johnsmachines

machines which I have made, am making, or intend to make, and some other stuff. If you find this site interesting, please leave a comment.

Tag: steam engine

TRIPLE UPDATE

A day out of the workshop for looking after my grandson, and watching my daughters husbands eldest son from his first marriage playing football, and cheering him on for kicking 3 goals in the last quarter….!!

But back into the workshop today.

First I bored the big end bearings.

IMG_2703

Bored on the mill, not CNC for a change. After some fiddling to get the measurement correct on the first big end, the next two took only a few moments.

Then some finishing turning and polishing for the con rods, and a decorative groove.

Then bored and reamed the the crossheads for gudgeon pins.  For once, the 3 cylinders were the same, so measure the first then quickly repeat the process for the next two.

Then, for a bit of fun, I assembled everything done so far.

IMG_2704

The crankshaft, con rods, crossheads, gudgeon pins.  The big cylinder in the foreground is a handle which I use to turn over the crankshaft manually or in the lathe.  It is also a threading handle (home made).

IMG_2706

Close up of the engine guts.

IMG_2707

The whole engine, so far. It is quite exciting to see it coming together. SWMBO is not impressed with it sitting on the kitchen table.

Next on my list, the pistons and piston rods.   Big decision.   Rings.   Cast iron or packing.

ps.  Neither.  Cast iron rings in gunmetal cylinders not a good idea.  Gunmetal would wear excessively.  Graphite impregnated packing would be OK, but I am probably going to use Viton O rings.  Easy to install, fairly inexpensive, and quite suitable in an engine which is unlikely to see any serious work.

TIGHT MAIN BEARINGS NEED GUMPTION

With the crankshaft installed and the main bearings snugged down, I tried to turn the crankshaft by hand.  It should have felt tight and smooth and firm, but it was, like the curate’s egg, only good in parts.  There were tight spots, and even when the mains were loosened, there were tight spots.

So I tried turning the crankshaft by hand some more, thinking that the high spots would wear down.  But with only minimal improvement.   Clearly some more aggressive lapping would be required.

I have some diamond lapping paste, in various grades, and I have no doubt that it would have been effective at taking off the high spots.  The problem is that the diamond dust can impregnate the softer metal in the bearing ie. the gunmetal, and remain there, continuing to score and wear the bearings for ever.

A colleague suggested using a grinding paste containing a much softer grinding material.  Toothpaste was mentioned, along with some kitchen scouring cleaners.  I could not find any such things in my workshop, so off to the supermarket I went.

SWMBO claims that I have no idea about supermarket shopping, and on this occasion, she was correct.  Confronted by dozens if not hundreds of cleaning agents, I was totally bewildered by the array of options.  So I did what any self respecting red blooded Aussie male would do…  I rang her and asked which brand to buy.

This is what I bought…..


Gumption kitchen laundry cleaner

Gumption bathroom kitchen laundry cleaner.

I applied the Gumption to the bearings…

IMG_2698

Using a small brush which any gynaecologist will recognise..

And set up the crasnkshaft – base – bearings in the lathe …..

IMG_2695

And ran the lathe at 40 rpm for a few minutes.  The temporary nature of the abrasive in the cleaner was evident by the scratching noise which stopped after a few revolutions.  The 5hp lathe motor was required to overcome the friction caused by the paste.   Very quickly, the resistance to turning disappeared, and it was obvious that the Gumption was working. (later, when I used the same method on the big end bearings, I found that it was quicker and easier to turn the motor by hand. Huge force was not necessary. And it took only 5-10 revolutions to do the job).

After grinding with Gumption, the bearings were disassembled so the paste could be cleaned off.

After grinding with Gumption, the bearings were disassembled so the paste could be cleaned off.  The high spots which were removed were quite visible.

After cleaning off the remains of the paste, and assembling the crankshaft, I retested the crankshaft & bearings. An amazing difference! Now it was smooth, and I was able to turn the shaft by hand, even with the bearing nuts tightened quite substantially. I might repeat the process to improve things even more.

Very impressed with Gumption. Great stuff.

Con rods for triple -3 finished!

The finished con rods.  I wont bore you with the photos of milling the wishbone slots.

The finished con rods. I wont bore you with the photos of milling the wishbone slots.

The crossheads have been dimensioned, and the big end bearings machined, and glued with Loctite in prpeatyaration (sorry, too many reds after dinner), preparation for accurate boring.

The crossheads have been dimensioned, and the big end bearings machined, and glued with Loctite in prpeatyaration (sorry, too many reds after dinner), preparation for accurate boring.

The big end bearings, machined, and glued, ready for accurate boring.  Is that what I am doing to you???

The big end bearings, machined, and glued, ready for accurate boring. Is that what I am doing to you???

CON RODS for TRIPLE -2

The con rod shafts have a taper of approx 1.5 degrees.  I turned the shafts between centres, using a tangential tool. The HSS cutter has a round cross section which gives a good finish, and automatically fillets the joins.

The con rod shafts have a taper of approx 1.5 degrees. I turned the shafts between centres, using a tangential tool.(a Diamond tool holder from Eccentric Engineering).  The HSS cutter has a round cross section which gives a good finish, and automatically fillets the joins.

IMG_2673

Of course left and right hand tools are required to do the whole taper.

Another jig! The con rod is difficult to hold accurately for milling, so I made a jig to assist. 10mm aluminium plate, with a cut out section to accept the con rod casting.

Another jig!
The con rod casting is difficult to hold accurately for milling, so I made a jig to assist.
10mm aluminium plate, with a cut out section to accept the con rod casting.

IMG_2675

The jig had to be made as accurately as possible. So it was milled square and parallel, then centre pins were installed to hold the casting by the previously drilled centres. A further pin with a sharp point was installed to stop the casting from rotating during the drilling and reaming for the gudgeon pin. That gudgeon pin hole was continued through the jig, so a large pin could be inserted to really hold the casting securely. It also allowed an accurate 180 degree rotation of the casting.

IMG_2676

A bit clearer with the swarf swept away!

IMG_2677

You can see the gudgeon pin in place, while further surfaces are milled.

IMG_2678

Close up of the jig and my metal workers’ dirty hand.   Just as well there is no more gynaecology.

IMG_2679

Progress!

IMG_2680

Not a clear shot, but here I am using the flutes of a milling bit to smooth the flat section under the gudgeon pin. Not ideal but it worked OK.  Tomorrow I plan to round off the external surfaces and mill the slot for the cross head.    Not much to show for a full day in the workshop, but it was fun…

CON RODS FOR TRIPLE

There are three connecting rods, and despite the different cylinder sizes, the 3 rods are identical. Due to the fact that the stroke for each cylinder is identical. It is only the bore which differs.

The castings for the con rods did not permit them to be held in a lathe chuck, even an independant 4 jaw. So I drilled centres, and held them between centres for turning the shafts.

IMG_2669

The con rod castings, after the initial tidy up on the belt and disk sander.

The con rod castings, after the initial tidy up on the belt and disk sander.

IMG_2670

The drilled centres, and rather rough centre lines.

MAIN BEARINGS FOR TRIPLE

Each main bearing consists of 2 gunmetal halves which fit into a slot in the base, and a cap which bolts to the base.  There are 6 of these.

I machined the gunmetal castings, and made the caps.

Before I finished the machining or drilled the holes for the bolts, my phase changer failed, so I finished the job on my (single phase) drill press. Not ideal but adequate.

The Phase Changer has failed at least once every year since I bought it 5-6 years ago.  It is the least reliable machine in my workshop.  Repairs to it seem to take at least 3-4 weeks on each occasion, which is frustrating.  I will borrow a 3 phase diesel generator to keep the workshop in action while waiting (again) for the repairs.

One of the 6 main bearings and caps.  The hole has been roughed out, ready for accurate boring

One of the 6 main bearings and caps. The hole has been roughed out, ready for accurate boring

The 6 main bearings sitting in their slots.  The hold down bolts are ready to be installed.  The bearing surfaces will be bored when I have some 3 phase power again.

The 6 main bearings sitting in their slots. The hold down bolts are ready to be installed. The bearing surfaces will be bored when I have some 3 phase power again.

Other People’s Triples

Not sure about the position of the apostrophe.

But if, like me, you enjoy looking at engines, then stop thinking about the apostrophe and watch the videos.

CRANKSHAFT FINISHED!

It is not perfect, but it will do.,

Today I removed the support blocks (heated with a gas torch to soften the Loctite) cleaned up the sharp edges, shaped the flanges, and polished it.

Next on the list is to make and fit the main bearings.  Thank goodness they are made from gunmetal.  There are 6 of them, and each has 3 components to be shaped and fitted.

IMG_2641

The stainless steel has a nice lustre, but it is difficult to machine.

CRANKSHAFT, almost finished

The crankshaft is almost finished! It is not perfect, and I am considering making another one. But for a first effort (at a crankshaft machined from solid), it is not too bad.   Actually, it was the second effort.  The first one was binned due to a 3mm eror.

I made the job much more difficult by using stainless steel as the material. Stainless is hard, and must be machined with carbide tooling.  Problems with chatter and tools blunting.  The big ends needed thin tools with a lot of overhang. After my initial unsuccessful effort, a friend suggested the use of a Gibraltar toolpost, which certainly reduced the chatter. (thanks David M).

IMG_2638

Turning the big end bearings, using a carbide parting tool held in “Gibraltar” tool post. Actually, it is an “Uluru” toolpost. Whatever the name, it worked better than the normal quick change toolpost on my lathe.

After an estimated further 12 hours of turning and milling, the crankshaft is almost finished.

IMG_2640

The support blocks glued with Loctite to support the main shaft, are still in place.

 Ahuman hand for scale.  Refer back to the original lump of 50.8,, diameter stainless steel pics to see how much material has been removed, leaving the crankshaft.  I have a large amount of razor wire to dispose of, and many cuts on my hands and face.  This is mongrel material to machine and I hope to never use it again.  At least my crankshaft should not rust.

A human hand for scale. Refer back to the original photos to see the lump of 50.8,, diameter stainless steel  to see how much material has been removed, leaving the crankshaft. I have a large amount of razor wire to dispose of, and many cuts on my hands and face. This is mongrel material to machine and I hope to never use it again. At least my crankshaft should not rust.

TRIPLE EXPANSION STEAM ENGINE ANIMATION

This is a very nice animation and summary of the triple expansion engines and steam turbine on the Titanic.

Note that the triple expansion engines  have 4 cylinders.  There are 2 low pressure cylinders.

Be prepared to hit the pause button on some of the old photos.

More Crankshaft. Roughed on mill, finished on lathe.

This is the first big end bearing.  The bearing surface was roughed out on the mill (held between centres using the dividing head), then the excess  around the flanges was removed on the mill (with the workpiece held in the milling vice),  then the bearing surface was finished in the lathe.

This is the first big end bearing. The bearing surface was roughed out on the mill (held between centres using the dividing head), then the excess around the flanges was removed on the mill (with the workpiece held in the milling vice), then the bearing surface was finished in the lathe.   There is a crankshaft buried in that lump of steel.  I just have to remove all of the bits which are not crankshaft.  (apologies to Michelangelo).

Making a start on the second big end. There is a block of steel loctited in the first big end so it is not bent when the workpiece is compressed between centres while the other big ends are machined. The second big end is yet to be finished on the lathe.

Making a start on the second big end.
There is a block of steel loctited in the first big end so it is not bent when the workpiece is compressed between centres while the other big ends are machined.
The second big end is yet to be finished on the lathe.

IMG_2620

A slightly different view showing the block glued into the first machined big end, and the almost finished second big end. This is the milling machine setup.

CRANKSHAFT- using the mill instead of lathe

My first attempt at making a crankshaft for the triple expansion steam engine involved turning the workpiece between centres.

It worked in a fashion, but only at 200rpm.  At that speed, not  great finish.  And frankly it was scary and hairy!

Then I discovered that I had made a 3mm mistake in the position of the middle big end bearing, so it all had to be done again.

IMG_2612

The first method of making the crankshaft. Slow, not a great finish, and fairly hairy, despite the 2 tonne lathe.

So today, with some new steel, I decided to use the vertical mill instead of lathe. Actually, I turned the cylinder to size on the lathe, after drilling the centres on the mill. I tried to turn the big ends on the lathe, (eccentric turning, using counterweights this time) but I was still not happy with the result from the intermittent turning.
So I tried a different method, using the vertical mill, and rotary table, set up as in the photos.

IMG_2615

Setup on the vertical mill. The rotary table was turned by hand… rather tedious. The 8mm end mill was run at 1600 rpm, taking off 0.5mm on each revolution. A slow process, but it felt safe, and the finish was excellent.

IMG_2617

The rotary table setup.

IMG_2616

Only 10mm of material remains, for the big end bearing. Before excavating the material for the next 2 big ends, I will glue (Loctite) blocks into the gaps to provide support. The mains will be turned or milled last. I might still finish the bearings on the lathe. Not yet decided. Watch this space,

After my initial problems with making the crankshaft, I asked and obtained advice from my Model Engineering Club colleagues. That resulted in the decision to machine the big ends first (thanks Stuart) and counterweight the turning when doing offset turning (thanks Malcolm). Also thanks to Peter V, for double checking my measurements this time, and jollying me along.

Still a lot to go to finish the crankshaft, but I can see that this method will work.  I might motorise the rotary table before I start any more of the 8 remaining bearings.

p.s. 7 December 2019 (4+ years later)  I did eventually motorise the rotary table, with a stepper motor, and it is CNC controlled, along with the XYZ axes on the mill, by Mach 3.   The triple expansion engine has been running on steam for over a year, and is virtually finished except for some optional small fittings (like cylinder waste drains, builder’s label).

How a surgeon starts awkward, tiny nuts.

BA7 nuts are tiny. The thread is 2.38mm diameter. Admittedly, there are smaller nuts, but I have had so many problems with the BA7, that I do not want to even contemplate the even smaller ones.

If I drop a BA7 nut, I have about a 50% chance of seeing it on the floor. There must be a small fortune in BA7 nuts on the floor of my workshop, or wherever they bounce to.

The steam engine which I am currently building has several hundred of these tiny fasteners, and many of them are in inaccessible cavities, at least relatively inaccessible to my 65 year old fingers.

The more accessible BA7 bolts and studs can have nuts fitted with the assistance of a 4mm jeweller’s tube spanner. I added some usefulness to the tube spanner by turning its outside wall thinner, to decrease the space it occupies, but even so, there are many locations where no tube spanner, however modified, or open ender, or needle nosed pliers will reach, and fingers are required.

So, I had a brain wave yesterday, about a method of starting small nuts on relatively inaccessible studs and it works! This might not be an original idea, but it is to me.

It requires a sharp needle, on a handle, with an appropriate bend near the end of the needle. The sharp end of the needle is exposed. In my previous life I was a surgeon, so I have a supply of medical needles, and they are ideal.  A syringe makes a good handle.

The nut is placed on the needle, (carefully).

The needle point is placed in the centre of the end of the stud or bolt, carefully to avoid the nut slipping off prematurely, and the needle is angled so it is in line with the stud. The needle needs to be sharp, so it does not slip off the end of the stud.

The nut slips down onto the stud, and it can be spun with a finger tip until it attaches to the stud. The needle is then (carefully) placed away, and the nut is tightened down by whatever means are possible.

This method requires some dexterity, but it can change an impossible task into a merely difficult one.

Ps. If you use medical needles, make sure that they are new. Some diseases like hepatitis can be transmitted by needle stick injury.

The needle tip is pushed into the end of the stud/bolt.  The nut slips onto the end of the stud, and is then spun with a finger tip until it engages with the thread.

The needle tip is pushed into the end of the stud/bolt. The nut slips onto the end of the stud, and is then spun with a finger tip until it engages with the thread.

CRANKSHAFT – early steps

The triple expansion steam engine crankshaft has 6 main bearings, 3 big ends, and 4 positions where eccentrics attach.

It is about 240mm long, machined from 50.8mm mild steel rod.

The mains are turned from centrally positioned centres, the big ends from eccentrically positioned “centres”.

The centres were drilled on the CNC milling machine, after the locating the top of the bar

The centres were drilled on the CNC milling machine, after the locating the top of the bar

IMG_2609

The eccentric centres were calculated, and drilled using CNC to get the positions.  The longitudinal scribed line was used to position the other end of the rod.

IMG_2610

Turning between centres, using a lathe dog. This will not be a quick job.

And this is how I would like to make a crankshaft…

WHEEL BALANCER- another home made tool

This is a jig for balancing wheels for steam engines, grinding wheels etc.

The jig has 3 adjustable pointed bolt legs for levelling.

The top of the jig was flattened on a surface grinder, then the silver steel bars were bolted (without tension).

If the wheel is perfectly balanced it will not roll.

IMG_2591

Wheel balancer, with steam engine wheel yet to be finished.

Bolton 12 Beam Engine Under Steam

A YouTube video of a Bolton 12 running under steam.  Not mine, (the workshop is much too tidy) but definitely inspires me to hook mine up to a boiler.

STEAM CHESTS for TRIPLE

The time which I have had spare in the past few days has been spent tidying up the workshop,  sorting tools and putting them away.  Today I spent a few hours making a start on the intermediate and low pressure steam chests.

Roughed them out and CNC’d a boss on the bottom of each chest.  Then roughed out the steam chest covers.

This is the progress to date.

IMG_2574

So far I have drilled, tapped and inserted ~180 BA7 screws and studs. And there are a lot more to go. The steam chests and covers are sitting on the base.

Attaching the cylinder block bases to the cylinder blocks was tricky.  I drilled the holes with the bases glued to the blocks using Loctite, and then tapped the holes and inserted the screws.  I will apply some heat to break down the Loctite.

It is quite difficult to insert the screws to the underside of the block.  Many are quite inaccessible.  There have been multiple tear downs of the model, with many more to go, so only a small number of screws are currently inserted.  I will have to work out an order of assembly, to make the assembly process as logical and easy as possible.

I am starting to consider which method I will use to make the crankshaft.  It has 6 main bearings, 3 big end bearings, and locations for 3 valve eccentrics and an oil pump.  It is quite complex.  Fabricate or turn from the solid.  I am tending to the latter, but we will see.

BOLTING THE TRIPLE CYLINDER HEADS, and another jig.

The 56 bolts which attach the cylinder heads, were installed today.

First, the heads were bolted into position with a jig.

IMG_2567

The work is held in position on the milling machine table, using 4 hold downs, and 2 T slot locating fixtures. The jig also helps to secure the work to the table.

The jig fits into the milling machine T slot, and the bolts are exactly positioned in the centre of the heads.

The bolts hold the heads in place while the centre drilling, through drilling and thread tapping takes place.

That is 4 processes for each of the 56 holes.  Even semi automating the process using CNC, it took 6 hours, including setting up, making the jig, and finally installing the bolts.

IMG_2569

Drilling the relief holes in the heads, after preliminary centre drilling. Those holes are only 2.5mm diameter, and 12mm deep. Despite the tiny drill size there were no breakages. The drill was set at 2500 rpm, feed rate 50mm per minute, and with pecks set at 2mm. A cutting lubricant was used.

IMG_2570

The head bolts in place. The bolts are BA7, which is pretty tiny, but they look the part, yes? The highest “density” of bolts is on the smallest cylinder head, which is on the high pressure cylinder. The threaded holes in the centre of the heads are for the pressure relief valves.

I have left the set up intact on the milling machine, until I am sure that there are no further processes I can perform with the block in this position.

The

HOW TO MAKE A FULL SIZE STEAM ENGINE

Click on the link to watch a movie-documentary from the 1930’s.
If you are a steam head, you will love it.

Cylinder Bases. Lathe or milling machine?

I read an expert treatise on making a double expansion steam engine, and I imagine that the comments applies to triples also.  One aspect emphasised the importance of accuracy in making the cylinder bases.  The parallelism of the surfaces, the concentricity of the piston rod hole and the other circular elements, and the thickness. The usual method for making these items is to turn them in a lathe with a 4 jaw chuck, then to reverse the item in the 4 jaw to turn the other face.  It is possible, but very fiddly and time consuming, and relies on expertise, patience, good eyesight, and a good lathe.   All of which are in short supply around here. A triple expansion steam engine requires 3 of these base plates, and while there are some common dimensions, the cylinder bores are all different.  Many of the screw holes are common to the 3 plates.  The thicknesses are all the same. To shorten this rather boring epistle, I decided to have a go at making the base plates on the CNC mill.  Given my previous muck ups, broken bits, crashes, this was a courageous decision, as evidenced by having to bin the first effort.  But the next 3 all seemed to work OK. First I studied the plans and noted the common elements, then I made a jig, with holes drilled at the common positions.

IMG_2543

The underside of the jig, showing the 5mm centre hole and the counterbored holes at the attachment points.

IMG_2544

The topside of the jig, after the first and second baseplates were drilled, thicknessed and shaped. The jig needed to be made very accurately, to retain position of the workpiece after it was reversed, so both faces could be milled. I am told that CNCers build up a collection of jigs over time. They are rarely used again.

IMG_2531

CNC milling the central boss. 20.48mm diameter, and accurate. Note the red positioning device, enabling the workpiece to be removed to check measurements, then replaced exactly in the same position.

To see a video of the CNC mill cutting the external profile click on the link below http://youtu.be/m0d5yuX96Uc

IMG_2541

The cylinder baseplates screwed to the columns. Some trimming of the column tops is required. The baseplates are centered accurately, as far as I can measure. Note that the central jig separating the columns has been removed, and the baseplates are now holding the column tops in position. The columns appear to be lining up correctly.

IMG_2538

The next example of using the CNC mill to perform a task which is normally done on the lathe. The mill cutter is travelling in diminishing circles, producing a central boss, and a flat surface.

IMG_2540

The boss finished to size (10mm dia) and flat surface.

BTW.  In a previous post I mentioned a 1 mm inaccuracy in a CNC milled part.  It happened again when I milled the first base plate, which ended up exactly 2mm smaller than programmed, and had to be re-made.  This time I discovered the cause of the inaccuracy….   I had used an 8mm milling cutter, but had forgotten to tell the CNC computer that I had changed from using the 6mm cutter.  The CNC machine did not notice the change, and cut the part exactly as instructed, very accurately, 2mm smaller than intended.  CNC machines are incredibly clever, but very very dumb.  They do exactly as instructed, even if the instruction is wrong.

%d bloggers like this: