[bogstandard]

I have a totally manual workshop, consisting of an Atlas 10f lathe dating from the late 1930's, a Picador mill/drill from the 80's and a Herbert manual surface grinder from the 50's. I have restored them all and brought them up to date.
Later this year I hope to invest in a small CNC mill, as even with 3 axis digital readout on my mill it is very time consuming drilling and reaming so many holes in the projects I have undertaken.
I have already built and run numerous steam engines and one four stroke side valve, water cooled petrol engine.
At the moment I am building a few twin cylinder oscillators (wobblers for those in the US) and the attached picture shows what stage I am up to, they all need surface grinding all over, but that comes after the tapping stage.

[nick.gilling]

They look excellent. I thought of doing a batch myself and selling a few off!

A surface grinder is a nice luxury to have and gives a very professional look and is obviously better than rubbing on a bit of emery cloth like I have to do for the port faces!

Got two questions...

What is the feature at the end of each cylinder? Is that cosmetic or just to further reduce the friction?

Also, why have you chosen to put the ports where they are instead of at the extreme ends of the cylinder? I have never thought of doing that before simply because of the more awkward angled hole. I can think of a few reasons for doing it now I've seen yours though. Have you done it to optomise the distance between the ports? (that was governed by the length of the piston rod and stroke on mine but your way gives more flexibility) Or was it so that your cylinder cover bolts don't interfere with the port? Are the covers going to be bolted? The only other reason I can think of is so that the port doesn't become uncovered by the cylinder when at 90 deg btdc like the mistake I made on mine! Or am I off the mark with these thoughts?

Thanks, you've given me some more ideas, although I want to tackle something more complicated than an oscillator next. I'm fed up of making those now but at least it was an inexpensive way to get back into the swing of things.

[bogstandard]

Hi Nick,
The 'feature' is just another way to reduce the friction to as little as possible.
The ports on this engine are all either straight in or up and down, ie. drill in the side, then drill from the top straight down to hit the side drilling, no complicated angle drilling at all, then just a small milled 'nick' connects the port to either the top or bottom of the piston (just enough to allow steam to bypass the top & bottom cover locating flanges).
The top covers are all bolted on with 2mm stainless cap screws.
The engine is a french design, a couple of minor mistakes on the plans, but it is 10mm bore with 20mm stroke, double acting, with a sealed bearing crankshaft support, so should run nice and slow and turn about 3" to 3 1/2" steam prop.
I left 0.002" oversize on all flat surfaces to allow for surface grinding, this saves hours trying to get the port faces flat by lapping.
The reason I am making six of these is that they are fairly expensive to produce, with bearings and all stainless fixings and fittings, I will be selling four to recoup my costs.
I have just finished an E.T.Westbury designed 'Whippet', a very nice project that gives a lot of challenges. My next project is the 'Seal' by the same designer, a four cylinder side valve petrol engine.

John

[nick.gilling]

Hi John,

I've always liked the look of the Whippet engine and fancied giving it a go.

When I first got into the hobby when I was about 15, I bought the Woking Precision Models catalogue and made a big mistake. I bought the castings and drawings for the Sparey 0.8cc compression ignition engine! With hindsight I don't think this was the ideal model to start with! Needless to say I messed up every component I attempted and then gave up! Infact I'm still using the material left over from it, the other day I used a bit of brass for my oscillating engine that had "carb body" written on it in felt tip pen ... this is 12 years later!

I now think my skills are about good enough to attempt a flame licker or hot air engine so I want try one of those next then move onto an i.c. engine.

The main project I started was a 5" gauge sweet pea, I'm confident I can machine the components but the size of the task is daunting. I have no time now I am married and have a 1 year old son, so what I do do, I want to see results relatively quickly for! I must have been serious at the time with Sweet Pea though, I bought a brand new professional boiler for £500 thats sat under my bench, I'm told they're now circa £1000 though so that wasn't a bad investment!

Good look with the Seal, that's a lovely engine too, my ultimate goal one day, way out of my league at the moment though!

Nick

[Mcgyver]

the attached picture shows what stage I am up to, they all need surface grinding all over, but that comes after the tapping stage.

John, the work looks good, are they brass or bronze? reason i ask i've never considered surface grinding copper based alloys, wondering what the results are like and what wheel you use. I've a Norton manual grinder, probably the least used piece i have, but admit its nice having. gets used mostly for tooling that i get case hardened.

Always like the Seal, nice project - please take lots of pics and post them. I've wondered how difficult it would to carve the block and from solid and avoid the castings or maybe the cost of the castings isn't so bad? always seems ridiculous by the time they get to north america.

Nick, don't sweat not having a surface grinder, I've got one and would still finish and piece of brass off with progressive grades of emery and the surface plate

good luck with it and keep the pics coming

[bogstandard]

Hi Mcgyver,
The bits shown are all brass. I use a standard grey carburundum wheel for grinding all my non ferrous materials, but I do dress fairly often to keep the wheel unclogged. They all come up with a mirror finish, aluminium as well. For all my ferrous work I use White Aluminium Oxide (loose bond) that a friend gets me from his works, when they wear down to 5" they are normally thrown away, but they are ideal for my machine, they use them for grinding guide vanes for aero engines.
With reference to the Seal, I purchased everything to build it a couple of years back, even down to the spark plugs, but since then Woking Precision has gone belly up, and all the rights have been taken over by Hemingway Kits, but they are going to remaster everything before releasing it, so expect everything to double in price. Looking at the plans there is really nothing that couldn't be hogged out of the solid, in fact I think you would find it a lot easier than making from castings, the main reason you could start from a flat and square datum, on the castings there isn't a flat or square part on them.
Before I start the build I have to make a camshaft grinder, for the Whippet I made it in the lathe using jigs, but that only had two lobes (both with different profiles for inlet & exhaust), I made two just in case, but as it turned out they were both good, but the seal has eight lobes, again with two different profiles, so the cam grinder will be born. I am also considering whether it could be used for grinding the valves as well, as these are much smaller than the whippet valves, and getting a good finish on the stems is always a problem, but I suppose I could use my toolpost grinder if all else fails (I don't really like using it because it covers the lathe in what could be described as rough grinding paste, and no matter how much you cover things up you always get some 'leakage')

John

[Mcgyver]

in fact I think you would find it a lot easier than making from castings, the main reason you could start from a flat and square datum, on the castings there isn't a flat or square part on them.
John

John, thanks for the grinding, info i'll have to give it a go!

on the seal, pretty sure i have the old ME issues it first appeared in, the $@#%$ won't even get my dough for the plans. hehe

I hear you on the castings, I've made engines from castings and the uninitiated often look at them and suppose that making it from castings was 'easier' because the basic shape is provide, au contraire!

I've long been a casting snob....however recently have been rethinking it. Castings are ridiculously expensive, and while one hand they are judged to be a more authentic model based on materials, in fact from an appearance standpoint greater detail and better scaled look can be achieved via some, albeit very complex, fabrications. Poster Keith and the chaski site has made two corliss engines that imo look superior to kits such as the Coles model. The reason is that when scaled down, the details of the casting can end up to rounded off and blob like for a true scale representation. Keith's work is as good or greater than Kozo's excellent silver solder fabrications imo.

Notwithstanding some of the kits cost $1000. What hasn't emerged though (that i've seen) are plans of a major project, say a triple expansion or corliss engine, that are intended to take advantage of the detail possible with fabrication.

[bogstandard]

Hi Mcgyver,
I agree with you about castings, some are very 'dodgy' indeed. The main crankcase for my whippet had been over fettled by the foundry by 1/8" on the water jacket area, I got my friend who supplies my grinding wheels to take it into work where a coded welder built it up again, now you can't tell anything was ever wrong.
If you go to here - http://modelenginenews.org/index.html
and select November 2006 you will see a build of the Seal by some of the best model engineers around.
I think all the parts I bought for the seal came to about $600 but that included everything (gears, plans, piston rings etc) except raw materials, like cast iron for the cylinders (I use old sash window weights). But even though it was designed in the 1940's no-one has ever corrected the faults on the drawings. Maybe Hemingway will do it when they get around to it.
If ever you require any of the info for the seal I am sure I could copy it for you.

John

[Geof]

....The main crankcase for my whippet had been over fettled by the foundry....John

Hands up how many people know what "fettled" means. Apologies for the intrusion, I had not seen the word for many decades.

[greybeard]

Depends on how many potters are reading the thread.

Ditto re intrusion - I just like to know how the other half lives !

John

[bogstandard]

Its a common term in the area of the UK that I come from. But it is used even more in the so called black country, north west of Birmingham where there still exists a fair amount of small foundries. I also think it is used in the potteries of Staffordshire (very close to where I live), in the same sort of context, cleaning off excess casting material or rough edges.

[Geof]

...context, cleaning off excess casting material or rough edges.

I did my share of fettling during my apprenticeship in New Zealand.

[bogstandard]

Here are a few more bits I have knocked out for my project.
The crank webs are a slightly different shape to the drawings to aid production.
The steam control valve was enlarged from the original drawing to allow a third slot to be machined, this will be used for a physical stop for fully fwd/rev. Also the slot on the back was moved round by 45deg. This was one of the errors on the drawing.
All top covers and steam glands have been made, should be able to start on all the shaftwork and pistons this week.

[bogstandard]

Here is an update how the engines are going.
All have been surface ground, just waiting to get the viton o-rings so that I can start on the pistons and rods.
It looks like my cobbled together digital readout on my miller really does its job, every part is fully interchangeable throughout all engines.

[nick.gilling]

That is really nice work. Have the drawings got tolerances on them if the parts are interchangable or have you applied your own? Will you be fitting the pistons to cylinders or just machining a batch of them to a certain size?

Nick

[bogstandard]

Hi Nick,
I personally take no notice of drawing tolerances, but I like to work within 0.001" or 0.02mm.
The plans are free from here -
http://jpduval.free.fr/Plans_moteurs_vapeur_p1.htm
All the bores have been lapped to exactly the same (using delrin rod turned to the diameter I want and then use very fine carburundum grinding paste), so once I have a piston to size I can make all the others the same. I keep all my tolerances very tight by the use of a collet chuck or soft jaws on my lathe, if using the soft jaws I can transfer it directly to my rotary table on the miller and keep almost perfect registration, within 0.001" or 0.02mm which is close enough for anyone. For mating surfaces I tend to surface grind, this saves hours on lapping flat faces, just fit the two pieces together and it usually seals perfectly within a couple of minutes running.
The pistons will be having viton o-rings for piston rings (no rings on the drawing), I find that they last a full season of sailing before they need to be replaced.
Hope I haven't gone over the top answering your questions, but we are here to help each other to understand things better.

John

[nick.gilling]

Hi John,

thanks for that, it answers another question I though of, was there any kind of power take off. But it seems that it come out of the centre of one of the crank discs.

What I meant with the tolerances was, do the drawings give appropriate clearances etc. e.g If the Cylinder was 10.00 mm +0.01 -0.00 would the piston be 10.00 -0.01 -0.02 i.e. if the components were machined to the drawings there would be at least 0.01 mm clearance with a maximum clearance of 0.03 mm.

Thanks

Nick

[bogstandard]

Hi Nick,
I do a very basic test for piston fit, I tape over the side ports, put a bit of oil in the bore and slide a piston in, put my finger over the top of the cylinder and pull the piston out, if it doesn't come out with a loud 'pop', time to make a new piston, usually 0.001" gives a very good compression.
With reference to the power takeoff, it can't come off the centre shaft because the conrod would hit it, what happens is that you extend one of the big end rods and put another crank disc onto the extended rod, if you look at the picture on the plans website it explains what I mean, but I usually make a bearing carrier that sits on the engine bedplate rather than connecting straight onto the propshaft. These will be shown some time in the near future, when I have the bedplates made.

John

[nick.gilling]

Hi John,

thanks for the info again, of course the power take off can't come of the centre shaft! I wasn't thinking straight when i said that! I just glanced at the drawing and assumed that.

The engines are looking great, very professional, am sure you'll fetch good money for the ones you sell. They look like a relatively compact and powerful engine.

Nick

[bogstandard]

Thanks for the compliment, I am building them for members of our model club but any that are left over will be sold to recoup some of my losses, when you build as a hobby you can't sell your time.
With the engine being a long stroke it should run a lot slower than the commercial units available, but they should give a large increase in power, I have calculated from past experience that they will turn a 3" to 3 1/2" steam prop. in a 48" model.
I have just had some answers from another website that specialises in model paddle boats and I should be able to gear one down and lay it on its back to make a horizontal engine.
Made all the pistons today and as expected they were all within 0.001" of each other, just one that was slightly tight, I guess I didn't lap the bore as much as the others. That is the advantage of multiple production, if you have it set to do one you may as well make a dozen, it doesn't take much longer because most of the work is in the setup and jigging.

John