Member postings for Tony Martyr

I have a problem in locating a small positive pressure/negative pressure dial gauge. I may try to rig up a U tube to do the job. I have been troubled by condenser problems during my working life while working for WH Allen. Finding a steam leak is very easy but finding a vacuum leak is a nightmare. I am about 3 weeks away from a first trial run and will report on my findings.

Tony

"Tony has had some good input, that's for sure"!! Amen to that!

Thanks Guys - I'm glad I asked the question because the more I thought about it the more unsure I became. However while you have been considering the question I have finally found the source of all wisdom concerning marine engines and steam plant which I thought had been lost in a house move.

The book has no title (!) but the foreword says it is a reprint (bound photocopy) produced by The Nabu Public Domain Reprints - made in the USA from a series of textbooks for marine engineers originally printed (as 11 separate volumes) printed between 1902 and 1907.

The answer for all airpumped tubed condensers is that water enters at the bottom or cool side/section and exits at the top or hot section - the book covers several designs but seems to be the general rule.

With my model I am more concerned in raising a vacuum than getting the best thermal efficiency so the condensate return will go into the top of the feed water tank (cylinder lubrication should float on top?). The engine has two feed water pumps which will draw from the bottom of the tank and whose discharge will tee into the boiler feed/hand-pump line. There is a manually operated feed by-pass that just returns to the tank.

The condenser will have a separate water tank the water from which I intend to circulate with a small submerged 12v aquarium pump.

I don't know how all this is going to perform but after spending lots of money and time in building the engine I thought it a bit of a crime to have it sitting as some sort of display item (my work is not exhibition quality although the casual visitor would be impressed) so I have built a stainless steel plated base in two parts - the engine section with all the tubes terminating at fixed manifolds and the boiler section housing the two water tanks, the boiler, its tubing and feed pump. Now if I can't get the system to work in a manner that is suitable and safe to 'show off', then I'll disconnect the two sections, mount the engine on a hardwood block and sulk.

Tony

I’im building the interface systems for my triple expansion engine which includes a stand alone cooling water tank/tower for the condenser. The condenser is a two compartment water tube unit meaning the water flows from a pump from the entry end then flows back through the second tube bank before returning to the tank.

The steam enters the top of the condenser body and condensate is pumped out of the bottom.

Question is: which way does the cooling water flow? Should it enter the top, hot section and flow Down or should it get pumped into the bottom and flow up?

i wish I had paid more attention during a previous life when I installed Allen steam turbines fitted with under slung condensers!

Tony

Hi Ramon: because this is a Woolf type engine, that is without inlet chambers before the IP and LP valves the timing is critical so as to avoid stalling back pressure when the HP exhaust starts when running on air. This problem held me up for a couple of attempts over two years. The IP valve has to be opening just as the HP is exhausting.

because air is a compressed gas while steam is an expanding gas when running on air only the HP does any work so at the first run I opened the IP Nd LP cylinder drain cocks but later found it runs with them shut so the air is having to go right through to the condenser.

It has been a long and, due to the cost of the castings, a very careful construction. As I have rebuilt it I have been very impressed by some of my machining!! Not sure I could do it nowadays.

i am now mounting it on a sheet of SS chequered plate and frame and bringing all the water and condensate pipes to a manifold so I can connect it to a matching frame with the boiler and water tank system

Edited By JasonB on 01/02/2021 18:43:13

About 10 years ago I bought a set of castings at the Midlands Model Engineering exhibition just as everyone was packing up, so at a discounted price. In between retirement, moving house and having two books published I managed to do the first build but failed to get it to run with compressed air. I stuck in a box for a year and sulked.

Lockdown prompted me to get it out and strip, then rebuild the whole thing after working out the optimum timing of, and between, the three cylinders.

Today it has run for the first time 😀

I am now designing a frame mounted system that incorporates my vertical boiler with a feed water tank and a CW tank for the condenser together with the condensate and feed water pumps on the engine

While using an electrical fan heater to raise my workbench area to a balmy 10C is very clearly visible on the meter display in terms of £/min, the short term peak of using both heater and a powerful wood router really got me into trouble. Trying to explain that the rate of expenditure over a period of one minute could not be extrapolated to a realistic annual rate of spend did not convince my critics who seem have become fixated on thereduction of electricity bill - which never registered before the arrival of the meter.

I'm tempted to do some maintenance on my old Fergy tractor where I can use a gas heater the other side of the field.

I understand that companies servicing 'in-door hobbies' are experiencing something of a lock-down boom - I thought it was just me!.
My workshop is an unheated in-shed space and I am finding that there is a correlation between the size of threads, or nuts, I can handle and the ambient temperature. While I have managed to fit cladding with 10BA brass screws via tweezers and jewelers screw driver today I have found 7 BA stuff, particularly in difficult to reach places, impossible to handle below 5 degrees C. So I have started to make a boiler/engine/feed system frame for my triple expansion engine using 3BA for the first time in my life - but I can get a grip of them!

My problems have started since the family have installed an electrical Smart Meter and I have fallen under its audit - beware!

In traditional marine work it was easier to lock a nut on a stud, by split-pin or lock nut, than to lock a bolt which needed tab washers or wire-locking of the whole ring of bolts.

In more modern marine diesel work it is the need to have equal torque setting that is important and that is easier with nuts on studs.

Tony

The engine has indeed got gunmetal cylinders and two part gunmetal pistons. The hard brass rings of the design have a scarfed joint (gap) and an excentric bore giving a 3/32 thickness opposite the gap which is at a 1/16 thickness.

I have made one for the HP cylinder which will have steam at about 80psi inlet. Since i'm going to the effort of a complete rebuild I think I will get some material and follow the design for the IP and use graphite in the LP which exhausts into the condensor. It is not an easy engine to work on once assembled and has required more modified spanners and nut runners than any other project I have undertaken.

Thanks for the suggestions

Tony

On stripping the Bolton/Bertinat triple expansion engine that I had machined and assembled in the 1990s (never run because I hadn't by then built a boiler of sufficient size), I find that there are no piston rings in the IP and LP cylinders.

The design calls for hard brass rings of varied cross section and since the LP is 1.5" diameter I now remember that the material was not to hand - still isn't.

Smaller engines seem to run OK when fitted with graphite string packing in leu of rings but I'm concerned about its fixing in the larger grooves (already machined)

Any suggestions of suitable materials to go in 1/4 x 1/8" deep gunmetal piston grooves which will run on steam?

Tony

Since the working loadlines in the top and bottom halves must be 50 odd degrees centred on the vertical centre-line I don't think the crescent shaped gap around the halving joint is going to be of concern, indeed it may aid lubrication. As Jason says it all depends on the amount the originals are oversized. I will do some careful measurement and report back.

Tony

Hi Brian, Your reply has triggered a memory of my apprenticeship days and metalling of big gearbox bearings - this led me to the answer! I will mill a small amount of each of the halving joints, thus pinching the bore below size on the vertical axis and then machine out to the correct size, there is sufficient metal in the casting to allow this - I don't have to add metal!!

cheers - Tony

I have finally got round to stripping and rebuilding a model triple expansion engine that I built from Reeves casting some years ago. I am very impressed by some of the work (!?) except that all the excentric sheaves seem to be too loose - can't be wear from the few hours run so I must of not appreciated the clearances needed when I built the engine. The thought of machining a completely new set of 6 sheaves or excentrics fills me with dread so I wondered about 'remetaling' the sheave bores with silver solder and reboring. This is probably more difficult than making new excentrics but seems more interesting.

Has anyone done such remedial work succesfully?

Tony

Hi Dave

The lakeland sheet is 0.005" thick so I intend to try it out on the cylinder faces where the use of paper has proved very difficult to execute

Tony

I'm sure I have seen mention here on the possible use of the 'Lakeland' oven liner sheet as a gasket material - but I can't find the posting.

It would appear to be a good material with which to cut intricate gasket shapes and use with a 'mere smear' of sealant

Has anyone experience of using it for steam engine gaskets?

Tony

Thanks Jason - I do like the photos. I would like to know how the cross-head slides within the main frame were set up for machining, perhaps on a horizontal borer but its a horribly 'bouncy' intermittant cut demanding a very ridgid set-up..

As for the hole in the excentric sheave as the answer to the adjustment of the valve timing - of course!
Why of earth didn't I see that as the answer - I'm trying to think of an excuse other than senility.

Thanks for your help

Rik: I don't know how far you've got but to get the 4 bearing alignment sorted out in the horizontal plane I machined the two inner bearing pedestals and then made a plain shaft jig to check the height of the two frames having already machined the bearing seatings - it meant having to take the castings out of the milling machine a couple of times but resetting with a precision level worked OK.

Tony

I have just finished my first build and run on air and steam of a Double Tangye engine.

I have now stripped it in order to make some modifications and cure some leaks.

The drawing shows a undimensioned tapping on the top centre-line of each cylinder labled "tap for oiler".

What sort of 'oiler' would function against full steam pressure? Would that be an oil cup with a screw-cap for use before and after running?

The two modifications will be to improve the function, probably at the expense of form and style.
1. The valve excentrics can only be adjusted by removing the sheaves which is more than a little inconvenient - redesign required.
2. The governors looks pretty but doesn't work well so both the inlet valve and the governors drive need replacing to include ball bearings.

Rather amazed that a design would put 4 close coupled bearings in line on a rigid shaft - my apprentice test piece was scraping 3 in line and that was bad enough - these are worse because the caps of two of them are at 45 degrees making disassembly unnecessarily difficult. A bit of a challenge!

Thanks to all - I have now found what I needed from Mamod spares

Look for a second hand Site Cabin which are based on ISO containers. They already have the door, windows a power-cable inlet and security shutters fitted.