term usually relates to the gas/air mix being delivered at a lower velocity than the flame front… hence the flame can burn (blow) back into the mixer chamber, or even right back to the gas jet… not a good idea.

The gas/air velocity being too low usually causes this.


Ramon,

Great to see how far you have got with this build.
I have been keeping an eye on the posts; however, I have deliberately stayed in the background, so to speak, to allow the other guy’s to make suggestions and comments. All of which have been very positive.

1st thing… I agree with George… fit a copper pipe for your gas feed… certainly don’t want to see a fireball with you getting badly hurts.

OK then… It would seem that you have now hit a brick wall with the burner… well; I can assure you that you are not far from it being a good one.

Looking at the last pictures tells me that you have reached the limit of gas air mix and that there is too high a gas content and no way of optimising things.

What to do?   Well: you can turn down the gas valve to reduce the gas content, however this will also reduce the gas velocity, which, in turn, will reduce the amount of air being drawn in via the Venturi holes… so that won’t work very well.

Fit a one size smaller jet… this will reduce the amount of gas but will also increase the gas velocity, which, in turn, will increase the amount of air drawn in through the Venturi holes… leading to a weak mixture… not quite what you need, however, you now have the option to move the gas jet holder closer to the Venturi holes and to partially close off the Venturi holes using the sleeve… a combination of which will allow you to optimise the mixture.
It’s all a bit of a balancing act just like the Venturi /spray bar arrangement on IC engines.
You should aim for a flame, which is a white/pale blue in the centre cone surrounded by a distinct darker blue outer cone… Butane/Propane burns with a slight yellow at the extreme tip.

The slight yellow tinge you can see in the flame some distance from the burner is mostly caused by burning dust and dirt particles in the air.

Your 0.35mm jet is a number 16.

The next size down is a number 12 at 0.3mm. (This is the size I recommend)

Next down is a number 8 at 0.25mm.

Next down is a number 5 at 0.2mm.

The smallest jet is a number 3 at 0.15mm.

You will find that the burner performs slightly differently on a day-to-day basis; this is caused by changes in ambient air pressure and temperature the latter can affect gas canister pressure.
The gas canister will also very in pressure due to content volume and temperature, especially when gas is being drawn off at a fairly high rate.
This will cause the temperature of the canister to fall as the liquid gas is vaporised… leading to reduced pressure.

One of the best ways to eliminate these pressure variations is to fit a constant pressure regulator… these can be purchased for model steam use but can also be made in the workshop… I can Email you some details if you feel the need.

One last observation...
On the burner mounting ring there are some locating screws going into the side wall of the mixer tube... have you sealed the threads using a gas tight sealant?

Hope this helps you on your way.

Best regards.

Sandy.

PS… watched the video of you running your ETA at the show, excellent stuff… bet you are glad it was not a 7” x 8” team racer prop though… they REALLY BITE!!!

[Ramon Wilson]

I'm impressed George, to say the least. As an ex runner whose knees are now totally shot at 70 you are fortunate indeed to be able to exercise so well - long may it continue for you 

Sandy - really pleased to hear from you. I had just begun to think that maybe you weren't feeling too good so it's good to see you back.

I have a little update and a few questions - hopefully not too many

Firstly though, I have followed your design faithfully up until drilling the jet. As the smallest drill I had was a #80 I thought I would try it to see what happened. I'm heartened by your comment that you feel its nearly there and can see the merit of what you suggest so will follow that path closely. Hopefully the .2 and .3mm drills will arrive tomorrow to enable progress on that front.

I'm still considering exactly what type of gas/gas supply to fit. I have been reading about using liquid gas from the tank and vapourising it at the burner to prevent the cooling off effect - I must admit I favour going down this route as to me it seems a practical way of addressing the cooling problem - can you or any one else - George? offer any advice on this method? It seems that another advantage is that Butane as opposed to Butane/Propane mix can be used

Re the screw on the mixing chamber. There is only the one. The fit between the chamber and the mounting ring is a good slip fit - the screw is there mainly to stop it rotating. I had thought about the need to seal it but was not going to until final assembly - would any leakage past this have a significant effect on the flame? The two other screws do not go all the way through the flue tube. They are just to retain it and prevent it too from rotating and locate in recesses drilled halfway through the flue material thickness.  It's mounted vertically today just to see how it looks - is there a preferred way?


Looking for some info on valves today I came across a long ago filed article on gas burners by Peter Arnot. On the drawing of a similar burner albeit 4.1/2" dia across the mixing chamber he shows a stub of material  to act as a turbulator  in front of the entrance of the mixer tube. Would doing the same be of any benefit?

I particularly wanted to use all the old Stuart Turner fittings - mainly for nostalgic reasons and in keeping with the original so have modified the steam valve and begun to look at the pipework layout. The red tape shows where a tee piece will fit - the tee to the flue 'dryer' and the inline outer end reducing to 1/8 pipe to the whistle.


The original design called for a steam dryer (I don't think it could be considered a superheater!) of a loop of pipe in the funnel but this is the steam dryer I have made this time from 3/16 tube.


However I'm not sure whether to mount this coil as below in the uptake itself which of course will be in hotter gases....


or to mount it the otherway up and inside the funnel - somewhat cooler


As it would free the area within the funnel for an inner flue to increase the draft I would prefer the former but my only doubt is whether the end loop would stand up to the heat over time situated as it would be at the bottom of the flue - Any thoughts on this would be appreciated.

Well I think that's about it for tonight - as usual many thanks for your input

Regards - Ramon

PS Nearly forgot - You're right Sandy, that first wince however wasn't a 'bite' but a (well) bent back finger as it locked due to flooding - that actually hurt more long term than the bite which was bad enough and on a 12 x 5 prop too  - I need to get some practice in

[K.B.C]

George,

I am puzzled by your use of the term ‘Blowback’ in relation to high gas velocity.
Can you explain what you are suggesting?

From a burner point of view this term usually relates to the gas/air mix being delivered at a lower velocity than the flame front… hence the flame can burn (blow) back into the mixer chamber, or even right back to the gas jet… not a good idea.

The gas/air velocity being too low usually causes this.




Sandy

Not only do I puzzle you but I do so to myself regularly.

I have always thought that this blow back that I experienced was do to the velocity of the gas being so high that it ignited below the Ceramic and occasionally pop back thro' the air tube holes.

I will now try experimenting with larger jets and control the flow of gas to the burner to see what happens.
I use at present in a 2.5" dia burner a No 8 Jet and as I am able to adjust the jet holder to position the jet in various position at the air holes to get a steady burn.

My main problem is that nobody at my club G.R.M.B.C is interested in building boilers and engines and those that are interested in steam buy and install, so since my mate who had the same interests as myself, passed away some time ago there is nobody to bounce and discuss ideas with.
As you probably know my club is very interested in Tug and towing, also those long gray pointy boats, so it's good to know that you lurk in the background to keep us right, thanks for yor input.

George.

[SandCam]

Hi Ramon,

Yes, I am ok myself, thanks for your concern, but have had a rather upsetting family issue to get through so have been away for a while.
I will email you later.

I actually felt the burner was operating quite well apart from the excessive flame length, it just needs a few minor changes to optimise it… certainly the jet appears to be too large but you will soon get that sorted with your smaller drills... I would expect a total flame length of about 4"- 5" at the optimum... the slightly smaller jet should bring this closer.

It will, of course, alter in performance when inside the flu; so you will probably need to adjust it a bit more when installed.

Did you make the current jet? Or is it a modified commercial one?

The reason I ask is that the genuine Calorgas jets are counterbored at 2.6mm dia from the thread side to within 0.025” – 0.030” of the tip so as to form a converging jet… the actual jet hole only passes through the thin tip portion.
I also seal the thread using some gas sealant when fitting it to the jet carrier.

I would think that the 0.3mm (size 12) jet would be about right… you may even get away with a number 8 (0.25mm) as used in the 2” vertical burner (see attached PDF)
An 0.2mm (number 5) would be way too small for your burner/boiler.

No worries about the small clamp screw, I was just concerned that it passed through the mixer chamber wall so could possibly leak gas… as it is, any small leakage around the flange will not be an issue, since this will just be air and will supplement the secondary air slots.

Fitting a small diffuser inside the mixer chamber, in line with the jet tube, may help a little in mixing the gas and air it would certainly do no harm to add one.

I actually fit 2 of them on my 2” dia vertical boiler burners… the first one for just that reason… the second one (furthest from the jet tube) is only there to provide a second mounting point.

I did not add one to your design as it is just a larger version of my standard 3 ½” boiler  centre flu burner and this did not need one… it is, however, a bit smaller in dia than yours, so perhaps I should have included one.

The orientation of the burner is not an issue… just mount it for best access to everything else.

If you do decide to fit one use the spacing from the jet tube as shown on the above PDF… the diffuser height needs to be just above the OD of the jet tube.

Steam drier… I would fit it down the flu, as is your preference, this will be the most effective… the only issue is, as you say, possible early failure due to heat exposure.
If you can use fittings with nuts and olives/cones then replacement would be easily possible should failure occur, however, if your fittings (tee etc) are of the soldering type then I would consider changing to a thin walled Stainless Steel tube for the drier.

The biggest problem will be when bringing the boiler up to steam, or when steam flow is shut off… the flu gasses are going to be of the order of 300deg – 400deg C at that location and, without steam passing through it, a copper tube will deteriorate pretty rapidly… stainless will just sit there without issue.

Fitting an inner funnel liner can be beneficial in increasing gas velocity, which can help strip away boundary layers within the flu, but don’t overdo it… you most certainly don’t need to use a blower or any other form of forced draft… this would just draw excess secondary air through the flu, thus cooling the gasses… gas burners don’t need this… coal fires do.
You can also fit the engine exhaust to pass up between the 2 skins rather than passing it up through the inner… this way you don’t get variable draft but still get a good output of steam from the funnel.

I have no personal experience with using liquid gas… for the simple reason I have not yet found a system that works reliably.
Most fall into the trap of not being able to adequately control the gas pressure, which can quickly get out of control.
Gas pressure needs to be reasonably constant or your air/gas mix will go all over the place, leading to erratic burner performance; which is why I suggested a pressure regulator.
I am not sure if any of these would work adequately for use with liquid gas though... although you may be able to use one on the vaporized gas if you can find a way to keep the temperature above returning to liquid.

I am not really sure if you could fit the necessary vaporising coil to your burner without it being vulnerable to external influences, such as cold air drafts and the heat sinking effect of the main boiler full of water... I would think a different burner style (such as the blowtorch type) would be more suitable on this score.

The only possible place would be a tight coil around the outside of the mixer body; however, I would not be convinced that the temperature there would be constant enough… it would certainly take some time to reach a suitable temperature, let alone a stable one.


70/30 Butane/Propane mix has a vapour pressure of 35.8 psig at 60 deg F (15.5deg C)
100% Butane would only be at 11.6psig at that temperature.

If your burner is set up for 70/30 Butane/Propane then to get the same flow using just 100% Butane would mean increasing it’s temperature to approx 98deg F (36.6deg C)

At 100deg F (37.8deg C) Butane would reach 37.5 psig.

10 deg F more and it would rise to 46.1 psig.

Butane also requires more AIR than the mixed gas.

70/30 Butane/Propane requires approx 23.86 cu ft air per cu ft of gas.

100% Butane will require approx 31.02 cu ft air per cu ft of gas.

NOTE... the above is for the gas state... I am not sure how this relates to the liquid state, other than Butane boils at 32deg F at atmospheric pressure.

So… pressure control is going to be one of your biggest problem.
The other is timing the change over from gas to liquid… get it wrong and you have a bigger problem.
By all means experiment, that’s what it is all about… just be very careful and consider how to control it adequately.

As for the Prop issue and the bent finger… ouch, I hated it when that happened… especially with a razor sharp racing prop… I still have some of the resultant scars... you have my sympathy.

Hope this is of some help.

Best regards.

Sandy. 

[SandCam]

George,

I am puzzled by your use of the term ‘Blowback’ in relation to high gas velocity.
Can you explain what you are suggesting?

From a burner point of view this term usually relates to the gas/air mix being delivered at a lower velocity than the flame front… hence the flame can burn (blow) back into the mixer chamber, or even right back to the gas jet… not a good idea.

The gas/air velocity being too low usually causes this.




Sandy

Not only do I puzzle you but I do so to myself regularly.

I have always thought that this blow back that I experienced was do to the velocity of the gas being so high that it ignited below the Ceramic and occasionally pop back thro' the air tube holes.

I will now try experimenting with larger jets and control the flow of gas to the burner to see what happens.
I use at present in a 2.5" dia burner a No 8 Jet and as I am able to adjust the jet holder to position the jet in various position at the air holes to get a steady burn.

My main problem is that nobody at my club G.R.M.B.C is interested in building boilers and engines and those that are interested in steam buy and install, so since my mate who had the same interests as myself, passed away some time ago there is nobody to bounce and discuss ideas with.
As you probably know my club is very interested in Tug and towing, also those long gray pointy boats, so it's good to know that you lurk in the background to keep us right, thanks for yor input.

George.

Hi George,
 Don't worry, I confuse myself often enough.

I had a feeling that was what you were trying to say and YES I used to think that too until I did a lot more delving into the mysterious world of gas burners.

Thats when I found out about flame front speed and how gas/air delivery speed effected the behaviour.

I am sure you find it somewhat frustrating when you get a problem and can't find anyone at your club interested enough to help.

Remember, you only need to PM me if you need to discuss an issues and I will always be happy to assist where I can.

Keep happy and Good on you for being able to keep your cycling up... I am well past that now for health reasons.

All the best.

Sandy.

[fcheslop]

Hi, Iv used liquid gas as per Malcolm's idea using a blow lamp type head running on a 70/30 mix and found it did help and keeps a constant flame.
I can do a few pics if its of any use
Sorry cannot comment on the ceramic burners and can only add welcome to the black art of burner making I always struggle and theres a load of suck it and see and it will be different when in the flue
cheers

[fcheslop]

Hi Sandy, if you had time would you be willing to do a post on burner design as I for one would love to learn more about the subject or point me in the right direction as the amount of scrappers I make is horrendous
Many thanks
frazer

[Ramon Wilson]

Hi Sandy - many thanks once again for your help and interest.

I've had a quick run through but have printed it off and am about to depart for some bedtime reading 

Decided to set the flue in today as preferred but like you have doubts as to its ability to stand the heat. It does have unions so should be easy enough to change.

Hopefully the drills will be here tomorrow - a watched doormat is just like a kettle

Back soon - thanks again - Ramon

[SandCam]

Hi Sandy, if you had time would you be willing to do a post on burner design as I for one would love to learn more about the subject or point me in the right direction as the amount of scrappers I make is horrendous
Many thanks
frazer

Hi Frazer,

Such an article would be quite a huge document as there are just so many variables and types... and would take some considerable time to compile.

I may be able to do a shorter one on ceramic burners at some point, but not at this point in time, since I have a lot of other stuff going on at the moment.

I would be more than happy to discuss, suggest, a design for a specific burner if that would be of help.

Just Pm me and I will attempt to assist.

Best regards.

Sandy.

[Ramon Wilson]

Morning Guys 

Sandy - I have read through your very thorough answers and thoughts to my questions and ideas. Thank you once again for taking the time to support this project with your advice and knowledge - it's really appreciated.

I did make the jet and did drill nearly  all the way through but without checking cannot say what size - probably 2.5. I left 0.5mm for the jet hole to pass so was nearly on target  - The next jets will be as you suggest. I'll fit a diffuser today.

The more I think about the drier the more I agree - it wont last long. I shall try to source some stainless tube - does anyone have any idea what grade would be the most malleable and where I can get some 3/16 od in longer lengths than 12"? In the short term I shall see how it goes - it might be possible to shroud the lower most point with a stainless heat shield .

Your advice not to fit any means of inducing a draft comes in the nick of time - I was about to do that today. My friend John (C) (I have lots of friend 'Johns'!) who gave me the parts for a fan has converted a coal fired horizontal boiler to gas using a flat rectangular ceramic burner. He suggested it as his apparently has a habit of blowing back/extinguishing the flame until he has steam up. I'll leave as is then - just fit an inner flue.

My thinking about using liquid gas came from two sources - mainly from seeing the problems created by cooling (using 70/30 mix) on a couple of the boats at the club. They have no form, not even insulation, of combating the temperature drop and the detrimental effect rapidly develops. Quite by chance I found the article on using liquid gas and felt this would be a path to take to try to reduce this effect.
However, having read your comments I'm now not quite so sure this will be as easy to control as first thought so yes - I would appreciate the info on a regulator. I will go down that route first seeing how much heat I generate on the mixing chamber which is really the only area I have for a vapourising coil. The thought of liquid gas not vapourising where it should is a definite concern  so will put thoughts of this method on the back burner (yes!  ) until a regulated system has been well tested. I intend to make the gas tank so will make provision for the take off just in case.

One more question please - does anyone have any idea of the thread size of the Coleman type gas tanks and whether a tap is available?

Looks like I've got another day in the shop - Sue's painting garden chairs 

Thanks again Sandy

Ramon

[Stuart]

Ramon
Polly engineering have them

Page 39 of the combined catalogue

19 quid though but they do not leak and are well made

Stuart

[Ramon Wilson]

Thanks Stuart - I had seen them and will go that route if all else fails but I would prefer to make one if I can - just need to know the size.

Ramon